JP2004037181A - Vibration sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vibration sensor capable of reducing a manufacturing cost and having stable quality. <P>SOLUTION: This vibration sensor 10 has a piezoelectric element 11. Electrodes are formed on both surfaces 11A and 11B of the piezoelectric element 11, of which the one end is a free end, and the other end is a fixed end. A support member 12 for supporting the piezoelectric element 11 is mounted on the surface 11B in the vicinity of the fixed end of the piezoelectric element 11. Electronic components and the support member 12 are fixed to an element board 15. The electrode on the surface 11A of the piezoelectric element 11 is electrically connected to the electrode on the element board 15 or the electrodes of the electronic components through a connection member 13. In particular, the connection member 13, the electrode on the surface 11A, the support member 12 and the electrode on the surface 11B are fixed by an adhesive. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a vibration sensor that detects vibration, and more particularly, to a configuration of a vibration sensor that is a functional electronic component used in an electronic device, a precision machine system, or the like.
[0002]
[Prior art]
FIG. 1 shows a basic structure of a conventional vibration sensor. As shown in FIG. 1, a conventional vibration sensor 9 includes a piezoelectric element 1, a support member 2, a wire 3, a field effect transistor 4, an element substrate 5, and shield cases 6A and 6B.
[0003]
Among them, the piezoelectric element 1 is made of a piezoelectric ceramic material such as PZT, and electrodes are formed on both surfaces, 1A surface and 1B surface. One end of the piezoelectric element 1 is a free end that freely moves by an external force, and the other end is a fixed end fixed to the element substrate 5 via the support member 2. The support member 2 is a member that supports the piezoelectric element 1. The wire 3 electrically connects one electrode 1 </ b> A of the piezoelectric element 1 to the gate of the field effect transistor 4. The field effect transistor 4 performs impedance conversion, amplification, and the like. The element substrate 5 fixes these components and the like, and a circuit pattern is formed on the surface thereof. The shield cases 6A and 6B electromagnetically cover the entire element substrate 5.
[0004]
Here, the support member 2 is made of copper or another conductive material. Therefore, the electrode 1B of the piezoelectric element 1 and the source of the field effect transistor 4 are electrically connected via the circuit pattern of the element substrate. With such a configuration, the circuit configuration can be simplified.
[0005]
[Problems to be solved by the invention]
In the structure of the conventional vibration sensor 9 shown in FIG. 1, solder is used for fixing the electrode 1A to the wire 3 and fixing the electrode 1B to the support member 2. The fixing method using solder can achieve both mechanical fixing and electrical connection, and is extremely reasonable in structure. However, low-temperature solder has been used for fixing the electrode 1A and the wire 3 and for fixing the electrode 1B and the support member 2 to secure the physical characteristics of the piezoelectric element 1.
[0006]
The fixing method using the low-temperature solder requires strict temperature control, and has a large problem in production such as an occasional problem in yield.
[0007]
The present invention has been made to solve such a problem, and an object of the present invention is to provide a vibration sensor that can reduce manufacturing cost and has stable quality.
[0008]
[Means for Solving the Problems]
A vibration sensor according to the present invention includes a piezoelectric element having electrodes formed on a first surface and a second surface, one end of which is a free end, and the other end of which is a fixed end, and a vicinity of a fixed end of the piezoelectric element. A support member for supporting the piezoelectric element on the second surface, an electrode formed with electrodes, and an element substrate for fixing the electronic component and the support member; an electrode on the first surface; and an electrode on the element substrate Alternatively, a connection member for electrically connecting an electrode of the electronic component is provided, and the connection member and the electrode on the first surface are fixed by an adhesive. With such a configuration, manufacturing cost can be reduced and stable quality can be ensured.
[0009]
Further, another vibration sensor according to the present invention includes a piezoelectric element having electrodes formed on a first surface and a second surface, one end of which is a free end, and the other end of which is a fixed end; A support member having conductivity and supporting the piezoelectric element on a second surface near a fixed end of the device, an element substrate on which electrodes are formed, and an electronic component and the support member are fixed; A connection member is provided for electrically connecting the electrode to an electrode on the element substrate or an electrode of an electronic component, and the connection member and the support member are fixed by an adhesive. Even with such a configuration, the manufacturing cost can be reduced and stable quality can be ensured.
