Metal oxide semiconductor sensor

Abstract

The invention relates to the technical field of gas sensors, in particular to a metal oxide semiconductor sensor which comprises a protective shell, a bottom plate, a heating piece and a selective film. An opening is formed in one end of the protective shell; the bottom plate is arranged in the protective shell, a semiconductor layer is arranged on the bottom plate, and an electrode group is arranged on the semiconductor layer; the heating element is arranged in the protective shell and is positioned on one side, deviating from the semiconductor layer, of the bottom plate; the selective membrane is arranged on the protective shell and covers the opening, and the selective membrane is used for filtering gas so that specific gas can enter the protective shell. The present application has an effect of reducing the possibility of a decrease in sensitivity of a sensor.

Description

Technical Field

[0001] The present application relates to the technical field of gas sensors, and in particular to a metal oxide semiconductor sensor. Background Art

[0002] At present, gas sensors mainly include metal oxide semiconductor sensors, catalytic combustion sensors, electrochemical sensors, etc. Metal oxide semiconductor sensors (hereinafter referred to as sensors) are the most widely used due to their many advantages such as low power consumption, low price, and miniaturization. The sensor uses metal oxide as a sensitive material. Its detection principle is based on the chemical adsorption and desorption of gas on the surface of metal oxide to change its own conductivity, and monitor the concentration of the target gas by comparing the current change.

[0003] Regarding the above-mentioned related technologies: Due to the broad-spectrum response characteristics of the metal oxide semiconductor sensor itself, it is impossible to achieve "one-to-one" selection of specific gases, which is mainly attributed to the properties of the sensor's gas-sensitive material itself and the stability of the operating temperature. In order to improve the selectivity of metal oxide semiconductor sensors, the prior art generally designs gas-sensitive materials with specific micro / mesoscopic morphologies for specific target detection gases. Although this method can improve the sensor selectivity to a certain extent, it requires large-scale preparation of gas-sensitive materials in actual production applications. The preparation process is complex and difficult to control, and it is difficult to obtain mass-produced gas-sensitive materials with stable performance. Summary of the invention

[0004] In order to solve the above technical problems, the present application provides a metal oxide semiconductor sensor.

[0005] The present application provides a metal oxide semiconductor sensor, which adopts the following technical solution: A metal oxide semiconductor sensor, comprising: A protective shell, one end of which is open; A bottom plate is arranged in the protective shell, and a semiconductor layer and an electrode group electrically connected to each other are respectively arranged on the bottom plate; A heating element, disposed in the protective housing and located on a side of the bottom plate away from the semiconductor layer; A selective membrane is arranged on the protection shell and covers the opening, and the selective membrane is used for filtering gas so as to allow specific gas to enter the protection shell.

[0006] By adopting the above technical solution, the selective membrane covers the opening, enabling external air to enter the protective housing and react with the semiconductor layer only through the selective membrane. This facilitates the screening of external air by the selective membrane to block non-specific gases outside the protective housing and allow specific gases to smoothly enter the protective housing, thereby helping to avoid the problem of reduced accuracy of the sensor caused by the interference of multiple gases with each other.

[0007] Optionally, the selective membrane is arranged at an interval from the semiconductor layer.

[0008] By adopting the above technical solution, the selective membrane is arranged at an interval from the semiconductor layer, making it difficult for the heat generated when the heating element works to be transferred to the selective membrane through the semiconductor layer. This helps to reduce the possibility of thermal expansion and contraction of the selective membrane after heating, resulting in changes in the physical properties of the selective membrane, and thus facilitates the stable functioning of the selective membrane.

[0009] Optionally, a through groove is formed on the side wall of the protective housing, the through groove communicates with the inside of the protective housing, and the selective membrane covers the through groove.

[0010] By adopting the above technical solution, the setting of the through groove facilitates the circulation of the gas in the protective housing between the opening and the through groove.

[0011] Optionally, a connecting piece is arranged on the selective membrane, the connecting piece is detachably connected to the protective housing, and the connecting piece is used to support the selective membrane.

