Capacitive pressure sensor

Abstract

A capacitive pressure sensor according to an embodiment of the present invention comprises a first electrode, a second electrode, and a dielectric layer disposed between the first electrode and the second electrode, the layer including a plurality of protrusions on an upper surface thereof, wherein the upper parts of the protrusions are in contact with the first electrode, and the first electrode may comprise a plurality of holes.

Description

Capacitive pressure sensor

[0001] The present invention relates to a capacitive pressure sensor, and more specifically, to a capacitive pressure sensor capable of detecting low pressure.

[0002] Pressure sensors are electronic devices that detect changes in pressure applied to the sensor, and they are classified into various types based on their diverse principles and structures. Examples include resistive pressure sensors, where the resistance of a material changes when pressure is applied; piezoelectric pressure sensors, which generate an electrical signal when a specific material receives pressure; capacitive pressure sensors, which utilize the principle that capacitance changes due to a change in the distance between two electrodes; inductive pressure sensors, which utilize changes in induction between a coil and a core; optical fiber pressure sensors, which utilize light interference caused by the deformation of an optical fiber; pressure diaphragm pressure sensors, which utilize the principle that a thin diaphragm deforms under pressure to generate an electrical signal; and vacuum pressure sensors, which measure pressure in a vacuum state.

[0003] These pressure sensors are used in various fields, including automobiles, aircraft, industrial processes, office automation, home appliances, medical devices, environmental control, industrial robots, and humanoids. In particular, capacitive pressure sensors are widely used in industrial applications, but they have a problem in that it is difficult to detect minute pressures when the material constituting the dielectric layer is rigid.

[0004] The technical problem that the present invention aims to solve is to provide a pressure sensor capable of detecting minute pressure even when the material constituting the dielectric layer is rigid.

[0005] Furthermore, the technical problem that the present invention aims to solve is not limited to the purposes mentioned above, and other unmentioned purposes will be clearly understood by a person skilled in the art from the description below.

[0006] A capacitive pressure sensor according to an embodiment of the present invention comprises a first electrode, a second electrode, and a dielectric layer disposed between the first electrode and the second electrode, wherein the dielectric layer comprises a plurality of protrusions on its upper surface, the upper portion of the protrusions contacts the first electrode, and the first electrode may comprise a plurality of holes.

[0007] In a capacitive pressure sensor according to an embodiment of the present invention, the plurality of protrusions may be arranged only in the portion for sensing pressure.

[0008] In a capacitive pressure sensor according to an embodiment of the present invention, a plurality of holes included in the first electrode may be positioned at a location corresponding to the lower part of the protrusion.

[0009] In a capacitive pressure sensor according to an embodiment of the present invention, the lower part of the protrusion may not come into contact with the first electrode when the first electrode is not pressed.

[0010] In a capacitive pressure sensor according to an embodiment of the present invention, the length of one side of the protrusion may be 0.5 to 3 mm.

[0011] In the capacitive pressure sensor according to an embodiment of the present invention, when no pressure is applied, the ratio of the area in contact with the first electrode to the area not in contact with the protrusion may be 0.25:0.75.

[0012] In a capacitive pressure sensor according to an embodiment of the present invention, the plurality of protrusions may be arranged at regular intervals.

[0013] In a capacitive pressure sensor according to an embodiment of the present invention, the height of the plurality of protrusions or the spacing between the plurality of protrusions may vary depending on the material constituting the dielectric layer.

[0014] According to the present invention, a pressure sensor capable of detecting minute pressure even when the material constituting the dielectric layer is rigid can be provided.

[0015] In addition to these, the effects obtainable from the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present invention belongs from the description below.

[0016] Figure 1a is a diagram illustrating a capacitive pressure sensor.

[0017] Figure 1b is a graph roughly showing the change in thickness of the dielectric layer according to pressure.

[0018] FIG. 2 is a cross-sectional view of a capacitive pressure sensor according to one embodiment of the present invention.

[0019] FIGS. 3a and FIGS. 3b are drawings illustrating protrusions of a dielectric layer according to various embodiments of the present invention.

[0020] FIG. 4 is an exploded perspective view of a capacitive pressure sensor according to one embodiment of the present invention.