[0010]
It is preferable that the piezoelectric element is configured with an electrode material without flattening the surface of the fired piezoelectric element. As a result, the adhesive penetrates into the space created in the connection portion, so that it is mechanically and firmly fixed, and at the same time, the electrical connection is kept stable.
[0011]
The adhesive is preferably a conductive adhesive. As a result, it is possible to particularly secure the electrical connection.
[0012]
Another vibration sensor according to the present invention includes a piezoelectric element having electrodes formed on a first surface and a second surface, one end of which is a free end, and the other end of which is a fixed end; A supporting member for supporting the piezoelectric element on a second surface near an end, an electrode formed with electrodes, and an element substrate for fixing an electronic component and the supporting member; an electrode on the first surface; A connection member for electrically connecting the electrode or the electrode of the electronic component, and the connection member is connected to the electrode by urging the electrode on the first surface so as to press the electrode. is there. With such a configuration, manufacturing cost can be reduced and stable quality can be ensured.
[0013]
Here, it is preferable to further include a fixing auxiliary member for fixing the connection member to the element substrate. With such a configuration, the connection member can be firmly fixed to the element substrate, and electrical connection between the connection member and the piezoelectric element can be ensured.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the drawings.
[0015]
FIG. 2 is a sectional view showing the vibration sensor 10 of the present invention. As shown in FIG. 2, the vibration sensor 10 of the present invention includes a piezoelectric element 11, a support member 12, a connection member 13, a field-effect transistor 14, an element substrate 15, and shield cases 16A and 16B. .
[0016]
Among them, the piezoelectric element 11 is made of a piezoelectric ceramic material such as PZT, and electrodes are formed on the entire surface of both surfaces 11A and 11B. One end of the piezoelectric element 11 is a free end that freely moves by an external force, and the other end is a fixed end fixed to the element substrate 15 via the support member 12. The support member 12 is a member that supports the piezoelectric element 11.
[0017]
The connection member 13 is a member for electrically connecting one electrode 11A of the piezoelectric element 11 and the gate of the field-effect transistor 14. The connection member 13 is made of, for example, a brass thin metal plate. Further, the connection member is bent at two places and is constituted by three flat plate portions. The first flat plate portion contacts the surface 11 </ b> A of the piezoelectric element 11. The width (width in the left-right direction in FIG. 2) of the first flat plate portion in contact with the surface 11A of the piezoelectric element 11 is substantially the same as the width of the support member 2. The second flat portion is substantially perpendicular to the first flat portion. The third flat plate portion is bent in a direction opposite to the bending direction of the first flat plate portion and the second flat plate portion. The second flat plate portion and the third flat plate portion are substantially perpendicular. The third flat portion is parallel to the main plane of the element substrate 15 and is in contact with the main plane. One end of the connection member 13 is fixed to the element substrate 15 by a fixing auxiliary member 13A. Here, the fixing auxiliary member 13A is, for example, a rivet. More specifically, the fixing auxiliary member 13A passes through the through hole provided in the third flat plate portion and the element substrate 15 described above. The auxiliary fixing member 13A is configured such that the diameters at both ends thereof are longer than the diameter of the through hole. Thereby, the connection member 13 is securely fixed to the element substrate 15.
[0018]
In this example, the connecting member 13 is fixed to the element substrate 15 by the fixing auxiliary member 13A. However, the present invention is not limited to this, and the connecting member 13 may be fixed to the element substrate 15 only by an adhesive.
[0019]
The field effect transistor 14 performs impedance conversion, amplification, and the like. The element substrate 15 is for fixing electronic components such as the support member 12 and the field effect transistor 14, and has a circuit pattern formed on the surface thereof. The shield cases 16A and 16B electromagnetically cover the entire element substrate 5.