[0012] By adopting the above technical solution, the selective membrane is detachably connected to the protective housing through the connecting piece, enabling the selective membrane to be replaced, so as to facilitate the replacement of the selective membrane according to the gas to be detected, enabling the sensor to detect different gases.

[0013] Optionally, a plugging groove and a limiting groove are respectively formed on the protective housing, the plugging groove communicates with the limiting groove, a limiting block is arranged on the connecting piece, the connecting piece is inserted into the plugging groove, and the limiting block is inserted into the limiting groove, and the limiting block is used to limit the connecting piece in the plugging groove.

[0014] By adopting the above technical solution, when the connecting piece is inserted into the plugging groove, the limiting block is inserted into the limiting groove to limit the connecting piece in the plugging groove, thus facilitating the stable support of the selective membrane by the connecting piece.

[0015] Optionally, sealing gaskets are respectively filled between the limiting block and the inner wall of the limiting groove and between the connecting piece and the inner wall of the plugging groove.

[0016] By adopting the above technical solution, the gasket can fill the gaps between the limiting block and the inner wall of the limiting groove, and between the connecting member and the inner wall of the insertion groove, so that the limiting block is not likely to move in the limiting groove, and the connecting member is not likely to move in the insertion groove, which is conducive to improving the stability of the connecting member inserted in the insertion groove.

[0017] Optionally, a receiving cavity is formed in the side wall of the protective housing, and a phase change material is filled in the receiving cavity.

[0018] By adopting the above technical solution, the phase change material can absorb the excess heat generated when the heating element works, and release the absorbed heat when the heating element stops working, so as to facilitate the adjustment of the temperature inside the protective housing, make the temperature inside the protective housing within a relatively constant temperature range, and then facilitate the semiconductor layer to work within a suitable temperature range.

[0019] Optionally, a heat conducting member is arranged on the inner wall of the receiving cavity close to the inside of the protective housing, the heat conducting member extends into the protective housing and is arranged close to the heating element, and a heat insulating layer is arranged on the inner wall of the receiving cavity far from the heat conducting member.

[0020] By adopting the above technical solution, the heat conducting member is convenient for guiding the excess heat generated when the heating element works to the phase change material for the phase change material to absorb. And the heat insulating layer makes the heat in the receiving cavity not easily dissipated to the outside of the protective housing, so as to facilitate the phase change material to release more heat into the protective housing, reduce the energy loss to a certain extent, and then is conducive to adjusting the temperature inside the protective housing.

[0021] Optionally, a through hole is formed in the protective housing, the through hole is communicated with the receiving cavity, a sliding member is slidably arranged in the receiving cavity, one end of the sliding member abuts against the phase change material, and the other end of the sliding member is inserted into the through hole. When the phase change material absorbs too much heat, one end of the sliding member penetrates out of the through hole.

[0022] By adopting the above technical solution, when the phase change material absorbs heat, the phase change material will undergo a phase change, so that the volume of the phase change material increases to push the sliding member to move in the direction close to the through hole. And when the selective film ages or too much dust and other impurities accumulate on the selective film, the gas that can pass through the selective film decreases, so that the heat taken out of the protective housing by the gas decreases, enabling the phase change material to absorb more heat, which will cause the volume of the phase change material to increase again to a certain extent, and then it is convenient to use the phase change material to push the sliding member to move, so that the sliding member penetrates out of the through hole, facilitating the staff to judge that the selective film needs to be replaced.

[0023] Optionally, an elastic film is arranged in the through hole.

[0024] By adopting the above technical solution, when the sliding member passes through the through hole, the sliding member will apply pressure to the elastic membrane, causing the elastic membrane to extend, so that the elastic membrane is not likely to hinder the movement of the sliding member. Moreover, the arrangement of the elastic membrane reduces to a certain extent the possibility of external dust and other impurities entering the through hole, thus facilitating the smooth sliding of the sliding member in the accommodation cavity.

