Acceleration sensor

Abstract

The present application discloses an acceleration sensor, which includes a frame, a mass block, elastic beams and piezoresistors. The frame has an internal space; the mass block is located in the internal space; each elastic beam at least includes a first elastic section and a second elastic section connected end to end, and the first elastic section and the second elastic section are arranged at an angle; one end of the elastic beam is fixed on the frame, the other end of the elastic beam is fixed to the mass block, and a plurality of piezoresistors are arranged on each elastic beam and grouped to form three Wheatstone bridge circuits. The above-mentioned elastic beams are arranged with multiple bends, with a larger plane utilization rate. The arrangement of the piezoresistors enables a single mass block to measure accelerations in three axial directions. Moreover, after arranging a plurality of piezoresistors on the elastic beams, the plurality of piezoresistors are easily located in the stress concentration area. This makes the corresponding relationship between the resistance change generated by the piezoresistors due to stress and the acceleration change of the mass block more precise, thereby improving the sensitivity and accuracy of the acceleration sensor.

Description

Technical Field

[0001] This application relates to the technical field of sensor devices, and particularly to an acceleration sensor. Background Art

[0002] Piezoelectric acceleration sensors are widely used because of their large measurement range, simple process and signal processing circuit. Its working principle is that when subjected to acceleration, the resistance value of the piezoresistor inside it changes, and the magnitude of the acceleration can be calculated through the change value of the resistance.

[0003] Among them, the three-axis piezoelectric acceleration sensor can measure the acceleration in three axial directions and has more usage scenarios. Currently, the three-axis piezoelectric acceleration sensor is developing towards miniaturization and low cost. The reduction in volume makes the sensitivity and accuracy of the three-axis piezoelectric acceleration sensor relatively low, and the usage effect is not ideal. Summary of the Invention

[0004] The main technical problem to be solved by this application is to provide an acceleration sensor to improve the sensitivity and measurement accuracy of the three-axis piezoelectric acceleration sensor.

[0005] To solve the above technical problem, the technical solution adopted by this application is to provide an acceleration sensor, which includes: a frame having an internal space; a mass block located in the internal space; a plurality of elastic beams, each of the elastic beams at least includes a first elastic section and a second elastic section connected end to end, and the first elastic section and the second elastic section are arranged at an angle; one end of the elastic beam is fixed on the frame, and the other end of the elastic beam is fixed to the mass block to suspend the mass block in the internal space; a plurality of piezoresistors are arranged on each of the elastic beams and are grouped to form three Wheatstone bridge circuits to measure the acceleration in three axial directions.

[0006] In a possible implementation manner, the elastic beams are the first elastic beam, the second elastic beam, the third elastic beam and the fourth elastic beam with the same shape; the first elastic beam, the second elastic beam, the third elastic beam and the fourth elastic beam are sequentially connected around the side surface of the mass block; wherein, two adjacent elastic beams are axially symmetrically arranged; two opposite elastic beams are centrosymmetrically arranged.

[0007] In a possible implementation manner, each of the elastic beams includes a first elastic section and a second elastic section, and the first elastic section and the second elastic section are perpendicularly arranged; wherein, one end of the first elastic section is connected to the frame, and one end of the second elastic section is connected to the mass block.

[0008] In a possible implementation, the varistor includes a first varistor, a second varistor, a third varistor, a fourth varistor, a fifth varistor, a sixth varistor, a seventh varistor, an eighth varistor, a ninth varistor, a tenth varistor, an eleventh varistor, and a twelfth varistor; wherein, the fifth varistor, the ninth varistor, and the first varistor are disposed on the first elastic beam; the sixth varistor, the tenth varistor, and the second varistor are disposed on the second elastic beam; the seventh varistor, the eleventh varistor, and the third varistor are disposed on the third elastic beam; the eighth varistor, the twelfth varistor, and the fourth varistor are disposed on the fourth elastic beam.

[0009] In a possible implementation, the first varistor, the second varistor, the third varistor, and the fourth varistor are respectively disposed at one end of the second elastic segment of each elastic beam close to the mass block; the fifth varistor, the sixth varistor, the seventh varistor, and the eighth varistor are respectively disposed at one end of the first elastic segment of each elastic beam close to the frame; the ninth varistor, the tenth varistor, the eleventh varistor, and the twelfth varistor are respectively disposed at one end of the first elastic segment of each elastic beam close to the second elastic segment.

[0010] In a possible implementation, the varistors on two adjacent elastic beams are symmetrically disposed; the varistors on two opposite elastic beams are centrosymmetrically disposed.

