JP2690964B2 - Thermal air flow meter - Google Patents
Thermal air flow meterInfo
- Publication number
- JP2690964B2 JP2690964B2 JP63228706A JP22870688A JP2690964B2 JP 2690964 B2 JP2690964 B2 JP 2690964B2 JP 63228706 A JP63228706 A JP 63228706A JP 22870688 A JP22870688 A JP 22870688A JP 2690964 B2 JP2690964 B2 JP 2690964B2
- Authority
- JP
- Japan
- Prior art keywords
- air flow
- flow meter
- circuit
- temperature
- voltage
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Description
【発明の詳細な説明】 〔産業上の利用分野〕 本発明は熱線式空気流量計に係り、特に自動車のエン
ジン制御に使用する吸入空気の検出を行なう熱線式空気
流量計に関する。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-wire air flow meter, and more particularly to a hot-wire air flow meter for detecting intake air used for engine control of an automobile.
自動車エンジン制御のための吸入空気量検出に熱線式
空気流量計を使用することは、特開昭62-153712等があ
り、エンジン制御に直接必要な質量空気流量が検出でき
ること、空気流量変化に対する応答が早いこと、等が利
点である。Japanese Patent Laid-Open No. 62-153712 discloses the use of a hot-wire air flow meter for detecting the amount of intake air for controlling an automobile engine. The advantage is that it is fast.
しかし、上記従来技術は、熱線の持つ温度変化による
特性変動に対して配慮がされておらず、低温（−40℃）
から高温（100℃）まで広い範囲で使用されるエンジン
制御では、その制御精度が低下する問題があつた。However, the above-mentioned conventional technology does not consider the characteristic fluctuation due to the temperature change of the heat ray, and the low temperature (-40 ° C)
In engine control used in a wide range from high to high temperature (100 ° C), there was a problem that the control accuracy decreased.
本発明は、周囲温度が変化しても、正確な流量を検出
できる熱線式空気流量計を提供することにある。The present invention is to provide a hot-wire air flow meter capable of detecting an accurate flow rate even if the ambient temperature changes.
上記目的は、熱線で検出した流量信号を処理する回路
に温度補償機能を付加することにより達成される。The above object is achieved by adding a temperature compensation function to a circuit that processes a flow rate signal detected by a heat ray.
熱線式空気流量計を用いた自動車エンジン制御システ
ムは、マイクロコンピユータが制御を司るため、アナロ
グ信号は、デイジタル信号、あるいは周波数に変換する
必要がある。そのため、本発明の空気流量計は、基本的
には熱線の温度を制御し熱線の出力信号を発生する熱線
制御回路と、その増巾回路および、アナログ信号を周波
数信号に変換するための周波数変換回路から構成され
る。Since an automobile engine control system using a hot wire air flow meter is controlled by a microcomputer, it is necessary to convert an analog signal into a digital signal or a frequency. Therefore, the air flow meter of the present invention is basically a hot wire control circuit that controls the temperature of the hot wire and generates an output signal of the hot wire, its amplification circuit, and a frequency converter for converting an analog signal to a frequency signal. Composed of circuits.
一方、熱線の温度変化は、空気流量＝０におけるオフ
セツトと、単位空気流量変化に対する熱線出力の変化分
を示すゲインがあり、各々温度補償が必要である。On the other hand, the temperature change of the heat ray has an offset at the air flow rate = 0 and a gain indicating the change amount of the heat ray output with respect to the change of the unit air flow rate, and temperature compensation is required for each.
本発明は、オフセツトの温度補償機能を増巾回路に、
ゲインの温度補償機能を周波数変換回路に設けたので周
囲温度の影響が非常に少ない。The present invention has an offset temperature compensation function in a widening circuit,
Since the temperature compensation function for gain is provided in the frequency conversion circuit, the influence of ambient temperature is very small.
本発明の実施例を図によつて説明する。 An embodiment of the present invention will be described with reference to the drawings.
第１図は本発明の基本構成図、第２図は熱線、および
熱線制御回路２、増巾回路３の詳細図、第３図は周波数
変換回路４の詳細図である。31は、オフセツトの温度補
償回路、41はゲインの温度補償回路である。第4,第５図
は動作図である。FIG. 1 is a basic configuration diagram of the present invention, FIG. 2 is a detailed view of a hot wire, a hot wire control circuit 2 and a widening circuit 3, and FIG. 3 is a detailed view of a frequency conversion circuit 4. Reference numeral 31 is an offset temperature compensation circuit, and 41 is a gain temperature compensation circuit. 4 and 5 are operation diagrams.
