JP3596436B2 - Angular velocity sensor - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an angular velocity sensor having a vibrator for electrically detecting an angular velocity about a predetermined axis, and more particularly, to a characteristic of the sensor and an anti-vibration structure.
[0002]
[Prior art]
In a vibration type angular velocity sensor using a Coriolis force shown as a conventional angular velocity sensor, a velocity V is given by oscillating and driving at a natural resonance frequency f having a natural vibration mode of a vibrator. At this time, when the angular velocity Ω is input around a predetermined axis of the vibrator, a Coriolis force Fc is generated in a direction orthogonal to the velocity and each of the angular velocity input axes. The Coriolis force Fc is extracted by an electric signal, and is synchronously detected at the same frequency as the driving frequency f, and is output as an angular velocity signal.
[0003]
[Problems to be solved by the invention]
In such an angular velocity sensor, it is difficult to discriminate / separate a noise signal in a frequency band of an external vibration parasitic near the driving frequency f from a signal of the Coriolis force generated when the angular velocity Ω is actually input. The angular velocity detection accuracy is deteriorated.
[0004]
For this reason, as a countermeasure against external noise or the like, for example, as disclosed in Japanese Patent Application Laid-Open No. H11-6736, the shape of the vibration isolating member has been devised.
[0005]
However, sufficient noise countermeasures have not been found yet.
[0006]
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a configuration in which sufficient measures against noise have been taken in an angular velocity sensor.
[0007]
[Means for Solving the Problems]
As a countermeasure against these noises, the present inventors conducted research from a completely new point of view, focused on the vibration of the vibration isolating member itself, and the resonance of the vibration isolating member, particularly the base holding portion, greatly affected the vibration state of the vibrator. For the first time.
[0008]
That is, according to the first aspect of the present invention, a sensor unit having at least a vibrator for detecting an angular velocity about a predetermined axis and a base to which the vibrator is fixed, and a resonance unit provided on the sensor unit, And a vibration isolating member having a resonance frequency separated by 3% or more from the frequency.
[0009]
In this way, by providing a vibration isolating member having a resonance frequency that is at least 3% apart from the resonance frequency of the vibrator, the base that resonates due to the vibration of the vibrator can resonate with the vibration isolating member that holds the base. Therefore, resonance does not resonate more than necessary. Therefore, vibration of the base can be suppressed, and noise vibration to the vibrator fixed to the base can be suppressed.
[0010]
Here, if the distance is not more than 3% from the resonance frequency of the vibrator, a sufficient effect cannot be obtained.
[0011]
According to the fourth aspect of the present invention, a supporting portion for fixing the vibrator and the base is provided between the vibrator and the base. Thus, by providing the support portion, the vibrator can be easily separated from the base, and transmission of vibration of the vibrator to the base can be suppressed.
[0012]
According to the fifth aspect of the present invention, since the sensor portion is housed in the case, it is possible to further suppress the generation of noise due to external vibration.
[0013]
Still further, according to the invention of claim 6, a sensor unit having at least a vibrator for detecting an angular velocity about a predetermined axis and a base to which the vibrator is fixed, a case accommodating the sensor unit, and a sensor unit An angular velocity sensor comprising a spring portion that is separated from the case and elastically supports the vibration isolation member, and a holding portion that holds the sensor portion by inserting at least a part of the base through an insertion hole. Thus, the vibration isolating member provides an angular velocity sensor having a resonance frequency separated by 3% or more from the resonance frequency of the vibrator.
[0014]
As described above, since the spring portion and the holding portion are formed as the configuration of the vibration isolating member, it is possible to further suppress noise generation of the vibrator due to vibration.
[0015]
According to the ninth aspect of the present invention, the material forming the holding portion of the vibration isolating member is selected so that the resonance frequency of the holding portion of the vibration isolating member is separated from the resonance frequency of the vibrator by 3% or more. By doing so, the present invention can be easily achieved.
