JPH06249864A - Wind speed sensor - Google Patents

Abstract

PURPOSE:To provide a wind speed sensor which can detect the wind speed with high precision, even if the environmental temperature varies, hardly transmitting heat to a sensor for temperature compensation from a wind speed detecting sensor. CONSTITUTION:A wind speed detecting sensor RH is installed on one edge side of a ceramic substrate 10, and a sensor RT for temperature compensation is directly formed on the other edge side through the printing or vapor deposition of platinum material. Further, a signal circuit part 20 of a hybrid IC is directly formed on the ceramic substrate 10 surface between both the sensors RH and RT through printing or vapor deposition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant temperature difference method wind speed sensor.

[0002]

2. Description of the Related Art FIG. 5 shows a basic circuit of a general wind speed sensor of a constant temperature difference method. In the figure, the power source 4 is connected to the input end 2 side of the four sides of the bridge circuit 1 via the transistor 3, and the other input end 5 side of the bridge circuit 1 is connected to the ground. A resistor R ₁ is connected between the input end 2 and the output end 6, and a wind speed detecting sensor RH is connected between the output end 6 and the ground. Further, a resistor R ₂ is provided between the input end 2 and the output end 8.
Is connected, and the temperature compensating sensor RT is connected between the output terminal 8 and the ground. The difference between the bridge side output voltage V _{H of} the wind speed detecting sensor RH and the bridge side output voltage V _T of the temperature compensating sensor RT is The differential output obtained by a differential amplifier 11 such as an operational amplifier is output to the base of the transistor 3 while being output as a wind speed detection signal.

The wind speed detecting sensor RH and the temperature compensating sensor RT are both composed of a platinum temperature sensitive resistance element having a positive temperature coefficient of resistance.
The resistance temperature coefficient of T is larger than that of a general resistor by one digit or more, and a resistance temperature coefficient of T that is substantially the same is used. The combined resistance value of the resistor R ₂ and the temperature compensation sensor RT is sufficiently larger than the combined resistance value of the resistor R ₁ and the wind speed detecting sensor RH.
As a result, the wind speed detecting sensor RH self-heats and functions as a heater by the current from the power source 4, while the temperature compensating sensor RT has a function of detecting the temperature of the airflow while keeping the self-heating state. This wind speed sensor RH
The resistance value of each bridge side is set such that the output voltages of the bridge terminals 6 and 8 are in a balanced state when the temperature difference between the temperature compensation sensor RT and the temperature compensation sensor RT becomes a set constant temperature difference.

In this type of wind speed sensor, when the air flow passes through the wind speed detecting sensor RH, the heat radiation amount of the wind speed detecting sensor RH changes according to the magnitude of the wind speed of the air flow, and the resistance value changes. The voltage V _{H at the} output terminal 6 changes due to the change in the resistance value. At this time, the difference between the voltage V _{T at} the output terminal 8 corresponding to the temperature of the air flow and the V _H is obtained by the differential amplifier 11, so that the influence of the temperature change of the air flow is removed, and the temperature-compensated differential signal is removed. The differential output of the amplifier 11 is taken out as a wind speed detection signal. On the other hand, as a result of the differential output being applied to the transistor 3, the current from the power source 4 flows to the wind speed detecting sensor RH and heat generation is performed by the amount of heat radiated by the air flow, and the wind speed detecting sensor RH and temperature compensation It is controlled so that the temperature difference from the sensor RT is always constant.

FIG. 3 shows a structural diagram of a wind speed sensor used in an automobile or the like. This wind speed sensor is provided with a sampling pipe 9 in a tubular pipe 7, and the sampling pipe 9
A wind speed detecting sensor RH and a temperature compensating sensor RT shown in the basic circuit of FIG. 5 are provided therein. In this wind speed sensor, the wind speed detection sensor RH and the temperature compensation sensor RT are connected to different positions in the sampling tube 9, respectively.
Further, since the signal circuit provided on a circuit board (not shown) and both sensors RH and RT are connected for assembly, the assembly work is troublesome, and the structure is complicated and large. Therefore, there is a problem that the work efficiency is low and the cost is high.

