Patent Publication Number: US-9835641-B2

Title: Angular velocity detection device and angular velocity sensor including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/705,459 filed on Dec. 5, 2012, which is a by-pass continuation of PCT/JP2011/003558 filed on Jun. 22, 2011, which claims priority to Japanese Patent Application Nos. 2010-144642 and 2010-144643 filed on Jun. 25, 2010; 2010-248078 and 2010-248079 filed on Nov. 5, 2010; and 2011-025738 filed on Feb. 9, 2011. 
    
    
     BACKGROUND 
     1. Technical Field 
     The technical field relates to an angular velocity sensor for use in, for example, a mobile device or a vehicle, and to an angular velocity detection device included in the sensor. 
     2. Background Art 
       FIG. 17  is a perspective view of an angular velocity detection device used in a conventional angular velocity sensor. Angular velocity detection device  1  includes frame body  2 , transverse beam  3 , arms  4 ,  5 ,  6 , and  7 , weights  8 ,  9 ,  10 , and  11 , driver  12 , monitor  13 , and detectors  14 ,  15 . Transverse beam  3  is suspended by frame body  2  in the direction of the X axis where the X, Y, and Z axes are orthogonal to each other. One end of each of arms  4  and  5  is supported by transverse beam  3  and arms  4  and  5  extend in the positive direction of the Y axis. Weights  8  and  9  are disposed at another end of each of arms  4  and  5 , respectively. One end of each of arms  6  and  7  is supported by transverse beam  3  and arms  6  and  7  extend in the negative direction of the Y axis. Weights  10  and  11  are disposed at another end of each of arms  6  and  7 , respectively. Driver  12  applies an AC voltage to arm  4  so as to generate a piezoelectric effect, thereby vibrating arm  4  in the direction of the X axis. This vibration causes arms  5 ,  6 , and  7  to resonate in the direction of the X axis. Monitor  13  detects the displacements of arms  4 ,  5 ,  6 , and  7  in the direction of the X axis. Detectors  14  and  15  output sensing signals, which are generated on arms  6  and  7  due to the piezoelectric effect and are caused by the Coriolis force when an angular velocity is applied to angular velocity detection device  1 . From these sensing signals, displacements in the direction of the Y or Z axis are detected. 
     SUMMARY 
     The angular velocity detection device includes an outer frame including a fixed portion and an outer beam portion connected to the fixed portion; a sensing part surrounded by the outer frame with a first slit therebetween; and a joint connecting the outer frame to the sensing part. The sensing part includes an inner beam portion, a flexible portion, and a detector. The inner beam portion has a hollow region inside and is square-shaped when viewed from above. The flexible portion is disposed in the hollow region of the inner beam portion, and connected to the inner edge of the inner beam portion. The detector is disposed in the flexible portion. The first slit is formed to surround the sensing part excluding the joint. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1A  is a top view of an angular velocity detection device according to an embodiment. 
         FIG. 1B  is a sectional view of the angular velocity detection device shown in  FIG. 1A . 
         FIG. 2  is a sectional view of an essential part of the angular velocity detection device shown in  FIG. 1A . 
         FIG. 3  shows the relationship between the phases of drive signals and the phases of vibrations of the arms of the angular velocity detection device shown in  FIG. 1A . 
         FIG. 4  shows the relation of connection between the angular velocity detection device shown in  FIG. 1A  and a driving circuit. 
         FIG. 5  is a top view showing a behavior of the angular velocity detection device shown in  FIG. 1A  when an angular velocity around the Z axis is applied thereto. 
         FIG. 6  is a top view showing a behavior of the angular velocity detection device shown in  FIG. 1A  when an angular velocity around the Y axis is applied thereto. 
         FIG. 7  shows phases of signals to be output from detectors of the angular velocity detection device shown in  FIG. 1A . 
         FIG. 8  shows the relation of connection between the angular velocity detection device shown in  FIG. 1A  and a detecting circuit. 
         FIG. 9  is a top view of an angular velocity detection device according to another embodiment. 
         FIG. 10  is a top view of an angular velocity detection device according to another embodiment. 
         FIG. 11  shows phases of signals to be output from detectors of the angular velocity detection device shown in  FIG. 10 . 
         FIG. 12  is a top view of an angular velocity detection device of another embodiment. 
         FIG. 13  shows phases of signals to be output from detectors of the angular velocity detection device shown in  FIG. 12 . 
         FIG. 14  is a partial top view of an angular velocity detection device of another embodiment. 
         FIG. 15  is a top view of an angular velocity detection device of another embodiment. 
         FIG. 16A  is a top view of an angular velocity detection device of another embodiment. 
         FIG. 16B  is a top view of an angular velocity detection device of another embodiment. 
         FIG. 17  is a perspective view of a conventional angular velocity detection device. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Before the detailed discussion of exemplary embodiments, problems of the conventional angular velocity detection device will be described. In angular velocity detection device  1  shown in  FIG. 17 , detectors  14  and  15  are not disposed symmetrically with respect to both axes “A” and “B”, which are parallel to the Y and X axes, respectively. This makes it impossible to cancel unwanted signals due to external disturbance such as acceleration or impact, causing the detection accuracy of the angular velocity to be low. Moreover, an external stress applied to angular velocity detection device  1  acts on transverse beam  3  so as to cause unwanted vibration on arms  4 ,  5 ,  6 , and  7 , thereby fluctuating outputs of detectors  14  and  15 . 
     Referring now to the drawings, description will be provided of exemplary embodiments of an angular velocity detection device and an angular velocity sensor including the device. In these embodiments, the same components as in the preceding embodiments are denoted by the same reference numerals, and the detailed description thereof may be omitted. 
     Exemplary Embodiments 
       FIG. 1A  is a top view of angular velocity detection device  16  (hereinafter referred as device  16 ) according to an embodiment.  FIG. 1B  is a sectional view of device  16 , taken along line  1 B- 1 B of  FIG. 1A . Device  16  includes an outer frame including fixed portions  17 A and  17 B, and outer beam portions  18 A and  18 B connected to fixed portions  17 A and  17 B. Device  16  further includes a sensing part surrounded by the outer frame with first slits  80 A and  80 B therebetween, and joints  19 A and  19 B connecting the outer frame and the sensing part. First slits  80 A and  80 B are formed to surround the sensing part excluding joints  19 A and  19 B. 
     The sensing part includes inner beam portion  20 A, central beam portion  20 B, first arm  21 , second arm  22 , third arm  23 , fourth arm  24  (hereinafter, arms  21  to  24 ), drivers  29  to  36 , and detectors  41  to  48 . The sensing part further includes weights  25  to  28  disposed at an end of each of first to fourth arms  21 ,  22 ,  23 , and  24 , respectively. 
