WO2005052601A1

WO2005052601A1 - Acceleration detection device

Info

Publication number: WO2005052601A1
Application number: PCT/JP2004/014632
Authority: WO
Inventors: Jun Tabota
Original assignee: Murata Manufacturing Co., Ltd.
Priority date: 2003-11-26
Filing date: 2004-10-05
Publication date: 2005-06-09
Also published as: JPWO2005052601A1

Abstract

[PROBLEMS] To provide an acceleration detection device capable of independently detecting an acceleration in a direction parallel with a mounting plane and an acceleration in a direction vertical thereto by mounting two acceleration sensors on one mounting plane. [MEANS FOR SOLVING PROBLEMS] These two same acceleration sensors (A) and (B) having the directions of axes of the maximum sensitivities relative to the sensor mounting plane (10) angled by θ relative to the mounting plane (10) are installed in the mounting plane (10) in the state of being inverted by 180˚each other. The acceleration in the direction vertical to the mounting plane can be provided by using the sum (SA + SB) of outputs (SA) and (SB) from the two acceleration sensors, and the acceleration in the direction parallel with the mounting plane can be detected by using a difference (SA - SB) between the outputs (SA) and (SB) independently of the acceleration in the vertical direction.

Description

Specification

Acceleration detector

Technical field

The present invention relates to an acceleration detection device, and more particularly to an acceleration detection device that can independently detect acceleration in two perpendicular directions using two acceleration sensors.

Background art

[0002] Conventionally, an acceleration sensor has been used to detect impact or acceleration applied to a magnetic hard disk device. In the case of a magnetic hard disk drive, the structurally vulnerable to impact is the mechanism of the head arm 1 that is rotationally driven in a pivot shape as shown in FIG. This mechanism is weak in the direction perpendicular to the surface of the magnetic disk 2 and in the radial direction, but relatively strong in the longitudinal direction of the head arm 1. Therefore, when detecting acceleration or impact in order to protect such a mechanism, it is effective to detect acceleration in two-axis directions, which is weaker than in all three-axis directions. This direction corresponds to a horizontal direction and a vertical direction with respect to the sensor mounting surface 3.

[0003] As shown in FIG. 2, when the mounting plane 3 of the acceleration sensor is an XY plane and the direction perpendicular to the XY plane is the Z direction, the acceleration applied in two directions of the X axis (or Y axis) and the Z axis Independent detection of the horizontal acceleration sensor 4 with at least the maximum sensitivity axis in the direction parallel to the XY plane 3 and the vertical acceleration sensor 5 with the maximum sensitivity axis in the Z-axis direction It is necessary to use different types of sensors.

However, the horizontal type sensor 4 and the vertical type sensor 5 often have completely different structures due to the mounting surface, so it is necessary to prepare two types of sensors separately, which increases the cost. there were.

[0004] On the other hand, as shown in FIG. 3, two orthogonal surfaces comprising a horizontal mounting surface 6 and a vertical mounting surface 7 are provided, and the same type (for example, a horizontal type) sensor 8 is provided on these mounting surfaces 6, 7. By attaching, 9 respectively, it is also possible to measure acceleration in two directions of X axis and Z axis independently. In this case, the cost required for the sensor can be reduced. Since two orthogonal mounting surfaces 6 and 7 are required, there is a disadvantage that the thickness of a product such as an electronic device is increased. [0005] Patent Document 1 discloses that two acceleration sensors whose maximum sensitivity axis directions with respect to the sensor mounting plane are neither parallel nor perpendicular to the mounting plane are mounted on the mounting plane in a direction orthogonal to X, Υ. Acceleration detectors have been proposed that can detect accelerations in three axes, Z and Z.

This device has the advantage of being able to detect a wide range of acceleration with a small number of acceleration sensors.The force can be detected independently by detecting the relative ratio of the acceleration components of the three axes alone. Not in translation.

