JPH07280572A - Method for adjusting output of piezoelectric type angular velocity sensor - Google Patents

Abstract

PURPOSE:To provide an output adjusting method for piezoelectric type angular velocity sensor with suppressed offset noise and its manufacturing method. CONSTITUTION:The method is used for adjusting the output of a piezoelectric type angular velocity sensor 1 provided with a prismatic vibrating part 11. A first side face 111 of the part 11 is joined with a piezoelectric element 20 for vibration and a second side face 112 thereof is joined with a piezoelectric element 20 for detection respectively, and the element 20 is provided with a piezoelectric body 21 and an electrode 22. After the element 20 is joined with the part 11, the electrode 22 and body 21 are partly cut off so as to adjust the output of the element 20. Therefore the output of the sensor 1 can be adjusted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an output adjusting method and a manufacturing method of an angular velocity sensor for detecting a motion around a reference axis when a vehicle is running.

[0002]

2. Description of the Related Art As a piezoelectric angular velocity sensor having a simple shape and easy to process, there has been proposed a piezoelectric angular velocity sensor using a Y-shaped branched prismatic tuning fork and a piezoelectric element. As shown in FIG. 10, the piezoelectric angular velocity sensor 9 has a prismatic vibrating portion 91.
Are arranged in parallel to form a Y-shaped tuning fork-shaped vibrator, and each vibrating portion 91 is provided with an exciting piezoelectric element 92 for generating bending vibration and a vibrating portion 9 by Coriolis force.
The detection piezoelectric element 93 for detecting the stress generated in 1
It is joined to the side surfaces 911 and 912 of each vibrating portion 91.

The piezoelectric elements 92 and 93 are joined to separate side surfaces 911 and 912 which are orthogonal to each other. In addition, the first side surface 911 to which the excitation piezoelectric element 92 is joined
A feedback piezoelectric element 94 is joined to the sensor, and senses the vibration (Fv) of the vibrating portion 91 by the excitation piezoelectric element 92 and feeds it back to the control power source (not shown) of the excitation piezoelectric element 92. .

When an external force with an angular velocity Ω is applied from the outside, a Coriolis force causes a vibration Fc in a direction perpendicular to the vibration Fv, and a voltage signal corresponding to the angular velocity Ω is generated in the detecting piezoelectric element 93. To do. Further, as a piezoelectric angular velocity sensor having another shape, there is a sound piece type piezoelectric angular velocity sensor including one prismatic vibrating portion (see FIGS. 7 to 9).

[0005]

However, the conventional piezoelectric angular velocity sensor described above has the following problems. That is, offset noise is generated in the detection piezoelectric element 93. That is, when the vibrating portion 91 is vibrated by the excitation piezoelectric element 92, a voltage output in phase with the feedback piezoelectric element 94 is generated in the detection piezoelectric element 93 even if the angular velocity Ω is zero, and as a result, the detection output S / N ratio is deteriorated.

Such a phenomenon does not theoretically occur if the detecting piezoelectric element 93 is homogeneous and is arranged symmetrically with respect to the neutral axis of vibration, but in reality, the detecting piezoelectric element 93 is actually used. It is caused by various factors such as non-uniform joining of the element 93, displacement of the joining position, and distortion of the neutral axis of the vibrating part.

That is, as shown in FIG. 11, when the vibrating part 91 is bent, if the detecting piezoelectric element 93 is uniform and symmetrical with respect to the neutral axis C of bending, the output of the compressive stress F ₁ and the tensile force are applied. The output of the stress F ₂ is balanced and offset, and offset noise does not occur. However, offset noise occurs due to the various factors described above. In addition, this offset noise also fluctuates with changes in ambient temperature.

The present invention has been made in view of such conventional problems, and an output adjusting method of a piezoelectric angular velocity sensor capable of reducing offset noise from a detecting piezoelectric element and improving angular velocity detection accuracy. And a method of manufacturing a piezoelectric angular velocity sensor with high accuracy using such an output adjusting method.