[0021] FIG. 5 is a side view showing the change according to the pressure applied to a capacitive pressure sensor according to one embodiment of the present invention.

[0022] FIGS. 6a to 6d are drawings showing examples in which a capacitive pressure sensor according to various embodiments of the present invention is applied.

[0023] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

[0024] However, the technical concept of the present invention is not limited to some of the described embodiments but can be implemented in various different forms, and within the scope of the technical concept of the present invention, one or more of the components among the embodiments may be selectively combined or substituted.

[0025] In addition, terms used in the embodiments of the present invention (including technical and scientific terms) may be interpreted in a sense that is generally understood by those skilled in the art to which the present invention belongs, unless explicitly and specifically defined otherwise. Terms that are commonly used, such as terms defined in advance, may be interpreted in consideration of their meaning in the context of the relevant technology.

[0026] Furthermore, the terms used in the embodiments of the present invention are for the purpose of describing the embodiments and are not intended to limit the present invention.

[0027] In this specification, the singular form may include the plural form unless specifically stated otherwise in the text, and when described as "at least one of A and B and C (or more than one)," it may include one or more of all combinations that can be formed from A, B, and C.

[0028] In addition, terms such as first, second, A, B, (a), (b), etc. may be used when describing the components of the embodiments of the present invention.

[0029] These terms are intended merely to distinguish a component from other components and are not limited by the nature, order, sequence, etc., of the said component.

[0030] And, where it is stated that a component is 'connected', 'combined', or 'joined' to another component, this may include not only cases where the component is directly connected, combined, or joined to the other component, but also cases where it is 'connected', 'combined', or 'joined' due to another component located between the component and the other component.

[0031] Furthermore, when described as being formed or placed "above or below" each component, "above" or "below" includes not only cases where two components are in direct contact with each other, but also cases where one or more other components are formed or placed between the two components. Additionally, when expressed as "above or below," it may include the meaning of a downward direction as well as an upward direction relative to a single component.

[0032] Figure 1a is a diagram illustrating a capacitive pressure sensor.

[0033] Referring to FIG. 1a, a capacitive pressure sensor (100) may include a first electrode (110), a second electrode (120), and a dielectric layer (130) disposed between the first electrode (110) and the second electrode (110). When pressure is applied between the first electrode (110) and the second electrode (120), the capacitance changes as the thickness of the dielectric layer (130) changes. The capacitive pressure sensor (100) can measure the applied pressure by checking the capacitance.

[0034] Specifically, capacitance can be calculated using [Equation 1].

[0035]

[0036] Here, C is capacitance, A is the cross-sectional area of ​​the first electrode (110) and / or the second electrode (120), d is the distance between the first electrode (110) and the second electrode (120), and ε is the permittivity of the dielectric. According to [Equation 1], if the pressure applied between the first electrode (110) and the second electrode (120) increases and the distance between the first electrode (110) and the second electrode (120) narrows, the capacitance increases, and if the pressure decreases and the distance between the first electrode (110) and the second electrode (120) widens, the capacitance decreases.

[0037] According to one embodiment, the distance between the first electrode (110) and the second electrode (120) may be narrower when the dielectric is hard than when it is soft, even if the applied pressure is the same. According to this characteristic, even if the capacitive pressure sensors have the same thickness, a capacitive pressure sensor containing a soft dielectric can only detect low pressure, whereas a capacitive pressure sensor containing a hard dielectric can detect up to high pressure. However, when the dielectric is hard, if the pressure applied between the first electrode (110) and the second electrode (120) is small, the distance between the first electrode (110) and the second electrode (120) may change slightly, and the capacitance may hardly change.

[0038] Figure 1b is a graph roughly showing the change in thickness of the dielectric layer according to pressure.

[0039] Referring to FIG. 1b, in the first section (160), the change in the thickness of the dielectric layer may be small even if the pressure increases. In the second section (170), the thickness of the dielectric layer changes in proportion to the pressure intensity. Finally, in the third section (180), the thickness of the dielectric layer may not change even if the pressure increases. The third section (180) may be a section where the thickness of the dielectric layer can no longer be physically thinned. In summary, there is a problem in that the pressure cannot be properly measured in the first section (160) and the third section (180). The present invention aims to solve the problem of not being able to properly measure pressure in the first section (160) by proposing a capacitive pressure sensor that can measure low pressure using the cross-sectional area of ​​the dielectric layer.