[0020]
The support member 12 is formed using copper or another conductive material. Therefore, the electrode 11B of the piezoelectric element 11 and the source of the field effect transistor 14 are electrically connected via the circuit pattern (electrode) of the element substrate 15. With such a configuration, the circuit configuration of the piezoelectric element 11 can be simplified. Note that the support member 12 does not need to have conductivity as a whole, and may have only a portion of conductivity as long as the conductivity between the electrode 11B and the circuit pattern of the element substrate 15 can be ensured. .
[0021]
Next, the configuration of the piezoelectric element 11 will be described in detail. The electrodes 11A and 11B of the piezoelectric element 11 according to the present invention are formed by directly applying the electrode material 112 to the surface of the as-fired piezoelectric element material 111, and are fixed to the connection member 13 and the support member 12, respectively. Electrically connected.
[0022]
FIG. 3 shows a cross section near the surface of the piezoelectric element material 111. As shown in this figure, the surface of the as-fired piezoelectric element material 111 is in a rough state, and has many peaks (peaks). Conventionally, the surface of the piezoelectric element material 111 was flattened by polishing or the like in order to ensure coating properties of the electrodes. However, in the first embodiment of the present invention, the surface of the piezoelectric element material 111 is not flattened. The electrode material 112 is directly applied to this surface in a rough state. The electrode material 112 is, for example, silver powder. The surface of the electrode 11A after the application of the electrode material 112 inherits the surface roughness caused by firing. That is, the surface of the electrode 11A is in a rough state.
[0023]
Next, the connecting member 13 is brought into contact with the surface of the electrode 11A with a predetermined force. As shown in FIG. 4, the peak (peak) of the roughness of the electrode 11 makes strong contact with the flat portion of the connection member 13. At this time, the contact between the two occurs through the peak of the surface of the electrode 11A and the entire opposing surface of the connection member 13, and both are electrically and strongly stable. In addition, when the predetermined contact force cannot be stably ensured only by manufacturing jigs and tools, it is reasonable to use the fixing auxiliary member 13A shown in FIG. 2 together.
[0024]
By fixing both with an adhesive in a state where the contact shown in FIG. 4 is secured, electrical contact and mechanical fixation can be surely secured. As the adhesive, for example, an epoxy resin is used. As shown in FIG. 5, it is preferable that the adhesive 113 penetrates into the space between the valley of the roughness of the electrode surface 11 </ b> A and the connection member 13 and is cured. Thereby, the electrode surface 11A and the connection member 13 are mechanically firmly and securely fixed, and the electrical connection is maintained stably.
[0025]
As described above, the fixation and the electrical connection between the electrode 11A and the connection member 13 have been described. However, the secure fixation and the electrical connection can be similarly obtained between the electrode 11B and the support member 12. Also, the connection between the connection member 13 and the gate of the field effect transistor 14 may be fixed by an adhesive. When the connection between the connection member 13 and the gate of the field-effect transistor 14 is performed via an electrode on the element substrate 5, the connection member 13 and the electrode on the element substrate 5 are fixed with an adhesive. It may be.
[0026]
In addition, when the contact area between the electrode surface and the connecting member is small, the flatness of the two is good and the electrical contact cannot be obtained unless a large contact force is used. If not, a conductive adhesive may be used in place of the adhesive to stabilize the electrical connection, ensuring mechanical fixation and electrical connection. In this case, as shown in FIG. 6, the conductive particles 114A in the conductive adhesive 114 are filled between the electrode 11A and the connection member 13, and the conductive particles 114A are electrically connected between the electrode 11A and the connection member 13. Bridge and secure stable electrical connection. Here, as the conductive adhesive, for example, an adhesive obtained by mixing gold or silver powder with an epoxy resin or the like is used. Although the above-described example of the use of the conductive adhesive in the case of bonding the electrode 11A and the connection member 13 has been described, the same operation is performed even when the electrode 11B and the support member 12 are applied, and the description is omitted. Also, the connection between the connection member 13 and the gate of the field effect transistor 14 may be fixed by a conductive adhesive. When the connection between the connection member 13 and the gate of the field effect transistor 14 is performed via an electrode on the element substrate 5, the connection member 13 and the electrode on the element substrate 5 are fixed with a conductive adhesive. You may make it.
[0027]
Next, the operation of the vibration sensor 10 of the present invention will be described in detail with reference to FIG.