[0009]

The present invention is a method for adjusting the output of a piezoelectric angular velocity sensor having a prismatic vibrating portion, wherein an exciting piezoelectric element is bonded to a first side surface of the vibrating portion, and
A piezoelectric element for detection is bonded to a second side surface orthogonal to the side surface of the piezoelectric element, and the piezoelectric element for detection is a piezoelectric element sensitive to stress and a signal extracting element arranged on the surface of the piezoelectric element. The piezoelectric element for detection has a suitable value for the output of the piezoelectric element for detection by partially cutting off the electrode and the piezoelectric body under the electrode after the piezoelectric element for detection is joined to the vibrating portion. And a method for manufacturing a piezoelectric angular velocity sensor using the output adjusting method.

The most remarkable point in the present invention is that
After joining the detecting piezoelectric element to the vibrating portion, the electrode and the piezoelectric body under the electrode are partially cut off, and the output of the detecting piezoelectric element is adjusted to an appropriate value. Of particular note is that the cutting of the piezoelectric element is performed by cutting both the electrode and the piezoelectric body below the electrode.

The adjustment to an appropriate value in the above means to suppress the offset noise as much as possible and obtain an appropriate signal level. Adjustment of the value of the offset noise is performed, for example, under an arbitrary normal temperature.
The piezoelectric element for excitation is driven with the angular velocity set to zero to excite the vibrating portion, and the output value of the piezoelectric element for detection is minimized.

[0012]

In the output adjusting method (and the manufacturing method, the same applies hereinafter) according to the present invention, the output and the piezoelectric element under the electrode are cut off after the piezoelectric element for detection is bonded to the vibrating portion. To do. As a result, after joining the piezoelectric elements, as shown in FIG.
Even if an imbalance (so-called offset noise) occurs between the output of the compressive stress F _{1 and} the output of the tensile stress F ₂ shown in ( ₂ ), the electrodes and the piezoelectric element can be cut off to balance both outputs.

That is, the electrode and the piezoelectric element on the side with a large output are cut off to suppress the output, and the compressive stress F ₁ and the tensile stress F _{2 are applied.}
The outputs of can be balanced. Since both the electrode and the piezoelectric element under the electrode are cut off, there is an effect that the output balance of both stresses F ₁ and F ₂ is unlikely to be lost even if the ambient temperature changes. The reason will be described below.

By leaving the piezoelectric material as it is and cutting off only the electrode, both stresses F ₁ and F at a certain temperature can be obtained.
The output of ₂ can be balanced and the offset noise can be made extremely small. However, this method has a problem that the offset noise increases again when the temperature changes.

That is, as shown in FIGS. 12 and 13, when only the electrode 931 on the surface of the detecting piezoelectric element 93 is cut off and the piezoelectric body 932 under the electrode is left, the offset noise at a certain temperature becomes a minimum value. Increases with changes in temperature. As shown in FIG. 13, when only the surface electrode 931 is removed, the internal electrode 9 corresponding to the removed surface electrode 933 is removed.
34 and the piezoelectric body 932 remain, and when the ambient temperature changes by ΔT, the vibrating portion 91 corresponds to this temperature change ΔT.
Change Δ that occurs on one side of the neutral axis C of the bending vibration of
There is a difference between V ₁ and the output change ΔV ₂ that occurs on the other side.

This difference is due to the piezoelectric body below the excised front surface electrode 933, resulting in an increase in offset noise as a result of temperature change. However,
If the surface electrode and the piezoelectric body under the electrode are removed as in the present invention, the offset noise due to the output imbalance hardly changes even if the temperature changes (ΔV ₁ = ΔV ₂ ). Therefore, according to the output adjusting method of the present invention, the angular velocity detection accuracy is good even if the temperature changes.

As described above, according to the present invention, an output adjusting method for a piezoelectric angular velocity sensor capable of reducing offset noise from the detecting piezoelectric element and improving the detection accuracy of the angular velocity, and such output adjustment. It is possible to provide a highly accurate method for manufacturing a piezoelectric angular velocity sensor using the method.

