Sensing device

Abstract

To provide a technique for reducing the size of a sensing device.SOLUTION: A sensing device adsorbs sensed substance as gas onto a piezoelectric oscillator and senses the sensed substance on the basis of change in oscillation frequency of the piezoelectric oscillator. The sensing device includes a base body provided with a first recess for storing an area of a Peltier element section on heat exhausting side and a second recess for storing a circuit board with a division plate interposed therebetween. A sensor substrate holding the piezoelectric oscillator is provided on and in contact with a temperature-controlling surface of the Peltier element section. An oscillation circuit oscillating the piezoelectric oscillator is mounted and a connector for external connection is surface-mounted on the circuit board. The connector connects a side face of an area of the base body where the second recess is formed to the outside. The connector is provided so as to be connected from the side face of the sensing device to the outside, thus reducing the size of the sensing device.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a sensing device that senses a substance to be sensed by a change in frequency of a piezoelectric vibrator. [Background technology]

[0002] Quartz crystal microbalances (QCMs) using quartz crystal oscillators are known as sensing devices for detecting substances contained in gases. One of the methods for analyzing substances using such QCMs is to attach a gas to a quartz crystal oscillator, then gradually increase the temperature of the quartz crystal oscillator from a low temperature to desorb the gas attached to the quartz crystal oscillator.

[0003] This method is a type of thermogravimetry, in which the amount of gas attached is obtained by measuring the change in frequency before and after gas desorption, and the gas components are identified by detecting the temperature at which the gas desorbs.Analytical devices with built-in Peltier elements for actively changing the temperature of the above-mentioned quartz crystal oscillator are known, and sensing devices that combine a QCM with a temperature control means for desorbing gas in this way are also called TQCMs (Thermoelectric QCMs) (for example, Patent Document 2, described below). Such TQCMs are equipped with temperature control units and quartz oscillator circuits, and as a result, their structure is becoming more complex and larger, and there is a demand for miniaturization.

[0004] Patent Document 1 describes a configuration in which a quartz crystal oscillator sensor, a Peltier element, and a heat transfer material are stacked in this order from above. Patent Document 2 describes a configuration in which a substrate equipped with a piezoelectric oscillator, a thermoelectric element unit, and a support plate are integrated and detachably mounted on a base unit. However, Patent Documents 1 and 2 do not focus on miniaturization and do not disclose a configuration that solves the problems of the present invention. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-257394 [Patent Document 2] Japanese Patent Publication No. 2020-193846 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in light of the above circumstances, and aims to provide a technique for miniaturizing a sensing device. [Means for solving the problem]

[0007] The present disclosure provides: A sensing device that adsorbs a gaseous substance to be sensed onto a piezoelectric vibrator, changes the temperature of the piezoelectric vibrator to desorb the substance, and senses the substance based on the relationship between the change in oscillation frequency of the piezoelectric vibrator and the temperature, a sensor substrate that holds the piezoelectric vibrator; a Peltier element unit that is in contact with the sensor substrate and includes a temperature control surface for changing the temperature of the piezoelectric vibrator and a heat dissipation surface on the opposite side of the temperature control surface; a circuit board on which an oscillation circuit is mounted, the oscillation circuit being electrically connected to the piezoelectric vibrator and causing the piezoelectric vibrator to oscillate, and on which a connector for connecting to an external device is surface-mounted; a base body having a first recess for accommodating an area of ​​the Peltier element portion on the heat dissipation surface side and a second recess for accommodating the circuit board, with a partition plate sandwiched between them; a cover body that houses the base body in a region where the first recess is formed, the Peltier element portion protruding outside the first recess, and the sensor substrate, and has an opening formed in it corresponding to an arrangement region of the piezoelectric vibrator that adsorbs the substance to be sensed; a base cover that covers the second recess, The connector is characterized in that connection to the outside is made from the side surface of the region of the base body where the second recess is formed. [Effects of the Invention]