次に動作を説明する。第1,第２図において、熱線１を
流れる電流Ihは、Kingの式より（１）式で示される。Next, the operation will be described. In FIGS. 1 and 2, the current I h flowing through the heating wire 1 is represented by the equation (1) according to King's equation.
一方、差動増巾器A1,抵抗器R1,R7,R8空気温度を検出
する補償線Rc、トランジスタT1により（１）式の（Th−
Ta）／RHは常にほぼ一定値に制御される。従つて、
（１）式より空気Ihは（２）となり、この電流Ihは抵
抗、R1で検出され、熱線制御回路の出力信号V2となる。 On the other hand, the differential amplifier A1, resistors R1, R7, R8 compensating line Rc for detecting the air temperature, and transistor T1 are used to (T h −
T a ) / RH is always controlled to a substantially constant value. Therefore,
(1) Air I h is (2) and from the equation, the current Ih is resistance, is detected by R1, the output signal V 2 of the heat ray control circuit.
このV2を増巾回路３の、差動増巾器A2で、後段の周波
数変換回路４の特性に合わせる様増巾する。V2,V0,F0の
伝達関数は（３），（４）式で示される。 This V 2 is widened by the differential widening unit A2 of the widening circuit 3 so as to match the characteristics of the frequency conversion circuit 4 in the subsequent stage. The transfer functions of V 2 , V 0 and F 0 are represented by the equations (3) and (4).
この動作を図で示すと、第５図の周囲温度25℃時のグ
ラフとなる。 This operation is shown in the graph of FIG. 5 when the ambient temperature is 25 ° C.
ここで周囲温度が変化し、例えば、80℃に上昇したと
すると、（１）式に示した、熱線の特性を示す定数A,B
が変化し、空気流量Ｑに対する熱線制御回路２の出力V2
は、第５図（ｂ）の点線の様になる。その結果、温度補
償がない状態では出力信号F0は第５図（ａ），（１）の
特性となる。If the ambient temperature changes here and rises to, for example, 80 ° C., the constants A and B indicating the characteristics of the heat wire shown in the equation (1) are shown.
Changes and the output V 2 of the heat ray control circuit 2 with respect to the air flow rate Q
Becomes like the dotted line in FIG. 5 (b). As a result, the output signal F 0 has the characteristics shown in FIGS. 5A and 5A when there is no temperature compensation.
従つて、熱線１が出力特性を決定している。オフセツ
トＡ、ゲインＢの温度変化に対する温度補償が必要であ
る。Therefore, the heating wire 1 determines the output characteristic. Temperature compensation for the temperature change of the offset A and the gain B is necessary.
オフセツト温度補償回路31、ゲイン温度補償回路41
は、それぞれ抵抗R17とツエナーダイオードDZ1,抵抗R11
1,ツエナーダイオードDZ2で構成されている。ツエナー
ダイオードのツエナー電圧（VC1,VC2に相当する）の温
度変化は、第４図に示す様に、ツエナー電流により、正
・負両方向に変化する。即ち、Ａの温度変化に対応し
て、抵抗R17を調整し、ツエナーダイオードDZ1のツエナ
ー電流を最適値にすることにより、（３）式のｅが温度
により変化するので、第５図（ｃ）の様に、V2−V0特性
が変化する。その結果、第５図（ａ）の（１）は、
（２）となり、オフセツトが温度補償される。同様にゲ
インは、ツエナーダイオードDZ2の電流を最適に設定す
ることにより、（４）式のΔVrに温度変化が加わり、V0
−F0特性は、第５図（ｄ）となる。その結果、第５図
（ａ），（２）の特性は（３）となり、オフセツトゲイ
ン共に温度補償され、室温の特性と一致する。Offset temperature compensation circuit 31, gain temperature compensation circuit 41
Are resistor R17, Zener diode DZ1, and resistor R11, respectively.
It is composed of 1, Zener diode DZ2. The temperature change of the zener voltage (corresponding to V C1 and V C2 ) of the zener diode changes in both positive and negative directions by the zener current as shown in FIG. That is, by adjusting the resistor R17 in response to the temperature change of A and setting the zener current of the zener diode DZ1 to the optimum value, e in the equation (3) changes depending on the temperature, so that FIG. The V 2 −V 0 characteristic changes like. As a result, (1) in FIG.
(2) The offset is temperature-compensated. Similarly, for the gain, by setting the current of the Zener diode DZ2 to the optimum value, the temperature change is added to ΔVr in the equation (4), and V 0
The −F 0 characteristic is shown in FIG. As a result, the characteristics of FIGS. 5 (a) and 5 (2) become (3), both offset gains are temperature-compensated, and match the characteristics at room temperature.
