JPH02275332A - Pressure sensor - Google Patents

Abstract

PURPOSE:To make it possible to perform highly accurate pressure detection with a simple constitution by bonding an electronic cooling element to a diaphragm wherein a pressure sensitive resistor forming a required circuit is provided, and providing a cylindrical space which is communicated to a nozzle at the central part. CONSTITUTION:A diaphragm 8 is provided with an insulating layer 11. A pressure sensitive resistor 18 forming a bridge circuit is provided on the surface of the diaphragm 8. An electronic cooling element which is composed of a copper electrode 3, a solder layer 2, a Peltier element 1 and the like is coupled to the diaphragm 8 through an upper bonding layer 13. A discharge plate 15 is provided at the lower surface of a lower electronic cooling element. A cylindrical space is formed with a cylinder 16 which is communicated to a nozzle 17 at the lower surface of the diaphragm 8. In this constitution, cooling is effectively performed, the resistor 18 is operated at the constant temperature all the time and temperature correction is not required. Thus, a pressure sensor which can detect the pressure highly accurately with the simple constitution is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pressure sensor, and more particularly to temperature compensation in a pressure sensor in which a pressure-sensitive resistor is arranged on a diaphragm.

(Prior Art) Conventionally, a pressure sensor has been put into practical use in which a ceramic thin plate is used as a diaphragm, and a pressure sensitive resistor made of a thick film resistor formed by thick film printing and baking techniques is arranged on the diaphragm.

For example, as shown in FIGS. 8A and 8B, a pressure-sensitive resistor 28, a conductive pattern 30, etc. are formed on the lower surface of a diaphragm 38 made of a thin ceramic plate by thick film printing and firing techniques, and then a ring-shaped pedestal 26 made of ceramic is formed. A pressure sensor has been put into practical use that is bonded onto the top surface of the sensor via an adhesive layer 33 made of glass or the like.

On the other hand, a pressure sensor has also been proposed in which a pressure sensitive resistor made of a thick film resistor is placed on a diaphragm made of a thin metal plate with an inorganic insulating layer such as a glass Gerry's insulating layer interposed therebetween.

(Problems to be Solved by the Invention) In the conventional pressure sensor, the temperature characteristics of the pressure-sensitive resistor 28 are not very good, so in order to make the sensor highly accurate, it is necessary to perform temperature compensation such as using a temperature compensation circuit. Ta. This took a lot of time because it involved measuring the temperature characteristics of each sensor and then installing a temperature compensation circuit.

Furthermore, when using an inexpensive metal diaphragm, the pressure-sensitive resistor and the temperature coefficient (expansion coefficient) are different, so simply making the insulating layer between the pressure-sensitive resistor and the diaphragm have the same pressure-sensitive resistor and temperature coefficient is not sufficient for achieving high precision. However, there are some problems and it has not been put into practical use.

(Means for Solving the Problems) The pressure sensor of the present invention aims to solve the above problems.

(1) A pressure sensitive resistor is formed in the form of a full bridge circuit on the upper surface of the diaphragm, a copper electrode is fixed to the lower surface of the diaphragm via an adhesive layer, and a copper electrode is fixed to the lower surface of the fIiJ electrode via a solder layer. A thermoelectric cooling element to which a heat sink is fixed is fixed, and a cylinder and a nozzle for introducing pressure from the outside are provided on the lower surface of the diaphragm.

(2) The electronic cooling element is a Beltier element.

(Function) In the pressure sensor of the present invention, a diaphragm on which a pressure-sensitive resistor, lead wires, etc. are formed by thick film printing and baking technology forms a part of the electronic cooling element, and the pressure-sensitive resistor is used to detect the temperature of the electronic cooling element. The temperature can be detected from the temperature characteristics of the pressure-sensitive resistor, the electronic cooling element can be controlled, and the temperature of the diaphragm can be kept constant, making it possible to improve the accuracy of the pressure sensor. .