[0008] According to the present disclosure, in a sensing device that senses a substance to be sensed that has been adsorbed to a piezoelectric vibrator based on changes in the oscillation frequency of the piezoelectric vibrator, a connector for connecting to the outside is surface-mounted on a circuit board on which an oscillation circuit that oscillates the piezoelectric vibrator is mounted. This circuit board is housed in a second recess in a base body, and the connector is provided so as to be connected to the outside from the side of the sensing device, thereby enabling the sensing device to be made smaller. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 10 is a vertical cross-sectional side view showing a sensing device of a comparative example. [Figure 2] FIG. 10 is a perspective view showing the appearance of a sensing device of a comparative example. [Figure 3] 1 is a vertical cross-sectional side view showing a sensing device according to an embodiment of the present invention. [Figure 4] 1 is an exploded perspective view showing a sensing device according to an embodiment of the present invention; [Figure 5] 1 is a perspective view showing an external appearance of a sensing device according to an embodiment of the present invention; [Figure 6] 1 is a vertical cross-sectional side view showing an example of a sensing system provided with a sensing device of the present invention. [Figure 7] FIG. 10 is a vertical cross-sectional side view showing another example of the sensing device of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention relates to a sensing device that is a TQCM, and aims to reduce the size of the sensing device. Therefore, prior to describing the present invention, a brief description of the configuration of a conventional sensing device will be given as a comparative example. <Comparative form> Fig. 1 is a longitudinal side view of a comparative example of a sensing device 11, and Fig. 2 is a perspective view of its exterior. The sensing device 11 shown in these figures has a base part 12 consisting of a base main body 121 and a back cover part 122. The base main body 121 is made up of a block that is circular in plan view, and has a protrusion part 123 that is also circular in plan view in the center of its upper surface.

[0011] A disk-shaped Peltier base 130 is provided on the upper surface of the base portion 12, and the Peltier element portion 13 is disposed on this Peltier base 130. The Peltier base 130 is formed with a recess (not shown) for positioning the Peltier element portion 13. Furthermore, a sensor substrate 15 having a quartz oscillator 14 is provided on the upper surface side of the Peltier element portion 13. The quartz oscillator 14 has excitation electrodes 141, 142 on both sides thereof and is electrically connected to an oscillation circuit 17 (described later) via a conductive pin 151. The Peltier element portion 13 adjusts the temperature of the quartz oscillator 14, and in this example, rectangular Peltier elements 131, 132 of different sizes are stacked in two layers.

[0012] A cover 16 is provided on the outside of the protrusion 123 on the base body 121 so as to cover the Peltier element part 13 and the sensor substrate 15 from above. This cover 16 is formed in a cylindrical shape that is open at the bottom, and its lower end is attached to the top surface of the base body 121. An opening 161 is formed in the cover 16 to supply gas, which is the substance to be sensed, to the excitation electrode 141 provided on the top surface of the quartz crystal oscillator 14.

[0013] A space 124 is formed inside the base body 121 and the protrusion 123, and a circuit board 18 equipped with an oscillator circuit 17 is housed in this space 124. The oscillator circuits 17 are arranged on both the upper and lower surfaces of the circuit board 18 so as to face each other. The height of the space 124 is greater than the height of the circuit board 18 including the upper and lower oscillator circuits 17. For example, a gap of approximately 5 mm is formed between the top surface of the upper oscillator circuit 17 and the ceiling surface of the space 124. The lower side of the circuit board 18 is closed by the back cover 122 of the base part 12.

[0014] A connector cover 191, which has a horizontally flat housing shape and protrudes downward, is provided on the underside of the back cover 122. A connector 19 for electrically connecting the circuit board 18 to the outside is housed inside this connector cover 191. By connecting the connector 19 to an external power supply, the oscillator circuit 17 and the crystal unit 14 are electrically connected to the outside. Note that components such as the crystal unit 4 and the oscillator circuit 17 that are also provided in the sensing device 1 of the present invention will be described later.

[0015] In this example, a connector 19 is provided so as to protrude downward from the sensing device 11, and the space 124 accommodating the oscillator circuit 17 has a large distance set between the upper surface of the upper oscillator circuit 17 and a ceiling surface 125 of the space 124, and the inside of the base part 12 has a relatively large space above the circuit board 18. Furthermore, the Peltier element part 13 is provided in the base part 12 via a Peltier base 130, so the sensing device 11 has a large configuration in the vertical direction. To give an example of the size of such a sensing device 11, the diameter L11 of the base portion 12 is, for example, 35 mm, and the height L12 from the bottom end of the connector 19 to the top end of the cover 16 is, for example, 37.25 mm.

[0016] Next, an embodiment of a sensing device 1, which is a TQCM of the present invention, will be described with reference to FIGS. 3 to 5. In sensing device 1, a Peltier element unit 3 and a sensor substrate 5 holding a quartz crystal oscillator 4, which is a piezoelectric oscillator, are stacked on the upper surface of a base body 2, and a circuit board 6 is disposed in a space formed on the lower surface of the base body 2. However, this sensing device 1 differs from comparative sensing device 11 in that a connector 7 is directly surface-mounted on the circuit board 6 and configured to be connected to an external device. In FIGS. 3 to 5, the left-right direction as viewed in the drawing is defined as the X direction, the front-back direction as the Y direction, and the up-down direction as the Z direction. Regarding the left-right direction, the right side of the paper in FIG. 3 will be described as one end and the left side as the other end.

