JP2008039450A - Pressure sensitive sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure sensitive sensor hardly influenced by disturbance with excellent detection performance and manufacturing efficiency. <P>SOLUTION: A piezoelectric sensor 8 deforms with an elastic body 14 and a voltage signal generates from the piezoelectric sensor 8 according to an applied acceleration. The signal is signal-processed at a filter, a magnification and a comparator circuit of a signal processing part 9, and the determination signal is transmitted to a controlling means 10. When a short circuit or a disconnection between a central electrode 8a and an outside electrode 8c of the piezoelectric sensor 8 occurs, the combined impedance of the piezoelectric sensor 8 and a resistance 11 from view of the signal processing part changes, the trouble of the disconnection or the short circuit of the electrodes is detected by detecting this change by the signal processing part 9 thereof. With the constitution of the piezoelectric sensor 8 whereby the both terminal parts of the piezoelectric sensor 8 are folded into a radio wave shielding body 12 covering the signal processing part 9, to perform radio wave shielding constitution individually is not necessary, the constitution is simplified thereof to reduce cost and improve manufacturing efficiency. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pressure-sensitive sensor using a cable-shaped piezoelectric sensor having flexibility.

  Recently, in vehicles called wagons and vans, so-called electric sliding doors that open and close by sliding a door panel along the front-rear direction by a motor drive have rapidly spread. In these electric sliding door type vehicles, in case of a person or an object being caught between the sliding door and the vehicle during the door closing operation, this pinching state is detected and the operation of the door is automatically reversed. A pinch sensor is required, and a pinch sensor using a piezoelectric sensor obtained by processing a piezoelectric body into a cable shape is disclosed (for example, see Patent Document 1).

  FIG. 5 is a cross-sectional view of a main part of an anti-pinch device provided with a pressure-sensitive sensor in the electric slide door described in Patent Document 1. Reference numeral 1 denotes a body side body (front seat door end surface), 2 a slide door, 3 a piezoelectric sensor, and 4 a support portion for supporting the piezoelectric sensor 3 on the slide door 2. FIG. 6 is an external view of a pressure-sensitive sensor provided with determination means of the same device. A resistor enclosing portion 5 in which a resistor for detecting disconnection / short-circuiting of the piezoelectric sensor 3 is encapsulated at the end of the piezoelectric sensor 3; A detection unit 6 including a filter, an amplifier, a comparator, a disconnection / short detection circuit, and the like is connected, and a power source and a detection signal input / output cord 7 are connected to the detection unit 6. FIG. 7 is a cross-sectional view of the piezoelectric sensor. The piezoelectric sensor 3 itself has a spiral shape with an overlap margin on the center electrode 3a, a piezoelectric body 3b in which a rubber elastic body is mixed with piezoelectric ceramic powder, and a piezoelectric body 3b. The outer electrode 3c and the coating layer 3d around which a thin film conducting wire is wound are concentrically stacked to form a flexible cable.

In addition, piezoelectric sensors are arranged on the inner area side and the outer area side of the electric sliding door, and the inner area side and the outer area side are configured with one piezoelectric sensor by folding back one piezoelectric sensor. A configuration is also disclosed in which pinching can be detected (see, for example, Patent Document 2).
JP 2004-316087 A JP 2002-4714 A

  However, in the configuration of Patent Document 1, the center electrode 3a and the piezoelectric body 3b of the piezoelectric sensor 3 are not easily affected by disturbance (radio wave noise) because the outer side is covered with the outer electrode 3c made of a thin film conducting wire. Since the terminal portion of the sensor 3 is not covered with the outer electrode 3c, it is likely to be weak against disturbance. For this reason, the structure which covers the circumference | surroundings of the detection part 6 to which the terminal part of the piezoelectric sensor 3 was connected with radio wave shielding materials, such as a metal body, is known. Similarly, the disconnection / short detection resistor enclosing portion 5 connected to the other end portion of the piezoelectric sensor 3 is also susceptible to disturbance. For this reason, it is generally necessary to cover the periphery of the resistor enclosing portion 5 with a radio wave shielding material (metal, conductive resin, etc.) in a configuration that has the same potential as the outer electrode 3c of the terminal portion. Both terminal portions had to be subjected to disturbance countermeasures, and had the disadvantage of poor productivity and high cost.

  In addition, when the outside of the resistor enclosing portion 5 is covered with a conductive resin material, there is a limit to the reduction in the thickness of the molding when trying to improve the moldability, and the resistance is smaller than the outer diameter of the piezoelectric sensor. It had the fault that the external dimension of the body enclosure part 5 will become large.

