JPH04299214A - angular velocity sensor - Google Patents

Abstract

PURPOSE:To obtain an angular velocity sensor wherein a drift occurs little, in respect to a problem that a drift voltage of an offset voltage fluctuates and deteriorates a drift characteristic in the angular velocity sensor used for a gyroscope or the like. CONSTITUTION:Piezoelectric elements 6 and 7 are joined on the outside surfaces of a U-shaped tuning fork part 5 which are opposite to each other, and a pair of right and left vibration detecting plates 2 and 4 to which piezoelectric elements 1 and 3 are joined perpendicularly to the direction of vibration of a turning fork are joined perpendicularly to the opposite fore end parts of this U-shaped tuning fork part 5 through the intermediary of joining members 8 and 9 having conductivity, so that an integrated structure be made. Thereby an angular velocity sensor enabling elimination of unnecessary vibration and being capable of displaying a stable performance can be obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular velocity sensor used in gyroscopes and the like.

0002

2. Description of the Related Art In recent years, with the development of computer technology, products with many functions have been commercialized, and as a result, demands for various sensors have increased. Applications of angular velocity sensors include navigation systems in electrical equipment, direction finding for robots, and stabilizer devices for drive devices, all of which are small and high-performance.
It will become necessary from now on.

Conventionally, an inertial navigation system using a gyroscope has been mainly used to determine the direction of a moving object such as an airplane or a ship. Although this method allows stable orientation to be determined, since it is mechanical, the device is large-scale and expensive, making it difficult to apply it to consumer equipment where miniaturization is desired.

On the other hand, a vibrating gyroscope (Japanese Patent Application No. 59-55420) has been proposed that detects angular velocity information from the Coriolis force generated when an angular velocity is generated by vibrating an object without using rotational force. This vibration gyroscope can be considered as a vibration sensor having a tuning fork structure. According to this, a drive piezoelectric bimorph (for excitation) and a detection piezoelectric bimorph are linearly and orthogonally joined, and the speed (cm
/S) was used to detect the Coriolis force acting on a piezoelectric bimorph for detection.

The conventional angular velocity sensor configured as described above will be explained below with reference to the drawings.

FIG. 7 shows a block diagram including a conventional angular velocity sensor and a drive circuit. The main part of the angular velocity sensor is formed by the driving piezoelectric bimorph elements 103, 104 and the detection piezoelectric bimorph elements 101, 102 orthogonally joined via the joining members 105, 106, and this pair is connected to the driving piezoelectric bimorph elements 103, 104, 1
The vibrator is connected at one end of 04 with a support 107.

[0007] This vibrator is connected to a base 109 via one metal elastic member 108, and the driving piezoelectric bimorph elements 103 and 104 are vibrated to cause a tuning fork to vibrate.
The configuration was such that an angular velocity output was obtained when an angular velocity was applied to the detection piezoelectric bimorph elements 101 and 102.

By applying a signal from the driving circuit 110 to the driving piezoelectric bimorph element 103 of the angular velocity sensor configured as described above, the driving piezoelectric bimorph element 104 is
resonates, and the drive circuit 110, AGC circuit 111, drive monitor 113, and drive piezoelectric bimorph elements 104, 10
The tuning fork starts to vibrate in the feedback loop formed by 3, and the amplitude signal obtained from the drive piezoelectric bimorph element 104 is fed back to the drive circuit 110 through the automatic gain adjustment circuit (AGC circuit) 111, and the tuning fork starts to vibrate. The amplitude of is kept constant.

Further, the phase signal obtained from the drive piezoelectric bimorph element 103 is used to obtain the angular velocity signal component from the detection piezoelectric bimorph elements 101 and 102, and the phase of the detection signal generated from the drive monitor 113 to the drive piezoelectric bimorph 104. It was configured to take out part of the signal information and detect a DC detection signal corresponding to the angular velocity using a detection circuit 115 and a filter circuit 116.

0010

However, in the conventional angular velocity sensor described above, the piezoelectric bimorph elements 101 to 10
4 is also a structure, so when a mechanical external force is applied as an elastic body, the piezoelectric bimorph elements 101 to 10
4 is easily subjected to extremely large stress, resulting in residual stress, permanent strain, or microcracks, and these mechanical stresses cause fluctuations in the offset voltage of the angular velocity detection signal.

That is, these distortions occur as unnecessary signal components when the tuning fork is vibrated, and these are output as part of the change in offset voltage. Therefore, the conventional angular velocity sensor configured using piezoelectric bimorph elements 101 to 104 as a structure has a problem in that external stress greatly affects drift characteristics, which is one of the major performance indexes. .

[0012] The present invention solves the above-mentioned conventional problems, and reduces the occurrence of drift in response to external mechanical stress.
The object of the present invention is to provide an angular velocity sensor that can exhibit stable performance.