[0017] Each part of the sensing device 1 will be described in detail below. As shown in Figures 3 and 4, the base body 2 is configured by providing a protrusion 23 that is circular in plan view in the center of one surface (upper surface) of a lower member 22 that is rectangular in plan view. The base body 2 including the lower member 22 is made of, for example, nickel-plated copper to ensure high thermal conductivity.

[0018] A first recess 24 having a generally rectangular shape in plan view is provided on the upper surface side of the protruding portion 23. When the base body 2 is viewed from above, the first recess 24 is formed in the center of the protruding portion 23. A bottom 241 of the first recess 24 is configured as a flat surface, and holes 242 for inserting pins 53, which will be described later, are formed in the bottom 241. Each hole 242 is formed to correspond to the arrangement position of the pin 53 (see FIG. 4).

[0019] On the other hand, a second recess 25 is formed on the other surface (lower surface) of the lower member 22. As shown in Fig. 3, in the lower member 22, the second recess 25 is formed from the region directly below the first recess 24 to the side surface 27 on one end side when the base body 2 is viewed in the left-right direction.

[0020] The height dimension of the second recess 25 is formed so that the second region 252 closer to the side surface 27 is larger than the height dimension of the first region 251 directly below the first recess 24. As will be described later, the oscillator circuits 61 and 62 are disposed in the first region 251, and the connector 7 is disposed in the second region 252. A ceiling surface 253 of the first region 251 and a ceiling surface 254 of the second region 252 are each configured as a flat surface.

[0021] 3, the first recess 24 and the second recess 25, which are arranged opposite each other vertically, are separated by a partition plate 26. The upper surface of the partition plate 26 forms the bottom 241 of the first recess 24, and the lower surface of the partition plate 26 forms the ceiling surface of the second recess 25 (ceiling surface 253 in the first region 251, and ceiling surface 254 in the second region 252). As described above, the partition plate 26 is formed with a thickness that varies from the first region 251 to the second region 252. For example, the thickness L1 of the partition plate in the first region 251 is set to, for example, 3 mm within a range of 3 to 5 mm. Furthermore, an opening 271 communicating with the second recess 25 is formed on the side surface 27 of the base body 2. This opening 271, in combination with the base cover 21 described below, forms the opening 20 for connecting the connector 7 to the outside.

[0022] A Peltier element unit 3 is provided in the first recess 24. The Peltier element unit 3 is configured, for example, by stacking two Peltier elements, one large and one small, in the shape of small pieces that are angular in plan view, one above the other. The top and bottom surfaces of the Peltier element unit 3 are flat, and the Peltier element unit 3 is provided in the first recess 24 so that its bottom surface contacts the top surface of the partition plate 26 (bottom 241 of the first recess 24). The Peltier element unit 3 is also set smaller than the sensor substrate 5 in plan view, and is provided so that the top surface of the Peltier element unit 3 contacts the center of the bottom surface of the sensor substrate 5.

[0023] The Peltier element unit 3 has a surface (upper surface) that contacts the sensor substrate 5 as a temperature control surface 31 for changing the temperature of the quartz crystal oscillator 4, and a surface (lower surface) opposite the temperature control surface 31 as a heat release surface 32. In this example, the upper surface of the upper stage of the Peltier element unit 3 is configured as the temperature control surface 31, and the lower surface of the lower stage is configured as the heat release surface 32. The entire lower stage of the Peltier element unit 3 is configured as a region on the heat release surface side, and this region is housed in, for example, the first recess 24. As shown in FIG. 3 , the height dimension of the Peltier element unit 3 is formed to be greater than the height dimension of the protrusion 23 (first recess 24). Therefore, the entire upper stage side of the Peltier element unit 3 protrudes outward from the first recess 24, with the temperature control surface 31 in contact with the sensor substrate 5.

[0024] By switching the direction of the current supplied to the Peltier element unit 3, the temperature control surface 31 can be switched between a heating surface and a cooling surface, thereby changing the temperature of the quartz crystal unit 4 via the sensor substrate 5. In other words, when cooling the sensor substrate 5, the temperature control surface 31 of the Peltier element unit 3 becomes the cooling surface, and its heat exhaust surface 32 becomes the heating surface. When heating the sensor substrate 5, the temperature control surface 31 of the Peltier element unit 3 becomes the heating surface, and its heat exhaust surface 32 becomes the cooling surface. In this way, the Peltier element unit 3 is configured to be able to change the temperature of the quartz crystal unit 4 within a range of, for example, -80°C to 125°C.