(Embodiment) An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a diagram showing the principle of electronic cooling according to the present invention, which consists of upper and lower substrates (alumina ceramic) 4, 4, with a Vertier element (electronic cooling element) 1 arranged between them, and a copper electrode 3.
are connected by solder layers 2, 2. When a current is passed through this in the direction of arrow B (tit flow), heat is released by arrow A (
heat flow). If the direction of the current is reversed, the direction of heat flow will also be reversed, allowing heating and cooling to be performed in the direction of the current.

FIG. 2 is a diagram for explaining the present invention in detail, and is a sectional view of the pressure sensor. That is, 8 is a diaphragm, and there are insulating layers 11 on both sides, and only the pressure sensitive part is a thin diaphragm, and the part that exchanges heat from the Bertier element 1 is thicker to ensure strength.

A pressure sensitive resistor 18, a conductive pattern 9, and an electrode 19 are formed on the diaphragm 8 by thick film printing and baking techniques.

A copper electrode 3 is fixed to the lower part of the diaphragm 8 via an adhesive layer 13, and the Vertier element 1 is fixed to the copper electrode 3 via a solder layer 2. The Beltier element 1 has two stages,
It is fixed with a substrate (alumina ceramic) 4 interposed between the upper and lower parts. A heat sink 15 is provided at the bottom, and a Bertier element 1 is provided.
Thermal efficiency (heat dissipation effect) is increased.

Furthermore, a cylinder 16 and a nozzle 17 for introducing pressure from the outside are provided at the lower part of the diaphragm 8. Further, a voltage is supplied to the Beltier element 1 through lead wires 12a to 12b.

FIG. 3 is a top view of FIG. 2, in which pressure-sensitive resistors 18a to 18d and conductor patterns 9. Electrode terminals 19a to 19d are provided with an insulating layer 11 in between.

Note that the insulating layer 11 is required to have heat resistance sufficient to withstand the temperature (600 to 900° C.) during firing of the pressure sensitive resistors 18 a to 18 d, the conductor pattern 9, and the electrode terminals 19 a to 19 d. The pressure sensitive resistors 18a to 18d are formed by screen printing a ruthenium oxide material on the insulating layer 11, for example.
It is formed by firing at a temperature of 00 to 900°C. The pressure sensitive resistors 18a and 18b are arranged at left and right positions near the periphery of the pressure receiving portion on the diaphragm 8, and the pressure sensitive resistors 18c and 18d are arranged above and below the center of the diaphragm 8. The electrode terminals 19a to 19d are positioned on the outside of the pressure receiving part of the diaphragm 8 by screen printing a material such as silver or silver-baladium on the insulating layer 11 and firing it at a temperature of 600 to 900°C. It is formed so that The conductor pattern 9 is formed by screen-printing a material such as silver or silver palladium on the insulating layer 11 and baking it at a temperature of 600 to 900°C, thereby forming the pressure sensitive resistors 18a to 18d and the electrode terminals 198 to 19.
d is formed to have a full bridge connection. The conductor pattern 9 is mainly formed along the periphery of the diaphragm 8 so that only the minimum necessary amount is exposed to the pressure receiving portion of the diaphragm 8.

FIG. 4 shows pressure sensitive resistors 18a to 18d, conductor pattern 9,
A circuit diagram of a full bridge circuit constituted by electrode terminals 19a to 19d, a Peltier element 1, and lead wires 12a to 12b is shown. In this full bridge circuit, when a predetermined DC voltage is applied between the electrode terminals 19b and 19d, the output voltage between the electrode terminals 19a and 19c becomes almost zero in an equilibrium state in which no pressure is applied to the sensing part of the diaphragm 8. It is set as follows.

FIG. 5 shows a temperature control circuit for the Peltier element 1.

A current is detected by a current detection resistor R1 that drives a full bridge circuit of pressure sensitive resistors 18a to 18d at a constant current using a constant current drive amplifier 20. Reference voltage 21.

The temperature target value voltage VC is generated by adjusting with the variable resistor 24. Temperature feedback voltage VB.

Input the temperature target value voltage VC to the error amplification amplifier 22,
The Peltier element 1 is driven by the Peltier element applied voltage Vp via the current boost transistors 23a and 23b.

