JP3172422B2 - Heating resistor type air flow measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating resistor type air flow measuring device used for controlling an internal combustion engine for an automobile.

[0002]

2. Description of the Related Art As disclosed in Japanese Patent Application Laid-Open No. Sho 62-812, a conventional technique uses two heating resistors to determine the direction of air flow, and detects only one of detection signals. To generate an output signal. And 2
A method is employed in which a noise component generated by mutual interference between two heating resistors and included in an output signal is reduced by attenuating an AC component of the output signal.

[0003]

However, in the above-mentioned prior art, since the output signal is attenuated, the detection delay at the time of air flow reversal becomes large, and there is a problem in measurement accuracy. Accordingly, it is an object of the present invention to provide a heating resistor type air flow measuring device capable of reducing noise while ensuring measurement accuracy.

[0004]

According to the present invention, a heating resistor type air flow measuring device which achieves the above object is provided with a heating current required for heating a forward heating resistor disposed in an air flow passage to a predetermined temperature. In the heating resistor type air flow measuring device for detecting a detection signal and detecting a reverse detection signal from a heating current necessary for heating the reverse heating resistor disposed in the air flow passage to a predetermined temperature, Cancellation for adding an AC component of the backward detection signal to a direction detection signal and adding an AC component of the forward direction detection signal to the backward direction detection signal to cancel a differential mode noise component included in each of the detection signals. Means.

Another feature of the present invention is that a heating current required to heat a forward heating resistor and a reverse heating resistor disposed in an air flow path to a predetermined temperature, respectively, is a forward detection signal and a forward detection signal. In a heating resistor type air flow measuring device, comprising a pair of air flow detecting units for detecting as a reverse direction detecting signal, and outputting a flow signal including a directional component of the air flow in the air flow path using the respective detecting signals. Adding the AC component of the reverse direction detection signal to the forward direction detection signal, and adding the AC component of the forward direction detection signal to the reverse direction detection signal, and generated by thermal interference between the heating resistors. Canceling means for canceling a differential mode noise component included in the forward detection signal and the backward detection signal and outputting a forward cancellation output signal and a backward cancellation output signal; Instead of reverse direction detection signal by using the forward offset output signal and said reverse offset output signal in outputting the flow rate signal.

Further, another feature of the present invention is that a heating current required to heat a forward heating resistor and a reverse heating resistor disposed in an air flow path to a predetermined temperature, respectively, is a forward detection signal and a forward detection signal. A pair of air flow rate detection units for detecting as a reverse direction detection signal, signal comparison means for determining the direction of the air flow in the air flow path from a magnitude comparison between the forward direction detection signal and the reverse direction detection signal, A signal selection unit that selects the forward detection signal or the backward detection signal based on the determination, and switches and inputs the forward detection signal or the backward detection signal selected by the signal selection unit; An output signal that is higher than a reference voltage in proportion to the added signal by adding an AC component of the backward detection signal to the forward detection signal, or in proportion to the input backward detection signal. The output signal is smaller than the reference voltage,
And a differential amplifier circuit for switching and outputting the output signal, and using the output signal from the differential amplifier circuit to output a flow signal including a directional component of the air flow.

Another feature of the present invention is that a heating current necessary for heating a forward heating resistor and a reverse heating resistor disposed in an air flow path to a predetermined temperature is provided in a forward direction. A pair of air flow rate detecting sections for detecting as a detection signal and a reverse direction detection signal, and signal comparing means for determining a direction of an air flow in the air flow path from a magnitude comparison between the forward direction detection signal and the reverse direction detection signal Signal selection means for selecting the forward detection signal or the backward detection signal based on the determination; and switching and inputting the forward detection signal or the backward detection signal selected by the signal selection means. An output signal that is higher than a reference voltage in proportion to the input forward detection signal, or an AC component of the forward detection signal is added to the input backward detection signal by inverting the phase thereof and added. An output signal that becomes smaller than the reference voltage in proportion to the calculated signal, and a differential amplifier circuit that switches and outputs the output signal, and includes the direction component of the airflow using the output signal from the differential amplifier circuit. It is in a heating resistor type air flow measuring device that outputs a flow signal.

