JP3998049B2 - Motion sensor vibrator and vibratory gyroscope - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a structure of a motion sensor vibrating body for a gyroscope that detects angular velocity using Coriolis force acting on the vibrating body, a structure of a motion sensor vibrating body for an accelerometer that detects linear acceleration acting on the vibrating body, The present invention also relates to a configuration of a vibration gyroscope in which a motion sensor vibrating body for a gyroscope and a detection circuit are combined.
[0002]
[Prior art]
Conventionally, various vibrators having various vibration modes have been proposed as motion sensor vibrators for vibration gyroscopes (hereinafter simply referred to as gyro sensor vibrators or simply vibrators). FIG. 6 shows an example of a tuning fork type gyro sensor vibrating body as a first conventional example. (A) is a top view, (b), (c) is sectional drawing of the electrode part of a vibration leg, and has shown electrode arrangement | positioning and connection. The tuning fork type vibrating body has two straight cantilevered vibrating legs 1R and 1L arranged in parallel and connected at one end to the base 9, and has a symmetry axis SA (three-dimensional symmetry plane). However, the tuning fork should be considered as a plane and set as an axis) to make a symmetric fundamental vibration (steady vibration to induce Coriolis force). The material is quartz, and the whole is enclosed in a vacuum container (not shown). (Hereinafter, other examples including the present invention are basically the same.)
[0003]
UR and UL are additional masses 5R and 5L provided as necessary near the free ends 4R and 4L of the legs during vibration (for example, thick-plated gold or bonded weight objects, etc. Is the maximum velocity vector at a certain moment of the center of gravity GR, GL. When the tuning fork rotates around a rotation axis parallel to the symmetry axis SA, Coriolis forces FR and FL proportional to the angular velocity Ω are generated in opposite directions in the direction perpendicular to the tuning fork plane (paper surface) on each vibrating leg. (Coriolis force is perpendicular to the velocity and angular velocity vectors). Excitation and detection are performed piezoelectrically.
[0004]
6C, 6R is a film-like excitation electrode for applying an alternating voltage that sustains the fundamental vibration, and is provided on the four side surfaces of the leg spring portion 3R. A lead pattern 10 made of a conductive film (not shown in the plan view). ) And led to the excitation terminal 8V on the base 9. Also, (b) 7L is a film-like detection electrode provided on the front and back surfaces of the leg spring portion 3L, detects the distortion of the spring portion based on the Coriolis force, and is guided to the detection terminal 8D on the base 9. The excitation electrode and the detection electrode are originally provided for each vibration leg, but the positions where the piezoelectric effect is high are close to the fixed ends 2R and 2L of the vibration leg and overlap each other, so that they are distributed to the legs. The detection electrode 7L may be provided on both side surfaces of the spring portion 3L, or there may be an example in which the excitation electrode and the detection electrode are provided at different locations on a common leg.
[0005]
7A and 7B show a gyro sensor vibrating body as a second conventional example, in which FIG. 7A is a plan view and FIG. 7B is a sectional view of a vibrating leg. This vibrating body has an L-shaped vibrating leg obtained by deforming a tuning fork, and also has a plane shape and a vibration mode that are line-symmetric. The symbols of the respective parts are the same as in the first conventional example. The vibration legs 1R and 1L are connected to the base 9 at the fixed ends 2R and 2L in the same manner as the tuning fork. Two long straight rod-like spring portions 3R and 3L arranged in parallel, and their free ends 4R and 4L have outwardly protruding portions, and additional masses 5R and 5L eccentric from the spring axis at this place Have The purpose of the additional mass is to detect the Coriolis force and to adjust the natural frequency to an appropriate low frequency. The vibrating body is excited by the excitation electrodes 6R and 6L, and is suitable for detecting an angular velocity of a rotational motion (in-plane rotation) parallel to the plane of the vibrating body.
[0006]
When the entire vibrating body together with the base 9 rotates at an angular velocity Ω around a rotation axis perpendicular to the surface, the Coriolis forces FR and FL are reversed in the plane according to the speeds UR and UL of the center of gravity of the additional masses 5R and 5L. appear. The moments generated in the spring portions 3R, 3L of the vibrating legs by both Coriolis forces act so that one of them increases the deflection due to the excitation and the other decreases, and the detection voltage due to the piezoelectric effect is applied to the excitation electrodes 6R, 6L. It is superimposed on the excitation voltage. Therefore, the excitation terminal of each leg, two 8V are input to the differential amplifier (not shown), the excitation voltage is canceled and the Coriolis force detection voltage is added, and synchronous detection is performed to detect the excitation voltage and the Coriolis force. The detection voltage can be separated and the angular velocity can be measured.