[0011] In a possible implementation, the third varistor, the fourth varistor, the fifth varistor, and the sixth varistor are first-class varistors; the first varistor, the second varistor, the seventh varistor, and the eighth varistor are second-class varistors; the ninth varistor, the tenth varistor, the eleventh varistor, and the twelfth varistor are third-class varistors.

[0012] In a possible implementation, the first-class varistors, the second-class varistors, and the third-class varistors are the same.

[0013] In a possible implementation manner, it further includes: a plurality of conductive leads arranged on the elastic beam, and one end of each conductive lead is further connected to a gold finger; each varistor is disposed on the conductive lead, and a preset circuit is formed through the conductive lead; wherein, the fifth varistor, the third varistor, the fourth varistor, and the sixth varistor form a first Wheatstone bridge circuit to measure the acceleration in the z-axis direction; the first varistor, the second varistor, the seventh varistor, and the eighth varistor form a second Wheatstone bridge circuit to measure the acceleration in the x-axis direction; the eleventh varistor, the ninth varistor, the tenth varistor, and the twelfth varistor form a third Wheatstone bridge circuit to measure the acceleration in the y-axis direction.

[0014] In a possible implementation manner, the fifth varistor is connected in series with the third varistor, and the fourth varistor is connected in series with the sixth varistor; the two groups of series resistors are connected in parallel to form the first Wheatstone bridge circuit; the first varistor is connected in series with the second varistor, and the seventh varistor is connected in series with the eighth varistor; the two groups of series resistors are connected in parallel to form the second Wheatstone bridge circuit; the eleventh varistor is connected in series with the ninth varistor, and the tenth varistor is connected in series with the twelfth varistor; the two groups of series resistors are connected in parallel to form the third Wheatstone bridge circuit.

[0015] The beneficial effect of this application is: Different from the prior art, this application provides an acceleration sensor, which includes a frame, a mass block, an elastic beam and varistors. The frame has an internal space; the mass block is located in the internal space; each elastic beam at least includes a first elastic section and a second elastic section connected end to end, and the first elastic section and the second elastic section are arranged at an angle; one end of the elastic beam is fixed on the frame, and the other end of the elastic beam is fixed to the mass block to suspend the mass block in the internal space; a plurality of varistors are arranged on each elastic beam and are grouped to form three Wheatstone bridge circuits to measure the acceleration in three axial directions. In the acceleration sensor of this application, the elastic beam is bent in multiple segments. Compared with a straight beam, the equivalent length of this elastic beam is longer and the plane utilization rate is greater. The arrangement of the varistors realizes the measurement of the acceleration in three axial directions, and after arranging a plurality of varistors on the elastic beam, the plurality of varistors are easily located in the stress concentration area. This makes the corresponding relationship between the resistance value change caused by the stress on the varistor and the acceleration change of the mass block more accurate, thereby improving the sensitivity and accuracy of the acceleration sensor. Description of the Drawings

[0016] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0017] Figure 1 is a top view schematic diagram of a partial internal structure of the acceleration sensor of the present application;

[0018] Figure 2 is Figure 1 a schematic diagram of the structure of the first Wheatstone bridge circuit in the acceleration sensor;

[0019] Figure 3 is Figure 1 a schematic diagram of the structure of the second Wheatstone bridge circuit in the acceleration sensor;

[0020] Figure 4 is Figure 1 a schematic diagram of the structure of the third Wheatstone bridge circuit in the acceleration sensor;

[0021] Figure 5 is Figure 1 a schematic diagram of a partial cross-sectional structure of the acceleration sensor cut along AA';

[0022] Among them, 100, acceleration sensor; 110, frame; 130, elastic beam; 131, first elastic beam; 132, second elastic beam; 133, third elastic beam; 134, fourth elastic beam; 140, piezoresistor; 141, first piezoresistor; 142, second piezoresistor; 143, third piezoresistor; 144, fourth piezoresistor; 145, fifth piezoresistor; 146, sixth piezoresistor; 147, seventh piezoresistor; 148, eighth piezoresistor; 149, ninth piezoresistor; 1410, tenth piezoresistor; 1411, eleventh piezoresistor; 1412, twelfth piezoresistor; 150, gold finger; 151, low-resistance silicon; 161, first Wheatstone bridge circuit; 162, second Wheatstone bridge circuit; 163, third Wheatstone bridge circuit; 171, conductive lead; 180, mass block; 181, upper cover plate; 182, lower cover plate; 183, limiting block; 184, bonding ring. Detailed implementation manners

[0023] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0024] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "the", and "said" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless clearly indicated otherwise in the above context. "Plural" generally includes at least two, but does not exclude the case of including at least one.

