JP2009174913A - Impact sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an impact sensor with its acceleration detection time adjustable without changing the specifications of components constituting the impact sensor. <P>SOLUTION: This impact sensor is formed by housing a sensor element part 9 in an external case 10 having at least one plane while preventing the plane provided on the external case 10 from running parallel to the longitudinal direction of a lead terminal 22 in which a magnet 4 moves. The plane of the external case 10 is formed so as to prevent the direction in which the magnet 4 moves from running parallel to a bottom surface of the external case 10, assuming, for example, that the plane is the bottom surface of the external case 10 in which the impact sensor 1a is mounted on a substrate for an electronic control circuit of a movable body. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an impact sensor, and more particularly to an impact sensor suitable for a mobile device such as an automobile airbag system (hereinafter also simply referred to as an airbag) and a seat belt pretensioner system.

  In general, this type of impact sensor uses an inertial force acting on an object that is moving at high speed, so that the acceleration caused by impact such as collision or sudden braking is greater than a set value. It is configured to detect the change and output it as an electrical signal by opening and closing a switch sensitive to the change of the magnetic field.

  When detecting the acceleration, if the impact sensor is used as an airbag system for an automobile or the like, it is energized to an electronic control circuit that operates an inflator (gas generator) for explosively inflating the bag (balloon shape). It has a structure to do.

  The board of the electronic control circuit on which the impact sensor is mounted is disposed so as to be parallel to the direction in which the acceleration occurs, and the impact sensor faces the direction in which the acceleration occurs and the direction in which the change in the magnetic field is detected. In such a manner, it is arranged and mounted on the substrate.

  5A and 5B are views showing the external appearance of a conventional impact sensor. FIG. 5A is a perspective view, FIG. 5B is a view from the top, and FIG. 5C is a view from the front. FIG. 5D is a view as seen from the right side, and shows the impact sensor 1 configured by providing a rectangular parallelepiped outer case 10 with external connection terminals 11 connected to a substrate of an electronic control circuit.

  FIG. 6 is an enlarged cross-sectional view of the impact sensor, and shows an enlarged cross-sectional view of the side surface at the position of FIG.

  The impact sensor 1 includes a contact portion 20 made of a ferromagnetic metal material that opens and closes in response to a change in a magnetic field and an inert gas (not shown) sealed in a glass tube 21 and joined to the contact portion 20. A reed switch 2 in which a lead terminal 22 made of a ferromagnetic material is drawn out from the glass tube 21, a cylindrical tube 3 made of a nonmagnetic synthetic resin material so as to wrap the outer periphery of the reed switch 2, and a tube 3 An annular magnet 4 that is fitted and applies a magnetic field change to the contact portion 20, and a magnet that receives an acceleration a greater than or equal to a predetermined value due to an impact caused by an end being brought into contact with one bottom surface of the magnet 4. 4 is housed in a cylindrical interior case 6, and the other bottom surface of the magnet 4 is arranged at the end of the interior case 6. Then, the magnet 4 contacts the back stopper 7 that sets the initial position, and the other end of the spring 5 is disposed at the other end of the interior case 6 and contacts the front stopper 8 that determines the moving range of the magnet 4. Thus, the sensor element unit 9 is configured.

  The sensor element portion 9 is housed in the outer case so that the longitudinal direction of the lead terminal to which the magnet 4 moves is parallel to the direction of the acceleration a.

  The lead terminal 22 drawn out from the sensor element portion 9 is connected to an external connection terminal 11 provided in the exterior case 10 by a resistance welding method or the like (not shown), and is housed in the exterior case 10 to store the impact sensor 1. Constitute.

  As shown in FIG. 6, the impact sensor 1 moves to the front stopper 8 side against the spring 5 against the spring 5 by the force acting on the magnet 4 when the acceleration a occurs in the direction of the arrow as shown in FIG. The action of the magnetic field acting on the contact portion 20 of the reed switch 2 is strengthened, and the contact portion 20 is closed (short-circuited).

  When the acceleration a disappears due to the magnet 4 colliding with the front stopper 8 or the like, the magnet 4 is pushed back toward the back stopper 7 by the restoring force of the spring of the spring 5 to the contact portion 20 of the reed switch 2. The force applied by the magnetic field is weakened, and the contact portion 20 performs an operation of being in an open (open) state by being restored by the elastic force of the metal material of the contact portion 20.

  FIG. 7 is a diagram showing the force acting on the center of gravity of the magnet of a conventional impact sensor, wherein the horizontal direction is the X axis and the vertical (gravity) direction is the Y axis.