Patent Document 1: JP-A-8-201419

Disclosure of the invention

Problems to be solved by the invention

[0006] Therefore, an object of the present invention is to mount two acceleration sensors on a single mounting plane so that acceleration in a direction parallel to the mounting plane and acceleration in a direction perpendicular to the mounting plane can be detected independently. It is to provide a device.

Means for solving the problem

[0007] In order to achieve the above object, the invention according to claim 1 provides two acceleration sensors having the same sensitivity axis whose maximum sensitivity axis direction to the sensor mounting plane is neither parallel nor perpendicular to the mounting plane. Means for inverting by 180 ° in the mounting plane, means for calculating the sum (S + S) of the outputs S 1 and S 2 of the two acceleration sensors, and the outputs S 1 and S 2

A B A B A B

And means for determining the difference (S—S) between the mounting planes are calculated from the sum of the outputs (S + S).

A B A B

The acceleration in the direction perpendicular to the mounting plane from the output difference (S-S)

A B

Provided is an acceleration detection device characterized in that acceleration in a direction can be independently detected.

[0008] Two acceleration sensors whose maximum sensitivity axis direction with respect to the sensor mounting plane is oblique to the mounting plane are mounted to be inverted by 180 ° in the mounting plane. For example, if the mounting plane is an XY plane and the sensitivity axis directions of the two sensors are arranged along the X axis direction, the outputs S and S of these acceleration sensors include components in the X axis direction and the Z axis direction . Of two acceleration sensors

A B

Since the sensitivity axis direction is inverted by 180 °, the components of the outputs S and S in the Z-axis direction are the same and X

A B

The component in the axial direction is reversed. Therefore, the sum of these outputs (S + S)

A B

Direction acceleration can be detected, and the X-axis direction acceleration is detected from the difference between these outputs (S-S).

A B

it can. Since these accelerations are independent data that are not affected by each other, Acceleration can be detected individually.

As described above, in the present invention, it is only necessary to use two identical acceleration sensors having the same maximum sensitivity axis and mount them in a reversed manner on one sensor mounting plane, so that the cost of the acceleration sensor can be reduced and The thickness of the product does not increase.

[0009] As described in claim 2, it is preferable that the direction of the maximum sensitivity axis of the acceleration sensor is within a range of 20-70 ° in the vertical direction from the mounting plane.

The direction of the maximum sensitivity axis of the acceleration sensor used in the present invention with respect to the sensor mounting plane is neither parallel nor perpendicular to the mounting plane. That is, the angle 0 with respect to the mounting plane in the direction of the maximum sensitivity axis is 0 ° <Θ <90 °.

At 0 = 0 ° and 90 °, there is no sensitivity in one of the X and Z axes. Otherwise, Θ may be any angle. However, in order to detect with higher sensitivity, the difference between the sensitivity in the X-axis direction and the sensitivity in the X-axis direction is preferably as small as possible. Therefore, it is better to set 20 ° ≤ Θ≤70 °.

The most desirable angle in the above range is 45 °. Because it is the force that can make the sensitivity of both XZ axes almost equal.

[0010] According to claim 3, the acceleration sensor includes a detection element made of piezoelectric ceramics and an insulating case for housing the detection element, and the detection element is formed on a bottom surface of the insulation case forming a sensor mounting plane. It is stored and held in an oblique direction with respect to the object.

An example of such an acceleration sensor is disclosed in Japanese Patent Application Laid-Open No. Hei 7-20144.

Since this sensor is small and inexpensive, and has a substantially constant maximum sensitivity axial direction, it can accurately detect the acceleration.

[0011] As in claim 4, means for obtaining the sum (S + S) of the outputs of the two acceleration sensors and the difference (S

A B

The means for determining (S) should have the function of independently adjusting the amplification factor.

A B

No.