第６図，第７図は、オフセツト、ゲインの温度補償回
路の別な実施例を示したものである。第６図はサーミス
タ、第７図はダイオードの順方向電圧の温度変化を利用
したものである。（ａ）の場合は温度保数が負となり
（ｂ）の場合は正となる。いずれも前述と同じ効果があ
る。FIG. 6 and FIG. 7 show another embodiment of the temperature compensation circuit for offset and gain. FIG. 6 shows the thermistor, and FIG. 7 utilizes the temperature change of the forward voltage of the diode. In the case of (a), the temperature retention is negative, and in the case of (b), it is positive. Both have the same effect as described above.
以上の様にすることにより、周囲温度変化の影響の少
ない、高精度な熱線式空気流量計を提供できる効果があ
る。By the above, there is an effect that it is possible to provide a highly accurate hot-wire type air flow meter that is less affected by changes in ambient temperature.
第１図は本発明の基本構成図、第２図，第３図は詳細な
回路図、第４図，第５図は動作図、第６図，第７図は温
度補償回路の別な実施例を示す図である。 １……熱線、２……熱線制御回路、３……増巾回路、31
……オフセツト温度補償回路、４……周波数変換回路、
41……ゲイン温度補償回路。FIG. 1 is a basic configuration diagram of the present invention, FIGS. 2 and 3 are detailed circuit diagrams, FIGS. 4 and 5 are operation diagrams, and FIGS. 6 and 7 are other embodiments of temperature compensation circuits. It is a figure which shows an example. 1 ... Heat ray, 2 ... Heat ray control circuit, 3 ... Widening circuit, 31
...... Offset temperature compensation circuit, 4 ... Frequency conversion circuit,
41 …… Gain temperature compensation circuit.
Claims (4)
された電流を電圧信号として出力する制御回路と、前記
電圧信号を増幅する増幅回路と、出力を周波数信号に変
換する周波数変換回路とからなる熱式空気流量計におい
て、前記増幅回路のオフセットおよび前記周波数変換回
路のゲインにそれぞれ温度変化を与えることを特徴とす
る熱式空気流量計。1. A control circuit for supplying a current to a heating resistor and outputting the supplied current as a voltage signal, an amplifier circuit for amplifying the voltage signal, and a frequency conversion circuit for converting the output into a frequency signal. In the thermal air flow meter, the thermal air flow meter is characterized in that the offset of the amplification circuit and the gain of the frequency conversion circuit are respectively changed in temperature.
ットの温度変化は、演算増幅器の入力電圧にツェナーダ
イオードのツェナー電圧の温度変化を利用して与えるこ
とを特徴とする熱式空気流量計。2. The thermal type air flow meter according to claim 1, wherein the temperature change of the offset of the amplifier circuit is given to the input voltage of the operational amplifier by utilizing the temperature change of the Zener voltage of the Zener diode.
は、入力電圧を積分し、その出力を比較器により比較
し、積分傾斜を反転する様に帰還する回路で構成され、
前記比較器の基準電圧に温度変化するようにしたことを
特徴とする熱式空気流量計。3. The frequency conversion circuit according to claim 1, wherein the frequency conversion circuit is configured by a circuit that integrates an input voltage, compares the output with a comparator, and feeds back so as to invert the integration slope.
A thermal type air flow meter characterized in that the temperature is changed to a reference voltage of the comparator.
化はツェナーダイオードのツェナー電圧の温度変化から
得ることを特徴とする熱式空気流量計。4. The thermal air flow meter according to claim 3, wherein the temperature change of the reference voltage is obtained from the temperature change of the Zener voltage of the Zener diode.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63228706A JP2690964B2 (en) | 1988-09-14 | 1988-09-14 | Thermal air flow meter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63228706A JP2690964B2 (en) | 1988-09-14 | 1988-09-14 | Thermal air flow meter |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0277618A JPH0277618A (en) | 1990-03-16 |
| JP2690964B2 true JP2690964B2 (en) | 1997-12-17 |
Family
ID=16880528
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63228706A Expired - Lifetime JP2690964B2 (en) | 1988-09-14 | 1988-09-14 | Thermal air flow meter |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2690964B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3275547B2 (en) * | 1994-07-01 | 2002-04-15 | 株式会社デンソー | Voltage-frequency conversion circuit |
| JP2008164632A (en) * | 1998-08-18 | 2008-07-17 | Tokyo Gas Co Ltd | Temperature compensating method, temperature compensating circuit using same, sensor, and water heater |
-
1988
- 1988-09-14 JP JP63228706A patent/JP2690964B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0277618A (en) | 1990-03-16 |
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