JP2010025582A - Pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-accuracy pressure sensor capable of reducing a pressure error due to gravity. <P>SOLUTION: The pressure sensor 10 has: diaphragms (a first diaphragm 14, a second diaphragm 16) which seal up openings 12a, 12b at both ends of a cylindrical housing 12; and a pressure-sensitive element 18 wherein a detection axis is set to a force detection direction and whose longitudinal both ends are connected to the diaphragms. The pressure sensor has reaction force generating sections (a first reaction force generating section 20, a second reaction force generating section 22), which are connected to the diaphragms and apply forces in the direction opposite to the gravity which the diaphragms receive to the diaphragms by the principle of a lever. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pressure sensor using a pressure-sensitive element and a diaphragm, and more particularly to a technique for reducing a measurement error of pressure caused by the deflection of the diaphragm due to gravity.

  Conventionally, a pressure sensor using a piezoelectric vibration element as a pressure-sensitive element is known as a water pressure gauge, a barometer, a differential pressure gauge, or the like. In the piezoelectric vibration element, for example, an electrode pattern is formed on a plate-shaped piezoelectric substrate, and a detection axis is set in the force detection direction. When pressure is applied in the direction of the detection axis, The resonance frequency changes, and the pressure is detected from the change in the resonance frequency. Patent Document 1 discloses a pressure sensor using a piezoelectric vibration element as a pressure sensitive element. When pressure is applied to the bellows through the pressure inlet, a force F corresponding to the effective area of the bellows is applied as a compression or tension force to the piezoelectric vibration element via force transmission means having a pivot (flexible hinge) as a fulcrum. A stress corresponding to the force F is generated in the piezoelectric vibrator, and the resonance frequency changes due to the stress. The pressure sensor measures pressure by detecting a change in resonance frequency generated in the piezoelectric vibrator.

Below, the conventional pressure sensor is demonstrated using the example currently disclosed by patent document 1. FIG. FIG. 7 is a schematic diagram showing the structure of a first conventional pressure sensor.
A conventional pressure sensor 101 shown in FIG. 7 includes a housing 104 having first and second pressure input ports 102 and 103 arranged to face each other, and a force transmission member 105 inside the housing 104. The first bellows 106 and the second bellows 107 are connected so as to sandwich one end of the force transmission member 105. The other end of the first bellows 106 is connected to the first pressure input port 102, and the other end of the second bellows 107 is connected to the second pressure input port 103. Further, a double tuning fork vibrator 109 is disposed as a pressure sensitive element between the other end of the force transmission member 105 and the end of the substrate 108 which is not a pivot (fulcrum).

  Here, in the pressure sensor, when the pressure is detected with high accuracy, the bellows is filled with liquid. As the liquid, oil such as silicone oil having high viscosity is generally used in order to prevent bubbles from entering or collecting inside the bellows or the bellows portion.

  Thus, the viscous oil 110 is filled in the first bellows 106, and when the pressure measurement target is liquid, the opening 111 opened in the first pressure input port 102 is provided. Therefore, the liquid and the oil 110 are in contact with each other and face each other. The opening 111 has an opening diameter that prevents the oil 110 from leaking to the outside.

  In the pressure sensor 101 having such a configuration, when the pressure F is applied to the oil 110 filled in the first bellows 106 from the liquid whose pressure is to be measured, the pressure F is passed through the first bellows 106. , Applied to one end of the force transmission member 105. On the other hand, atmospheric pressure is applied to the second bellows 107, and a force corresponding to atmospheric pressure is applied to one end of the force transmission member 105.

  As a result, the force corresponding to the differential pressure between the pressure F applied from the liquid whose pressure is to be measured via the other end of the force transmission member 105 and the pressure due to the atmospheric pressure is used as a fulcrum for the double tuning fork. A compressive force or a tensile force is applied to the mold vibrator 109. When compressive force or tensile force is applied to the double tuning fork type vibrator 109, stress is generated in the double tuning fork type vibrator 109, and the resonance frequency changes according to the magnitude of the stress. Therefore, the resonance frequency is measured. Thus, the magnitude of the pressure F can be detected.

  By the way, the first bellows 106 and the second bellows 107 which are the mechanical parts constituting the above-described pressure sensor are made by cutting out an aluminum block to form a mold, and after nickel-plating the mold, It is melted and removed to form a nickel bellows structure. Therefore, the bellows is expensive because it requires complicated processing steps for manufacturing.

  Further, the force transmission member 105 has a portion fixed to the housing 104 with a pivot (fulcrum) having a width of 1 mm or less as a contact point and a portion for transmitting the force, but these are integrated by machining from an integrated metal block. Therefore, it is difficult to process, and the manufacturing cost is expensive.

  For these reasons, pressure sensors with reduced manufacturing costs have been developed without using the bellows or force transmission member described above. As such a pressure sensor, in Patent Document 2, a piezoelectric substrate is used as a pressure sensitive element in an internal space formed by laminating two piezoelectric diaphragms having recesses on at least one main surface of a piezoelectric substrate so that the recesses face each other. In the pressure sensor in which the vibrator is arranged, both ends of the piezoelectric vibrator are fixed to the inner bottom surface of one of the concave portions of the piezoelectric diaphragm, and the inner bottom surfaces of the concave portions of the two piezoelectric diaphragms are connected by a force transmission column. Is disclosed.