[0013]

[Means for Solving the Problems] In order to solve the above problems, an angular velocity sensor according to the present invention includes a drive section in which piezoelectric elements each having electrodes formed on both surfaces are joined to opposing outer surfaces of a U-shaped tuning fork; A detection section in which a pair of vibration detection plates each having a piezoelectric element bonded thereto, which is orthogonal to the tuning fork vibration direction and has electrodes formed on both sides, are bonded to both tips of the U-shaped tuning fork via a conductive bonding member. The driving part of the U-shaped tuning fork is electrically connected to the vibration detection plate, and a lead terminal is connected to the center of the U-shaped tuning fork, and the other end of the lead terminal is connected to the base. The structure is such that it is supported by

[0014]

[Function] With this configuration, since the piezoelectric element is no longer the main structural member, the elastic properties of the piezoelectric element do not directly affect the tuning fork vibration, and extremely stable vibration without unnecessary vibration can be achieved. You will be able to do this.

[0015] Furthermore, by configuring the vibration detection plate and the drive unit of the U-shaped tuning fork to be connected via a conductive bonding member, the vibration detection plate and the drive unit of the U-shaped tuning fork are electrically connected to each other. Conductivity can be established and the lead wire can be taken out in common.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An angular velocity sensor according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing the configuration of an angular velocity sensor according to the present invention, which is formed into a U-shape using a constant elastic conductor, and piezoelectric elements 6 and 7 are attached to opposing inner or outer surfaces using an epoxy adhesive. Joining members 8 and 9 made of a constant elastic conductor and having concave portions perpendicular to each other at both ends are joined to both ends of the U-shaped tuning fork portion 5 using a conductive adhesive or solder. Furthermore, the piezoelectric elements 1 and 3 are bonded to each other, and vibration detection plates 2 and 4 made of a constant elastic conductor (material: Elinvar) are attached to the other ends of the bonding members 8 and 9 to detect the vibration of the U-shaped tuning fork portion 5. They are arranged perpendicular to the direction and joined using conductive adhesive or soldering to form the main part.

The U-shaped tuning fork section 5 is shown in FIGS. It has a structure in which a hole is provided in the center for the lead terminal 20 to pass through.

The piezoelectric elements 1, 3, 6, and 7 are shown in FIG.
As shown in Pb(Mg1/3Nb2/3)O3,Pb
It uses a piezoelectric ceramic mainly composed of three components, TiO3 and PbZrO3, and has silver electrodes 31 baked on both sides of the piezoelectric ceramic 30 (dimensions 1.6 x 6 x 0.2).
The configuration includes the following.

Next, lead terminals 14, 15, 16, 1
7 is for electrically connecting the piezoelectric elements 6, 1, 3, and 7, respectively, and is made of insulating glass 21, 22,
A support base 28 mainly made of Fe is provided through 23 and 24.
The support base 28 is insulated from the support base 28 and is attached so as to pass through the support base 28. In addition, lead terminals 14, 15, 16, 1
Reference numeral 7 has a structure that also serves as a lead terminal for electrical connection with the outside.

Further, the lead terminal 20 is for supporting the U-shaped tuning fork portion 5 at one point and for electrically connecting it.
Lead terminal 2 is inserted into the hole provided in the center of the U-shaped tuning fork section 5.
0 is passed through and joined by soldering to obtain electrical continuity, and the other end is joined via an insulating glass 27.

Note that the lead terminals 18 and 19 are unused terminals. The above piezoelectric elements 6, 1, 3, 7 and lead terminal 1
4, 15, 16, and 17, the insulated lead wires 10 and 11 are bonded to the side surface of the U-shaped tuning fork portion 5 using epoxy adhesive, and each end is connected to the piezoelectric elements 1 and 3 and the lead terminal 1.
5 and 16, respectively, and connect the wires by soldering. Further, the lead terminal 1 is connected to the piezoelectric element 6 provided in the U-shaped tuning fork portion 5.
4, from the piezoelectric element 7 to the lead terminal 17, respectively.
Similarly, the wires are connected by soldering using the insulated lead wires 12 and 13.

The angular velocity sensor created in this way is F
The container is housed in a bottomed cylindrical can case 29 mainly made of cans, and the contact portion between the support base 28 and the opening periphery of the can case 29 is hermetically sealed and joined by spot electric welding. This hermetic sealing is achieved by filling the inside of the can case 29 with airtight filling gas.

The characteristics of the angular velocity sensor of this embodiment constructed in this manner will be explained below.

In order to compare the characteristics of the angular velocity sensor according to this embodiment, the characteristics will be compared with those of a conventional piezoelectric bimorph type angular velocity sensor. The contents of this document sample (
Table 1) shows the results.