To solve the above problems, the applicants have proposed a wind speed sensor of the type in which the sensors RH and RT are formed on a substrate as shown in FIG. In this wind velocity sensor, the circuit shown in FIG. 5 is mounted on an epoxy board 14, and the epoxy board 14 is a chip part of a signal circuit 20 including the bridge circuit 1 of the basic circuit shown in FIG. Are formed by soldering or the like. Further, the separately prepared wind speed detecting sensor RH and the temperature compensating sensor RT are juxtaposed side by side from the edge portion of the epoxy substrate 14, and in this state, they are adhered to the substrate 14 by an adhesive or the like, and both sensors RH, RTs are closely arranged.

[0007]

However, since the wind speed sensor RH and the temperature compensating sensor RT are separately manufactured in the wind speed sensor of the above-mentioned proposed example, it is difficult to control the manufacturing conditions to be the same. By all means RH and R
Variation in the temperature coefficient of resistance (TCR) with T
There is a problem that the TCRs of RT and RT are not the same. Therefore, since the sensor output (wind speed detection signal) changes when the environmental temperature changes, there is a problem that the wind speed cannot be detected accurately.

Further, since the sensor RH and the sensor RT are arranged close to each other, there is a problem that the sensor RT is likely to receive the heat of the sensor RH. Therefore, the temperature compensating sensor RT is provided.
There is a problem in that the temperature of the air flow cannot be accurately detected due to the heat transferred from the outside and the temperature compensation function cannot be fully exerted.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to transfer almost no heat from the wind speed detecting sensor to the temperature compensating sensor and to change the environmental temperature. The present invention provides a wind speed sensor capable of detecting wind speed with high accuracy.

[0010]

In order to achieve the above object, the present invention is constructed as follows. That is, in the wind speed sensor of the present invention, a wind speed detection sensor is formed on one end side of the same ceramic substrate, and a temperature compensation sensor is formed on the other end side thereof directly on the ceramic substrate by printing, sputtering or vapor deposition of a resistance element material. The signal circuit section of the hybrid IC is directly formed on the ceramic substrate surface between the sensors.

Further, in the wind speed sensor of the present invention, a wind speed detecting sensor is formed on one end side of the same circuit board, a temperature compensating sensor is formed on the other end side, and a signal circuit section is formed on the board surface between both sensors. The front and back surfaces of this circuit board are covered with a conductor case, and the circuit board and the conductor case are fixed by a heat conductive adhesive.

[0012]

When the power of the wind speed sensor is turned on and the circuit operation is performed, the wind speed detection sensor generates heat. The wind speed detection sensor is located on one end side of the ceramic substrate and the temperature compensation sensor is located on the other end side and is not in close proximity, so the heat of the wind speed detection sensor is attenuated by freely setting the distance between them. Then, the heat is not applied to the temperature compensation sensor. As a result, the temperature compensating sensor can sufficiently exhibit the function of temperature compensation. Further, since the wind speed detection sensor and the temperature compensation sensor can be manufactured on the same ceramic substrate under the same conditions, the temperature coefficient of resistance of both sensors becomes almost the same,
It is possible to reduce variations in temperature characteristics between products as wind speed sensors.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. In the description of the present embodiment, the same reference numerals will be given to the same names as those in the proposed example, and detailed description thereof will be omitted. FIG. 1 shows the main configuration of the wind speed sensor of the first embodiment.

The characteristic of this embodiment is that the signal circuit section 20 of the hybrid IC is printed on the same ceramic substrate 10 made of alumina, between the wind speed detecting sensor RH and the temperature compensating sensor RT, and both sensors RH and RT. That is, it was formed directly by sputtering or vapor deposition.

In this embodiment, the platinum film 16 for the wind speed detecting sensor RH is formed on the one end side and the other end side of the rectangular ceramic substrate 10 by the same manufacturing conditions such as printing, vapor deposition or sputtering. A platinum film 16 for RT for temperature compensation is simultaneously formed. Next, both platinum films 16 are subjected to laser treatment or etching treatment to form a resistance circuit pattern, one side is formed as a wind speed detecting sensor RH, and the other end side is formed as a temperature compensating sensor RT. Usually, the resistance value of RT is 10 times or more the resistance value of RH. Also, RH and RT
Since the platinum material is formed by vapor deposition or sputtering under the same manufacturing conditions, the temperature coefficient of resistance (TCR) of RH and RT is almost the same.

Next, the signal circuit section 20 of the hybrid IC is formed by printing or the like on the surface of the ceramic substrate 10 between the sensors RH and RT to form the wind speed sensor 21.