According to the present invention, there is provided a heating resistor type air flow measuring device capable of reducing noise while ensuring measurement accuracy.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing a heating resistor type air flow measuring device according to one embodiment of the present invention. The heating resistor type air flow measuring device according to the present embodiment includes an air flow detecting unit 8, 18, characteristic adjusting circuits 21, 22, and a canceling unit 5.
0, switching means 51, and a differential amplifier 31.

In FIG. 1, the air flow detecting units 8 and 18 are:
A Wheatstone bridge circuit comprising heating resistors 1 and 11 and air temperature detecting resistors 2 and 12 and resistors 3, 4, 5, 13, 14 and 15 installed in the air passage; and heating resistors 1 and 11 Constant temperature control consisting of operational amplifiers 6 and 16 and transistors 7 and 17 that supply current to the Wheatstone bridge circuit so that the resistance of the air temperature detection resistors 2 and 12 is corrected and set to a constant value. And a circuit. The pair of air flow detectors 8 and 18 detect the heating current of the heating resistors 1 and 11 by the current detection resistors 3 and 13 and output a forward detection signal V2F and a reverse detection signal V2R, respectively. . The heating resistors 1 and 11 are arranged so that the detection sensitivity of the heating resistor in one of the forward direction and the reverse direction of the airflow is increased.

In other words, one air flow detecting unit 8 for detecting a heating current required to heat the forward heating resistor 1 arranged in the air flow passage to a predetermined temperature as a forward detection signal V2F; Reverse heating resistor 11 arranged in air flow path
And a second air flow detecting unit 18 for detecting a heating current necessary to heat the air to a predetermined temperature as a reverse direction detection signal V2R.

The forward direction detection signal V2F and the backward direction detection signal V2R are characteristic-adjusted by characteristic adjustment circuits 21 and 22, and are output as two forward / reverse adjustment signals VOF and VOR. afterwards,
The adjustment signals VOF and VOR are compared by the comparator 29, and the larger signal is selected by the switch circuit 30. That is, the direction of the air flow is determined by the comparator 29 as signal comparing means from the magnitude comparison between the adjustment signal VOF as the forward direction detection signal and the adjustment signal VOR as the reverse direction detection signal. And a switch circuit as signal selection means based on the determination.
30 selects the forward cancellation output signal VOUTF or the reverse cancellation output signal VOUTR. Eventually,
The differential amplifier 31 inverts the voltage at the time of detection of the backflow, amplifies the forward cancellation output signal VOUTF or the backward cancellation output signal VOUTR as the output signal VOUT, and “a flow signal VG including the direction component of the airflow”. Is output.

When the heating resistor 1 for detecting the forward direction and the heating resistor 11 for detecting the reverse direction are thermally coupled to each other, the changes in the heating currents are complementary. The two adjustment signals VOF and VOR include the differential mode noises whose phases are inverted from each other. If one of the adjustment signals VOF and VOR is selected and used as the output signal VOUT of the flow meter while the differential mode noise component is still included as in the prior art, the output signal VOUT and the flow rate The signal VG will also contain noise. In order to remove this differential mode noise component, there is a method of attenuating (for example, averaging) the AC component of the two forward and reverse adjustment signals, but the attenuation causes a large detection delay at the time of air flow reversal. Become.

Accordingly, the present invention is to eliminate noise without increasing the detection delay at the time of air flow reversal.
That is, in the embodiment of FIG. 1, the AC component of the reverse signal is converted from the forward adjustment signal VOF after the characteristic adjustment to the forward signal by using one of the canceling means 50a including the resistors 23 and 24 and the capacitor 25. The added forward canceling output signal VOUTF is obtained, and the AC component of the forward signal is converted from the backward adjusting signal VOR to the backward signal using the other canceling means 50b including the resistors 26 and 27 and the capacitor 28. Is added to obtain a reverse cancellation output signal VOUTR. In this embodiment, the canceling means 50 includes one canceling means 50a and the other canceling means 50b, but does not necessarily require both canceling means as described later.