[0026]

[Table 1]

In order to check the characteristics of the material samples shown in Table 1, the operating circuit shown in FIG. 4 was used. Figure 4
is basically equivalent to the operating circuit shown in FIG. 6 used to check the characteristics of the conventional example. In addition, the characteristic check is shown in Figure 4.
The change in the drift voltage over time of the angular velocity sensor was investigated by replacing the inner sensor part with the two types of material samples (material numbers A and B) shown in Table 1 above. A comparison was made by showing the amount of change in drift over time of the angular velocity sensor of this example (material number B) when the amount was set as 0 dB as a reference.

FIG. 5 shows the temporal drift characteristics at this time. In FIG. 5, the X-axis shows the elapsed time from the time of operation, and the Y-axis shows the amount of change in drift over time.The angular velocity sensor according to this embodiment has a drift value over time of about -20 dB compared to the conventional product.
It is clear from Table 1 and FIG.

Furthermore, the angular velocity sensor according to the present invention has piezoelectric elements 1,
3 is joined to the vibration detection plates 2, 4, and is electrically connected to the U-shaped tuning fork portion 5 via the conductive constant elasticity joining members 8, 9, so that the vibration detection plates 2, 4 In the conventional method, two lead wires are required to be taken out from the piezoelectric elements 1 and 3, but only one lead wire is taken out from each side of the piezoelectric elements 1 and 3. Therefore, the lead wires taken out from the pair of detection parts are two in total, one each from piezoelectric elements 1 and 3, and one each from piezoelectric elements 6 and 7 of U-shaped tuning fork part 5. , a total of four connections can be made.

The piezoelectric elements 6 and 7 may be bonded to the opposing inner surfaces of the U-shaped tuning fork portion 5. Further, the shape of the U-shaped tuning fork portion 5 may have a structure as shown in FIGS. 6(a) and 6(b).

[0031]

[Effects of the Invention] The angular velocity sensor according to the present invention has a vibration detecting plate orthogonally joined to the vibration tip of a U-shaped tuning fork at right angles to the vibration direction via a joining member. , mainly uses vibration detection plates and U, not piezoelectric elements.
Since this configuration largely depends on the configuration with the letter-shaped tuning fork, it is possible to obtain the effect of greatly reducing (about -20 dB) fluctuations in the temporal drift voltage of the offset voltage caused by the piezoelectric element.

Furthermore, by supporting the center part of the U-shaped tuning fork part at one point, the unbalance of the vibration amplitude is eliminated, and more stable vibrations without unnecessary vibrations can be obtained, and the offset caused by unnecessary vibrations of the tuning fork vibrations is eliminated. Voltage drift fluctuations can be further reduced.

Furthermore, by configuring the joining member with a conductive member, the number of lead wires taken out from the piezoelectric element on the detection side can be reduced by two, making wiring connection easier and making it suitable for use as a tuning fork vibrator. Unnecessary parts are reduced, it becomes more like a rigid body, vibrations without unnecessary vibration components can be obtained, and as a result, lower drift can be obtained.

[0034] Furthermore, by integrating the vibration detection plate and the U-shaped tuning fork portion via a joining member, the orthogonality between the vibration direction of the U-shaped tuning fork and the vibration detection plate can be assembled with higher precision. This prevents signal components in the vibration direction from leaking to the vibration detection side. Furthermore, it is easy to change the material, shape, size, etc. of the vibration detection side, and it is possible to obtain many effects such as a degree of freedom in sensor design.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the configuration of an angular velocity sensor according to an embodiment of the present invention.

[Fig. 2] A perspective view showing the configuration of a piezoelectric element used in the same example.

[Fig. 3] (a) A front view showing the configuration of the U-shaped tuning fork used in the same example. (b) A side view of the same.

[Fig. 4] Block diagram showing the configuration of the drive circuit used in the same example.

[Figure 5] Characteristic diagram showing the drift change between the elapsed time during operation and the offset voltage of the angular velocity sensor

[Fig. 6] (a), (b) Perspective views showing other embodiments of the U-shaped tuning fork portion according to this embodiment.

[Fig. 7] Block diagram showing the configuration of a conventional angular velocity sensor drive circuit

[Explanation of symbols]

1, 2 Piezoelectric element 3,4 Vibration detection plate 5　U-shaped tuning fork part 6,7 Piezoelectric element 8, 9 Conductive bonding member 10-13 Insulated lead wire 14-20 Lead terminal 21-27 Insulated glass 28 Support base 29 Can case

Claims (2)

[Claims] Claim 1: A drive unit having piezoelectric elements with double-sided electrodes bonded to opposing outer surfaces of the U-shaped tuning fork, and a pair of vibration detection plates having piezoelectric elements with double-sided electrodes bonded to both sides of the U-shaped tuning fork. An angular velocity sensor consisting of a detection part joined to the tip part through a conductive joining member so as to be perpendicular to the vibration direction of the tuning fork, and the vibration part of the U-shaped tuning fork and the vibration detection plate are electrically connected. . 2. The angular velocity sensor according to claim 1, wherein a lead terminal is connected to the center of the U-shaped tuning fork, and the other end of the lead terminal is connected to a base to support the U-shaped tuning fork.