  The force F0 generated at the center of gravity g of the magnet due to an automobile collision or the like is that the mass of the magnet is m, the acceleration generated in the magnet is a, the coefficient of friction and the load acting between the tube and the magnet are μ and p, and the spring of the spring If the constant is k and the distance the spring is contracted is L, the following equation (1) is obtained.

  F0 = ma− (μp + kL) (1)

  In this case, the force mG that acts on the center of gravity g of the magnet due to the gravity G is a direction that is orthogonal to the direction of the force ma that acts on the magnet due to the acceleration a, and therefore does not become a force that acts in the direction in which the magnet moves.

  In the case of the conventional impact sensor described above, in order to adjust the impact sensitivity according to the customer's required specifications, specifications such as the mass, material, and shape of the magnet, specifications such as the spring constant, material, and shape of the spring, Alternatively, it is necessary to change the specifications such as the shape dimensions of the tube, the interior case, and each stopper, and it is necessary to collect the sensor element design and various components for each customer's required specifications.

  As a means for solving the above problem, there is a technique for adjusting the sensitivity of an impact sensor by using two reed switches so that the contacts are arranged symmetrically or asymmetrically on the central axis of the magnet. It is disclosed.

  However, since the impact sensor of Patent Document 1 uses two reed switches, it is difficult to reduce the size by increasing the outer shape of the tube and increasing the size of the magnet, the spring, the case, and the like. The structure of the impact sensor is complicated because the detection time is adjusted by using the direction of one contact.

JP 2002-31645 A

  As described above, in order to adjust the detection time of acceleration due to impact in the conventional impact sensor, it is necessary to individually select the specifications of the members constituting the impact sensor such as magnets, springs, tubes, etc. There is a problem that the constituent members cannot be shared.

  The technical problem of the present invention is to provide an impact sensor that can adjust the detection time of acceleration without changing the specifications of the components that constitute the impact sensor.

  The present invention includes a reed switch having a lead terminal having a contact portion that opens and closes in response to a change in a magnetic field, a tube that wraps the reed switch, and a magnet that moves in parallel in the longitudinal direction of the reed switch. A sensor element portion in which a spring for biasing the magnet, a back stopper for setting an initial position of the magnet, and a front stopper for stopping the movement of the magnet are housed in an interior case have at least one plane. An impact sensor housed in an exterior case, where the plane provided on the exterior case is, for example, the bottom surface of the exterior case mounted on the substrate of the electronic control circuit of the moving body, that is, the longitudinal direction of the lead terminal, that is, the magnet The moving direction is not parallel to the bottom surface of the outer case.

  By mounting such an exterior case on the electronic control circuit of the moving body, it is possible to incline the longitudinal direction of the lead terminal so that the board of the electronic control circuit mounted on the moving body is not parallel to the magnet. The impact sensor capable of adjusting the sensitivity of acceleration can be obtained by utilizing the action of the acting gravity.

  The sensor element portion can be configured by using the same sensor element as that used in a conventional impact sensor.

  In addition, it is preferable to have a storage part provided with the latching | locking part or the group of a latching | locking part which fits and latches a sensor element part in an exterior case.

  Furthermore, it is preferable that the storage portion has a locking portion or a set of locking portions capable of setting a plurality of angles formed by the plane of the outer case and the longitudinal direction of the lead terminal.

  By providing a plurality of locking portions or sets of locking portions, the angle formed by the plane of the exterior case and the longitudinal direction of the lead terminal, that is, the inclination of the sensor element portion can be easily changed.

  Further, by providing a locking portion in which the plane of the outer case and the longitudinal direction of the lead terminal are parallel, the conventional use state in which no inclination is given, that is, the impact sensor is a plane provided in the outer case. It is also possible to configure so that the longitudinal direction of the lead terminal is parallel.

  FIG. 1 shows the force acting on the magnet of the impact sensor of the present invention, and FIG. 1 (a) shows the case where the longitudinal direction of the lead terminal where the magnet moves is tilted downward with respect to the direction in which the acceleration occurs. FIG. 1B is a diagram when the longitudinal direction of the lead terminal in which the magnet moves is tilted upward with respect to the direction in which acceleration occurs, and the horizontal direction is the X axis and the vertical (gravity). The direction is the Y axis.

  The force F1 generated at the center of gravity g of the impact sensor of FIG. 1 (a) is that the mass of the magnet is m, the acceleration caused by the collision of the moving body is a, the gravitational acceleration is G, and acts between the tube and the magnet. When the friction coefficient and load are μ and p, the spring constant of the spring and the contracted distance are k and l, and the angle between the direction in which the acceleration a occurs and the direction in which the magnet moves is θ, the following equation (2) It is expressed as follows.