In a switching means 51 comprising a comparator 29 as a signal comparing means and a switch circuit 30 as a signal selecting means, the comparator 29 supplies a forward and backward two adjustment signals after characteristic adjustment representing the forward and reverse of the air flow. VOF and VOR are input to control the switching operation of the switch circuit 30. That is, the comparator 29 switches the switch circuit 30 by detecting the forward and reverse directions of the air flow, and the output signal VOUT (VOUTF or VOUTR) from which the noise has been canceled is switched and output. Note that, instead of the adjustment signals VOF and VOR, a forward detection signal V2F and a backward detection signal V2R may be used. As described above, the differential mode noise can be reduced, that is, canceled out, without increasing the detection delay at the time of air flow reversal.

Summarizing the above briefly, the present invention for solving the problem is to provide the forward detection signal with the AC component of the backward detection signal and the reverse detection signal with the AC component of the forward detection signal. In other words, a circuit is configured to add the AC components of the respective detection signals opposite to the forward detection signal V2F or the backward detection signal V2R to cancel the differential mode noise component included in the two detection signals. It was done. In other words, when a backflow detection type flow meter is configured using two heating resistor type air flow rate detection units, 2
The closer the two heating resistors are, the more they thermally interfere with each other.If the heating current of one heating resistor increases, the excess heat is transmitted to the other heating resistor, and the effect of the excess heat is reduced. Since the air flow detecting unit on the side of the heating resistor that has received the heating current reduces the heating current, two heating current detection signals (detection signals V2F and V2
R) includes noise components whose phases are inverted from each other. Therefore, the AC component of the two heating current detection signals is added to each other to remove the noise component. In the case of the first embodiment, the offset means
It is also possible that 50 includes signal comparing means for determining the direction of the airflow and signal selecting means for selecting a forward or reverse cancellation output signal based on the determination.

FIG. 2 is a view showing a heating resistor type air flow measuring device according to another embodiment of the present invention. A second embodiment will be described. In the embodiment of FIG. 2, in addition to a circuit consisting of a resistor 24 and a capacitor 25 for preliminarily adding only the AC component of the reverse adjustment signal VOR, an adjustment signal selected by a switch circuit 30 that performs a switching operation according to a comparator 29 V
OF and VOR are determined by using a reference voltage VCM so that the output voltage when the flow rate is 0 (zero) becomes VCM, and a flow signal V representing forward and reverse directions.
A differential amplifier circuit 55 is configured by providing a circuit comprising an operational amplifier 36 for outputting G, resistors 23, 34, 35, 37 and a reference voltage VCM. In other words, a circuit configuration is used in which only the AC component of the adjustment signal VOR in the reverse direction is added to the adjustment signal VOF so as to cancel it using the AC signal extraction means including the resistor 24 and the capacitor 25. In the case of the present embodiment, it can be said that the canceling means, the switching means, and the differential amplifier are integrated.

According to the embodiment of FIG. 2, the adjustment signal VOF in the forward direction has the effect of reducing the differential mode noise,
For the adjustment signal VOR in the reverse direction, a resistor 24 and a capacitor
25, the AC component in the frequency range defined by the circuit is cut off and acts as a noise filter, so that the heating resistor for forward detection during forward flow measurement is used.
When 1 and the heating resistor 11 for reverse direction detection are thermally coupled, there is an effect that the differential mode noise is gradually reduced. Furthermore, by setting the output voltage when the flow rate is 0 (zero) to VCM, it becomes possible to operate with a single power supply system for automobiles,
There is an advantage of dual use of power supply.

On the other hand, in the case of the present embodiment, before the input of the forward and backward two adjustment signals after the characteristic adjustment to the direction discriminating comparator 29, the "response" originally provided by the heating resistor type air flow measuring device is provided. The "delay" is corrected by the equalizers 32 and 33 to improve the detection delay of backflow occurrence. The equalizer 32,
33 can be applied to other embodiments other than the present embodiment, or can be omitted.

FIG. 3 is a view showing a heating resistor type air flow measuring device according to a third embodiment of the present invention. A third embodiment will be described with reference to FIG. In the embodiment of FIG. 3, the adjustment signals VOF and VOR selected by the switch circuit 30 switched by the comparator 29 are used by using the reference voltage VCM so that the output voltage at the time of the flow rate 0 (zero) becomes VCM. As a circuit that outputs a flow signal VG representing both forward and reverse directions,
Resistor 27, capacitor 28, operational amplifier 36, and resistors 34, 35, 3
A differential amplifier circuit 56 comprising 7, 38 and a reference voltage VCM is configured. In the case of the present embodiment, the AC component of the forward adjustment signal VOF is inverted by the differential amplifier circuit 56 and added by a circuit including the resistor 27 and the capacitor 28. Also in the case of this embodiment, it can be said that the canceling means, the switching means, and the differential amplifier are integrally configured.