[0007]
[Problems to be solved by the invention]
The tuning fork of the first conventional example exhibits excellent characteristics with respect to the excited fundamental vibration. Although it is necessary to adjust the natural frequency of each vibration leg equally, there is an advantage that the work is easy because there are only two vibration legs. However, rotation in the tuning fork plane cannot be detected. Therefore, a tuning fork must be placed in order to detect motion in a horizontal plane, and this tends to be an obstacle to obtaining a thin gyro sensor in many applications. In addition, since the highly efficient positions of the excitation electrode and the detection electrode overlap as described above, it is difficult to separately arrange the two types of electrodes on the same vibration leg. Further, the structure of the detection electrode 7L for detecting the out-of-plane vibration of the vibrating leg cannot obtain high sensitivity as compared with the configuration using the four surfaces of the vibrating leg.
[0008]
The vibrating body of the second conventional example has an advantage that it can detect the in-plane rotation. However, the fundamental vibration that is excited does not balance the inertial force. The tip of the vibrating leg is a center of rotation CR, CL (about 27% of the length from the fixed end to the free end if the additional mass is ignored, and the spring portion 3R, 3L on the spring axis line) If the mass is ignored, the position is calculated as 1/3 of the total length from the fixed end, that is, the position is generally about 30%). Accordingly, the inertial forces of the additional masses 5R and 5L at the positions of the eccentric gravity centers GR and GL remain without canceling out the components in the direction of the symmetry axis SA, shake the base 9, cause vibration leakage, and lower the Q value of the vibrating body. . Increasing the eccentricity of the additional mass (increasing the arm length of the moment) in an attempt to increase the detection sensitivity of the Coriolis force becomes more serious, and a sufficient amplitude cannot be obtained.
[0009]
In addition, the balance condition of the vibration inertia force of the vibrating body in which the plurality of vibrating legs are opened / closed and bent / vibrated substantially symmetrically in one plane is generally expressed. A common tangent line can be drawn on the vibration trajectory of the vibration mass of each leg (if the additional mass is large, it comes close to the center of gravity of the additional mass) (this is a short arc because of the rotational motion as described above). In other words, the inertial force of each leg is on the same line of action and the direction is opposite), in other words, the position of the center of gravity is at the same height along the axis of symmetry, and the radius of gravity of the center of gravity is parallel to the axis of symmetry. It is to become. Under this condition, the shape of the vibrating leg itself may be asymmetric.
[0010]
Further, since the excitation moment and the moment generated by the Coriolis forces FR and FL in the respective spring portions are in the same direction, the piezoelectric effect due to both overlaps, making it difficult to separate the excitation and detection electrodes as described above. Although it is possible in principle to separate circuit signals, the detection voltage of Coriolis force is small, so the excitation signal that remains without being canceled and the voltage generated by the piezoelectric effect of the fundamental vibration become large noise, which increases detection accuracy. High potential for adverse effects. Also, considering the moment that the Coriolis forces FR and FL facing the radial directions rR and rL make on the cross section of the spring portions 3R and 3L, the arm length of the moment becomes zero near the rotation centers CR and CL, and the arm length before and after that The sign of is even reversed. Therefore, the Coriolis force can generate an effective spring distortion that causes the piezoelectric effect only in a part of the electrode area (a part relatively close to the free end having a large arm length). It is thought that only low sensitivity can be obtained.
[0011]
There is also a problem with the material of the vibrating body. Conventionally, the materials of various vibrators are piezoelectric single crystals or porcelains appropriately polarized after forming. When a metal constant elastic material is used, the piezoelectric element is bonded to the surface. These have strong piezoelectricity and do not require vacuum sealing, but the product accuracy is unstable. In order to stabilize the product characteristics and improve the detection accuracy, it is preferable to use a single crystal material. Artificial quartz materials are particularly desirable (as they have been successfully applied to tuning fork vibrators for wristwatches). They are excellent in the Q value and temperature characteristics of basic vibrations, can be processed by etching, and are extremely desirable. It is considered that the cut angle (relative to the crystal axis) at which the piezoelectricity is relatively weak and good characteristics are obtained is limited, and it is still applied only to special sensor vibrating bodies. Single crystal materials other than quartz are not fully used and expensive.
[0012]
In addition, other issues in motion detection are addressed. Part 1 is a motion sensor vibrating body for an accelerometer. When the tuning fork mentioned in the conventional example is used without excitation, a voltage proportional to the acceleration in the direction perpendicular to the vibrating leg axis can be detected from the electrode 6R of the right leg 1R (the inertial force in this direction is the fundamental vibration). Therefore, a voltage proportional to the acceleration perpendicular to the tuning fork surface (in the same direction as the Coriolis force) can be detected from the electrode 7L of the left leg 1L. However, a vibration body having a simple configuration capable of detecting acceleration in two axes (two orthogonal directions) in the plane of the vibration body has not been proposed yet. Although the accelerometer is used without excitation, it is referred to as a vibrating body when the main part that senses acceleration has a shape capable of free vibration.
[0013]
The second of the other problems relates to the detection principle of a vibrating gyroscope. Conventionally, a voltage proportional to the vibration distortion due to the Coriolis force is detected in an analog manner using a piezoelectric phenomenon, and various attempts have not been made to detect an angular velocity, for example, digitally. In general, this is not preferable for the development of measurement technology.