[0016]
Further, in the invention of claim 10, the thickness of the base-side mounting portion of the vibration isolating member is the same as that of the vibration isolating member so that the resonance frequency of the holding portion of the vibration isolating member is separated from the resonance frequency of the vibrator by 3% or more. If the thickness on the direction side is adjusted, the resonance frequency of the holding portion of the vibration isolating member can be accurately separated from the resonance frequency of the vibrator by 3% or more.
[0017]
In the invention according to claim 11, a sensor unit having at least a vibrator for detecting an angular velocity about a predetermined axis and a base to which the vibrator is fixed, a case for housing the sensor unit, and a sensor unit Between the vibration isolating member and the case so that the sensor portion is held in the case by applying a compressive stress to the vibration isolating member. And a frame member provided in the vibrator, wherein the vibration damping member has a resonance frequency that is at least 3% apart from a resonance frequency of the vibrator.
[0018]
By employing such a configuration, noise can be further reduced.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIG.
[0020]
In the present embodiment, for example, a sensor unit 20 having a case 10 for fixing a sensor to an object to be detected such as a vehicle, a vibrator 21 and a base 22 for fixing the vibrator 21, and the sensor unit 20 is housed in the case 10. And a vibration isolating member 50 for holding and attenuating external vibrations and shocks transmitted to the vibrator 21, a frame 60 for fixing the vibration isolating member 50 in the case 10, and generating a drive signal for the vibrator 21 to generate a Coriolis force. A circuit board 80 for processing a signal that has detected Fc, a flexible cable 70 (hereinafter, abbreviated as “flexible”) for connecting an electric signal to the circuit board 80 by connecting, for example, the hermetic terminal p of the base 22 to the circuit board 80, It is formed by a connector 90 having a power supply terminal and an angular velocity signal output terminal processed by the circuit board 80 and covering the circuit board from external noise. The vibration isolating member 50 includes a spring portion 52 for supporting the sensor portion 20 at a distance from the case for insulating the interference from the outside and a holding portion 51 for elastically holding the sensor portion. Is formed with an insertion hole 51a so that it can be fitted to the base side mounting portion.
[0021]
Next, the sensor unit 20 of the angular velocity sensor will be described with reference to FIGS. The sensor unit 20 includes, for example, a vibrator 21 having an electrode formed on the surface of a piezoelectric element, a metal plate-like base 22 disposed substantially parallel to the vibrator 21, and a vibrator 21 and the base 22. The structure includes a supporting portion 23 made of, for example, 42 alloy, which is connected and fixed, and a dome-shaped shell 27 made of metal and arranged to cover the vibrator 21. Further, the base 22 is provided with a base-side mounting portion 22a for mounting a vibration isolating member.
[0022]
The vibrator 21 constitutes a so-called tuning fork type vibrator having a tuning fork shape having a pair of arm portions 24 and 25 and a connecting portion 26 connecting one end of each arm portion 24 and 25. The vibrator 21 is joined to the support 23 by, for example, an epoxy-based adhesive. Further, the support portion 23 fixes the vibrator 21 to the base 22 by fixing it to the base 22 by, for example, welding. The vibrator 21 includes driving electrodes 30, 31, monitoring electrodes 32, 33, temporary GND electrodes 34, 35, 40 grounded to a reference potential, angular velocity detecting electrodes 41, 42, and angular velocity detecting electrodes 41, 42. , The extraction electrodes 45, 46 for extracting the output from the angular velocity detection electrodes 41, 42 to the pad electrodes 36, 37, the provisional GND electrode 40 on the back surface, and the provisional GND on the front surface. Temporary GND short-circuit electrodes 43 and 44 for short-circuiting the electrodes 34 and 35 are formed.
[0023]
Input and output of signals between the vibrator 21 and the outside such as a circuit board are performed by connecting the hermetic terminal p provided on the base 22 and each electrode on the vibrator 21 by wire bonding S, for example.