In the embodiment of FIG. 3, the forward adjustment signal VOF
In this case, an AC component in a frequency range determined by a circuit composed of the resistor 24 and the capacitor 25 is cut off to act as a noise filter, and the effect that the differential mode noise due to the thermal coupling between the heating resistors is gradually reduced. is there. The adjustment signal VOR in the reverse direction has the effect of reducing only the differential mode noise of the heating resistor.

FIG. 4 is a view showing a heating resistor type air flow measuring device according to a fourth embodiment of the present invention. A fourth embodiment will be described with reference to FIG. In FIG. 4, a flow meter 40 as a heating resistor type air flow measuring device includes air flow detecting units 8 and 18 and characteristic adjusting circuits 21 and 22.
Then, the flow meter 40 transmits two forward and reverse adjustment signals VOF and VOR after the characteristic adjustment to the fuel injection amount control device 41 for the internal combustion engine. In the case of the fourth embodiment, the two forward and reverse adjustment signals VOF and VOR can be said to be a forward direction detection signal and a backward direction detection signal detected by the flow meter 40 in a broad sense.

A signal comparing means 42, AC signal extracting means 43 and 44, signal adding means 45 and 46, and a signal selecting means 47 are provided inside a fuel injection amount control device 41 of the fuel injection amount control system of the internal combustion engine. The fuel injection amount control device 41 creates an output signal VOUT including a direction component, and sends the output signal VOUT to the signal processing means 48 as information necessary for controlling the fuel injection amount of the internal combustion engine. The signal processing means 48 processes the output signal VOUT into a flow rate signal VG.

Accordingly, the canceling means 50, that is, one of the canceling means 50a is constituted by the AC signal extracting means 44 and the signal adding means 45, and the other canceling means 50b is constituted by the AC signal extracting means 43 and the signal adding means 46. The switching means 51 includes a signal comparing means 42 and a signal selecting means 47. That is, a switching means for selecting an input signal as two adjustment signals, and a canceling means for adding each other's AC component to each input signal and outputting the result are a fuel injection amount control device 41 as a semiconductor electronic circuit.
2 shows an embodiment in the case of being configured inside.

According to the embodiment of FIG. 4, the signal comparing means 42,
The AC signal extracting means 43 and 44, the signal adding means 45 and 46, the signal selecting means 47, and the like can be integrated into the fuel injection amount control device 41, and can also serve as the numerical calculation processing function of the fuel injection amount control device 41. Therefore, there is an effect that the system cost is reduced.

FIG. 5 is a diagram showing a heating resistor type air flow measuring device according to a fifth embodiment of the present invention. The difference from the embodiment of FIG. 4 is that the heating resistor type air flow measuring device is not integrated into the fuel injection amount control device 41. In the figure, the canceling means of FIG.
Reference numeral 50 is the same as that constituted by the AC signal extracting means 43, the signal adding means 46, the AC signal extracting means 44, and the signal adding means 45 in the embodiment of FIG. The switching means 51 in FIG. 5 is the same as that comprising the signal comparing means 42 and the signal selecting means 47 of the embodiment in FIG.

FIG. 5 also shows a configuration in which the heating resistor type air flow measuring device of the embodiment shown in FIG. 1 is replaced with a block configuration. That is, the AC signal extracting means 43 in FIG.
Corresponds to an AC signal extracting means including the resistor 27 and the capacitor 28 in FIG. AC signal extraction means 44
Corresponds to the AC signal extracting means including the resistor 24 and the capacitor 25. The signal adding unit 45 corresponds to a signal adding unit including the resistor 23 and the connection unit. The signal adding means 46 corresponds to a signal adding means including the resistor 26 and the connection portion. 1. The signal comparing means 42 in FIG. 5 corresponds to the comparator 29 in FIG. 1, and the signal selecting means 47 corresponds to the switch circuit 30 in FIG.