  On the other hand, when a piezoelectric sensor is mounted on an automobile or the like as a sandwiching sensor, the piezoelectric sensor is passed through an elastic body called a protector in advance, and the piezoelectric sensor is easily displaced when the sandwiching occurs. For this reason, as a method for inserting a cable-like long component such as a piezoelectric sensor into an elastic body, a method is known in which pressurized air is fed into a through-hole on the insertion side and the inner diameter is expanded. However, when the breaker / short detection resistor encapsulating portion is processed in advance and then passed through the elastic body as in Patent Document 1, the outer dimensions of the disconnection / short detection resistor enclosing portion and the piezoelectric sensor are reduced. If the difference becomes large, the insertion work becomes difficult even if the above method is used, and if the inner diameter of the elastic body is made larger than the outer diameter of the piezoelectric sensor in order to improve this, a gap is generated between the piezoelectric sensor and the elastic body, and the vibration of the vehicle As a result, the piezoelectric sensor vibrates and has a disadvantage of being easily detected erroneously.

  In the piezoelectric sensor 3 of Patent Document 1, a resistor enclosing portion 5 for detecting disconnection / short circuit is provided at the terminal portion in order to detect disconnection / short circuit of the electrode. The resistor connection between the center electrode and the outer electrode of the piezoelectric sensor is not required, but the countermeasure for the disturbance of the terminal part is necessary in the same manner as described above, and as a countermeasure, the periphery of the terminal part is covered with a conductive resin material. As a result, the outer diameter of the terminal portion is thicker than that of the piezoelectric sensor, and there is a problem similar to that described above.

  In the configuration of Patent Document 2, the piezoelectric sensors are disposed on the inner region side and the outer region side of the electric slide door, and the piezoelectric sensor is disposed at a location near the outside and a location near the inside of the slide door. Although it is possible to detect the pinching in a wider range, the disconnection / short detection resistor described in Patent Document 1 is not specified, but when the terminal treatment similar to the above is performed as a measure against disturbance It is easily estimated that the same problem as described above occurs. In addition, a configuration in which one piezoelectric sensor is folded and disposed on the inner region side and the outer region side is disclosed, but for the purpose of detecting pinching at a position apart from the inner region side and the outer region side, Although the sandwiching detection area is widened, the folded piezoelectric sensors are separated from each other. Therefore, it cannot be expected that both folded piezoelectric sensors simultaneously detect the sandwiching and increase the detection sensitivity.

  The present invention solves the above-described conventional problems, and an object of the present invention is to provide a pressure-sensitive sensor that has excellent terminal processing productivity and is resistant to disturbance.

  In order to solve the above-mentioned conventional problems, a pressure-sensitive sensor according to the present invention comprises four layers of a central electrode, a piezoelectric body, an outer electrode, and a coating layer, and has a flexible coaxial piezoelectric sensor, A signal processing unit connected to one end for filtering, amplifying and comparator processing the output signal of the piezoelectric sensor; and an electromagnetic shield covering the signal processing unit; It is set as the structure accommodated.

  This makes it possible to provide a pressure sensitive sensor that is resistant to disturbances and excellent in terminal processing productivity.

  The pressure-sensitive sensor of the present invention is configured to house the other end of the piezoelectric sensor inside the radio wave shield covering the signal processing unit connected to one end of the cable-shaped piezoelectric sensor. Since a single radio wave shield can also be used as a measure against disturbance at both ends of the piezoelectric sensor, a pressure-sensitive sensor that is resistant to disturbance and excellent in assemblability can be provided.

The first invention comprises four layers of a central electrode, a piezoelectric body, an outer electrode, and a covering layer, a flexible coaxial piezoelectric sensor, and one end of the piezoelectric sensor connected to the filter, amplifier, comparator circuit, etc. The piezoelectric sensor includes a signal processing unit that processes an output signal of the piezoelectric sensor and an electromagnetic shield that covers the signal processing unit, and the other terminal unit of the piezoelectric sensor is also accommodated in the radio wave shield. . As a result, it is not necessary to individually take measures against disturbance at both terminal portions of the piezoelectric sensor, and productivity can be improved.