[0025] The sensor substrate 5 is made of, for example, LTCC (Low Temperature Co-fired Ceramics) and is formed in a generally rectangular shape in a plan view. The upper surface of the sensor substrate 5 is provided with a recess 51, and the peripheral edge of the quartz crystal unit 4 is supported by the opening edge of the recess 51. The quartz crystal unit 4 supported by the opening edge is disposed in the center of the sensor substrate 5. In addition, a temperature detection unit 52 for detecting the temperature of the quartz crystal unit 4 is provided on the upper surface of the sensor substrate 5. Note that for convenience of illustration, the temperature detection unit 52 is depicted in different positions in FIGS. 3 and 4.

[0026] The quartz crystal unit 4 includes a disk-shaped quartz crystal blank 40, which is, for example, an AT-cut piezoelectric piece. A first excitation electrode 41 and a second excitation electrode 42, each made of, for example, gold (Au), are arranged on the upper surface of the quartz crystal blank 40, spaced apart from each other in the left-right direction, as shown in FIGS. 3 and 4. The first excitation electrode 41 is a reaction electrode that adsorbs the substance to be sensed, and the second excitation electrode 42 is a reference electrode. A third excitation electrode 43 is provided on the lower surface of the quartz crystal blank 40 in an area facing the first and second excitation electrodes 41 and 42.

[0027] One end of each of the extraction electrodes 441 and 442 is connected to the first and second excitation electrodes 41 and 42, respectively. These extraction electrodes 441 and 442, the extraction electrode (not shown) of the third excitation electrode 43, and the temperature detection unit 52 are each electrically connected to the upper ends of a plurality of pins 53, which are rod-shaped conductive members, via wiring patterns and conductive members (not shown) provided on the sensor substrate 5.

[0028] As shown in Fig. 4, a plurality of these pins 53, for example, four pins on each side in the front-rear direction of the sensor substrate 5, are provided and arranged in the left-right direction. Each pin 53 is provided so as to extend vertically downward from the underside of the sensor substrate 5. As described above, the Peltier element section 3 is formed smaller than the sensor substrate 5 in a plan view. Therefore, the pins 53 extend further downward through the outer region of the Peltier element section 3 without interfering with it. The pins 53 are provided so as to extend further downward through the hole 242 formed in the bottom 241 of the first recess 24.

[0029] The base body 2 and the Peltier element unit 3 are bonded together by, for example, a metal nanoparticle paste such as silver nanoparticle paste at the lower surface (heat dissipation surface) 32 of the Peltier element unit 3 and the bottom 241 of the first recess 24. The upper surface (temperature control surface) 31 of the Peltier element unit 3 and the lower surface of the sensor substrate 5 are also fixed together by, for example, the metal nanoparticle paste.

[0030] The base body 2 on which the sensor substrate 5 is provided via the Peltier element section 3 in this manner is covered from above by the cover body 8 in the area where the first recess 24 is formed, and the Peltier element section 3 protruding outside the first recess 24 and the sensor substrate 5 are housed in the cover body 8. The cover body 8 is configured as an upright cylinder with a ceiling, and after the Peltier element section 3 and the sensor substrate 5 are attached to the base body 2, the lower end of the cover body 8 is attached to the base body 2 so as to surround the periphery of the sensor substrate 5 and the side peripheral surface of the protruding section 23.

[0031] The ceiling portion 81 of the cover body 8 is configured as a flat surface, and an opening 82 that is circular in plan view is formed in this ceiling portion 81. This opening 82 is provided at a position corresponding to the first excitation electrode 41 of the quartz oscillator 4, and is configured so that the substance to be sensed, which is a gas, can be introduced toward the excitation electrode 41. In this example, the first excitation electrode 41 is a reaction electrode, and therefore the region where the first excitation electrode 41 is formed corresponds to the arrangement region of the piezoelectric oscillator (quartz oscillator) 4 that adsorbs the substance to be sensed.

[0032] The edge of the opening 82 of the cover body 8 extends downward to form a cylindrical guide 83 whose opening diameter gradually decreases downward. For example, the lower end of the guide 83 is provided so as to be slightly spaced, for example, by 0.5 mm, from the surface of the quartz crystal unit 4. The cover body 8 in this example also includes a cylindrical wall portion 84 that forms a space surrounding the periphery of the second excitation electrode 42, and the lower end of this wall portion 84 is also provided so as to be slightly spaced from the surface of the quartz crystal unit 4.

[0033] Next, the structure of the lower side of the base body 2 in the sensing device 1 will be described. A circuit board 6 is housed in the second recess 25 of the base body 2. The circuit board 6 is a horizontal plate-like body, and is arranged across the first region 251 and the second region 252 of the second recess 25. In the region on the other end side (the left side when facing FIG. 3) of the circuit board 6 as viewed in the left-right direction, oscillator circuits 61 and 62 are provided on the upper and lower surfaces of the circuit board 6, respectively. The oscillator circuits 61 and 62 are constituted by integrated circuits (ICs), which are silicon semiconductor elements, and are configured to be connected to the quartz crystal oscillator 4 to cause the quartz crystal oscillator 4 to oscillate.