[0018]

【Example】

Example 1 An output adjusting method for a piezoelectric angular velocity sensor according to an example of the present invention will be described with reference to FIGS. As shown in FIG. 1, the piezoelectric angular velocity sensor of this example is a piezoelectric angular velocity sensor 1 having a pair of prismatic vibrating portions 11 that branch left and right from a connecting portion 13. First side surface 111 of vibrating portion 11
The excitation piezoelectric element 30 is bonded to the first side surface 112, and the detection piezoelectric element 20 is bonded to the second side surface 112 orthogonal to the first side surface 111.

The detecting piezoelectric element 20 has a piezoelectric body 21 sensitive to stress and an electrode 22 for extracting a signal, which is arranged on the surface of the piezoelectric body 21. In this example, after the detection piezoelectric element 20 is bonded to the vibrating portion 11, the electrode 22 and the piezoelectric body 21 under the electrode 22 are partially cut off so that the output of the detection piezoelectric element 20 has an appropriate value. Adjust to.

Each of these will be described in detail below. Vibration part 1
Reference numeral 1 is made of a highly elastic material such as metal and is formed into a prismatic shape having a rectangular cross section. And the vibrating section 11
Are arranged in parallel to the left and right of the connecting portion 13 to form a tuning fork. The connecting portion 13 of the tuning fork is fixed to the base 14 by press fitting or the like.

As shown in FIG. 1, each of the vibrating portions 11 has a plate-shaped excitation piezoelectric element 30 and a feedback piezoelectric element 3.
1, and the piezoelectric element 20 for detection are joined. Each of the piezoelectric elements 30, 31, 20 includes a ceramic piezoelectric body 301, 311, 21 such as PZT and electrodes 302, 31.
It consists of 2, 22.

Excitation piezoelectric element 30 and feedback piezoelectric element 31
The first side surface 111 that joins and is formed at a right angle to the second side surface 112 that joins the detection piezoelectric element 20.
The excitation piezoelectric element 30 applies an AC voltage to the electrode 302 and causes the vibrating portion 11 to flexurally vibrate in the Fv direction in the figure.

The feedback piezoelectric element 31 includes the vibrating section 11
The bending vibration in the Fv direction is detected and fed back to a control device (not shown), and the control device (ECU or the like) controls the power supply of the excitation piezoelectric element 30 so that the vibration part 11 can obtain a bending vibration of a predetermined magnitude. To operate. On the other hand, the detecting piezoelectric element 20 detects the vibration stress F _c due to the Coriolis force generated in the direction perpendicular to Fv by the angular velocity Ω.

At this time, due to the displacement of the bonding position of the detection piezoelectric element 20, the non-uniform bonding state, the displacement of the neutral axis of the bending vibration of the vibrating portion 11, and the like, the detection piezoelectric element 20 returns the feedback piezoelectric element. So-called offset noise having the same phase as the voltage generated from the element 31 is generated, and the detection accuracy of the angular velocity Ω deteriorates, that is, the S / N ratio deteriorates.

Therefore, in the present embodiment, in order to reduce the offset noise, the following method of adjusting the angular velocity sensor is adopted. That is, when the vibrating portion 11 is flexurally vibrated by the exciting piezoelectric element 30, the state of stress generated in the vibrating portion 11 is as shown in FIG. The curve on the side surface 112 in FIG.

In particular, the stress distribution of the vibrating portion 11 in the excitation direction (y direction in FIG. 2) is symmetrical with respect to the center line C ₀ of the vibrating portion 11 as shown in FIG. 11
As shown in FIG. 2C, the stress distribution in the longitudinal direction (z direction in FIG. 2) becomes maximum toward the root of the vibrating portion 11 (on the side of the connecting portion 13).

In the vibrating portion 11 of the prismatic tuning fork having such a stress distribution, if the detecting piezoelectric element 20 is bonded to the vibrating portion 11 symmetrically with respect to the center line C ₀ of the vibrating portion 11, the detecting piezoelectric element 20 will be described. The stress applied in the direction of excitation is canceled in the plane, and offset noise does not occur from the detection piezoelectric element 20.