[0025] It should be understood that the term "and / or" used herein is only a kind of association relationship describing associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally represents an "or" relationship between the front and rear associated objects.

[0026] It should be understood that the term "including", "comprising", or any other variant used herein is intended to cover non-exclusive inclusion, so that a process, method, article, or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such a process, method, article, or device. Without further limitation, the elements defined by the statement "including..." do not exclude the existence of additional identical elements in the process, method, article, or device including the said elements.

[0027] The triaxial piezoresistive acceleration sensor is developing towards miniaturization and low cost. The reduction in volume results in a decrease in the sensitivity and accuracy of the triaxial piezoresistive acceleration sensor.

[0028] Based on the above problems, the present application proposes an acceleration sensor. By setting an elastic beam with multiple bends, several piezoresistors are arranged on the elastic beam, and several piezoresistors form three Wheatstone bridge circuits to measure the acceleration in three axial directions, improving the space utilization rate, conforming to the development trend of the miniaturization of the acceleration sensor, and effectively improving the sensitivity and accuracy of the triaxial piezoresistive acceleration sensor.

[0029] Next, a detailed description of an acceleration sensor provided by the present application will be given in conjunction with the accompanying drawings and embodiments.

[0030] The present application provides an acceleration sensor. Please refer to Figures 1 to 5 , Figure 1It is a top view schematic diagram of the internal part structure of the acceleration sensor of this application; Figure 2 It is Figure 1 A schematic diagram of the structure of the first Wheatstone bridge circuit in the acceleration sensor; Figure 3 It is Figure 1 A schematic diagram of the structure of the second Wheatstone bridge circuit in the acceleration sensor; Figure 4 It is Figure 1 A schematic diagram of the structure of the third Wheatstone bridge circuit in the acceleration sensor; Figure 5 It is Figure 1 A schematic diagram of the partial structure of the cross-section of the acceleration sensor cut along AA'. In a specific embodiment, the acceleration sensor 100 of this application includes a frame 110, a mass block 180, elastic beams 130, and piezoresistors 140.

[0031] The frame 110 has an internal space. The mass block 180 is located in the internal space. A plurality of elastic beams 130, each elastic beam 130 at least includes a first elastic section and a second elastic section connected end to end, and the first elastic section and the second elastic section are arranged at an angle. One end of the elastic beam 130 is fixed on the frame 110, and the other end of the elastic beam 130 is fixed to the mass block 180 to suspend the mass block 180 in the internal space. A plurality of piezoresistors 140 are arranged on each elastic beam 130 and are grouped to form three Wheatstone bridge circuits to measure the acceleration in three axial directions. Specifically, the frame 110 defines the internal space and plays a role in support and protection. To meet the development trend of miniaturization of the triaxial piezoresistive acceleration sensor 100, in this embodiment, the acceleration sensor 100 is an acceleration sensor 100 with a single mass block 180. The acceleration in three axial directions is sensed by the only mass block 180. When the mass block 180 is subjected to acceleration, the mass block 180 generates displacement, and at the same time pulls each elastic beam 130 to cause the elastic beam 130 to deform. The deformation of the elastic beam 130 causes the piezoresistors 140 on the elastic beam 130 to be stressed and generate a change in resistance value. By measuring the change amount of the resistance value of the piezoresistor 140, the magnitude of the stress it receives can be known. Then, through material mechanics analysis, the inertial force received by the mass block 180 can be obtained. Finally, the magnitude of the acceleration of the mass block 180 can be obtained through Newton's second law. Among them, the linear beam stress concentration area is at the root of both ends of the linear beam. Compared with the linear beam, in this embodiment, a multi-segment bent elastic beam 130 is set. The design of the multi-segment bent elastic beam 130 makes the stress concentration area not only located at both ends of the elastic beam 130, but also located at the bending part of the elastic beam 130. The above can make several piezoresistors 140 on the elastic beam 130 all be in the stress concentration area. At the same time, the space utilization rate of the multi-segment bent elastic beam 130 is larger and the equivalent length is longer, which conforms to the development trend of miniaturization of the acceleration sensor 100.

[0032] Different from the prior art, the present application proposes an acceleration sensor 100. The acceleration sensor 100 is provided with an elastic beam 130 having multiple bends. The space utilization rate of the elastic beam 130 with multiple bends is greater, making it easier to arrange the piezoresistors 140 on the elastic beam 130 in the stress concentration area, meeting the miniaturization development trend of the three-axis piezoresistive acceleration sensor 100. Moreover, since the piezoresistors 140 are located in the stress concentration area, the corresponding relationship between the resistance change of the piezoresistors 140 and the acceleration change of the mass block 180 is more accurate, improving the sensitivity and accuracy of the acceleration sensor 100.

