Patent Publication Number: US-2006016261-A1

Title: Angular velocity sensor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2004-212943, filed on Jul. 21, 2004, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates generally to an angular velocity sensor, and, more particularly, to a multi-axis angular velocity sensor using a quadruped or H-shaped tuning fork.  
      2. Description of the Related Art  
      Various types have been proposed so far as a piezoelectric angular velocity sensor. One of such types is configured to have a protrusion at the tip portion of a tripod tuning fork type oscillator so as to enable detection of the angular velocities of a plurality of axes (see, e.g., Japanese Patent Application Laid-Open Publication No. 2002-213963).  
      On the other hand, another type is configured to have a weight portion, adapted to detect angular velocities, formed at the center of a disk-shaped piezoelectric element so as to detect the angular velocities of a plurality of axes (see, e.g., Japanese Patent Application Laid-Open Publication No. 1996-94661).  
      Still another type is known that is configured to have four oscillating arms formed by a common supporting portion, with two inner or outer oscillating arms used as drive arms and the other two as sensing arms (see, e.g., Japanese Patent Application Laid-Open Publication No. 1996-278142).  
      However, the angular velocity sensor in the first conventional example, having a tripod tuning fork structure with a protrusion, lacks simplicity in manufacture, and if the sensor is rendered multiaxial to detect the angular velocities of the respective axes, the electrode area becomes smaller. This likely leads to increased impedance.  
      On the other hand, the configuration in the second conventional example has a drawback in terms of manufacturing cost because of the structural complexity involved in forming the weight portion on the disk-shaped piezoelectric element.  
      Further, the third conventional example is designed to detect the angular velocity of only a single axis and cannot detect the angular velocities of a plurality of axes.  
     SUMMARY OF THE INVENTION  
      In light of the above, it is an object of the present invention to provide an angular velocity sensor that can be manufactured by a simple method and reduced in size and height and that can detect the angular velocities of a plurality of axes with a single element.  
      A first aspect of the angular velocity sensor for achieving the object of the present invention is characterized in that it has a base portion formed by a piezoelectric single crystal and having a length in the Y-axis direction and a thickness in the Z-axis direction, and four beams each having a length in the Y-axis direction vertical to the X- and Z-axis directions that are arranged side by side in the X-axis direction and formed by the piezoelectric single crystal integrally with the base portion, that the four beams are grouped in two pairs with one in each pair used as a drive beam and the other a counterbalance, that the drive beams are provided with drive electrodes adapted to oscillate the beams in the X-axis direction and Y-axis sensing electrodes adapted to detect the rotation angle applied around the Y-axis, and that the other beams serving as counterbalances are provided with X-axis sensing electrodes adapted to detect the rotation angle applied around the X-axis.  
      A second aspect of the angular velocity sensor for achieving the object of the present invention is characterized in that, in the first embodiment, the drive electrodes are electrodes formed on both surfaces of the drive beams vertical to the Z-axis direction with a drive signal applied between the drive electrodes, that the Y-axis sensing electrodes are electrodes formed on the surfaces of the drive beams vertical to the Z-axis direction separately from the drive electrodes and electrodes formed on the surfaces of the drive beams vertical to the X-axis direction so that outputs between these electrodes are detected as the rotation angle applied around the Y-axis, and that the X-axis sensing electrodes are electrodes formed on the surfaces of the other beams serving as counterbalances vertical to the Z-axis direction and electrodes formed on both surfaces thereof vertical to the X-axis direction so that outputs between these electrodes are detected as the rotation angle applied around the X-axis.  
      A third aspect of the angular velocity sensor for achieving the object of the present invention is characterized in that, in the second embodiment, Z-axis sensing electrodes are formed on the both.surfaces of the other beams serving as counterbalances vertical to the Z-axis direction separately from the X-axis sensing electrodes formed on the both surfaces of the other beams serving as counterbalances vertical to the Z-axis direction so that outputs between these electrodes are detected as the rotation angle applied around the Z-axis.  
      A fourth aspect of the angular velocity sensor for achieving the object of the present invention is characterized in that, in any of the first to third embodiments, the four beams are formed on one side of the base portion relative to the Z-axis direction to form a comb shape.  
      A fifth aspect of the angular velocity sensor for achieving the object of the present invention is characterized in that, in any of the first to third embodiments, the two pairs of the four beams are formed so as to be opposed to each other in the Z-axis direction with the base portion therebetween to form an H shape.  
      The features of the present invention will become more apparent from the embodiments which will be described below with reference to the drawings.  