[0040] FIG. 2 is a cross-sectional view of a capacitive pressure sensor according to one embodiment of the present invention.

[0041] Referring to FIG. 2, the capacitive pressure sensor (200) may include a first electrode (210), a second electrode (220), and a dielectric layer (230) disposed between the first electrode (210) and the second electrode (220). Here, the dielectric layer (230) may include a plurality of protrusions (240) on one surface, and the first electrode (210) may include a hole (260) at a position corresponding to a valley (250) of the protrusion.

[0042] According to one embodiment, the crest (270) of the dielectric layer protrusion may come into contact with the first electrode (210). The valley (250) of the dielectric layer protrusion does not come into direct contact with the first electrode (210) unless pressure is applied, and the space between the valley (250) of the dielectric layer protrusion and the first electrode (210) may be filled with air. The space between the valley (250) of the dielectric layer protrusion and the first electrode (210) filled with air may be referred to as an air layer.

[0043] FIGS. 3a and FIGS. 3b are drawings illustrating protrusions of a dielectric layer according to various embodiments of the present invention.

[0044] Referring to FIGS. 3a and 3b, protrusions on the dielectric layer may be placed on one side of the dielectric layer. There may be multiple protrusions, and they may be placed at regular intervals. Additionally, the protrusions may be placed only within an area that overlaps perpendicularly with the pressure sensing portion (e.g., the pressure sensing region described later). If protrusions are placed in a location other than the pressure sensing portion, a change in the cross-sectional area there may also change the capacitance and become noise.

[0045] According to one embodiment, the crest (270), which is the high part of the projection, is flat so that it can come into contact (or touch) with the electrode. On the other hand, the groove (250), which is the low part of the projection, may or may not be flat. FIG. 3a shows a projection in which the groove (250) is not flat, and FIG. 3b shows a projection in which at least a portion of the groove (250) is flat.

[0046] According to one embodiment, air may be filled between the protrusions within the dielectric layer. Since the air between the protrusions must be able to be expelled to the outside when the electrode is pressed, the electrode (210) may include a hole (260). If the electrode (210) does not include a hole (260) and the air is not expelled to the outside, the air between the grooves (250) may move to another location within the dielectric layer, and thus the electrode (210) and the dielectric layer may not make proper contact. The hole (260) may be placed at a location corresponding to the groove (250) of the protrusion, which is where the air is filled. The hole (260) may be placed anywhere in the groove (250) of the protrusion, but since the groove (250) of the protrusion can also make contact with the electrode (210) when pressure is applied, the center between two adjacent protrusions, the center of the groove, or the center of four protrusions may be the most desirable location for the hole (260). According to one embodiment, the location of the hole (260) may be determined by the location, number, and size of the protrusions and / or electrodes placed in the part for detecting pressure. Various examples related to the location of the hole (260) are described in the following embodiments. According to one embodiment, the hole (260) may be circular in shape, but is not limited thereto. Also, the number of holes (260) is not limited. When the electrode (210) is pressed and then released, air may be inserted through the hole (260) and filled between the grooves (250).

[0047] According to one embodiment, the length of one side of a protrusion may vary between 0.5 and 3 mm. Since the protrusion must have a peak (270) portion in contact with the electrode (210) so that capacitance can be measured, the surface area of ​​the protrusion may be larger than a certain size so that the protrusion is not separated from the electrode (210). According to one embodiment, when the protrusion is not pressed, the ratio of the surface area in contact with the electrode (210) to the surface area not in contact with the protrusion may be 0.25:0.75.

[0048] FIG. 4 is an exploded perspective view of a capacitive pressure sensor according to one embodiment of the present invention.

[0049] Referring to FIG. 4, the capacitive pressure sensor (200) may include a first electrode (210), a dielectric layer (230), and a second electrode (220). According to one embodiment, a contact member for contacting the electrode and the dielectric layer, a circuit for measuring capacitance through the electrode, etc. may be further included, but since this is not the gist of the invention, a description thereof is omitted.

