CN108332886A - A kind of integral type quartz resonance pressure sensor structure - Google Patents

Abstract

The invention discloses a structure of an integrated quartz resonant pressure sensor, relates to the field of sensors, in particular to an integrated structure of a quartz resonant pressure sensor, which is used to solve the problem of adopting between the sensitive element and the structure of the quartz resonant pressure sensor in the prior art. Due to the problems of easy aging, difficult positioning and temperature drift caused by the pasting method, the present invention includes a sensitive element and a sensor body. The sensitive element is all made of quartz, including the element body, a resonant wafer and a first through hole. The element The main body is a cuboid structure, and the center of the front of the element body is provided with a first through hole, and the center of the first through hole is provided with a resonant chip connected to the element body. The present invention has the advantages of long life, controllable temperature drift, high sensitivity and The advantage of good linearity.

Description

An Integrated Quartz Resonant Pressure Sensor Structure

technical field

The invention relates to the field of sensors, in particular to an integrated quartz resonant pressure sensor structure.

Background technique

The pressure sensors currently on the market are nothing more than piezoresistive, piezoelectric or resonant; the sensitive unit of the piezoresistive pressure sensor is a piezoresistor, which is characterized in that when the external pressure acts on the piezoresistor, the resistance value changes , by measuring the change of the output voltage value to convert the size of the external pressure. The disadvantage of this type of sensor is that the temperature drift is serious, and it is easy to produce creep effect after long-term use, so the application accuracy requires low static force test. Piezoelectric sensors use piezoelectric quartz or ceramic materials. The biggest feature of this type of sensor is high piezoelectric coefficient and high Q value, so the test accuracy is high; but it can test dynamic force. In recent years, more and more attention has been paid to the resonant pressure sensor. It is made of piezoelectric resonant components. The frequency change of the same resonant components can sense the magnitude of the external force. Its characteristics are direct digital frequency signal output, and its accuracy is higher than the above two. In addition, this type of sensor can test both static force and dynamic force; it has attracted much attention in the case of higher precision force testing.

The biggest problem faced when making the above sensor is the installation problem between the sensitive element and the structure. The past practice is to connect the two together by pasting, which has the following problems:

1. The connection of the glue point will lead to the long-term stability of the sensor. Since the glue will have been aging for a long time due to the influence of the external temperature, it will inevitably lead to problems in the adhesion between the sensitive element and the structure.

2. The connection of glue points cannot control the adhesive force between the sensitive device and the structure. As a result, the prestress of the sensitive device in each device is inconsistent, which will inevitably lead to very poor consistency of the final product and cannot be mass-produced.

3. It is difficult to ensure the positioning relationship between sensitive devices and structures during the dispensing process.

4. Due to the different materials of glue point, structure and sensitive components, their thermal expansion coefficients are also different. When the external temperature changes, the temperature drift of the sensor cannot be controlled. Swiss Kiesler also proposed an integrated structure, but there is still a connection between the chip and the metal structure in the structure, so it is impossible to avoid the problem of temperature drift of the sensor caused by the different temperature expansion coefficients of the two materials.

Contents of the invention

The object of the present invention is: in order to solve the above problems, the present invention provides a kind of integrated quartz resonant pressure sensor structure, adopts the configuration of all quartz structure, and the cutting type of resonant wafer is consistent with structural frame, and whole structure is one-piece type, does not exist Glue point connection has the advantages of easy mass production, accurate structure positioning, and no temperature drift problem.

The technical scheme that the present invention adopts is as follows:

An integrated quartz resonant pressure sensor structure, including a sensitive element and a sensor body, the sensor body includes a base, lead wires, a bottom plate and external wiring, the bottom plate is provided with an amplification circuit, and the sensitive element is fixed in the base , the sensitive element is electrically connected to the amplifying circuit through a lead wire, and the external wire is electrically connected to the amplifying circuit. The sensitive element is entirely made of quartz, including a component body, a resonant wafer and a first through hole, and the component body is a cuboid structure, the front center of the element body is provided with a first through hole, and the center of the first through hole is provided with a resonant chip integrally connected with the element body.

Further, among the structural dimensions of the element body, the length, width and height are equal, and both are 40 mm to 42 mm.