      According to the present invention there is provided an angular velocity sensor that is simple in structure, easy to manufacture, compact and short to allow mounting in a flat position, and capable of detecting the angular velocities of a plurality of axes with a single element. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other objects, aspects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which:  
       FIG. 1A  is a view illustrating the conceptual configuration of a quadruped tuning fork type oscillator of a first embodiment according to the present invention;  
       FIG. 1B  is a cross-sectional view along line a-a′ of  FIG. 1A  illustrating the connection of drive and sensing electrodes;  
       FIG. 2A  is an explanatory view of the condition in an Fz mode in the first embodiment;  
       FIG. 2B  is a cross-sectional view along line a-a′ of  FIG. 2A  illustrating the connection of the drive and sensing electrodes;  
       FIG. 3A  is an explanatory view of the condition in an Fz′ mode in the first embodiment;  
       FIG. 3B  is a cross-sectional view along line a-a′ of  FIG. 3A  illustrating the connection of the drive and sensing electrodes;  
       FIG. 4A  is a view illustrating the conceptual configuration of the quadruped tuning fork type oscillator of a second embodiment according to the present invention;  
       FIG. 4B  is a cross-sectional view along line a-a′ of  FIG. 4A  illustrating the connection of the drive and sensing electrodes;  
       FIG. 5A  is an explanatory view of the condition in the Fz mode in the second embodiment;  
       FIG. 5B  is a cross-sectional view along line a-a′ of  FIG. 5A  illustrating the connection of the drive and sensing electrodes;  
       FIG. 6A  is an explanatory view of the condition in the Fz′ mode in the second embodiment;  
       FIG. 6B  is a cross-sectional view along line a-a′ of  FIG. 6A  illustrating the connection of the drive and sensing electrodes;  
       FIG. 7A  is a view illustrating the conceptual configuration of the quadruped tuning fork type oscillator of a third embodiment according to the present invention;  
       FIG. 7B  is a cross-sectional view along line a-a′ of  FIG. 7A  illustrating the connection of the drive and sensing electrodes;  
       FIG. 8A  is an explanatory view of the condition in the Fz mode in the third embodiment;  
       FIG. 8B  is a cross-sectional view along line a-a′ of  FIG. 8A  illustrating the connection of the drive and sensing electrodes;  
       FIG. 9A  is an explanatory view of the condition in the Fz′ mode in the third embodiment;  
       FIG. 9B  is a cross-sectional view along line a-a′ of  FIG. 9A  illustrating the connection of the drive and sensing electrodes;  
       FIG. 10A  is a view illustrating the conceptual configuration of the quadruped tuning fork type oscillator of a fourth embodiment according to the present invention;  
       FIG. 10B  is a cross-sectional view along line a-a′ of  FIG. 10A  illustrating the connection of the drive and sensing electrodes;  
       FIG. 11A  is an explanatory view of the condition in the Fz mode in the fourth embodiment;  
       FIG. 11B  is a cross-sectional view along line a-a′ of  FIG. 11A  illustrating the connection of the drive and sensing electrodes;  
       FIG. 12A  is an explanatory view of the condition in the Fz′ mode in the fourth embodiment;  
       FIG. 12B  is a cross-sectional view along line a-a′ of  FIG. 12A  illustrating the connection of the drive and sensing electrodes;  
       FIG. 13A  is a view illustrating the conceptual configuration of an H-shaped tuning fork type oscillator of a fifth embodiment according to the present invention;  
       FIG. 13B  is a cross-sectional view along lines a-a′ and b-b′ of  FIG. 13A  illustrating the connection of the drive and sensing electrodes;  
       FIG. 14A  is an explanatory view of the condition in the Fz mode in the fifth embodiment;  
       FIG. 14B  is a cross-sectional view along lines a-a′ and b-b′ of  FIG. 14A  illustrating the connection of the drive and sensing electrodes;  
       FIG. 15A  is an explanatory view of the condition in the Fz′ mode in the fifth embodiment;  
       FIG. 15B  is a cross-sectional view along lines a-a′ and b-b′ of  FIG. 15A  illustrating the connection of the drive and sensing electrodes;  
       FIG. 16A  is a view illustrating the conceptual configuration of the H-shaped tuning fork type oscillator of a sixth embodiment according to the present invention;  
       FIG. 16B  is a cross-sectional view along lines a-a′ and b-b′ of  FIG. 16A  illustrating the connection of the drive and sensing electrodes;  
       FIG. 17A  is an explanatory view of the condition in the Fz mode in the sixth embodiment;  
       FIG. 17B  is a cross-sectional view along lines a-a′ and b-b′ of  FIG. 17A  illustrating the connection of the drive and sensing electrodes;  
       FIG. 18A  is an explanatory view of the condition in the Fz′ mode in the sixth embodiment;  
       FIG. 18B  is a cross-sectional view along lines a-a′ and b-b′ of  FIG. 18A  illustrating the connection of the drive and sensing electrodes; and  
       FIG. 19  is a view illustrating how to install the angular velocity sensor according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The embodiments of the present invention will now be described with reference to the accompanying drawings. It is to be noted that the embodiments are provided only for the purposes of understanding the present invention and that the technical scope of the present invention is not limited thereto.  