[0028]
When a device equipped with the vibration sensor 10 of the present invention receives a drop or a shock, a pulse-like force accompanying the shock is transmitted to the vibration sensor 10. The force accompanying this impact is first transmitted to the cases 16A and 16B shown in FIG. 2, and propagates through the cases 16A and 16B. For example, when a vertical force is applied from the outside to the position indicated by the arrow B, the force propagates through the case 16A, and at the same time, is transmitted to the element substrate 15 which is in close contact with the case 16A. The light is transmitted to the fixed end 11 </ b> C of the piezoelectric element 11 via the reference numeral 12. At this time, the other end 11D of the piezoelectric element 11 is a free end to which no force is directly applied from the outside, and follows the gravity. In this state, when the fixed end 11C of the piezoelectric element 11 receives a pulse-like external force shown by an arrow B, the piezoelectric element 11 changes from a state before receiving the external force (shown by a broken line) to a solid line as shown in FIG. Transition to the state indicated by. That is, the fixed end 11C of the piezoelectric element 11 is lifted, and the free end maintains its position as indicated by the law of inertia. Therefore, the piezoelectric element 11 is distorted in an upwardly convex state, and a potential corresponding to the distortion appears on the electrodes 11A and 11B. Then, the bending energy caused by the distortion and the internal rigidity which is the restoration energy of the piezoelectric element 11 are balanced, and the distortion of the piezoelectric element 11 is released over time, and returns to the original state.
[0029]
Next, when the external force disappears, the vibration sensor 10 is released from the position regulated by the external force, and returns to the original state or the unregulated state. At this time, the piezoelectric element 11 performs a movement opposite to the above-described movement.
[0030]
As shown in FIG. 8, the piezoelectric element 11 is released from the pulse-like external force, and shifts from a state in which the distortion is released by the external force (shown by a broken line) to a state shown by a solid line in which the external force is released. That is, with the release of the external force, the fixed end 11C of the piezoelectric element 11 returns to its original position (downward in the drawing), and the free end maintains its position as shown by the law of inertia. Therefore, the piezoelectric element 11 is distorted in an upwardly concave state, and a potential corresponding to the distortion appears on the electrodes 11A and 11B.
[0031]
Then, the distortion of the piezoelectric element 11 is released over time due to the balance between the bending energy due to the distortion and the internal rigidity, which is the restoration energy of the piezoelectric element 11, and the piezoelectric element 11 returns to the original state.
[0032]
When an external force is applied as vibration, the behavior is determined by the balance between the vibration frequency and the restoration energy of the piezoelectric element 11.
[0033]
The potential appearing at the electrodes 11A and 11B is transmitted to the gate and the source of the field-effect transistor 14 via the connection member 13 connected to the electrode 11A and the support member 12 connected to the electrode 11B.
[0034]
The potential generated at the electrode 11A is transmitted to the gate of the field-effect transistor 54 through the connected connecting member 53, and the potential generated at the electrode 11B is transmitted through the pattern of the supporting member 12 and the element substrate 15. , To the source of the field effect transistor 14.
[0035]
The field effect transistor 14 performs impedance conversion, amplification, and the like on the transmitted signal, and outputs the signal to its output terminal. This output is transmitted to the outside as an output signal of the vibration sensor 10 via a signal line of the cable 17 to be connected.
[0036]
At this time, the vibration sensor 10 covers the entire element substrate 15 on which the piezoelectric element 11, the support member 12, the connection member 13, and the various components are mounted by the shield cases 16A and 16B, and is electromagnetically shielded. Therefore, the vibration sensor 10 is hardly affected by surrounding electric noise and the like, and a high-quality detection signal can be obtained.
[0037]
As described above, in the vibration sensor according to the embodiment of the present invention, the member connected to the electrode is brought into contact with a predetermined force, and in a state where the mutual position is secured in this contact state, the adhesive or the adhesive is used. A conductive adhesive is used to fix and hold to obtain mechanical fixing and electrical connection.