According to the first embodiment, the ceramic substrate 10
Since the wind speed detecting sensor RH is formed on one end side and the temperature compensating sensor is formed on the other end side under the same manufacturing conditions, the resistance temperature coefficients of both sensors RH and RT are substantially the same.

As described above, since the temperature coefficient of resistance (TCR) of the wind speed detecting sensor RH and the temperature compensating sensor RT can be regarded as the same, the circuit formation and the handling of the circuit are facilitated. That is, when the α both temperature coefficient of resistance RH and _{RT (TCR), RH R =} RH 0 (1 + αT H) ····· (1) RT R = RT 0 (1 + αT A) ····· ( 2) Resistance of RH RH _R here, RT _R is the resistance value of RT, RH ₀ is the resistance value of RH at 0 ° C., RT ₀ is the resistance value of RT at 0 ° C., T _H is RH temperature, T _A is It is the temperature of RT (the temperature of the airflow to be measured). On the other hand, RH
The amount of heat P that is lost from the heating element of (1) in a unit time is expressed by the following equation. P = (A + B√v) ( T H -T A) ····· (3) where, A, B are constants, v indicates the flow velocity of the gas. here,
P is when the current through RH and I equal to the calorific value of RH, the _{^{I 2 RH R = (A +}} B√v) (T H -T A) ····· (4) a V ₀ sensor output voltage Then, from the equilibrium condition of the bridge circuit, R ₁ RT _R = R ₂ RH _R (5) I = RT _R V ₀ / RH _R (R ₂ + RT _R ) (6) ( 4), (from _{6), V 0 = (R 2 +} RT R) {RH R (A + B√v) (T H -T A)} 1/2 ····· (7) (1), ( 2), (3), and (7), V ₀ = (R ₂ + RT _R ) {R ₁ (R ₁ / RH ₀ −R ₂ / RT ₀ ) (A + B√v) / α} ^1/2 / R ₂ (8) Here, if RT ₀ = R ₂ , then equation (8) is as follows. V ₀ = (1+ (α / 2 · T _A )) (C + D√v) ^1/2 (9) However, C and D are constants. Therefore, the sensor output voltage V ₀ is a TCR of α / 2. It turns out that In this case, in order to make the temperature characteristic of the sensor flat, a circuit having a TCR of -α / 2 is added to the position of the output side (Vout) 17 of the basic circuit of FIG. A resistor having a −CR / 2 TCR for reducing the temperature characteristic may be inserted at, for example, 12 positions on the RT side. Thus, RH and RT TCR
The fact that they are the same makes it extremely easy to design an electric circuit.

Further, the signal circuit section 20 of the hybrid IC is formed on the surface of the ceramic substrate 10 between the two sensors RH and RT by printing or the like, and both the sensors RH and RT are also formed by printing, sputtering or vapor deposition. As in the example, both the sensors RH, RT and the signal circuit section 20 are not required to be attached to the epoxy substrate 14 by using adhesive or solder, and the troublesome work becomes unnecessary, and the work is extremely simple and uniform in manufacturing. A product can be manufactured, and the work efficiency can be significantly improved and the cost can be significantly reduced.

Furthermore, since RH and RT are provided on both ends of the ceramic substrate, the distance between RH and RT can be freely set, and there is no concern of heat conduction from RH to RT, and accuracy is improved. A high wind speed sensor can be obtained.

FIG. 2 shows the wind speed sensor of the second embodiment. This wind speed sensor has both front and back surfaces of the ceramic substrate 10 of the wind speed sensor 21 of the first embodiment shown in FIG.
It is covered with a conductor case 15 made of aluminum or the like. Through holes A, B and C are provided in the conductor case 15, and the ground side of the wind speed sensor 21 and the conductor case 15 are in a conductive state with a heat conductive adhesive 18 It is fixed by adhesion. The heat conductive adhesive 18 preferably has conductivity.

In the second embodiment, the wind speed sensor 21 of the first embodiment is covered with a conductor case 15 made of aluminum or the like, and the ground side of the wind speed sensor 21 is electrically connected to the conductor case 15 so that the heat conductive adhesive 18 The heat generated in the wind speed detecting sensor RH and the signal circuit section 20 is transferred to the conductor case 15 via the heat conductive adhesive 18, and the heat dissipation effect of the conductor case 15 (the heat conductivity of the aluminum case) is fixed. Is more than 10 times as much as that of alumina), and it is possible to suppress heat from flowing into the temperature compensating sensor RT to a minimum.