[0034] These oscillator circuits 61, 62 are arranged in the first area 251 so as to face the Peltier element unit 3, for example, with the partition plate 26 interposed therebetween. The circuit board 6 is housed in the second recess 25 so that the upper surface of the upper oscillator circuit 61 is spaced apart from the partition plate 26. If priority is given solely to miniaturizing the sensing device 1, it may be possible to have the oscillator circuit 61 in contact with the partition plate 26. However, in order to suppress the effect of exhaust heat from the Peltier element unit 3, it is preferable to arrange the oscillator circuit 61 at a distance from the partition plate.

[0035] On the other hand, the thickness L1 of the partition plate of the first region 251 is set to, for example, 3 mm, which is larger than the thickness of the second region 252. Therefore, compared to when the partition plate 26 is uniformly formed to the same thickness as the second region 252, the influence of the exhaust heat from the Peltier element unit 3 is less likely to be transmitted downward. On the other hand, from the viewpoint of preventing the size of the sensing device 1 from increasing, it is difficult to ensure a gap of 5 mm as in the sensing device 11 according to the comparative embodiment. In the embodiment, the separation distance L2 between the top surface of the upper oscillation circuit 61 and the bottom surface of the partition plate 26 (ceiling surface 253 of the first region 251) can be set to, for example, 0.5 mm within a range of 0.3 to 1.5 mm.

[0036] A connector 7 for connecting to an external device is attached to the upper surface of the circuit board 6 on the side of the second region 252. The connector 7 is composed of, for example, a two-piece receptacle 71, and this receptacle 71 is surface-mounted to the circuit board 6 using SMT (Surface Mount Technology). That is, the connector 7 is mounted by the following steps: printing solder on the circuit board 6, mounting the receptacle 71 on the circuit board 6, and then applying heat to melt the solder and fix the receptacle 71. As shown in FIG. 3 , the connector 7 is arranged so that the receptacle 71 faces an opening 271 formed in a side surface 27 on one end side of the lower member 22 of the base body 2.

[0037] In this way, the connector 7 is disposed between the circuit board 6 and the partition plate 26 in the second region 252 of the second recess 25 of the base body 2. In the region (second region 252) where the connector 7 is disposed, the thickness dimension of the partition plate 26 is smaller than the thickness dimension L1 of the region (first region 251) where the oscillator circuit 71 is disposed.

[0038] 3, consider a case where the height dimension of the receptacle 71 surface-mounted on the upper surface of the circuit board 6 is greater than the height dimension of the oscillator circuit 61 arranged on the same surface. In this case, if the partition plate 26 is formed with a uniform thickness L1, the second recess 25 must be formed deeper to ensure a space for arranging the receptacle 71, which would result in an increase in the size of the sensing device 1.

[0039] On the other hand, when the opening 20 for the connector 7 is formed toward the side surface 27 of the lower member 22, the receptacle 71 can be disposed at a position away from the region directly below the Peltier element unit 3, as shown in FIG. 3. By disposing the receptacle 71 at a position away from directly below the Peltier element unit 3, the effects of heat exhaust from the Peltier element unit 3 can be reduced. Furthermore, compared to the oscillator circuit 61, the receptacle 71 itself is a component that is less susceptible to adverse effects from heat. For this reason, in order to reduce the size of the sensing device 1, the thickness of the partition plate 26 is reduced in the second region 252 where the connector 7 is provided, thereby ensuring space for disposing the receptacle 71.

[0040] 4, two sockets 63 for inserting the pins 53 are provided on the upper surface of the circuit board 6, one at the front end and one at the rear end of the oscillator circuit 61. Each socket 63 has an insertion opening formed therein so that a plurality of pins 53, for example, four pins 53, can be inserted. These insertion openings are arranged side by side in the left-right direction.

[0041] The socket 63 is conductive and electrically connected to each of the oscillator circuits 61, 62. The positions of the insertion openings of each socket 63 correspond to the positions of the pins 53, which are inserted into the respective insertion openings. For ease of illustration, the sockets 63 are omitted from FIG. 3. Furthermore, one end of a cable 64 is connected to the circuit board 6, and the other end of the cable 64 is connected to the connector 7.

[0042] According to the above-described configuration, the pins 53 connected to the crystal unit 4 pass through the holes 242 in the base body 2 and are inserted into the respective insertion openings of the sockets 63 provided on the circuit board 6. By inserting the pins 53 into the sockets 63 in this manner, the sockets 63, which are electrodes connected to the circuit board 6, are electrically connected to the pins 53. As a result, the crystal unit 4 and the temperature detection unit 52 of the sensor board 5 are electrically connected to the circuit board 6. The circuit board 6 is fixed to the second recess 25 of the base body 2 by, for example, screws 65. In Fig. 3, reference numeral 66 denotes a member having a screw hole for inserting the screw 65, and the circuit board 6 is fixed to the partition plate 26 by the screw in the second region 252, for example.