[0025] In summary, the present application includes at least one of the following beneficial technical effects: 1. By providing a selective membrane on the protective housing, non-specific gases are not likely to enter the protective housing, while specific gases can smoothly enter the protective housing, which is beneficial to avoiding the mutual interference of various gases and reducing the accuracy of the sensor, and further beneficial to reducing the possibility of the decrease in the sensitivity of the sensor; 2. Through the mutual cooperation of the connecting member, the selective membrane, the protective housing and the limiting block, the selective membrane can be detachably connected to the protective housing through the connecting member and the limiting block, so as to facilitate the replacement of the selective membrane. Furthermore, by replacing different selective membranes, the sensor can detect different gases, and it is also convenient to replace the selective membrane when the selective membrane ages or is damaged; 3. Through the mutual cooperation of the protective housing, the phase change material, the heat conducting member and the heat insulating layer, the excess heat generated when the heating member works can be absorbed by the phase change material, and the phase change material can release the absorbed heat when the heating member stops working, so as to facilitate the adjustment of the temperature in the protective housing, make the temperature in the protective housing in a relatively constant temperature range, and further facilitate the operation of the semiconductor layer in a suitable temperature range; 4. Through the mutual cooperation of the protective housing, the phase change material, the sliding member and the elastic membrane, when the selective membrane ages or too much dust and other impurities accumulate on the selective membrane, resulting in a reduction in the gas passing through the selective membrane, the phase change material can absorb more heat, causing the volume of the phase change material to increase after phase change, so as to push the sliding member to move, making one end of the sliding member pass through the through hole and push the elastic membrane to extend, thus facilitating the staff to judge that the selective membrane needs to be replaced. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic diagram of the overall structure of a metal oxide semiconductor sensor in Embodiment 1 of the present application.

[0027] Figure 2 is along Figure 1 The cross-sectional view taken along line A-A in

[0028] Figure 3 is a schematic diagram of the structure of the protective housing in Embodiment 1 of the present application.

[0029] Figure 4 isFigure 2 A partial enlarged view of point B in the middle.

[0030] Description of reference numerals: 1. Protective shell; 11. Opening; 12. Plug-in slot; 13. Limiting slot; 14. Sealing gasket; 15. Through slot; 16. Accommodating cavity; 17. Heat-conducting part; 18. Heat-insulating layer; 19. Through hole; 191. Elastic membrane; 2. Bottom plate; 21. Semiconductor layer; 22. Electrode group; 3. Heating part; 4. Connecting part; 41. Limiting block; 5. Selective membrane; 6. Phase change material; 7. Sliding part. DETAILED DESCRIPTION

[0031] The following is combined with Figures 1-4 This application is described in further detail. Example 1

[0032] Embodiment 1 of the present application discloses a metal oxide semiconductor sensor.

[0033] It should be noted that, in the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicating orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0034] Reference Figure 1 and Figure 2 The metal oxide semiconductor sensor comprises a protective shell 1, a bottom plate 2, a heating element 3, a connecting element 4 and a selective membrane 5. The bottom plate 2 and the heating element 3 are respectively arranged in the protective shell 1, and the bottom plate 2 is respectively provided with a semiconductor layer 21 and an electrode group 22 electrically connected to each other, and the heating element 3 is located on the side of the bottom plate 2 away from the semiconductor layer 21. An opening 11 is provided on the side of the protective shell 1 close to the semiconductor layer 21, and the selective membrane 5 is detachably connected to the protective shell 1 through the connecting element 4, and the selective membrane 5 covers the opening 11, so that when the external gas flows into the protective shell 1, the selective membrane 5 can screen the external gas to block the non-specific gas outside the protective shell 1 and allow the specific gas to smoothly enter the protective shell 1, thereby helping to reduce the possibility of multiple gases interfering with each other and causing the accuracy of the sensor to be reduced.

[0035] In this embodiment, the heating element 3 can be configured as a heating wire.

[0036] Reference Figure 1, the selective membrane 5 is arranged at an interval from the semiconductor layer 21, so that the heat generated when the heating element 3 works is not easily transferred to the selective membrane 5 through the semiconductor layer 21, which is beneficial to reducing the possibility that the selective membrane 5 expands and contracts thermally after being heated, resulting in changes in the physical properties of the selective membrane 5, and thus facilitating the stable functioning of the selective membrane 5.