Further, since the conductor case 15 and the ground side of the circuit of the ceramic substrate 10 are connected in a conductive state, the conductor case 15 serves as an electrical ground, so that the wind speed detection sensor RH and the temperature compensation sensor RT and The signal circuit unit 20 can be electrically shielded from the outside, and the influence of noise from the outside can be suppressed.

The present invention is not limited to the above-mentioned embodiments, and various embodiments can be adopted. For example, in the above embodiment, the alumina ceramic substrate 10 is used as the circuit substrate, but a ceramic substrate such as zirconia may be used instead of the alumina substrate.

An epoxy substrate 14 may be used instead of the ceramic substrate 10. Also in this case, since the RH is fixed to one end of the substrate 14 and the RT is fixed to the other end, the heat of the RH is less likely to be transferred to the RT as compared with the proposed example, and the function of the RT for temperature compensation is improved. This is the same as the second embodiment.
RT and signal circuit section if covered and shielded by the conductor case 15.
The heat of 20 is dissipated by the conductor case 15 and hardly transmitted to the RT, the temperature compensation function of the RT is further improved as compared with the proposed example, and the effect of noise from the outside can be suppressed by the shielding effect. However, as in this embodiment, the ceramic substrate 10
By using, the TCRs of RH and RT can be made almost the same, and the heat dissipation effect is also excellent, so the performance as a sensor is further greatly improved.

Further, although the aluminum case is used as the conductor case 15 of the second embodiment, for example, a metal case such as iron or copper may be used, and the case material may be any material as long as it has a large heat dissipation effect.

Furthermore, although the platinum material is used as the sensor material in the above embodiment, a resistance element material other than the platinum material can be used.

[0028]

According to the present invention, the wind velocity detecting sensor is formed on one end side of the same ceramic substrate and the temperature compensating sensor is formed on the other end side thereof directly on the ceramic substrate by printing, sputtering or vapor deposition. Since the temperature coefficient of resistance of the temperature compensation sensor can be made substantially the same as that of the temperature compensation sensor, the temperature compensation function can be sufficiently exerted and a highly accurate wind speed sensor can be manufactured.

Further, since the wind speed detecting sensor, the temperature compensating sensor, and the signal circuit of the hybrid IC are formed on the ceramic substrate, the work is easy and a uniform small wind speed sensor with no variation can be manufactured. As a result, it is possible to significantly improve the work efficiency and the manufacturing cost.

Further, since the wind speed detecting sensor is provided on one end side of the same ceramic substrate and the temperature compensating sensor is provided on the other end side thereof, the two sensors are not close to each other, and the heat of the wind speed detecting sensor compensates for the temperature. There is little influence on the sensor for use. Moreover, the front and back sides of the circuit board are covered with conductor cases,
Since the circuit board and the conductor case are fixed in a conductive state by a heat conductive adhesive, the heat of the signal circuit part such as the sensor for wind speed detection and the hybrid IC is radiated by the conductor case and does not easily go around to the temperature compensation sensor. Therefore, the temperature compensation sensor can sufficiently exert the temperature compensation function.

Furthermore, since the ground side of the circuit board and the conductor case are connected in a conductive state, the influence of noise from the outside can be suppressed.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a main part configuration of a wind speed sensor according to a first embodiment.

FIG. 2 is an explanatory diagram of a wind speed sensor according to a second embodiment.

FIG. 3 is a structural diagram of a conventional wind speed sensor used in an automobile or the like.

FIG. 4 is an explanatory diagram of a conventional wind speed sensor.

FIG. 5 is a basic circuit diagram of a wind speed sensor.

[Explanation of symbols]

 10 Ceramic substrate 14 Epoxy substrate 15 Conductor case 16 Platinum film 18 Thermally conductive adhesive 20 Signal circuit part RH Wind velocity detection sensor RT Temperature compensation sensor

Claims (2)

[Claims] 1. A wind speed detecting sensor is formed on one end of the same ceramic substrate, and a temperature compensating sensor is formed on the other end of the same ceramic substrate directly on the ceramic substrate by printing or vapor deposition of a resistance element material. A wind speed sensor in which the signal circuit of the hybrid IC is directly formed on the surface. 2. A wind speed detecting sensor is provided on one end side of the same circuit board, a temperature compensating sensor is provided on the other end side thereof, and a signal circuit section is formed on a board surface between both sensors. Both sides are covered with a conductor case, and the circuit board and conductor case are fixed with a heat conductive adhesive.