JP2007033319A - Electromechanical transducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact and highly sensitive electromechanical transducer. <P>SOLUTION: The electromechanical transducer includes a spindle, a frame, a beam in an X-axis direction that connects the spindle and frame, and a beam in a Y-direction nearly perpendicular to the X-direction in a plane, and the transducer converts mechanical fluctuations to electric fluctuations. A resistor is separated from the transducer. The transducer has at least three transducers; a first transducer is provided at the beam in the X-direction; a second transducer is provided at the beam in the Y-direction; and a third transducer is provided at the beam in the X-direction or in the Y-direction that converts mechanical fluctuations to electric fluctuations in a Z-axis direction different from the X axis or the Y-axis direction. The structure provides the compact and highly sensitive electromechanical transducer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electromechanical transducer that detects acceleration or tilt angle in a two-dimensional or three-dimensional direction applied to a measured object, and converts this into an electrical signal, and in particular, a small electric device that can be mounted on a portable device or the like. It relates to a mechanical converter.

  With technological innovations such as portable electronic devices and robots, there is an increasing demand for small electromechanical transducers that detect acceleration and tilt angles in two-dimensional or three-dimensional directions. Such an electromechanical transducer has many proposals, but a configuration in which a three-dimensional acceleration component is detected by one electromechanical transducer has been proposed (see, for example, Patent Document 1).

The configuration and function shown in Patent Document 1 will be described with reference to the drawings. 4 is a diagram in which the electromechanical transducer of the prior art shown in Patent Document 1 is rewritten so as not to depart from the gist thereof, and FIG. 4A is a plan view seen from above. FIG. 2B is a cross-sectional view schematically showing the cross section. Reference numeral 100 denotes a substrate, 101 denotes an action portion, 102 denotes a flexible portion, 103 denotes a fixing portion, 104 denotes a weight, 105 denotes a pedestal, and 110 denotes an electromechanical transducer. RX1 to RX4, RY1 to RY4, and RZ1 to RZ4 are piezoresistive elements.
In the conventional electromechanical transducer 110 shown in Patent Document 1, a fixed portion 103, an action portion 101, and a flexible portion 102 are provided on a substrate 100 made of a silicon single crystal plate or the like. A pedestal 105 is provided below the fixed portion 103, and a weight 104 is provided below the action portion 101.

  As shown in FIG. 4A, a plurality of piezoresistive elements RX1 to RX4, RY1 to RY4, and RZ1 to RZ4 are formed on the upper surface of the substrate 100. The piezoresistive element is an element whose resistance value changes due to mechanical deformation, and is arranged on the upper surface of the flexible portion 102 in a predetermined direction.

In FIG. 4A, the horizontal direction in the drawing is defined as the X axis and the vertical direction is defined as the Y axis. Further, the Z axis is defined in a direction perpendicular to the drawing (in FIG. 4B, the vertical direction of the drawing). Thereby, an XYZ three-dimensional coordinate system is defined.
In this coordinate system, four piezoresistive elements RX1 to RX4 for detecting acceleration in the X-axis direction are arranged on the X-axis. In addition, four piezoresistive elements RY1 to RY4 for detecting acceleration in the Y-axis direction are arranged on the Y-axis. Further, four piezoresistive elements RZ1 to RZ4 for detecting acceleration in the Z-axis direction are arranged in the vicinity of the piezoresistive elements RX1 to RX4 on an axis parallel to the X axis.

  Further, in order to detect mechanical deformation related to the XYZ three-dimensional coordinate system, a bridge circuit is configured using these piezoresistive elements. This is shown in FIGS. 5 (a) to 5 (c). As shown in FIG. 5, three sets of bridge circuits are configured using the twelve piezoresistive elements described above. 106 is a power source, and 107 is a voltmeter.

  FIG. 5A shows an X-axis bridge circuit for detecting acceleration in the X-axis direction. RX1 and RX4 are connected in series, and RX2 and RX3 are connected in series in parallel with this to constitute an X-axis bridge circuit. A power source 106 is connected between RX1 and RX2, and between RX4 and RX3, and a voltmeter 107 is connected between RX1 and RX4 and between RX2 and RX3. . The voltmeter 107 measures the voltage Vx.

FIG. 5B is a Y-axis bridge circuit for detecting acceleration in the Y-axis direction. RY1 and RY4 are connected in series, and RY2 and RY3 are connected in series in parallel with this to constitute a Y-axis bridge circuit. A power source 106 is connected between RY1 and RY2, RY4 and RY3, and a voltmeter 107 is connected between RX1 and RX4 and between RX2 and RX3. . The voltmeter 107 measures the voltage Vy.