       FIGS. 1A  to  3 B are views illustrating a first embodiment of the present invention.  FIG. 1A  is a view illustrating the conceptual configuration of a quadruped tuning fork type oscillator, whereas  FIG. 1B  is a cross-sectional view along line a-a′ of  FIG. 1A  illustrating the connection of drive and sensing electrodes.  
      As the common configuration, embodiments to be described below all have a base portion  1  cut out from a piezoelectric single crystal and having a length in the Y-axis direction and a thickness in the Z-axis direction, and four beams  2   a,    2   b,    2   c  and  2   d  formed by the piezoelectric single crystal integrally with the base portion  1  and each having a length in the Y-axis direction vertical to the X- and Z-axis directions, and arranged side by side in the X-axis direction.  
      Single crystal elements with a large electromechanical coupling coefficient are preferred for use as the piezoelectric single crystal from the viewpoint of high sensitivity and size reduction, and lithium niobate (LiNbO 3 ), lithium tantalate (LiTaO 3 ), potassium niobate (KNbO 3 ) and quartz (SiO 2 ) are among the materials that can be used.  
      In the first embodiment, of the four beams, the beams  2   a  and  2   b  are paired, and the beams  2   c  and  2   d  are paired, with one in each pair or the beams  2   a  and  2   d  used as drive beams and the other or the beams  2   b  and  2   c  as counterbalances, as illustrated in  FIG. 1B .  
      The beam  2   a  has drive electrodes  3   a   1  and  3   a   2  formed on the surfaces vertical to the Z-axis direction, whereas the beam  2   d  has drive electrodes  3   b   1  and  3   b   2  formed on the surfaces vertical to the Z-axis direction. A drive signal is supplied between the drive electrodes  3   a   1  and  3   a   2  and between the drive electrodes  3   b   1  and  3   b   2  from terminals T 1  and T 2 .  
      This causes the drive beams  2   a  and  2   d  to be excited in the X-axis direction, and the counterbalance beams  2   b  and  2   c  to oscillate in the opposite direction in the X-axis direction, as illustrated in  FIG. 1A . This mode is defined as an Fx mode.  
       FIGS. 2A and 2B  are explanatory views of application of a rotational force around the Y-axis in the Fx mode illustrated in  FIGS. 1A and 1B . In  FIG. 2A , if a rotational force is applied around the Y-axis in the Fx mode, the drive beams  2   a  and  2   d  and the counterbalance beams  2   b  and  2   c  are displaced in the directions indicated by the arrows, that is, in opposite directions in the Z-axis direction, due to Corioli&#39;s force. This condition is defined as an Fz mode. Therefore, the detection of the displacements in the Fz mode allows detection of the rotation angle applied around the Y-axis.  
      To detect the displacements of the drive beams  2   a  and  2   d  in the Z-axis direction in the Fz mode, the sensing electrodes are connected in the cross-sectional view along line a-a′ of  FIG. 2A  as illustrated in  FIG. 2B .  
      In  FIG. 2B , electrodes  4   a   1  and  4   b   1  are formed on the surfaces of the drive beams  2   a  and  2   d  vertical to the X-axis, and electrodes  4   a   2 ,  4   a   3 ,  4   b   2  and  4   b   3  on the surfaces of the drive beams  2   a  and  2   d  vertical to the Z-axis. If the outputs between the electrodes  4   a   1  and  4   a   2 , and  4   a   1  and  4   a   3  and those between the electrodes  4   b   1  and  4   b   2 , and  4   b   1  and  4   b   3  are found from terminals T 3  and T 4 , the displacements in the Fz mode can be detected.  
      Similarly,  FIGS. 3A and 3B  are explanatory views of application of a rotational force around the X-axis in the Fx mode illustrated in  FIGS. 1A and 1B . In  FIG. 3A , when a rotational force is applied around the X-axis in the Fx mode, the drive beams  2   a  and  2   d  and the counterbalance beams  2   b  and  2   c  are displaced in the directions indicated by the arrows, that is, in opposite directions in the Z-axis direction, due to Corioli&#39;s force. This condition is defined as an Fz′ mode. Therefore, the detection of the displacements in the Fz′ mode allows detection of the rotation angle applied around the X-axis.  