FIG. 8 shows a pressure sensor according to the second prior art.
A pressure sensor 121 shown in FIGS. 8A and 8B (cross-sectional view taken along line AA in FIG. 8A) is a mounting in which a double tuning fork vibrator 122 is provided on an inner bottom surface 125 of a quartz diaphragm having a recess 124. The quartz diaphragm 128 and the quartz diaphragm 123, which are fixed to the mounting portions 127a and 127b and have the concave portion 129, are coupled with the concave opening surfaces facing each other. In addition, force transmission pillars 126a and 126b are provided to couple the quartz diaphragm 128 and the quartz diaphragm 123 in the vicinity of the center.

  The quartz diaphragms 123 and 128 are circular, and the concave portions 124 and 129 included in the quartz diaphragms 123 and 128 are circular concave portions. If the quartz diaphragm 123 is on the base side and the quartz diaphragm 128 is on the lid side, the mounting portions 127a and 127b and the force transmission members 126a and 126b for fixing the double tuning fork vibrator 122 to the quartz diaphragm 123 on the base side. To form. The force transmission column portions 126a and 126b connect the inner bottom surfaces of the concave portion 124 of the quartz diaphragm 123 and the concave portion 129 of the quartz diaphragm 128 to constitute the pressure sensor 121.

  In the above configuration, as shown in FIG. 8C, when the pressure P1 and the pressure P2 are the same, the quartz diaphragm is not deformed and no stress is applied to the double tuning fork vibrator 122. The tuning fork vibrator 122 oscillates at a reference resonance frequency f0.

  When the pressure P1 is higher than the pressure P2 (positive pressure), as shown in FIG. 8 (d), the center of the quartz diaphragm is pushed out to the side to which the pressure P2 is applied, whereby the quartz diaphragm plane is curved. In this state, since the extensional stress as shown by the arrow in the figure is applied to the double tuning fork vibrator 2, the oscillation frequency of the double tuning fork vibrator 2 changes in a direction rising from the frequency f0. On the other hand, when the pressure P1 is lower than the pressure P2 (negative pressure), as shown in FIG. 8 (e), the center of the quartz diaphragm is pushed out to the side to which the pressure P1 is applied, and this causes the quartz diaphragm plane to be curved. In the state, since the compressive stress as indicated by the arrow in the figure is applied to the double tuning fork vibrator 2, the oscillation frequency of the double tuning fork vibrator 2 changes in a direction lower than the frequency f0.

Therefore, according to the invention of Patent Document 2, since the polarity of positive pressure and negative pressure can be detected, the number of components can be reduced from Patent Document 1, and the essential low profile as a device element is possible. A pressure sensor capable of measuring relative pressure is realized.
Japanese Patent Laid-Open No. 56-119519 JP 2004-132913 A

  However, the configuration of Patent Document 2 has caused a new problem. That is, the pressure sensor of Patent Document 1 is configured on the premise that the pressure sensor is used while being kept horizontal, and there is no problem as long as the force transmission means is balanced by a pivot (fulcrum).

  On the other hand, in the pressure sensor 121 of Patent Document 2, the upper and lower quartz diaphragms receive a downward force due to the gravity of the earth. If the pressure sensor 121 is turned upside down, the upper and lower quartz diaphragms will act in the opposite direction due to the gravity of the earth. Thus, the pressure sensor is originally intended to measure only the pressure of gas / liquid, but an error occurs in the pressure measurement value depending on the installation posture. The mounting portions 127a and 127b formed on the lower quartz diaphragm 123 directly receive the holding of the double tuning fork vibrator, which is a pressure-sensitive element, from a place completely different from the mounting portion described above. Since the force transmission column 126 is connected to the upper crystal diaphragm 128, accurate differential pressure measurement cannot be performed.

  Accordingly, the present invention focuses on the above-described problems, and an object thereof is to provide a high-accuracy pressure sensor in which the change in how gravity acceleration is applied and the influence of vibrations generated thereby are reduced.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following application examples.
[Application Example 1] A diaphragm for sealing openings at both ends of a cylindrical housing;
A pressure sensor having a force detection direction as a detection axis and both ends in the longitudinal direction connected to the diaphragm, the pressure sensor being connected to the diaphragm and in a direction opposite to the gravity that the diaphragm receives according to the principle of an insulator A pressure sensor, comprising: a reaction force generation unit that applies a force to the diaphragm.

  With the above configuration, the diaphragm receives a force from the reaction force generating unit in the opposite direction to the gravity received by the diaphragm, so the displacement of the diaphragm due to the gravity is canceled, and accordingly, the stress to the pressure sensitive element due to the displacement is also reduced. Offset. Therefore, a pressure sensor with reduced pressure error due to gravity is obtained.

  Application Example 2 Principle of an insulator using a first housing and a cylindrical housing, a first diaphragm and a second diaphragm for sealing openings at both ends of the housing, and the first diaphragm The first diaphragm is applied to the first diaphragm by a force in the direction opposite to the gravity received by the first diaphragm, and the second diaphragm is connected to the second diaphragm by a lever principle using a second weight. A second reaction force generating unit that applies a force in the direction opposite to the gravity received by the second diaphragm, the inside of the housing, the detection direction of the force as a detection shaft, one end connected to the first diaphragm, and the like A pressure sensor having an end connected to the second weight.

