JPH06331362A - Vibration gyroscope - Google Patents

Abstract

PURPOSE:To reduce the generation of noises attributed to demodulation by a third vibration mode. CONSTITUTION:An H-shaped vibrator has four arms. The H-shaped vibrator has a first mode (a) in which the arms vibrate longitudinally as viewed from the front of the H shape thereof and a second mode (b) and a third mode (c) in which the arms vibrate horizontally. A resonance frequency of the first mode (a) is separated sufficiently from the resonance frequencies of the second mode (b) and the third mode (c) because of difference in the direction of vibration. Therefore, the resonance frequency of the third mode (c) is separated sufficiently from the resonance frequency of the drive mode (a). When a vibration gyroscope is carried on a vehicle, the vibration of the vehicle (external vibration) is transmitted to the vibrator but the vibration of the third mode will not be generated easily. Thus, there is limited possibility of generating noises attributed to the demodulation by the vibration of the third mode with respect to the output signal of the piezo-electric element for detection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration gyro having a third vibration mode other than a drive mode and a detection mode in which a vibrator vibrates when a Coriolis force acts. Vibrating gyro with.

[0002]

2. Description of the Related Art FIG. 4 is an external view of a conventional vibrating gyro, FIG.
FIG. 6 shows a vibration mode of the vibrator, and FIG. 6 shows a vibration gyro output regarding noise generation in this vibration gyro. The vibration gyro 1 has four arms 2 each having a rectangular cross section with a vertical dimension m and a horizontal dimension n, and an H-shaped vibrator 3 having a height dimension h,
The driving piezoelectric elements 4 are attached to the left and right outer sides of each arm 2 when viewed from the front of the H-shape, and the detecting piezoelectric elements 5 are attached to the front side of each arm 2.

The H-shaped vibrator 3 has a first mode in which the arm 2 vibrates back and forth when viewed from the front of the H-shape as shown in FIG. 5 (a), and as shown in FIG. The arms 2 vibrate in the left and right directions opposite to each other and the upper and lower arms 2 vibrate.
The second mode also vibrates in the left and right directions opposite to each other. As shown in FIG. 5C, the left and right arms 2 vibrate in the opposite directions and vibrate in the left and right directions.
There are vibration modes of the third mode that vibrate in the same direction in the left and right directions. Since the second mode and the third mode are vibrations in the left-right direction as well, their resonance frequencies are close to each other. On the other hand, since the vibration direction of the first mode is different from the vibration directions of the second mode and the third mode at right angles, the resonance frequency of the first mode is sufficiently separated from the resonance frequencies of the second mode and the third mode. .

In the conventional driving / detecting method of the vibration gyro 1 described above, the vibrator 3 is driven by the driving piezoelectric element 4 as shown in FIG.
When vibrating in the drive mode (second mode) b of (b), an angular velocity is applied to this oscillator 3 and a Coriolis force acts,
This is a method of vibrating in the detection mode (first mode) a of (a), and the detection piezoelectric element 5 detects the vibration of this detection mode a. In the conventional vibrator 3, the drive mode b
The difference between the resonance frequency of the
It was about 0 Hz. This is because when the resonance frequency of the drive mode b and the resonance frequency of the detection mode a are brought close to each other, the sensitivity of the vibration gyro becomes high, and when both resonance frequencies are too close, noise due to external vibration becomes large. In consideration of the above, the compromise was set to about 120 Hz.

[0005]

By the way, when the conventional vibration gyro 1 is mounted on, for example, a vehicle, when the external vibration due to the vibration of the vehicle is applied to the driving vibration gyro 1, the resonance frequency of the drive mode b is increased. Vibration of the third mode c having an approximate resonance frequency easily occurs. This third
When the vibration of the mode c occurs, the vibration of the third mode c amplitude-modulates the output signal of the detection piezoelectric element 5, and this becomes noise due to external vibration. This is shown in FIG. FIG. 6A shows the gyro output when a shock is applied, and FIG. 6B shows the Null signal at that time. As shown,
Noise due to amplitude modulation of the output signal of the detection piezoelectric element 5 by the vibration of the third mode c is clearly generated.

The present invention has been made to solve the above-mentioned conventional drawbacks, and is caused by the modulation by the third vibration mode when the vibrator has the third vibration mode other than the drive mode and the detection mode. An object is to provide a vibration gyro with less noise generation.

[0007]

According to the present invention for solving the above-mentioned problems, a vibrating gyroscope having a third vibrating mode in addition to two vibrating modes in which a vibrating mode thereof has a relationship between a driving mode and a detecting mode. In the drive mode of the vibrator, a vibration mode whose resonance frequency is farthest from the resonance frequencies of other vibration modes is selected.

According to a second aspect of the invention, in the vibrating gyroscope according to the first aspect, the difference between the resonance frequency of the drive mode of the vibrator and the resonance frequency of the other vibration mode is set to 200 Hz or more.

[0009]

In the above structure, even if external vibration is applied to the vibrator vibrating in the drive mode, the resonance frequency in the drive mode is sufficiently separated from the resonance frequency in the third mode.
It is unlikely that the amplitude modulation is performed by the third mode vibration. Therefore, it is unlikely that noise due to modulation will occur.

