JP2011209270A - Angular velocity sensor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an angular velocity sensor element of higher output sensitivity available for angular velocity sensors used on various electronics.SOLUTION: This invented angular velocity sensor element is designed so that shape of its first drive arm 11a and second drive arm 11b may be a folding-back structure of arm sides extending in the direction perpendicular to vibrational direction of a spindle 10. According to this structure, amount of displacement towards vibrational direction of these first and second drive arms will increase, thereby the angular velocity sensor element of higher output sensitivity can be provided.

Description

  The present invention relates to an angular velocity sensor element used in various electronic devices.

  A conventional angular velocity sensor element of this type is configured as shown in FIG.

  FIG. 11 is a top view of a conventional angular velocity sensor element.

  In FIG. 11, arms 2a and 2b provided in a cross direction with the fixed portion 1 as the center, and a pair of arms 2a arranged symmetrically among the four arms 2a and 2b are used as detection arms 2a, and the remaining pair of arms 2b. Is provided as a support arm 2b, and a drive arm 3 is provided at the tip of the support arm 2b, and the drive arm 3 is vibrated as indicated by an arrow, so that an angular velocity is applied to the drive arm 3 to exert a Coriolis force. Is transmitted to the detection arm 2a via the arm 2b, and the detection arm 2a is vibrated in the direction indicated by the arrow, and the structure in which the deflection of the detection arm 2a due to this vibration is converted into an electrical signal and output is known. It has been.

  As prior art document information related to the invention of this application, for example, Patent Document 1 is known.

Japanese Patent Laid-Open No. 2003-337025

  However, since the above-described conventional angular velocity sensor element has a cantilever structure in which the central portion of the drive arm 3 is fixed to the support arm 2b, the distal end portion of the support arm 2b serving as the vibration base point of the drive arm 3 and the drive arm 3 has a problem that the amount of deformation from the tip portion of the three is reduced, and the output sensitivity of the angular velocity sensor element is thereby reduced.

  The present invention solves the above-described conventional problems, and an object thereof is to provide an angular velocity sensor element having high output sensitivity.

  In order to achieve the above object, the present invention has the following configuration.

  According to the first aspect of the present invention, a pair of fixed portions, a first drive arm having one end supported by one of the pair of fixed portions, and one end of the other fixed portion. A second drive arm supported and connected to the first drive arm; a weight portion supported on the other end of the first drive arm and the second drive arm; and the pair of fixed portions Are provided on one or both of the connecting portion for connecting both the first driving arm and the second driving arm, and the weight portion is driven to vibrate in a direction connecting the fixed portion and the weight portion. Coriolis force generated in the first drive arm and the second drive arm provided on one or both of the drive electrode provided with the piezoelectric layer and the first drive arm and the second drive arm. A detection electrode provided with a piezoelectric layer for detection; The driving arm and the second driving arm have a folded-back structure of arm sides extending in a direction perpendicular to the vibration direction of the weight portion. According to this configuration, the first driving arm and the second driving arm Since the arm has a folded-back structure that extends in a direction perpendicular to the vibration direction of the weight portion, the displacement amount of the first drive arm and the second drive arm in the vibration direction is increased, thereby increasing the output. The effect is that sensitivity is increased.

  In the invention according to claim 2 of the present invention, in particular, when the temperature around the angular velocity sensor changes, the elastic portion is provided in each of the pair of fixed portions, so that the elastic portion is elastically deformed. Since the tensile stress is not applied to the fixed part other than the part, the increase in the driving frequency and detection frequency of the angular velocity sensor element due to temperature change is about the same, and as a result, the detuning frequency is difficult to change. This has the effect that the output signal of the angular velocity sensor does not fluctuate.

  In the invention according to claim 3 of the present invention, in particular, since the elastic portion is provided in the vicinity of the hole by providing the hole in each of the pair of fixing portions, the elastic portion is elastically deformed, and thereby the elastic portion Since no tensile stress is applied to any other fixed part, the increase in the drive frequency and detection frequency of the angular velocity sensor element due to temperature change is about the same, and as a result, the detuned frequency is less likely to change. The output signal of the angular velocity sensor does not fluctuate, and since the pair of fixing portions can be securely fixed to the ASIC at locations other than the holes of the pair of fixing portions, the strength for fixing the angular velocity sensor element to the ASIC is high. It has the effect of improving.