  In the above configuration, the pressure is applied in the direction in which the pressure sensitive element is pushed out of the first diaphragm by the pressure received by the first diaphragm, and the pressure is applied in the direction in which the pressure sensitive element is attracted to the second diaphragm by the pressure received by the second diaphragm. It takes. However, when the pressures received by the first diaphragm and the second diaphragm are the same, the pressure-sensitive element is not loaded even though its position moves. Therefore, it becomes a pressure sensor which can measure the relative pressure which detects the pressure difference of the 1st diaphragm and the 2nd diaphragm. In addition, since the detection axis of the pressure sensitive element and the displacement directions of the first diaphragm and the second diaphragm are aligned on the same axis, the pressure difference between the first diaphragm and the second diaphragm can be accurately measured.

  Further, with the above configuration, the first reaction force generation unit always applies a force in the opposite direction to the combined force of the bending deformation stress caused by the gravity received by the first diaphragm and the gravity received by the pressure sensitive element, thereby generating the second reaction force. Since the unit always gives a force in the opposite direction to the resultant force obtained by subtracting the gravity received by the pressure sensitive element from the stress of the bending deformation caused by the gravity received by the second diaphragm, the displacement due to the gravity received by the first diaphragm and the second diaphragm is offset. In addition, the stress caused by the gravity applied to the first diaphragm and the second diaphragm is offset by the pressure sensitive element. Therefore, the pressure-sensitive element detects only the pressure difference between the first diaphragm and the second diaphragm, and becomes a pressure sensor that reduces the influence of the change of the gravitational acceleration and the vibration generated thereby.

Application Example 3 The pressure sensor according to Application Example 2, wherein the first reaction force generation unit is formed in a pair with the pressure sensitive element interposed therebetween.
As a result, another first reaction force generator is arranged at a symmetrical position with respect to the first reaction force generator that is not on the detection axis of the pressure sensitive element. The gravity balance on the side is maintained, and the inclination angle dependency of the measurement error of the pressure sensor is improved. Further, since the stresses other than the detection axis direction applied to the pressure sensitive element by the pair of first reaction force generation units are canceled out, a more accurate pressure sensor is obtained.

Application Example 4 The pressure sensor according to Application Example 2 or 3, wherein the second reaction force generation unit is formed in a pair with the pressure-sensitive element interposed therebetween.
As a result, the force in the direction other than the detection axis direction applied by the pair of second reaction force generation units to the pressure sensitive element is canceled out, so that a pressure sensor with higher accuracy can be obtained. In particular, when the present application example and the application example 2 are combined, the pressure sensitive element hardly receives a force in a direction other than the detection axis direction, so that a highly accurate pressure sensor can be constructed.

  Application Example 5 The first reaction force generation unit and the second reaction force generation unit are supported via a fixing unit fixed to the housing, and the fixing unit is provided at the center of the side surface of the housing. The pressure sensor according to any one of Application Examples 2 to 4, wherein the pressure sensor is fixed.

  Thereby, even when the components inside the housing and the material of the housing are different, it is possible to reduce the measurement error of the pressure accompanying the temperature change caused by the difference in the linear expansion coefficient.

  [Application Example 6] Pressure according to any one of Application Examples 2 to 5, wherein a metal film is disposed on at least one surface of the first weight and the second weight. Sensor.

  Since the metal film is disposed after the construction of the first weight and the second weight, an opportunity to adjust the weight on the weight side is increased, and by arranging an appropriate amount of the metal film, the metal film is disposed on the weight side. By finely adjusting the weight, the balance between each weight and each diaphragm can be easily adjusted.

Application Example 7 The pressure sensor according to Application Example 6, wherein the metal film can be partially or completely peeled off.
Since the metal film is peeled off after the metal film is disposed, the weight side weight is further increased, and the metal film can be peeled off with a laser or the like. Since the weight on the weight side can be adjusted even after the pressure sensor is constructed, the pressure sensor yield is improved.

  Hereinafter, a pressure sensor according to the present invention will be described in detail with reference to embodiments shown in the drawings. However, the components, types, combinations, shapes, relative arrangements, and the like described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention only unless otherwise specified. .

  A pressure sensor 10 according to the first embodiment is shown in FIG. The pressure sensor 10 according to the first embodiment measures relative pressure, and includes a housing 12, a first diaphragm 14, a second diaphragm 16, a pressure-sensitive element 18, a first reaction force generator 20, and a second reaction force. A generation unit 22 and a fixing unit 24 are included.

  The housing 12 seals the inside to a vacuum and accommodates each component described later. As a result, the pressure sensor 10 can increase the Q value of the pressure-sensitive element 18 and ensure a stable resonance frequency, so that the long-term stability of the pressure sensor 10 can be ensured.

  The housing 12 has a cylindrical shape with both ends opened, and a first diaphragm 14 and a second diaphragm 16 described later are connected to the respective openings 12a and 12b. A hermetic terminal 26 is disposed at the center of the side surface of the housing 12, and wiring (wiring 18 c, wiring 20 d, wiring 24 c) from the pressure-sensitive element 18 described later inside the housing 12 and pressure-sensitive outside the housing 12. A wiring (not shown) from an oscillation circuit (not shown) of the element 18 can be connected. The material of the housing 12 may be any material as long as it has a certain rigidity, but is preferably a metal or ceramic having a small linear expansion coefficient.

