JPH0528653Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an object detection device suitable for use in an object placement member such as an electric carpet. The apparatus includes a ribbon-shaped piezoelectric film on which electrodes are formed by metal vapor deposition, and an object placement member on which the ribbon-shaped piezoelectric film is arranged in a meandering manner and on which the object is placed, and the object is placed on the object placement member. The present invention relates to an object detection device in which the piezoelectric film generates a voltage due to the pressure of a placed object, and the generated voltage detects the placement of the object.

<Prior Art> An example in which a conventional object detection device is used in an electric carpet will be explained.

The conventional electric carpet, as shown in Figure 6,
A piezoelectric film 21 is disposed in a meandering manner between an upper mat 23 and a lower mat 24 forming an electric carpet body 22 which is an object placement member, and a heating element (not shown) is disposed on the electric carpet body 22. The structure is such that the presence of a person on the electric carpet main body 22 is detected by the voltage generated by the piezoelectric film 21, and the heating element is controlled to be energized.

Incidentally, reference numeral 26 denotes an operation section containing a built-in energization control section for controlling energization of the heating element, and is provided at a corner of the electric carpet main body 22.

<Problem to be solved by the invention> The piezoelectric film described above is made by forming electrodes on both sides of a plastic film made of polyvinylidene fluoride, polyvinylidene polycyanide, etc. into a thin film (thickness of 30 μm or less) by metal vapor deposition. It is formed by polarizing a plastic film by applying a high voltage between the piezoelectric films, and when it is arranged in a meandering manner on the electric carpet body, the piezoelectric film is bent at the meandering part, so the electrodes of the piezoelectric film may peel off. However, there was a drawback that the piezoelectric film cracked.

The object of the present invention is to provide an object detection device for use in electric carpets, etc., which eliminates the above-mentioned drawbacks.

<Means for Solving the Problems> In order to achieve the above object, the object detection device of the present invention uses a ribbon-shaped piezoelectric film with electrodes formed by metal vapor deposition on both sides, which generates a voltage when pressure is applied by an object. and an object placement member on which the ribbon-shaped piezoelectric film is arranged in a meandering manner and on which the object is placed, and the piezoelectric film receives a voltage due to the pressure of the object placed on the object placement member. In an object detection device that generates a voltage and detects the placement of an object using the generated voltage, the piezoelectric film is arranged in a meandering manner on the object placement member to prevent damage to the piezoelectric film when it is bent. A bent body having an outer circumferential surface with a predetermined radius of They are arranged in a meandering manner on the object mounting member.

<Operation> In the object detection device having the above configuration, when an object is placed on the object placement member, the piezoelectric film provided on the object placement member generates a voltage, and this generated voltage causes the object to be placed on the object placement member. Detects that the device is placed on the placement member.

<Embodiment> An example in which an embodiment of the object detection device of the present invention is used in an electric carpet will be described with reference to FIGS. 1 to 3.

In the electric carpet of the present invention, a heating element 4 is disposed in a meandering manner on a lower body 3 which together with an upper body 1 forms a carpet body 2 which is an object placement member. Piezoelectric films 5a, 5 formed into a ribbon shape and N-shape
b and 5c, respectively, and the upper body 1 is attached or welded to the lower body 3 so that the heating element 4 and the piezoelectric films 5a, 5b, and 5c are sandwiched between the lower body 3, and the carpenter is attached to the lower body 3. A control section 6 is provided at a corner of the main body 2 to detect the presence or absence of a human body based on the voltage generated by the piezoelectric films 5a, 5b, and 5c, and to control the energization of the heating element 4.

First, one end of the piezoelectric film 5a, 5b, 5c, which is provided with the lead wire 7 for taking out the generated voltage, is
The piezoelectric films 5a, 5b,
5c is disposed toward the other side opposite to one side of the lower body 3 as shown in FIG. The vinyl chloride rod 9 and the piezoelectric films 5a, 5 are folded back along the outer periphery of the vinyl chloride rod 9, which is a bent body formed into a round rod having a round shape.
b and 5c are fixed to the lower body 3 near the other side with the hot melt 8.

Then, the piezoelectric films 5a, 5b, 5c are arranged toward one side of the lower body 3, and the piezoelectric films 5a, 5b, 5c are arranged near one side of the lower body 3 in the same manner as above.
5c is folded back along the outer periphery of the vinyl chloride rod 9, and the vinyl chloride rod 9 and the piezoelectric films 5a, 5b, 5c are fixed to a portion near one side of the lower body 3 using the hot melt 8.

Further, the other ends of the piezoelectric films 5a, 5b, 5c are disposed toward the other side of the lower body 3, and the piezoelectric films 5a, 5b, 5c are disposed near the other side of the lower body 3.
5c is fixed with hot melt 8, and the piezoelectric films 5a, 5b, 5c are arranged on the lower body 3 in a substantially N-shape.

The radius of the vinyl chloride rod 9 is set as follows.