     Inner beam portion  20 A is square-shaped when viewed from above. Central beam portion  20 B connects the opposite sides of inner beam portion  20 A, and is parallel to outer beam portion  18 A. Arms  21  to  24  are disposed inside inner beam portion  20 A and connected to central beam portion  20 B. 
     Thus, fixed portions  17 A,  17 B, outer beam portions  18 A,  18 B, and inner beam portion  20 A together form a frame part having a top surface (first surface) and a bottom surface (second surface), and also having inner edge  104  and hollow region  102  inside the frame part. As shown in  FIG. 1B , lower support body  110 B is disposed so as to confront the bottom surface of the frame part. Lower support body  110 B is bonded to fixed portions  17 A and  17 B via adhesive portions  108 . Central beam portion  20 B, arms  21  to  24 , and weights  25  to  28  are disposed in hollow region  102  of the frame part, thereby forming a flexible portion connected to inner edge  104  of the frame part. First slits  80 A and  80 B surrounding inner beam portion  20 A are through-holes disposed between adhesive portions  108  of the frame part and the flexible portion. 
     Adhesive portions  108  are formed at the four corners of the outer frame in  FIG. 1A , but may alternatively extend long between outer beam portions  18 A,  18 B along fixed portions  17 A,  17 B, or extend along outer beam portions  18 A,  18 B. 
     As shown in  FIG. 1B , the frame part and lower support body  110 B are separated by the thickness of adhesive portions  108 . This configuration can reduce the stress when the frame part and lower support body  110 B are bonded to each other, thereby reducing the residual stress accumulated in the flexible portion. As a result, the sensitivity of device  16  is prevented from degrading over time. 
     Arm  22  is disposed on the same side as arm  21  with respect to central beam portion  20 B, and is line-symmetrical to arm  21 . More specifically, arm  22  is symmetrical to arm  21  with respect to axis “C”, which is at right angles to central beam portion  20 B. Axis “C” is parallel to the Y axis. 
     Arm  23  is disposed on the opposite side of arm  21  with respect to central beam portion  20 B, and is line-symmetrical to arm  21 . More specifically, arm  23  is symmetrical to arm  21  with respect to axis “D”, which passes through the center of central beam portion  20 B. Axis “D” is parallel to the X axis. 
     Arm  24  is disposed on the same side as arm  23  with respect to central beam portion  20 B, and is line-symmetrical to arm  23 . More specifically, arm  24  is symmetrical to arm  23  with respect to axis “C”. Thus, arms  21  and  22  extend in the positive direction of the Y axis, whereas arms  23  and  24  extend in the negative direction of the Y axis. 
     Drivers  29 ,  30  and detectors  41 ,  42  are disposed on arm  21 . Drivers  31 ,  32  and detectors  43 ,  44  are disposed on arm  22 . Drivers  33 ,  34  and detectors  45 ,  46  are disposed on arm  23 . Drivers  35 ,  36  and detectors  47 ,  48  are disposed on arm  24 . Drivers  29  to  36  drive arms  21  to  24  in the X axis direction. Detectors  41  to  48  detect the displacements of weights  25  to  28  disposed on arms  21  to  24 , respectively, in the Y or Z axis direction. 
     Device  16  further includes monitors  37  to  40  in the vicinity of the regions where arms  21  to  24  are connected to central beam portion  20 B. Monitors  37  to  40  detect the displacements of arms  21  to  24  in the X axis direction. 
     Each component of angular velocity detection device  16  is now described as follows. Fixed portions  17 A and  17 B support outer beam portions  18 A and  18 B. Specifically, fixed portions  17 A and  17 B are formed parallel to the Y axis, and both ends of them are connected to outer beam portions  18 A and  18 B, thereby forming an outside frame body. Fixed portions  17 A and  17 B are fixed, using a support member or an adhesive, in a package (not shown) where device  16  is stored. Fixed portions  17 A and  17 B includes electrode pads (not shown) at their outer edges. These electrode pads are electrically connected to drivers  29  to  36 , monitors  37  to  40 , and detectors  41  to  48  by wires (not shown). 
     Inner beam portion  20 A has two sides parallel to the Y axis and two sides parallel to the X axis, thereby forming an inside frame body. Those two sides of inner beam portion  20 A that are parallel to the Y axis can bend in the Z axis direction, and are substantially symmetrical to each other with respect to axis “C” parallel to the Y axis. As a result, the two sides of inner beam portion  20 A that are parallel to the Y axis bend with a substantially equal amplitude in response to an angular velocity applied to device  16 . The two sides of inner beam portion  20 A that are parallel to the X axis are connected at their substantial centers to outer beam portions  18 A and  18 B via joints  19 A and  19 B. 
     Central beam portion  20 B is parallel to the X axis, and is connected to substantial midpoints of the two sides of inner beam portion  20 A that are parallel to the Y axis. As a result, central beam portion  20 B can bend in the Z axis direction. 
     Arm  21  extends in the positive direction of the Y axis from one end thereof connected to central beam portion  20 B; extends in the positive direction of the X axis from the first joint; and extends in the negative direction of the Y axis from the second joint, thus forming the shape of the letter “J”. At the other end of arm  21 , weight  25  is disposed. 
     Arm  22  extends in the positive direction of the Y axis from one end thereof connected to central beam portion  20 B; extends in the negative direction of the X axis from the first joint; and extends in the negative direction of the Y axis from the second joint, thus forming the shape of the letter “J”. At the other end of arm  22 , weight  26  is disposed. 
     Arm  23  extends in the negative direction of the Y axis from one end thereof connected to central beam portion  20 B; extends in the positive direction of the X axis from the first joint; and extends in the positive direction of the Y axis from the second joint, thus forming the shape of the letter “J”. At the other end of arm  23 , weight  27  is disposed. 
     Arm  24  extends in the negative direction of the Y axis from one end thereof connected to central beam portion  20 B; extends in the negative direction of the X axis from the first joint; and extends in the positive direction of the Y axis from the second joint, thus forming the shape of the letter “J”. At the other end of arm  24 , weight  28  is disposed. Arms  21  to  24  are connected to weights  25  to  28 , respectively, at the recessed center of one side of each of weights  25  to  28  having a substantially square shape. Arms  21  to  24  can bend in the X, Y, and Z axes directions. 
     Arms  21  and  22  are symmetrical with respect to axis “C” parallel to the Y axis. Arms  23  and  24  are also symmetrical with respect to axis “C”. Arms  21  and  23  are symmetrical with respect to axis “D” parallel to the X axis. Arms  22  and  24  are also symmetrical with respect to axis “D”. Disposed to be symmetrical with respect to axes “C” and “D”, arms  21  to  24  bend with a substantially equal amplitude in response to an angular velocity applied to device  16 . 