[0033] In this embodiment, each elastic beam 130 includes a first elastic segment and a second elastic segment, and the first elastic segment and the second elastic segment are perpendicularly arranged; wherein, one end of the first elastic segment is connected to the frame 110, and one end of the second elastic segment is connected to the mass block 180. Specifically, in this embodiment, the elastic beam 130 has two segments. The perpendicularly arranged first elastic segment and second elastic segment increase the plane utilization rate of the elastic beam 130, improving the sensitivity and accuracy of the acceleration sensor 100. In some other embodiments, the first elastic segment and the second elastic segment may not be perpendicularly arranged, for example, the included angle is an acute angle or an obtuse angle. In addition, the elastic beam 130 may also have three segments, four segments or other numbers of segments, as long as it is ensured that the elastic beam 130 has multiple bends, and the specific arrangement is not limited.

[0034] In this embodiment, the elastic beams 130 are the first elastic beam 131, the second elastic beam 132, the third elastic beam 133 and the fourth elastic beam 134 with the same shape. The first elastic beam 131, the second elastic beam 132, the third elastic beam 133 and the fourth elastic beam 134 are sequentially connected around the side surface of the mass block 180. Among them, two adjacent elastic beams 130 are axially symmetrically arranged, and two opposite elastic beams 130 are centrosymmetrically arranged. Specifically, the four elastic beams 130 are arranged around the mass block 180, suspending the mass block 180 in the internal space of the frame 110, which can effectively prevent the influence of packaging or external stress on the internal structure of the frame 110, improving the stability of the acceleration sensor 100 and the accuracy of acceleration measurement. At the same time, in a preferred embodiment, inside the frame 110, both sides of the elastic beam 130 are also surrounded by the mass block 180, and the elastic beam 130 is embedded in the mass block 180. This setting makes the stress change of the elastic beam 130 more sensitive when the acceleration of the mass block 180 changes, improving the measurement accuracy.

[0035] Further, in this embodiment, the acceleration sensor 100 further includes an upper cover plate 181 and a lower cover plate 182. The upper cover plate 181 and the lower cover plate 182 are respectively disposed on two sides of the frame 110 through bonding rings 184. Specifically, the upper cover plate 181 and the lower cover plate 182 are used to seal and protect the frame 110. Among them, the upper cover plate 181 and the lower cover plate 182 also have protrusions in the mass block 180 area on the side facing the frame 110 to form limit blocks 183, and the displacement of the mass block 180 in the z-axis direction is restricted by the limit blocks 183, improving the stability of the acceleration sensor 100. In some embodiments, the bonding ring 184 at one end of the upper cover plate 181 close to the gold finger 150 is connected to the low-resistance silicon 151, ensuring the flatness of the connection surface and making the connection stable.

[0036] In this embodiment, the acceleration sensor 100 is a three-axis piezoresistive acceleration sensor 100. The three-axis piezoresistive acceleration sensor 100 measures the acceleration in three axial directions through three Wheatstone bridge circuits. For the existing three-axis piezoresistive acceleration sensor 100 with a single mass block 180, there is a problem of large cross-coupling interference in the acceleration measurement between axes.

[0037] In this embodiment, the acceleration-sensitive units such as the internal elastic beams 130 and the mass block 180 in the frame 110 are arranged in central symmetry. By setting each elastic beam 130 to include a first elastic segment and a second elastic segment perpendicular to each other, the mechanical decoupling ability of the acceleration measurement between axes is improved. The acceleration sensor 100 measures the acceleration in three axial directions through three Wheatstone bridge circuits respectively. By designing the arrangement of the piezoresistive resistors 140 on each multi-segment elastic beam 130, the electrical decoupling ability of the acceleration measurement between axes is improved. The above design can reduce the interference of cross-coupling.

[0038] The arrangement of the piezoresistive resistors 140 in this embodiment will be described below.