[0024]
At room temperature, the resonance frequency of the vibrator 21 was 3.2 kHz, and the resonance frequency of the vibration isolating member 50 was 2.5 kHz.
[0025]
Next, the operation of the vibrator 21 will be described with reference to FIG. First, by applying an inverted voltage to each drive electrode of the vibrator 21 from the circuit board 80, resonance occurs in the Y direction, a drive amplitude is generated, and a mass velocity V is generated. The driving frequency at this time oscillates at the resonance frequency of the target mode of the vibrator 21 in which the amplitude efficiency is high and the speed is maximum at the same voltage. Also, by monitoring and feeding back the outputs of the monitoring electrodes 32 and 33, self-excited oscillation control is performed so that the output becomes constant even when the drive amplitude state changes due to temperature or the like.
[0026]
When the angular velocity Ω is input while the mass velocity V is generated in the vibrator 21 in this manner, a Coriolis force Fc is generated in a direction orthogonal to the mass velocity V and the angular velocity input axis (Z). As a result, a deflection amplitude (detection amplitude) in the X direction is generated, and an output proportional to the deflection amplitude is generated from the angular velocity detection electrodes 41 and 42, thereby detecting the angular velocity Ω.
[0027]
The offset temperature drift (hereinafter, abbreviated as “temperature drift”), which is a sensor characteristic in the present case, refers to the output from the angular velocity detection electrodes 41 and 42 (ie, the offset) when the input angular velocity is not input (0 ° / s). ), And there is a problem that a remarkable projection-like variation occurs in a specific temperature range of the warm drill. As a cause of the generation of the hot dripper, the relationship between the shape of the vibration isolating member 50 and the hot drift is determined and determined as a result of a research and a result of the material and the shape used for the vibration isolating member 50, particularly, the base holder 51. The vibration generated from the resonance frequency greatly affects the increase of unnecessary vibration of the vibrator 21 which is one of the main factors of the warming, and the shape of the vibration isolating member 50 or the base holder 51 and the material to be used are optimized. By doing so, unnecessary vibration of the vibrator 21 can be minimized, and an improvement in hot dripping has become possible.
[0028]
Hereinafter, features of the present invention will be described in detail.
[0029]
First, FIG. 5 shows the results of evaluation of hot drilling when the conventional tuning fork vibrator 21 using a piezoelectric body and the vibration isolating member 50 are made of, for example, standard silicon rubber and have a hardness of about 60 ° Hs.
[0030]
In FIG. 5, the horizontal axis shows the relationship between the change in temperature and the vertical axis shows the relationship between the transducer output.
In the conventional structure, as shown in FIG. 5, at around −20 ° C., abnormal protrusions in the shape of a protrusion (hereinafter, abbreviated as a protrusion T) occur in the warm drill.
[0031]
Therefore, the inventors paid attention to the vibration state of the vibration isolating member 50 in the temperature range where the hot drill protrusions T occur (in the case of FIG. 5, around -20 ° C.). As a result, in this temperature range, it was confirmed that the resonance frequency of the vibration of the holding portion 51 of the vibration isolating member 50 substantially matched the resonance frequency of the vibrator 21.
[0032]
This is apparent from FIG. 6 showing the relationship between the resonance frequency of the vibrator 21 and the holding portion 51 of the vibration isolating member 50 and the temperature at which the hot drill protrusion T occurs.
[0033]
That is, it can be seen from FIG. 6 that the two resonance frequencies coincide in the temperature range (in this case, −20 ° C.) in which the warm drill protrusion T occurs in the conventional structure.
[0034]
As a method for measuring the resonance frequency of the vibration isolating member 50 in the present invention, the vibrator 21 is vibrated by applying an AC voltage to the vibrator 21 in a state where the vibration isolating member 50 is assembled. The vibration frequency of the vibrators 21 was sequentially changed, and the movement of the holding portion of the vibration isolating member 50 at the frequency of each vibrator 21 was confirmed with a laser displacement meter. Then, the frequency of the vibration isolating member 50 was obtained from the movement of the vibration isolating member 50.