     Fixed portions  17 A,  17 B, outer beam portions  18 A,  18 B, inner beam portion  20 A, central beam portion  20 B, and arms  21  to  24  are made of a piezoelectric material such as crystal, LiTaO 3 , and LiNBO 3 . These portions can alternatively be made of a non-piezoelectric material such as silicon, diamond, fused silica, alumina, and GaAs. Using silicon enables these portions to be miniaturized by micro processing technology and be integrated into an IC or other circuit. 
     Fixed portions  17 A,  17 B, outer beam portions  18 A,  18 B, inner beam portion  20 A, central beam portion  20 B, and arms  21  to  24  may be made of the same or different materials from each other and then assembled, or may be integrally formed from the same material. In the case of forming integrally from the same material, dry or wet etching can be used to form fixed portions  17 A,  17 B, outer beam portions  18 A,  18 B, inner beam portion  20 A, central beam portion  20 B, and arms  21  to  24  efficiently in the same process. 
     Drivers  29  to  36  drive arms  21  to  24  in the X axis direction. Drivers  29  to  36  are of piezoelectric type using piezoelectric elements in the embodiment, but may alternatively be of capacitance type using the capacitance between electrodes. 
       FIG. 2  is a schematic sectional view of drivers  29  and  30 , taken along line  2  of  FIG. 1A . Driver  29  includes lower electrode  29 A, upper electrode  29 C, and piezoelectric element  29 B sandwiched between these electrodes. Driver  30  includes lower electrode  30 A, upper electrode  30 C, and piezoelectric element  30 B sandwiched between these electrodes. Drivers  29  and  30  are disposed parallel to each other on the top surface of arm  21 . 
     Lower electrodes  29 A,  30 A and upper electrodes  29 C,  30 C are made of platinum (Pt), gold (Au), aluminum (Al), or an alloy or oxide containing one of them as a main component. Lower electrodes  29 A and  30 A are preferably made of Pt. In the case of using Pt, lead zirconate titanate (PZT), which is contained in piezoelectric elements  29 B and  30 B, can be oriented in one direction. Upper electrodes  29 C and  30 C are preferably made of Au. In the case of using Au, the resistance hardly degrades over time, allowing device  16  to be highly reliable. 
     Lower electrodes  29 A and  30 A are reference potential electrodes. Applying an AC driving voltage to upper electrodes  29 C and  30 C can vibrate arm  21  in the X axis direction. An AC driving voltage can be applied to both lower electrodes  29 A,  30 A and upper electrodes  29 C,  30 C to make the drive efficiency higher. 
     Drivers  31  to  36 , which have the same structure as drivers  29  and  30 , are disposed on the top surfaces of arms  22  to  24 , respectively. As shown in  FIG. 1A , drivers  29  to  36  are preferably disposed near weights  25  to  28  in arms  21  to  24  having a substantially J shape. With this arrangement, those regions of arms  21  to  24  near central beam portion  20 B can be used for detectors  41  to  48 . On the other hand, in the case where drivers  29  to  36  are disposed in those regions of arms  21  to  24  near central beam portion  20 B, drivers  29  to  36  can have a high drive efficiency and a large area. This results in an increase in the amplitude of arms  21  to  24 , allowing device  16  to have a high sensitivity. 
       FIG. 3  shows the relationship between the phases of the drive signals given to drivers  29  to  36  and the phases of vibrations of arms  21  to  24 . Drivers  29 ,  31 ,  33 , and  35  are given drive signals of the same phase (+), whereas drivers  30 ,  32 ,  34 , and  36  are given drive signals of the opposite phase (−) to it. As a result, arms  21 ,  23  vibrate at the same phase (+), whereas arms  22 ,  24  vibrate at the opposite phase (−) to it in the X axis direction. 
     Monitors  37  to  40  detect the displacements of arms  21  to  24  in the X axis direction. Monitors  37  to  40  are of piezoelectric type using piezoelectric elements in the embodiment like drivers  29  and  30  shown in  FIG. 2 , but may alternatively be of capacitance type using the capacitance between electrodes. 
     Monitors  37  to  40  are disposed on the top surfaces of arms  21  to  24 . More specifically, monitors  37  to  40  are disposed in those regions of the top surfaces of arms  21  to  24  where they can receive monitor signals of the same phase as the vibrations of arms  21  to  24  shown in  FIG. 3 . Monitors  37  to  40  can efficiently detect distortion in spite of their small area by being disposed in the regions of arms  21  to  24  having a substantially J shape near central beam portion  20 B as shown in  FIG. 1A . Monitors  37  to  40  are preferably smaller in area than detectors  41  to  48  in order to secure the area for detectors  41  to  48 . 
     Detectors  41  to  48  detect the displacements of arms  21  to  24  in the Y or Z axis direction. Detectors  41  to  48  are of piezoelectric type using piezoelectric elements like drivers  29  and  30  shown in  FIG. 2 , but may alternatively be of capacitance type using the capacitance between electrodes. 
     Detectors  41  to  48  are disposed on the top surfaces of arms  21  to  24 . As shown in  FIG. 1A , detectors  41  to  48  can be disposed in those regions of arms  21  to  24  having a substantially J shape near central beam portion  20 B. With this arrangement, detectors  41  to  48  can have a high detection efficiency, and a large area, allowing device  16  to have a high sensitivity. On the other hand, in the case where detectors  41  to  48  are disposed in those regions of arms  21  to  24  near weights  25  to  28 , those regions of arms  21  to  24  near central beam portion  20 B can be used for drivers  29  to  36 . 
     Detectors  41 ,  42  and detectors  43 ,  44  are symmetrical with respect to axis “C” parallel to the Y axis, whereas detectors  45 ,  46  and detectors  47 ,  48  are symmetrical with respect to axis “C”. Detectors  41 ,  42  and detectors  45 ,  46  are symmetrical with respect to axis “D” parallel to the X axis, whereas detectors  43 ,  44  and detectors  47 ,  48  are symmetrical with respect to axis “D”. The arrangement of detectors  41  to  48  symmetrically with respect to axes “C” and “D” can cancel unwanted signals due to external disturbance such as acceleration and impact, allowing accurate detection of an angular velocity. 