[0043] The base body 2 is also provided with a base cover 21 that covers the second recess 25 from the underside. The base cover 21 is attached to the base body 2, for example, with screws (not shown). In this way, a space 250 that houses the circuit board 6 is formed between the second recess 25 and the base cover 21. As shown in Figures 3 and 4, for example, the base cover 21 includes a horizontal plate member 211 that is formed so as to be able to cover the second recess 25 in a plan view, and a vertical portion 212 that is formed by bending one end of the plate member 211. The thickness of the plate member 211 is set to, for example, 1 mm.

[0044] The vertical portion 212 engages with an opening 271 formed in the side surface 27 at one end of the base body 2 to form an opening 20 for the connector 7. As a result, the receptacle 71 of the connector 7 is connected to an external plug (not shown) through the opening 20. Furthermore, with the base cover 21 attached, the distance between the lower surface of the oscillator circuit 62 on the lower side of the circuit board 6 and the upper surface of the base cover 21 can be set to, for example, 0.5 mm within the range of 0.3 to 1.5 mm.

[0045] The features of the sensing device 1 according to this embodiment will now be described. The sensing device 1 of the present invention is configured such that the connector 7 is housed in the second recess 25 of the base body 2 and is connected to the outside from the side surface 27 of the base body 2. Therefore, compared to a configuration in which the connector 19 protrudes downward from the base portion 12 as in the comparative embodiment, the height dimension of the sensing device 1 is smaller, allowing for miniaturization.

[0046] Furthermore, whereas in the comparative example the Peltier element 13 is provided on the base portion 12 via the Peltier base 130, in the sensing device 1 of the present invention the Peltier element portion 3 is provided to be housed within the first recess 24 of the base body 2. By integrating the base body 2 and the Peltier base in this way, the height dimension of the sensing device 1 can be reduced by an amount equivalent to the thickness dimension of the Peltier base 130.

[0047] The present invention focuses on miniaturizing the sensing device 1 and has reviewed the components of the comparative embodiment while taking into consideration the thermal effects on the oscillator circuits 61 and 62. As a result, even in a configuration that does not include a Peltier base 130, it is believed that by optimizing the thickness dimension L1 of the partition plate 26 of the base body 2 and the separation distance L2 between the lower surface of the partition plate 26 and the upper surface of the oscillator circuit 61, it is possible to suppress the thermal effects on the oscillator circuits 61 and 62 and achieve miniaturization of the sensing device 1, as described above.

[0048] Furthermore, the thickness of the base cover 21 of the sensing device 1 has been revised to make it thinner than the comparative embodiment. Also, the opening diameter of the opening 82 of the cover body 8 has been widened and the guide 83 has a gentler slope, so that the distance between the sensor board 5 and the upper surface 81 of the cover body 8 is set smaller than in the comparative embodiment. These innovations also contribute to the miniaturization of the sensing device 1.

[0049] Furthermore, by reducing the number of components and making the sensing device 1 thinner in order to reduce its size, it is possible to reduce the weight and cost of the sensing device 1. Furthermore, in the comparative embodiment, the connector 19 is connected to the circuit board 18 by a cable, and this connection was made by manual soldering, but in the sensing device 1 of the present invention, the connector 7 is surface-mounted on the circuit board 6, which simplifies the work process compared to connecting a cable manually. Furthermore, the connector cover 191 that was necessary in the comparative embodiment is no longer necessary, which reduces the number of parts.

[0050] Furthermore, in the comparative example, the Peltier base 130 and the Peltier element section 13 were adhered together and then screwed to the base section 12, but in the sensing device 1 of the present invention, the Peltier element section 3 is directly adhered to the base body 2. This also eliminates the need for lock bolts that were required to screw the Peltier base 130, which also reduces the number of parts. This reduction in the number of parts and labor also contributes to cost reductions. In this way, the sensing device 1 of the present invention can be made smaller, lighter, and less expensive to manufacture than the comparative example. Therefore, the range of applications of the sensing device 1 that senses gas as a sensing target substance can be expanded compared to conventional devices.

[0051] As an example of the size of such a sensing device 1, the left-right dimension L3 of the base body 2 is 27 mm, the front-to-back dimension L4 is 29 mm, and the height L5 from the bottom end of the base body 2 to the top end of the cover body 8 is 18 mm, making it smaller than the comparative sensing device 11.