  According to a second aspect of the present invention, a function of detecting disconnection / short circuit of the electrode of the piezoelectric sensor is added to the signal processing unit of the pressure-sensitive sensor according to the first aspect of the invention. A high-impedance resistor is connected between the outer electrodes, and since the connecting portion between the resistor and each electrode of the piezoelectric sensor is located inside the radio wave shield, a resistor is connected to the terminal portion of the piezoelectric sensor. Also in the pressure-sensitive sensor having a body, it is possible to provide a pressure-sensitive sensor that is resistant to disturbance and excellent in productivity as in the first invention.

  According to a third aspect of the invention, the resistor of the pressure-sensitive sensor of the second aspect of the invention is configured to be integrally disposed on the same control board that forms the signal processing unit, and the resistor is mounted on the circuit component of the signal processing unit. Since it can be mounted at the same time, productivity is improved.

  According to a fourth invention, the piezoelectric sensor of the pressure sensor according to any one of the first to third inventions is held in the same space in the folded elastic body, and the folded portion of the piezoelectric sensor is made of an elastic body. Since the piezoelectric sensor inserted into the elastic body does not include the terminal processed portion, the thickness is uniform, and the insertion workability is improved and the gap between the piezoelectric sensor and the elastic body is provided. The piezoelectric sensor can be prevented from vibrating and erroneously detecting. In addition, since the two piezoelectric sensors that are folded and close to each other can detect pinching in almost the entire area of the elastic body, it is possible to provide a pressure-sensitive sensor that has almost no dead area and high detection sensitivity.

  According to a fifth aspect of the present invention, an insulating resin is filled in the radio wave shield of the pressure sensitive sensor according to any one of the first to fourth aspects of the invention. Fixing and waterproofing of the control processing board and the terminal processing unit of the pressure line sensor are possible, and the reliability can be improved.

(Embodiment 1)
A pressure-sensitive sensor according to a first embodiment of the present invention will be described with reference to FIGS.

  1 is a cross-sectional view of the pressure-sensitive sensor, FIG. 2 is a cross-sectional view of the main part of the sensor, and FIG. 3 is a cross-sectional view of the A-A ′ portion of FIG.

  The piezoelectric sensor 8 includes four layers of a center electrode 8a, a piezoelectric body 8b, an outer electrode 8c, and a covering layer 8e, and is configured in a flexible coaxial cable shape. A signal processing unit 9 is connected to the center electrode 8 a and the outer electrode 8 c of the terminal portion of the piezoelectric sensor 8, and a control means 10 is connected to the tip of the signal processing unit 9. The other end portion of the piezoelectric sensor 8 is connected to a high-impedance resistor 11 between the center electrode 8a and the outer electrode 8c. The signal processing unit 9 includes a filter, an amplifier, and a comparator circuit, and has a function of processing an output signal of the piezoelectric sensor 8 and an abnormality detection function of detecting disconnection or short of each electrode of the piezoelectric sensor 8. . Both terminal portions of the piezoelectric sensor 8 are accommodated in the same radio wave shield 12 that covers the signal processing unit 9, and the radio wave shield 12 is filled with an insulating resin 13 such as urethane. The piezoelectric sensor 8 folds back one piezoelectric sensor and is accommodated in the same space of the elastic body 14, and the folded portion 15 is disposed close to the end of the elastic body 14.

  The operation and action of the pressure sensor configured as described above will be described below.

When a stress is applied in the direction of the arrow in FIG. 3, the piezoelectric sensor 8 is deformed together with the elastic body 14, and a voltage signal is generated from the piezoelectric sensor 8 in accordance with the applied acceleration. The signal is processed by the filter, amplification, and comparator circuit of the signal processing unit 9, and the determination signal is transmitted to the control means 10.

  Further, when the center electrode 8a and the outer electrode 8c of the piezoelectric sensor 8 are disconnected or short-circuited between the electrodes, the combined impedance of the piezoelectric sensor 8 and the resistor 11 as viewed from the signal processing unit 9 changes. Detection by the signal processing unit 9 detects a disconnection or short circuit failure of the electrode. In the configuration of the pressure-sensitive sensor 8, since both terminal portions of the piezoelectric sensor 8 are accommodated in the radio wave shield 12 that covers the signal processing unit 9, it is not necessary to individually provide the radio wave shield configuration, and the configuration is simple. Cost reduction and productivity improvement.

  In addition, since the piezoelectric sensor 8 is folded and accommodated in the same space in the elastic body, when the piezoelectric sensor 8 is inserted into the hole of the elastic body 14, only the folded piezoelectric sensor having the same thickness is passed. The insertion workability is not affected by the shape of the terminal processing unit.