     First slits  80 A and  80 B are formed in such a manner as to surround the sensing part excluding joints  19 A and  19 B. In short, the sensing part is suspended by joints  19 A and  19 B. For this reason, when fixed portions  17 A,  17 B and/or outer beam portions  18 A,  18 B are subjected to a stress, causing device  16  to be pulled in the X axis direction, or causing fixed portions  17 A,  17 B and/or outer beam portions  18 A,  18 B to be bent, the stress is not easily transferred to the sensing part. This reduces the effect of the external stress on the sensing part, thereby reducing fluctuations in the output of detectors  41  to  48  when an external stress is applied to device  16 . Specifically, in the case where device  16  has a size of about 2.5×2.5 mm and its base is made of 150 μm thick silicon (Si), the influence of the stress on the sensing part is reduced to about one third. This effect is provided independently of the effect of the arrangement of detectors  41  to  48 . 
     The following is a description of a driving circuit and a detecting circuit which are connected to device  16 . Specifically, the following description is focused on the improvement in the detection accuracy of an angular velocity achieved by the arrangement of detectors  41  to  48  symmetrically with respect to axes “C” and “D”. 
       FIG. 4  shows the relation of connection between angular velocity detection device  16  and driving circuit  50 , which includes I-V conversion amplifier  51 , AGC (Auto Gain Control)  52 , filter  53 , and drive amplifiers  54 ,  55 . Electrode pads  49 A to  49 H, which are part of electrode pads formed in fixed portions  17 A and  17 B, are electrically connected to drivers  29  to  36 , respectively, and electrode pads  49 J to  49 M are electrically connected to monitors  37  to  40 , respectively. 
     Electrode pads  49 J to  49 M output monitor signals. The monitor signals are connected together, converted into a voltage by I-V conversion amplifier  51 , adjusted to have a constant amplitude by AGC  52 , separated from unwanted frequency components by filter  53 , inverted and amplified by drive amplifier  54 , and supplied to electrode pads  49 B,  49 D,  49 F, and  49 H. Drive amplifier  54  outputs a drive signal. The drive signal is inverted and amplified by drive amplifier  55 , and supplied to electrode pads  49 A,  49 C,  49 E, and  49 G. With this configuration, driving circuit  50  can provide the drive signals having the phases shown in  FIG. 3  to drivers  29  to  36 , thereby vibrating arms  21  to  24  in the phases shown in  FIG. 3 . 
       FIGS. 5 and 6  are top views showing behaviors of angular velocity detection device  16  when an angular velocity is applied thereto.  FIG. 5  shows the case of detecting an angular velocity around the Z axis. When driving circuit  50  provides drive signals to drivers  29  to  36  in device  16 , drive oscillation  56  is generated at a unique drive oscillation frequency in the X axis direction. When angular velocity  57  around the Z axis is applied to device  16 , Coriolis force is generated on weights  25  to  28  in the Y axis direction, thereby generating detection oscillation  58 . Detection oscillation  58  generated in weights  25  to  28  in the Y axis direction allows arms  21  to  24  to vibrate in the X axis direction. Arms  21  and  23  perform drive oscillation in anti-phase with arms  22  and  24 , therefore detection oscillation of arms  21  and  23  is in anti-phase with that of arms  22  and  24 . 
     Detection oscillation  58  allows detectors  41  to  48  to output detection signals that have the same frequency as drive oscillation  56  and that also have an amplitude dependent on angular velocity  57 . Thus, measuring the magnitude of the detection signals results in detecting the magnitude ω z  of angular velocity  57 . 
       FIG. 6  shows the case of detecting an angular velocity around the Y axis. In response to angular velocity  59  around the Y axis, Coriolis force generates detection oscillation  60  on weights  25  to  28  in the Z axis direction. Arms  21  and  23  perform drive oscillation in anti-phase with arms  22  and  24 , therefore detection oscillation of arms  21  and  23  is in anti-phase with that of arms  22  and  24 . 
     Detection oscillation  60  allows detectors  41  to  48  to output detection signals that have the same frequency as drive oscillation  56  and that also have an amplitude dependent on angular velocity  59 . Thus, measuring the magnitude of the detection signals results in detecting the magnitude ω y  of angular velocity  59 . 
       FIG. 7  shows phases of signals to be output from detectors  41  to  48  of angular velocity detection device  16 . The signals to be output from detectors  41  to  48  are referred to as S 1  to S 8 , respectively.  FIG. 7  specifically shows the following: the phases of the drive signals of the detectors; the phases in the case where angular velocities are applied around the X, Y, and Z axes; and the phases in the case where accelerations are applied in the X, Y, and Z axes directions, with respect to the phases of the drive signals provided by driving circuit  50 . 
     From  FIG. 7 , the magnitude ω z  of angular velocity  57  around the Z axis can be calculated by Mathematical Formula (1)
 
ω z ={( S 2+ S 5)+( S 3+ S 8)}−{( S 1+ S 6)+( S 4+ S 7)}  (1)
 
     The magnitude ω y  of angular velocity  59  around the Y axis can be calculated by Mathematical Formula (2)
 
ω y ={( S 2+ S 5)+( S 1+ S 6)}−{( S 3+ S 8)+( S 4+ S 7)}  (2)
 
     The calculation of Mathematical Formulas (1) and (2) can be performed by detecting circuit  61  shown in  FIG. 8 .  FIG. 8  shows the relation of connection between angular velocity detection device  16  and the detecting circuit. Detecting circuit  61  processes signals S 1  to S 8  output from detectors  41  to  48  of device  16 . 
     When the phases of the drive signals are substituted into Mathematical Formula (1), the result becomes 0. Specifically, detectors  41  to  48  receive drive signals as unwanted signals, which in turn are cancelled with each other by the calculation of Mathematical Formula (1). Similarly, when the phases in the cases that each one of the angular velocities around the X and Y axes, and the accelerations in the X, Y, and Z axes directions is applied are substituted into Mathematical Formula (1), the results become 0. Thus, angular velocities around the other axes and accelerations in the directions of the other axes, which are unwanted signals, are cancelled with each other by the calculation of Mathematical Formula (1). 
     When the phases in the cases that each one of the drive signals, angular velocities around the X and Z axes, and accelerations in the X, Y, and Z axes directions is applied are substituted into Mathematical Formula (2), the results become 0. Thus, drive signals, angular velocity components around the other axes and acceleration components in the directions of the other axes, which are unwanted signals, are cancelled with each other by the calculation of Mathematical Formula (2). 
     As described above, detectors  41  to  48  are disposed symmetrically with respect to axis “C” parallel to the Y axis, and also with respect to axis “D” parallel to the X axis. This arrangement can cancel the drive signals, angular velocities around the other axes, and accelerations in the directions of the other axes, which are unwanted signals. 
       FIG. 8  shows the relation of connection between angular velocity detection device  16  and detecting circuit  61 . Fixed portions  17 A and  17 B include electrode pads  491  to  498  electrically connected to detectors  41  to  48 . 