Further, the first through hole is cylindrical and runs through the center of the front surface of the element body, and the inner diameter of the first through hole is 9 mm to 11 mm.

Further, the resonant chip has a thickness of 0.200 mm to 0.210 mm, including a force-bearing piece and a connecting piece, and two connecting pieces extend from symmetrical ends of the force-bearing piece, and the connecting piece has no connection with the inner wall of the first through hole. seam connection.

Further, the maximum width of the connecting piece is smaller than the diameter of the force-bearing piece.

Further, a second through hole is opened in the center of the side of the element body, the second through hole is cylindrical and penetrates through the center of the side of the element body, and the geometric center of the first through hole coincides with the geometric center of the second through hole .

Further, the amplifying circuit includes a resistor Rb1, a resistor Rb2, a resistor Rc1, a resistor Rc2, a capacitor C1, a variable capacitor C2, a transistor T1 and a transistor T2, and one end of the sensitive element is connected in series with the variable capacitor C2 and the resistor Rc2 in sequence. The output terminal Ec, the other end of the sensitive element is respectively connected to one end of the resistor Rb1 and the base of the triode T1, the other end of the resistor Rb1 is connected in series with the capacitor C1 and the resistor Rb2 in series and then connected to the output terminal V0, the emitter of the triode T1 The emitter of the triode T2 is grounded, the collector of the triode T1 is connected in series with the resistor Rc1 and then connected to the output terminal EC, and the base and collector of the triode T2 are connected in parallel at both ends of the resistor Rb2.

In summary, owing to adopting above-mentioned technical scheme, the beneficial effect of the present invention is:

1. The present invention adopts a one-piece structure, and there is no glue point pasting, so there is no problem of long-term aging of the pasting point, and the service life is longer.

2. The integrated structure of the present invention makes the force conduction between the element main body and the resonant wafer controllable, the prestress in each sensitive element is consistent, and the product consistency is good, which is conducive to mass production.

3. The resonant wafer and the element main body of the present invention have an integrated structure, so there is no positioning problem in the production process, and the production efficiency can be improved.

4. The resonant chip and the element body of the present invention all adopt the same cut quartz crystal, have the same expansion coefficient, and the temperature drift of the sensor is controllable when the external temperature changes.

5. The present invention improves the element body by punching holes, which maximizes the force on the resonant wafer, improves the uniformity of the force on the wafer, and has a better structural linearity, with a linear fitting error of about 7%, thereby improving the sensor's performance. sensitivity.

Description of drawings

The invention will be described by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a schematic diagram of the overall structure of the present invention;

Fig. 2 is a schematic diagram of the amplifying circuit of the present invention;

Fig. 3 is a schematic structural diagram of a sensitive element in Embodiment 1 of the present invention;

Fig. 4 is a force analysis diagram of the sensitive element in Example 1 of the present invention;

Fig. 5 is the FEM simulation figure of the sensitive element of embodiment 1 of the present invention;

Fig. 6 is a schematic structural diagram of a sensitive element in Embodiment 2 of the present invention;

Fig. 7 is a force analysis diagram of the sensitive element in Example 2 of the present invention;

Fig. 8 is a FEM simulation diagram of the sensitive element in Embodiment 2 of the present invention.

Description of drawings: 1. Sensitive element; 1-1, element body; 1-2, resonant chip; 1-2-1, force plate; 1-2-2, connecting piece; 1-3, first through hole ; 1-4, the second through hole; 2, the main body of the sensor; 3, the base; 4, the lead wire; 5, the bottom plate;

In order for those skilled in the art to better understand the invention, the invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

Example 1:

As shown in Figures 1 and 3, an integrated quartz resonant pressure sensor structure includes a sensitive element 1 and a sensor body 2, and the sensor body 2 includes a base 3, lead wires 4, bottom plate 5 and external wires 6, the The base plate 5 is provided with an amplifying circuit 7, the sensitive element 1 is fixed in the base 3, the sensitive element 1 and the amplifying circuit 7 are electrically connected through the lead wire 4, and the external wire 6 is electrically connected with the amplifying circuit 7, and the characteristic That is, the sensitive element 1 is entirely made of quartz, including an element body 1-1, a resonant wafer 1-2 and a first through hole 1-3, the element body 1-1 is a cuboid structure, and the element body 1- A first through hole 1-3 is opened in the center of the front surface of 1, and a resonant chip 1-2 connected with the element body 1-1 is arranged in the center of the first through hole 1-3.