      To detect the displacements of the counterbalance beams  2   b  and  2   c  in the Z-axis direction in the Fz′ mode, the sensing electrodes are connected in the cross-sectional view along line a-a′ of  FIG. 3A  as illustrated in  FIG. 3B .  
      In  FIG. 3B , electrodes  5   a   1 ,  5   a   2 ,  5   b   1  and  5   b   2  are formed on the surfaces of the counterbalance beams  2   b  and  2   c  vertical to the X-axis, and electrodes  6   a   1 ,  6   a   2 ,  6   b   1  and  6   b   2  on the surfaces of the counterbalance beams  2   b  and  2   c  vertical to the Z-axis. If the outputs between the electrodes  5   a   1  and  6   a   1 , and  5   a   1  and  6   a   2  and those between the electrodes  5   b   2  and  6   b   1 , and  5   b   2  and  6   b   2  are found from terminals T 5  and T 6 , the displacements in the Fz′ mode can be detected.  
      As described above, the first embodiment allows detection of the rotation angles of two axes or the Y- and X-axes, and therefore, the angular velocities of these axes in the Fz and Fz′ modes with a single element.  
      Next,  FIGS. 4A  to  6 B are views illustrating a second embodiment of the present invention. The second embodiment is identical to the first embodiment in that it is configured with the base portion  1  and the four beams  2   a,    2   b,    2   c  and  2   d  formed integrally with the base portion  1 .  
       FIG. 4A  is a view illustrating the conceptual configuration of the quadruped tuning fork type oscillator, whereas  FIG. 4B  is a cross-sectional view along line a-a′ of  FIG. 4A  illustrating the connection of the drive electrodes.  
      In the second embodiment, of the four beams, the beams  2   a  and  2   b  are paired, and the beams  2   c  and  2   d  are paired, with one in each pair or the beams  2   b  and  2   c  used as the drive beams and the other or the beams  2   a  and  2   d  as the counterbalances, as illustrated in  FIG. 4B .  
      The beam  2   b  has drive electrodes  6   a   1  and  6   a   2  formed on the surfaces vertical to the Z-axis direction, whereas the beam  2   c  has drive electrodes  6   b   1  and  6   b   2  formed on the surfaces vertical to the Z-axis direction. A drive signal is supplied between the drive electrodes  6   a   1  and  6   a   2  and between the drive electrodes  6   b   1  and  6   b   2  from terminals T 11  and T 21 .  
      This causes the drive beams  2   b  and  2   c  to be excited in the X-axis direction, and the counterbalance beams  2   a  and  2   d  to oscillate in the opposite direction in the X-axis direction, as illustrated in  FIG. 4A . This mode is defined as the Fx mode.  
       FIGS. 5A and 5B  are explanatory views of application of a rotational force around the Y-axis in the Fx mode illustrated in  FIGS. 4A and 4B . In  FIG. 5A , if a rotational force is applied around the Y-axis in the Fx mode, the drive beams  2   b  and  2   c  and the counterbalance beams  2   a  and  2   d  are displaced in the directions indicated by the arrows, that is, in opposite directions in the Z-axis direction, due to Corioli&#39;s force. This condition, identical to that illustrated in  FIG. 2A , is the Fz mode. Therefore, the detection of the displacements in the Fz mode allows detection of the rotation angle applied around the Y-axis.  
      To detect the displacements of the drive beams  2   b  and  2   c  in the Z-axis direction in the Fz mode, the sensing electrodes are connected in the cross-sectional view along line a-a′ of  FIG. 5A  as illustrated in  FIG. 5B .  
      In  FIG. 5B , the electrodes  5   a   1  and  5   b   1  are formed on the surfaces of the drive beams  2   b  and  2   c  vertical to the X-axis, and electrodes  6   a   3 ,  6   a   4 ,  6   b   3  and  6   b   4  on the surfaces of the drive beams  2   b  and  2   c  vertical to the Z-axis. If the outputs between the electrodes  5   a   1  and  6   a   3 , and  5   a   1  and  6   a   4  and those between the electrodes  5   b   1  and  6   b   3 , and  5   b   1  and  6   b   4  are found from terminals T 31  and T 41 , the displacements in the Fz mode can be detected.  