[0014]
The main object of the present invention is to make a compact, thin, easy to manufacture, high quality of vibrating body, capable of detecting in-plane rotation of the vibrating body, capable of high sensitivity detection, and vibration suitable for use of a piezoelectric single crystal. It is providing the motion sensor vibrating body for gyroscopes. Another object is to provide a motion sensor vibrating body for an accelerometer capable of detecting acceleration in an arbitrary direction. Yet another object is to provide a vibrating gyroscope with a novel detection principle.
[0015]
In order to achieve the above main object, the motion sensor vibrator for the vibration gyroscope of the present invention has the following characteristics.
(1) It has a plurality of cantilevered vibration legs substantially in one plane, and at least one of the vibration legs follows from the fixed end to the free end. Kin Center of gravity of vibrating mass of the vibrating leg Is surrounded by each part of the vibrating leg at an angle of 270 ° or more In addition, when the plurality of vibrating legs freely vibrate in the plane, the inertial force of vibration excited so that the vibration locus of the center of gravity of the vibrating mass is substantially on the same straight line is provided. It is set so as to be substantially cancelled as a whole, and at least an excitation electrode is provided on the bent surface.
[0016]
The motion sensor vibrating body of the present invention may further include at least one of the following features.
(2) The excitation electrode is provided on four side surfaces near the fixed end of the vibrating leg, and the Coriolis force detection electrode is closer to the free end than the excitation electrode and the center of gravity of the vibration mass. Provided in at least a part of the surrounding area.
(3) The material of each vibration leg is made of a single crystal material and is bent in a polygonal line, and at least two directions of the bent part of the polygonal line are a plurality of the same kind of crystal axes of the single crystal material. An angle approximately equal to at least two of the two.
[0017]
(4) An extension line of the vibration locus of the center of gravity of the vibration mass near the free end passes through the Coriolis force detection electrode. thing.
[0018]
In order to achieve the other object, the vibrating gyroscope of the present invention has the following features.
(5) (1) above Using a sensor vibrating body, the vibration mass of the vibration part has a structure in which the radius of vibration movement changes due to the Coriolis force. Detecting the rotational angular velocity that caused the Coriolis force by changing the half cycle alternately long and short and measuring the change of the half cycle of the subsequent vibration or the time corresponding to the change.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a motion sensor vibrating body for a vibration gyroscope according to a first embodiment of the present invention, where (a) is a plan view, and (b) and (c) are vibrations also showing electrode arrangement and connection. Sectional drawing of a leg, (d) is a diagram showing a bending deformation of a vibrating leg due to fundamental vibration and Coriolis force. In this example, parts having functions similar to those of the first and second conventional examples described above are given the same symbols to avoid duplication of explanation. In addition, it is assumed that the material of the vibrating body is a quartz material (hereinafter, the same applies to other embodiments). The vibrating body is punched out of a quartz Z plate (or a Z ′ plate obtained by rotating it several times around the X axis), and the entire shape and the basic vibration state are in a plane symmetrical with respect to the symmetry axis SA which is the longitudinal direction of each leg. It is vibration. The natural frequency of each leg is equal. The direction of the symmetry axis SA is directed to one Y axis (or Y ′ axis) of the crystal axes. This is a direction in which the main spring portion exhibits a piezoelectric effect, and at the same time, the temperature change of the elastic modulus can be reduced to stabilize the frequency. The vibrator is enclosed in a vacuum container (not shown) in order to eliminate air resistance.
[0020]
The vibrating legs 1R and 1L have a shape in which the axis is greatly bent, and are arranged symmetrically with respect to the symmetry axis SA. The spring part of each leg is divided into bent parts, and is composed of 31R, 31L, 33R, and 33L from the fixed ends 2R and 2L toward the free ends 4R and 4L. Excitation electrodes 6R and 6L are provided on the four surrounding surfaces of the spring portions 31R and 31L as shown in (b), and detection electrodes 7R and 7L are provided on the four surrounding surfaces of the spring portions 33R and 33L as shown in (c). Further, the vibrating leg portions 32R and 32L are short and difficult to bend, so there is no springiness. The portions 34R and 34L have a thick cross section (leg width) to make them rigid and do not use the springiness (this portion is in the X-axis direction). There is no bending-distortion piezoelectric effect and the temperature characteristic of the elastic modulus is poor), and the portions 35R and 35L close to the free end are fixed portions of the additional masses 5R and 5L. The center of gravity GGR, GGL of the total vibration mass of each vibration leg is directly above the rotation centers CR, CL. Incidentally, when tracing from the fixed ends 2R, 2L to the free ends 3R, 3L, for example, the spring portions 32R, 32L and the portions 35R, 35L are turned and bent by 180 ° (the portions 32R, 32L are 270 °). . The center of gravity GGR, GGL of the vibrating mass is surrounded by each part of each vibrating leg at an angle of 270 ° or more.