As a preferred embodiment, among the structural dimensions of the element body 1-1, the length, width and height are all equal to 41 mm.

As a preferred embodiment, the first through hole 1-3 is cylindrical and penetrates through the front center of the element body 1-1, and the inner diameter of the first through hole is 10 mm.

As a preferred embodiment, the resonant chip 1-2 has a thickness of 0.208mm, including a force-bearing piece 1-2-1 and a connecting piece 1-2-2, and the force-bearing piece 1-2-1 is symmetrical Two connecting pieces 1-2-2 are extended from both ends of the two ends, and the connecting piece 1-2-2 is seamlessly connected with the inner wall of the first through hole 1-3.

As a preferred embodiment, the maximum width of the connecting piece 1-2-2 is smaller than the diameter of the force-bearing piece 1-2-1.

As shown in Figure 2, as a preferred embodiment, the amplifying circuit 7 includes a resistor Rb1, a resistor Rb2, a resistor Rc1, a resistor Rc2, a capacitor C1, a variable capacitor C2, a transistor T1 and a transistor T2, and one end of the sensitive element The variable capacitor C2 and the resistor Rc2 are connected in series to the output terminal Ec, and the other end of the sensitive element is respectively connected to one end of the resistor Rb1 and the base of the transistor T1, and the other end of the resistor Rb1 is connected in series with the capacitor C1 and the resistor Rb2 in turn. Connected to the output terminal V0, the emitter of the triode T1 and the emitter of the triode T2 are both grounded, the collector of the triode T1 is connected in series with the resistor Rc1 and then connected to the output terminal EC, the base and collector of the triode T2 are connected in parallel to the resistor Rb2 both ends.

When the upper surface of the entire structure is deformed after being stressed, the force is transmitted to the resonant chip in the middle, causing the resonant chip to deform. Select a node on the middle resonant chip to test the stress value corresponding to the node when the external force is applied to the surface, and evaluate the value of the stress. The linearity of the structure and its force analysis results are shown in Figure 4, and the results shown in Figure 5 are obtained by finite element method simulation, and the corresponding values are as follows:

force(N) STRESS (PA) 1000 18038.013 1250 22552.6309 2500 45112.0816 5000 90200.1631 8000 144301.202 10000 180410.228 12000 216502.073 15000 270600.342 17500 315730.604

From the simulation results, it can be concluded that the linearity of the structure in this embodiment is relatively good, and the linear fitting error is about 7%.

Example 2:

This embodiment makes the following improvements on the basis of Embodiment 1:

As shown in Figure 6, as a preferred embodiment, the center of the side of the element body 1-1 is provided with a second through hole 1-4, and the second through hole 1-4 is cylindrical and penetrates through the element body 1-1. 1, the geometric center of the first through hole 1-3 coincides with the geometric center of the second through hole 1-4.

When the upper surface of the entire structure is deformed after being stressed, the force is transmitted to the resonant chip in the middle, causing the resonant chip to deform. Select a node on the middle resonant chip to test the stress value corresponding to the node when the external force is applied to the surface, and evaluate the value of the stress. The linearity of the structure and its force analysis results are shown in Figure 7, and the results shown in Figure 8 are obtained by finite element method simulation, and the corresponding values are as follows:

force(N) STRESS (PA) 1000 6020.10555 1250 7525.13235 2500 15050.261 5000 30100.5294 8000 48160.8444 10000 60201.0588 12000 72241.2666 15000 90301.5882 17500 105352.316

From the above simulation calculations, it can be found that the way of punching holes on the side helps to concentrate the stress, and the entire linearity error is reduced by 100 times, which is helpful for the processing of the later circuit.