      Similarly,  FIGS. 6A and 6B  are explanatory views of application of a rotational force around the X-axis in the Fx mode illustrated in  FIGS. 4A and 4B . In  FIG. 6A , when a rotational force is applied around the X-axis in the Fx mode, the drive beams  2   b  and  2   c  and the counterbalance beams  2   a  and  2   d  are displaced in the directions indicated by the arrows, that is, in opposite directions in the Z-axis direction, due to Corioli&#39;s force. This condition, identical to that illustrated in  FIG. 3A , is the Fz′ mode. Therefore, the detection of the displacements in the Fz′ mode allows detection of the rotation angle applied around the X-axis.  
      To detect the displacements of the counterbalance beams  2   a  and  2   d  in the Z-axis direction in the Fz′ mode, the sensing electrodes are connected in the cross-sectional view along line a-a′ of  FIG. 6A  as illustrated in  FIG. 6B .  
      In  FIG. 6B , electrodes  4   a   1 ,  4   a   4 ,  4   b   1  and  4   b   4  are formed on the surfaces of the counterbalance beams  2   a  and  2   d  vertical to the X-axis, and electrodes  4   a   2 ,  4   a   3 ,  4   b   2  and  4   b   3  on the surfaces of the counterbalance beams  2   a  and  2   d  vertical to the Z-axis. If the outputs between the group of the electrodes  4   a   1 ,  4   a   4 ,  4   b   1  and  4   b   4  and the group of the electrodes  4   a   2 ,  4   a   3 ,  4   b   2  and  4   b   3  are found from terminals T 51  and T 61 , the displacements in the Fz′ mode can be detected.  
      As described above, the second embodiment allows detection of the rotation angles of two axes or the Y- and X-axes, and therefore, the angular velocities of these axes in the Fz and Fz′ modes with a single element, as with the first embodiment.  
      Next, description will be given of a configuration example operable to detect the angular velocities of three axes with a single element as a third embodiment with reference to  FIGS. 7A  to  9 B.  
      The third embodiment is identical to the first and second embodiments in that it is configured with the base portion  1  and the four beams  2   a,    2   b,    2   c  and  2   d  formed integrally with the base portion  1 .  
       FIG. 7A  is a view illustrating the conceptual configuration of the quadruped tuning fork type oscillator, whereas  FIG. 7B  is a cross-sectional view along line a-a′ of  FIG. 7A  illustrating the connection of the drive electrodes.  
      In the third embodiment, of the four beams, the beams  2   a  and  2   b  are paired, and the beams  2   c  and  2   d  are paired, with one in each pair or the beams  2   a  and  2   d  used as the drive beams and the other or the beams  2   b  and  2   c  as the counterbalances, as illustrated in  FIG. 7B .  
      The beam  2   a  has the drive electrodes  3   a   1  and  3   a   2  formed on the surfaces vertical to the Z-axis direction, whereas the beam  2   d  has the drive electrodes  3   b   1  and  3   b   2  formed on the surfaces vertical to the Z-axis direction. A drive signal is supplied between the drive electrodes  3   a   1  and  3   a   2  and between the drive electrodes  3   b   1  and  3   b   2  from the terminals T 11  and T 21 .  
      This causes the drive beams  2   a  and  2   d  to be excited in the X-axis direction, and the counterbalance beams  2   b  and  2   c  to oscillate in the opposite direction in the X-axis direction, as illustrated in  FIG. 7A . This mode is the Fx mode.  
       FIGS. 8A and 8B  are explanatory views of application of a rotational force around the Y-axis in the Fx mode illustrated in  FIGS. 7A and 7B . In  FIG. 8A , if a rotational force is applied around the Y-axis in the Fx mode, the drive beams  2   a  and  2   d  and the counterbalance beams  2   b  and  2   c  are displaced in the directions indicated by the arrows, that is, in opposite directions in the Z-axis direction, due to Corioli&#39;s force. This condition, identical to that illustrated in  FIG. 2A , is the Fz mode. Therefore, the detection of the displacements in the Fz mode allows detection of the rotation angle applied around the Y-axis.  
      To detect the displacements of the drive beams  2   a  and  2   d  in the Z-axis direction in the Fz mode, the sensing electrodes are connected in the cross-sectional view along line a-a′ of  FIG. 8A  as illustrated in  FIG. 8B .  
      In  FIG. 8B , the electrodes  4   a   1  and  4   b   1  are formed on the surfaces of the drive beams  2   a  and  2   d  vertical to the X-axis, and the electrodes  4   a   2 ,  4   a   3 ,  4   b   2  and  4   b   3  on the surfaces of the drive beams  2   a  and  2   d  vertical to the Z-axis. If the outputs between the electrodes  4   a   1  and  4   a   2 , and  4   a   1  and  4   a   3  and those between the electrodes  4   b   1  and  4   b   2 , and  4   b   1  and  4   b   3  are found from the terminals T 3  and T 4 , the displacements in the Fz mode can be detected.  