FIG. 6 is a view showing a heating resistor type air flow measuring device according to a sixth embodiment of the present invention. In the embodiments of FIGS. 1 to 5, the heating resistor type air flow measuring device and the flow meter 40 have been described as including the characteristic adjustment circuits 21 and 22 and the differential amplifier 31. However, the heating resistor type air flow measuring device can be interpreted in a narrow sense as being the air flow detecting units 8 and 18 which integrally include the canceling means 50.

That is, the heating resistor type air flow measuring device in this case detects the forward detection signal V2F from the heating current required to heat the forward heating resistor disposed in the air flow passage to a predetermined temperature. And a means for detecting a reverse detection signal V2R from a heating current required to heat the reverse heating element disposed in the air flow path to a predetermined temperature. The AC component of the backward detection signal is added to the direction detection signal, and the AC component of the forward detection signal is added to the backward detection signal, so that the differential mode noise component included in the forward detection signal and the backward detection signal is reduced. And offsetting means for offsetting.

In this case, the forward cancellation output signal VOUTF and the reverse cancellation output signal VOUT output from the cancellation means are provided.
Using OUTR, the flow signal VG will be determined.
In a heating resistor type air flow measuring device as a flow meter including an air flow detecting unit and a characteristic adjusting circuit, a canceling means 50 is provided between the air flow detecting units 8 and 18 and the characteristic adjusting circuits 21 and 22. It is also possible.

[0031]

According to the present invention, an output based on a differential component between a forward detection signal and a reverse detection signal generated by mutual interference between two heating resistors of a heating resistor type air flow measuring device of a backflow detection type. The noise of the signal and the flow signal can be reduced without increasing the detection delay at the time of air flow reversal.

[Brief description of the drawings]

FIG. 1 is a view showing a heating resistor type air flow measuring device according to an embodiment of the present invention.

FIG. 2 is a view showing a heating resistor type air flow measuring device according to another embodiment of the present invention.

FIG. 3 is a view showing a heating resistor type air flow measuring device according to a third embodiment of the present invention.

FIG. 4 is a view showing a heating resistor type air flow measuring device according to a fourth embodiment of the present invention.

FIG. 5 is a view showing a heating resistor type air flow measuring device according to a fifth embodiment of the present invention.

FIG. 6 is a view showing a heating resistor type air flow measuring device according to a sixth embodiment of the present invention.

[Explanation of symbols]

1,11: Heating resistor, 2,12: Air temperature detecting resistor, 3,4,5,13,14,15,23,24,26,27,34,35,37,38 ... Resistance,
6, 16, 36 ... operational amplifiers, 7, 17 ... transistors, 8, 18 ... air flow rate detection units, 21, 22 ... characteristic adjustment circuits, 25, 28 ... capacitors, 29 ... comparators, 30 ...
Switch circuit, 31: Differential amplifier, 32, 33: Equalizer, 40: Flow meter, 41: Fuel injection amount control device, 42
... Signal comparing means, 43, 44 ... AC signal extracting means, 4
5, 46 ... signal adding means, 47 ... signal selecting means, 48 ...
Signal processing means, 50, 50a, 50b: cancellation means, 51: switching means, 55, 56: differential amplifier circuit, V2F: forward detection signal, V2R: reverse detection signal, VOF: forward adjustment signal, V
OR: reverse adjustment signal, VB: battery voltage, VOUT: output signal, VOUTF: forward offset output signal, VOUTR: reverse offset output signal, VCM, VREF: reference voltage, VG: flow rate signal.

Continuing from the front page (72) Inventor Chihiro Kobayashi 2520 Takahiro, Hitachinaka-shi, Ibaraki Prefecture Hitachi, Ltd.Automotive Equipment Division (72) Inventor Izumi Watanabe 2477 Takaba, Hitachinaka-shi, Ibaraki Hitachi Car Engineering Co., Ltd. 56) References JP-A-7-333027 (JP, A) JP-A-62-73124 (JP, A) JP-A-1-185416 (JP, A) JP-A-7-5007 (JP, A) ) Surveyed field (Int.Cl. ⁷ , DB name) G01F 1/68-1/699

Claims (7)

