JP2006317340A - Load sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a load sensor for incorrect operation and operation incapability by suppressing a settling phenomenon of an insulating film of the load sensor and always surely carrying out sensing operation suitable for a state of load burden. <P>SOLUTION: The load sensor comprises a flexible insulating spacer 10 having a cell hole 11; first and second flexible insulating films 12 and 13 arranged mutually in substantially parallel by being superposed on both the faces of the spacer 10 respectively; a plurality of first and second cell electrodes 7a and 7b provided on each inner face of the first and second films by being oppositely arranged in each cell hole in order to sense a load state from the outside; and a circuit wiring layers 8a and 8b formed on at least one of the first and second films. At least one cell electrode of the first and second cell electrodes has pressure sensitive resistant layers 7a2 and 7b2 on the surface. The pressure sensitive resistant layer has projections 7a3 and 7b3 projected toward the other opposite cell electrode. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a load sensor, and more particularly to a flexible film-like load sensor suitable for a seating sensor (switch) for detecting a seating state on a seat.

  For example, an automobile seat belt wearing system is equipped with an electrical display panel that indicates whether the seat belt is worn or not, and a flexible film-like seating (load) sensor installed on the back side of the seat skin of the seat. It has a role of transmitting a sense signal corresponding to the signal to the panel display circuit.

  The prior art regarding this kind of film-like seating sensor or seating membrane switch is already known (for example, refer to Patent Document 1). This conventional sensor has a distribution pattern of a plurality of sensor cells (unit bodies) corresponding to the seating sense range of the seat.

  In the structure of the first example of the cell (unit body), as shown in FIG. 6A, a cell hole 52 made of, for example, a circular through hole is formed in a part of the flexible insulating spacer 51. Flexible flat first and second insulating films 53 and 54 are overlaid on both surfaces of the spacer 51 so as to close the cell holes 52. And, for example, in a state where the first and second cell electrodes 55 and 56 having good conductivity made of a silver paste layer and a protective carbon layer on the surface thereof face each other at a predetermined interval in the cell hole 52, The first and second films 53 and 54 are respectively attached to the inner surfaces.

  In the cell of the first example structure, generally, each of the insulating films 53 and 54 is made of PEN (polyethylene naphthalate) and has a thickness of about 100 μm. The spacer 51 is a PET (polyethylene terephthalate) base material and its double-sided adhesive tape. It is made of an adhesive material, and the substrate thickness is about 100 μm, the adhesive material thickness is about 25 μm × 2, the total thickness is about 150 μm, and the diameter of the cell hole 52 is about 10 mm.

  Further, in the structure of the second example of the cell (unit body), as shown in FIG. 6B, in addition to the structure of the first example, a pressure-sensitive resistance layer using a pressure-sensitive ink of a high-resistance material. 57 and 58 are provided on the first and second cell electrodes 55 and 56, respectively, and the members having the same reference numerals as those in the first example have the same material, shape and dimensions.

When the spacers are not seated, the contact cells of the wiring layers facing each other are separated from each other (off state), but when seated, the insulating film is pressed and the cell electrodes in the space in the cell hole are pressed. Touched (on state), for example, a sensor signal is supplied to a seat belt wearing system.
Japanese Patent No. 29099961 (Japanese Patent Laid-Open No. 9-315199)

  However, the sensor causes material deterioration related to flexure and restoration of the insulating film due to repeated operation of ON / OFF corresponding to the seating / non-sitting (loading / non-loading), and the on-load value is lowered. In the extreme case, as shown by the broken line in FIG. 6A, the first insulating film 53 causes a sag and the first cell electrode 55 is always in contact with the second cell electrode 56. There is a problem that the sensing operation function is easily impaired by being always on regardless of the presence or absence of a load.

  According to an experiment, the sagging phenomenon is such that when the sensor gives a temperature of 100 ° C. for 1000 hours under no load, the on-load value decreases by about 30%. For 50 hours, when the temperature of 100 ° C. is applied, it is progressing to the extent that it is always on (switching operation impossible).

  Here, the resistance (logarithm value) -load pressure (logarithm value) characteristic will be described with reference to FIG. 5. The sensor of the first example has a good conductivity as shown in the characteristic line 41 at the same time as the load application in the normal state. The cell electrodes come into contact with each other, rapidly saturate to an extremely low resistance value, and enter the ON state.

  Therefore, when the sag phenomenon of the insulating film occurs, as shown by the characteristic line 41a, it is turned on at a low load, and in an extreme case, it is always turned on even at no load as shown by the characteristic line 41b.