However, as described above, the positional deviation Δ in the driving direction is caused as shown in FIG.
When y occurs, the stress in the excitation direction applied to the detection piezoelectric element 20 is not canceled in the plane, and the offset voltage V ₀ from the detection piezoelectric element 20 as shown in FIG.
Will occur.

Therefore, in this embodiment, the exciting piezoelectric element 30 is used.
The electrode 22 of the detection piezoelectric element 20 shown in FIG. 1 is monitored while the offset voltage V ₀ output from the detection piezoelectric element 20 is monitored while the vibrating portion 11 is flexibly vibrated by the
The offset voltage V ₀ is made zero by scraping off a part of the piezoelectric body 21 with a grinder or the like.

Next, the relationship between the piezoelectric element cutting amount of the detecting piezoelectric element 20 and the offset voltage V ₀ will be described with reference to FIG. FIG. 3 shows the positional deviation Δy of the detection piezoelectric element 20.
FIG. 6 is a characteristic diagram showing an experimental result of the relationship between the offset voltage V ₀ and the offset voltage V ₀ .

“Δ” in FIG. 3 shows experimental data, but as shown in FIG.
_{Since 0} is affected not only by the positional deviation Δy but also by the uneven adhesion between the detection piezoelectric element 20 and the vibrating section 11, the value of the offset voltage V ₀ will vary somewhat.

However, as is known from the experimental data in the figure, it roughly agrees with the approximate straight line 51 shown by the broken line in FIG. Therefore, in order to make the offset voltage V ₀ zero, the zero point of the positional deviation Δy (in FIG.
The outer edge of the side surface 112) of the center of the side 112, and the position deviation Δy is 2 so that the position deviation (−Δy) is almost the same in the opposite direction.
The piezoelectric body 21 and the electrode 2 of the detecting piezoelectric element 20 are doubled in amount.
2 may be cut in the vertical direction (z direction in FIG. 2) (reference numeral 201 in FIG. 1 indicates a cut-out portion of the detection piezoelectric element 20, but the cut-out portion 201 is cut in the vertical direction as described below. Not limited to those that are penetrated).

Next, a method for making the offset voltage V ₀ zero will be described with reference to FIGS. 4 and 5. Figure 4 shows
Grinding when a part of the detection piezoelectric element 20 is ground in the vertical direction (z direction in FIG. 2) with a predetermined groove width W (W = 0.1 mm, y direction in FIG. 2) as shown in (a). It is a characteristic view (b) showing the experimental result of the relationship between the length L and the offset voltage V ₀ . FIG. 5 is a characteristic diagram showing an experimental result of the relationship between the groove width W and the amount of change in the offset voltage V ₀ when grinding is performed with a predetermined grinding length L (L = 13 mm).

The angular velocity sensor 1 used in the experimental results shown in FIGS. 4 and 5 has a size of 30 mm and a cross section of 3 mm.
The angular velocity sensor includes a vibrating portion 11 having a size of 3 mm × 3 mm, an exciting piezoelectric element 30 having a length of 13 mm, a width of 3 mm, and a plate thickness of 0.2 mm, and a detecting piezoelectric element 20. An alternating voltage of 2 V was applied to the excitation piezoelectric element 30, and a pencil grinder was used to cut off the piezoelectric body 21 and the electrode 22.

Then, as shown in FIG. 4A, when the piezoelectric body 21 of the detecting piezoelectric element 20 is sequentially shaved from the connecting portion 13 side, as shown in FIG. 2B, at the base of the vibrating portion 11. Since the stress increases as the distance increases, the degree of change in the offset voltage V ₀ increases as shown in FIG. 4B.
Further, as shown in FIG. 5, when the shaving width W is successively increased, the offset voltage V ₀ gradually increases.

Therefore, an example of the adjustment process of the angular velocity sensor based on the result of this experiment will be described next. FIG. 6 is a flowchart showing the adjustment process of the angular velocity sensor of this example. In FIG. 6, in step 601, an AC voltage is supplied to the exciting piezoelectric element 30 of the angular velocity sensor 1 to vibrate the vibrating portion 11 in the exciting direction Fv.