[0050] According to one embodiment, the first electrode (210) is an electrode disposed on the upper surface of the capacitive pressure sensor (200) and may be composed of a plurality of electrodes. Each of the plurality of first electrodes (210) may extend in a first direction and be spaced apart from each other.

[0051] The second electrode (220) is an electrode disposed on the lower surface of the capacitive pressure sensor (200) and may be composed of a plurality of electrodes. The upper surface and the lower surface are distinguished only for illustrative purposes and are not actually distinguished. Each of the plurality of second electrodes (220) may extend in a second direction and be spaced apart from one another. Here, the second direction may be a direction perpendicular to the first direction.

[0052] Each region where the first electrode (210) and the second electrode (220) overlap vertically is a pressure-sensing region and can be referred to as a pressure-sensing region. The pressure-sensing region can also overlap vertically with the protrusions and holes of the dielectric layer (230) described below.

[0053] According to one embodiment, the first electrode (210) may include a plurality of holes (260). The holes (260) may be arranged at regular intervals, but are not limited thereto. For example, the location, size, number, and spacing of the holes (260) may vary depending on the location of the capacitive pressure sensor (200) placed to detect pressure. The holes (260) are intended to introduce or discharge air between the first electrode (210) and the dielectric layer (230) and may be placed where air is present on the dielectric layer (230). Referring to FIG. 4, the plurality of holes (260) may be located between each protrusion of the dielectric layer (230).

[0054] According to one embodiment, the dielectric layer (230) may be disposed on the lower surface of the first electrode (210). The dielectric layer (230) may include protrusions as previously described. The protrusions may be disposed on one surface of the dielectric layer (230). One surface of the dielectric layer (230) may be a surface that contacts the first electrode (210). According to one embodiment, the ridge, which is the high part of the protrusion, may always be in contact with the first electrode (210), while other parts may not be in contact with the first electrode (210) and may only be in contact when pressed.

[0055] According to one embodiment, the height of the protrusions and / or the spacing between the protrusions may vary depending on the material constituting the dielectric layer (230). For example, if the material constituting the dielectric layer (230) is hard, the height of the protrusions may be lower than if the material constituting the dielectric layer (230) is soft. Also, if the height of the protrusions is low, the spacing between the protrusions may be narrow. On the other hand, if the material constituting the dielectric layer (230) is soft, the height of the protrusions may be higher because they can be easily pressed, and thus the spacing between the protrusions may be wide.

[0056] According to one embodiment, the second electrode (220) may be disposed on the lower surface of the dielectric layer (230). The second electrode (220) can measure the capacitance of the dielectric layer (230) together with the first electrode (210). The lower surface of the dielectric layer (230) may not include protrusions and may not include holes.

[0057] FIG. 5 is a side view showing the change according to the pressure applied to a capacitive pressure sensor according to one embodiment of the present invention.

[0058] Referring to FIG. 5, (a) represents a state where no pressure is applied to the capacitive pressure sensor, and (f) represents a state where pressure is applied most strongly. Specifically, (a) to (c) represent a state where only the protrusions are pressed because the intensity is not high even when pressure is applied to the capacitive pressure sensor, and (d) to (f) represent a state where the thickness of the dielectric layer becomes thin because the pressure is sufficiently strong.

[0059] Referring again to (a) to (c), the thickness of the portion of the dielectric layer without protrusions remains the same from (a) to (c), but the thickness of the portion with protrusions can become thinner as the pressure increases from (a) to (c), that is, as the pressure increases. At this time, the change in thickness is within the height of the protrusions, and since the height of the protrusions is minute compared to the entire dielectric layer, the change in capacitance due to the change in the height of the protrusions can be ignored. Therefore, in (a) to (c), as the protrusions are pressed, the contact area with the electrode can be expanded, and the pressure can be measured by measuring the capacitance due to the change in cross-sectional area.