  F1 = ma · sin (90−θ) + mG · sin θ− (μp + kl) (2)

  Similarly, the force F2 generated at the center of gravity g of the magnet of the impact sensor in FIG. 1B is represented by m as the mass of the magnet, a as the acceleration caused by the collision of the moving body, G as the gravitational acceleration, The friction coefficient and the load acting between them are μ and p, the spring constant of the spring and the contracted distance are k and l, and the angle between the direction in which the acceleration a occurs and the direction in which the magnet moves is θ, It is expressed as 3).

  F2 = ma · sin (90−θ) −mG · sin θ− (μp + kl) (3)

  The direction of the vector generated by gravity G is the same direction (+) as the vector generated in the magnet by acceleration when the longitudinal direction of the lead terminal in which the magnet moves is downward with respect to the direction in which acceleration occurs, and the magnet moves When the longitudinal direction of the lead terminal is upward, the direction opposite to the vector generated by acceleration (-) is obtained.

  Accordingly, by providing the magnet so that the direction in which the magnet moves is inclined with respect to the direction in which the acceleration occurs, the sensitivity can be adjusted without changing the parts that constitute the sensor element portion.

  According to the present invention, a reed switch including a lead terminal having a contact portion that opens and closes in response to a change in a magnetic field, a tube that wraps the reed switch, and an outer peripheral portion of the tube that is parallel to the longitudinal direction of the lead terminal. At least a sensor element portion in which an interior case is housed, a magnet for moving the magnet, a spring for biasing the magnet, a back stopper for setting the initial position of the magnet, and a front stopper for stopping the movement of the magnet There is obtained an impact sensor housed in an exterior case having one plane, wherein the plane of the exterior case and the longitudinal direction of the lead terminal on which the magnet moves are not parallel.

  According to the present invention, it is possible to obtain an impact sensor characterized in that the exterior case has a storage portion having a locking portion or a set of locking portions into which the sensor element portion is fitted.

  According to the present invention, the storage portion includes a plurality of the locking portions or a set of locking portions, and the flat surface of the outer case and the lead move when the sensor element portion is fitted. An impact sensor is obtained in which the angle formed by the longitudinal direction of the terminal is different for each of the locking portions or the set of locking portions.

  According to the present invention, when the impact sensor is mounted on a movable body, the impact sensor is installed so that the plane of the exterior case and the acceleration direction generated in the movable body are parallel to each other. A method is obtained.

  According to the present invention, it is possible to provide an impact sensor capable of adjusting the detection time without changing the specifications of the parts constituting the impact sensor.

  The impact sensor of the present invention is configured such that the sensor element portion is housed in an exterior case having at least one plane, and the plane of the exterior case and the moving direction of the magnet provided in the sensor element portion are not parallel. .

  For example, if the impact sensor is the bottom surface of the exterior case mounted on the substrate of the electronic control circuit of the moving body, the longitudinal direction of the lead terminal to which the magnet moves is not parallel to the bottom surface of the exterior case. Configure as follows.

  The sensor element has a contact portion made of a ferromagnetic material that opens and closes in response to a change in the magnetic field, and a lead terminal made of a ferromagnetic material in which an inert gas is sealed in the glass tube and joined to the contact portion. A reed switch, a cylindrical tube made of a non-magnetic synthetic resin material that wraps around the outer periphery of the reed switch, an annular magnet that is fitted into the tube and changes the magnetic field at the contact portion, and an impact A spring for energizing the magnet along the outer peripheral surface of the tube when it receives an acceleration of a predetermined value or more due to the occurrence of is stored in the interior case.

  Further, a back stopper for setting the initial position of the magnet is brought into contact with one end portion of the interior case, and a spring for energizing the magnet and a moving range of the magnet are set at the other end portion of the interior case. The front stopper is in contact.

  In addition, the component which comprises a sensor element part can be used even if it is a thing of any specification, if it is conventionally used.

  Here, as the material of the parts constituting the sensor element part, the rhodium treated contact is used for the reed switch, and polybutylene terephthalate is used for the tube, back stopper, front stopper, interior case, exterior case and lid. The magnet is a plastic magnet (6 nylon ferrite magnet), the spring is a coil spring made of non-magnetic stainless steel SUS304, and the external connection terminal is a tinned copper wire for electrical use. Used.

  In addition, the tube, the front stopper, and the interior case may be manufactured by using polybutylene terephthalate to form an integral structure by molding.

  The exterior case has a structure having a storage portion including a locking portion or a set of locking portions that fit together using the outline of the sensor element portion.

