JPH04203927A - Angular velocity sensor - Google Patents

Abstract

PURPOSE:To improve the shock impact resistance of an angular velocity sensor by constituting the sensor of a tuning fork vibrating element, a supporting rod for supporting and bonding the element to a base member, a vibration absorbing material covering the periphery of the rod, and a supporting body for supporting and reinforcing the supporting rod via the absorbing material. CONSTITUTION:A driving piezoelectric element 2 starts symmetic vibrations centering an electrode block 3 when signals are impressed thereto. That is, a so-called tuning fork vibration is started. A proper oscillation while a tuning fork vibrating element is attached to an end of a supporting rod 4 is about 400Hz, which is approximately at the center of a driving frequency of the tuning fork vibrating element. A vibration absorbing material 7 is made of silicone gel. Silicone in a jel state is injected between a supporting body 8 and the supporting rod 4 and then heated to be turned to gel. Even when the absorbing material 7 and the supporting body 8 are attached around the supporting body 4, the proper oscillation of the supporting rod 4 is about 440Hz and at the center of the driving frequency of the tuning fork vibrating element. Therefore, the secondary and the tertiary higher harmonics do not have the frequency in the vicinity of the driving frequency. An angular velocity sensor which is resistive to the external acceleration is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a gyroscope, and particularly to an angular velocity sensor using vibration of a piezoelectric element.

BACKGROUND ART Conventionally, a mechanical rotary gyro has been mainly used as an inertial navigation device using a gyroscope to determine the direction of a moving object such as an airplane or a ship.

Although this method can provide stable orientation, since it is mechanical, the device is large-scale and costly, and it is difficult to apply it to equipment that requires miniaturization.

On the other hand, there is a vibration-type angular velocity sensor that vibrates an object without using rotational force and detects the "Coriolis force" from a vibrating sensing element. Many of these structures employ piezoelectric and electromagnetic mechanisms. In these cases, the mass that makes up the gyro does not move at a constant speed, but instead vibrates. Therefore, when an angular velocity is applied, the Coriolis force occurs as a vibration torque with a frequency equal to the frequency of the mass. The principle of a vibration-type angular velocity sensor is to measure angular velocity by detecting vibrations caused by this torque, and in particular, many sensors using piezoelectric materials have been devised (
Journal of the Japan Society of Aeronautics and Astronautics Vol. 23 No. 257 339-350
page).

Problems to be Solved by the Invention With a structure based on the above principle, patent application No. 18582/1982
Although the angular velocity sensor shown in No. 5 was invented, it had the following problems.

When disturbance acceleration caused by vibration of the motor of a device equipped with an angular velocity sensor acts on the angular velocity sensor, unless the angular velocity sensor is completely insensitive to translational acceleration, the angular velocity sensor will generate an error output in response to the disturbance acceleration. do.

This is because the sensing piezoelectric element is basically an acceleration sensor and is not selectively sensitive only to the "Coriolis force".

According to the principle of the vibration type angular velocity sensor described above, a vibration torque corresponding to the angular velocity is generated from the detection piezoelectric element.
A corresponding AC signal is output. This AC signal is synchronously detected and converted into a DC signal. Therefore, the frequency component of the acceleration response differs from the disturbance acceleration by the frequency of the synchronous detection signal, that is, the drive frequency. Therefore, of the disturbance acceleration, it is the frequency component near the driving frequency that particularly affects the acceleration response.

Conventionally, in order to reduce acceleration response, it has been possible to match the sensitivities of a pair of detection piezoelectric elements to create a canceling effect, to hold the sensor through a vibration isolating material, or to reduce the natural frequency of the support. By setting an appropriate value, for example, a value approximately in the middle between 1/2 and 1/3 of the driving frequency of the tuning fork vibrating element, transmission of disturbance acceleration to the sense element has been suppressed. However, the reduction in acceleration response was not sufficient.

In addition, the acceleration response in the thickness direction of the detection piezoelectric element is more sensitive than the acceleration response in the thickness direction and detection axis direction of the drive piezoelectric element. It was necessary to define the direction.

The present invention has been made in view of this point, and an object of the present invention is to obtain an angular velocity sensor that is resistant to disturbance acceleration.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention covers the support rod that supports and connects the tuning fork vibrating element to the base member with a vibration absorbing material, and covers this vibration absorbing material with the support. The structure is such that the support rod is supported and reinforced through the support rod.

Effect: With the above configuration, when the support rod vibrates due to disturbance acceleration, the vibration absorbing material has its outer periphery fixed to the support, so
The support rod compresses and expands the vibration absorbing material, the vibration energy is converted into thermal energy, and the vibration is quickly attenuated, making it possible to obtain an angular velocity sensor that is resistant to disturbance acceleration.