[0021]
Next, a configuration for balancing the inertial force of the fundamental vibration to be excited will be described. In the first approximation, the center positions of the spring portions 31R and 31L are regarded as the rotation centers CR and CL, and the gravity centers GGR and GGL of the vibration mass are obtained from the mass distribution above the rotation centers CR and CL of each vibration leg. , So that it is directly above each of the rotation centers CR and CL (with the symmetry axis SA vertical) and equal height. More precisely, the shape and mass distribution of each vibrating leg is set in detail, the virtual free vibration is applied to the vibrating body, the finite element method is applied, and the calculated inertial force (the magnitude is the amplitude of each detail). In proportion to the axis of symmetry SA in the vertical direction and in the opposite direction, and the magnitude of the moment of inertia of each detail with respect to each fixed end 2R, 2L cancels out. It is good to determine the mass distribution. The correction of the mass distribution can also be performed experimentally.
[0022]
Next, a rotation detection mechanism will be described. When the vibrating body rotates in the plane, the Coriolis forces FR and FL act on the center of gravity GR and GL of the additional masses 5R and 5L of the vibrating legs in the vibrating body plane, as in the second conventional example. The action lines are the radiuses rR and rL, but the axes of the spring portions 33R and 33L provided with the detection electrodes are shifted from the center of rotation (the shift amounts are arbitrary in principle). And a sufficiently large Coriolis moment can be applied to the spring portions 33R and 33L over its entire length, and highly sensitive detection can be performed. Since the Coriolis force creates a moment in the surface of the vibrating body, it can be detected with high sensitivity using the four-surface electrodes around the legs as in the case of excitation of the basic vibration. In addition, since the detection parts 32R and 32L are different from the excitation parts 31R and 31L, respective dedicated electrodes can be provided.
[0023]
Next, the optimality of the excitation part and the detection part will be examined with reference to the diagram of FIG. For the sake of simplicity, the diagram shows only one side (right leg) that is symmetrical. The thin line is exaggerated and the thick line is exaggerated in the bending shape when excitation or Coriolis inertial force is applied. Since the spring portions 31R and 31L where the excitation electrodes are provided are located farthest from the center of gravity of the total vibration mass, the piezoelectric effect due to the moment of inertia force of the fundamental vibration is the highest, and is optimal as a site where the excitation electrodes are provided.
[0024]
Further, as described above, the four-surface electrode is possible at the spring portions 33R and 33L where the detection is performed, and the Coriolis force moment acts greatly, which is suitable for the detection. However, there is another reason. If the heights of the center of gravity GR and GL of the additional masses 5R and 5L (which are also considered by adding the masses of the vibrating legs 34R, 34L, 35R and 35L themselves) are set appropriately, the left figure of (d) Thus, the action line of inertial force of the additional mass (which is considered to be substantially coincident with the velocity vector UR of the basic vibration of the center of gravity GR) cuts the center of the length of the spring portion 33R (of the electrode portion). Therefore, the moment generated by the inertial force of the additional mass 5R in the spring portion 33R is opposite in the upper half and the lower half of the spring portion (the bending of the diagram is reversed), the piezoelectric effect is canceled out, and the detection electrode 7R has a basic vibration. No effect appears, and a pure detection output without noise (or extremely small) can be obtained. This is one of the excellent characteristics of the present vibrating body for detecting weak Coriolis force with high accuracy, and even if the residual noise is separated in a circuit, it is much more advantageous than the conventional example.
[0025]
Next, details of the vibrator according to the first embodiment will be described. Mainly related to electrode connection pattern. Reference numeral 10 denotes a film-like connection pattern provided on the surface of the vibrating body, and connects the electrode films to each other and the electrode film and the connection pads 29 and 92 group. Through holes 28 and 93 are used for connection between the back surface and the front surface of the vibrator. The connection pads 92 on the base 9 are further interconnected (may be connected on the side of an external circuit (not shown)) if necessary, so that the drive terminals 8V and the detection terminals 8D are appropriately used. Further, when the terminals from the detection electrodes 7R and 7L are pulled out via the surface of the vibration legs, the areas of the excitation electrodes 6R and 6L are cut. This lowers the excitation efficiency and may induce an excitation signal as noise in the lead-out line of the close detection electrode. Therefore, in the present embodiment, the connection pad 29 provided on the bending portion of the vibration leg and the connection pad 92 provided on the auxiliary base 91 side are connected by wire bonding. Reference numeral 30 denotes a bonding wire. Since the amplitude of the basic vibration at a portion where the connection pad 29 is present is relatively small, even this structure is unlikely to be an obstacle. However, this is not an essential structure.
[0026]
2A and 2B show a second embodiment of a vibrating body for a gyro sensor according to the present invention, wherein FIG. 2A is a plan view, FIGS. 2B and 2C are cross-sectional views of a vibrating leg, and FIG. It is a diagram which shows a deformation | transformation. The shape and action of the present embodiment have much in common with the vibrator of the first embodiment described above. In other words, it is folded and bent to surround the center of gravity of the vibration mass, a symmetrical shape, the natural frequency of each leg is equal, the crystal Z plate (or Z 'plate), the inertial force of the basic vibration is balanced Separation of excitation electrode and detection electrode, large moment of Coriolis force at detection electrode part, detection of in-plane rotation, insensitivity of basic vibration in detection electrode, vacuum sealing, connection method (some illustrations omitted) Etc.