  As described above, the angular velocity sensor element of the present invention includes a pair of fixed portions, a first drive arm whose one end is supported by one of the pair of fixed portions, and one end at the other fixed portion. Is supported, the second drive arm is connected to the first drive arm, the weight is supported at the other end of the first drive arm and the second drive arm, and the pair of fixings. Drive the vibration of the weight part in the direction connecting the fixed part and the weight part, provided on one or both of the connecting part for connecting both of the parts and the first drive arm and the second drive arm. Coriolis force generated in the first driving arm and the second driving arm provided on one or both of the driving electrode provided with the piezoelectric layer to be driven and the first driving arm and the second driving arm. And a detection electrode provided with a piezoelectric layer for detecting The shape of the first drive arm and the second drive arm is a folded structure of arm sides extending in a direction orthogonal to the vibration direction of the weight portion. According to this configuration, the first drive arm and Since the shape of the second drive arm is a folded structure of the arm side extending in the direction orthogonal to the vibration direction of the weight portion, the displacement amount of the first drive arm and the second drive arm in the vibration direction increases. Thereby, an angular velocity sensor element having a high output sensitivity can be provided.

1 is an exploded perspective view showing an angular velocity sensor using an angular velocity sensor element according to Embodiment 1 of the present invention. Top view of the same angular velocity sensor element Schematic diagram showing the drive vibration state of the same angular velocity sensor element Schematic diagram showing the detected vibration state of the same angular velocity sensor element Schematic diagram showing the principle of electrode expansion and contraction provided in the same angular velocity sensor element Schematic diagram showing the driving principle of the same angular velocity sensor element Schematic diagram showing the detection principle of the same angular velocity sensor element The top view of the angular velocity sensor element in Embodiment 2 of this invention Top view showing a state where the elastic part of the angular velocity sensor element is deformed Top view showing an example of another angular velocity sensor element in the second embodiment Schematic diagram of conventional angular velocity sensor element

(Embodiment 1)
Hereinafter, the angular velocity sensor element according to Embodiment 1 of the present invention will be described with reference to the drawings.

  FIG. 1 is an exploded perspective view showing an angular velocity sensor using the angular velocity sensor element according to Embodiment 1 of the present invention, and FIG. 2 is a top view of the angular velocity sensor element.

  1 and 2, the basic structure of an angular velocity sensor using an angular velocity sensor element is an angular velocity sensor element 5 in a package 4, a drive control circuit for applying a drive signal to the angular velocity sensor element 5, and an output from the angular velocity sensor element 5. An ASIC 6 including a detection circuit for processing the detected signal is arranged, and the opening of the package 4 is sealed with a lid 7. The ASIC 6 and the angular velocity sensor element 5 are attached to the package 4 via a TAB tape 8 for anti-vibration measures.

  As shown in FIG. 2, the angular velocity sensor element 5 is a first fixing portion 9a, and the first fixing portion 9a is connected to the second fixing portion 9b by a connecting portion 9c. The weight portions 10 are symmetrically arranged on both sides of the first fixed portion 9a and the second fixed portion 9b, and the weight portions 10 are respectively connected to the first drive arm 11a and the second drive arm 11b. It has a connected shape, and a drive electrode 12 described later is provided on the first drive arm 11a. On the other hand, the drive electrode 12, the detection electrode 13, and the monitor electrode 14 are appropriately disposed on the second drive arm 11b, and the pad electrode 15 and the connection wiring provided on the first fixed portion 9a and the second fixed portion 9b. 16 is connected. Each of the first drive arm 11a and the second drive arm 11b has a direction (Y-axis) orthogonal to the direction (X-axis direction) connecting the first fixed part 9a and the second fixed part 9b and the weight part 10 (Y-axis). The arm side is folded back in the direction).

  Then, the drive signal formed by the ASIC 6 is applied to the drive electrode 12 via the pad electrode 15 and the connection wiring 16 so that the weight portion 10 expands and contracts in the X-axis direction as shown in FIG. In this driving vibration state, a Coriolis force is generated by receiving an angular velocity having a rotation axis in a direction (Z-axis direction) perpendicular to the substrate surface (XY plane) of the angular velocity sensor element 5 in this driving vibration state. The drive arm 11a and the second drive arm 11b vibrate in the Y-axis direction as shown in FIG. 4, and the deformation of the first drive arm 11a and the second drive arm 11b due to this detected vibration is shown in FIG. The detection electrode 13 shown in FIG. 2 converts the detection signal into an electrical signal, and outputs the detection signal to the ASIC 6 via the connection wiring 16 and the pad electrode 15. The monitor electrode 14 is provided to detect the amplitude and drive period of the drive arm 11 and feed back the information to the ASIC 6 to control the drive signal and the detection signal.