Since the frequency of vibration that can occur in a normal vehicle (mainly an automobile) is about 0 to 200 Hz, if the difference between the resonance frequency of the drive mode of the vibrator and the resonance frequency of other vibration modes is 200 Hz or more. The risk of amplitude modulation due to the above-mentioned third vibration mode is eliminated, and noise generation in the vibration gyro when mounted on a vehicle is reduced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an external view of the vibration gyro of the present invention, FIG. 2 shows a vibration mode of the vibrator, and FIG. 3 shows a vibration gyro output regarding noise generation in the vibration gyro. The vibrating gyro 11 has four arms 12 each having a rectangular cross section.
Each arm 1 with a H-shaped vibrator 13 when viewed from the front of the H-shape
Piezoelectric elements 15 for detection are attached to the outer sides of the left and right sides of 2, and the piezoelectric elements 1 for driving are attached to the front side of each arm 12.
4 is pasted. Note that it is possible to omit some of the numbers of the detection piezoelectric elements 15 and the driving piezoelectric elements 14. The dimensions of each part of the vibrator 11 are the same as those of the vibrator 1
The vertical dimension m of the rectangular cross section of the arm 12 of FIG.
The vertical dimension m is the same as the horizontal dimension n '
Is smaller than the lateral dimension n. The height h of the vibrator 11 is the same as the conventional one. Therefore, the difference between the resonance frequency of the first mode a of the vibrator 11 and the resonance frequency of the second mode b is
It is larger than the difference of b. The difference between the resonance frequency of the first mode a and the resonance frequency of the second mode b is about 120 Hz in the past, but is set to about 200 Hz, for example.
The frequency of 200 Hz is usually because the frequency of the vibration that can occur in the vehicle (automobile) is about 0 to 200 Hz, whereby the vibration of the third mode c when the vibration gyro is mounted in the vehicle ( The resonance frequency is the second mode b
(Which is close to the resonance frequency of) is less likely to occur.

As can be seen from how to attach the detecting piezoelectric element 15 and the driving piezoelectric element 14 to the arm 12 of the vibrator 11, the first mode a is the driving mode and the second mode b is the detecting mode in the present invention. Therefore, in the present invention, the resonance frequency of the third mode c is as shown in FIG.
As described in the above description, it is sufficiently separated from the resonance frequency of the drive mode a which is the first mode.

In the vibrating gyro 11, when the driving piezoelectric element 14 is driven, the vibrator 13 vibrates in the driving mode (first mode) a shown in FIG. 2A, and an angular velocity is applied to the vibrator 13 to cause Coriolis. When a force is applied, the vibrator 11 vibrates in the detection mode (second mode) b in FIG. 2B, and the detection piezoelectric element 5 detects the vibration in the detection mode b. When this vibration gyro 11 is mounted on a vehicle, for example, when external vibration due to vibration of the vehicle is applied to the driving vibration gyro 11, the resonance frequency of the third mode c is sufficiently larger than the resonance frequency of the drive mode a as described above. Since they are separated from each other, the vibration of the third mode c does not easily occur. Therefore, it is unlikely that the vibration of the third mode c amplitude-modulates the output signal of the detection piezoelectric element 5 to generate noise due to external vibration. The situation is shown in FIG. FIG. 3A shows the gyro output when a shock is applied, and FIG. 3B shows the Null signal at that time. As shown in the figure, there is no noise in which the vibration of the third mode c amplitude-modulates the output signal of the detection piezoelectric element 15.

The difference between the resonance frequencies of the first mode a, which is the driving mode, and the second mode b, which is the detection mode, may be set appropriately depending on the object on which the vibrating gyro is mounted. That is, the resonance frequency difference may be set to exceed the frequency range of mechanical vibration that can occur in the object to be mounted.

[0015]

According to the present invention, the vibrator is in the drive mode
In the vibration gyro having the third vibration mode other than the detection mode, the vibration mode whose resonance frequency is farthest from the resonance frequencies of the other vibration modes is selected as the driving mode of the vibrator. Even if external vibration is applied, the third vibration mode rarely occurs. Therefore, the output signal of the detecting piezoelectric element is less likely to be amplitude-modulated by the vibration of the third vibration mode, and the noise due to this modulation is less likely to occur.

According to the vibration gyro of the present invention, the difference between the resonance frequency of the drive mode of the vibrator and the resonance frequency of the other vibration modes exceeds a frequency range of 200 Hz which can occur in a normal vehicle. Therefore, there is no fear of amplitude modulation due to the third vibration mode, and the noise generation of the vibration gyro when mounted on a vehicle is reduced.

[Brief description of drawings]

FIG. 1 is a perspective view of a vibrating gyroscope showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a vibration mode of a vibrator of the vibration gyro of the present invention.

FIG. 3 is a diagram of a vibration gyro output related to noise generation in the vibration gyro of the present invention.

FIG. 4 is a perspective view of a conventional vibrating gyro.

FIG. 5 is an explanatory diagram of a vibration mode of a vibrator of a conventional vibration gyro.

FIG. 6 is a diagram of a vibration gyro output related to noise generation in a conventional vibration gyro.

[Explanation of symbols]

 11 Vibration Gyro 12 Arm 13 Vibrator 14 Driving Piezoelectric Element 15 Detecting Piezoelectric Element

Claims (2)

[Claims] 1. A vibrating gyroscope having a third vibrating mode in addition to two vibrating modes in which the vibrating mode has a relationship between a driving mode and a detecting mode, wherein the vibrating mode of the vibrating element has a resonance frequency as a driving mode. The vibration gyro is characterized in that the vibration mode selected is the farthest from the resonance frequency of other vibration modes. 2. The vibration gyro according to claim 1, wherein a difference between a resonance frequency of a drive mode of the vibrator and a resonance frequency of another vibration mode is set to 200 Hz or more.