  The first diaphragm 14 and the second diaphragm 16 each have a pressure-receiving surface that faces the outside, and the pressure-receiving surface is bent and deformed by receiving the pressure of the measured pressure environment, and is bent and deformed inside the housing 12. The stress which concerns on is transmitted. The first diaphragm 14 and the second diaphragm 16 are center regions 14a and 16a that are displaced by pressure from the outside, and a flexible portion 14b that is located at the outer periphery of the center regions 14a and 16a and bends and deforms by pressure from the outside. 16b and outer peripheral portions 14c and 16c which are on the outer periphery of the flexible portions 14b and 16b and are joined to the housing 12. A central region 14a inside the first diaphragm 14 is connected to one end 18a in the longitudinal direction of a pressure sensitive element 18 described later, and a central region 16a of the second diaphragm 16 is connected to a connecting member 22d of a second reaction force generating unit 22 described later. Connected. The material of the first diaphragm 14 and the second diaphragm 16 is preferably excellent in corrosion resistance, such as a metal such as stainless steel or ceramic, and may be a single crystal such as quartz or other non-crystalline material. When forming with a metal, you may form by pressing a metal base material. Further, if it is formed by using a photolithography technique and an etching technique (hereinafter referred to as photolithography etching process together), the generation of residual stress in the press working is suppressed, and a sensitive diaphragm is formed. Similarly, in the case of forming with quartz, it is preferable to form by photolithography / etching. The diaphragm may be coated on the surface exposed to the outside so as not to be corroded by liquid or gas. For example, a nickel diaphragm may be coated with a nickel compound, and if the diaphragm is a piezoelectric crystal such as quartz, silicon may be coated.

  The pressure sensitive element 18 is formed as a double tuning fork type piezoelectric vibrator, a SAW resonator, a thickness shear vibrator, or the like using a piezoelectric material such as quartz, lithium niobate, or lithium tantalate. The pressure sensitive element 18 is arranged so that its longitudinal direction is coaxial with the displacement directions of the first diaphragm 14 and the second diaphragm 16, and the displacement direction is used as a detection axis.

  The pressure-sensitive element 18 is electrically connected to the above-described oscillation circuit (not shown), and vibrates at an inherent resonance frequency by an alternating voltage supplied from the oscillation circuit (not shown). The pressure frequency of the pressure-sensitive element 18 fluctuates by receiving an elongation stress or a compressive stress from the longitudinal direction. In particular, the double tuning fork type piezoelectric resonator element has a very large change in resonance frequency with respect to elongation / compression stress and a wide variable range of resonance frequency compared to a thickness shear vibrator, etc., so it can be decomposed to detect a slight pressure difference. It is suitable for a pressure sensor that excels. When the double tuning fork type piezoelectric vibrator is subjected to an extension stress, the amplitude width of the vibrating arm (vibrating part) is reduced, so that the resonance frequency is increased. When the compressive stress is applied, the amplitude width of the vibrating arm (vibrating part) is increased. The resonance frequency is lowered. As the piezoelectric substrate of the double tuning fork type piezoelectric vibrator, quartz having excellent temperature characteristics is desirable.

  One end 18a in the longitudinal direction of the pressure-sensitive element 18 is connected to the central region 14a of the first diaphragm 14, and the other end 18b on the opposite side of the one end 18a is connected to a second reaction force generator 22 described later. In FIG. 1, the other end 18b and the second weight 30 are integrated. Further, the wiring 18 c on the one end 18 a side of the pressure sensitive element 18 extends to the action point 20 c side of the first reaction force generation unit 20. Therefore, the pressure-sensitive element 18 has the longitudinal direction as a detection axis, and the force detection direction and the displacement direction of the first diaphragm 14 (second diaphragm 16) have a coaxial relationship.

  The fixing portion 24 is a member fixed to the inner side (inner wall) at the center of the side surface of the housing 12, and the fixing portion 24 includes a first protrusion 24 a serving as a first fulcrum 20 a of a first reaction force generating portion 20 described later. , And a second protrusion 24b serving as a second fulcrum 22a of the second reaction force generator 22. By fixing the fixing portion 24 to the inner wall at the center of the side surface of the housing 12, even when the components inside the housing 12 including the fixing portion 24 and the material of the housing 12 are different, the pressure due to the temperature change caused by the difference in the linear expansion coefficient The measurement error can be reduced. Of course, if the housing 12 and the components inside the housing 12 are the same material, the fixing portion 24 does not need to be fixed to the center of the side surface of the housing 12. The fixed portion 24 is provided with a wiring 24c, and the wiring 24c extends from the first protruding portion 24a to the hermetic terminal 26 outside the connection position of the fixed portion 24 with the housing 12.

  The first reaction force generator 20 uses the first weight 28 to apply a force in the direction opposite to the direction of the force due to the weight of the first diaphragm 14 to the first diaphragm 14 according to the principle of leverage. The 1st reaction force generation part 20 is hold | maintained at the 1st projection part 24a by making the connection part with the 1st projection part 24a into the 1st fulcrum 20a. A first weight 28 is disposed at the first force point 20 b of the first reaction force generator 20. In FIG. 1, the first force point 20b and the first weight 28 are integrated. The first action point 20 c of the first reaction force generator 20 is connected to the central region 14 a inside the first diaphragm 14 or the one end 18 a of the pressure sensitive element 18. Note that the connection position between the first fulcrum 20a and the first protrusion 24a and the connection position between the first force point 20b and the first diaphragm 14 are designed to be narrow and movable to some extent. As a result, the first reaction force generating unit 20 can transmit the force direction from the first force point 20b to the first action point 20c by reversing the direction of the force from the first force point 20b with the first fulcrum 20a interposed therebetween, and the pressure sensitive element. It can suppress that 18 (1st diaphragm 14) receives the force of directions other than a detection-axis direction from the 1st reaction force production | generation part 20. FIG. The length of the first reaction force generator 20 on the first force point 20b side and the weight of the first weight 28 are the moment of inertia with respect to the first fulcrum 20a on the first force point 20b side and the first fulcrum on the first action point 20c side. Adjustment is made so that the moment of inertia relative to 20a is balanced. In the first reaction force generator 20, a wiring 20d is provided from the first action point 20c to the first fulcrum 20a. Therefore, the pressure sensitive element is electrically connected to an external oscillation circuit (not shown) through the conductive wirings 18c, 20d, and 24c. The wirings 18c, 20d, and 24c are also disposed on the back surfaces (not shown) of the one end 18a, the first reaction force generation unit 20, and the fixing unit 24, respectively.

