JPH07139951A - Angular velocity sensor - Google Patents

Abstract

PURPOSE:To provide an angular velocity sensor, which can securely support a vibrating body even if the balance of the vibrating body is collapsed and can perform vibration efficiently with less leakage of vibration. CONSTITUTION:In a square tuning-fork-type piezoelectric vibration gyroscope, two square forks 3 and 4 are supported with a square shaped supporting part 2 with respect to a base stage part 1. The cross sections of the base stage part 2, the supporting part 2 and the square forks 3 and 4 have the square shape, respectively. Driving piezoelectric elements 5 and 6, feedback piezoelectric elements 9 and 10 and detecting piezoelectric elements 7 and 8 are fixed to the orthogonally intersecting surfaces of the square forks 3 and 4. The width of the supporting part 2 is set at 5mm or less.

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 for measuring an angular velocity using a piezoelectric vibration type gyro, which sensor is used for measuring a motion state of a moving body such as a vehicle, a ship, an airplane or a robot. For example, it is used to measure the vehicle turning angular velocity for controlling the attitude of the vehicle.

[0002]

2. Description of the Related Art Conventionally, there is an angular velocity sensor using a prismatic tuning fork type piezoelectric vibrating gyro. As shown in FIG. 23, two prisms 33 are supported by a supporting portion 32 with respect to a base portion 31, and a driving piezoelectric element 34 and a detecting piezoelectric element 35 are provided on the surfaces orthogonal to each prism 33. Are fastened respectively. At this time, as shown in FIG. 23, there is a structure having a pin structure for supporting the vibration node as shown in FIG. 23 or a structure having no support portion as shown in FIG.

[0003]

However, when a node is supported by a thin member such as a pin (32) having a circular cross section as shown in FIG. 23, the balance of the vibrating body is lost due to variations in manufacturing. When it is present, unnecessary vibration is generated in the support portion 32, and the vibrating body cannot be firmly supported.

Further, as shown in FIG. 24, if the vibrating body is fixed without providing the supporting portion, the leakage of the vibration is large and the vibrating cannot be performed efficiently. Further, it is considered that this vibration leak also affects the offset signal of the sensor output, and the vibration leak changes due to a change in temperature, thereby causing a temperature drift of the offset.

Therefore, an object of the present invention is to provide an angular velocity sensor capable of reliably supporting a vibrating body even when the balance of the vibrating body is lost and efficiently vibrating with less leakage of vibration.

[0006]

According to a first aspect of the present invention, two prisms are supported on a base portion by a prismatic support portion, and a driving piezoelectric element and a detection piezoelectric element are provided on a surface orthogonal to the prisms. In an angular velocity sensor using a prismatic tuning fork type piezoelectric vibrating gyro fixed to each of the elements, the vibration of the base portion due to the vibration of the prism by the driving piezoelectric element provided in the prism is 1.5% or less. It is a gist to provide an angular velocity sensor.

According to a second aspect of the present invention, two prisms are supported by a prismatic support portion with respect to a base portion, and a driving piezoelectric element and a detecting piezoelectric element are fixed to the orthogonal surfaces of the prisms. In an angular velocity sensor using the prismatic tuning fork type piezoelectric vibrating gyro, there is provided an angular velocity sensor in which the width of the supporting portion is 5 mm or less. A third aspect of the invention provides an angular velocity sensor in which the thickness of the support portion is substantially the same as the thickness of the prism.

Further, the fourth invention provides an angular velocity sensor in which the width of the supporting portion is within a range of 5 mm or less and 0.5 mm or more. According to a fifth aspect of the present invention, two prisms are supported by a prismatic support portion with respect to the base portion, and the driving piezoelectric element and the detecting piezoelectric element are fixed to the surfaces orthogonal to each other. In the angular velocity sensor using the prismatic tuning fork type piezoelectric vibrating gyro, the width of the supporting portion is A millimeter and the width of the prism is B millimeter,
When the length of the support part is C millimeter,

[0009]

## EQU00003 ## The gist is an angular velocity sensor that satisfies A.ltoreq.0.4.times.C + B. According to a sixth aspect of the present invention, two prisms are supported by a prismatic support portion with respect to the base portion, and the driving piezoelectric element and the detecting piezoelectric element are fixed to the orthogonal surfaces of the respective prisms. In the angular velocity sensor using the prismatic tuning fork type piezoelectric vibrating gyro, when the width of the support portion is A millimeter, the width of the prism is B millimeter, and the length of the support portion is C millimeter,

[0010]

The gist of the present invention is an angular velocity sensor satisfying the following condition: 0.4 × C + B-1 ≦ A ≦ 0.4 × C + B + 1. .