Subsequently, in step 602, the offset voltage V ₀ generated by the detection piezoelectric element 20 bonded to each vibrating section 11 is detected. Subsequently, in step 603, it is determined whether or not this offset voltage V ₀ is zero. If the offset voltage V ₀ is already zero at this point, the detecting piezoelectric element 20 is bonded to the vibrating section 11 symmetrically with respect to the center line C ₀ (FIG. 2) of the vibrating section 11. Judge and finish the adjustment.

However, when the offset voltage V ₀ is not zero in the judgment of step 603, the routine proceeds to step 604, where the grinding of the detecting piezoelectric element 20 is started.
At this time, based on the above-mentioned experimental results, the grinding direction of the detecting piezoelectric element 20 is as shown in FIG.
It is advisable to perform grinding from point (B) on the side 3 toward the point (C) on the free end side of the vibrating portion 11. If you do this,
Since the stress becomes weaker toward the free end side of the vibrating portion 11 and the change amount of the offset voltage V ₀ becomes smaller, it becomes easier to perform fine adjustment at the end of the adjustment stage.

Then, almost in synchronism with this grinding, in step 605, it is judged again whether or not the offset voltage V ₀ is zero. At this time, as shown in FIG. 6, when the offset voltage V ₀ does not become zero, steps 604, 6
The processing of 05 is repeated. Then, when the offset voltage V ₀ becomes zero, the process proceeds to step 606, the search is stopped, and the series of adjustment processes is completed.

If the grinding from point (B) to point (C) shown in FIG. 4 is still insufficient, the position is further shifted so as to move from point (B) to point (C). It may be ground. Also in this grinding direction, rather than grinding in one line from point (B) to point (C), for example, the vicinity of point (B) is ground first to roughly adjust the offset voltage V _0. , Later fine adjustment (C)
It may be performed near the point.

In the output adjusting method of this example,
Not only the electrode 22 is cut off from the detection piezoelectric element 20, but also the piezoelectric body 21 is cut off. Therefore, even if the ambient temperature changes, the output balance of the detection piezoelectric element 20 on the left and right of the vibration center axis C ₀ is not disturbed. Therefore,
Even if the temperature changes, the offset noise V ₀ hardly increases.

As described above, according to this example, the offset noise can be reduced and the angular velocity detection accuracy can be improved regardless of the ambient temperature. Then, if the output adjusting method as in this example is carried out, it is possible to manufacture a piezoelectric angular velocity sensor with little offset noise and high detection accuracy.
As described above, according to this example, there is little offset noise of the piezoelectric element for detection, and the output adjustment method of the piezoelectric angular velocity sensor that can improve the detection accuracy of the piezoelectric angular velocity sensor,
Further, it is possible to provide a highly accurate method for manufacturing a piezoelectric angular velocity sensor using such an output adjusting method.

Embodiment 2 As shown in FIG. 7, this embodiment is an example of application to a sound piece type piezoelectric angular velocity sensor 10 consisting of one vibrating section 12, and the piezoelectric angular velocity sensor 10 has one Excitation piezoelectric elements 33 and 2
It has the individual detecting piezoelectric elements 24 and 25. As shown in FIG. 7, the excitation piezoelectric element 33 is bonded to the central portion of the first side surface 121 of the vibrating portion 12, and the pair of detection piezoelectric elements 24 and 25 is bonded to the upper and lower sides of the second side surface 122. There is.

In this example, the feedback piezoelectric element is composed of the vibrating section 12
Is arranged on the opposite side of the first side surface 121. And
The ends 241 and 251 of the detection piezoelectric elements 24 and 25 are cut off, and the output is adjusted so that the offset voltage V ₀ is minimized. In the figure, reference numeral 123 is a metal wire rod for supporting the vibrating portion 12. Others are the same as those in the first embodiment.