[0052] Next, a sensing system 9 using the sensing device 1 will be described with reference to Fig. 6. The sensing system 9 includes a vacuum container 90, one of whose sides is configured as a cooling unit 91 for cooling the sensing device 1. The sensing device 1 is mounted in the vacuum container 90, as shown in Fig. 6, with the base body 2 fixed to the cooling unit 91 and the opening 82 of the cover body 8 facing horizontally. The cooling unit 91 is configured, for example, by a chiller having a flow path 911 through which a cooling medium flows, and is configured to cool the base body 2 and, via this base body 2, cool a circuit board 62 having oscillation circuits 61, 62.

[0053] Because the base body 2 has high thermal conductivity, when it is cooled by the chiller, the partition plate 26 and the protrusion 23 are also cooled. This also cools the Peltier element unit 3 and cover body 8 that are in contact with the base body 2, and the entire sensing device 1 is cooled. In this way, the heat of the cooling unit 91 is thermally conducted to the Peltier element unit 3 via the base body 2, so it can be said that the base body 2 supplies and exhausts heat to and from the Peltier element unit 3. Note that the base body 2 may be configured to either supply or exhaust heat to the Peltier element unit 3.

[0054] Inside the vacuum vessel 90, a stand 93 for supporting a sample 92 is provided at a position opposite the opening 82 of the sensing device 1, and this stand 93 can be heated to a predetermined temperature by a heating mechanism 94. The vacuum vessel 90 is connected to a vacuum exhaust mechanism 96 via an exhaust path 95, and is configured to be evacuated to a predetermined vacuum level.

[0055] Furthermore, when the sensing device 1 is attached to the cooling unit 91, the receptacle 71 of the connector 7 and the plug provided on the power supply unit 97 are connected to each other inside the vacuum container 90. This electrically connects the sensing device 1 to the main body of the sensing system 9 (not shown). In this way, the oscillator circuits 61 and 62 are electrically connected to the external main body, and are configured to be able to acquire the oscillation frequency of the crystal oscillator 4. Furthermore, they are configured to be able to supply current to the Peltier element unit 3, and to be able to acquire the temperature of the crystal oscillator 4 detected by the temperature detection unit 52. Then, based on the temperature of the crystal oscillator 4 detected by the temperature detection unit 52, the direction of the current supplied to the Peltier element unit 3 and the supplied power are adjusted to adjust the temperature of the crystal oscillator 4. This allows the temperature of the crystal oscillator 4 to be raised from a predetermined temperature at a predetermined rate.

[0056] In this sensing system 9, after the sample 92 is supported on the base 93, the vacuum container 90 is closed, the inside of the vacuum container 90 is evacuated to a predetermined vacuum level, and the base 93 is heated to, for example, 125°C by the heating mechanism 94. As a result, gas, which is the substance to be sensed contained in the sample 92, sublimes and is released into the vacuum container 90. Meanwhile, a cooling medium is supplied to the cooling unit 91, and the temperature is adjusted by the Peltier element unit 3 to cool the quartz crystal oscillator 4 to, for example, -80°C. As a result, gas generated by heating the sample 92 enters the sensing device 1 through the opening 82 and adheres to the first excitation electrode 41.

[0057] At this time, the change in mass of the quartz oscillator 4 causes a change in the oscillation frequency of the quartz oscillator 4, allowing the substance to be sensed to be detected. Furthermore, while continuing to acquire the oscillation frequency, the Peltier element unit 3 adjusts the temperature, raising the temperature of the quartz oscillator 4 at a rate of, for example, 1°C / min. When the substance to be sensed that has adhered to the first excitation electrode 41 is detached as a result of this temperature rise in the quartz oscillator 4, the oscillation frequency changes significantly at that point. A user of the sensing system 9 can read the timing at which the oscillation frequency changes from a graph showing the change in the oscillation frequency over time, identify the temperature at which the change occurred based on the timing of the change, and further identify the type of substance to be sensed based on that temperature.

[0058] In this example, the quartz crystal oscillator 4 is equipped with a second excitation electrode 42 (reference electrode), so the oscillation frequency F1 on the reaction electrode 41 side and the oscillation frequency F2 on the reference electrode 42 side are measured. Then, the difference between these oscillation frequencies F1 and F2 is obtained, and from the relationship between the difference obtained in advance and the amount (mass) of the substance to be sensed, the amount of the substance to be sensed corresponding to the difference can be detected.