[0039] The three-axis piezoresistive acceleration sensor 100 includes three Wheatstone bridge circuits, and each Wheatstone bridge circuit is composed of four piezoresistors 140. In this embodiment, the piezoresistors 140 include a first piezoresistor 141, a second piezoresistor 142, a third piezoresistor 143, a fourth piezoresistor 144, a fifth piezoresistor 145, a sixth piezoresistor 146, a seventh piezoresistor 147, an eighth piezoresistor 148, a ninth piezoresistor 149, a tenth piezoresistor 1410, an eleventh piezoresistor 1411, and a twelfth piezoresistor 1412. Among them, the fifth piezoresistor 145, the ninth piezoresistor 149, and the first piezoresistor 141 are disposed on the first elastic beam 131; the sixth piezoresistor 146, the tenth piezoresistor 1410, and the second piezoresistor 142 are disposed on the second elastic beam 132; the seventh piezoresistor 147, the eleventh piezoresistor 1411, and the third piezoresistor 143 are disposed on the third elastic beam 133; the eighth piezoresistor 148, the twelfth piezoresistor 1412, and the fourth piezoresistor 144 are disposed on the fourth elastic beam 134. Specifically, the initial resistance values of the above twelve piezoresistors 140 are the same, and each piezoresistor 140 has the same linear characteristic. When subjected to the same stress, the resistance values of the piezoresistors 140 change in the same way.

[0040] Among them, the acceleration sensor 100 further includes a plurality of conductive leads 171. The conductive leads 171 are arranged on the elastic beam 130, and one end of each conductive lead 171 is further connected to a gold finger 150. Each piezoresistor 140 is disposed on the conductive lead 171, and a preset circuit is formed through the conductive lead 171. Among them, the fifth piezoresistor 145, the third piezoresistor 143, the fourth piezoresistor 144, and the sixth piezoresistor 146 form a first Wheatstone bridge circuit 161 to measure the acceleration in the z-axis upward direction. The first piezoresistor 141, the second piezoresistor 142, the seventh piezoresistor 147, and the eighth piezoresistor 148 form a second Wheatstone bridge circuit 162 to measure the acceleration in the x-axis upward direction. The eleventh piezoresistor 1411, the ninth piezoresistor 149, the tenth piezoresistor 1410, and the twelfth piezoresistor 1412 form a third Wheatstone bridge circuit 163 to measure the acceleration in the y-axis upward direction. Further, low-resistance silicon 151 is fabricated at the head and tail of the piezoresistor 140, and the conductive lead 171 is connected to the low-resistance silicon 151 to electrically connect the piezoresistor 140.

[0041] In this embodiment, for the composition of each Wheatstone bridge circuit, please refer to Figures 2 to 4 .

[0042] The fifth varistor 145 is in series with the third varistor 143, and the fourth varistor 144 is in series with the sixth varistor 146; the two sets of series resistors are connected in parallel to form a first Wheatstone bridge circuit 161; the first varistor 141 is in series with the second varistor 142, and the seventh varistor 147 is in series with the eighth varistor 148; the two sets of series resistors are connected in parallel to form a second Wheatstone bridge circuit 162; the eleventh varistor 1411 is in series with the ninth varistor 149, and the tenth varistor 1410 is in series with the twelfth varistor 1412; the two sets of series resistors are connected in parallel to form a third Wheatstone bridge circuit 163.

[0043] Specifically, according to the first Wheatstone bridge circuit 161, we have: Z_Vout = (R3·R4 - R5·R6) / ((R3 + R5)·(R4 + R6))·VDD; in the above formula, Z_Vout is the output voltage of the first Wheatstone bridge circuit 161, R3 is the resistance value of the third varistor 143, R4 is the resistance value of the fourth varistor 144, R5 is the resistance value of the fifth varistor 145, R6 is the resistance value of the sixth varistor 146, and VDD is the supply voltage. The output voltage in the z-axis direction can be calculated through the calculation formula. According to the second Wheatstone bridge circuit 162, we have: X_Vout = (R2·R7 - R1·R8) / ((R1 + R7)·(R2 + R8))·VDD; in the above formula, X_Vout is the output voltage of the second Wheatstone bridge circuit 162, R1 is the resistance value of the first varistor 141, R2 is the resistance value of the second varistor 142, R7 is the resistance value of the seventh varistor 147, R8 is the resistance value of the eighth varistor 148, and VDD is the supply voltage. The output voltage in the x-axis direction can be calculated through the calculation formula. According to the third Wheatstone bridge circuit 163, we have: Y_Vout = (R9·R10 - R11·R12) / ((R9 + R11)·(R10 + R12))·VDD; in the above formula, Y_Vout is the output voltage of the third Wheatstone bridge circuit 163, R9 is the resistance value of the ninth varistor 149, R10 is the resistance value of the tenth varistor 1410, R11 is the resistance value of the eleventh varistor 1411, R12 is the resistance value of the twelfth varistor 1412, and VDD is the supply voltage. The output voltage in the y-axis direction can be calculated through the calculation formula.