     The output lines of electrode pads  492  and  495  are connected together and connected to I-V conversion amplifier  62 A. In short, signals S 2  and S 5  are superimposed and sent to I-V conversion amplifier  62 A. The output lines of electrode pads  493  and  498  are connected together and connected to I-V conversion amplifier  62 B. In short, signals S 3  and S 8  are superimposed and sent to I-V conversion amplifier  62 B. The output lines of electrode pads  491  and  496  are connected together and connected to I-V conversion amplifier  62 C. In short, signals S 1  and S 6  are superimposed and sent to I-V conversion amplifier  62 C. The output lines of electrode pads  494  and  497  are connected together and connected to I-V conversion amplifier  62 D. In short, signals S 4  and S 7  are superimposed and sent to I-V conversion amplifier  62 D. 
     The angular velocity around the Z axis is calculated as follows. The output lines of I-V conversion amplifiers  62 A and  62 B are connected together, whereas the output lines of I-V conversion amplifiers  62 C and  62 D are connected together. These signals connected together are each sent to difference amplifier  63 Z. Difference amplifier  63 Z outputs a signal, which is in turn detected by detector circuit  64 Z using the signal from driving circuit  50 , and then extracted by low-pass filter  65 Z. Thus, the magnitude ω z  of angular velocity  57  around the Z axis is output from output terminal  66 Z. 
     The angular velocity around the Y axis is calculated as follows. The output lines of I-V conversion amplifiers  62 A and  62 C are connected together, whereas the output lines of I-V conversion amplifiers  62 B and  62 D are connected together. These signals connected together are each sent to difference amplifier  63 Y. Difference amplifier  63 Y outputs a signal, which is in turn detected by detector circuit  64 Y using the signal from driving circuit  50 , and then extracted by low-pass filter  65 Y. Thus, the magnitude ω y  of angular velocity  59  around the Y axis is output from output terminal  66 Y. 
     As known from  FIGS. 7 and 8 , the drive signals are cancelled by connecting of electrode pads  491  through  498  before being sent to I-V conversion amplifiers  62 A to  62 D. Thus, the drive signals can be cancelled before being amplified by I-V conversion amplifiers  62 A to  62 D. 
     The angular velocity around the Y axis is cancelled by connecting of I-V conversion amplifiers  62 A through  62 D before being sent to difference amplifier  63 Z for detecting the angular velocity around the Z axis. Thus, the angular velocity around the Y axis can be cancelled before being amplified by difference amplifier  63 Z. 
     The angular velocity components around the Z axis are cancelled by connecting of I-V conversion amplifiers  62 A through  62 D before being sent to difference amplifier  63 Y for detecting the angular velocity around the Y axis. 
     The acceleration in the direction of the X axis can be cancelled before being sent to I-V conversion amplifiers  62 A to  62 D, while the acceleration in the direction of the Y axis can be canceled before being amplified by difference amplifier  63 Z. 
     As described above, detectors  41  to  48  are disposed symmetrically with respect to axis “C” parallel to the Y axis, and also with respect to axis “D” parallel to the X axis. This arrangement can cancel the drive signals, angular velocity components around the other axes, and acceleration components in the directions of the other axes, which are unwanted signals. 
     As shown in  FIG. 9 , an angular velocity detection device may further include drivers  67  to  74  on arms  21  to  24 .  FIG. 9  is a top view of angular velocity detection device  16 A as another example of the embodiment. In device  16 A, arms  21  to  24  can also vibrate in the Y axis direction, allowing the detection of the angular velocity around the X axis. The magnitude ω x  of the angular velocity around the X axis can be calculated by Mathematical Formula (3)
 
ω x =( S 1+ S 2+ S 3+ S 4)−( S 5+ S 6+ S 7+ S 8)  (3)
 
     Thus, the provision of drivers  67  to  74  allows the detection of the angular velocities around the three axes at the same time. Furthermore, drive signals, angular velocities around the other axes, and accelerations in the directions of the other axes, which are unwanted signals, can be cancelled with each other during the detection of the angular velocity around each axis. 
     In angular velocity detection devices  16  and  16 A according to the embodiment, arms  21  to  24  having weights  25  to  28  are supported by central beam portion  20 B, which is in turn supported by inner beam portion  20 A Inner beam portion  20 A is supported by outer beam portions  18 A and  18 B via joints  19 A and  19 B. This configuration enables device  16 A to detect the angular velocities around the three axes at the same time, but has the disadvantage of being susceptible to acceleration and impact. For this reason, the effect of cancelling angular velocities around the other axis and accelerations in the directions of the other axes is particularly evident in the device structure of device  16 A. Furthermore, the influence of the external stress can be reduced by suspending the sensing part inside the outer frame, with first slits  80 A and  80 B therebetween. 
     As shown in  FIGS. 1A and 9 , fixed portions  17 A and  17 B are disposed as an opposing pair with outer beam portions  18 A and  18 B therebetween. Outer beam portions  18 A and  18 B are disposed as an opposing pair with fixed portions  17 A and  17 B therebetween. In this configuration, joints  19 A and  19 B are preferably formed in two positions where outer beam portions  18 A,  18 B and inner beam portion  20 A are parallel to each other. In this case, the sensing part can be suspended in the outer frame regardless of the direction in which device  16  is disposed. 
     Under the condition that outer beam portions  18 A and  18 B are subjected to no stress in the direction parallel thereto, joints  19 A and  19 B may be formed in two positions where fixed portions  17 A,  17 B and inner beam portion  20 A are parallel to each other. 
     Another angular velocity detection device of the embodiment is now described as follows.  FIG. 10  is a top view of angular velocity detection device  16 B as another example of the embodiment. The following description will be focused on the difference between devices  16  and  16 A shown in  FIGS. 1A and 9  and device  16 B. 
     Device  16 B includes detectors  76  and  78  on the side of inner beam portion  20 A that faces fixed portion  17 A via first slit  80 B. Detector  76  is near arm  21 , and detector  78  is near arm  23 . Device  16 B further include detectors  77  and  79  on the side of inner beam portion  20 A that faces fixed portion  17 B via first slit  80 A. Detector  77  is near arm  22  and detector  79  is near arm  24 . Detectors  76  and  78  are disposed symmetrical to detectors  77  and  79  with respect to axis “C”, while detectors  76  and  77  are disposed symmetrical to detectors  78  and  79  with respect to axis “D”. Device  16 B is otherwise identical to device  16 A shown in  FIG. 9 . Detectors  76  to  79  function to detect the angular velocity around the X axis applied to device  16 B. 
