JPH05205187A - Pulse oscillating element - Google Patents

Abstract

PURPOSE:To easily transduce mechanical motion into an electric signal by utilizing a piezoelectric element. CONSTITUTION:A leaf spring 1 which performs snap action is constituted by providing curved beams 1a and 1c at both sides of a straight beam 1b and the piezoelectric element 2 is adhered to the beam 1b. One end 1d of the leaf spring 1 is fixed and a force is applied to the other end 1e to deform the side of the piezoelectric element 2, and then the curved beams 1a and 1c are inverted in the process of the deformation, so that the deformation of the leaf spring 1 abruptly increases at the moment. Consequently, electric charges generated at both the sides of the piezoelectric element 2 owing to compressive straining abruptly rise, so they can be led out as a pulse signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse transmission element using a piezoelectric element, and more particularly to a pulse transmission element suitable for being incorporated in a switch mechanism.

[0002]

2. Description of the Related Art Conventional push button switches, micro switches, limit switches and the like have metal contacts, and the contacts are opened and closed by a mechanical displacement input to open and close an electrical circuit to detect the presence or absence of mechanical displacement. Have been communicated to. However, in a control panel or the like using a programmable controller, the input signal from the operation switch does not have to be continuous, and a pulse signal may be used in many cases. Therefore,
For such an application, an element that generates a pulse signal in response to an operation by an external force can be used as a switch instead of a conventional push button switch having a mechanical contact. On the other hand, it is known that a piezoelectric element generates an electric charge when an external force is applied, and by utilizing this phenomenon, it is possible to generate the pulse signal without supplying electric power from the outside.

[0003]

By the way, in order to obtain a pulse signal with the piezoelectric element, it is necessary to give it a momentary distortion. Therefore, when the pulse generating element is composed of the piezoelectric element alone, a separate mechanism for converting the slowly changing switch operating force into an impact force is required, and the overall structure is complicated and the manufacturing cost is high. Therefore, an object of the present invention is to provide a pulse transmission element capable of instantaneously deforming a piezoelectric element without converting an external force into an impact force and extracting a pulse voltage from the piezoelectric element with a simple configuration. Is.

[0004]

The present invention achieves the above object by forming a pulse transmission element by attaching a piezoelectric element to a part of a leaf spring having a snap action characteristic. Here, the snap action characteristic refers to a characteristic in which, when a load is applied to the leaf spring and gradually deformed, when the deformation reaches a certain point (snap action point), the ratio of the displacement to the load rapidly increases. It is a thing. A leaf spring having a snap action characteristic can be configured by connecting an arch-curved beam and a straight beam to each other at both ends. In that case, the piezoelectric element is attached to the beam on the straight side. At this time, the output voltage can be increased by stacking and sticking the piezoelectric elements.

[0005]

[Operation] When an external force is applied to the leaf spring to gradually deform it, the amount of deformation of the leaf spring sharply increases at the moment when the snap action point is reached, and the bending strain of the piezoelectric element attached to this is also shocked. Increase to. At that time, electric charges corresponding to the strain are generated in the piezoelectric element, and this is taken out as a pulse voltage to the outside.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. Example 1 FIG. 1 is a perspective view of a pulse transmission element. In the figure, 1
Is a leaf spring and has a structure in which three parallel beams 1a to 1c are connected to each other by connecting portions 1d and 1e at both ends thereof, and the central beam 1b is straight, while the beams on both sides thereof are straight. 1a and 1c are arched on the same side. Reference numeral 2 denotes a strip-shaped piezoelectric element, which is attached to the surface of the central beam 1b of the leaf spring 1 on the side where the beams 1a and 1c are curved by a conductive adhesive. The piezoelectric element 2 is polarized in the thickness direction, and electrodes are printed on both surfaces thereof. Three
Is a lead wire drawn from each electrode.

FIG. 2 shows a processing method for bending the beams 1a and 1c of the leaf spring 1, in which (A) is a plan view,
(B) is a side view. The leaf spring 1 remains a flat plate on the entire surface when punched from a plate material by a press. Next, the connection portion 4 at one end of each of the beams 1a and 1c with the connecting portion 1d is crushed by the punch 5 and plastically deformed so that the length of each of the beams 1a and 1c is longer than that of the beam 1b. This makes the beam 1
a and 1c are curved in an arch shape between the connecting portions 1d and 1e.