  FIG. 5C shows a Z-axis bridge circuit for detecting acceleration in the Z-axis direction. RZ1 and RZ3 are connected in series, and RZ2 and RZ4 are connected in series in parallel with this to constitute a Z-axis bridge circuit. A power source 106 is connected between RZ1 and RZ2, between RZ3 and RZ4, and a voltmeter 107 is connected between RZ1 and RZ3 and between RZ2 and RZ4. . The voltmeter 107 measures the voltage Vz.

In the method of assembling the bridge circuit in the prior art disclosed in Patent Document 1, the arrangement position and connection order of the piezoresistive elements on the flexible portion 102 are different between the X axis and the Z axis. That is, in the X-axis bridge circuit, RX1 and RX4, and RX2 and RX3 are connected in series, respectively. In the Z-axis bridge circuit, RZ1 and RZ3, and RZ2 and RZ4 are connected in series, respectively.
By adopting such a configuration, even if the four piezoresistive elements RX1 to RX4 for the X axis and the four piezoresistive elements RZ1 to RZ4 for the Z axis are arranged adjacent to each other in parallel to the X axis, It is possible to detect the acceleration in the X-axis direction and the acceleration in the Z-axis direction separately.

  A conventional electromechanical converter 110 shown in Patent Document 1 is a three-dimensional structure using three known uniaxial electromechanical converters using a known configuration, for example, a cantilever and a strain gauge. Compared to a configuration that detects the acceleration component in the direction, there is an advantage that the manufacturing cost is low and it is suitable for mass production.

Japanese Patent Publication No. 8-7228 (page 7, Fig. 1-6)

  In recent years, further miniaturization of mounted components has been demanded in portable electronic devices and the like. If a small electromechanical transducer that can be mounted on a small electronic device such as a cellular phone is to be constructed, the weight is inevitably formed small. At that time, in order to increase the detection sensitivity even with a small and light weight, it is necessary to devise measures such as making the flexible portion easier to deform. For example, an opening is provided in the flexible part, a thin beam is formed in the X-axis direction and the Y-axis direction, and a weight is supported by the thin beam. As described above, many proposals have been made for a configuration in which a beam (flexible portion) is easily deformed even with a small and light weight.

However, in the conventional technique shown in Patent Document 1, eight piezoresistive elements, RX1 to RX4 and RZ1 to RZ4, are required for detecting acceleration in the X-axis direction and the Z-axis direction. The flexible part 102 is arranged substantially coaxially. Furthermore, each piezoresistive element needs to be connected by wiring in order to form a bridge circuit. Since it is such a structure, the flexible part 102 cannot be made into a thin beam shape. Therefore, the prior art disclosed in Patent Document 1 has a problem that it cannot be mounted on a small electronic device such as a mobile phone that is required to be downsized.
In addition, since the conventional technique shown in Patent Document 1 has a configuration in which many piezoresistive elements and wirings are formed on a beam, the wiring between the piezoresistive elements is subjected to stress due to deformation of the beam, and obstruction such as disconnection. There was a problem that was likely to occur. That is, it cannot be used for a long time.

  Accordingly, an object of the present invention is to provide an electromechanical converter with high reliability that can be mounted on an electronic device that is required to be miniaturized by solving the above-described problems.

  In order to solve the above problems, the electrical converter of the present invention adopts the following configuration.

It has a weight part, a frame part, a beam part in the X-axis direction that connects the weight part and the frame part, and a beam part in the Y-axis direction that is substantially perpendicular to the X-axis direction in a plan view, and electrically controls mechanical fluctuations. An electromechanical converter having a converter for converting into fluctuations,
A resistor is provided apart from the transducer, and the transducer is composed of at least three transducers, the first transducer is provided in the beam portion in the X-axis direction, and the first transducer is provided in the beam portion in the Y-axis direction. A third converter that converts a mechanical variation in the Z-axis direction different from the X-axis direction or the Y-axis direction into an electrical variation in the X-axis direction beam portion or the Y-axis direction beam portion. A converter is provided.