[0037] In this embodiment, the selective membrane 5 is a gas selective membrane, and the corresponding type can be set according to actual needs. And the semiconductor layer 21 is made of semiconductor material.

[0038] Refer to Figure 2 and Figure 3 , insertion slots 12 and limiting slots 13 that communicate with each other are respectively formed on the protective housing 1. In this embodiment, the insertion slot 12 communicates with the opening 11. A limiting block 41 is fixedly connected to the connecting member 4. When it is necessary to fix the connecting member 4 on the protective housing 1, first insert the connecting member 4 into the insertion slot 12, and then slide the connecting member 4 so that the connecting member 4 drives the limiting block 41 to be inserted into the limiting slot 13, thereby facilitating the use of the limiting block 41 to limit the connecting member 4, so that the connecting member 4 is not easily separated from the insertion slot 12, and thus facilitating the setting of the selective membrane 5 on the protective housing 1 and covering the selective membrane 5 on the opening 11.

[0039] When it is necessary to remove the connecting member 4 from the protective housing 1, first move the connecting member 4 in a direction away from the limiting slot 13, so that the connecting member 4 drives the limiting block 41 to disengage from the limiting slot 13, thereby facilitating the extraction of the connecting member 4 from the insertion slot 12, and thus facilitating the replacement of the selective membrane 5.

[0040] Sealing gaskets 14 are respectively filled between the limiting block 41 and the inner wall of the limiting slot 13, and between the connecting member 4 and the inner wall of the insertion slot 12. In this embodiment, the sealing gasket 14 is a rubber gasket, so that the sealing gasket 14 can apply a pre-tightening force to the connecting member 4 and the limiting block 41, so that the connecting member 4 abuts against the inner wall of the insertion slot 12, and thus is beneficial to improving the stability of the connecting member 4 inserted in the insertion slot 12.

[0041] Refer to Figure 2 and Figure 3 , a through slot 15 is formed on the side wall of the protective housing 1, and the through slot 15 communicates with the inside of the protective housing 1 to facilitate the air flow inside and outside the protective housing 1, so that the outside air can flow between the opening 11 and the through slot 15.

[0042] In this embodiment, insertion slots 12 and limiting slots 13 are also formed on the periphery of the through slot 15, so as to facilitate the installation of the selective membrane 5 at the through slot 15 by using the connecting member 4 and covering the selective membrane 5 on the through slot 15 to prevent unfiltered gas from the outside from entering the protective housing 1 through the through slot 15.

[0043] Refer toFigure 2 A receiving cavity 16 is formed in the side wall of the protective housing 1. The receiving cavity 16 is filled with a phase change material 6, and the phase change material 6 does not completely fill the receiving cavity 16. A heat conducting member 17 is fixedly connected to the inner wall of the receiving cavity 16 close to the inside of the protective housing 1. The heat conducting member 17 extends into the protective housing 1 and is disposed close to the heating member 3.

[0044] When the heating member 3 operates, part of the heat generated by the heating member 3 is absorbed by the semiconductor layer 21, and the heat not absorbed by the semiconductor layer 21 is absorbed by the phase change material 6 through the heat conducting member 17. The phase change material 6 can release the absorbed heat after the heating member 3 stops operating, thereby facilitating the adjustment of the temperature inside the protective housing 1 so that the temperature inside the protective housing 1 is within a relatively constant temperature range, and further facilitating the operation of the semiconductor layer 21 within a suitable temperature range, which improves the sensitivity of the sensor to a certain extent.

[0045] In this embodiment, the phase change material 6 undergoes a phase change during both the heat absorption and heat release processes. When the phase change material 6 absorbs heat, its volume increases; when the phase change material 6 releases heat, its volume decreases.

[0046] A heat insulation layer 18 is provided on the inner wall of the receiving cavity 16 away from the heat conducting member 17, so that the heat inside the receiving cavity 16 is not easily dissipated to the outside of the protective housing 1, thereby facilitating the release of more heat from the phase change material 6 into the protective housing 1, reducing the energy loss to a certain extent, and further facilitating the adjustment of the temperature inside the protective housing 1. In this embodiment, the heat insulation layer 18 is made of a heat insulating material.