  The second reaction force generator 22 uses the second weight 30 to apply a force in the direction opposite to the direction of the force due to the weight of the second diaphragm 16 to the second diaphragm 16 according to the principle of leverage. The second reaction force generation unit 22 includes a second weight 30 and a lever portion 22e connecting member 22d. The insulator 22e is held by the second protrusion 24b with the connection portion with the second protrusion 24b as a second fulcrum 22a. A second weight 30 is connected to the second force point 22b of the lever portion 22e, and a connection member 22d bent in a key shape is connected to the action point 22c of the lever portion 22e. Further, the connection member 22 d is connected to the central region 16 a of the second diaphragm 16. Therefore, the action point 22c of the lever portion 22e and the second diaphragm 16 are connected via the connection member 22d. In the second reaction force generator 22, the connection position between the second fulcrum 22a and the second protrusion 24b of the lever 22e, the connection position between the second action point 22c and the connection member 22d, the second force point 22b and the second weight. Each of the connection positions with 30 is designed to be narrow and movable to some extent. As a result, the second reaction force generator 22 (insulator 22e) can invert the direction of the force from the second force point 22b and transmit it to the second action point 22c by sandwiching the second fulcrum 22a. In addition, the second weight 30, that is, the pressure sensitive element 18 integrated with the second weight 30, can be prevented from receiving a force in a direction other than the detection axis direction from the second reaction force generator 22. The length of the second reaction force generator 22 on the second force point 22b side, the weight of the second weight 30, and the length from the second fulcrum 22a on the second action point 22c side are the first force point on the first force point 20b side. Adjustment is made so that the moment of inertia with respect to the fulcrum 22a and the moment of inertia with respect to the first fulcrum 20a on the first action point 22c side are balanced.

  When the pressure-sensitive element 18 (second weight 30), the first reaction force generation unit 20 (first weight 28), the second reaction force generation unit 22, and the fixing unit 24 are each formed of quartz, these are referred to as photolithographic It is preferable to manufacture as a single body by etching.

FIG. 2 shows a process diagram of the photolithographic etching process in the first embodiment.
When the pressure-sensitive element 18, the first reaction force generation unit 20, the second reaction force generation unit 22, and the fixing unit 24 are integrally formed by photolithography / etching, first, as shown in FIG. Prepare a mother substrate 32, [2] apply a positive photoresist 34 to the surface of the mother substrate 32, [3] a pressure sensitive element 18, a first reaction force generator 20, a second reaction force generator 22, Exposure is performed using a photomask 36 corresponding to the shape of the fixing portion 24, [4] the photoresist 34 is exposed, [5] development is performed, and the exposed photoresist 34a is removed. [6] a mother substrate 32 is provided. The exposed region is etched until it penetrates the mother substrate 32 to form the pressure sensitive element 18, the first reaction force generation unit 20, the second reaction force generation unit 22, and the fixing unit 24. [7] The photoresist 34 is formed. Peeling, and so on 1] it goes through to [7] becomes process.

  Then, in a state where the pressure sensitive element 18, the first reaction force generation unit 20, the second reaction force generation unit 22, and the fixing unit 24 are integrated, the fixing unit is fixed to the inner wall of the housing 12, and the opening 12 a of the housing 12 is formed. It connects with the peripheral part 14c of the 1st diaphragm 14, joins the center area | region 14a and the one end 18a of the pressure-sensitive element 18, connects the opening part 12b with the peripheral part 16c of the 2nd diaphragm 16, and the center area | region 16a is made into 2nd reaction. It connects with the connection member 22d of the force generation part 22. Finally, the pressure sensor 10 according to the first embodiment is constructed by sucking air from the vacuum sealing hole 12c formed in the housing 12 and sealing it.

  When the pressure sensor 10 constructed in this way is viewed directly, the diaphragms (first diaphragm 14 and second diaphragm 16) that seal the openings (opening 12 a and opening 12 b) at both ends of the cylindrical housing 12. A pressure sensor 10 having a detection axis as a detection axis and both ends in the longitudinal direction connected to the diaphragm (one end connected via the second reaction force generator 22). And a reaction force generation unit (first reaction force generation unit 20 and second reaction force generation unit 22) that is connected to the diaphragm and applies a force in a direction opposite to the gravity that the diaphragm receives on the basis of the principle of leverage. It can be seen as a pressure sensor 10. As a result, the diaphragm receives a force from the reaction force generating portion in the opposite direction to the gravity received by the diaphragm, so that the displacement of the diaphragm due to the gravity is reduced, and accordingly, the stress to the pressure sensitive element due to the displacement is also reduced. Is done. Therefore, it can be understood that the pressure sensor 10 has a reduced pressure error due to gravity.