The first converter, the second converter, and the third converter each include at least two conversion elements, and the resistor includes at least seven resistance elements.
A first conversion element and a first resistance element constituting the first converter are connected in series, and in parallel therewith, a second conversion element and a second resistance element constituting the first converter, Are connected in series to form an X-axis bridge circuit,
A third conversion element and a third resistance element constituting the second converter are connected in series, and a fourth conversion element and a fourth resistance element constituting the second converter are connected in parallel with the third conversion element and the third resistance element, respectively. Are connected in series to form a Y-axis bridge circuit,
The fifth resistance element and the sixth resistance element are connected in series, and the fifth conversion element, the sixth conversion element, and the seventh resistance element constituting the third converter are connected in series with the fifth resistance element and the sixth resistance element. Connected to the Z-axis bridge circuit,
A physical quantity applied to the weight portion is detected using an X-axis bridge circuit, a Y-axis bridge circuit, and a Z-axis bridge circuit.

  The two conversion elements constituting the third converter have the same conversion characteristics.

The electrical converter of the present invention includes at least three converters and a resistor provided apart from each other.
In the electrical converter of the present invention, the converter and the resistor can be installed separately. For example, a converter can be provided in the beam portion, and a resistor can be provided in the other portion. By adopting such a configuration, it is not necessary to install an extra element or wiring in the beam portion, and the beam portion can be reduced in size. By reducing the number of converters and resistors provided in the beam portion, it is possible to reduce disconnection of wiring due to stress applied to the beam portion, and it is possible to configure a highly reliable electric converter.
In addition, the first transducer is provided in the beam portion in the X-axis direction, the second transducer is provided in the beam portion in the Y-axis direction, and the beam portion in the X-axis direction or the beam portion in the Y-axis direction is provided. Is provided with a third converter. Each of these converters consists of at least two conversion elements, and the resistor also consists of at least seven resistance elements. These conversion elements and resistors are combined to form a bridge circuit for the X axis, the Y axis, and the Z axis, and a physical quantity applied to the weight portion is detected. By adopting such a configuration, the number of transducers and resistors provided in a certain axial beam portion can be reduced, so that the shape of the beam portion can be further reduced. That is, since the beam portion can be miniaturized, there is an effect that the physical quantity can be detected with higher sensitivity to the movement of the weight portion.

According to the electric converter of the present invention, it is possible to mount a small, highly sensitive and highly reliable electric converter in a portable device that could not be achieved by the electric converter of the prior art.

  The configuration relating to the detection of the optimum structure and physical quantity of the electrical converter of the present invention will be described below with reference to the drawings. In the present embodiment, description will be given by taking acceleration as an example of the physical quantity.

[Description of converter arrangement: FIG. 1]
First, the configuration of the electromechanical converter of the present invention will be described.
FIG. 1A is a structural plan view of the electromechanical transducer of the present invention viewed from above, and FIG. 1B is a cross-sectional view thereof. In the example shown in FIG. 1, there is shown a configuration in which a weight portion is provided at substantially the center of the frame and the weight portion is supported by four beam portions. Moreover, the structure which provides a converter in a beam part and provides a resistor in a frame part is shown.
In FIG. 1, 1 is a frame portion, 2 is a wiring, 3 is a planar electrode, 4 is a conversion element, 5 is a beam portion, 6 is a weight portion, 7 is a protective film, and 20 is an electromechanical transducer. PX1, PX2, PY1, PY2, PZ1, and PZ2 are converters, and PX1 and PX2 form a first converter, and PY1 and PY2 form a second converter, and PZ1 and PZ2 Constitutes a third converter. PX1 is a first conversion element, and PX2 is a second conversion element. PY1 is a third conversion element, and PY2 is a fourth conversion element. PZ1 is a fifth conversion element, and PZ2 is a sixth conversion element. The conversion element 4 shown in FIG. 1B represents one of these first to sixth conversion elements. For example, the conversion element 4 provided on the beam portion 5 on the left side of the drawing is the first conversion element. The conversion element 4 provided on the beam portion 5 on the right side of the drawing PX1 can be defined as the second conversion element PX2.
RF1, RF2, RF3, RF4, RF5, RF6, and RF7 are resistors, RF1 is a first resistance element, and RF2 is a second resistance element. RF3 is a third resistance element, and RF4 is a fourth resistance element. RF5 is a fifth resistance element, RF6 is a sixth resistance element, and RF7 is a seventh resistance element.

  In FIG. 1A, the horizontal direction in the drawing is defined as the X axis and the vertical direction is defined as the Y axis. Further, the Z axis is defined in a direction perpendicular to the drawing (in FIG. 1B, the vertical direction of the drawing). Thereby, an XYZ three-dimensional coordinate system is defined.