[0060] Even if all the protrusions are pressed, if the pressure increases, the dielectric layer may be compressed. (d) to (f) represent a state where the dielectric layer itself is compressed, in which case the cross-sectional area may not change. Therefore, in (d) to (f), pressure can be measured by measuring the capacitance due to the change in thickness of the dielectric layer.

[0061] FIGS. 6a to 6d are drawings showing examples in which a capacitive pressure sensor according to various embodiments of the present invention is applied.

[0062] FIGS. 6a and 6b show embodiments according to the arrangement of protrusions on the dielectric layer and electrodes of the capacitive pressure sensor, and for convenience of explanation, the capacitive pressure sensor is shown in a perspective view.

[0063] Specifically, FIG. 6a illustrates an example in which protrusions (630) of a dielectric layer are formed in an area that overlaps vertically with an electrode (610) placed on the upper surface of a capacitive pressure sensor. Referring to FIG. 6a, the protrusions (630) of the dielectric layer may be arranged in a ratio of 2 x N per electrode (610), and holes (640) may be arranged at the center of every four protrusions (630). FIG. 6a is merely an example, and more or fewer protrusions and / or holes may be arranged.

[0064] FIG. 6b illustrates an example in which a protrusion (630) of a dielectric layer is formed in a pressure sensing area that is vertically overlapping with an electrode (610) placed on the upper surface and an electrode (620) placed on the lower surface of a capacitive pressure sensor. Referring to FIG. 6b, one protrusion (630) of the dielectric layer may be placed in each pressure sensing area, and a hole (640) may be placed between the protrusions. FIG. 6b is merely an example, and more protrusions and / or holes may be placed in the pressure sensing area.

[0065] FIGS. 6c and 6d show embodiments according to the number of protrusions of the dielectric layer placed in the pressure sensing area, and for convenience of explanation, the capacitive pressure sensor is shown in a plan view.

[0066] Specifically, FIG. 6c is an example in which one protrusion (630) of the dielectric layer is arranged for each pressure sensing area, and a hole (640) may be arranged between the protrusions. FIG. 6c shows one hole (640) arranged between the protrusions, but is not limited thereto. For example, two holes (640) may be arranged, or grooves may be arranged at both ends.

[0067] FIG. 6d is an example in which multiple protrusions (630) of the dielectric layer are arranged in each pressure sensing area. Holes may be arranged between the protrusions (630). FIG. 6d may be an example in which a capacitive pressure sensor according to one embodiment of the present invention is applied to a large area.

[0068] Although the invention has been described above with reference to embodiments, this is merely illustrative and does not limit the invention. Those skilled in the art will understand that various modifications and applications not exemplified above are possible within the scope of the essential characteristics of the embodiments. For example, each component specifically shown in the embodiments may be modified and implemented. Furthermore, differences related to such modifications and applications should be interpreted as being included within the scope of the invention as defined in the appended claims.

Claims

1. First electrode; Second electrode; and It includes a dielectric layer disposed between the first electrode and the second electrode, and The above dielectric layer includes a plurality of protrusions on its upper surface, and The high part of the above protrusion contacts the first electrode, and The first electrode above is a capacitive pressure sensor comprising a plurality of holes.

2. In Paragraph 1, A capacitive pressure sensor in which the above plurality of protrusions are placed only in the part for sensing pressure.

3. In Paragraph 1, A capacitive pressure sensor in which a plurality of holes included in the first electrode are positioned at a location corresponding to the lower part of the protrusion.

4. In Paragraph 1, A capacitive pressure sensor in which the lower part of the above-mentioned protrusion does not contact the first electrode when the first electrode is not pressed.

5. In Paragraph 1, The above-mentioned protrusion is a capacitive pressure sensor having a surface length of 0.5 to 3 mm.

6. In Paragraph 1, The above-described protrusion is a capacitive pressure sensor in which the ratio of the area in contact with the first electrode to the area not in contact is 0.25:0.75 when no pressure is applied.

7. In Paragraph 1, The above plurality of protrusions are arranged at regular intervals, forming a capacitive pressure sensor.

8. In Paragraph 1, A capacitive pressure sensor in which the height of the plurality of protrusions or the spacing between the plurality of protrusions varies depending on the material constituting the dielectric layer.

Images