[0011]

When the width of the support member is 5 mm or less, and the size is set so as to satisfy the formula 3 or the formula 4, the vibrating body is stably supported. In other words, vibration energy can be effectively trapped inside the tuning fork even if the dimensions of the left and right vibrators are different due to processing dimension errors in the manufacturing process of the gyro.

Therefore, unnecessary vibration leakage can be reduced, and noise generation due to this can be suppressed. Moreover, as a result of reducing unnecessary vibration leakage, a stable vibration state is achieved,
It is stable against temperature changes and has good temperature characteristics.

[0013]

As described above in detail, according to the present invention,
Even if the balance of the vibrating body is unbalanced, the vibrating body can be reliably supported, and the excellent effect that vibration of the vibrating body is small and the vibrating body can be efficiently vibrated.

[0014]

【Example】

(First Embodiment) An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an angular velocity sensor using the prismatic tuning fork type piezoelectric vibrating gyro of this embodiment. Two prisms 3 and 4 are supported by a support 2 having a prismatic shape with respect to the base 1.

The base portion 1, the support portion 2, and the prisms 3 and 4 are formed in a square cross section, and have substantially the same thickness. The driving piezoelectric element 5 is attached to the lower portion of the right side surface of the prism 3 and the driving piezoelectric element 6 is attached to the lower portion of the right side surface of the prism 4. When an AC voltage is applied to the driving piezoelectric elements 5 and 6, the prism 3 and
4 is oscillated in the left-right direction in FIG.

Further, the detection piezoelectric element 7 is attached to the upper front portion of the prism 3, and the detection piezoelectric element 8 is also attached to the upper front portion of the prism 4. When the rotational angular velocity is applied to the central axes of the prisms 3 and 4 (vibrator), the detection piezoelectric elements 7 and 8 are accompanied by the vibration of the prisms 3 and 4 due to the application of the AC voltage to the driving piezoelectric elements 5 and 6. At 1, the Coriolis force acting in the front-back direction is detected as a voltage.

The feedback piezoelectric elements 9 and 10 are attached to the upper portions of the driving elements 5 and 6. The feedback piezoelectric elements 9 and 10 monitor the vibration state,
Used for self-excited oscillation. As the operation of the sensor, when an alternating voltage is supplied to the driving piezoelectric elements 5 and 6,
The elements 5 and 6 expand and contract, and the prisms 3 and 4 flexurally vibrate in the driving vibration direction. In this state, prisms 3 and 4 (transducer)
When the rotational angular velocity is applied to the central axis of the, the detection vibration is generated by the Coriolis force, and the signal due to the bending vibration is generated in the detection piezoelectric elements 7 and 8. Then, the detection piezoelectric element 7,
The angular velocity is detected based on the signal of 8.

Here, the width A of the supporting portion 2 is 3 mm. The results of various experiments are shown below. The angular velocity sensor shown in FIG. 1 stabilizes vibration when there is a shape dimension error of the right and left prisms 3 and 4 and a mass error of the left and right piezoelectric elements (driving piezoelectric elements 5 and 6, detection piezoelectric elements 7 and 8). I can not bring out the full potential. This appears as the amplitude of the base 1.

In this embodiment, as shown in FIG. 2, the width of the left prism 3 is 3.0 mm and the width of the right prism 4 is 2.7 m.
m. That is, it was assumed that the width of the right prism 4 was 2.7 mm by shifting the regular prism width of 3.0 mm to the negative side by 10%. Then, various experiments were conducted with a predetermined point on the base 1 as the X point.

3 to 7 show the correlation between the amplitude of the base 1 and the width A of the support when the dimensions of each part of the prismatic tuning fork type piezoelectric vibrating gyro are changed. The dimensions of the angular velocity sensor during each experiment are also shown in the figure. Here, as shown in FIG. 1, the distance between the prisms (vibrator) 3 and 4 is W,
The width of the prisms 3 and 4 is B, the length is L, and the support portion length is C, and the length of the root portion of the prisms 3 and 4 is D.