  The angular velocity sensor element 5 has a structure in which a drive electrode 12, a detection electrode 13, a monitor electrode 14 and the like are provided on a substrate made of Si, and each electrode structure is Pt provided on a substrate 17 as shown in FIG. A laminated electrode comprising a lower electrode 18 made of, a piezoelectric layer 19 made of PZT provided on the lower electrode 18, and an upper electrode 20 made of Au provided on the piezoelectric layer 19. When a positive voltage is applied to the upper electrode 20 with the electrode 18 connected to the ground, a compressive force acts in the electrode stacking direction, and the substrate 17 extends in the in-plane direction. On the other hand, when a negative voltage is applied to the upper electrode 20, a tensile force acts in the electrode stacking direction, and the substrate 17 contracts in the in-plane direction. Further, as a reverse phenomenon, if the first drive arm 11a and the second drive arm 11b are bent and the piezoelectric layer 19 is contracted, a negative voltage is generated, and if the piezoelectric layer 19 is extended, a positive voltage is generated. . Although not particularly shown between the upper electrode 20 and the piezoelectric layer 19 and between the lower electrode 18 and the piezoelectric layer 19, there is an adhesion layer (not shown) made of Ti in order to increase the adhesion between the layers. Intervene.

  When the angular velocity sensor element 5 is driven, as shown in FIG. 6, the arm sides connected to the weight portion 10 side are vertically and horizontally centered as indicated by alternate long and short dashed lines 21a and 21b (the longitudinally centered axis is A central axis 21a in the extending direction of the arm side, and a horizontal central axis is defined as a central axis 21b orthogonal to the extending direction including the bending inflection point of the arm side). Then, the drive electrode 12 is disposed on the side close to the weight portion 10 and the diagonal position thereof, and is controlled so that a drive signal having the same potential is applied thereto. Occurs and stretches, and the arm side bends in an S-shape. On the other hand, if a negative voltage is applied, tensile stress is generated and shrinkage occurs, and the arm side tends to bend in the opposite direction to the case where a positive voltage is applied. Is something you can do.

  The first drive arm 11a and the second drive arm 11b have a folded-back structure on the arm side perpendicular to the vibration direction of the weight portion 10, and the first drive arm 11a and the second drive arm are bent by the bending of the arm side. By securing the amplitude of 11b, a larger amplitude than that of the drive arm 3 having the conventional cantilever structure shown in FIG. 11 is obtained, and the arm side extends in a direction perpendicular to the vibration direction. Since each arm side is bent and vibrated, the structure is easy to receive Coriolis force. As a result, the detection level of the angular velocity sensor element 5 is improved.

  Further, in forming the detection signal from the detection vibration shown in FIG. 4 in the angular velocity sensor element 5, the position where the detection electrode 13 is eccentric with respect to the central axis 22a in the extending direction of the arm side as shown in FIG. By arranging in the position, the deflection component of the arm side due to the Coriolis force can be efficiently converted into an electric signal.

  That is, as shown in FIG. 4, the arm sides constituting the first drive arm 11a and the second drive arm 11b bend like a bow when an angular velocity is applied. If a detection signal must be formed and the detection electrode 13 is provided eccentrically to the right side of the central axis 22a of the arm side as shown in FIG. Since a force that stretches the detection electrode 13 is applied to the right half of the arm, a positive voltage is induced, and when the arm side is bent to the right side in the figure, a force that contracts the detection electrode 13 is applied to the right half of the arm side. Is induced.

  Further, since the first drive arm 11 a and the second drive arm 11 b have the arm side folding structure, the first drive arm 11 a and the second drive arm 11 b are connected to the single weight portion 10. The direction of drive vibration can be improved by making the first drive arm 11a symmetrical with the second drive arm 11b. Note that the drive electrodes 12 provided on the first drive arms 11a and the second drive arms 11b are similarly arranged symmetrically, so that the direction of drive vibration can be further improved.

  Furthermore, in the angular velocity sensor element according to the first embodiment of the present invention, the first fixing portion 9a and the second fixing portion 9b are connected by the connecting portion 9c, so that the angular velocity does not act on the angular velocity sensor element. In this case, the first drive arm 11a and the second drive arm 11b can be prevented from moving in the direction in which the Coriolis force, which is the direction perpendicular to the drive direction, is generated.

  In the above-described angular velocity sensor, the structure in which the laminated electrode using PZT is arranged on the substrate 17 made of Si as the angular velocity sensor element 5 has been described. However, the substrate 17 is configured by a piezoelectric body such as quartz. Even in the structure in which the opposing electrode is formed on the 17 opposing surfaces, the amplitude of the drive vibration in the angular velocity sensor element 5 can be increased, and the same effect can be achieved without changing the configuration in which the detection level is increased.

(Embodiment 2)
Hereinafter, the angular velocity sensor element according to the second embodiment of the present invention will be described with reference to the drawings.