  The storage portion of the outer case includes a plurality of the locking portions or sets of locking portions, and is provided in the bottom surface of the outer case and the sensor element portion when the sensor element portion is fitted. The angle formed with the longitudinal direction of the lead terminal of the reed switch through which the magnet moves is different from each other in each of the locking portion or the set of locking portions. Here, the set of locking portions is used when a plurality of locking portions are used in order to stably store the sensor element portion, and it is preferable that two to eight locking portions are set as one set. .

  In addition, the plurality of the locking portions or the set of locking portions are such that the angle formed between the bottom surface of the outer case and the longitudinal direction of the outer peripheral portion of the tube provided in the sensor element portion is parallel. You may provide the structure which becomes.

  In the impact sensor of the present invention, for example, a control circuit board of an airbag mounted on a moving body such as an automobile is arranged so as to be parallel to a direction in which acceleration occurs, and a bottom surface of an outer case is provided on the board. Install and use in parallel.

  Hereinafter, embodiments of the present invention will be described in detail using examples.

Example 1
FIG. 2 is a diagram for explaining an example of the impact sensor of the present invention, and shows an enlarged side sectional view.

  In the impact sensor of the present invention, a contact portion 20 (not shown in the following description showing the inside of a circle) and an inert gas (not shown) made of a ferromagnetic material that opens and closes in response to a change in a magnetic field and a glass tube 21. The lead terminal 22 made of a ferromagnetic material sealed in and joined to the contact portion 20 is drawn from the glass tube, and the non-magnetic synthetic resin material is wrapped around the outer periphery of the lead switch 2. A cylindrical tube 3, an annular magnet 4 that is fitted into the tube 3 to change the magnetic field to the contact portion 20, and the magnet 4 is attached to the tube 3 when an acceleration of a predetermined value or more is received due to an impact. A spring 5 that energizes along the outer peripheral surface of the inner case 6 is housed in the interior case 6, and is further disposed on the end surface of the interior case 6 to set the initial position of the magnet 4. Pas 7 is in contact, to constitute a sensor element portion 9 to be deployed on the other end face of the inner case 6 crash engagement was sealed movement of the magnet 4 contacts the front stopper 8 defining the magnet moving range.

  The sensor element portion 9 has an angle of 10 degrees, 20 degrees, and 30 degrees in the direction in which the magnet 4 of the sensor element section 9 moves downward and upward with respect to the plane of the bottom surface of the exterior case 10 in which the acceleration directions are parallel. So that each was tilted.

  The lead terminal 22 drawn out from the sensor element portion 9 is connected to the external connection terminal 11 provided in the outer case 10 by a resistance welding method (not shown), and housed in the outer case 10 to constitute an impact sensor. .

  The reed switch 2 uses a rhodium contact made by NEC TOKIN. The tube 3, the inner case 6, the back stopper 7, the front stopper 8, and the outer case 10 are made of polybutylene terephthalate, and the magnet 4 is a plastic magnet. A coil spring made of nonmagnetic stainless steel SUS304 was used for the spring 5 (6 nylon ferrite magnet), and an annealed copper wire for the external connection terminal 11 was used.

  In addition, the sensor element part 9 accommodated in the exterior case 10 was bonded and fixed to the exterior case 10 with an adhesive (not shown).

  FIG. 3 is a graph showing an acceleration test result of the impact sensor of the present invention.

In the acceleration test of the impact sensor, the detection time is confirmed by applying an acceleration of 10 m / s ² using a sine half-wave impact tester.

  Data A10, A20, A30, B10, B20, B30, and C indicate detection times by the acceleration test, and are plotted using normal probability paper.

  The data A10 is provided with an inclination of 10 degrees downward in the direction in which the magnet moves with respect to the acceleration direction a, and A20 is provided with an inclination of 20 degrees downward in the direction in which the magnet moves with respect to the acceleration direction a. Is provided with an inclination of 30 degrees downward in the direction in which the magnet moves with respect to the acceleration direction a, B10 is provided with an inclination of 10 degrees in the direction in which the magnet moves with respect to the acceleration direction a, and B20 is The detection time when the direction in which the magnet moves with respect to the acceleration direction a is 20 degrees upward is provided, and B30 is the detection time when the direction in which the magnet moves with respect to the acceleration direction a is provided 30 degrees upward. is there.

  Data C shows the detection time by the acceleration test in the configuration of the conventional impact sensor shown in FIG. 6, and the detection time is plotted using normal probability paper.