      Similarly,  FIGS. 9A and 9B  are explanatory views of application of a rotational force around the X-axis in the Fx mode illustrated in  FIGS. 7A and 7B . In  FIG. 9A , when a rotational force is applied around the X-axis in the Fx mode, the drive beams  2   a  and  2   d  and the counterbalance beams  2   b  and  2   c  are displaced in the directions indicated by the arrows, that is, in opposite directions in the Z-axis direction, due to Corioli&#39;s force. This condition, identical to that illustrated in  FIG. 3A , is the Fz′ mode. Therefore, the detection of the displacements in the Fz′ mode allows detection of the rotation angle applied around the X-axis.  
      To detect the displacements of the counterbalance beams  2   b  and  2   c  in the Z-axis direction in the Fz′ mode, the sensing electrodes are connected in the cross-sectional view along line a-a′ of  FIG. 9A  as illustrated in  FIG. 9B .  
      In  FIG. 9B , the electrodes  5   a   1  and  5   b   1  are formed on the surfaces of the counterbalance beams  2   b  and  2   c  vertical to the X-axis, and the electrodes  6   a   1 ,  6   a   2 ,  6   b   1  and  6   b   2  on the surfaces of the counterbalance beams  2   b  and  2   c  vertical to the Z-axis. If the outputs between the electrodes  5   a   1  and  6   a   1 , and  5   a   1  and  6   a   2  and those between the electrodes  5   b   1  and  6   b   1 , and  5   b   1  and  6   b   2  are found from the terminals T 5  and T 6 , the displacements in the Fz′ mode can be detected.  
      Further in  FIG. 9A , when a rotational force is applied around the Z-axis, the drive beams  2   a  and  2   d  and the counterbalance beams  2   b  and  2   c  are displaced in the directions indicated by the up and down arrows, that is, in opposite directions in the Y-axis direction, due to Corioli&#39;s force. This condition is defined as an Fy mode.  
      Therefore, the detection of the displacements in the Fy mode allows detection of the rotation angle applied around the Z-axis.  
      To detect the displacements of the counterbalance beams  2   b  and  2   c  in the Y-axis direction in the Fy mode, the sensing electrodes are connected in the cross-sectional view along line a-a′ of  FIG. 9A  as illustrated in  FIG. 9B .  
      In  FIG. 9B , electrodes  6   a   5 ,  6   a   6 ,  6   b   5  and  6   b   6  are further formed on the surfaces of the counterbalance beams  2   b  and  2   c  vertical to the Z-axis. If the output between the electrodes  6   a   5  and  6   a   6  and that between the electrodes  6   b   5  and  6   b   6  are found from terminals T 7  and T 8 , the displacements in the Fy mode can be detected.  
      As described above, the third embodiment allows detection of the rotation angles of three axes or the Y-, X- and Z-axes, and therefore, the angular velocities of these axes in the Fz, Fz′ and Fy modes with a single element.  
      Further, a modification of the third embodiment, operable to detect the angular velocities of three axes with a single element, is illustrated as a fourth embodiment in  FIGS. 10A  to  12 B. In contrast to the third embodiment, the fourth embodiment uses the beams  2   b  and  2   c  rather than the beams  2   a  and  2   d  as the drive beams, and therefore, the beams  2   a  and  2   d  as the counterbalance beams.  
      In  FIG. 10A , the fourth embodiment is identical to the first, second and third embodiments in that it is configured with the base portion  1  and the four beams  2   a,    2   b,    2   c  and  2   d  formed integrally with the base portion  1 .  
       FIG. 10A  is a view illustrating the conceptual configuration of a quadruped tuning fork type oscillator, whereas  FIG. 10B  is a cross-sectional view along line a-a′ of  FIG. 10A  illustrating the connection of the drive electrodes.  
      In the fourth embodiment, of the four beams, the beams  2   a  and  2   b  are paired, and the beams  2   c  and  2   d  are paired, with one in each pair or the beams  2   b  and  2   c  used as the drive beams and the other or the beams  2   a  and  2   d  as counterbalances, as illustrated in  FIG. 10B .  