  Further, the sensor of the second example has a resistance with a gentler slope than that of the first example in accordance with a change in the contact area between the pressure sensitive resistors according to a change in the load amount after a load is applied as in the characteristic line 42 in a normal state. The value (bulk resistance of the pressure-sensitive resistance layer + mutual contact resistance) decreases almost linearly and reaches a saturated state.

  Therefore, when the sag phenomenon of the insulating film occurs, as shown by the characteristic line 42a, the resistance value enters a saturation region at a low load, and the on load decreases. In the second example, since the resistance threshold value for the peripheral device operation can be set, it can be adjusted so as to avoid the always-on state in the circuit operation even if the structure-on-state due to the sag phenomenon occurs.

  The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a load sensor that can always reliably perform a sensing operation adapted to the state of a load and that prevents malfunction and inoperability.

  According to a first aspect of the present invention, there is provided a load sensor according to the present invention, comprising: a flexible insulating spacer having a cell hole made of a through-hole; and each cell hole is closed and overlapped on both surfaces of the spacer so as to be substantially parallel to each other. The flexible first and second insulating films that are arranged and the inner surfaces of the first and second films that are arranged to face each other in the cell holes in order to sense an external load state are provided. A first and second cell electrode; and a circuit wiring layer formed on at least one of the first and second films and related to the cell electrode, wherein at least one cell electrode of the first and second cell electrodes is A pressure-sensitive resistance layer is provided on the surface, and the pressure-sensitive resistance layer has a protrusion protruding toward the other cell electrode facing each other.

  According to a second aspect of the present invention, in the load sensor according to the first aspect, a total thickness of the first cell electrode and the second cell electrode in the protrusion is equal to or greater than a thickness of the spacer. It is characterized by being.

  According to a third aspect of the present invention, in the load sensor according to the first or second aspect, the pressure-sensitive resistance layer is formed by mixing a pressure-sensitive ink with a granular material as a material for forming the protrusion. It is characterized by that.

  According to the load sensor of the present invention, since the pressure-sensitive resistance layer provided on at least one cell electrode has a protrusion protruding toward the other cell electrode facing each other, Even if the film is exposed to an external environment that is prone to sag, the sag phenomenon of the insulating film in actual use is suppressed or prevented, and the sensing operation adapted to the load condition is always executed reliably, causing malfunction. In addition, it is possible to prevent inoperability.

  Hereinafter, an embodiment in which a load sensor according to the present invention is applied to, for example, a seating sensor (switch) mounted on an automobile seat will be described with reference to FIGS. 1 to 4.

  FIG. 1 (a) shows the overall planar pattern structure of the seating switch. The seating sensor 1 has various pattern shapes depending on the shape of the seat seat (attached body), the setting of the sensing area, and the like. As an example, the seating sensor 1 has a substantially Y-shaped pattern as shown in the figure. It has the trunk part 2 and the 1st thru | or 3rd branch parts 3, 4, and 5 branched into the strip shape of 3 rows, for example. For example, a plurality of substantially circular sensor cells 6 each serving as a switch cell are juxtaposed in a series of states for each of the branch sections at predetermined intervals.

  Each cell 6 is provided with a first cell electrode 7a and a second cell electrode 7b constituting a pair of cell electrodes, and a plurality of first cells are provided for each of the branch portions 3, 4, and 5. A first circuit wiring layer 8a connecting the cell electrodes 7a and a second circuit wiring layer 8b connecting the plurality of second cell electrodes 7b are arranged along the extending direction of the pattern. The first and second wiring layers 8 a and 8 b are led to a terminal portion 9 provided in a part of the trunk portion 2, and are connected to peripheral devices through the terminal portion 9. Such a seating sensor is disposed in a seating sensing range of the seat seat (attached body), and senses whether or not an occupant is seated on the seat (external load state).

  Next, since the plurality of cells 6 have substantially the same shape and size, refer to FIGS. 1B and 1C for the structure of one cell (unit body). I will explain.

  For example, a cell hole 11 made of, for example, a circular through hole is formed in a part of a flexible film-like insulating spacer 10 made of PEN or PET, for example, so that the cell hole 11 is blocked on both surfaces of the spacer 10. In addition, flexible first and second insulating films 12 and 13 made of, for example, PET are arranged so as to be substantially parallel to each other. The spacer 10 and the insulating films 12 and 13 are bonded to each other with an adhesive (not shown).