[0044] In this embodiment, the first varistor 141, the second varistor 142, the third varistor 143, and the fourth varistor 144 are respectively arranged at one end of the second elastic segment of each elastic beam 130 close to the mass block 180; the fifth varistor 145, the sixth varistor 146, the seventh varistor 147, and the eighth varistor 148 are respectively arranged at one end of the first elastic segment of each elastic beam 130 close to the frame 110; the ninth varistor 149, the tenth varistor 1410, the eleventh varistor 1411, and the twelfth varistor 1412 are respectively arranged at one end of the first elastic segment of each elastic beam 130 close to the second elastic segment. In addition, the varistors 140 on two adjacent elastic beams 130 are symmetrically arranged; the varistors 140 on two opposite elastic beams 130 are centrosymmetrically arranged. Specifically, the initial resistance value of each varistor 144 is r. When the mass block 180 is subjected to an acceleration with a positive direction along the z-axis and a magnitude of a z , the stress on the varistor 140 is T z , and Δr z is the resistance change of the varistor 140 under the stress T z . In addition, within the z-axis acceleration measurement range, Δr z / r and a z have an approximately linear relationship. When the mass block 180 is subjected to an acceleration with a positive direction along the x-axis and a magnitude of a x , the stress on the varistor 140 is T x , and Δr x is the resistance change of the varistor 140 under the stress T x . In addition, within the x-axis acceleration measurement range, Δr x / r and a x have an approximately linear relationship. When the mass block 180 is subjected to an acceleration with a positive direction along the y-axis and a magnitude of a y , the stress on the varistor 140 is T y , and Δr y is the resistance change of the varistor 140 under the stress T y . In addition, within the y-axis acceleration measurement range, Δr y / r and a y have an approximately linear relationship.

[0045] Among them, when the mass block 180 has accelerations in different axial directions, causing different stresses on each varistor 140, the resulting resistance value changes are shown in the following table:

[0046] Table 1

[0047] T R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 <![CDATA[T z > <![CDATA[+Δr z1 > <![CDATA[+Δr z2 > <![CDATA[+Δr z3 > <![CDATA[+Δr z4 > <![CDATA[-Δr z5 > <![CDATA[-Δr z6 > <![CDATA[-Δr z7 > <![CDATA[-Δr z8 > <![CDATA[+Δr z9 > <![CDATA[-Δr z10 > <![CDATA[+Δr z11 > <![CDATA[-Δr z12 > <![CDATA[T x > <![CDATA[-Δr x1 > <![CDATA[+Δr x2 > <![CDATA[-Δr x3 > <![CDATA[+Δr x4 > <![CDATA[+Δr x5 > <![CDATA[-Δr x6 > <![CDATA[+Δr x7 > <![CDATA[-Δr x8 > <![CDATA[-Δr x9 > <![CDATA[-Δr x10 > <![CDATA[-Δr x11 > <![CDATA[-Δr x12 > <![CDATA[T y > <![CDATA[+Δr y1 > <![CDATA[+Δr y2 > <![CDATA[-Δr y3 > <![CDATA[-Δr y4 > <![CDATA[-Δr y5 > <![CDATA[-Δr y6 > <![CDATA[+Δr y7 > <![CDATA[+Δr y8 > <![CDATA[+Δr y9 > <![CDATA[+Δr y10 > <![CDATA[-Δr y11 > <![CDATA[-Δr y12 >

[0048] The relationships shown in the above table are the changes in the resistance values of the piezoresistors 140 when subjected to positive acceleration along each axis. The '+' indicates that the resistance value of the piezoresistor 140 increases after being stressed, and the '-' indicates that the resistance value of the piezoresistor 140 decreases after being stressed. If the mass 180 has an opposite acceleration, the signs of the above resistance value changes are opposite.

[0049] In this embodiment, the third piezoresistor 143, the fourth piezoresistor 144, the fifth piezoresistor 145, and the sixth piezoresistor 146 are the first type of piezoresistors; the first piezoresistor 141, the second piezoresistor 142, the seventh piezoresistor 147, and the eighth piezoresistor 148 are the second type of piezoresistors; the ninth piezoresistor 149, the tenth piezoresistor 1410, the eleventh piezoresistor 1411, and the twelfth piezoresistor 1412 are the third type of piezoresistors. The first type of piezoresistor, the second type of piezoresistor, and the third type of piezoresistor are the same.