  Further, by folding back the piezoelectric sensor 8, the displacement at the same location can be detected by the two piezoelectric sensors 8, so that the detection sensitivity can be increased. Further, since the folded portion 15 of the piezoelectric sensor 8 is brought close to the end of the elastic body 14, the displacement of the piezoelectric sensor 8 can be detected in almost the entire area of the elastic body 14.

  Furthermore, since the inside of the radio wave shield 12 is filled with an insulating resin 13, the terminal portion of the piezoelectric sensor 8 and the resistor 11 and the signal processing unit 9 in the radio wave shield 12 are fixed and sealed. It is possible to prevent vibrations of the components in the shield 12 and the piezoelectric sensor 8 to prevent erroneous detection and to ensure waterproofness.

  In the pressure-sensitive sensor of this embodiment, a resistor is provided at the terminal portion of the piezoelectric sensor to detect disconnection and short circuit of the electrodes of the piezoelectric sensor. Even in the configuration in which the resistor is not provided, the same disturbance performance can be obtained by accommodating the terminal portion of the piezoelectric sensor in the radio wave shield.

(Embodiment 2)
A pressure-sensitive sensor according to a second embodiment of the present invention will be described with reference to FIG.

  FIG. 4 is an enlarged view of a main part of the pressure sensitive sensor. In the second embodiment, the resistor 11 connected to the terminal portion of the piezoelectric sensor 8 is mounted on the control board constituting the signal processing unit 9, and the connection between the center electrode 8a and the outer electrode 8c of the piezoelectric sensor 8 is as follows. It is configured to be electrically connected by a pattern on the control board. Since the resistor 11 can be mounted on the control board constituting the signal processing unit 9 in this way, the resistor 11 can be mounted at the same time as the circuit components of the signal processing unit 9 in advance. Improvements can be made.

  As described above, since the pressure-sensitive sensor according to the present invention can provide a pressure-sensitive sensor having a simplified configuration, excellent disturbance (radio wave noise) performance and sensing performance, and having good productivity, the slide of the automobile. It can be widely applied as a pinch detection sensor for doors, housing doors and other doors.

Sectional drawing of the pressure-sensitive sensor in Embodiment 1 of this invention Sectional drawing of the principal part of the pressure-sensitive sensor in Embodiment 1 of this invention Sectional view taken along the line AA ′ in FIG. 2 of the pressure-sensitive sensor according to Embodiment 1 of the present invention Sectional drawing of the principal part of the pressure-sensitive sensor in Embodiment 2 of this invention Cross-sectional view of the main parts of a conventional anti-pinch device equipped with a pressure-sensitive sensor on an electric sliding door External view of a pressure-sensitive sensor equipped with a conventional determination device Sectional view of a conventional pressure sensor (piezoelectric sensor)

Explanation of symbols

DESCRIPTION OF SYMBOLS 8 Piezoelectric sensor 8a Center electrode 8b Piezoelectric body 8c Outer electrode 8d Covering layer 9 Signal processing part 11 Resistor 12 Radio wave shielding body 13 Insulating resin 14 Elastic body 15 Folding part

Claims (5)

The piezoelectric sensor is composed of four layers, a central electrode, a piezoelectric body, an outer electrode, and a covering layer, and a flexible coaxial piezoelectric sensor, and one end of the piezoelectric sensor is connected to the output of the piezoelectric sensor through a filter, amplification, comparator circuit, etc. A pressure-sensitive sensor comprising: a signal processing unit that processes a signal; and a radio wave shielding body that covers the signal processing unit, and the other terminal unit of the piezoelectric sensor is also accommodated in the radio wave shielding body. A function for detecting disconnection / short circuit of the electrode of the piezoelectric sensor is added to the signal processing unit, and a high impedance resistor is connected between the center electrode and the outer electrode on the terminal side where the signal processing unit of the piezoelectric sensor is not connected. The pressure-sensitive sensor according to claim 1. The pressure-sensitive sensor according to claim 2, wherein the resistor is integrally disposed on the same control board constituting the signal processing unit. The pressure-sensitive sensor according to any one of claims 1 to 3, wherein the piezoelectric sensor is folded and held in the same space in the elastic body, and the folded portion of the piezoelectric sensor is close to the end of the elastic body. The pressure sensor according to any one of claims 1 to 4, wherein the inside of the radio wave shield is configured to be filled with an insulating resin.

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