  In the pressure sensor 10 according to the first embodiment, the pressure-sensitive element 18 is pressed in the direction pushed out from the first diaphragm 14 by the pressure received by the first diaphragm 14, and the pressure-sensitive element is generated by the pressure received by the second diaphragm 16. A force is applied in the direction in which 18 is attracted to the second diaphragm 16. Therefore, when the force applied to the pressure sensitive element 18 by the first diaphragm and the second diaphragm is the same, the pressure sensitive element 18 does not receive any stress although its position moves. When the pressure on the first diaphragm 14 side is high, compressive stress is applied to the pressure sensitive element 18, and when the pressure on the second diaphragm 16 side is high, extension stress is applied to the pressure sensitive element 18. Therefore, the pressure sensor 10 according to the first embodiment can measure the relative pressure for detecting the pressure difference between the first diaphragm 14 and the second diaphragm 16. Further, since the detection axis of the pressure-sensitive element 18 and the displacement directions of the first diaphragm 14 and the second diaphragm 16 are coaxially arranged, the pressure difference between the first diaphragm 14 and the second diaphragm 16 can be accurately measured.

  By the way, when the first diaphragm 14 side is up and the second diaphragm 16 side is down, the first diaphragm 14 is displaced to the inside of the housing 12 by its own weight, and the second diaphragm 16 is outside the diaphragm 12 by its own weight. When the first diaphragm 14 side is down and the second diaphragm 16 side is up, the first diaphragm 14 is displaced to the outside of the housing 12 by its own weight, and the second diaphragm 16 is housing by its own weight. 12 seems to be displaced inward.

  However, the first weight 28 is always balanced by applying a force in the opposite direction to the combined force of the bending deformation stress received by the first diaphragm 14 and the gravity received by the pressure-sensitive element 18, and the second weight 30 is In order to balance the resultant force obtained by subtracting the gravity received by the pressure-sensitive element 18 from the stress of the bending deformation caused by the gravity received by the second diaphragm 16, the first diaphragm 14 and the second diaphragm 16 are balanced. The displacement due to the gravitational force received by the first diaphragm 14 and the second diaphragm 16 is canceled by the pressure-sensitive element 18. Therefore, the pressure-sensitive element 18 detects only the pressure difference between the first diaphragm 14 and the second diaphragm 16 and becomes the pressure sensor 10 in which the change in the method of applying gravitational acceleration and the influence of vibrations generated thereby are reduced.

  FIG. 3 shows a pressure sensor 40 according to the second embodiment. The pressure sensor 40 according to the second embodiment has a configuration in which a pair of the first reaction force generation unit 20 (first weight 28) and the second reaction force generation unit 22 in the first embodiment are formed. Along with this, a pair of fixing portions 24 are also formed. The first reaction force generation units 20 and 42, the second reaction force generation units 22 and 44, and the fixing units 24 and 46 are symmetrically formed with the pressure sensitive element 18 interposed therebetween.

  The fixing portion 46 is disposed symmetrically with the fixing portion 24 with the longitudinal direction of the pressure-sensitive element 18 as the center line, and is connected to the inner wall of the central portion of the side surface of the housing 12 to form a first protrusion 46a and a second protrusion 46b. . The first protrusion 46 a is connected to the first fulcrum 42 a of the first reaction force generator 42, and the second protrusion 46 b is connected to the second fulcrum 44 a of the lever part 44 f of the second reaction force generator 44.

  The first reaction force generator 42 is arranged symmetrically with the first reaction force generator 20 with the longitudinal direction of the pressure sensitive element 18 as the center line. A first weight 54 is disposed at the first force point 42b of the first reaction force generator 42, and the first force point 42b and the first weight 54 are integrated. The action point 42 c of the first reaction force generator 42 is connected to one end 18 a of the pressure sensitive element 18.

  The second reaction force generation unit 44 is arranged symmetrically with the second reaction force generation unit 22 with the longitudinal direction of the pressure sensitive element 18 as a center line. Similar to the second reaction force generation unit 22, the second reaction force generation unit 44 includes a second weight 44e, a lever portion 44f, and a connection member 44d. Connected.

  A second weight 44e is disposed at the second force point 44b of the lever portion 44f of the second reaction force generation unit 44, and the second force point 44b and the second weight 44e are integrated. Further, the second weight 44 e is integrated with the second weight 30. A connection member 44d having a key shape is connected to the action point 44c of the lever portion 44f. The connection member 44d is connected to the central region 16a of the second diaphragm 16 and is integrated with the connection member 22d.

  The first reaction force generation unit 42 (first weight 54), the second reaction force generation unit 44, and the fixing unit 46 include the pressure sensitive element 18 (second weights 30, 44e) and the first reaction force generation unit 20 (first reaction force generation unit 20). Since the first weight 28), the second reaction force generating portion 22, and the fixing portion 24 are formed on the same plane, it is preferable to integrally form them by photolithography and etching.