The two-axis acceleration can be detected independently from the sum (S + S) and difference (S-S) of the outputs,

A B A B

If the angle 0 to the mounting plane in the direction of the sensitivity axis is other than 45 °, the sensitivity of the sum difference will be different. Therefore, the amplification factor can be adjusted independently for the means for obtaining the sum and the means for obtaining the difference. By adding the function, the sensitivity of sum and difference can be made the same, and acceleration in two axes can be detected with the same sensitivity.

The invention's effect

[0012] According to the invention described in claim 1, two acceleration sensors whose maximum sensitivity axis direction with respect to the sensor mounting plane is oblique to the mounting plane are mounted to be inverted by 180 ° in the mounting plane. So, from the sum of the outputs of the two acceleration sensors (S + S), it is perpendicular to the mounting plane

A B

Direction acceleration can be detected, and the acceleration parallel to the mounting plane can be calculated from the output difference (S-S).

A B

Can be detected. Since these accelerations are independent data, the acceleration of each axis can be detected individually.

Further, in the present invention, since two identical acceleration sensors may be used, the cost of the acceleration sensor can be reduced, and these sensors need only be inverted and mounted on one sensor mounting plane. The problem that the thickness of the product increases can be solved. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to examples.

Example 1

FIG. 4 shows a first embodiment of the acceleration detection device according to the present invention.

In this acceleration detection device, an acceleration sensor A and an acceleration sensor B are mounted on a sensor mounting plane 10 by inverting 180 ° in the mounting plane 10. The maximum sensitivity axis directions P and P of the sensors A and B with respect to the sensor mounting plane 10 are

A B

Have been.

In FIG. 4, assuming that the mounting plane 10 is an XY plane, in this embodiment, the maximum sensitivity axis direction P of the acceleration sensor A is inclined in the Z axis direction by an angle に対して with respect to the plus direction of the X axis.

A

The maximum sensitivity axis direction P of the acceleration sensor B is the angle Θ with respect to the minus direction of the X axis.

B

It is inclined in the axial direction.

Here, the two sensors A and B are arranged along the X-axis direction. However, if the directions are inverted by 180 ° in the mounting plane 10, the positions are arbitrary.

[0015] Sensors A and B are the same acceleration sensor, and have the same structure as that shown in Japanese Patent Application Laid-Open No. Hei 7-20144. That is, as shown in Fig. 5, a bimorph-type acceleration detection The output element 20 is housed and supported in an insulative case 30 having a strength such as an insulating ceramic with both ends fixed. The bottom surface of the case 30 is mounted on the mounting plane 10.

The acceleration detecting element 20 has a rectangular flat plate shape, and a pair of piezoelectric ceramic plates 23 having a signal electrode 21 and an intermediate electrode 22 formed on the front and back surfaces are face-to-face bonded, and the tilt angle corresponding to the direction of the maximum sensitivity axis P is formed. It was cut off at. Each of the piezoelectric ceramic plates 23 joined via the intermediate electrode 22 is polarized (indicated by an arrow in FIG. 5) in the direction of its own thickness and in the opposite direction to the other side. Further, each of the signal electrodes 21 is drawn out to different ends along the longitudinal direction of each piezoelectric ceramic plate 23. Although not shown, external electrodes from which the signal electrodes 21 of the acceleration detecting element 20 are drawn out are formed on the outer surface of the case 30, and are configured as surface-mounted chip components.

FIG. 6 shows a circuit block for processing the outputs of the acceleration sensors A and B mounted as shown in FIG.

In the figure, the output of sensor A is amplified by first-stage amplifier 11 and input to adders 13 and 14. On the other hand, the output of the sensor B is amplified by the first-stage amplifier 12 having the same amplification degree as the first-stage amplifier 11 and is input to the adder 13, and the output of the first-stage amplifier 12 is inverted by the inverter 15 before and after being inverted. It is input to the adder 14.

The adder 13 increases the output S of the sensor A amplified by the first-stage amplifier 11 and the output S of the sensor A by the first-stage amplifier 12.