     In  FIG. 11 , the signals to be output from detectors  76  to  79  are referred to as S 9  to S 12 , respectively.  FIG. 11  specifically shows the following: the phases of the drive signals of the detectors; the phases in the case where angular velocities are applied around the X, Y, and Z axes; and the phases in the case where accelerations are applied in the X, Y, and Z axes directions, with respect to the phases of the drive signals provided by driving circuit  50 . 
     From  FIG. 11 , the magnitude ω x2  of the angular velocity around the X axis can be calculated by Mathematical Formula (4)
 
ω x2 =( S 9+ S 11)−( S 10+ S 12).  (4)
 
     When the phases in the cases that each one of the drive signals, angular velocities around the Y and Z axes, and accelerations in the X, Y, and Z axes is applied are substituted into Mathematical Formula (4), the results become 0. Thus, angular velocities around the other axes and accelerations in the directions of the other axes, which are unwanted signals, are cancelled with each other by the calculation of Mathematical Formula (4). 
     As known from  FIG. 11 , in the case where detectors  76  to  79  are disposed on inner beam portion  20 A in such a manner as to be symmetrical with respect to axes “C” and “D”, no drive signals appear on detectors  76  to  79 . Thus, the influence of drive signals can be eliminated by unwanted signals, without adding the signals from the plurality of detectors. 
     In the configuration shown in  FIGS. 1A and 9 , if detectors  41  to  48  are displaced with respect to the outer frame, drive signals cannot be cancelled by performing the calculation of Mathematical Formula (1), (2), or (3). In device  16 B, on the other hand, even if detectors  76  to  79  are displaced with respect to the outer frame, the influence of the drive signal components can be eliminated. Similarly, angular velocities around the Y and Z axes, and acceleration in the Y axis direction, which are unwanted signals, do not appear on detectors  41  to  48 , thereby providing the same effect. 
     As described above, detectors  76  to  79  can be disposed symmetrically with respect to axes “C” and “D” to eliminate or cancel drive signals, angular velocity components around the other axes, and acceleration components in the directions of the other axes, which are unwanted signals. 
     Thus, angular velocity detection device  16 B extends in the X-Y plane defined by the X and Y axes where X, Y, and Z axes are orthogonal to each other. It is preferable that detectors  41  to  48  disposed on arms  21  to  24  are used as angular velocity detectors around the Z axis, and that detectors  76  to  79  for detecting the angular velocity around the X axis are disposed on the sides of inner beam portion  20 A. The sides of inner beam portion  20 A are parallel to fixed portions  17 A and  17 B. 
     Another angular velocity detection device of the embodiment is now described as follows.  FIG. 12  is a top view of angular velocity detection device  16 C according to the present embodiment. The following description will be focused on the difference between device  16 C and devices  16 ,  16 A shown in  FIGS. 1A and 9 . 
     Angular velocity detection device  16 C includes detectors  81  to  84  in central beam portion  20 B. Detector  81  is near arm  21 , detector  82  is near arm  22 , detector  83  is near arm  23 , and detector  84  is near arm  24 . Device  16 C is otherwise identical to device  16 A shown in  FIG. 9 . Detectors  81  and  83  are disposed symmetrical to detectors  82  and  84  with respect to axis “C”, while detectors  81  and  82  are disposed symmetrical to detectors  83  and  84  with respect to axis “D”. Detectors  81  to  84  function to detect the angular velocity around the Y axis applied to device  16 C. 
     In  FIG. 13 , the signals to be output from detectors  81  to  84  are referred to as signals S 13  to S 16 , respectively.  FIG. 13  specifically shows the following: the phases of the drive signals of the detectors; the phases in the case where angular velocities are applied around the X, Y, and Z axes; and the phases in the case where accelerations are applied in the X, Y, and Z axes directions, with respect to the phases of the drive signals provided by driving circuit  50 . 
     From  FIG. 13 , the magnitude ω y2  of the angular velocity around the Y axis can be calculated by Mathematical Formula (5)
 
ω y2 =( S 13+ S 15)−( S 14+ S 16)  (5)
 
     When the phases in the cases that each one of the drive signals, angular velocities around the X and Z axes, and accelerations in the directions of the X, Y, and Z axes is applied are substituted into Mathematical Formula (5), the results become 0. Thus, angular velocities around the other axes and accelerations in the directions of the other axes, which are unwanted signals, are cancelled with each other by the calculation of Mathematical Formula (5). 
     As known from  FIG. 13 , in the case where detectors  81  to  84  are disposed on central beam portion  20 B in such a manner as to be symmetrical with respect to axes “C” and “D”, no drive signals appear on detectors  81  to  84 . Thus, the influence of drive signals can be eliminated by unwanted signals, without adding the signals from the plurality of detections. In the configuration shown in  FIGS. 1A and 9 , if detectors  41  to  48  are displaced with respect to the outer frame, drive signals cannot be cancelled by performing the calculation of Mathematical Formula (1), (2), or (3). In device  16 C, on the other hand, even if detectors  81  to  84  are displaced with respect to the outer frame, the influence of the drive signal components can be eliminated. Similarly, angular velocities around the X and Z axes, and acceleration in the direction of the X axis, which are unwanted signals, do not appear on detectors  81  to  84 , thereby providing the same effect. 
     As described above, detectors  81  to  84  can be disposed symmetrically with respect to axes “C” and “D” to eliminate or cancel drive signals, angular velocity components around the other axes, and acceleration components in the directions of the other axes, which are unwanted signals. 
     Another angular velocity detection device of the embodiment is now described as follows.  FIG. 14  is a partial top view of angular velocity detection device  16 G of the embodiment. The following description will be focused on the difference between device  16 G and devices  16 ,  16 A shown in  FIGS. 1A and 9 . 
     Angular velocity detection device  16 G differs from angular velocity detection device  16  shown in  FIG. 1A  in the shape of arms and the arrangement of drivers and detectors.  FIG. 14  shows the shape of first arm (hereinafter, arm)  211  as an example. Although not shown, second, third, and fourth arms, which respectively correspond to arms  22 ,  23 , and  24  shown in  FIG. 1A , have the same shape as arm  211 . These arms have the same symmetrical relationship as in angular velocity detection device  16 . 
     Arm  211  includes first end  211 A, first corner  211 B, and second corner  211 C. First end  211 A is connected to central beam portion  20 B. In short, arm  211  has first arm portion  211 E, second arm portion  211 F, and third arm portion  211 G, which together form the shape of the letter “J”. First arm portion  211 E extends between first end  211 A and first corner  211 B. Second arm portion  211 F extends between first corner  211 B and second corner  211 C. Third arm portion  211 G extends between second corner  211 C and second end  211 D. Second end  211 D is connected to weight  25 . Weight  25  is connected to arm  211  in such a manner that an extension of the outer side of third arm portion  211 G is coincident with one side of weight  25  having a substantially square shape. 