4 and 5 show process diagrams of photolithography / etching in the second embodiment.
When the pressure sensitive element 18, the first reaction force generation units 20 and 42, the second reaction force generation units 22 and 44, and the fixing units 24 and 46 are integrally formed by photolithography and etching, as shown in FIG. 1) Prepare a mother substrate 48 as a material, [2] Apply a positive photoresist 50 on the surface of the mother substrate 48, [3] Pressure-sensitive element 18, first reaction force generators 20, 42, first 2 Exposure is performed using a photomask 52 corresponding to the shapes of the reaction force generation units 22 and 44 and the fixing units 24 and 46, [4] the photoresist 48 is exposed, and [5] development and exposure of the photoresist 50a. [6] The region where the mother substrate 48 is exposed is etched until it penetrates the mother substrate 48, whereby the pressure-sensitive element 18, the first reaction force generators 20, 42, and the second reaction force generators 22, 44 are removed. Forming the fixing parts 24, 46, [ ] Peeling the photoresist 50, the process and so [1] - goes through [7] becomes processes. Hereinafter, the pressure sensor 40 according to the second embodiment is constructed through a process similar to that of the first embodiment. In the first embodiment, the wirings 18c, 20d, and 24c are formed on the front and back surfaces of the pressure sensitive element 18, the first reaction force generating unit 20, and the fixing unit 24, and the two wirings are connected to the outside from the pressure sensitive element 18. However, in the second embodiment, two wirings are formed on the same surface as shown by a broken line in FIG. 2, and one is wired from the pressure sensitive element through the first reaction force generation unit 42 and the fixing unit 46. Then, the hermetic terminal 26 may be attached to the opposite side of the connecting portion between the fixed portion 46 and the housing 12 and electrically connected to the outside.

  In the pressure sensor 40 according to the second embodiment, another first weight 52 is arranged at a symmetrical position with respect to the first weight 28 not on the detection axis of the pressure sensitive element 18 with the pressure sensitive element 18 interposed therebetween. Therefore, the gravity balance on the first diaphragm 14 side is maintained, and the inclination angle dependency of the measurement error of the pressure sensor 40 is improved. Furthermore, since the stresses other than the direction of the detection axis applied to the pressure sensitive element 18 by the pair of first reaction force generation units 20 and 42 are canceled out, the pressure sensor 40 is more highly accurate. Further, since the force in the direction other than the detection axis direction applied to the pressure sensitive element 18 by the pair of second reaction force generation units 22 and 44 is also canceled, the pressure sensor 40 is more highly accurate. By providing a pair of the first reaction force generators 20 and 42 and the second reaction force generators 22 and 44 in this way, the pressure sensitive element 18 hardly receives a force in a direction other than the detection axis direction, so that it has extremely high accuracy. A simple pressure sensor 40 can be constructed.

  FIG. 6 shows a modification of the first embodiment and the second embodiment. FIG. 6A shows a modification of the first embodiment, and FIG. 6B shows a modification of the second embodiment. In the pressure sensors 10 and 40 according to the first embodiment and the second embodiment, the second weights 30 and 44e are configured to be integrated with the pressure-sensitive element 18, but in the same manner as the first weights 28 and 54, A configuration separated from the pressure element 18 can be adopted.

  6A, the fixing portion 60 is fixed to the inner wall of the central portion of the side surface of the housing 12, and is formed in a symmetrical shape between the first reaction force generation portion 20 and the second reaction force generation portion 58. A first protrusion 60a and a second protrusion 60b are formed. The first protrusion 60 a is connected to the first fulcrum 20 a of the first reaction force generator 20, and the second protrusion 60 b is connected to the second fulcrum 58 a of the second reaction force generator 58.

A first weight 28 is disposed at the first force point 20b of the first reaction force generator 20, and the first force point 20b and the first weight 28 are integrated. The action point 20 c of the first reaction force generator 20 is connected to one end 18 a of the pressure sensitive element 18.
A second weight 62 is disposed at the second force point 58b of the second reaction force generator 58, and the second force point 58b and the second weight 62 are integrated. The action point 58 c of the second reaction force generator 58 is connected to the other end 18 b of the pressure sensitive element 18.

  In FIG. 6B, the fixing portion 66 is connected to the inner wall of the central portion of the side surface of the housing 12 in a symmetrical arrangement with the fixing portion 60 with the pressure sensitive element 18 as the center line. A first protrusion 66 a and a second protrusion 66 b are formed on the fixing portion 66. The first protrusion 66 a is connected to the first fulcrum 42 a of the first reaction force generator 42, and the second protrusion 66 b is connected to the second fulcrum 64 a of the second reaction force generator 64.

  The first reaction force generation unit 42 is arranged symmetrically with the first reaction force generation unit 20 with the longitudinal direction of the pressure sensitive element 18 as the center line. A first weight 54 is disposed at the first force point 42b of the first reaction force generator 42, and the first force point 42b and the first weight 54 are integrated. The action point 42 c of the first reaction force generator 42 is connected to one end 18 a of the pressure sensitive element 18.

  The second reaction force generator 66 is disposed symmetrically with the second reaction force generator 58 with the longitudinal direction of the pressure sensitive element 18 as the center line. A second weight 68 is disposed at the second force point 66b of the second reaction force generator 66, and the second force point 66b and the second weight 68 are integrated. The action point 66 c of the second reaction force generator 66 is connected to the other end 18 b of the pressure sensitive element 18.

  The other end 18 b of the pressure sensitive element 18 is connected to the central region 16 a of the second diaphragm 16. The first action point 20c and the first action point 42c are connected to the center area 14a of the first diaphragm 14, and the second action point 58c and the second action point 66c are connected to the center area 16a of the second diaphragm 16. You may comprise.