[0038]
By adopting this fixing and connecting method, the vibration sensor can be processed in the surface state of firing and the manufacturing process is simplified, and the strict temperature in the manufacturing process is compared with the conventional soldering method. There is no need for management, and there are advantages in manufacturing, such as reduction in manufacturing variations. As a result, a secondary effect is obtained in which low-priced, stable quality products can be supplied to users.
[0039]
In the above-described example, the example in which the connection between the electrode 11A and the connection member 13 is performed using an adhesive has been described. However, the present invention is not limited to this, and the connection member 13 may be connected by the urging force of the connection member 13. The connection member 13 in this case is made of a metal flat plate or the like, and has a certain elastic force. Then, the connection member 13 is urged by the elastic force so as to press the electrode 11A.
[0040]
【The invention's effect】
According to the present invention, it is possible to reduce the manufacturing cost and to provide a vibration sensor having stable quality.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a conventional vibration sensor.
FIG. 2 is a sectional view showing a vibration sensor according to the present invention.
FIG. 3 is a sectional view showing a surface state of an electrode of a piezoelectric element in the vibration sensor according to the present invention.
FIG. 4 is a cross-sectional view showing a contact state between a piezoelectric element electrode 11A and a connection member 13 according to the present invention.
FIG. 5 is a cross-sectional view showing a state of contact between a piezoelectric element electrode 11A and a connection member 13 and a state of an adhesive according to the present invention.
FIG. 6 is a cross-sectional view showing a bonding state in which the piezoelectric element electrode 11A and the connection member 13 of the present invention are fixed using a conductive adhesive 114.
FIG. 7 is a cross-sectional view illustrating a state in which the piezoelectric element is distorted by an external force.
FIG. 8 is a sectional view showing a state of the piezoelectric element at the moment when the external force is released.
[Explanation of symbols]
1: piezoelectric element 1A, 1B: electrode 2: support member 3: wire 4: field effect transistor 5: element substrate 6A, 6B: shield case 7: cable 10: vibration sensor 11 of the present invention: piezoelectric element 11A: piezoelectric element Electrode 11B: Electrode of piezoelectric element 11C: Fixed end 11D of piezoelectric element: Free end 12 of piezoelectric element: Support member 13: Connection member 13A: Fixing auxiliary member 14: Field effect transistor 15: Element substrates 16A, 16B: Shield Case 17: Cable 111: Piezoelectric element material 112: Electrode material 113: Adhesive 114: Conductive adhesive 114A: Conductive particles

Claims (6)

A piezoelectric element having electrodes formed on the first surface and the second surface, one end being a free end, and the other end being a fixed end;
A support member for supporting the piezoelectric element on a second surface near the fixed end of the piezoelectric element;
Electrodes are formed, an element substrate for fixing the electronic component and the support member,
A connection member that electrically connects the electrode on the first surface and an electrode on the element substrate or an electrode of an electronic component;
A vibration sensor in which the connection member and the electrode on the first surface are fixed with an adhesive. A piezoelectric element having electrodes formed on the first surface and the second surface, one end being a free end, and the other end being a fixed end;
A supporting member having conductivity, supporting the piezoelectric element on a second surface near the fixed end of the piezoelectric element,
Electrodes are formed, an element substrate for fixing the electronic component and the support member,
A connection member that electrically connects the electrode on the first surface and an electrode on the element substrate or an electrode of an electronic component;
A vibration sensor in which the connection member and the support member are fixed with an adhesive. The vibration sensor according to claim 1, wherein the piezoelectric element includes an electrode material without flattening a surface of the fired piezoelectric element. The vibration sensor according to claim 1, 2 or 3, wherein the adhesive is a conductive adhesive. A piezoelectric element having electrodes formed on the first surface and the second surface, one end being a free end, and the other end being a fixed end;
A support member for supporting the piezoelectric element on a second surface near the fixed end of the piezoelectric element;
Electrodes are formed, an element substrate for fixing the electronic component and the support member,
A connection member that electrically connects the electrode on the first surface and an electrode on the element substrate or an electrode of an electronic component;
A vibration sensor in which the connection member is connected to the electrode on the first surface by urging the electrode to press the electrode on the first surface. The vibration sensor according to claim 5, further comprising a fixing auxiliary member for fixing the connection member to the element substrate.

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