Tuning fork type gyroscope

A tuning fork type gyroscope including plate members spaced apart from each other, vibration elements for vibrating the plate members, suspension members for suspending the plate members, and electrodes arranged in the lower portion of the plate members, wherein the suspension members comprises: main bars connected to the plate members by connection members; fixing members connected to both ends of each of said main bars so as to support the main bars and reduce (a) restoring tensile forces(s) along the length of the main bars; and a supporting member connected to (a) central portion(s) of the main bars so as to support the main bars. The gyroscope reduces the restoring tensile force of the main bars and provides flexibility to the main bars.

BACKGROUND OF THE INVENTION 
The present invention relates to a gyroscope, and more particularly, to a 
tuning fork type gyroscope. 
A gyroscope for detecting the angular velocity of an inertial object has 
been employed as a core part of a navigation apparatus for guided 
missiles, sea-going vessels or aircraft. Applications for the gyroscope 
have been extended to fields such as a navigation apparatus for 
automobiles and an apparatus for detecting and correcting hand quiver in a 
high-magnification camcorder. A conventional gyroscope employed for 
detecting the angular velocity is manufactured by assembling a multitude 
of complex parts requiring precise machining. Thus, due to the 
conventional gyroscope having burdensome manufacturing costs and a large 
structure, the conventional gyroscope is not suitable for general 
industrial purposes or in-home electronics. 
A comb driven tuning fork type microgyroscope, shown in FIG. 1, developed 
by The Charles Stark Draper Laboratory, is disclosed in U.S. Pat. No. 
5,349,855. Here, a solid and dotted line-hatched portions represent 
electrodes (terminals) and a fixed structure, respectively, and unhatched 
portion represents suspended structure, as shown in FIG. 1. 
Referring to FIG. 1, combs 102a and 102b are formed on either side of a 
plate member 101a and combs 102c and 102d are formed on either side of a 
plate member 101b. Main bars 104a and 104b are connected to the plate 
members 101a and 101b by connection members 103a and 103b, and are 
supported by fixing portions 105a and 105b. Fixing structures 106a, 106b 
and 106c have combs 107a, 107b, 107c and 107d each meshed with the combs 
102a, 102b, 102c and 102d of the plate members 101a and 101b at intervals 
of predetermined distance, respectively. 
Electrodes 108a and 108b are disposed in the lower part of the plate 
members 101a and 101b, and terminals 109a, 109b, 109c, 109d and 109e each 
apply a voltage to the fixing structures 106a, 106b and 106c and the 
electrodes 108a and 108b, respectively. 
In the above-mentioned gyroscope, when an alternating current (AC) voltage 
is applied to the terminals 109a, 109b, 109c, 109d and 109e, an 
electrostatic force is generated between the combs 102a, 102b, 102c and 
102d and the combs 107a, 107b, 107c and 107d of the fixing structures 
106a, 106b and 106c, to thereby vibrate the plate members 101a and 101b 
along the X-axis. The combs 107b and 107c of the fixing structure 106b are 
used for detecting the positions of the plate members 101a and 101b on the 
X-axis. At this time, if the gyroscope rotates around the Y-axis with the 
angular velocity .OMEGA., the plate members 101a and 101b are acted on by 
a Coriolis force in the Z-axis. Accordingly, the plate members 101a and 
101b are displaced along the Z-axis, and the angular velocity .OMEGA. is 
detected by measuring the capacitance difference according to the change 
in distance between the plate members 101a and 101b and the electrodes 
108a and 108b. 
In the conventional gyroscope as mentioned above, since only the middle 
portions of the main bars 104a and 104b are supported, the displacement of 
the plate members 101a and 101b in the Z-axis due to the Coriolis force is 
not uniform. Thus, the change of capacitance according to the displacement 
of the plate members 101a and 101b in the Z-axis becomes non-linear. 
In another conventional gyroscope, as shown in FIG. 2, a pair of parallel 
main bars 201a and 201b are provided, both ends of which are supported by 
fixing portions 202a, 202b, 202c and 202d. 
However, in operation of such a gyroscope, plate members 203a and 203b and 
electrodes 204a and 204b do not maintain a uniform distance therebetween. 
Further, as shown in FIG. 3, the displacement of the middle portions of 
the main bars 201a and 201b is large causing the distance between the 
plate members 203a and 203b and electrodes 204a and 204b to become 
non-uniform, thereby producing noise. Also, since the main bars 201a and 
201b are fixed at both ends respectively, when the displacement is large, 
the restoring tensile force along the length of the main bars 201a and 
201b becomes larger than the Coriolis force, which is undesirable. 
Moreover, when the plate members 203a and 203b vibrate up and down, it is 
preferable that the main bars 201a and 201b have torsional flexibility to 
a certain extent. However, the main bars 201a and 201b remain rigid 
because they are fixed by fixing portions 202a, 202b, 202c and 202d. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a tuning 
fork type gyroscope for reducing a restoring tensile force along the 
length of a main bar which occurs as displacement in a Z-axis direction of 
plate members becomes large, and for removing non-linearity of the change 
in capacitance according to an angular velocity. 