With this configuration, the pressure sensors 10 and 40 according to the modification of the first embodiment and the second embodiment seal the openings (opening 12a and opening 12b) at both ends of the cylindrical housing 12. Pressure sensors 10 and 40 having diaphragms to be stopped (first diaphragm 14 and second diaphragm 16) and pressure-sensitive elements 18 having the detection direction of force as a detection axis and both ends in the longitudinal direction connected to the diaphragm. The reaction force generators (first reaction force generators 20, 42, second reaction force generators 58, 58) that are connected to the diaphragm and apply a force in the opposite direction to the gravity that the diaphragm receives on the principle of the lever. 66). In addition, since the manufacturing method of the said modification is the same as that of 1st Embodiment and 2nd Embodiment, respectively, description is abbreviate | omitted.
The effect according to the modified example of FIG. 6A is basically the same as that of the first embodiment, and the effect according to the modified example of FIG. 6B is basically the same as that of the second embodiment.

  In the first embodiment and the second embodiment, as shown in FIGS. 1, 3 and 6, the surface of the first weights 28 and 54 and the second weights 30, 44e, 62 and 68 is made of a metal such as Au. A membrane 56 can be provided. The metal film 56 of Au or the like can be formed by sputtering on a mask (not shown) corresponding to the shape of the surface of the first weights 28 and 52 and the second weights 30 and 44e. At this time, the metal film 56 may be disposed on one side or both sides of the first weights 28 and 54 and the second weights 30 and 44e.

  As a result, the metal film 56 is disposed after the construction of the first weights 28 and 54 and the second weights 30, 44 e, 62 and 68, so the weights on the first weight side and the second weight side are adjusted. As the opportunity increases, the weights of the first weight side and the second weight side are finely adjusted by disposing an appropriate amount of the metal film 56, and the first diaphragm 14 and the second diaphragm 16 are deformed by gravity. It is possible to reduce the stress applied to the pressure sensitive element due to the above.

  Further, the metal film 56 can be peeled off by irradiation with a laser or the like. Therefore, when the pressure sensors 10 and 40 are entirely made of a material that transmits laser light, such as quartz, the first weights 28 and 54 and the second weights 30 and 44e even after the pressure sensors 10 and 40 are constructed. , 62, 68 can be finely adjusted, and the yield of the pressure sensors 10, 40 is improved.

1 is a schematic diagram of a pressure sensor according to a first embodiment. It is process drawing of the photolitho etching process in 1st Embodiment. It is a schematic diagram of the pressure sensor which concerns on 2nd Embodiment. It is process drawing of the photolithography etching process in 2nd Embodiment. It is process drawing of the photolithography etching process in 2nd Embodiment. It is a schematic diagram which shows the modification of 1st Embodiment and 2nd Embodiment. It is a schematic diagram of the pressure sensor which concerns on a 1st prior art. It is a schematic diagram of the pressure sensor which concerns on a 2nd prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ......... Pressure sensor, 12 ......... Housing, 14 ......... 1st diaphragm, 16 ......... 2nd diaphragm, 18 ......... Pressure sensitive element, 20 ...... 1st reaction force production | generation part, 22 ... …… Second reaction force generator 24 …… Fixed part 26 ...... Hermetic terminal 28 …… First weight 30 …… Second weight 32 …… Mother substrate 34 …… Photoresist 36... Photomask 40... Pressure sensor 42... First reaction force generator 44... Second reaction force generator 46. Mother substrate, 50... Photoresist, 52... Photomask, 54... First weight, 56... Metal film, 58. 62 ......... Second weight, 64 ......... Second reaction force generating portion, 66 ......... Fixed portion, 68 ......... Second weight 101 ......... Pressure sensor, 102 ......... Pressure input port, 103 ......... Pressure input port, 104 ...... Case, 105 ...... Force transmitting means, 106 ...... First bellows, 107 ......... Second bellows, 108 ...... Substrate, 109 ...... Double tuning fork vibrator, 110 ......... Oil, 111 ......... Opening, 121 ......... Pressure sensor, 122 ...... Double tuning fork Resonator, 123... Quartz diaphragm, 124... Recess, 125... Internal bottom surface, 126... Force transmission column, 128.

Claims (7)

A diaphragm that seals the openings at both ends of the cylindrical housing;
A pressure sensor having a detection direction of force as a detection axis and a pressure sensitive element having both ends in the longitudinal direction connected to the diaphragm,
A pressure sensor, comprising: a reaction force generating unit that is connected to the diaphragm and applies a force on the diaphragm in a direction opposite to the gravity that the diaphragm receives according to the principle of an insulator. A cylindrical housing;
A first diaphragm and a second diaphragm for sealing the openings at both ends of the housing;
A first reaction force generator connected to the first diaphragm and applying a force in a direction opposite to the gravity applied to the first diaphragm on the first diaphragm by the principle of an insulator using a first weight;
A second reaction force generator connected to the second diaphragm and applying a force in the direction opposite to the gravity applied to the second diaphragm on the second diaphragm according to the principle of lever by using a second weight;
A pressure sensor, which is disposed inside the housing, includes a pressure sensing element having a detection direction as a force detection axis, one end connected to the first diaphragm, and the other end connected to the second weight. .   The pressure sensor according to claim 2, wherein the first reaction force generation unit is formed in a pair with the pressure sensitive element interposed therebetween.   4. The pressure sensor according to claim 2, wherein the second reaction force generation unit is formed in a pair with the pressure sensitive element interposed therebetween.   The first reaction force generation part and the second reaction force generation part are fixed to the housing via a fixing part fixed to the housing, and the fixing part is fixed to the center of the side surface of the housing. The pressure sensor according to any one of claims 2 to 4, wherein the pressure sensor is provided.   6. The pressure sensor according to claim 2, wherein a metal film is disposed on at least one surface of the first weight and the second weight. 7.   The pressure sensor according to claim 6, wherein a part or all of the metal film can be peeled off.