[0047] Refer to Figure 4 A through hole 19 is formed in the protective housing 1. The through hole 19 is communicated with the receiving cavity 16, and an elastic membrane 191 is disposed in the through hole 19, so that foreign matters such as dust in the outside world are not easily introduced into the receiving cavity 16 through the through hole 19.

[0048] Refer to Figure 2 and Figure 4 A sliding member 7 is slidably disposed in the receiving cavity 16. One end of the sliding member 7 is adapted to the shape of the receiving cavity 16 and fits against the inner wall of the receiving cavity 16. The other end of the sliding member 7 is inserted into the through hole 19 and fits against the inner wall of the through hole 19. And the end of the sliding member 7 away from the through hole 19 abuts against the phase change material 6.

[0049] When the selective membrane 5 ages or too much dust and other impurities accumulate on the selective membrane 5, the gas that can pass through the selective membrane 5 decreases, resulting in less heat being carried out of the protective housing 1 by the gas. As a result, the phase change material 6 can absorb more heat, causing the volume of the phase change material 6 to increase again after phase change, so as to push the sliding member 7 to move, making one end of the sliding member 7 penetrate out of the through hole 19. At this time, the sliding member 7 will apply pressure to the elastic membrane 191, causing the elastic membrane 191 to extend out of the through hole 19, so as to facilitate the observation by the staff, and then facilitate the staff to judge that the selective membrane 5 needs to be replaced.

[0050] After the phase change material 6 releases heat, the volume of the phase change material 6 decreases, and the sliding member 7 moves in a direction away from the through hole 19, causing one end of the sliding member 7 to move back into the through hole 19, so that the sliding member 7 no longer applies pressure to the elastic membrane 191, and the elastic membrane 191 contracts and returns to its original state.

[0051] The implementation principle of a metal oxide semiconductor sensor according to Embodiment 1 of the present application is as follows: When it is necessary to monitor a specific gas, first prepare the corresponding selective membrane 5, and then apply pressure to the sealing gasket 14 to compress the sealing gasket 14, so as to facilitate the connecting member 4 to drive the limiting block 41 to be completely inserted into the insertion slot 12.

[0052] Then, move the connecting member 4 so that the connecting member 4 drives the limiting block 41 to move into the limiting slot 13. At this time, the sealing gasket 14 rebounds and fills the gap between the connecting member 4 and the insertion slot 12, thus completing the installation of the selective membrane 5.

[0053] At this time, when the outside air enters the protective housing 1, the selective membrane 5 will block the non-specific gas outside the protective housing 1 and allow the specific gas to smoothly enter the protective housing 1, so as to facilitate the reaction of the specific gas with the semiconductor layer 21, which helps the sensor to monitor the specific gas and reduces the interference of the non-specific gas to a certain extent. Embodiment 2

[0054] The difference between Embodiment 2 and Embodiment 1 is that the heating element 3 can be set as a pulse heater.

[0055] Refer to Figure 1 , by adopting the pulse heating method, the heating power of the heating element can be adjusted, so as to facilitate the heating element to heat the semiconductor layer at different heating powers, so that the temperature of the sensor can be switched between high temperature and low temperature, and then the sensor can not only complete the measurement of a specific gas at high temperature, but also delay the attenuation of the sensitivity of the sensor at low temperature, effectively extending the service life of the sensor.

[0056] In this embodiment, the pulse heating method is adopted, so that the high temperature value, low temperature value of the sensor and the duration of high temperature and low temperature can be adjusted, facilitating the stable operation of the sensor in different application scenarios.

[0057] A temperature detector (not shown in the figure) is arranged inside the protective housing to detect the temperature inside the protective housing, and the temperature detector can feedback the detected temperature signal to the heating element to adjust the heating power of the heating element, thus helping to ensure that the sensor reaches the set target operating temperature.

[0058] In the same clean air environment, long-term electrical durability and regular sensitivity tests are respectively carried out on the sensor in two heating states of continuous heating and pulse heating, and the data shown in Table 1 are obtained. Among them, the sensitivity S is the sensitivity of the continuously heated sensor, and the sensitivity S1 is the sensitivity of the pulse-heated sensor.