To achieve the above objects, there is provided a tuning fork type 
gyroscope comprising plate members spaced apart from each other, vibration 
means for vibrating the plate members, suspension means for suspending the 
plate members, and electrodes arranged in the lower portion of the plate 
members, wherein the suspension means comprises: main bars connected to 
the plate members by connection members; fixing means connected to either 
end of the main bar so as to support the main bar and reduce a restoring 
tensile force along the length of the main bar; and supporting means 
connected to the middle portion of the main bar so as to support the main 
bar.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 4 shows (an embodiment of) a tuning fork type gyroscope according to 
the present invention. Here, the same reference numerals are used for 
elements that are the same as that of FIG. 1. 
Referring to FIG. 4, vibration means for vibrating plate members 101a and 
101b include combs 102a, 102b, 102c and 102d, respectively, protruding 
from either side of the plate members 101a and 101b, other combs 107a, 
107b, 107c and 107d each meshed with the plate member combs 102a, 102b, 
102c and 102d at intervals of a predetermined distance, respectively, and 
terminals 109a, 109b, 109c, 109d and 109e for applying electric power to 
the combs 102a-102d and 107a-107b. Suspension means for suspending the 
plate members 101a and 101b with respect to the upper portion of 
electrodes 108a and 108b include: main bars 401a and 401b on which 
connection members 103a and 103b connected to the plate members 101a and 
101b are formed; fixing means 410 connected to both ends of the main bars 
401a and 401b, respectively for supporting the main bars 401a and 401b and 
reducing the restoring tensile force of the main bars 401a and 401b by 
allowing the main bars 401a and 401b to be relaxed in the length 
direction; and supporting means 420 for supporting the middle portions of 
the main bars 401a and 401b. 
The fixing means 410 includes a buffer portion 411 extending 
perpendicularly from the ends of the main bars 401a and 401b and a fixing 
portion 412 connected to the buffer portion 411 and fixed to the circuit 
board (not shown). 
Other embodiments of the fixing means 410 are shown in FIGS. 5 through 7. 
Referring to FIG. 5, a main bar 501a is connected to a fixing portion 512 
by a rectangular ring-shaped buffer portion (511). The buffer portion 511 
may have at least one U-shaped bending portion 511a as shown in FIG. 6 so 
as to buffer the tensile force along the length of the main bar 501a. In 
FIG. 7, there is provided a square wave-shaped buffer portion 711. 
The supporting means 420 of FIG. 4 has distortion bars 421a and 421b 
extending perpendicularly from either side of the middle portions of the 
main bars 401a and 401b, i.e. the portions of the main bars 401a and 401b 
having the largest displacement during vibration, and fixing portions 422a 
and 422b connected to ends of the distortion bars 421a and 421b and fixed 
to the circuit board. 
Other embodiments of the supporting means 420 (in FIG. 4) are shown in 
FIGS. 8 and 9. In FIG. 8, connection bars 821a extend perpendicularly from 
either side of a main bar 801a. A rectangular ring-shaped distortion 
portion 821b which is connected to a fixing portion 822 is connected with 
end of the connection bar 821a so as to provide additional flexibility. In 
FIG. 9, the supporting means 420 (in FIG. 4) includes connection bars 921a 
extending perpendicularly from either side of a main bar 901a, the 
distortion bars 921b extending perpendicularly from either side of ends of 
the connection bars 921a and are bent inward at their ends, and fixing 
portions 922 to which the bent ends of the distortion bars 921b are 
connected. 
The fixing means and the supporting means are not limited to the disclosed 
embodiments but any structure which reduces the restoring tensile force 
and distortion as the plate member vibrates may be included in the present 
invention. 
According to the present invention, as shown in FIG. 4, it is preferable 
that the connection members 103a and 103b for supporting the plate members 
101a and 101b be placed at portions of the main bars 401a and 401b where 
the displacement of the main bars 401a and 401b in a Z-axis direction is 
maximum. 
Referring to FIG. 10, in operation of the gyroscope according to the 
present invention, when the main bars 401a and 401b vibrate, the distance 
between the plate members 101a and 101b and the electrodes 108a and 108b 
is uniform. Thus, the change of capacitance according to the change in 
angular velocity is linear. 
In the tuning fork type gyroscope according to the present invention, when 
the plate member vibrates, the fixing means and the supporting means 
reduce the restoring tensile force along the length of the main bar and 
maintains a uniform distance between the plate member and the electrode, 
to thereby prevent noise and detect the angular velocity more accurately. 
It is noted that the present invention is not limited to the preferred 
embodiment described above, and it is apparent that variations and 
modifications by those skilled in the art can be effected within the 
spirit and scope of the present invention defined in the appended claims.