  As shown in FIG. 1, the electromechanical transducer 20 of the present invention is provided with a weight portion 6 that is passively driven by acceleration substantially at the center of the frame portion 1. A flexible beam portion 5 is provided so as to connect the frame portion 1 and the weight portion 6. The weight portion 6 is supported by two beam portions 5 in the X-axis direction and the Y-axis direction, respectively. It is desirable that the beam portion 5 has a minimum cross-sectional area so as to support the weight portion 6 without hindering the movement of the weight portion 6. With such a configuration, even if the weight portion 6 is small or light, stress due to the operation is applied to the beam portion 5, and each transducer can receive the stress more effectively. is there.

  As a material of the frame part 1 and the weight part 6, for example, a silicon single crystal plate or a glass plate can be used. When such a material is used, the small electromechanical transducer 20 can be formed by known processing means such as a photolithography technique or anisotropic dry etching (RIE). Moreover, as a member of the beam part 5, silicon nitride, silicon oxide, a polyimide resin, an epoxy resin, etc. other than a silicon single crystal or glass can be used.

The electromechanical transducer 20 of the present invention is provided with a plurality of transducers on the upper surface of the beam portion 5. The installation location of the transducer in the beam portion 5 is preferably a portion where stress is strongly applied to the movement of the weight portion 6, for example, a connection portion between the frame portion 1 and the beam portion 5.
The converters PX1, PX2, PY1, PY2, PZ1, and PZ2 are conversion elements whose electrical characteristics change due to mechanical deformation, for example, piezoresistive elements whose resistance value changes under mechanical stress. Can be configured. These converters are arranged in a predetermined direction on the upper surface of the beam portion 5.

Although these converters will exhibit resistance change according to the bending deformation amount of the beam part 5, the conversion elements provided in the same axial direction have the same conversion characteristic. For example, the first conversion element PX1 and the second conversion element PX2 have the same conversion characteristics. Similarly, the third conversion element PY1, the fourth conversion element PY2, the fifth conversion element PZ1, and the sixth conversion element PZ2 have the same conversion characteristics.
The conversion characteristic of the conversion element is, for example, having the same change in resistance value when the same mechanical stress is applied. Specifically, means for making the conversion characteristics the same are widely known. For example, the same conversion characteristics can be easily obtained by making the impurity concentration of the resistor portion constituting the piezoresistive element, the formation size, and the size the same. Can be. Since such a technique is widely proposed, description thereof is omitted.

  Further, each conversion element is electrically connected to the planar electrode 3 via the wiring 2. The planar electrode 3 serves as a terminal for connecting the electromechanical transducer 20 of the present invention to an external device or the like, and corresponds to a pad in the case of a semiconductor device. As shown in FIG. 1B, a protective film 7 is provided on the upper surface of the electromechanical transducer 20 except for the portion of the planar electrode 3.

  The wiring 2 and the planar electrode 3 can be made of known metals such as aluminum, copper, and gold, or alloys thereof. The protective film 7 can be formed of a silicon nitride film, a polyimide resin film, or the like.

The electromechanical transducer 20 of the present invention shown in FIG. 1 is provided with resistors from the first resistance element RF1 to the seventh resistance element RF7 on the upper surface of the frame 1. If a silicon single crystal is used for the frame 1, a polysilicon resistor or a diffused resistor can be selectively formed at a predetermined location, and these can be used as a resistor. In that case, a known semiconductor manufacturing technique can be used.
These resistors do not necessarily have to be provided on the frame portion 1, and may be provided on a separate external substrate, for example.

Next, the arrangement of the converter will be described in more detail.
The first conversion element PX1 and the second conversion element PX2 are provided at the portion where the beam portion 5 and the frame portion 1 that extend in the X-axis direction are joined, and the bending of the beam portion 5 in the X-axis direction is converted into an electric signal. A first converter for conversion is configured.
Similarly, the third conversion element PY1 and the fourth conversion element PY2 are provided at a portion where the beam portion 5 and the frame portion 1 which are extended in the Y direction are joined, and the bending of the beam portion 5 in the Y axis direction is electrically A second converter is configured for conversion into a signal.
Furthermore, the first conversion element PX1 and the second conversion element described above are connected to a portion where the beam portion 5 and the frame portion 1 that span the fifth conversion element PZ1 and the sixth conversion element PZ2 in the X-axis direction are joined. A third converter is provided adjacent to PX2 for converting the deflection of the beam portion 5 in the Z-axis direction into an electric signal. The fifth conversion element PZ1 and the sixth conversion element PZ2, and the first conversion element PX1 and the second conversion element PX2 are provided separately from each other.