[0059] Table 1

[0060] In the same air environment, the sensor is respectively subjected to continuous heating and pulse heating, and the average power consumption in the two instant heating states is calculated, and the data shown in Table 2 are obtained: Table 2

[0061] It should be noted that in this embodiment, the test method of sensitivity and the calculation method of power consumption are both conventional technical means for those skilled in the art. Therefore, no further elaboration is made.

[0062] It can be seen that compared with the continuous heating method, adopting the pulse heating method in the sensor can not only reduce energy consumption, but also delay the sensitivity attenuation rate of the sensor.

[0063] The above are all the preferred embodiments of this application. The protection scope of this application is not limited accordingly. Therefore, all equivalent changes made according to the structure, shape and principle of this application should be covered within the protection scope of this application.

Claims

1. A metal oxide semiconductor sensor, characterized in that, include: A protective shell (1), wherein one end of the protective shell (1) is open (11); A bottom plate (2) is arranged in the protective shell (1), and a semiconductor layer (21) and an electrode group (22) which are electrically connected to each other are respectively arranged on the bottom plate (2); A heating element (3) is arranged in the protective housing (1) and is located on a side of the bottom plate (2) facing away from the semiconductor layer (21); A selective membrane (5) is arranged on the protective shell (1) and covers the opening (11), wherein the selective membrane (5) is used to filter gas so as to allow specific gas to enter the protective shell (1).

2. The metal oxide semiconductor sensor according to claim 1, wherein: The selective membrane (5) and the semiconductor layer (21) are arranged at intervals.

3. The metal oxide semiconductor sensor according to claim 1, wherein: A through slot (15) is provided on the side wall of the protective shell (1), the through slot (15) being connected to the interior of the protective shell (1), and the selective membrane (5) is arranged to cover the through slot (15).

4. The metal oxide semiconductor sensor according to claim 1, wherein: The selective membrane (5) is provided with a connecting piece (4), the connecting piece (4) being detachably connected to the protective housing (1), and the connecting piece (4) being used to support the selective membrane (5).

5. The metal oxide semiconductor sensor according to claim 4, wherein: The protective shell (1) is provided with a plug-in slot (12) and a limit slot (13), respectively; the plug-in slot (12) is communicated with the limit slot (13); a limit block (41) is provided on the connecting member (4); the connecting member (4) is inserted into the plug-in slot (12); the limit block (41) is inserted into the limit slot (13); the limit block (41) is used to limit the connecting member (4) within the plug-in slot (12).

6. The metal oxide semiconductor sensor according to claim 5, characterized in that: Sealing pads (14) are filled between the limiting block (41) and the inner wall of the limiting groove (13), and between the connecting piece (4) and the inner wall of the plug-in groove (12), respectively.

7. The metal oxide semiconductor sensor according to claim 1, wherein: A accommodating cavity (16) is provided in the side wall of the protective shell (1), and the accommodating cavity (16) is filled with a phase change material (6).

8. The metal oxide semiconductor sensor according to claim 7, characterized in that: A heat conducting element (17) is provided on an inner wall of the accommodating cavity (16) on one side close to the protective shell (1); the heat conducting element (17) extends into the protective shell (1) and is provided close to the heating element (3); and a heat insulating layer (18) is provided on an inner wall of the accommodating cavity (16) on one side away from the heat conducting element (17).

9. The metal oxide semiconductor sensor according to claim 7, wherein: The protective shell (1) is provided with a through hole (19), the through hole (19) being in communication with the accommodating chamber (16), a sliding member (7) being slidably arranged in the accommodating chamber (16), one end of the sliding member (7) being in contact with the phase change material (6), the other end of the sliding member (7) being inserted into the through hole (19), and when the phase change material (6) absorbs excessive heat, one end of the sliding member (7) passes through the through hole (19).

10. The metal oxide semiconductor sensor according to claim 9, wherein: An elastic membrane (191) is arranged in the through hole (19).

Images