[0059] In this way, the sensing device 1 is used in the vacuum atmosphere of the sensing system 9, and the space 250 accommodating the circuit board 6 between the second recess 25 and the base cover 21 is a vacuum atmosphere. As a result, the oscillator circuit 61, which is spaced apart from the partition plate 26, is vacuum-insulated from the partition plate 26. Therefore, even if the separation distance L2 between the oscillator circuit 61 and the partition plate 26 is relatively small, within the range of 0.3 to 1.5 mm, the influence of heat exhausted from the partition plate 26 is inherently small. Meanwhile, the partition plate 26 itself is quickly cooled by heat conduction from the cooling unit 91, thereby suppressing the thermal influence from the partition plate 26. For this reason, even if the separation distance L2 is set small in order to reduce the size of the sensing device 1, the thermal influence on the oscillator circuit 61 is not so great.

[0060] Another example of the sensing device 1 of the present invention is shown in Fig. 7. This figure shows a configuration example in which the connector 7 is provided on the underside of the circuit board 6. In this example, the base body 2A also has a lower member 22A and a protrusion 23, and the upper side of the partition plate 26A is configured in the same way as in the above-described embodiment. On the other hand, the partition plate 26A can be configured to have a uniform thickness, for example. A circuit board 6 including oscillator circuits 61 and 62 is disposed in a second recess 25A formed below the partition plate 26A, and a connector 7 is surface-mounted on the underside of the circuit board 6.

[0061] The second recess 25A is then covered from below by the base cover 21A, and an opening 20A for the connector 7 is formed between the second recess 25A and an opening 272 formed in the side surface 27A at one end of the base body 2A. In this example, too, for example, by adjusting the thickness dimension of the partition plate 26A, the height dimension of the lower member 22A of the base body 2A can be made the same as that of the lower member 22 in the embodiment shown in Figures 3 and 4, thereby making it possible to reduce the size of the sensing device 1.

[0062] In the above-described embodiment, the receptacle 71 of the two-piece connector is provided on the circuit board 6 and is connected to an external plug. Alternatively, the plug of the two-piece connector may be surface-mounted on the circuit board 6 and connected to an externally provided receptacle. Furthermore, in the above-described embodiment, the first excitation electrode 41, which is a reaction electrode, and the second excitation electrode 42, which is a reference electrode, are provided on one side of the quartz crystal resonator 4, but the quartz crystal resonator 4 may be configured to have only the excitation electrode as a reaction electrode on one side. [Explanation of symbols]

[0063] 1 Sensing device 2 Base body 21 Base cover 3 Peltier element 4 crystal oscillator 41, 42, 43 Excitation electrode 5 Sensor board 6 Circuit Board 61, 62 Oscillator circuit 7 Connectors

Claims

1. A sensing device that adsorbs a gaseous substance to be sensed onto a piezoelectric vibrator, changes the temperature of the piezoelectric vibrator to desorb the substance, and senses the substance based on the relationship between the change in oscillation frequency of the piezoelectric vibrator and the temperature, a sensor substrate that holds the piezoelectric vibrator; a Peltier element unit that is in contact with the sensor substrate and includes a temperature control surface for changing the temperature of the piezoelectric vibrator and a heat dissipation surface on the opposite side of the temperature control surface; a circuit board on which an oscillation circuit is mounted, the oscillation circuit being electrically connected to the piezoelectric vibrator and causing the piezoelectric vibrator to oscillate, and on which a connector for connecting to an external device is surface-mounted; a base body having a first recess for accommodating an area of ​​the Peltier element portion on the heat dissipation surface side and a second recess for accommodating the circuit board, with a partition plate sandwiched between them; a cover body that houses the base body in a region where the first recess is formed, the Peltier element portion protruding outside the first recess, and the sensor substrate, and has an opening formed in it corresponding to an arrangement region of the piezoelectric vibrator that adsorbs the substance to be sensed; a base cover that covers the second recess, The connector is connected to the outside from the side of the region of the base body where the second recess is formed.

2. The sensing device according to claim 1, characterized in that the Peltier element is housed in the first recess so that the heat dissipation surface is in contact with the partition plate, and the circuit board is housed in the second recess so that the oscillator circuit is spaced from the partition plate.

3. 3. The sensing device according to claim 2, wherein the distance between the oscillator circuit and the partition plate is within a range of 0.3 to 1.5 mm.

4. The sensing device described in claim 2, characterized in that the sensing device is used in a vacuum atmosphere, and the space accommodating the circuit board between the front second recess and the base cover becomes a vacuum atmosphere, so that the oscillator circuit, which is located away from the partition plate, is vacuum insulated from the partition plate.

5. The sensing device according to claim 1, characterized in that the connector is arranged between the partition plate and the circuit board, and the partition plate is configured so that the thickness dimension is larger in the area where the oscillator circuit is arranged than in the area where the connector is arranged.

6. 5. The sensing device according to claim 4, wherein the thickness of the partition plate in the region where the oscillation circuit is disposed is within a range of 3 to 5 mm.

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