(57) [Claims] 1. A forward detection signal is detected from a heating current required to heat a forward heating resistor disposed in an air flow passage to a predetermined temperature, and a reverse heating signal disposed in the air flow passage is detected. In a heating resistor type air flow measurement device for detecting a reverse direction detection signal from a heating current required to heat a resistor to a predetermined temperature, an AC component of the reverse direction detection signal is added to the forward direction detection signal, and A heating resistor type air flow measuring device, comprising: a canceling means for adding an AC component of the forward detection signal to a direction detection signal to cancel a differential mode noise component included in each of the detection signals. 2. A pair of heating currents required to heat a forward heating resistor and a reverse heating resistor disposed in an air flow passage to a predetermined temperature, respectively, as a forward detection signal and a reverse detection signal. A heating resistor type air flow measurement device that includes an air flow detection unit and outputs a flow signal including a directional component of the air flow in the air flow path using each of the detection signals. An AC component of a reverse direction detection signal is added, and an AC component of the forward direction detection signal is added to the reverse direction detection signal, and the forward direction detection signal and the reverse direction generated by thermal interference between the heating resistors. A canceling means for canceling the differential mode noise component included in the detection signal and outputting a forward cancellation output signal and a backward cancellation output signal is provided, instead of the forward detection signal and the backward detection signal. Heating resistor type air flow rate measuring apparatus characterized by outputting the flow rate signal with the direction canceling the output signal and said reverse offset output signal. 3. A signal comparing means according to claim 1, wherein said canceling means determines a direction of said air flow from a magnitude comparison between said forward direction detecting signal and said backward direction detecting signal. Signal selection means for selecting the forward cancellation output signal or the backward cancellation output signal based on the determination, wherein the forward cancellation output signal or the backward cancellation switched according to the direction of the airflow. A heating resistor type air flow measuring device, wherein the flow signal is output using an output signal. 4. A semiconductor electronic circuit according to claim 3, wherein said canceling means, said signal comparing means and said signal selecting means control a fuel injection amount of an internal combustion engine using said flow rate signal. A heating resistor type air flow measuring device characterized in that it is included in the apparatus. 5. A pair of sensors for detecting a heating current required to heat a forward heating resistor and a reverse heating resistor disposed in an air flow passage to a predetermined temperature, respectively, as a forward detection signal and a reverse detection signal. An air flow rate detection unit, signal comparison means for determining the direction of the air flow in the air flow path from a magnitude comparison between the forward direction detection signal and the backward direction detection signal, and the forward direction detection based on the determination Signal selection means for selecting a signal or the backward detection signal; and switching and inputting the forward detection signal or the backward detection signal selected by the signal selection means, and applying the inverse to the input forward detection signal. An output signal that adds an AC component of the direction detection signal and becomes higher than a reference voltage in proportion to the added signal, or an output signal that becomes smaller than the reference voltage in proportion to the input reverse direction detection signal. And a differential amplifying circuit for switching and outputting, and using the output signal from the differential amplifying circuit, outputting a flow signal including a directional component of the air flow, a heating resistor type air flow. measuring device. 6. A pair of sensors for detecting a heating current required to heat a forward heating resistor and a reverse heating resistor disposed in an air flow passage to a predetermined temperature, respectively, as a forward detection signal and a reverse detection signal. An air flow rate detection unit, signal comparison means for determining the direction of the air flow in the air flow path from a magnitude comparison between the forward direction detection signal and the backward direction detection signal, and the forward direction detection based on the determination Signal selection means for selecting a signal or the backward direction detection signal; and switching and inputting the forward direction detection signal or the backward direction detection signal selected by the signal selection means, in proportion to the inputted forward direction detection signal. The output signal becomes higher than the reference voltage, or the AC component of the forward detection signal is added to the input backward detection signal by inverting the phase, and is smaller than the reference voltage in proportion to the added signal. A differential amplifier circuit for switching and outputting the output signal, and using the output signal from the differential amplifier circuit to output a flow signal including a directional component of the airflow. Resistor type air flow measurement device. 7. An internal combustion engine, wherein a fuel injection amount of the internal combustion engine is controlled using a flow signal obtained by the heating resistor type air flow measuring device according to any one of claims 1 to 6. Fuel injection amount control system.