  Of course, the fifth conversion element PZ1 and the sixth conversion element PZ2 are the third conversion element PY1 and the fourth conversion element PY2 at the portion where the beam portion 5 and the frame portion 1 spanned in the Y-axis direction are joined. And may be provided adjacent to each other. That is, it may be provided in either the X-axis direction or the Y-axis direction.

[Description of Bridge Circuit: Fig. 2]
Moreover, in order to detect the mechanical deformation | transformation which concerns on this XYZ three-dimensional coordinate system, a bridge circuit is comprised using these conversion elements and resistors. This is shown in FIGS. 2 (a) to 2 (c). By configuring the bridge circuit, physical quantities such as acceleration, inclination, and vibration can be converted into voltage changes and detected.
The resistor can be provided on the frame portion 1 as shown in FIG. 1A, but may be provided on an external substrate. Further, the connection of the bridge circuit may be performed by providing a wiring on the frame portion 1 or may be performed on the external substrate via the planar electrode 3.

  As shown in FIG. 2, the first conversion element PX1 and the second conversion element PX2, the third conversion element PY1 and the fourth conversion element PY2, the fifth conversion element PZ1 and the sixth conversion element PZ2 Three sets of bridge circuits are configured by using six conversion elements and seven resistors of the first resistance element RF1 to the seventh resistance element RF7. Reference numerals 9a, 9b and 9c denote power sources, and 8a, 8b and 8c denote voltmeters. P1 to P6 are connection points.

  The bridge circuit shown in FIG. 2 shows three sets of bridge circuits in order to explain the three connection states. Of course, it is not always necessary to prepare three sets of bridge circuits. Although not shown, three sets of bridge circuits can be configured by switching converters and resistors using known wiring switching means. In that case, it is only necessary to prepare one each of the voltmeters 8a to 8c and the power supplies 9a to 9c.

  FIG. 2A shows an X-axis bridge circuit for detecting acceleration in the X-axis direction. The first conversion element PX1 and the first resistance element RF1 are connected in series, and the second conversion element PX2 and the second resistance element RF2 are connected in series with the first conversion element PX1 to form an X-axis bridge circuit. is doing. Further, a power source 9a is connected between the first conversion element PX1 and the second conversion element PX2 and between the first resistance element RF1 and the second resistance element RF2, and further, the first conversion element A voltmeter 8a is connected between the element PX1 and the first resistance element RF1 (connection point P1) and between the second conversion element PX2 and the second resistance element RF2 (connection point P2). . The voltmeter 8a measures a voltage Vx between the connection point P1 and the connection point P2.

  FIG. 2B is a Y-axis bridge circuit for detecting acceleration in the Y-axis direction. A third conversion element PY1 and a third resistance element RF3 are connected in series, and a fourth conversion element PY2 and a fourth resistance element RF4 are connected in series in parallel with this to constitute a Y-axis bridge circuit. is doing. Further, a power source 9b is connected between the third conversion element PY1 and the fourth conversion element PY2, and between the third resistance element RF3 and the fourth resistance element RF4, and further the third conversion element. A voltmeter 8b is connected between the element PY1 and the third resistance element RF3 (connection point P3) and between the fourth conversion element PY2 and the fourth resistance element RF4 (connection point P4). . The voltmeter 8b measures the voltage Vy between the connection point P3 and the connection point P4.

  FIG. 2C shows a Z-axis bridge circuit for detecting acceleration in the Z-axis direction. The fifth resistance element RF5 and the sixth resistance element RF6 are connected in series, and the fifth conversion element PZ1 and the sixth conversion element PZ2 are connected in series with the fifth resistance element RF5 and the sixth resistance element RF7. Both are connected in series to form a Z-axis bridge circuit. Further, a power source 9c is connected between the fifth resistor element RF5 and the fifth converter element PZ1, and between the sixth resistor element RF6 and the seventh resistor element RF7, and further, a fifth resistor A voltmeter 8c is connected between the element RF5 and the sixth resistance element RF6 (connection point P5) and between the sixth conversion element PZ2 and the seventh resistance element RF7 (connection point P6). . The voltmeter 8c measures the voltage Vz between the connection point P5 and the connection point P6.

When configuring the X-axis bridge circuit shown in FIG. 2A, for example, by selecting a conversion element and a resistance element having an appropriate resistance value, the equation 1 is established between the connection point P1 and the connection point P2. The voltage Vx, which is a potential difference between the connection point P1 and the connection point P2, can be set to zero.