FIG. 3 shows the correlation between the support portion width A and the vibration of the base portion 1 which is the amplitude at the point X of the base portion 1 in FIG. 2 when the support portion length C is changed. is there. As is clear from FIG. 3, the smaller the support portion width A, the smaller the amplitude difference. Therefore, it was found that the smaller the support portion width A, the more stable the vibration. FIG. 4 shows the correlation between the vibration at the point X of the base 1 and the support width A when the widths B of the prisms 3 and 4 are changed. FIG. 5 shows the correlation between the vibration at the point X of the base 1 and the support width A when the distance W between the prisms 3 and 4 is changed. FIG. 6 shows the correlation between the vibration at the point X of the base 1 and the support width A when the lengths L of the prisms 3 and 4 are changed. Further, FIG. 7 shows the correlation between the vibration at the point X of the base 1 and the support width A when the length D of the root portions of the prisms 3 and 4 is changed.

From these FIGS. 3 to 7, the distance W between the prisms 3 and 4, the length L of the prisms 3 and 4, and the length of the root portion of the prisms 3 and 4 with respect to the amplitude at the point X of the base 1. It was found that there was no influence by the thickness D, the width B of the prism, and the length C of the supporting portion. As described above, it was found that the smaller the support portion width A, the smaller the amplitude of the base portion 1 in any size. That is, it was found that the support portion width A is a dominant factor for the amplitude of the base portion, and the smaller the support portion width A, the smaller the amplitude of the base portion.

The correspondence between the temperature drift characteristic of the zero point and the support portion width A, which is an important characteristic of the gyro, is shown in FIG.
It became like. As is clear from FIG. 8, similar to the result of the vibration of the base 1, the smaller the width A of the support 2, the smaller the temperature drift and the better characteristics. It was also found that sufficient temperature drift characteristics were obtained when the width of the support portion was 5 mm or less. Then, comparing this result with the result of the vibration of the base 1, it means that the width A of the support portion is 5 mm or less, which means that the amplitude of the base 1 corresponds to 1.5% or less of the tip amplitude. is doing.

Therefore, it is considered that a sensor with good characteristics can be obtained by designing the shape of the supporting portion so that the base amplitude is 1.5% or less. As one of the means, in order to obtain a vibration gyro with good temperature drift characteristics, the width A of the support portion is
It can be easily understood from FIG. 3 to FIG. However, there are limitations from the actual sensor manufacturing process,
If the support 2 must be thicker, the shape of the support 2 may be designed so that the vibration of the base 1 due to vibration leakage is 1.5% or less.

In this way, the shape of the support portion 2 of the vibrating gyro is adjusted so that the vibration of the base portion 1 is 1.5% or less.
And specifically, by designing it to be 5 mm or less,
A gyro with high vibration stability can be obtained. As described above, in this embodiment, the vibration of the prisms 3 and 4 by the driving piezoelectric elements 5 and 6 provided on the prisms 3 and 4 causes the amplitude of the base portion 1 to be 1.5% or less of the amplitude of the prisms 3 and 4. When designed so that specifically, the width of the support portion 2 is set to 5 mm or less, so that the vibrating body is stably supported.

That is, even if the dimensions of the right and left prisms 3 and 4 (vibrator) are different due to a processing dimension error in the manufacturing process of the gyro, the vibration energy can be effectively trapped inside the tuning fork. Therefore, unnecessary vibration leakage can be reduced, and noise generation due to this can be suppressed. Moreover, as a result of reducing unnecessary vibration leakage, a stable vibration state is achieved,
It is stable against changes in temperature and has good temperature characteristics. In this way, even if the balance of the vibrating body is lost, the vibrating body can be reliably supported and the vibration can be efficiently vibrated with less leakage of vibration.

(Second Embodiment) Next, we conducted further diligent research. The same angular velocity sensor as shown in FIG. 2 was used. The results of various experiments are shown below. FIG. 9 shows a correlation between the amplitude difference at the tips of the left and right prisms (vibrators) 3 and 4 and the support portion width A. The amplitude difference is smallest when the support width A is 3.0 mm. Therefore, it was found that the vibration was stable when the support width A was 3.0 mm.

10 to 16 show prisms (vibrator) 3 and 4.
3 shows the correlation between the tip end amplitude difference between the right and left prisms (vibrators) 3 and 4 and the support portion width A when the width B and the support portion length C are changed. As a result, it was found that there is a dimensional relationship that minimizes the amplitude difference at the tips of the prisms (vibrator) 3, 4. Here, W, L, and D at the respective points indicate the same points as in the first embodiment.