      The beam  2   b  has the drive electrodes  6   a   1  and  6   a   2  formed on the surfaces vertical to the Z-axis direction, whereas the beam  2   c  has drive electrodes  6   b   1  and  6   b   2  formed on the surfaces vertical to the Z-axis direction. A drive signal is supplied between the drive electrodes  6   a   1  and  6   a   2  and between the drive electrodes  6   b   1  and  6   b   2  from the terminals T 11  and T 21 .  
      This causes the drive beams  2   b  and  2   c  to be excited in the X-axis direction, and the counterbalance beams  2   a  and  2   d  to oscillate in the opposite direction in the X-axis direction, as illustrated in  FIG. 10A . This mode is the Fx mode.  
       FIGS. 11A and 11B  are explanatory views of application of a rotational force around the Y-axis in the Fx mode illustrated in  FIGS. 10A and 10B . In FIG.  11 A, if a rotational force is applied around the Y-axis in the Fx mode, the drive beams  2   b  and  2   c  and the counterbalance beams  2   a  and  2   d  are displaced in the directions indicated by the arrows, that is, in opposite directions in the Z-axis direction, due to Corioli&#39;s force. This condition, identical to that illustrated in  FIG. 2A , is the Fz mode. Therefore, the detection of the displacements in the Fz mode allows detection of the rotation angle applied around the Y-axis.  
      To detect the displacements of the drive beams  2   b  and  2   c  in the Z-axis direction in the Fz mode, the sensing electrodes are connected in the cross-sectional view along line a-a′ of  FIG. 11A  as illustrated in  FIG. 11B .  
      In  FIG. 11B , the electrodes  5   a   1  and  5   b   1  are formed on the surfaces of the drive beams  2   b  and  2   c  vertical to the X-axis, and the electrodes  6   a   3 ,  6   a   4 ,  6   b   3  and  6   b   4  on the surfaces of the drive beams  2   b  and  2   c  vertical to the Z-axis. If the outputs between the electrodes  5   a   1  and  6   a   3 , and  5   a   1  and  6   a   4  and those between the electrodes  5   b   1  and  6   b   3 , and  5   b   1  and  6   b   4  are found from terminals T 31  and T 41 , the displacements in the Fz mode can be detected.  
      Similarly,  FIGS. 12A and 12B  are explanatory views of application of rotational forces around the X- and Z-axes in the Fx mode illustrated in  FIGS. 10A and 10B . In  FIG. 12A , when a rotational force is applied around the X-axis in the Fx mode, the drive beams  2   b  and  2   c  and the counterbalance beams  2   a  and  2   d  are displaced in the directions indicated by the arrows, that is, in opposite directions in the Z-axis direction, due to Corioli&#39;s force. This condition, identical to that illustrated in  FIG. 3A , is the Fz′ mode. Therefore, the detection of the displacements in the Fz′ mode allows detection of the rotation angle applied around the X-axis.  
      To detect the displacements of the counterbalance beams  2   a  and  2   d  in the Z-axis direction in the Fz′ mode, the sensing electrodes are connected in the cross-sectional view along line a-a′ of  FIG. 12A  as illustrated in  FIG. 12B .  
      In  FIG. 12B , the electrodes  4   a   1  and  4   b   1  are formed on the surfaces of the counterbalance beams  2   a  and  2   d  vertical to the X-axis, and the electrodes  4   a   2 ,  4   a   3 ,  4   b   2  and  4   b   3  on the surfaces of the counterbalance beams  2   a  and  2   d  vertical to the Z-axis. If the outputs between the electrodes  4   a   1  and  4   a   2 , and  4   a   1  and  4   a   3  and those between the electrodes  4   b   1  and  4   b   2 , and  4   b   1  and  4   b   3  are found from the terminals T 51  and T 61 , the displacements in the Fz′ mode can be detected.  
      Further in  FIG. 12A , when a rotational force is applied around the Z-axis, the drive beams  2   b  and  2   c  and the counterbalance beams  2   a  and  2   d  are displaced in the directions indicated by the up and down arrows, that is, in opposite directions in the Y-axis direction, due to Corioli&#39;s force. This condition is defined as the Fy mode.  
      Therefore, the detection of the displacements in the Fy mode allows detection of the rotation angle applied around the Z-axis.  
      To detect the displacements of the counterbalance beams  2   a  and  2   d  in the Y-axis direction in the Fy mode, the sensing electrodes are connected in the cross-sectional view along line a-a′ of  FIG. 12A  as illustrated in  FIG. 12B .  
      In  FIG. 12B , the electrodes  4   a   4 ,  4   a   5 ,  4   b   4  and  4   b   5  are further formed on the surfaces of the counterbalance beams  2   a  and  2   d  vertical to the Z-axis. If the output between the electrodes  4   a   4  and  4   a   5  and that between the electrodes  4   b   4  and  4   b   5  are found from terminals T 71  and T 81 , the displacements in the Fy mode can be detected.  