[0027]
The feature of this embodiment is that the direction of the axis of each part of the vibrating legs 1R, 1L is a multiple of approximately 60 °. Quartz has three-fold rotational symmetry around the Z axis, and there are X and Y axes of exactly the same nature every 120 °. Therefore, each part of the vibrating leg is made substantially parallel to any of the three Y1, Y2, and Y3 axes. Accordingly, the bending deflection can be detected piezoelectrically in any part of the vibrating leg, and the entire length can be used without waste as a spring part having a cut orientation in which the temperature change of the bending elasticity is relatively small. (As described above, in the first embodiment, the vibration legs 34R and 34L intentionally increase the rigidity to avoid the use as a spring part.) In this example, the spring parts 31R and 31L are used for excitation. 32R, 32L, 33R, 33L, 34R, and 34L are used for detection. (The spring portions 32R and 32L may be changed for excitation.) The electrodes of each portion are added in series with the detection voltage of each portion in consideration of the direction of the Coriolis moment to be detected and the direction of the Y axis of the portion. As shown in FIG. The detection sensitivity is further enhanced by the shape structure of this example.
[0028]
In the present embodiment, unlike the first embodiment, the lead pattern 10 from the detection electrode to the detection terminal passes through a gap generated by dividing the upper electrodes of the excitation electrodes 6R and 6L without going through wire bonding. . The position of the gap is the central part of the width of the spring parts 31R and 31L (the side surface of the neutral plane of bending), and this part is hardly distorted by the fundamental vibration, and both sides are sandwiched between excitation electrodes of the same polarity and equipotential And there is little risk of picking up noise from the excitation effect. Another way of drawing out the same effect is to provide a gap at the center of the bottom surface of the excitation electrodes 6R and 6L, and to place the two lead patterns 10 for the detection electrodes 7R and 7L one above the other. It is a structure to pass through.
[0029]
FIG. 3 shows another embodiment of the gyro sensor vibrating body of the present invention, each of which is formed from a quartz crystal Z plate and utilizes the Y-axis in three directions, (a), (b), (c), (D) is a plan view of each of these examples. (A) is similar to the vibrating body of FIG. 2, but the length of the vibrating body is shortened by eliminating the spring part in the longitudinal direction in the middle of the vibrating leg, and the detection electrodes can be provided on 22R, 22L 23R, and 23L. . (B) is a shape in which two vibrating legs bent in the same direction are arranged in the left-right direction, and the fixed ends 2R and 2L are brought close to each other to improve the transmission of vibration distortion between the vibrating legs. In (c), the vibration legs 1R and 1L are disposed surrounding the base 9, and a large leg is used to achieve a low frequency and a compact electrode shape while aiming for a large electrode area. (D) aimed at simplification and size reduction by further reducing the spring element than (a). Each of them has a bent leg shape that surrounds the vibration leg center of gravity GGR and GGL deeply ((b) the surrounding angle is slightly smaller but still exceeds 180 °), and the balance of the inertial force of the basic vibration For this reason, the radial radii GrR and GrL of the vibration leg centroids are arranged in parallel, and the heights of the centroids GGR and GGL in the radial direction are made equal.
[0030]
Since these gyro sensor vibrators of the present invention give a shape surrounding the center of gravity of the vibrating mass, the vibrating legs are so-called heads. Especially when subjected to impacts from the out-of-plane direction, the legs are closer to the fixed end than a simple tuning fork. Inevitably breaks. The device of the vibrator container for preventing this tendency and obtaining a gyroscope which is not easily damaged will be described. Although not shown below, the base 9 of the vibrator is fixed to a pedestal provided inside the container. In addition, a plate or the like coated with flexible silicon rubber is placed in the container with an appropriate interval in parallel to the surface of the vibration member, with the vibration member interposed therebetween. With this structure, the vibrating body normally does not touch the rubber surface, and the rubber plate receives the vibrating body in a range that does not deform excessively at the time of impact, thereby preventing breakage. The same applies to an accelerometer vibrating body to be described later.
[0031]
FIG. 4 shows an example of an embodiment of a vibrating gyroscope according to the present invention, where (a) is a plan view of a vibrating body, (b) is a block diagram of an excitation and detection circuit, and (c) is a modification of a part of the circuit. FIG. 4D is a waveform diagram for explaining the principle of angular velocity detection. In the vibrating body (a), generally “U” -shaped vibrating legs 1 </ b> R and 1 </ b> L are arranged symmetrically on a crystal Z (Z ′) plate surface and integrated with the base 9. The orientation in the plate is almost as shown, and the rotation of the plate surface is detected. The spring portions of the vibrating legs are 31R, 31L, 33R, 33L (parallel to the Y1 axis), 32R (parallel to the Y2 axis), and 32L (parallel to the Y3 axis), which are good directions of piezoelectric characteristics and temperature characteristics. The spring portions 31R and 31L are the most principal spring portions of the basic vibration, and the excitation electrodes 6R and 6L are provided. The rotation centers CR and CL are generated near the center. The center of gravity GGR, GGL of the entire vibrating leg including the additional masses 5R, 5L is directly above and at the same height as each rotation center, and the inertial force of the basic vibration is balanced.