A

The width of the output S of the sensor B is added. On the other hand, the adder 14 is amplified by the first-stage amplifier 11.

B

Output S of the sensor A and the sensor amplified by the first-stage amplifier 12 and inverted by the inverter 15.

A

Add the output of sensor B—S. That is, the adder 13 outputs S + S and the adder 14

B A B

Returns S — S.

A B

In this example, an inverter 15 and an adder 14 were used to determine the output difference S — S.

A B

Force A well-known subtractor can also be used.

Here, the measurement principle of the present invention will be described.

Let the acceleration outputs of sensors A and B be S and S (vectors), respectively, and use these as the X, Υ, and Z axes.

A B

Expressed by the components of

S = (K cos θ, 0, K sin θ) S = (— K cos θ, 0, K sin 0)

B B B

It becomes. Where K and K are the sensitivities of each sensor.

A B

Next, the sum (S + S) and the difference (S−S) of the outputs of the sensors A and B are considered.

A B A B

(S + S) = ((K — K) cos 0, 0, (K + K) sin Θ)

A B A B A B

(S -S) = ((K + K) cos 0, 0, (K — K) sin Θ)

A B A B A B

Here, if the sensitivity of each sensor is K = κ = κ,

A B

(S + S) = (0, 0, 2Ksin Θ)

A B

(S -S) = (2Kcos Θ, 0, 0)

A B

It becomes.

In other words, the sum output (S + S) operates as a vertical sensor with main axis sensitivity in the ∑ axis direction.

A B

In this case, the difference output (s-S) works as a horizontal type sensor with main axis sensitivity in the X-axis direction.

A B

For example, if sensors A and B with Θ = 25 ° are used,

(S + S) = (0, 0, 0.845K)

A B

(S — S) = (1. 813K, 0, 0)

A B

It becomes. In other words, this is equivalent to providing a vertical sensor with a sensitivity of 0.845K and a horizontal sensor with a sensitivity of 1.813K.

In this way, the sensitivity of the sum-of-differences that can realize an acceleration detection device that can measure two axes independently is different. . In that case, adders 13 and 14 are provided with a function to adjust the gain independently.For example, when Θ = 25 °, the ratio of the gains of the adders 13 and 14 is calculated as the sensitivity ratio It should be set to the inverse ratio of 1.813: 0.845.

Fig. 7 shows the X: Z sensitivity ratio of the acceleration sensor A alone and the sensitivity ratio of X (S-S): Z (S + S) by the acceleration sensors A and B according to the maximum sensitivity axis angle Θ. It is. This

A B A B

Here, K = l.

According to Fig. 7, 0 has no sensitivity in the direction of one of X and では at 0 ° and 90 °, but other angles can be used. However, even if the gains of the adders 13 and 14 can make the sensitivities of the X and 軸 axes the same, there is a problem of SZN and so on. Therefore, the most desirable angle Θ is 45 °, It can be used without any problem in the range of 20 °-70 °.

Example 2

In the first embodiment, accelerations in the X and Z axis directions are independently detected using two sensors A and B having the same sensitivity axis angle Θ, but as shown in FIG. It is also possible to independently detect acceleration in the X, Υ, and Z-axis directions using three sensors A, B, and C having sensitivity axis angles Θ. The sensors A and B are the same as in the first embodiment, and the sensor C is mounted on the mounting plane 10 in the Y-axis direction. That is, the sensor C is mounted in the direction orthogonal to the sensors A and B.

[0020] The sensitivity of the sensor C in the X, Υ, and Z-axis directions is represented by S (vector), which is represented by a component of each axis.

C

S = (0, K cos Θ, K sin Θ)

C C C

It becomes.

Here, assuming that the sensitivity of sensor c is κ C = κA = κB = κ,

S = (0, Kcos Θ, Ksin Θ)

c

It becomes.