  At this time, for example, if the first conversion element PX1 and the second conversion element PX2 are configured using piezoresistive elements whose resistance values change due to the stress applied thereto, the first conversion element PX1 and the first conversion element PX1 A difference in resistance value caused by stress between the two conversion elements PX2 can be detected as a potential difference between the connection point P1 and the connection point P2.

  When the Y-axis bridge circuit shown in FIG. 2B is configured, for example, by selecting a conversion element and a resistance element having an appropriate resistance value, the number 2 is set between the connection point P3 and the connection point P4. The voltage Vy, which is a potential difference between the connection point P3 and the connection point P4, can be set to zero.

  At this time, for example, if the third conversion element PY1 and the fourth conversion element PY2 are configured using piezoresistive elements whose resistance values change depending on the stress applied to each of the third conversion element PY1 and the fourth conversion element PY2, The difference in resistance value caused by the stress between the four conversion elements PY2 can be detected as a potential difference between the connection point P3 and the connection point P4.

  When configuring the Z-axis bridge circuit shown in FIG. 2C, for example, by selecting a conversion element and a resistance element having an appropriate resistance value, a number 3 is established between the connection point P5 and the connection point P6. The voltage Vz which is a potential difference between the connection point P5 and the connection point P6 can be set to zero.

At this time, for example, if the fifth conversion element PZ1 and the sixth conversion element PZ2 are configured using piezoresistive elements whose resistance values change due to the stress applied to each, the fifth conversion element PZ1 and the fifth conversion element PZ1 The difference in resistance value caused by the stress with the six conversion elements PZ2 can be detected as a potential difference between the connection point P5 and the connection point P6.

[Description of electromechanical conversion action: Fig. 3]
Next, the electromechanical conversion action in the configuration of the embodiment of the present invention will be described in detail. A description will be given by taking as an example the action when the acceleration in the three-axis direction is separated for each axis and converted into an electrical signal.

[Method of detecting acceleration in X-axis and Y-axis directions: FIGS. 2 and 3]
First, the operation when the acceleration in the X-axis direction is separated from the other axes and is electrically detected will be described.
FIG. 3 is a cross-sectional view schematically showing the structure of the electromechanical transducer of the present invention. FIG. 3A is an X-axis direction or a Y-axis direction parallel to the beam portion 5 (left of the drawing). 3B shows a case where acceleration in the Z-axis direction (from the top to the bottom of the drawing) perpendicular to the beam portion 5 is applied. In the figure, the arrow indicates acceleration.

As shown in FIG. 3A, when the weight portion 6 is passively driven by the acceleration in the X-axis direction, the deflection of the beam portion 5 arranged in the X-axis direction causes the conversion element 4 formed at the end portion to Stress acts. In FIG. 3A, the conversion element 4 provided on the beam portion 5 on the left side of the drawing is defined as a first conversion element PX1, and the conversion element 4 provided on the beam portion 5 on the right side of the drawing is defined as a second conversion element PX2.
As shown in FIG. 3A, when acceleration is applied in the X-axis direction, the first conversion element PX1 decreases in resistance value due to compressive stress, while the second conversion element PX2 increases in resistance value due to elongation stress. Will be presented. In the drawing, compressive stress is described as + stress, and elongation stress is described as-stress.
For this reason, the equilibrium relationship between the converters (PX1, PX2) and the resistors (RF1, RF2) in the X-axis bridge circuit shown in FIG. 2A is broken, and the potential difference between the connection point P1 and the connection point P2. The voltage Vx can be observed.

The same applies to the case where the weight portion 6 is passively driven by acceleration in the Y-axis direction that is 90 degrees perpendicular to the X-axis. If FIG. 3A is regarded as a view in which acceleration is applied in the Y-axis direction, in FIG. 3A, the conversion element 4 provided in the beam portion 5 on the left side of the drawing is the third conversion element PY1, and the beam on the right side of the drawing. The conversion element 4 provided in the part 5 can be defined as a fourth conversion element PY2.
As shown in FIG. 3A, when acceleration is applied in the Y-axis direction, the third conversion element PY1 decreases in resistance value due to compressive stress, while the fourth conversion element PY2 increases in resistance value due to elongation stress. Will be presented.
For this reason, the equilibrium relationship between the converters (PY1, PY2) and the resistors (RF3, RF4) in the Y-axis bridge circuit shown in FIG. 2B is broken, and the potential difference between the connection point P3 and the connection point P4. The voltage Vy can be observed.
Of course, the beam portion 5 arranged in the X-axis direction is not bent, and stress does not act on the transducers (PX1, PX2) formed at the end portions thereof. And no connection point P2.