  FIG. 8 is a top view of the angular velocity sensor element according to the second embodiment of the present invention.

  The same components as those in FIG. 2 of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  2 is different from FIG. 2 of the first embodiment in that the first elastic portion 33 is provided in the vicinity of the first hole 32 by providing the first hole 32 in the first fixing portion 31, and the second The second elastic portion 36 is provided in the vicinity of the second hole 35 by providing the second hole 35 in the fixing portion 34 of the second fixing portion 34.

  Here, the case where the temperature around the angular velocity sensor changes from 25 ° C. to −40 ° C. is considered. As shown in FIG. 1, when the angular velocity sensor element 5 is fixed to the ASIC 6 in Embodiment 1 of the present invention, the angular velocity sensor element 5 is more than the ASIC 6 due to the difference in thermal expansion coefficient between the angular velocity sensor element 5 and the ASIC 6. It contracts greatly. Then, tensile stress is applied to the first fixed portion 9a and the second fixed portion 9b in the angular velocity sensor element 5. As shown in (Table 1), the driving frequency fd of the angular velocity sensor element 5 increases by about 107 Hz, while the detected frequency fs increases by 33 Hz. Therefore, the detuning frequency Δf of the angular velocity sensor element 5 changes by 74 Hz. Due to the change in the detuning frequency Δf, the output signal of the angular velocity sensor changes.

  In the angular velocity sensor element according to the second embodiment of the present invention, the first elastic portion 33 is provided in the vicinity of the first hole 32 by providing the first hole 32 in the first fixing portion 31, and the second Since the second elastic portion 36 is provided in the vicinity of the second hole 35 by providing the second hole 35 in the fixing portion 34, the first elastic portion 33 and the second elastic portion 33 are provided as shown in FIG. Since the portion 36 is elastically deformed, tensile stress is not applied to the first fixing portion 31 and the second fixing portion 34 other than the first elastic portion 33 and the second elastic portion 36 (Table As shown in 2), the increase in the driving frequency of the angular velocity sensor element 5 is 107 Hz, while the increase in the detection frequency is 94 Hz, both increases being similar.

  As a result, since the change in the detuning frequency Δf is as small as 12 Hz, the amount of change in the output signal of the angular velocity sensor with respect to the temperature change is small, and the first fixed portion 31 other than the first hole 32 and the first Since the first fixing portion 31 and the second fixing portion 34 can be reliably fixed to the ASIC 6 at a place other than the second hole 35 of the second fixing portion 34, the angular velocity sensor element 5 is fixed to the ASIC 6. This has the effect of improving the strength to be improved.

  In the angular velocity sensor element 5 according to the second embodiment of the present invention, the first elastic portion 33 is provided in the vicinity of the first hole 32 by providing the first hole 32 in the first fixing portion 31. The second elastic portion 36 is provided in the vicinity of the second hole 35 by providing the second hole 35 in the second fixing portion 34. However, as shown in FIG. In addition to providing the first elastic portion 39 by providing the notched portion 38 in 37, providing the second elastic portion 42 by providing the notched portion 41 in the second fixing portion 40 has the same effect. Is.

  The present invention has an effect of increasing the detection level of the angular velocity sensor element, and is particularly useful as an angular velocity sensor element used for an angular velocity sensor that requires a small and highly sensitive characteristic such as a navigation system.

9a, 31, 37 First fixed portion 9b, 34, 40 Second fixed portion 9c Connecting portion 10 Weight portion 11a First drive arm 11b Second drive arm 12 Drive electrode 13 Detection electrode 19 Piezoelectric layer

Claims (3)

A pair of fixed portions, a first drive arm having one end supported by one of the pair of fixed portions, and one end supported by the other fixed portion and connected to the first drive arm. A second driving arm provided; a weight portion supported by the other ends of the first driving arm and the second driving arm; a connecting portion that connects both the pair of fixing portions; and the first A drive electrode provided with a piezoelectric layer provided on one or both of the drive arm and the second drive arm and configured to drive and vibrate the weight portion in a direction connecting the fixed portion and the weight portion; A detection electrode provided on one or both of the first drive arm and the second drive arm and provided with a piezoelectric layer that detects Coriolis force generated in the first drive arm and the second drive arm; The first drive arm and the second drive arm. Angular velocity sensor which has a folded structure of the arm side extending arm of the shape in the direction orthogonal to the vibration direction of the weight portion. The angular velocity sensor element according to claim 1, wherein an elastic portion is provided in each of the pair of fixed portions. The angular velocity sensor element according to claim 2, wherein an elastic part is provided in the vicinity of the hole by providing a hole in each of the pair of fixed parts.

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