Subtracting the sum output (S + S) from twice the output S of sensor C gives

C A B

2S one (S + S)

C A B

= (0, 2Kcos Θ, 2Ksin θ)-(0, 0, 2Ksin θ)

= (0, 2Kcos θ, 0)

It can be seen that the acceleration of the Υ axis can be detected independently. Thereafter, by passing through an appropriate amplifier as in the first embodiment, the sensitivities of X, Υ, and できる can be made uniform.

In this embodiment, by fixing the same three sensors on the mounting plane 10 in a predetermined direction, accelerations in the X, 加速度, and Ζ-axis directions can be independently detected. Therefore, sensitivity adjustment is easy and the cost of the acceleration sensor can be reduced.

The acceleration detection device according to the present invention is not limited to the above embodiment.

Although the sensor shown in Fig. 5 was used as the acceleration sensor, it is not limited to this, but any sensor that has a sensitivity axis with a constant angle Θ and that has a fixed mounting angle with respect to the mounting plane can be used. .

Fig. 8 shows an example in which three sensors A, Β, and C with the same angle Θ are used to independently detect acceleration in the X, Υ, and Ζ three-axis directions. Not something. Example For example, instead of the sensor c having an oblique sensitivity axis, a known horizontal type acceleration sensor can be attached in the Y-axis direction to independently detect acceleration in the X, Υ, and Z-axis directions. . In this case, it is not necessary to perform the calculation as in the second embodiment.

Brief Description of Drawings

FIG. 1 is a schematic diagram of a magnetic hard disk drive.

FIG. 2 is a perspective view of an acceleration detection device in which two types of acceleration sensors are mounted on one mounting plane.

FIG. 3 is a perspective view of an acceleration detection device in which two acceleration sensors are attached to two orthogonal attachment planes.

FIG. 4 is a perspective view of the acceleration detecting device according to the first embodiment of the present invention in a mounted state.

FIG. 5 is a perspective view of an example of an acceleration sensor used in the present invention.

FIG. 6 is a circuit block diagram for processing an output of an acceleration sensor according to the present invention.

[Fig.7] Sensitivity ratio of X: Z and angle of maximum sensitivity axis direction Θ and (S — S): (S + S)

A B A B

It is a figure showing a sensitivity ratio.

FIG. 8 is a perspective view of an acceleration detecting device according to a second embodiment of the present invention in a mounted state. Explanation of symbols

[0023] A, B acceleration sensor

10 Sensor mounting surface

13, 14 Adder (means for calculating the sum of outputs)

15 Inverter

20 Acceleration detector

30 cases

Claims

The scope of the claims

[1] Two accelerometers having the same sensitivity axis whose maximum sensitivity axis direction to the sensor mounting plane is neither parallel nor perpendicular to the mounting plane are mounted 180 ° inverted in the mounting plane, The sum (S + S) of the outputs S 1 and S 2 of the two acceleration sensors is calculated.

A B A B

Means for determining the difference (S—S) between the outputs S 1 and S 2,

A B A B

From the sum of the outputs (S + S), the acceleration in the direction perpendicular to the mounting plane is calculated as

A B

Acceleration in the direction parallel to the mounting plane can be detected independently from the difference (S-S)

A B

An acceleration detecting device characterized by the above-mentioned.

2. The acceleration detection device according to claim 1, wherein a direction of a maximum sensitivity axis of the acceleration sensor is within a range of 20 to 70 degrees in a vertical direction from the mounting plane.

[3] The acceleration sensor includes a detection element made of piezoelectric ceramics, and an insulating case that houses the detection element,

3. The acceleration detection device according to claim 1, wherein the detection element is housed and held obliquely with respect to a bottom surface of an insulating case forming a sensor mounting plane.

[4] The means for obtaining the sum (S + S) of the outputs and the means for obtaining the difference (S—S)

A B A B

4. The acceleration detecting device according to claim 1, wherein the acceleration detecting device has a function of independently adjusting an amplification factor.