[0035]
From the above findings, it has been found for the first time in the present invention that it is necessary to make the resonance frequency of the holding portion 51 of the vibration isolating member 50 different from the resonance frequency of the vibrator 21.
[0036]
As specific means, a relational expression shown in FIG. 7 can be used.
[0037]
That is, the resonance frequency Fh of the holding portion 51 of the vibration isolating member 50 is proportional to the product of the propagation constant (corresponding to (E / ρ) ^1/2 ) and the shape of the vibration isolating member (corresponding to D). Then, by selecting the optimum shape for each, the warm-driving protrusion T can be suppressed and the warm-driving characteristics can be improved. Here, E is the viscoelastic modulus, ρ is the density, and D is the shape of the holding part, and specifically, the thickness of the holding part.
[0038]
Hereinafter, optimization of the material used for the vibration isolation member 50 will be described.
[0039]
FIG. 8 shows the relationship between the propagation constant determined by the material property value which is a coefficient of the relational expression shown in FIG. 7 and the temperature at which the hot drill protrusion T occurs.
[0040]
As is clear from FIG. 8, the two are in a correlation, and it has been found that the temperature range in which the warm projections T occur can be changed by changing the propagation constant.
[0041]
For this reason, the anti-vibration member 50 has conventionally been designed with consideration given only to external vibration and impact. However, this time, the natural vibration of the anti-vibration member 50, particularly the holding portion 51 of the anti-vibration member 50 has been considered. It can be understood that the influence on the vibrator by the vibration is very high, and that it is necessary to take care to avoid interference with the vibrator 21 by using a material having a high attenuation rate.
[0042]
Next, the shape of the holding portion 51 of the vibration isolating member 50, which is a coefficient of the relational expression shown in FIG. 7, was examined.
[0043]
The shape of the holding portion 51 of the vibration isolating member 50 in the present embodiment indicates the size of the thickness D of the holding portion 51 in FIG.
[0044]
FIG. 10 is a characteristic diagram showing the relationship between the propagation constant and the protrusion generation temperature in the shape of each sex member.
[0045]
As a result, it was understood that the resonance frequency of the base 50 changed by changing the thickness D of the holding portion 51 of the vibration isolating member 50. That is, as shown in FIG. 9, the relationship between the thickness D and the temperature at which the warm-driving protrusion T is generated can be changed by changing the thickness D of the holding portion 51 of the vibration isolating member 50 so that the temperature range at which the warm-driving protrusion T is generated. Can be changed.
[0046]
By performing the above optimization, the resonance frequency of the base holder 51 of the vibration isolating member 50 in the sensor operating temperature range is made different from the resonance frequency of the vibrator 21, thereby suppressing the warming projection T. We were able to improve warm drips.
[0047]
By performing the above-described optimization with respect to the embodiment of FIG. 1, it is possible to improve the temperature drift. However, it is necessary to design in consideration of vibration resistance. For example, when it is necessary to use a soft rubber to improve the warming projection T, the vibration resistance is remarkably reduced due to the low spring property. In this regard, by compressing and assembling the spring part 52 of the vibration isolating member 50 in particular, the spring property can be increased, and the vibration resistance can be improved.
[0048]
As a configuration of this compression, for example, the thickness of the spring portion 52 of the vibration isolating member 50 shown in FIG. 1 may be increased.
[0049]
In the above-described embodiment, the vibrator 21 has a tuning fork shape made of a piezoelectric element. However, for example, the vibrator 21 may have a shape in which one end of a prism is fixed, or a shape in which both ends of a prism are free. May be used. Further, the same operation and effect can be obtained even with a vibrator made of a semiconductor.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing an entire configuration of an angular velocity sensor according to a first embodiment of the present invention.
2A is a configuration diagram of a sensor unit in FIG. 1 as viewed in A, and FIG. 2B is a transmission diagram in B of FIG.