[0032]
The spring parts 32R, 32L and 33R, 33L can be used to detect Coriolis force by providing detection electrodes as in the first and second embodiments, but this part applies a different detection principle in this example. Is not provided with a detection electrode. (This portion may be covered with an excitation electrode to increase the amplitude of the fundamental vibration.) The detection principle in this example is that the Coriolis forces FR and FL due to in-plane rotation act in the radial direction, and the bent shape of the legs Therefore, it is utilized that the moving masses GrR and GrL of the vibrating mass expand and contract depending on the direction of the Coriolis force (the “U” is slightly bent and vibrates while opening and closing). In general, if the radius of vibration mass increases in the same mass to spring system, the natural vibration period becomes longer, and if the radius decreases, the vibration period becomes shorter. Further, the oscillation circuits 11R and 11L (shown in (b)) allow the vibrating body to freely vibrate. Since the Coriolis force reverses the direction at every half cycle of vibration, each vibrating leg vibrates from end to end of the amplitude by alternately repeating a long half cycle and a short half cycle. Further, since the Coriolis forces FR and FL are in opposite directions, when the half cycle of vibration of one leg is extended, the half cycle of the other leg is shortened.
[0033]
In FIG. 4D, the vertical axis represents the oscillating voltage detected from the excitation electrode (upper side is 1R side, lower side is 1L side), and the horizontal axis is time. The time difference of the vibration half cycle is exaggerated. Since the output waveform of the oscillation circuit has a phase difference of several tens of degrees from the vibration displacement of the leg, if this is regarded as approximately 90 °, the half cycle of the voltage is the half cycle of the vibration mass velocity (the direction of the center of gravity is the same direction) Period), that is, substantially coincides with the half cycle from end to end of the vibration displacement of the center of gravity. Suppose that the zero point of the voltage waveform of each leg is TR1, TR2,..., TL1, TL2,. By measuring the time intervals of (1) TR1 to TR2, (2) TR2 to TR3, or (3) TL1 to TL2, respectively according to the above-described theory, (1) and (2), or (1) and (3 ) Etc., it becomes a function of Coriolis force. In this embodiment, the difference times such as TR1 and TL1, TL2 and TR2, TR3 and TL3,... Are directly counted using a fast clock pulse C.
[0034]
In the measurement circuit diagram of FIG. 4 (b), the excitation electrode of each leg is supplied to the oscillation circuits 11R and 11L interacting with each leg, and the output waveform is supplied by the waveform shaping circuits 12R and 12L if necessary. The amplitude, waveform, and phase are corrected so that stable detection is possible. Further, pulse signals at the time points of the waveform zero points TR1, TL1, TL2, TR2,... Are output by the level detection circuits 13R and 13L, and their intervals are measured by the time difference measurement circuit 14. That is, the signal C output from the stable high-frequency clock source 15 is counted. The correction circuit 16 corrects the nonlinearity of the measurement result. The measurement result is displayed on the display device 17.
[0035]
(C) is a circuit block diagram of a modification in which this embodiment is partially modified. In this case, detection electrodes are provided on the springs 32R, 32L, 33R, 33L and the like on the vibrating body side (not shown). The detection electrode output of each vibration leg includes a small amount of voltage due to Coriolis force, but most is a voltage proportional to the vibration displacement. This is directly amplified by the amplifiers 18R and 18L and applied to the level detection circuits 13R and 13L. The following is the same as the original form (b) of the present embodiment. However, the level detection circuits 13R and 13L are configured to detect a peak or bottom time point instead of a zero point of the voltage waveform.
[0036]
FIG. 5 shows a vibrating body for a linear acceleration sensor which is still another embodiment of the present invention, and (a) and (b) are plan views thereof. Each is formed of a crystal Z plate, and the spring portion has three or six vibrating legs parallel to the Y1, Y2, and Y3 axes. Although this sensor body is referred to as a vibrating body, it is not necessary to excite it when measuring only linear acceleration. However, the main part of the sensor is a cantilever member (mass-spring system) that has mass and bending elasticity like the leg of a tuning fork and has a shape that allows free vibration by stimulation without an excitation electrode. Is vibrated and may also be used as a gyroscope sensor or the like. When excitation is not performed, the vibrating body may be sealed in an airtight container instead of in a vacuum.
[0037]
The acceleration sensor vibrating body (a) is composed of three legs. When the base portion 9 performs linear acceleration motion parallel to the vibrating body surface and the inertial force acts on the vibrating legs 1A, 1B, and 1C to bend in the vibrating body surface, the distortion is shown in FIG. 1 (c) 7R or 7L. Such four-surface detection electrodes (not shown) are provided for detection. If the structure of each leg and the detection electrode is exactly the same, the deflection of each leg, that is, the positive / negative ratio of the detection voltage and the ratio are proportional to the sine of the angle between the leg axis and the direction of acceleration. The size and in-plane direction / direction can be calculated.