Example 3 In this example, as shown in FIG. 8, another piezoelectric angular velocity in which the number of excitation piezoelectric elements 34 and 35 is two and the number of detection piezoelectric element 26 is one in the second embodiment. It is an application example to the sensor 10. That is, a pair of excitation piezoelectric elements 34 and 35 are bonded above and below the first side surface 121 of the vibrating portion 12, and the second side surface 1
One detection piezoelectric element 26 is bonded to the central portion of 22. In the figure, reference numeral 261 indicates a piezoelectric element 26 for detection.
Is the excised part. Others are the same as in the second embodiment.

Example 4 This example is an example of application to a piezoelectric angular velocity sensor 10 in which an exciting piezoelectric element 33 and a detecting piezoelectric element 26 are joined to the central portion of a vibrating portion 12, as shown in FIG. . The piezoelectric angular velocity sensor 10 of this example is similar to the second embodiment in that the support pin 1
23 (not shown in FIG. 9) is used to support two points, or one end of the diaphragm 12 is press-fitted to be supported. Others are the same as those in the second or third embodiment.

[Brief description of drawings]

FIG. 1 is a perspective view of a piezoelectric angular velocity sensor according to a first embodiment.

FIG. 2 is an iso-stress diagram in the vibrating part of Example 1 (a).
And a change curve (b) of the stress value in the y direction of the transverse section BB of the vibrating part, and a change curve (c) of the stress value in the z direction on the side surface 111.

FIG. 3 is a correlation diagram between the positional deviation Δy (FIG. 2) and the output V ₀ of the detection piezoelectric element according to the first embodiment.

FIG. 4 is an explanatory view (a) showing a cut length L of the detection piezoelectric element of the first embodiment and a correlation diagram (b) between L and an output change amount.

5 is a correlation diagram between the cutting width W and the amount of change in output voltage shown in FIG. 4 in the detection piezoelectric element of Example 1. FIG.

FIG. 6 is a flowchart of an output adjustment process of the piezoelectric angular velocity sensor according to the first embodiment.

FIG. 7 is a perspective view of a piezoelectric angular velocity sensor according to a second embodiment.

FIG. 8 is a perspective view of a piezoelectric angular velocity sensor according to a third embodiment.

FIG. 9 is a perspective view of a piezoelectric angular velocity sensor according to a fourth embodiment.

FIG. 10 is a perspective view of a conventional piezoelectric angular velocity sensor.

FIG. 11 is a schematic diagram of deformation of a conventional piezoelectric angular velocity sensor during excitation.

FIG. 12 is an explanatory diagram of an output adjustment method of a conventional piezoelectric angular velocity sensor.

13 is a view on arrow A of FIG.

[Explanation of symbols]

 1,10. ． ． Piezoelectric angular velocity sensor, 11. ． ． Vibration part, 111, 112. ． ． Side, 20. ． ． Detecting piezoelectric element, 21. ． ． Piezoelectric body, 22. ． ． Electrode, 30. ． ． Excitation piezoelectric element,

Claims (3)

[Claims] 1. A method of adjusting the output of a piezoelectric angular velocity sensor having a prismatic vibrating portion, wherein an exciting piezoelectric element is bonded to a first side surface of the vibrating portion and is orthogonal to the first side surface. A detection piezoelectric element is bonded to the second side surface, and the detection piezoelectric element has a piezoelectric body sensitive to stress and an electrode for signal extraction arranged on the surface of the piezoelectric body. Therefore, after the detection piezoelectric element is bonded to the vibrating portion, the electrode and the piezoelectric body under the electrode are partially cut off,
An output adjusting method for a piezoelectric angular velocity sensor, characterized in that the output of the detecting piezoelectric element is adjusted to an appropriate value. 2. The method of adjusting the output of the detection piezoelectric element according to claim 1, wherein the excitation piezoelectric element is driven with an angular velocity of zero under normal temperature to minimize the output value of the detection piezoelectric element. A method for adjusting the output of a piezoelectric angular velocity sensor, which is an adjustment. 3. A method of manufacturing a piezoelectric angular velocity sensor, characterized in that the manufacturing method includes the output adjusting method according to claim 1 or 2.