  Then, first and second cell electrodes 7a and 7b made of, for example, circular thin layers facing each other in the cell hole 11 are formed on the inner surfaces of the first and second films 12 and 13 by circuit printing technology. In addition, a cell electrode pair is configured for each cell unit.

  The first cell electrode 7a is formed on the inner surface of the first insulating film 12, for example, a first cell electrode layer 7a1 made of a highly conductive material such as silver paste, and the surface of the first cell electrode 7a is deposited on the surface of the first cell electrode layer 7a1. It has a two-layer structure composed of a first pressure-sensitive resistance layer 7a2 made of a high resistance material such as pressure ink. The first pressure-sensitive resistance layer 7a2 has a shape having a plurality of first protrusions 7a3 that are formed by, for example, a printing technique so as to have an uneven surface, and protrude in the direction of the other cell electrode facing each other. ing.

  Similarly to the first cell electrode 7a, the second cell electrode 7b is formed of a second cell electrode layer 7b1 made of a silver paste of a highly conductive material and a high resistance material sensitively deposited on the surface thereof. The second pressure-sensitive resistance layer 7b2 made of pressure ink has a two-layer structure, and the second pressure-sensitive resistance layer 7b2 has a shape having a plurality of second protrusions 7b3 whose surfaces are uneven. Yes.

  Each of the plurality of first and second protrusions is scattered on each planar pattern of the pressure-sensitive resistance layers 7a2 and 7b2 constituting the surface layers of the respective cell electrodes 7a and 7b, for example, like paper file abrasive grains. The pressure-sensitive ink can be directly formed by printing, for example, so as to achieve the state.

  An example of an effective method for forming the scattered state of a plurality of protrusions is shown in FIG. 2, for example, a spherical elastic material made of, for example, nylon resin or silicon resin as a material for forming the protrusions. The granular material or particle 7a4 or 7b4 is used.

  And, by printing or applying the pressure sensitive ink in which the particles 7a4 or 7b4 are mixed as a filler on or either one of the first electrode layer 7a1 and the second electrode layer 7b, scattered protrusions 7a3, The first pressure-sensitive resistor layer 7a2 and the second pressure-sensitive resistor layer 7b2 having 7b3 can be easily formed. In this case, the height of the protruding portion only needs to be selected and managed mainly by the particle size of the spherical particles, and the adjustment of the height of the protruding portion and the formation management are remarkably simple.

  The height of the first projecting portion 7a3 and the second projecting portion 7b3 is set to a height at which the first projecting portion 7a3 and the second projecting portion 7b3 are in contact with each other in a state of substantially abutting each other. In order to ensure this contact state, here, the total thickness T of the first cell electrode 7a and the second cell electrode 7b including the protrusions 7a3 and 7b3 is the thickness of the spacer (first And equivalent to the interval between the second insulating films), and is designed so that T> t.

  Thus, since the first cell electrode 7a and the second cell electrode 7b are always in contact with each other, the first and second sensor electrodes are used from the sensor product completion to the use state. The insulating films 12 and 13 are mechanically supported substantially in parallel.

  Therefore, according to the seating sensor of the present invention according to this embodiment, even if the insulating films are exposed to an external environment in which the respective insulating films tend to sag in the repeated operation of the sensor, for example, under high temperature use conditions, The film sag phenomenon is suppressed or prevented. Therefore, the sensing operation adapted to the load load state is always executed reliably, and malfunctions and inoperability are prevented.

  Further, the resistance (logarithmic value) -load pressure (logarithmic value) characteristics of the seating sensor of the present invention according to this embodiment are as shown by the characteristic line 43 in FIG. The resistance value (bulk resistance of the pressure-sensitive resistance layer + mutual contact resistance) is almost linear with a gentle slope in the same manner as in the conventional second example, with the change in the contact area between the pressure-sensitive resistances corresponding to the change in the load amount. Decreases to saturation. Further, in the present embodiment, due to the presence of the protrusions 7a3 and 7b3, the surface area of the pressure-sensitive resistance layer is significantly larger than that of the second example, and the first and second pressure-sensitive resistances when loaded are applied. Since the contact area between the layers is remarkably increased and the contact resistance is decreased, the characteristic line 43 shows a characteristic shifted so as to have a saturation resistance value lower than that of the characteristic line 42.

  For this reason, there is an advantage that the resistance threshold with respect to the peripheral device operation can be set to a wider value up to a lower value than in the second example, and can be set more freely. Further, since the sag phenomenon of the insulating film is prevented, there is no decrease in the on-load as in the characteristic line 42a shown in the second example, and the sensing operation adapted to the load condition is always executed reliably. Malfunction and inoperability are prevented.