  As compared with the detection time of the conventional impact sensor 1 shown in FIG. 6, when the inclination of the sensor element portion is directed downward with respect to the acceleration direction, in A10, the detection time is accelerated by about 11.4% on average. In A20, the detection time can be increased by 17.8%. In A30, the detection time can be adjusted by about 21.4% by average, and the inclination of the sensor element portion can be increased. In the case of B10, about 15.3% detection time can be delayed by an average value in B10, 29.7% detection time can be delayed in B20, and about 50% detection by an average value in B30. The time could be adjusted late.

  Thus, by arranging the direction in which the magnet moves with respect to the direction in which the acceleration occurs, the impact sensor of the present invention can adjust the detection time.

(Example 2)
FIG. 4 is a diagram for explaining an example of the impact sensor of the present invention, and shows an enlarged side sectional view. The outer case 10a has a storage portion 12a in which the direction in which the magnet of the sensor element portion (not shown) moves with respect to the direction in which the acceleration a occurs is inclined 20 degrees downward, and an inclination 20 degrees upward. The storage part 12 which can be stored in either the storage part 12b or the parallel storage part 12c is provided.

  The storage portion 12a includes a set of locking portions 13a that fit the outer corners of the sensor element portion, and the storage portion 12b similarly has a set of engagement portions that fit the outer corner portions of the sensor element portion. The stopper portion 13b is provided, and the storage portion 12c is configured to include a set of locking portions 13c for fitting the outer corners of the sensor element portion.

  The inclination of the impact sensor can be easily changed by providing the outer case 10a with a storage portion 12 that can be stored at any of a plurality of different angles, and the detection time similar to the result shown in FIG. I was able to.

  Therefore, an impact sensor that can adjust the detection time of acceleration due to impact without changing the members constituting the impact sensor can be obtained.

  As mentioned above, although the form of this invention was demonstrated using the Example, this invention is not restricted to these Examples, Even if there is a design change of the range which does not deviate from the summary of this invention, it is in this invention. included. That is, various changes and modifications that can be naturally made by those skilled in the art are also included in the present invention.

  By using the impact sensor of the present invention, an impact sensor capable of adjusting the detection time without changing the material constituting the impact sensor can be supplied to an automobile airbag system or the like.

The figure which shows the force which acts on the magnet of the impact sensor of this invention. FIG. 1A is a diagram illustrating a case where the longitudinal direction of a lead terminal in which a magnet moves is tilted downward with respect to a direction in which acceleration occurs. FIG. 1B is a diagram showing a case where the longitudinal direction of the lead terminal in which the magnet moves is tilted upward with respect to the direction in which the acceleration occurs. The figure explaining an example of the impact sensor of this invention. The graph which shows the acceleration test result of the impact sensor of this invention. The figure explaining the exterior case of the impact sensor of this invention. The figure which shows the external appearance of the conventional impact sensor. FIG. 5A is a perspective view. FIG.5 (b) is the figure seen from the upper surface. FIG.5 (c) is the figure seen from the front. FIG.5 (d) is the figure seen from the right side surface. The cross-sectional enlarged view of an impact sensor. The figure which shows the force which acts on the gravity center of the magnet of the conventional impact sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Impact sensor 2 Reed switch 3 Tube 4 Magnet 5 Spring 6 Interior case 7 Back stopper 8 Front stopper 9 Sensor element part 10, 10a Exterior case 11 External connection terminal 12a, 12b, 12c Storage part 13a, 13b, 13c Locking part 20 Contact portion 21 Glass tube 22 Lead terminal A10 Data A20 Data A30 Data B10 Data B20 Data B30 Data C Data

Claims (4)

  A reed switch having a lead terminal having a contact portion that opens and closes in response to a change in a magnetic field, a tube that wraps the reed switch, a magnet that moves an outer peripheral portion of the tube in parallel with a longitudinal direction of the lead terminal, and An exterior having at least one plane, a spring for energizing the magnet, a back stopper for setting an initial position of the magnet, and a sensor element portion in which a front stopper for stopping movement of the magnet is housed in an interior case An impact sensor housed in a case, wherein the plane of the exterior case and the longitudinal direction of the lead terminal to which the magnet moves are not parallel.   The impact sensor according to claim 1, wherein the outer case includes a storage portion having a locking portion into which the sensor element portion is fitted.   The storage portion includes a plurality of the locking portions, and when the sensor element portion is fitted, an angle formed between the flat surface of the outer case and the longitudinal direction of the lead terminal to which the magnet moves is the locking The impact sensor according to claim 1, wherein each of the parts is different.   4. The apparatus according to claim 1, wherein when the impact sensor is mounted on a moving body, the shock sensor is installed such that the plane of the outer case and an acceleration direction generated on the moving body are parallel to each other. 5. How to use the shock sensor.

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