Now, as shown in FIG. 3, when one end 1d of the pulse transmission element of FIG. 1 is fixed and a load is applied to the other end 1e in the direction shown by an arrow to deform the whole to the piezoelectric element 2 side, The piezoelectric element 2 bonded integrally with the spring 1 causes compressive strain in each cross section, and as a result, charges are generated on the electrodes. 6
Is a discharge resistor for taking out the generated charge as a voltage, and 7 is a compression spring for applying a load. Hereinafter, a phenomenon when the pulse transmission element of FIG. 3 is deformed will be described with reference to FIG. Here, (A) of FIG. 4 shows the time change of the displacement of the load end 1e, (B) shows the time change of the load, and (C) shows the time change of the voltage across the discharge resistor 6, respectively.

In FIG. 4, when a load is applied and the displacement is gradually increased from zero, the load is gradually increased accordingly. During that time, the piezoelectric element 2 generates an electric charge, but if the discharge resistor 6 is appropriately selected, the generated electric charge is immediately discharged, so that a small voltage is detected. In the process of the displacement, the beams 1a and 1c are deformed into a wave shape so as to be gradually lifted upward in FIG. 3 opposite to the curved side. And time T ₁
When the snap action point is reached later, the beam is reversed in a stroke over the beam 1b to the position on the opposite side. Therefore, the load generated by the leaf spring 1 is rapidly reduced, but since the compression spring 7 stores a spring force commensurate with the load immediately before that, the displacement is displaced until the spring force and the load at that time are balanced. Increase sharply. As a result, a large compressive strain is momentarily generated in the piezoelectric element 2, and a pulse voltage appears in the discharge resistor 6.

Thereafter, the load increases as the displacement increases again until the time T ₂ elapses, but during that time, the electric charges are sequentially discharged, and the detected voltage becomes small. Time T ₂
After that, when the load is reduced this time, the snap action point is reached again after the time T ₃ , and the beams 1a and 1c are moved to the positions shown in FIG.
It reverses to the original position below and the load increases rapidly. This allows
The load end 1e rises sharply while compressing the compression spring 7, and the displacement sharply decreases. As a result, the compressive strain of the piezoelectric element 2 is instantaneously reduced, and a pulse voltage having the opposite polarity to that when the load is increased is generated. At that time, if there is a residual charge at the time of transmitting the positive pulse, the peak value becomes smaller accordingly. Then, when the load becomes zero after time T ₄ , the state returns to the original state of FIG.

According to experiments, a PZT piezoelectric element having a width of 3 mm, a length of 30 mm and a thickness of 0.3 mm is used, and this is bonded to a leaf spring of a phosphor bronze plate having a thickness of 0.3 mm to form a pulse transmitting element. It was manufactured and deformed by hand, and a signal with a peak voltage of 10 V and a rise time of 10 ms was obtained. At that time, the capacitance of the piezoelectric element is 15 nF and the discharge resistance is 1 MΩ. The fall time is determined by the CR time constant and the charge generated by the subsequent distortion.

FIG. 5 shows the deformation of the pulse transmission device of FIG. 1 in terms of the relationship between displacement and load.
When the amount of curvature of a and 1c is relatively small, (B) is relatively large. FIG. 4 shows the case where the amount of bending in (A) is small.
The load remains in the same direction even after the snap action point P ₁ is exceeded, which is a monostable type characteristic of automatically returning to the initial position P ₀ when the load is removed. In that case, the snap action point has hysteresis, and it is P ₁ point when the load increases, but P ₁ point when it decreases.
₂ points. On the other hand, when the amount of bending in (B) is large, the load reverses when the snap action point P ₁ is exceeded, and if the load is removed there, P on the side opposite to the initial position P ₀
It has a bistable characteristic that is stable at _three points. Also in this case, the snap action point has hysteresis, and becomes P ₁ point when the load increases and P ₂ point when the load decreases.

Embodiment 2 FIG. 6 shows an embodiment in which piezoelectric elements are laminated and adhered,
(A) is a plan view and (B) is a side view. In order to increase the amount of generated charges, two piezoelectric elements 2A and 2B are laminated and adhered, and piezoelectric elements 2A and 2B are attached as indicated by arrows in (B).
The polarization directions of are opposed to each other, and about twice the voltage is obtained by the lead wire 3a connected to the counter electrode and the lead wire 3b commonly connected to the electrodes on both sides. The number of stacked layers may be three or more.

Embodiment 3 FIG. 7 is a perspective view of an embodiment in which a terminal is provided on the pulse transmission device of FIG. 1, and FIG. 8 is an exploded view thereof. In the figure, leaf spring 1
Has one terminal 8 integrally formed on one side of the fixed end 1d,
The upper holder 10a and the lower holder 1 together with the other terminal 9
0b and the holder 10 are integrally held in an insulated state. The terminal 9 and the upper surface electrode of the piezoelectric element 2 are connected to the lead wire 3
Connected by. Reference numeral 11 is a mounting hole.