      As described above, the fourth embodiment also allows detection of the rotation angles of three axes or the Y-, X- and Z-axes, and therefore, the angular velocities of these axes in the Fz, Fz′ and Fy modes with a single element.  
      Here, the aforementioned embodiments all have a comb-shaped configuration with the beams formed integrally with the base portion  1  and arranged in the X-axis direction.  
      On the other hand, the present invention is also applicable to a configuration with two beams each arranged on the opposite sides of the base portion  1 , that is, an H-shaped configuration.  
       FIGS. 13A  to  15 B are views illustrating an embodiment having such an H-shaped configuration. This embodiment is configured with the drive beams  2   a  and  2   d  and the counterbalance beams  2   b  and  2   c  arranged on the opposite sides of the base portion  1  as illustrated in  FIG. 13A .  
      As illustrated in  FIG. 13B , a drive signal is supplied between the terminals T 1  and T 2  to cause excitation in the X-axis direction and, as a result, provide the Fx mode. In  FIGS. 14A and 14B  corresponding to  FIGS. 2A and 2B , therefore, the angular velocity around the Y-axis can be detected between the terminals T 3  and T 4 , thanks to the Fz mode that causes displacements in the Z-axis direction due to Corioli&#39;s force as illustrated in  FIG. 14A .  
      Further, in  FIGS. 15A and 15B  corresponding to  FIGS. 3A and 3B , the angular velocity around the X-axis can be detected between the terminals T 5  and T 6 , thanks to the Fz′ mode that causes displacements in the Z-axis direction due to Corioli&#39;s force as illustrated in  FIG. 15A .  
      As described above, the angular velocity sensor with the H-shaped configuration, to which the present invention is applied, can detect the angular velocities of two axes with a single element.  
      Further,  FIGS. 16A  to  18 B are views illustrating another embodiment having an H-shaped configuration that corresponds to the aforementioned third embodiment. Therefore,  FIGS. 16A  to  18 B correspond to  FIGS. 7A  to  9 B describing the third embodiment. This embodiment is configured with the drive beams  2   a  and  2   d  and the counterbalance beams  2   b  and  2   c  arranged on the opposite sides of the base portion  1  as illustrated in  FIG. 16A .  
      A drive signal is supplied between the terminals Tl and T 2  as illustrated in  FIG. 16B  to cause excitation in the X-axis direction and provide the Fx mode. In  FIGS. 17A and 17B  corresponding to  FIGS. 8A and 8B , therefore, the angular velocity around the Y-axis can be detected between the terminals T 3  and T 4 , thanks to the Fz mode that causes displacements in the Z-axis direction due to Corioli&#39;s force as illustrated in  FIG. 17A .  
      Further, in  FIGS. 18A and 18B  corresponding to  FIGS. 3A and 3B , the angular velocity around the X-axis can be detected between the terminals T 5  and T 6 , thanks to the Fz′ mode that causes displacements in the Z-axis direction due to Corioli&#39;s force as illustrated in  FIG. 18A .  
      Still further, in  FIGS. 18A and 18B , the angular velocity around the Z-axis can be detected between the terminals T 7  and T 8 , thanks to the Fy mode that causes displacements in the Y-axis direction due to Corioli&#39;s force as illustrated in  FIG. 18A .  
      As described above, the angular velocity sensor with the H-shaped configuration, to which the present invention is applied, can detect the angular velocities of three axes with a single element.  
       FIG. 19  is a view illustrating how to install the angular velocity sensor according to the present invention. In  FIG. 19 , (i) and (ii) for case (a) represent the sensor used as a two-axis sensor, whereas (i) and (ii) for case (b) represent the sensor used as a three-axis sensor. In either case, level placement on the XY plane provides a two-axis angular velocity sensor for the X- and Y-axes or a three-axis angular velocity sensor for the X-, Y- and Z-axes that can be reduced in height when packaged.  
      As described above with reference to the drawings, the present invention can provide an angular velocity sensor that is simple in structure, can be reduced in height and can detect the angular velocities of a plurality of axes with a single element. Therefore, the angular velocity sensor is applicable in a number of areas for downsizing of equipment, thus making a significant contribution to industry.  
      While illustrative and presently preferred embodiments of the present invention have been described in detail herein, it is to be understood that the inventive concepts may be otherwise variously embodied and employed and that the appended claims are intended to be construed to include such variations except insofar as limited by the prior art.