By the way, the thickness of the main body portion of the pressure-sensitive ink layer is a value smaller than the particle diameter,
In order to reduce the contact resistance (component), when the particles 7a4 and 7b4 are made of an insulator, it is preferable that the entire surface of the particles 7a4 and 7b4 is covered with pressure-sensitive ink. When there is no need to reduce the contact resistance (component) or when a high resistance material is applied to the particles, the entire surface of the particles may not necessarily be covered with pressure-sensitive ink. Ink coating management can be made relatively rough.

  Here, the dimensions of each part of the cell 6 are as follows. The thickness of the insulating films 12 and 13 is about 100 μm, the thickness t of the spacer 10 is about 50 μm, the diameter of the cell hole 11 is about 10 mm, and the first cell. The thicknesses of the electrode 7a and the second cell electrode 7b are each about 25 μm or more, and the total thickness T of both at the protruding portion is about 50 μm or more, and T ≧ t. In this case, the spherical particles 7a4 and 7b4 have a diameter of about 20 to 30 μm, and the diameter of each cell electrode is about 8 mm which is smaller than the cell hole diameter.

  The relationship of T ≧ t indicates that in the sensor assembly, the height of the protrusion is already adjusted so that the first cell electrode 7a and the second cell electrode 7b are in contact with each other. This means that the influence of the sag phenomenon of the insulating films 12 and 13 is surely prevented.

  By the way, even if the total thickness T of the cell electrode pair is slightly smaller than the thickness t of the spacer, the sensor operation can have an effect of preventing the influence of the sag phenomenon. In other words, it is preferable that the height of the protruding portion is set to a height at which the first cell electrode 7a and the second cell electrode 7b are substantially in contact with each other when no load is applied.

  In addition, by preventing the sagging phenomenon, the insulating films 12 and 13 can be made of inexpensive PET instead of expensive PEN excellent in high temperature characteristics, and the spacer thickness is the same as the conventional one. The adhesive can be made as thin as about 1/2, and the adhesive for bonding the insulating film and the spacer can be easily formed in advance by printing on the required surface of the insulating film. There is also an attendant effect that it can be significantly reduced.

  3A, 3B and 3C show various modifications of the sensor of the present invention relating to the planar pattern of the protrusions 7a3 and 7b3 formed on the pressure-sensitive resistance layers 7a2 and 7b2 of the cell electrodes 7a and 7b. It is shown. Each of the protrusions 7a3 and 7b3 represents the pattern of the ridgeline of the peak at the top of the protrusion, and the protrusion shown in FIG. 3 (a) has a plurality of linear parallel lines, as shown in FIG. ) Is formed in a pattern in which the ridgeline is a plurality of zigzag parallel lines, and the protrusion shown in FIG. 3C is a pattern in which the ridgeline is a plurality of coaxial circular rings. Of course, the spherical particles 7a4 and 7b4 shown in FIG. 2 may be arranged in such a pattern.

  By adopting the above modification, a pressure-sensitive resistance layer having various surface areas can be formed by selecting the number of ridge lines of the protrusion and the pattern shape, so that the contact resistance constituting one component of the on-resistance is a desired small value. Can be set to For example, the surface area and the contact resistance component of the pressure-sensitive resistance layer are smaller in FIG. 3B than in FIG. 3A, the on-resistance is reduced, and the resistance threshold value can be set lower and more easily in a wide range. Become.

  FIGS. 4A and 4B show a modification of the structure of the first and second cell electrodes 7a and 7b, and the same reference numerals are assigned to the same parts as those of the sensor of the above embodiment. Therefore, the description is omitted.

  That is, in the modification of FIG. 4A, the first and second cell electrodes 7a and 7b omit the first and second cell electrode layers 7a1 and 7b1 in the embodiment, and the first and second insulating films 12 are omitted. , 13 is formed of first and second pressure-sensitive resistance layers 7a2, 7b2, which are directly attached to the respective layers.

  In this case, although the first and second pressure-sensitive resistance layers 7a2 and 7b2 are not illustrated, the first and second circuit wiring layers 8a and 8b shown in FIG. Connected. Of course, the cell electrode layer may be provided on one of the first and second cell electrodes 7a and 7b.