[0038]
For reference, this vibrator can be used in other ways. If the vibration legs are excited and designed so that the vibration locus of each center of gravity (illustrated by an arrow) is directed to one point at the center, the balance of inertial force can be substantially taken. A Coriolis force is generated in a direction perpendicular to the surface with respect to rotation about an axis parallel to the vibrating body surface. Therefore, if each leg is excited and a detection electrode having a structure as shown in FIG. 6 (b) 7L is provided, the magnitude / direction of the angular velocity vector can be calculated from the three detection voltages. It can also be a sensor.
[0039]
The acceleration sensor vibrating body in (b) has six legs, the legs 1A and 1D are parallel to the Y1 axis, the legs 1B and 1E are parallel to the Y3 axis, and the legs 1C and 1F are parallel to the Y2 axis. The detection terminal 8D group is provided on the base 9 disposed outside to facilitate connection with an external circuit. A biaxial acceleration sensor can be configured in accordance with the three-legged vibrating body of (a) using three pairs of legs in the same direction, but in this example legs 1A, 1B, 1C Can be used to detect the acceleration in the plane of the vibrating body, and to detect out-of-plane acceleration (perpendicular to the plane) using the legs 1D, 1E, and 1F. The legs 1A, 1B and 1C may be provided with detection electrodes having the structure shown in FIG. 1C, and the legs 1D, 1E and 1F may be provided with detection electrodes having the structure shown in FIG. 6B and 7L. Since the acceleration in the vertical direction can add the detection voltage for the three legs, the low detection sensitivity in this direction can be compensated.
[0040]
For reference again, the vibrating body (b) can also be used as a gyro sensor. There are two basic vibration modes that can be balanced. The first is a mode in which every other leg vibrates in the opposite direction to the outside of the vibrating body surface, which is excited by providing an electrode of the same structure as that for detecting out-of-plane bending. The axis of rotation that can be detected is parallel to the surface of the vibrating body, and the deflection of each leg due to the Coriolis force is also in-plane. The second is a mode in which the interval between adjacent legs changes in the plane of the vibrating body, and the interval between legs at a certain moment is every other large, small, large, small, large, and small as shown by arrows. Then, the Coriolis force by the rotation axis parallel to the vibrating body surface is detected as out-of-plane vibration of each leg. It is not impossible to detect in-plane rotation. For that purpose, an eccentric mass is provided on the same side of each leg as shown in (c) (even if the amount of eccentricity is large, the eccentric arm is parallel to each Y axis). In the same manner as in the second conventional example, in-plane bending due to Coriolis force is induced and detected.
[0041]
Although various embodiments of the present invention have been described above, application examples of the present invention are not limited to those already described. For example, the material of the vibrator is not limited to quartz, but may be other piezoelectric single crystals (the refraction angle of the spring portion is determined according to the cut angle and the symmetry of the crystal). In addition, there may be cases where a piezoelectric ceramic is used, or a metal having a piezoelectric element attached thereto. Also in these cases, the position of the electrode film on the vibrating body conforms to the case described above. The shape of the vibrating legs (for example, gently folding or spiraling with porcelain or metal vibrating bodies, or with the free ends of the legs facing outwards, or a pair of legs with different shapes), and any number of vibrating legs There are various types of additional mass positions and shapes (possibly with no weight member), base shapes, excitation and detection electrode positions, connection patterns and terminal arrangements, etc. obtain. The same applies to the vibrating body and the detection circuit configuration in the vibrating gyroscope.
[0042]
【The invention's effect】
The motion sensor vibrating body of the present invention can achieve the following effects by the configuration of claims 1 to 2.
(1) Small and thin (possibly because the main part is in one plane).
(2) Easy to manufacture (because of the planar shape and the minimum number of vibrating legs requiring adjustment).
(3) High vibration body quality (because the inertial force of basic vibration is balanced as a whole).
(4) In-plane rotation can be detected (depending on overall configuration, also related to thinning).
(5) Sensitivity of detection is possible (sites suitable for excitation and detection can be provided, each electrode can be provided, the effective length of the detection electrode can be increased, and four legs can be used, bending The shape can increase the mass for detecting the Coriolis force and the moment at the detection site, and can reduce the noise-like piezoelectric effect due to the excitation vibration at the detection site).
[0043]
Moreover, although the structure of claim 3 is added and the vibration leg is bent, the same piezoelectric and elastic properties can be given to each part of the leg, and the following various effects are obtained.
(6) Each part of the leg can be effectively used piezoelectrically for detection (and excitation).
(7) The elastic properties of the legs (for example, temperature characteristics of elastic modulus) can be kept relatively good.
(8) Accordingly, the piezoelectric single crystal is effectively used as the material of the sensor vibrating body, thereby enabling highly accurate detection.
(9) It is possible to use a quartz material that is particularly weak in piezoelectric effect but excellent in elastic properties.
[0044]
The configuration of claim 4 has the following effects.
(10) The piezoelectric effect due to the fundamental vibration of the vibrating mass can be made difficult to appear on the Coriolis force detection electrode.