[0050] For the piezoresistors 140 arranged symmetrically as described above, and each piezoresistor 140 having the same initial resistance value and resistance change law, when the mass 180 is subjected to an acceleration in the positive direction of the z-axis with a magnitude of a z , the resistance value changes of the piezoresistors 140 have the following relational expressions:

[0051] Δr z1 ≈Δr z2 ≈Δr z3 ≈Δr z4 =Δr1;

[0052] Δr z5 ≈Δr z6 ≈Δr z7 ≈Δr z8 =Δr2;

[0053] Δr z9 ≈Δr z10 ≈Δr z11 ≈Δr z12 =Δr3;

[0054] Combined with the output voltage formulas of the first Wheatstone bridge circuit 161, the second Wheatstone bridge circuit 162, and the third Wheatstone bridge circuit 163, respectively, we can obtain: X_ Vout ≈0; Y_Vout≈0. Additionally, since within the z-axis acceleration measurement range, Δr z / r and a z have an approximately linear relationship, the output voltage of the first Wheatstone bridge circuit 161 is linearly related to the z-axis acceleration; the output voltages of the second Wheatstone bridge circuit 162 and the third Wheatstone bridge circuit 163 are approximately independent of the z-axis acceleration.

[0055] When the mass block 180 is subjected to an acceleration with a magnitude of a in the positive x-axis direction, the resistance changes of the piezoresistors 140 have the following relationships: x ;

[0056] Δr x1 ≈Δr x2 ≈Δr x3 ≈Δr x4 =Δr4;

[0057] Δr x5 ≈Δr x6 ≈Δr x7 ≈Δr x8 =Δr5;

[0058] Δr x9 ≈Δr x10 ≈Δr x11 ≈Δr x12 =Δr6;

[0059] Combined with the output voltage formulas of the first Wheatstone bridge circuit 161, the second Wheatstone bridge circuit 162, and the third Wheatstone bridge circuit 163, we can respectively obtain: Z_Vout≈0;

[0060] Y_Vout≈

[0061] 0; Y_Vout≈0. Additionally, since within the x-axis acceleration measurement range, Δr x / r and a x have an approximately linear relationship, the output voltage of the second Wheatstone bridge circuit 162 is linearly related to the x-axis acceleration; the output voltages of the first Wheatstone bridge circuit 161 and the third Wheatstone bridge circuit 163 are approximately independent of the x-axis acceleration.

[0062] When the mass block 180 is subjected to an acceleration with a magnitude of a in the positive y-axis direction, the resistance changes of the piezoresistors 140 have the following relationships: y ;

[0063] Δr y1 ≈Δr y2 ≈Δr y3 ≈Δr y4 =Δr7;

[0064] Δr y5 ≈Δr y6 ≈Δr y7 ≈Δr y8 =Δr8;

[0065] Δr y9 ≈Δr y10 ≈Δr y11≈Δr y12 = Δr9;

[0066] Combining the output voltage formulas of the first Wheatstone bridge circuit 161, the second Wheatstone bridge circuit 162, and the third Wheatstone bridge circuit 163, we can respectively obtain: Z_Vout≈0; X_Vout≈0; In addition, since within the y-axis acceleration measurement range, Δr y / r and a y have an approximately linear relationship, the output voltage of the third Wheatstone bridge circuit 163 is linearly related to the y-axis acceleration; the output voltages of the first Wheatstone bridge circuit 161 and the second Wheatstone bridge circuit 162 are approximately independent of the y-axis acceleration.

[0067] In this embodiment, the arrangement of the piezoresistors 140 on the bending elastic beam 130 is such that when the piezoresistors 140 are stressed, the absolute values of the resistance changes of the symmetrically distributed piezoresistors 140 are the same, which can simplify the output voltage formula, and the influence of the cross-axis acceleration on the output voltage of the measured axial acceleration is approximately zero. The output voltage of the first Wheatstone bridge circuit 161 is only related to the z-axis acceleration; the output voltage of the second Wheatstone bridge circuit 162 is only related to the x-axis acceleration; the output voltage of the third Wheatstone bridge circuit 163 is only related to the y-axis acceleration, having very low cross-axis coupling interference. As described above, through the setting of the bent elastic beam 130 and the distribution of the piezoresistors 140 on the elastic beam, the designs of the first type of piezoresistor, the second type of piezoresistor, and the third type of piezoresistor are the same. In some other embodiments, the first type of piezoresistor, the second type of piezoresistor, and the third type of piezoresistor can also be three different piezoresistors, without specific limitation.

[0068] Different from the prior art, the present application proposes an acceleration sensor 100. The acceleration sensor 100 is provided with a multi-segment bent elastic beam 130. The multi-segment bent elastic beam 130 has a greater space utilization rate. The piezoresistors 140 on the elastic beam 130 can be in the stress concentration area, meeting the miniaturization development trend of the three-axis piezoresistive acceleration sensor 100. Moreover, since the piezoresistors 140 are located in the stress concentration area, the corresponding relationship between the resistance change of the piezoresistors 140 and the acceleration change of the mass block 180 is more accurate, improving the sensitivity and accuracy of the acceleration sensor 100. In addition, by arranging the piezoresistors 140 in the above embodiments, the output voltages of the three Wheatstone bridges are only related to the accelerations in their respective measured axes, and the cross-coupling of the acceleration measurements of each axis can be eliminated.

