JPS5919861A - Angular velocity sensor - Google Patents

Abstract

PURPOSE:To detect an angular velocity without generating an offset, by fitting two tuning forks to the same side surface of a rigid body, and constituting so that each vibration surface becomes a right angle to each other. CONSTITUTION:The turning fork 5a and the tuning fork 5b are fitted to a supporting member 4a and 4b so that their vibration surfaces become a right angle to each other. When an electric power source having constant frequency being near resonance frequency of the tuning fork 5a is connected to piezoelectric elements 2a, 2b, the tuning fork 5a starts its vibration. When a prism 1 is rotated around its long axis, the tuning fork 5b is resonated by amplitude being proportional to an angular velocity by force operation on the prism 1 and Coriolis' force, and voltage being proportional to the angular velocity is generated from piezoelectric elements 2c, 3d. The vibration surfaces of the tuning fork 5a and 5b are fitted so as to become a right angle to each other, therefore, the vibration modes are entirely different, and no resonance is generated, therefore, the tuning fork 5b is not vibrated by vibration of the tuning fork 5a, and no offset is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an angular velocity sensor suitable for detecting the angular velocity of a rotating body or the like.

Conventionally, a vibrating gyroscope has been used as a sensor for detecting angular velocity. As shown in FIG. 1, piezoelectric elements 2a to 2b are attached to each side of a prism 1, and the prism 1 is supported by support members 3a and 3b. When a power source having a constant frequency is connected to the opposing piezoelectric elements 2a and 2b, the square column 1 vibrates in the zz' force direction using the supporting members 3a and 3b as nodes. When the square prism 1 is rotated around the x-x' axis, the prism 1 also vibrates in the y-y' force direction, and the vibration amplitude is proportional to the angular velocity applied around the x xl axis. It has been analyzed based on Newton's laws of motion and Coriolis force, and is well known. Therefore, the piezoelectric element 2c provided on the side surface of the prism 1 that is perpendicular to the side surface on which the piezoelectric elements 2a and 2b are provided,
2d outputs a voltage proportional to the amplitude of the prism 1 in the y-y' direction, so the angular velocity can be determined from this voltage value.

However, in such conventional sensors, the area of each surface in the longitudinal direction of the prism 1 is approximately the same, so the shooting modes are similar, even when the angular velocity around the x-x' axis is not given. , z-z' force direction vibration causes slight vibration due to y-y' force direction resonance, so an offset occurs. In order to reduce this offset, it is possible to change the area ratio of the horizontal plane and the vertical plane among the longitudinal planes, but if you do this, the area of one plane will become smaller and the piezoelectric element will also become smaller, so the output voltage However, this method has the drawback that the accuracy becomes poor due to the small size of the image.

Therefore, an object of the present invention is to provide an angular velocity sensor that does not generate offset and has high detection accuracy.1 To achieve such an object, the present invention has two tuning forks whose vibration surfaces are perpendicular to each other. By attaching the sensors to the same surface of a rigid body and completely changing the vibration modes of both sensors, the tuning forks are prevented from resonating with each other when no angular velocity is applied. Hereinafter, the present invention will be described in detail using drawings showing embodiments.

FIGS. 2 to 5 are diagrams showing an embodiment of the present invention,
Figure 2 is a front view, Figure 3 is a plan view, Figure 4 is a side view of the sensor viewed from the left, and Figure 5 is a side view of the sensor viewed from the right, which is the same as Figure 1. The same symbols are used for parts.

4a and 4b are first and second support members,
It is attached to the same longitudinal surface of a prismatic column 1 as a rigid body.

Support points for tuning forks 5a and 5b are attached to the support portions 4a and 4b. In this case, the positions of the support members 4a and 4b are determined so that the vibration surfaces of the tuning fork 5a and the tuning fork 5b are perpendicular to each other.

The piezoelectric elements 2a and 2b vibrate together with the first tuning fork 5a, and the piezoelectric elements 2c and 2d vibrate together with the second tuning fork 5b.
It is designed to vibrate as one.

The supporting points of each tuning fork are arranged at equal distances from the prism 1, and the supporting points are arranged on the same line as shown by the dashed line in FIG.

In the sensor according to the present invention configured in this way,
When a power source having a constant frequency close to the resonance frequency of the tuning fork 5a is connected to the piezoelectric elements 2a and 2b, the tuning fork 5a starts to vibrate. Here, when the prism 1 is rotated around its long axis,
The tuning fork 5b begins to vibrate, and the vibration amplitude is proportional to the angular velocity given to the prism 1.

Strictly speaking, this analysis should be performed based on Newton's equation of motion and Coriolis force, as in the case of Figure 1, but qualitatively it can be considered as follows.

In FIG. 2, the tuning fork 5a vibrates in the vertical direction of the paper, but since the support point of the tuning fork 5a is fixed to the prism 1 by the support member 4a, the prism 1 does not vibrate. This phenomenon can be explained by considering that forces in opposite directions act on the support part 4a of the prism 1 above and below υ, and this force is balanced, and that this force acts uniformly on the prism 1. Also good. Here, when an angular velocity is applied to the circumference of the long axis of the prism 1, the force acting on the prism 1 and the Coriolis force cause the tuning fork 5b to vibrate in the front and back directions of the paper.

Since the vibration surfaces of the tuning forks 5a and 5b are mounted at right angles to each other, the vibration modes are completely different, and since resonance does not occur, the vibration of the tuning fork 5a when no angular velocity around the long axis is applied. The tuning fork 5b does not vibrate and no offset occurs. When an angular velocity around the long axis is given, the tuning fork 5b resonates with an amplitude proportional to the angular velocity as described above, and a voltage proportional to the angular velocity is generated from the piezoelectric elements 2c and 2d. Therefore, the value of the angular velocity can be determined from the value of this voltage.

As explained above, the angular velocity sensor according to the present invention is configured such that two tuning forks are attached to the same side of a rigid body and their respective vibration surfaces are perpendicular to each other, so that the angular velocity can be counted without causing an offset. Therefore, it has an excellent effect of being able to detect angular velocity with high precision.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of a conventionally used angular velocity sensor, FIGS. 2 to 5 show an embodiment of the present invention, FIG. 2 is a front view, and FIG. 3 is a plan view. FIG. 4 is a side view of this sensor as seen from the left, and FIG. 5 is a side view of the sensor as seen from the right. 1...Prismatic column, 28-2d...Piezoelectric element, 4a
, 4b... support member, 5a, 5b... tuning fork. Patent applicant: G-Eco Co., Ltd. Agent: Masaki Yamakawa (and one other person)

Claims (1)

[Claims] a rigid body; first and second support portion sides attached in the longitudinal direction on the same side of the rigid body; first and second tuning forks having support points fixed to the support members; and a piezoelectric element attached to each vibrating surface of the second tuning fork, and the first tuning fork and the second tuning fork are attached such that their vibrating surfaces are at right angles to each other. sensor.