Embodiment FIG. 1 is a structural diagram showing an embodiment of an angular velocity sensor according to the present invention. In FIG. 1, 1 is a detection piezoelectric element, 2
3 is a driving piezoelectric element, 3 is an electrode block, and 6 is a joining member. The sensing piezoelectric element 1 and the driving piezoelectric element 2 are joined to each other through the joining member 6 so as to be substantially perpendicular to each other to form a sensor element. , and the pair of sensor elements are coupled by an electrode block 3 serving as a coupling member to constitute a tuning fork vibrating element. 4 is a support rod, 5 is a base, 7 is a vibration absorber,
Reference numeral 8 denotes a support body, and the tuning fork vibrating element is supported by the base 5 via the support rod 4. It is supported by a support body 8 via.

The operation of the angular velocity sensor of this embodiment configured as described above will be explained below.

First, in order to drive a pair of driving piezoelectric elements 2, an alternating current signal is applied between the opposing surfaces of the driving piezoelectric elements 2 and the outer surfaces thereof, using the opposing surfaces as common electrodes. The drive piezoelectric element 2 to which the signal is applied begins to vibrate symmetrically around the electrode block 3, which is what is called a tuning fork vibration. Since the detection of angular velocity is the same as that described in the prior art section, the description thereof will be omitted.

The support rod 4 is made of an alloy of iron, cobalt, and nickel, and has a length of 4.5 m111. The thickness is 0.6n+m and the natural frequency with a tuning fork vibrating element attached to the tip is approximately 4.
00 ) 1z, and the driving frequency of the tuning fork vibrating element is approximately 1k.
The value is approximately in the middle between 1/2 and 1/3 of Hz. The support 8 is a metal tube with an outer diameter of 2 mm, an inner diameter of 1 mm, and a length of 4 mm.

The vibration absorbing material 7 is a silicone gel, which is injected in a gel state between the support body 8 and the support rod 4, and heated to gel. Vibration absorbing material 7 around the support rod 4. Even with the support 8 attached, the natural frequency of the support rod 4 is approximately 440 ) 1
z, which is 1/2 and 1/3 of the driving frequency of the tuning fork vibrating element.
Since the value is approximately at the center of , its second and third harmonic components do not have frequencies near the drive frequency.

FIG. 2 is a diagram comparing the acceleration response to the excitation intensity when the support rod of a conventional angular velocity sensor and an angular velocity sensor according to an embodiment of the present invention are excited at a frequency near the resonance frequency. The conventional sensor has 0.7G as shown by the wavy line.
However, in the sensor according to the embodiment of the present invention, as shown by the solid line, the acceleration response is within the elastic limit up to at least 3G, and the acceleration response maintains linearity. Moreover, the level is also about 1/2 that of conventional sensors, indicating that the resistance to disturbance acceleration is improved.

In addition, in terms of drop impact resistance, conventional angular velocity sensors are
Although deterioration in resonance characteristics was observed at 00G, no deterioration in resonance characteristics was observed in the angular velocity sensor according to the example of the present invention even at 100OG.

In conventional angular velocity sensors, the support rod bends due to the impact of falling, causing the tip of the tuning fork vibrating element to displace significantly and contacting the case housing the tuning fork vibrating element, and the impact concentrates on the root of the driving piezoelectric element. This is because the driving piezoelectric element will be destroyed. In the embodiment of the present invention, the drop impact resistance is improved because the maximum amount of deflection of the support rod is regulated by the support, so the amplitude of the tuning fork vibrating element is reduced.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, when the support rod vibrates due to disturbance acceleration, since the outer periphery of the vibration absorbing material is fixed to the support body, the support rod compresses and expands the vibration absorbing material.
Vibration energy is converted into thermal energy and the vibration is quickly attenuated, so an angular velocity sensor that is resistant to disturbance acceleration can be obtained. Furthermore, since the maximum amount of deflection of the support rod is regulated, it is possible to obtain an angular velocity sensor with excellent drop impact resistance.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the structure of an angular velocity sensor according to an embodiment of the present invention, and FIG. 2 is a characteristic diagram of acceleration response to excitation intensity in the conventional sensor and the sensor of the present invention. 1... Piezoelectric element for detection, 2... Old piezoelectric element for drive, 3... Electrode block, 4... Support rod, 5... Base , 6... Joining member, 7... Old vibration absorbing material, 8... Support body. Name of agent: Agent Haruaki Ogata and two others Figure 1

Claims (1)

[Claims] A pair of sensor elements in which a drive piezoelectric element and a detection piezoelectric element are joined to each other so as to be substantially perpendicular to each other via a joining member, and a tuning fork vibrating element in which a pair of sensor elements are joined at an end of the driving piezoelectric element through a joining member. , an angular velocity sensor consisting of a support rod that supports and connects this tuning fork vibrating element to a base member, a vibration absorber that covers the periphery of this support rod, and a support that supports and reinforces the support rod via this vibration absorber. .