Embodiment 4 FIG. 9 is a perspective view of the essential portion of an embodiment in which the breakage of the lead wire is prevented. In the embodiment of FIG. 7, the lead wire 3 is deformed when the leaf spring 1 is deformed.
Also deforms at the same time, and if the number of repetitions is large, there is a risk of the lead wire 3 breaking due to fatigue. Therefore, in an application where the number of operations is large, as shown in FIG. 9, the connection point between the piezoelectric element 2 and the lead wire 3 is located inside the holder 10. As a result, even if the leaf spring 1 is deformed, the connecting point is not displaced, so that the lead wire 3 is not deformed.

Embodiment 5 FIG. 10 is a perspective view of an embodiment in which a plate spring having a curved beam on only one side is held by a holder, and FIG. 11 is an exploded view thereof. In the figure, the leaf spring 1 is provided with a curved beam 1a only on one side, and a lever 12 is integrally formed on the opposite side from the load end portion 1e obliquely upward. The terminal 8 of the leaf spring 1 is held by the holder 10 together with the terminal 9. The lower holder 10b also receives the load end 1e, and a mounting hole 11 is provided in the vicinity thereof. In the illustrated configuration, when the lever 12 is downwardly displaced, the curved beam 1a
The bending moment M is applied to the tip of the curved beam 1a at the snap action point and the load end 1e is lifted. As a result, the beam 1b to which the piezoelectric element 2 is attached bends, and the voltage generated between the electrodes of the piezoelectric element 2 is taken out from the terminals 8 and 9.

FIG. 12 shows a process of continuously manufacturing the pulse transmission device of FIG. In step I, the leaf spring 1 and the terminal 9 are punched out, leaving the connecting portion 13a from the plate material 13,
In step II, the holder 10 is molded and then the connecting portion 13a is cut off. Next, in step III, the piezoelectric element 2 is attached to the beam 1b,
Further, in step IV, the snap action processing of the beam 1a and the bending processing of the lever 12 are performed. Finally, in step V, lead wire 3
Is completed by soldering.

Embodiment 6 FIG. 13 shows an embodiment in which an anchor is used to form a curved beam. That is, in the figure, the beams 1a and 1c on both sides of the leaf spring 1 are separated from the fixed end portion 1d, and the tip end is pushed by the anchor 14 to be curved.
The anchor 14 is fixed to the leaf spring 1 with a rivet 15, and the cut ends of the beams 1a and 1c are V-shaped at the tip of the anchor 14.
It is fitted in the groove. FIG. 14 is a diagram for explaining the operation of the pulse transmission element of FIG. Before the operation (A), the anchor 14 is slightly above the load end 1e, and the load end 1e is pressed against the lower stopper 16 due to the balance of the forces with the curved beams 1a and 1c. Here, when the external force F acts on the load end 1e, the balance of the forces is reversed, and (B)
As shown in FIG. 3, the anchor 13 rapidly pushes up the leaf spring 1 to cause a snap action. The amount of deformation of the leaf spring 1 is restricted by the load end 1e hitting the upper stopper 17 before the piezoelectric element 2 is excessively bent. In this configuration, snap action characteristics can be obtained even if the curved beams 1a and 1c are not inverted, so that the mechanical life of the leaf spring 1 becomes longer than when the anchor 13 is not used.

Embodiment 7 FIG. 15 shows a contactless load switching circuit using the pulse transmitting element of the present invention. Since the piezoelectric element 2 is a charge-generating element, it cannot drive an electromagnetic relay or the like and can generate signals only in pulses. Therefore, the circuit shown in FIG. 15 applies generated charges to the FET 18 which can be driven by voltage, and the switching action thereof allows the ON or OFF state to be continued for some time. Reference numeral 19 is a load, and 20 is a power supply. However, the electric charge of the piezoelectric element 2 may remain even if the deformation is returned to the original state, and the electric charge may be generated even if it is not deformed due to the temperature rise (pyroelectric effect). In order to prevent this, when there is no deformation in the figure, the gate and drain of the FET 18 are short-circuited by the discharge switch 21 to discharge the residual charge. When using an FET that is destroyed by a reverse voltage, a protection diode 22 is connected as shown in the figure.

FIG. 16 shows the pulse transmission device of FIG.
2 shows a configuration example of the discharge switch 21 when used in the circuit of FIG. In the figure, a discharge switch 23 is provided by providing a discharge contact 23 which comes into contact with the operating end 1e of the leaf spring 1 in a non-operating state, and leads the terminal 9 connected to the upper surface electrode of the piezoelectric element 2 and the discharge contact 23. It is connected by a line 24. The terminals 8 and 9 are connected to the gate and drain of the FET 18, respectively. As a result, in the inoperative state shown in the figure, the residual charge of the piezoelectric element 2 is discharged through the discharge switch 21, while when the leaf spring 1 is deformed by the operation of the lever 12, the discharge switch 21 opens and the charge is accumulated in the piezoelectric element 2. When it reaches the snap action point, FET1
8 turns on.