The pressure detection signal is input to the instrumentation amplifier 25.

FIG. 6 is an example of a temperature characteristic graph of the resistance values of the pressure sensitive resistors 18a to 18d. In FIG. 5, electrode terminals 19b-1
The resistance value between 9d shows the characteristics shown in FIG.

The current detection resistor R1 has a flat temperature characteristic and a constant drive current, so for the temperature feedback voltage VB, let the drive current be IB and the bridge resistance (resistance value between 19b and 19d) be RB.

VB=IBX (RB+R1) In the above formula, IB and R1 are constant.

The relationship vBOe:RB is established, and in FIG. 6, it can be seen that the resistance value RB has a correlation with the thermometer, so that VB can be used as a temperature feedback signal.

FIG. 7 is a graph showing the relationship between the pressure-receiving gas temperature TO and the Peltier element applied voltage vP, in which the Peltier element applied voltage vP is controlled by the temperature feedback voltage VB in accordance with the temperature, and the pressure-sensitive resistors 18a to 18a. The temperature of 18d changes to remain constant.

(Effects of the Invention) As explained above, according to the present invention, there is no need to measure the temperature characteristics of the pressure sensor, and a high-precision pressure sensor can be achieved even by using an inexpensive metal diaphragm. By introducing the pressure gas through the diaphragm, the temperature of the pressure-receiving gas in contact with the diaphragm can be kept constant.1 A highly stable pressure sensor, which cannot be easily obtained with normal temperature compensation, becomes possible. Further, since a pressure-sensitive resistor is used for temperature detection without the need to separately provide a temperature detection element such as a thermistor, detection errors can be reduced because the object of temperature compensation and the detection element are the same.

Furthermore, by keeping the pressure-sensitive resistor at a constant temperature, there is no drift in sensitivity as well as zero-point drift, and the set temperature can be set arbitrarily, so pressure can be detected at the temperature where the pressure-sensitive resistor is in the best operating condition, resulting in high stability. A highly reliable, long-life pressure sensor can be created.

[Brief explanation of drawings]

Fig. 1 is a principle diagram of a thermoelectric cooling element, Fig. 2 is a broken sectional view showing an embodiment of the present invention, Fig. 3 is a top view showing an embodiment of the invention, and Fig. 4 is a pressure sensitive resistor. The bridge and the Peltier device circuit diagram, and FIG. 5 is the Peltier device control circuit diagram. 6th
FIG. 7 is a graph of the pressure-sensitive resistor temperature characteristic, FIG. 7 is a graph of the voltage applied to the Peltier element of the pressure-receiving gas temperature body, and FIGS. 8A and 8B are a cross-sectional view and a top view, respectively, showing a conventional example. 1... Peltier element 2... Solder layer 3... Copper electrode 4... Substrate 8... Diaphragm 9... Conductor pattern 11...
Insulating layers 12a, 12b... Lead wire 13... Adhesive layer 15... Heat sink 16... Cylinder 17... Nozzle 18.18a ~18d...pressure sensitive resistor 19,
19 a to 19 d-.-@pole terminal 20... Constant current drive amplifier 21... Reference voltage 22... Error amplification amplifier 23a, 23b... Current boost transistor 24... Variable resistor 25...
...Instrumentation amplifier VC...Temperature target value voltage Vp...Peltier element applied voltage VB...
・Temperature feedback voltage R1...Current detection resistor

Claims (2)

[Claims] (1) A pressure sensitive resistor is formed in the form of a full bridge circuit on the upper surface of the diaphragm, a copper electrode is fixed to the lower surface of the diaphragm via an adhesive layer, and a pressure sensitive resistor is fixed to the lower surface of the diaphragm via a solder layer. 1. A pressure sensor characterized in that a thermoelectric cooling element having a heat sink fixed thereto is fixed thereto, and a cylinder and a nozzle for introducing pressure from the outside are provided on the lower surface of the diaphragm. (2) The pressure sensor according to claim 1, wherein the electronic cooling element is a Peltier element.