FIG. 10 shows the difference between the amplitude and the width A of the supporting portion when the width B of the prisms 3 and 4 is changed (when the specified values are deviated by 10% from the specified values of 1.5 mm, 3 mm and 5 mm). Show correlation. 11 to 13 show the correlation between the amplitude difference and the width A of the supporting portion when the length C of the supporting portion 2 is changed. The changed dimensions are shown in each figure. 10 to 1
From 3, the width A of the supporting portion, the prism 3,
It was found that the width B of No. 4 and the length C of the supporting portion 2 were affected.

FIG. 14 shows the correlation between the amplitude difference and the support width A when the distance W between the prisms 3 and 4 is changed. or,
FIG. 15 shows the correlation between the amplitude difference and the support portion width A when the lengths L of the prisms 3 and 4 are changed. Further, FIG. 16 shows the correlation between the amplitude difference and the support portion width A when the length D of the root portions of the prisms 3 and 4 is changed. From FIGS. 14 to 15, there is no influence on the left-right amplitude difference due to the separation distance W of the prisms 3 and 4, the length L of the prisms 3 and 4, and the length D of the root portion of the prisms 3 and 4. found.

FIG. 17 shows a summary of the minimum values of the vibration difference under these conditions. The plot points of these minimum values could be summarized in the following conditional expression.

[0032]

## EQU00005 ## A.ltoreq.0.4.times.C + B where A is the width of the supporting portion 2 (millimeters) B is the width of the prisms 3 and 4 (millimeters) C is the length of the supporting portion 2 (millimeters)

[0033]

## EQU6 ## It is preferable that 0.4 × C + B-1 ≦ A ≦ 0.4 × C + B + 1. Here, in the above equation, (0.4
The width of ± 1 mm with respect to (× C + B) is provided so that the amplitude difference at the tips of the prisms (vibrators) 3 and 4 is 10% or less.

As described above, by designing the shape of the support portion of the vibration type gyro according to the above equation, a gyro having high vibration stability can be obtained. That is, even if the dimensions of the right and left prisms 3 and 4 (vibrator) are different due to processing dimension errors in the manufacturing process of the gyro, the vibration energy can be effectively trapped inside the tuning fork. Therefore, unnecessary vibration leakage can be reduced, and noise generation due to this can be suppressed. Further, as a result of reducing unnecessary vibration leakage, a stable vibration state is achieved, which is stable with respect to temperature changes and the temperature characteristics are improved. In this way, even if the balance of the vibrating body is lost, the vibrating body can be reliably supported and the vibration can be efficiently vibrated with less leakage of vibration.

Next, the relationship between the difference Δf between the resonance frequencies of the driving vibration and the detected vibration and the sensitivity will be described. The sensitivity increases as Δf decreases. For example, in the angular velocity sensor shown in FIG. 18, when the thickness of the prism is 3 mm and the length L of the prism is 35 mm, Δf and the sensitivity are examined. As a result, the relationship shown in FIG. 19 is obtained.

That is, the smaller Δf is, the higher the sensitivity can be. However, it has been found that there is a problem described below when Δf is reduced. (1) When the difference Δf in resonance frequency is small, the sensitivity is high, but a change in sensitivity or a change in offset is likely to occur due to a temperature change in the resonance frequency, and the temperature characteristic deteriorates. (2) Further, when the angular velocity is periodically applied, for example, when it is used for controlling the attitude of the vehicle, a response of about 0 to 40 Hz is practically required. However, as shown in FIG. 20, the response characteristics are the angular velocity frequency fo and the frequency difference Δf.
Has a peak at the points where are equal. As shown in FIG. 21, a gyro with a resonance frequency matched does not have a flat response. To give the gyro a flat response at frequencies up to 40 Hz, use the
As shown in 2, Δf needs to be 60 Hz or higher.

As described above, the resonance frequency difference Δf needs to be a certain value or more, and specifically, it is desirable to set it to 60 Hz or more. On the other hand, if Δf is too large, the sensitivity is lowered and therefore it cannot be made so large. Specifically, it is preferably 200 Hz or less. Therefore, in order to make a prismatic tuning fork type gyro with good characteristics, it is necessary to provide a certain difference between the resonance frequencies of drive and detection.
Approximately 200 Hz is desirable.

As described above, the resonance frequencies of the driving vibration and the detection vibration are not completely matched with each other, and a certain difference is provided, more specifically, 60 to 200 Hz. Where 60 to 20
0 Hz may be either plus or minus. as a result,
Since the resonance frequencies of drive and detection are close to each other to some extent, high sensitivity is achieved. Further, it is not necessary to make fine adjustments for matching the resonance frequencies, and the production can be performed at low cost. Furthermore, since the resonance frequency is less affected by the temperature change, it is possible to provide a gyro with good temperature characteristics.