  In the modification of FIG. 4B, the first pressure-sensitive resistance layer 7a2 has a protrusion 7a3, and the second pressure-sensitive resistance layer 7b2 has a flat shape without a protrusion, and in this case, the protrusion 7a3. (The maximum thickness of the pressure-sensitive resistance layer) is larger than the height of the protrusion in the above embodiment. Also in this case, as in the modification of FIG. 4A, at least one of the first and second cell electrode layers 7a1 and 7b1 may be omitted.

  Although the number of the protrusions is plural in the above-described example, it goes without saying that the effect can be obtained if at least one protrusion is provided in order to improve the problem of the sag phenomenon of the prior art. .

  In the embodiment, as shown in FIG. 1, the first and second circuit wiring layers 8a and 8b are formed on the first and second insulating films 12 and 13, respectively. As a modification of the above, the second cell electrode 7b has a configuration in which two comb-shaped portions are arranged in parallel with each other in a meshed state, and two circuit wiring layers respectively connected to the respective comb-shaped portions are connected to the second insulating layer. The first cell electrode 7a formed on the film 13 is separated (off state) from the two comb-shaped parts when not seated, and contacts the both comb-shaped parts when seated (when loaded). You may form so that both the comb-shaped parts may be short-circuited (ON state).

  In this case, the first cell electrode 7a and the first insulating film 12 do not need to be provided with a circuit wiring layer. Therefore, the circuit wiring layer includes the first and the first electrodes in order to configure the circuit according to the cell electrode structure. It may be formed on at least one of the second insulating films and electrically coupled (coupled) to the cell electrodes to form a closed switching circuit related to each cell electrode.

  In the above-described embodiment, an example in which the present invention is applied to a so-called digital switching operation like a seating sensor (switch) has been described. However, the contact area from the initial partial contact between the cell electrodes varies depending on the sensor. It is also possible to apply the present invention to a pressure-sensitive sensor that shows an expansion change with respect to the sense surface and can sense an analog change in the load amount. In this case, the contact area between the pair of pressure-sensitive resistance layers is increased due to the presence of the protrusions, so that the analog change can be sensed with linearity in a wide range.

It is a figure which shows the load sensor which concerns on one Embodiment of this invention, (a) is the partially notched top view which shows the whole image, (b) is the partially notched top view which expands and shows the sensor cell unit body, (C) is sectional drawing which follows the AA line of (b). FIG. 2A shows an example of a pressure-sensitive resistance layer structure of a load sensor according to an embodiment of the present invention, FIG. 2A is a plan view thereof, and FIG. 2B is a CC line in FIG. It is sectional drawing which follows. The other modification of the pressure-sensitive resistance layer of the load sensor which concerns on one Embodiment of this invention is shown, (a) thru | or (c) are all the top views. The modification of the structure of the 1st and 2nd cell electrode of the load sensor which concerns on one Embodiment of this invention is shown, (a) And (b) are all the sectional drawings. It is a characteristic view for comparing and explaining the resistance (logarithmic value) -load pressure (logarithmic value) characteristics in the load sensor according to an embodiment of the present invention and the related art. (A) And (b) is sectional drawing which shows both the sensor cell unit bodies of the conventional load sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Load sensor 6 Sensor cell 7a 1st cell electrode 7a1 1st cell electrode layer 7a2 1st pressure sensitive resistance layer 7a3 1st projection part 7a4, 7b4 Spherical particle 7b 2nd cell electrode 7b1 2nd cell electrode layer 7b2 2nd pressure sensitive resistance Layer 7b3 Second protrusions 8a and 8b Circuit wiring layer 10 Spacer 11 Cell hole 12 First insulating film 13 Second insulating film

Claims (3)

  A flexible insulating spacer having a cell hole made of a through hole, and a flexible first and second insulating member which closes each cell hole and overlaps both surfaces of the spacer and is arranged substantially parallel to each other. A first and second cell electrode disposed opposite to each other in each cell hole to sense a load state from the outside, and provided on each inner surface of each of the first and second films; and A circuit wiring layer formed on at least one of the second films and related to the cell electrode, and at least one of the first and second cell electrodes has a pressure-sensitive resistance layer on a surface thereof, and the pressure-sensitive layer The resistance layer has a protrusion that protrudes toward the other cell electrode facing each other.   2. The load sensor according to claim 1, wherein a total thickness of the first cell electrode and the second cell electrode in the protrusion is equal to or greater than a thickness of the spacer.   3. The load sensor according to claim 1, wherein the pressure-sensitive resistance layer is formed by mixing a pressure-sensitive ink with a granular material as a material for forming the protrusions. 4.

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