[0069] The above are only embodiments of the present invention, and thus do not limit the patent scope of the present invention. Any equivalent structure or equivalent principle transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. An acceleration sensor, characterized in that, Comprising: A frame having an internal space; A mass block located in the internal space; A plurality of elastic beams, each elastic beam including a first elastic section and a second elastic section connected end to end, the first elastic section and the second elastic section being arranged at an angle; one end of the elastic beam is fixed to the frame, and the other end of the elastic beam is fixed to the mass block to suspend the mass block in the internal space; A plurality of piezoresistors arranged on each elastic beam and grouped to form three Wheatstone bridge circuits for measuring accelerations in three axial directions; The piezoresistors include a first piezoresistor, a second piezoresistor, a third piezoresistor, a fourth piezoresistor, a fifth piezoresistor, a sixth piezoresistor, a seventh piezoresistor, an eighth piezoresistor, a ninth piezoresistor, a tenth piezoresistor, an eleventh piezoresistor, and a twelfth piezoresistor; The first piezoresistor, the second piezoresistor, the third piezoresistor, and the fourth piezoresistor are respectively arranged at one end of the second elastic section of each elastic beam close to the mass block; The fifth piezoresistor, the sixth piezoresistor, the seventh piezoresistor, and the eighth piezoresistor are respectively arranged at one end of the first elastic section of each elastic beam close to the frame; the fifth piezoresistor, the third piezoresistor, the fourth piezoresistor, and the sixth piezoresistor form a first Wheatstone bridge circuit for measuring the acceleration in the z-axis direction; the first piezoresistor, the second piezoresistor, the seventh piezoresistor, and the eighth piezoresistor form a second Wheatstone bridge circuit for measuring the acceleration in the x-axis direction; The ninth piezoresistor, the tenth piezoresistor, the eleventh piezoresistor, and the twelfth piezoresistor are respectively arranged at one end of the first elastic section of each elastic beam close to the second elastic section; the eleventh piezoresistor, the ninth piezoresistor, the tenth piezoresistor, and the twelfth piezoresistor form a third Wheatstone bridge circuit for measuring the acceleration in the y-axis direction; Wherein, the initial resistance values of the piezoresistors are the same, and the piezoresistors have the same linear characteristics; two adjacent elastic beams and the piezoresistors on the two adjacent elastic beams are axially symmetrically arranged, and two opposite elastic beams and the piezoresistors on the two opposite elastic beams are centrally symmetrically arranged.

2. The acceleration sensor according to claim 1, wherein The elastic beams are the first elastic beam, the second elastic beam, the third elastic beam, and the fourth elastic beam with the same shape; The first elastic beam, the second elastic beam, the third elastic beam, and the fourth elastic beam are sequentially connected around the side surface of the mass block.

3. The acceleration sensor according to claim 2, wherein Each elastic beam includes a first elastic section and a second elastic section, and the first elastic section and the second elastic section are perpendicularly arranged; wherein, one end of the first elastic section is connected to the frame, and one end of the second elastic section is connected to the mass block.

4. The acceleration sensor according to claim 3, wherein The fifth varistor, the ninth varistor and the first varistor are arranged on the first elastic beam; the sixth varistor, the tenth varistor and the second varistor are arranged on the second elastic beam; the seventh varistor, the eleventh varistor and the third varistor are arranged on the third elastic beam; the eighth varistor, the twelfth varistor and the fourth varistor are arranged on the fourth elastic beam.

5. The acceleration sensor according to claim 4, characterized in that, It further includes: A plurality of conductive leads are arranged on the elastic beam, and one end of each conductive lead is further connected to a gold finger; Each varistor is arranged on the conductive lead, and a preset circuit is formed through the conductive lead.

6. The acceleration sensor according to claim 5, wherein The fifth varistor is connected in series with the third varistor, and the fourth varistor is connected in series with the sixth varistor; two groups of series resistors are connected in parallel to form the first Wheatstone bridge circuit; The first varistor is connected in series with the second varistor, and the seventh varistor is connected in series with the eighth varistor; two groups of series resistors are connected in parallel to form the second Wheatstone bridge circuit; The eleventh varistor is connected in series with the ninth varistor, and the tenth varistor is connected in series with the twelfth varistor; two groups of series resistors are connected in parallel to form the third Wheatstone bridge circuit.

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