Working principle: Quartz crystal has a piezoelectric effect. When pressure is applied to the crystal, charges will be generated on both sides of the crystal in a certain direction, one surface will generate positive charges, and the other surface will generate negative charges; if the pressure is changed to tension (pull force), the nature of the charge is just opposite, which is the positive piezoelectric effect. Conversely, if a voltage is applied to both sides of the crystal, it will produce stretching or contracting motion, which is called the inverse piezoelectric effect. Due to the reverse piezoelectric effect of quartz crystal, under the action of AC voltage, the crystal will undergo periodic mechanical vibration, and because it has piezoelectric effect, it will cause the charge properties on both sides of the crystal during periodic mechanical vibration. Periodic changes, so a sinusoidal alternating current i is formed in the circuit. The magnitude of the alternating current is proportional to the magnitude of the mechanical vibration, that is, proportional to the magnitude of the applied alternating voltage. The amplitude of the mechanical vibration of the quartz crystal and the size of the AC current are related to the frequency of the applied AC voltage. When the frequency of the applied AC voltage is equal to the natural frequency of the crystal, the amplitude of the mechanical vibration and the AC current are the largest. This phenomenon is called The piezoelectric resonance of the quartz crystal is equivalent to the series resonance of the LC circuit. Therefore, the crystal oscillator can be equivalent to an LC series resonant tank,

When the external force acts on the edge of the quartz wafer, it will cause the deformation of the quartz wafer, hinder its resonant frequency, and cause the intrinsic frequency to change; the magnitude of the external force can be calculated by examining the change in frequency.

The above is only a preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, some modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection of the invention. scope.

Claims (7)

1. a kind of integral type quartz resonance pressure sensor structure, including sensing element (1) and sensor main body (2), the biography Sensor main body (2) includes pedestal (3), lead (4), bottom plate (5) and external connection (6), and the bottom plate (5) is equipped with amplifying circuit (7), the sensing element (1) is fixed in pedestal (3), and the sensing element (1) and amplifying circuit (7) pass through lead (4) electricity Connection, the external connection (6) are electrically connected with amplifying circuit (7), which is characterized in that the sensing element (1) is all by quartzy structure At, including component body (1-1), resonant chip (1-2) and first through hole (1-3), the component body (1-1) they are cuboid knot Structure, the front center of the component body (1-1) offer first through hole (1-3), first through hole (1-3) center be equipped with The connected resonant chip (1-2) of component body (1-1) integral type.

2. a kind of integral type quartz resonance pressure sensor structure according to claim 1, it is characterised in that：The element In the structure size of ontology (1-1), length, width and height are equal, are 40mm~42mm.

3. a kind of integral type quartz resonance pressure sensor structure according to claim 1, it is characterised in that：Described first Through-hole (1-3) cylinder front center through component body (1-1), the internal diameter of the first through hole (1-3) be 9mm~ 11mm。

4. a kind of integral type quartz resonance pressure sensor structure according to claim 1, it is characterised in that：The resonance Chip (1-2) thickness is 0.200mm~0.210mm, including stress piece (1-2-1) and connection sheet (1-2-2), the stress piece Two panels connection sheet (1-2-2) is extended at the symmetrical both ends (1-2-1), and the connection sheet (1-2-2) is interior with first through hole (1-3) Wall seamless connects.

5. a kind of integral type quartz resonance pressure sensor structure according to claim 4, it is characterised in that：The connection The maximum width of piece (1-2-2) is less than the diameter of stress piece (1-2-1).

6. a kind of integral type quartz resonance pressure sensor structure according to claim 1, it is characterised in that：The element Ontology (1-1) center side opens up the second through-hole (1-4), and second through-hole (1-4) is cylinder through component body (1- 1) center side, the geometric center of the first through hole (1-3) and the geometric center of the second through-hole (1-4) overlap.

7. a kind of integral type quartz resonance pressure sensor structure according to claim 1, it is characterised in that：The amplification Circuit (7) includes resistance Rb1, resistance Rb2, resistance Rc1, resistance Rc2, capacitance C1, variable capacitance C2, triode T1 and triode T2, one end of sensing element is connected with variable capacitance C2 and resistance Rc2 successively is followed by leading-out terminal Ec, the other end of sensing element Be connected respectively with the base stage of one end of resistance Rb1 and triode T1, the other end of the resistance Rb1 successively with capacitance C1 resistance Rb2 series connection is followed by leading-out terminal V0, and the emitter of the triode T1 is grounded with the emitter of triode T2, triode T1's Collector is connected with resistance Rc1 to be followed by the base stage and collector of leading-out terminal EC, the triode T2 and is connected in parallel on the two of resistance Rb2 End.