The piezoelectric film 5 (in the embodiment, piezoelectric films 5a, 5b, and 5c are provided, but the same piezoelectric film is used, so the description will be referred to as the piezoelectric film 5) is made up of a film part 10 and an aluminum film part 10, as shown in FIG. Assuming that it is a composite beam with the electrode 11 formed by vapor deposition, the peeling of the electrode 11 is caused by the film part 1
This is considered to be due to the difference in strain caused by the difference in elastic constants between the piezoelectric film 5 and the electrode 11, so the allowable radius of curvature is determined with the piezoelectric film 5 bent as shown in FIG.

As shown in FIG. 3, ρ is the piezoelectric film 5
is the radius of curvature when bent, and the neutral axis at this time is N-
It is indicated by N′. The thickness of the film portion 10 is 2T, and the thickness of the electrode 11 formed by vapor deposition of aluminum is t. The bending stress at point P in FIG. 3 is expressed as σ=Ef・T/ρ, and the thickness t of the electrode 11
is a sufficiently small value with respect to the thickness 2T of the film portion 10, the bending stress applied to the electrode 11 is equal to the bending stress applied to the point P, and the electrode 11
If the breaking stress of aluminum vapor-deposited is σb, then
The radius of curvature at which the electrode 11 does not break is ρ≧Ef·T/σb (2T》t) (1). Note that Ef is the longitudinal elastic modulus of the film portion 10.

For example, if a piezoelectric film 5 is used in which an electrode 11 is provided by vapor-depositing aluminum to a thickness of 5 μm on a film portion 10 having a wall thickness 2T of 30 μm, the diameter d of the vinyl chloride rod 9 used to bend the piezoelectric film 5 is used. The aluminum breaking stress is approximately 7Kg/mm ² , and the film part 1
If the elastic constant of 0 is 250Kg/ ^mm2 , then from the above equation (1), d≧2(250×0.015/7−(0.015+0.005)) 〓1.03mm, so in one embodiment, it is more certain that aluminum 2 mm in diameter to prevent electrode 11 from peeling off due to vapor deposition.
The above-mentioned vinyl chloride rod 9 is used.

In addition, as another embodiment of the object detection device of the present invention, as shown in FIG. The vinyl chloride rod 12 may be easily held and positioned when it is attached to the carpet body 2 with the hot melt 8.

As another embodiment of the object detection device of the present invention, as shown in FIG.
, one end of the vinyl chloride rod 9 is provided on the side wall 15 of the recess 14 , two notches 17 are provided adjacent to each other on the front wall 16 of the recess 14 for passing the piezoelectric film 5 through, and the connector body 13 may be provided with a lid 18 for closing the recess 14 to form a connector 19 for attaching the piezoelectric film 5, and the connector 19 may be provided on the carpet body 2. Such a connector 19 is constructed by opening the lid 18, inserting the piezoelectric film 5 into the recess 14 through one of the notches 17, hooking the piezoelectric film 5 onto the vinyl chloride rod 9 in the recess 14, and The piezoelectric film 5 is pulled out from the other notch 17.

In this way, if the connector 19 is used, only the connector 19 can be attached to the hot melt 8.
After fixing the connector 19, the piezoelectric film 5 is placed (the vinyl chloride rod 9 of the connector 19).
The connector 9 and the piezoelectric film 5 do not need to be fixed to the lower body at the same time, and the piezoelectric film 5 can be easily installed.

<Effects of the Invention> Since the object detection device of the present invention has the above-described configuration, both sides of the piezoelectric film at the bent portion where the ribbon-shaped piezoelectric film is bent along the outer circumferential surface of the folded body. Peeling of the electrode formed by metal vapor deposition and cracking of the piezoelectric film can be reliably prevented with a simple configuration, and objects can be reliably detected.

[Brief explanation of drawings]

Fig. 1 is a schematic perspective view showing an example in which an embodiment of the object detection device of the present invention is used in an electric carpet, Fig. 2 is an enlarged section of section A in Fig. 1, and Fig. 3 is a piezoelectric film shown in Fig. 1. FIG. 4 is an enlarged view of main parts showing another embodiment of the object detection device of the present invention, and FIG. 5 is another embodiment of the object detection device of the present invention. FIG. 6 is a schematic perspective view showing an example of a conventional object detection device used in an electric carpet. In the figure, 2...carpet body, 5...piezoelectric film, 9...vinyl chloride rod.

Claims (1)

[Claims for Utility Model Registration] A ribbon-shaped piezoelectric film with electrodes formed by metal vapor deposition on both sides, which generates a voltage when pressure is applied by an object, and the ribbon-shaped piezoelectric film arranged in a meandering manner, and an object placement member on which an object is placed, the piezoelectric film generates a voltage due to the pressure of the object placed on the object placement member, and the object detection detects placement of the object based on the generated voltage. In the apparatus, a bending body having an outer circumferential surface with a predetermined radius for preventing damage to the piezoelectric film when the piezoelectric film is arranged in a meandering shape and bent is provided on the object mounting member; The piezoelectric film is bent along the outer peripheral surface of a curved body, the folded body is fixed to the object placement member, and the piezoelectric film is arranged on the object placement member in a meandering manner. Object detection device.