Embodiment 8 FIG. 17 shows an embodiment in which the pulse transmission element, the FET 18 and the discharge contact 23 of FIG. 10 are housed in a case consisting of a base 25a and a cover 25b to form a contactless micro switch. The pulse generator, the FET 18, and the discharge contact 23 are attached to the holders 10a and 10b, and the base 25 is attached.
It is stored in a and covered with a cover 25b. 18a, 18b and 18c are the gate, drain and source terminals of the FET 18, respectively. The external force is transmitted to the lever 12 via the pin plunger 26. The individual parts are assembled by gluing, screwing, fitting, etc. The piezoelectric element 2 and the FET 18 are internally connected, and the drain terminal 18b of the FET 18 is externally connected.
Then, only the source terminal 18c is projected.

As described above, the pulse transmitting element of the illustrated embodiment has the straight beam 1 of the leaf spring 1 having the snap action characteristic by the arch-shaped curved beams 1a and 1c.
The piezoelectric element 2 is bonded to b, and the piezoelectric element 2 is applied by an external force that gently changes due to the snap action of the leaf spring 1.
A pulse signal can be obtained by applying an instantaneous distortion to. In the illustrated embodiment, if the beams 1a and 1c of the leaf spring 1 are made to have different bending amounts, a two-step snap action operation is performed, and two pulse signals can be obtained with one stroke. Further, only one curved beam may be used, or three or more curved beams may be used and the snap action points may be changed.

[0023]

According to the present invention, since the piezoelectric element is attached to a part of the leaf spring having the snap action characteristic to form the pulse transmission element, the advantage of the piezoelectric element that an external power source is unnecessary is provided. While utilizing it, mechanical movements can be easily converted into electric signals, and, for example, pulse transmission type push button switches, limit switches, micro switches, etc. can be manufactured at low cost. Further, it is also possible to manufacture a contactless switch capable of opening and closing a load by combining with a FET or the like.

[Brief description of drawings]

FIG. 1 is a perspective view of a first embodiment of the present invention.

2 (A) is a plan view and FIG. 2 (B) is a side view of the method for processing the leaf spring in FIG.

FIG. 3 is a side view showing a mounting state when the pulse transmission element of FIG. 1 is operated.

4 is a diagram showing a situation when the pulse transmission element of FIG. 3 is deformed, (A) is a diagram showing a relationship between time and displacement,
(B) is a figure which shows the relationship between time and a load, (C) is a figure which shows the relationship between time and voltage.

5A and 5B are diagrams showing the relationship between displacement and load when the pulse transmission element of FIG. 1 is deformed, where FIG. 5A shows the case where the curved amount of the curved beam is relatively small, and FIG. is there.

FIG. 6 shows a second embodiment of the present invention (A) is a plan view,
(B) is a side view thereof.

FIG. 7 is a perspective view showing a third embodiment of the present invention.

FIG. 8 is an exploded view of FIG. 7.

FIG. 9 is a perspective view of essential parts showing Embodiment 4 of the present invention.

FIG. 10 is a perspective view showing a fifth embodiment of the present invention.

FIG. 11 is an exploded view of FIG.

12 is a diagram showing a manufacturing process of the pulse transmission device of FIG.

FIG. 13 is a perspective view showing Embodiment 6 of the present invention.

14 is a diagram showing the operation of the pulse transmission device of FIG.
(A) is a state before the operation, and (B) is a state after the operation.

FIG. 15 is a circuit diagram showing Embodiment 7 of the present invention.

16 is a side view showing the configuration of the discharge switch in FIG.

FIG. 17 is an exploded perspective view showing an eighth embodiment of the present invention.

[Explanation of symbols]

 1 leaf spring 1a curved beam 1b straight beam 1c curved beam 2 piezoelectric element

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shunsai Machida 1-1, Tanabe Shinden, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd. (72) Inventor Yukinori Kawamura 1 Tanabe, Shinagawa, Kawasaki-ku, Kanagawa No. 1 in Fuji Electric Co., Ltd. (72) Inventor Hideo Kume 1-1 No. Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd.

Claims (3)

[Claims] 1. A pulse transmission element comprising a piezoelectric element attached to a part of a leaf spring having a snap action characteristic. 2. The pulse transmitting element according to claim 1, wherein a piezoelectric element is attached to the straight beam of the leaf spring in which the arch-shaped curved beam and the straight beam are connected to each other at both ends. 3. The pulse transmission element according to claim 1, wherein the piezoelectric elements are laminated and adhered.