Measuring and testing – Speed – velocity – or acceleration – Angular rate using gyroscopic or coriolis effect
Reexamination Certificate
2001-07-05
2003-04-01
Moller, Richard A. (Department: 2856)
Measuring and testing
Speed, velocity, or acceleration
Angular rate using gyroscopic or coriolis effect
C073S514320
Reexamination Certificate
active
06539803
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an external force measuring device suitable for use in detection of, e.g., an angular velocity, an acceleration, and so forth.
2. Description of the Related Art
In general, as external force measuring devices, angular velocity sensors have been known, each of which comprises a substrate, a mass supported displaceably in two orthogonal directions on the substrate via supporting beams, a vibration generating means for vibrating the mass in a vibration-direction parallel to the substrate in one of the two directions, and an angular velocity detection means for detecting the displacement of the mass caused when the mass is displaced in a detection-direction perpendicular to the vibration-direction (for example, Japanese Unexamined Patent Application Publication No. 5-312576).
In an angular velocity sensor produced in such a first conventional technique, the mass is vibrated at a predetermined amplitude, e.g., in the X-axial direction of the X and Y axial directions parallel to the substrate. In this state, if an angular velocity on the Z axis is applied, a Coriolis force acts on the mass, so that the mass is displaced in the Y-axial direction. Therefore, the angular velocity detection means detects the displacement of the mass as a variation in electrostatic capacitance or the like to output a detection signal corresponding to the angular velocity.
In this case, the mass is supported displaceably (vibration) in the X-axial direction and so forth by the supporting beams provided on the substrate. The supporting beams are fixed to the substrate on the base-ends thereof. The top ends thereof are connected to the mass. When the angular velocity sensor is operated, the supporting beams are deflected, and thereby, the mass is vibrated in the X-axial direction.
In a second conventional technique described, e.g., in Japanese Unexamined Patent Application PublicationNo. 7-218268, an angular velocity sensor, called a tuning fork, is used. A pair of masses, arranged on a substrate, are vibrated at opposite phases to each other. The vibration to be transmitted from the masses to the substrate via supporting beams is canceled out by means of a pair of the masses.
In this case, the supporting beams which support a pair of the masses have complicated shapes having plural flexed portions so that each of the masses can be supported at one site on the substrate. Moreover, the top ends of the supporting beams are branched and connected to the respective masses.
In the above-described first conventional technique, the mass is connected to the substrate via the supporting beams. Therefore, when the mass is vibrated on the substrate, the vibration is readily transmitted to the substrate side via the supporting beams.
For this reason, when the angular velocity sensor is operated, vibration energy is leaked toward the substrate side, so that the amplitudes and the vibration velocity of the mass are reduced, and a Coriolis force caused by the angular velocity is decreased. As a result, the detection sensitivity may be unstable. Moreover, when the vibration is transmitted to the substrate, the mass may be vibrated in the detection direction, due to vibration of the substrate, though no angular velocity is applied to the mass. Thus, this causes the problem that errors are readily generated in detection values of the angular velocity, and the reliability is deteriorated.
On the other hand, in the second conventional technique, the pair of masses are vibrated at opposite phases, so that the vibration to be transmitted to the substrate side is canceled out. However, these masses are supported by supporting beams having complicated flexed shapes. Therefore, in production of the sensor, it is difficult to render the supporting beams, e.g., the sizes, shapes, characteristics at deflecting, and so forth evenly with respect to the masses provided on the opposite sides.
For this reason, in the second conventional technique, dispersions in size and errors in working or the like of the supporting beams may cause a difference between the vibration states of the pair of the masses. Thus, there arises the problems that vibration of the respective masses transmitted to the substrate side cannot be stably canceled out.
On the other hand, when the angular velocity sensor is operated, and an acceleration in the Y-axial direction is added to the sensor, due to an external force of collision or the like, the masses may be displaced in the Y-axial direction, caused by not only the Coriolis force caused by the angular velocity but also the inertial force by the acceleration. Thus, the displacement comprising the angular velocity component and the acceleration component is detected as the angular velocity.
As a result, in the first conventional technique, even if collision or the like is slightly added to the angular velocity sensor, for example, the acceleration component, caused by the collision or the like, is contained as an error in an angular velocity detection signal, which deteriorates the detection accuracy of the angular velocity. Thus, there arises the problem that the reliability is enhanced with difficulty.
Especially, in the case in which the acceleration to be added to the sensor has a frequency component of which the frequency is near the vibration frequency of the masses, an error, caused by the acceleration component, can not be securely eliminated even if the detection signal is synchronously rectified and integrated at a constant period corresponding to the vibration frequency to carry out the signal processing such as synchronous detection or the like which extracts the angular velocity component.
SUMMARY OF THE INVENTION
In view of the above-described problems of the conventional techniques, the present invention has been devised. It is a first object of the present invention to provide an external measuring device in which vibration of masses can be prevented from being transmitted to the substrate side via supporting beams, the vibration state can be stably kept on the substrate, and moreover, the detection sensitivity and detection accuracy and reliability can be enhanced.
Moreover, it is a second object of the present invention to provide an external force measuring device in which even if both of the angular velocity and the acceleration are applied to the masses, at least the angular velocity can be accurately detected, separately from the acceleration, and the detection operation can be stabilized.
To solve the above-described problems, according to a first aspect of the present invention, there is provided an external force measuring device which comprises a substrate, plural masses opposed to and spaced from the substrate, arranged along the Y-axial direction of three orthogonal axial directions, that is, X-, Y-, and Z-axial directions, such as to be vibratable in the X-axial direction at opposite phases to each other by a vibration generator; supporting beams connecting the respective masses displaceably in the X-axial direction, fixing portions provided between the supporting beams and the substrate, and an external force detector for detecting, as the angular velocity or acceleration, a displacement of the respective masses in one of the Y-axial and Z-axial directions, caused when an angular velocity or an acceleration acts on the respective masses.
Owing to the above-described configuration, the plural masses can be connected by the supporting beams in the Y-axial direction perpendicular to the vibration direction (X-axial direction). For example, a part of the masses are vibrated by means of the vibration generator, and thereby, neighboring masses can be vibrated substantially at opposite phases. Thereby, on the sites in the middles of the supporting beams connecting the masses, the nodes of vibration can be arranged at which the supporting beams are positioned substantially constantly when the supporting beams, together with the respective masses, are vibrated.
Moreover, for example, two masses to be vibrat
Keating & Bennett LLP
Moller Richard A.
Murata Manufacturing Co. Ltd.
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