FIG. 3 is a perspective view showing a main part configuration of a sensor unit of FIG. 2;
FIG. 4 is a development view of the vibrator of FIG.
FIG. 5 is a characteristic diagram showing a relationship between a temperature change and a vibration output.
FIG. 6 is a characteristic diagram showing the relationship between the temperature at which the warm projections T occur and the respective resonance frequencies of the vibrator and the vibration isolating member.
FIG. 7 is a relational expression related to a resonance frequency of the holding unit 51.
FIG. 8 is a characteristic diagram showing a relationship between a propagation constant and a protrusion generation temperature.
FIG. 9 is an explanatory view showing a shape of a holding portion 51 of the vibration isolating member 50.
FIG. 10 is a characteristic diagram showing a relationship between a propagation constant and a protrusion generation temperature in the shape of each sex member.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... case, 20 ... sensor part, 21 ... vibrator, 22 ... base, 50 ... vibration isolating member, 51 ... holding part, 52 ... spring part, 60 ... frame

Claims (11)

A sensor unit having at least a vibrator for detecting an angular velocity about a predetermined axis and a base on which the vibrator is fixed,
An angular velocity sensor, comprising: a vibration isolating member provided in the sensor unit and having a resonance frequency separated by 3% or more from the resonance frequency of the vibrator. 2. The angular velocity sensor according to claim 1, wherein a resonance frequency of the vibration isolating member is lower than a resonance frequency of the vibrator by 3% or more with respect to a resonance frequency of the vibrator. 3. 2. The angular velocity sensor according to claim 1, wherein a resonance frequency of the vibration isolation member is higher than a resonance frequency of the vibrator by 3% or more with respect to a resonance frequency of the vibrator. 3. The angular velocity sensor according to any one of claims 1 to 3, further comprising a support between the vibrator and the base for fixing the vibrator and the base. The angular velocity sensor according to claim 1, wherein the sensor unit is held in the case via the vibration isolating member. A sensor unit having at least a vibrator for detecting an angular velocity about a predetermined axis and a base on which the vibrator is fixed,
A case for housing the sensor unit,
An angular velocity comprising: a spring portion that elastically supports the sensor portion by separating the sensor portion from the case; and a vibration isolating member including a holding portion that holds the sensor portion by inserting at least a part of the base through an insertion hole. A sensor,
The angular velocity sensor according to claim 1, wherein the vibration isolation member has a resonance frequency that is at least 3% apart from a resonance frequency of the holding unit of the vibrator. 7. The angular velocity sensor according to claim 6, wherein a resonance frequency of the holding portion of the vibration isolating member is smaller than a resonance frequency of the vibrator by 3% or more with respect to a resonance frequency of the vibrator. 7. The angular velocity sensor according to claim 6, wherein a resonance frequency of the holding portion of the vibration isolator is higher than a resonance frequency of the vibrator by 3% or more with respect to a resonance frequency of the vibrator. The material constituting the holding portion of the vibration isolating member is selected such that the resonance frequency of the holding portion of the vibration isolating member is separated from the resonance frequency of the vibrator by 3% or more. Item 9. The angular velocity sensor according to any one of Items 6 to 8. The thickness of the vibration isolating member in the same direction as the thickness of the base-side mounting portion is adjusted such that the resonance frequency of the holding portion of the vibration isolating member is separated from the resonance frequency of the vibrator by 3% or more. The angular velocity sensor according to claim 6, wherein: A sensor unit having at least a vibrator for detecting an angular velocity about a predetermined axis and a base on which the vibrator is fixed,
A case for housing the sensor unit,
An anti-vibration member for fixing the sensor unit in the case,
An angular velocity sensor comprising a frame member provided between the vibration isolating member and the case so that the sensor portion is held in the case by applying a compressive stress to the vibration isolating member. hand,
The angular velocity sensor according to claim 1, wherein the vibration isolating member has a resonance frequency that is at least 3% apart from a resonance frequency of the vibrator.

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