[Brief description of drawings]

FIG. 1 is a perspective view showing an angular velocity sensor of an embodiment.

FIG. 2 is a front view of an angular velocity sensor.

FIG. 3 is a diagram showing a relationship between a support portion width and a base portion amplitude.

FIG. 4 is a diagram showing a relationship between a support portion width and a base portion amplitude.

FIG. 5 is a diagram showing a relationship between a support portion width and a base portion amplitude.

FIG. 6 is a diagram showing a relationship between a support portion width and a base portion amplitude.

FIG. 7 is a diagram showing a relationship between a support portion width and a base portion amplitude.

FIG. 8 is a diagram showing a relationship between a support portion width and a temperature drift.

FIG. 9 is a diagram showing a relationship between a support width and an amplitude difference.

FIG. 10 is a diagram showing a relationship between a width of a support portion and an amplitude difference.

FIG. 11 is a diagram showing a relationship between a support width and an amplitude difference.

FIG. 12 is a diagram showing a relationship between a support width and an amplitude difference.

FIG. 13 is a diagram showing a relationship between a width of a support portion and an amplitude difference.

FIG. 14 is a diagram showing a relationship between a support width and an amplitude difference.

FIG. 15 is a diagram showing a relationship between a width of a support portion and an amplitude difference.

FIG. 16 is a diagram showing a relationship between a support width and an amplitude difference.

FIG. 17 is a diagram showing a relationship between a support portion length and a support portion width.

FIG. 18 is a perspective view showing an angular velocity sensor.

FIG. 19 is a diagram showing a relationship between frequency difference Δf and sensitivity.

FIG. 20 is a diagram showing a relationship between an angular velocity frequency and a gain.

FIG. 21 is a diagram showing a relationship between frequency and responsiveness.

FIG. 22 is a diagram showing the relationship between frequency and responsiveness.

FIG. 23 is a perspective view showing a conventional angular velocity sensor.

FIG. 24 is a perspective view showing a conventional angular velocity sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base part 2 Support part 3 Prismatic prism 4 Prismatic prism 5 Piezoelectric element for driving 6 Piezoelectric element for driving 7 Piezoelectric element for detection 8 Piezoelectric element for detection

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomoyuki Kanda 1-1-1, Showa-cho, Kariya city, Aichi Nihon Denso Co., Ltd.

Claims (6)

[Claims] 1. A prismatic tuning fork type in which two prisms are supported by a prismatic support portion with respect to a base part, and a driving piezoelectric element and a detecting piezoelectric element are respectively fixed to the orthogonal surfaces of the prisms. In an angular velocity sensor using a piezoelectric vibrating gyro, the vibration of the base due to the vibration of the prism due to the driving piezoelectric element provided in the prism is 1.5% or less of the amplitude of the prism. Angular velocity sensor. 2. A prismatic tuning fork type in which two prisms are supported by a prismatic support part with respect to a base part, and a driving piezoelectric element and a detecting piezoelectric element are respectively fixed to the orthogonal surfaces of the prisms. An angular velocity sensor using a piezoelectric vibrating gyro, wherein the width of the support portion is 5 mm or less. 3. The angular velocity sensor according to claim 1, wherein a thickness of the supporting portion is substantially the same as a thickness of the prism. 4. The angular velocity sensor according to claim 1, wherein the width of the supporting portion is within a range of 5 mm or less and 0.5 mm or more. 5. A prismatic tuning fork in which two prisms are supported by a prismatic support part with respect to a base part, and a driving piezoelectric element and a detecting piezoelectric element are respectively fixed to the surfaces orthogonal to each other. In an angular velocity sensor using a piezoelectric piezoelectric gyro, when the width of the supporting portion is A millimeter, the width of the prism is B millimeter, and the length of the supporting portion is C millimeter, the following equation is obtained: A ≦ 0.4 × An angular velocity sensor characterized by satisfying C + B. 6. A prismatic tuning fork in which two prisms are supported by a prismatic support portion with respect to a base portion, and a driving piezoelectric element and a detecting piezoelectric element are fixed to the surfaces of the prisms orthogonal to each other. In an angular velocity sensor using a piezoelectric vibrating gyro, when the width of the supporting portion is A millimeter, the width of the prism is B millimeter, and the length of the supporting portion is C millimeter, the following equation is obtained: 0.4 × C + B- An angular velocity sensor characterized in that 1 ≦ A ≦ 0.4 × C + B + 1 is satisfied.