Further, as shown in FIG. 3 (b), when the weight portion 6 is passively driven by the acceleration in the Z-axis direction from the top to the bottom of the drawing, the end portion thereof is bent by the bending of the beam portion 5 arranged in the X-axis direction. Stress acts on the conversion element 4 formed in the above. In FIG. 3B, the conversion element 4 provided in the beam part 5 on the left side of the drawing is defined as a first conversion element PX1, and the conversion element 4 provided on the beam part 5 on the right side of the drawing is defined as a second conversion element PX2.
In this case, in FIG. 3B, the first conversion element PX1 exhibits an increase in resistance value due to elongation stress, and similarly, the second conversion element PX2 also exhibits an increase in resistance value due to elongation stress.
Accordingly, the balanced relationship between the converters (PX1, PX2) and the resistors (RF1, F2) is maintained, and no potential difference is generated between the connection point P1 and the connection point P2.

As described above, according to the electromechanical transducer of the present invention, it is possible to configure an electromechanical transducer that detects the acceleration in the X-axis direction separately from the other axes and electrically detects the acceleration.
Also, the acceleration in the Y-axis direction that is 90 degrees perpendicular to the X-axis can be detected electrically by separating the acceleration in the Y-axis direction from the other axes by the same action as the X-axis direction. It becomes.

[Method of detecting acceleration in the Z-axis direction: FIGS. 2 and 3]
Next, an operation when the acceleration in the Z-axis direction is separated from the other axis and electrically detected will be described.
As described above, the two converters (PZ1, PZ2) for detecting the acceleration in the Z-axis direction apply the acceleration in the X-axis direction to the portion where the beam portion 5 and the frame portion 1 that are spanned in the X-axis direction are joined. A converter for converting the bending of the beam portion 5 in the Z-axis direction into an electric signal can be configured by being provided adjacent to the converters (PX1, PX2) to be detected.

As shown in FIG. 3A, when the weight portion 6 is passively driven by the acceleration in the X-axis direction, the deflection of the beam portion 5 arranged in the X-axis direction causes the conversion element 4 formed at the end portion to Stress acts. In FIG. 3A, the conversion element 4 provided in the beam part 5 on the left side of the drawing is defined as a fifth conversion element PZ1, and the conversion element 4 provided in the beam part 5 on the right side of the drawing is defined as a sixth conversion element PZ2.
As shown in FIG. 3A, when acceleration is applied in the X-axis direction, the fifth conversion element PZ1 decreases in resistance value due to compressive stress, while the sixth conversion element PZ2 increases in resistance value due to elongation stress. Will be presented.
For this reason, the balanced relationship between the converters (PZ1, PZ2) and the resistors (RF5, RF6, RF7) in the Z-axis bridge circuit shown in FIG. 2C is the same as that of the fifth conversion element RZ1 and the sixth conversion element. Since the change in resistance value with RZ2 is canceled by series connection (electrical addition), it is retained. Therefore, the voltage Vz that is a potential difference is not generated between the connection point P5 and the connection point P6.

When the weight portion 6 is passively driven by the acceleration in the Y-axis direction that is 90 degrees perpendicular to the X-axis, the beam portion 5 arranged in the X-axis direction is not bent and is formed at the end thereof. No stress acts on the transducers (PY1, PY2).
Therefore, the balanced relationship between the transducers (PZ1, PZ2) and the resistors (RF5, RF6, RF7) in the Z-axis bridge circuit shown in FIG. 2C is maintained, and the connection point P5 and the connection point P6 are There is no potential difference between them.

Further, as shown in FIG. 3 (b), when the weight portion 6 is passively driven by the acceleration in the Z-axis direction from the top to the bottom of the drawing, the end portion thereof is bent by the bending of the beam portion 5 arranged in the X-axis direction. Stress acts on the conversion element 4 formed in the above. In FIG. 3B, the conversion element 4 provided on the left beam portion 5 in the drawing is defined as a fifth conversion element PZ1, and the conversion element 4 provided on the right beam portion 5 in the drawing is defined as a sixth conversion element PZ2.
In this case, in FIG. 3B, the fifth conversion element PZ1 exhibits an increase in resistance value due to elongation stress, and similarly, the sixth conversion element PZ2 also exhibits an increase in resistance value due to elongation stress.
For this reason, the balanced relationship between the converters (PZ1, PZ2) and the resistors (RF5, RF6, RF7) in the Z-axis bridge circuit shown in FIG. 2C is the same as that of the fifth conversion element PZ1 and the sixth conversion element. Since the resistance value change with the element PZ2 increases due to series connection (electrical addition), it collapses. Therefore, the voltage Vz which is a potential difference between the connection point P5 and the connection point P6 can be observed.