(11) Therefore, weak Coriolis force can be detected with low noise.
[0045]
The configuration of claim 5 has the following effects.
(12) It was possible to provide a vibration gyroscope based on a novel detection principle that can easily digitize the detection output.
(13) In some cases, the configuration of the vibrator can be simplified by eliminating the need for the detection electrode.
[Brief description of the drawings]
FIG. 1 shows a first embodiment of a motion sensor vibrating body for a vibration gyroscope according to the present invention, where (a) is a plan view, and (b) and (c) are vibrations that also show electrode arrangement and connection. Sectional drawing of a leg, (d) is a diagram showing a bending deformation of a vibrating leg due to fundamental vibration and Coriolis force.
FIGS. 2A and 2B show a second embodiment of a motion sensor vibrating body for a vibration gyroscope of the present invention, FIG. 2A is a plan view, FIG. 2B is a diagram showing bending deformation of a vibration leg, and FIG. And (d) are cross-sectional views of the vibrating legs.
FIGS. 3A and 3B show other embodiments of the vibration sensor vibrating body for the vibration gyroscope of the present invention, and FIGS. 3A and 3B are plan views of the respective examples. FIGS. .
4A and 4B show an embodiment of a vibrating gyroscope of the present invention, in which FIG. 4A is a plan view of a vibrating body, FIG. 4B is a block diagram of an excitation and detection circuit, and FIG. (D) is a waveform diagram for explaining the principle of angular velocity detection.
FIGS. 5A and 5B show an embodiment of a motion sensor vibrating body for an accelerometer capable of detecting multi-directional linear acceleration according to the present invention, and FIGS. 5A and 5B are plan views of examples thereof. FIGS.
6A and 6B show a motion sensor vibrating body for a vibration gyroscope of a first conventional example, where FIG. 6A is a plan view and FIG. 6B is a cross-sectional view of a vibration leg.
7A and 7B show a motion sensor vibrating body for a vibration gyroscope of a second conventional example, where FIG. 7A is a plan view and FIG. 7B is a sectional view of a vibration leg.
[Explanation of symbols]
1A, 1B, 1C, 1D, 1E, 1F, 1R, 1L Vibration leg (or leg)
2R, 2L fixed end
3R, 3L, 31R, 31L, 32R, 32L, 33R, 33L Spring part
34R, 34L, 35R, 35L (vibrating leg)
4R, 4L Free end
5R, 5L additional mass
6R, 6L excitation electrode
7R, 7L detection electrode
8D detection terminal
8V excitation terminal
9 Base
91 Auxiliary base
10 Lead pattern
29, 92 Connection pad
28, 93 Through hole
30 Bonding wire
11R, 11L oscillator
12R, 12L waveform filter
13R, 13L Zero level detection circuit
14 Time difference measurement circuit
15 High frequency clock source
16 Correction circuit
17 Display device
C clock pulse
CR, CL Rotation center
GR, GL Center of gravity of additional mass
GGR, GGL Center of gravity of vibrating mass
FR, FL Coriolis force
rR, rL Radius of additional mass
GrR, GrL Radius of vibrating mass
UR, UL velocity vector
SA symmetry axis
Ω Angular velocity

Claims (5)

Substantially has a plurality of cantilever vibration legs in one plane, at least one center of gravity of the seismic mass and can those the vibrating legs traced to a free end from the fixed end of the vibrating legs of the vibrating leg It has a bent shape that is surrounded by each part at an angle of 270 ° or more, and when the plurality of vibrating legs freely vibrate in the plane, the vibration locus of the center of gravity of their vibrating mass is substantially collinear. The motion sensor vibration for a vibration gyroscope is set so that the inertial force of the vibration excited as described above is substantially canceled as a whole, and at least an excitation electrode is provided on the bent surface. body. The excitation electrode is provided on four side surfaces of the portion near the fixed end of the vibration leg, and the Coriolis force detection electrode is closer to the free end than the excitation electrode and surrounds the center of gravity of the vibration mass. The motion sensor vibrating body according to claim 1 , wherein the vibration sensor vibrating body is provided in at least a part of the portion. The material of each vibrator is made of a single crystal material and is bent in a polygonal line, and at least two directions of the bent part of the polygonal line are at least of a plurality of the same kind of crystal axes of the single crystal material. The motion sensor vibrating body according to claim 1 , wherein the motion sensor vibrating body has an angle substantially equal to two. The motion sensor vibrating body according to claim 2 or 3, wherein an action line of inertial force of a vibrating mass near the free end passes through a portion provided with the Coriolis force detection electrode . The motion sensor vibrating body according to claim 1 is used, and the vibration mass of the vibration part has a structure in which the radial diameter of the vibration motion is changed by Coriolis force, and the direction is reversed every time the vibration direction is changed. Detecting the rotational angular velocity that caused the Coriolis force by making the half-cycle of vibrational motion change alternately by the effect of force and measuring the half-cycle change of the subsequent vibration or the time corresponding to the change. Vibrating gyroscope characterized by.

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