     Arm  211  and weight  25  can perform drive oscillation in the X-Y plane, and can bend in the Z axis direction. Arm  211  and weight  25  are made of the same material as those shown in  FIG. 1A . 
     Drivers  29  and  30  are disposed on first arm portion  211 E. Detectors  41  and  42  are disposed on second arm portion  211 F. Detectors  41 ,  42  and drivers  29 ,  30  have the same configuration as those shown in  FIG. 1A . Arm  211  can perform drive oscillation in the X-Y plane by applying anti-phase voltages to drivers  29  and  30 , respectively. 
     The principle of this angular velocity detection device is now described. When an external driving circuit (not shown) applies an AC voltage having a resonance frequency of drive oscillation to drivers  29  and  30 , arm  211  and weight  25  perform drive oscillation along a drive oscillation direction D 1  in the X-Y plane. If an angular velocity is applied around the Z axis at this moment, Coriolis force is generated in the direction at right angles with the drive oscillation direction D 1 . The Coriolis force excites detection oscillation in a detection oscillation direction D 2  in synchronization with the drive oscillation. Detectors  41  and  42  detect the distortion of arm  211  caused by the detection oscillation as a displacement of arm  211 , thereby detecting the angular velocity. 
     In general, the resonance frequency of detection oscillation in the detection oscillation direction D 2  is set close to the resonance frequency of drive oscillation in the drive oscillation direction D 1 . The reason for this is as follows. The detection oscillation generated when an angular velocity is applied is in synchronization with drive oscillation. As a result, as the resonance frequency of detection oscillation is closer to a resonance frequency of drive oscillation, the detection oscillation is excited more. 
     However, since the drive oscillation direction D 1  and the detection oscillation direction D 2  are different from each other, it is difficult to make the resonance frequency of drive oscillation and that of detection oscillation close to each other. For example, when the resonance frequency of drive oscillation in angular velocity detection device  16  shown in  FIG. 1A  is designed to be about 40 kHz, the resonance frequency of detection oscillation is about 65 kHz. This means that these resonance frequencies are 25 kHz apart from each other, decreasing the sensitivity of the angular velocity around the Z axis. 
     In contrast, in the configuration shown in  FIG. 14 , the length W 1  of arm  211  in the X axis direction is set larger than the length W 2  of weight  25  in the X axis direction. As a result, when an angular velocity is applied around the Z axis during the detecting resonance oscillation, the stiffness can be lower at second corner  211 C and its vicinity where stress tends to be concentrated, allowing the resonance frequency of the detecting resonance oscillation to be lower. In an angular velocity detection device with this configuration, when the resonance frequency of drive oscillation is 40 kHz, the resonance frequency of detection oscillation can be about 45 kHz. Thus, the difference between these resonance frequencies can be 5 kHz or less, thereby allowing the angular velocity around the Z axis to be detected at about five times as high sensitivity as angular velocity detection device  16 . 
     As shown in  FIG. 14 , width  211 K of second arm portion  211 F may be smaller than width  211 H of first arm portion  211 E. With this configuration, the stiffness can be low at second corner  211 C and its vicinity, allowing the resonance frequencies of drive oscillation and detection oscillation to be close to each other. Width  211 J of third arm portion  211 G may be smaller than width  211 K of second arm portion  211 F. Alternatively, first corner  211 B may have a radius of curvature larger than that of second corner  211 C. With these configurations, the resonance frequencies of drive oscillation and detection oscillation can be close to each other for the same reason. These configurations are effective alone, but the resonance frequencies of drive oscillation and detection oscillation can be much closer when used in combination. This can further increase the sensitivity of the angular velocity around the Z axis. 
     When arm  211  and weight  25  are made to perform drive oscillation in the drive oscillation direction D 1 , the distortion tends to be concentrated in first arm portion  211 E. Therefore, the provision of drivers  29  and  30  in first arm portion  211 E can improve drive efficiency. 
     Similarly, when arm  211  and weight  25  are made to perform detection oscillation in the detection oscillation direction D 2 , the distortion tends to be concentrated in second arm portion  211 F. Therefore, the provision of detectors  41  and  42  in second arm portion  211 F can improve detection efficiency. Arm  211  performs drive oscillation along the drive oscillation direction D 1 , and performs detection oscillation along the detection oscillation direction D 2 . Hence, detectors  41  and  42  may be disposed on third arm portion  211 G to detect the detection oscillation. 
     As described above, the resonance frequency of the drive oscillation and that of the detection oscillation of an angular velocity around the Z axis can be close to each other in the angular velocity detection device. As a result, the angular velocity around the Z axis can be detected at a high sensitivity. 
     Another angular velocity detection device of the embodiment is now described.  FIG. 15  is a top view of angular velocity detection device  16 D according to the embodiment. The following description will be focused on the difference between device  16 D and device  16 G shown in  FIG. 14 . 
     Angular velocity detection device  16 D includes detectors  91  to  94  for detecting an angular velocity around the Y axis on the sides of inner beam portion  20 A. The sides are parallel to outer beam portions  18 A and  18 B. Device  16 D is otherwise identical to device  16 G. 
     Thus, detectors  91  to  94  can be disposed on the sides of inner beam portion  20 A that are parallel to outer beam portions  18 A and  18 B to make central beam portion  20 B thin, allowing unwanted resonance frequencies in the X-Y plane to be low. This can increase the difference between the unwanted resonance frequencies and the resonance frequency of drive oscillation, allowing accurate detection of detection oscillation based on drive oscillation. 
     This configuration can also be applied to angular velocity detection devices  16 ,  16 A,  16 B, and  16 C shown in  FIGS. 1A, 9, 10, and 12 , respectively. In short, detectors  81  to  84  shown in  FIG. 12  can be replaced by detectors  91  to  94 . 
     Thus, when X, Y, and Z axes are orthogonal to each other, angular velocity detection device  16 D extends in the X-Y plane defined by the X and Y axes. It is preferable that detectors  41  to  48  disposed on arms  211  to  214  are used as angular velocity detectors around the Z axis, and that detectors  91  to  94  for detecting the angular velocity around the X axis are disposed on the sides of inner beam portion  20 A that are parallel to outer beam portions  18 A and  18 B. 
     Detectors  76  to  79  for detecting the angular velocity around the X axis are disposed on the sides of inner beam portion  20 A. is the sides are parallel to fixed portions  17 A and  17 B. This configuration has an effect similar to the configuration shown in  FIG. 9 . 