As described above, according to the configuration of the present invention, not only the X-axis and Y-axis, but also the acceleration in the Z-axis direction can be electrically detected separately from the other axes.
Moreover, the converter is provided in the part which a beam part and a frame part contact | connect, and it is not necessary to provide a resistor in a beam part. For this reason, there is no need for extra wiring in the beam portion, the shape of the beam portion can be set freely, and there is no failure such as disconnection in the wiring of the beam portion. Therefore, a thin flexible part (beam) can also be formed.

  According to the electromechanical transducer of the present invention, the beam portion can be easily deformed even with a small and light weight. Therefore, the small size, high sensitivity, and high reliability that cannot be achieved by the conventional electromechanical transducer. It becomes possible to mount the electric converter on the portable device.

In the embodiment of the present invention, the example in which the conversion element for detecting the acceleration in the Z-axis direction is provided in the beam portion in the X-axis direction has been described. However, the present invention is not limited to this. A conversion element that detects acceleration in the Z-axis direction may be provided in the beam portion in the Y-axis direction.
Of course, the converter provided in a certain axial direction has been described by taking the case of using two conversion elements as an example, but this is not a limitation. In view of the shape of the beam portion, more conversion elements may be provided.

  The electromechanical transducer of the present invention can detect a three-dimensional acceleration component with one electromechanical transducer. Since it can be made smaller than before, it is suitable for portable electronic devices, robots, and the like that have a strong demand for miniaturization.

It is a figure for demonstrating the structure of the electromechanical converter of this invention. It is a figure explaining the bridge circuit in the electromechanical converter of this invention. It is sectional drawing for demonstrating the effect | action of the electromechanical converter of this invention. It is a figure for demonstrating the structure of the electromechanical converter of a prior art. It is a figure explaining the bridge circuit in the electromechanical converter of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Frame part 2 Wiring 3 Planar electrode 4 Conversion element 5 Beam part 6 Weight part 7 Protective film 8a, 8b, 8c Voltmeter 9a, 9b, 9c Power supply 20 Electromechanical converter PX1 1st conversion element PX2 2nd conversion element PY1 3rd conversion element PY2 4th conversion element PZ1 5th conversion element PZ2 6th conversion element RF1 1st resistance element RF2 2nd resistance element RF3 3rd resistance element RF4 4th resistance element RF5 4th 5 resistive element RF6 6th resistive element RF7 7th resistive element P1 to P6 Connection point

Claims (3)

Mechanical variation including a weight part, a frame part, a beam part in the X-axis direction connecting the weight part and the frame part, and a beam part in the Y-axis direction substantially orthogonal to the X-axis direction in a plane. An electromechanical transducer having a transducer for converting the electrical variation into electrical fluctuations,
A resistor spaced apart from the converter;
The transducer comprises at least three transducers;
The X-axis direction beam portion is provided with a first converter,
A second converter is provided in the beam portion in the Y-axis direction,
A third converter that converts mechanical fluctuations in the Z-axis direction different from the X-axis direction or the Y-axis direction into electrical fluctuations in the X-axis direction beam part or the Y-axis direction beam part. An electromechanical transducer characterized by being provided. Each of the first converter, the second converter, and the third converter includes at least two conversion elements,
The resistor comprises at least seven resistance elements,
A first conversion element and a first resistance element constituting the first converter are connected in series, and a second conversion element and a second resistance constituting the first converter are connected in parallel with the first conversion element and the first resistance element. Configure the X-axis bridge circuit by connecting the elements in series,
A third conversion element and a third resistance element constituting the second converter are connected in series, and a fourth conversion element and a fourth resistance constituting the second converter are connected in parallel with the third conversion element and the third resistance element. Connect the elements in series to form a Y-axis bridge circuit,
A fifth resistance element and a sixth resistance element are connected in series, and in parallel therewith, a fifth conversion element, a sixth conversion element, and a seventh resistance element constituting the third converter are provided. Connected in series to form a Z-axis bridge circuit,
The electromechanical transducer according to claim 1, wherein a physical quantity applied to the weight portion is detected using the X-axis bridge circuit, the Y-axis bridge circuit, and the Z-axis bridge circuit.   The electromechanical converter according to claim 2, wherein two conversion elements constituting the third converter have the same conversion characteristics.

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