     Other angular velocity detection devices of the embodiment are now described as follows.  FIGS. 16A and 16B  are top views of angular velocity detection devices  16 E and  16 F, respectively, of the embodiment. The following description will be focused on the difference between devices  16 E,  16 F and device  16 D shown in  FIG. 15 . 
     In angular velocity detection device  16 E shown in  FIG. 16A , inner beam portion  20 A has second slits  96 A to  96 D adjacent to detectors  91  to  94  disposed on the sides of inner beam portion  20 A that are parallel to outer beam portions  18 A and  18 B. 
     In order to improve the sensitivity of detectors  91  to  94 , detectors  91  to  94  need to have a larger area. However, an increase in the width of inner beam portion  20 A for the purpose of increasing the area of detectors  91  to  94  would result in an increase in the stiffness of inner beam portion  20 A. This would then cause the unwanted resonance frequencies of arms  211  to  214  to get closer to the drive frequency, thereby inducing an unstable vibrational state and decreasing measurement accuracy. 
     To avoid this situation, the configuration shown in  FIG. 16A  includes second slits  96 A to  96 D. This can decrease the stiffness of inner beam portion  20 A, while increasing the area of detectors  91  to  94  relative to the area of the top surface of inner beam portion  20 A. As a result, the difference between the drive frequency of arms  211  to  214  and the unwanted resonance frequencies can be increased while improving the sensitivity of detectors  91  to  94 . 
     Inner beam portion  20 A is stiffer near the corners than near the center of each side. For this reason, in order to increase the difference between the drive frequency of arms  211  to  214  and the unwanted resonance frequencies, it is preferable to form second slits  96 A to  96 D near the corners of inner beam portion  20 A. 
     It is further preferable that second slits  96 A to  96 D are right trapezoids when viewed from the above, each having an upper base, a lower base longer than the upper base, and an oblique side connecting the upper and lower bases and that the lower base is on the outer side in the direction of the width of inner beam portion  20 A, and the oblique side is near a corner of inner beam portion  20 A. Second slits  96 A to  96 D having such a shape facilitate the adjustment of the stiffness of inner beam portion  20 A and the sensitivity of detectors  91  to  94 . 
     In angular velocity detection device  16 F shown in  FIG. 16B , on the other hand, inner beam portion  20 A has second slits  98 A to  98 D adjacent to detectors  76  to  79  disposed on the sides of inner beam portion  20 A. The sides are parallel to fixed portions  17 A and  17 B. 
     Similar to the case shown in  FIG. 16A , in order to improve the sensitivity of detectors  76  to  79 , detectors  76  to  79  need to have a larger area. However, an increase in the width of inner beam portion  20 A for the purpose of increasing the area of detectors  76  to  79  would result in an increase in the stiffness of inner beam portion  20 A. This would then cause the unwanted resonance frequencies of arms  211  to  214  to get closer to the drive frequency, thereby inducing an unstable vibrational state and decreasing measurement accuracy. 
     More specifically, the difference between the drive frequency of arms  211  to  214  and the unwanted resonance frequencies is 500 Hz or above, and more preferably, 1000 Hz or above. Device  16 F needs to be reduced in size with decreasing size of the apparatuses on which device  16 F is mounted. However, as device  16 F is smaller, its mass is smaller, causing the unwanted resonance frequencies to increase and get closer to the drive frequency. 
     To avoid this situation, the configuration shown in  FIG. 16B  is provided with second slits  98 A to  98 D. This can decrease the stiffness of inner beam portion  20 A, while increasing the area of detectors  76  to  79  relative to the area of the top surface of inner beam portion  20 A. As a result, the difference between the drive frequency of arms  211  to  214  and the unwanted resonance frequencies can be increased while improving the sensitivity of detectors  76  to  79 . 
     Specifically, in the case where angular velocity detection device  16 F has a size of about 2.5×2.5 mm, its base is made of 150 μm thick Si, and its drive frequency is about 40 kHz, the frequency difference is about 1000 Hz. This effect is provided independently of the effect of the presence of first slits  80 A and  80 B. 
     Inner beam portion  20 A is stiffer near the corners than near the center of each side. For this reason, in order to increase the difference between the drive frequency of arms  211  to  214  and the unwanted resonance frequencies, it is preferable to form second slits  98 A to  98 D near the corners of inner beam portion  20 A. In the configuration shown in  FIG. 16B , there are no joints between fixed portions  17 A,  17 B and inner beam portion  20 A, allowing high detection sensitivity at the position of inner beam portion  20 A near central beam portion  20 B. Thus, detectors  76  to  79  can detect the angular velocity around the X axis at a high sensitivity by the arrangement of detectors  76  to  79  in the vicinity of the regions of inner beam portion  20 A where inner beam portion  20 A is connected to central beam portion  20 B. Second slits  98 A to  98 D can be formed near the corners of inner beam portion  20 A where little contribution is made to improve the sensitivity. 
     It is more preferable that second slits  98 A to  98 D are right trapezoids when viewed from the above, each having an upper base, a lower base longer than the upper base, and an oblique side connecting the upper and lower bases and that the lower base is on the outer side in the direction of the width of inner beam portion  20 A, and the oblique side is near a corner of inner beam portion  20 A. Second slits  98 A to  98 D having such a shape facilitate the adjustment of the stiffness of inner beam portion  20 A and the sensitivity of detectors  76  to  79 . When needed, both second slits  96 A to  96 D shown in  FIG. 16A  and second slits  98 A to  98 D shown in  FIG. 16B  may be formed. 
     The configuration shown in  FIGS. 16A and 16B  can also be applied to angular velocity detection devices  16 ,  16 A,  16 B, and  16 C shown in  FIGS. 1A, 9, 10, and 12 , respectively. In short, detectors  81  to  84  shown in  FIG. 12  can be replaced by detectors  91  to  94 , and in addition, second slits  96 A to  96 D can be formed. Furthermore, in the configuration shown in  FIG. 10 , detectors  76  to  79  may be disposed close to central beam portion  20 B, and in addition, second slits  98 A to  98 D may be formed. 
     In the above description, the angular velocity sensor includes driving circuit  50 , detecting circuit  61 , and one of angular velocity detection devices  16  to  16 F. However, driving circuit  50  and detecting circuit  61  do not have to be incorporated into the angular velocity sensor. At least either driving circuit  50  or detecting circuit  61  can be incorporated into an apparatus where the angular velocity sensor is installed. 
     As described above, the angular velocity sensors of the embodiments are useful for mobile terminals and vehicles because it can cancel unwanted signals due, for example, to acceleration, thereby having high detection accuracy of the angular velocity.