1. Field of the Invention
The present invention relates to a tilt detector, and more particularly, to a tilt detector that outputs an electrical signal indicating a tilt condition.
2. Description of Related Art
In some applications, tilt detectors are used together with alarms for automobiles, safes and the like as theft prevention systems, in which the tilt detector is used to sense tilt or vibration from unauthorized attempted access, thus triggering the alarm.
In some other applications, tilt detectors are linked to switches or breakers and installed in electric heaters or gas burners as secondary fire prevention mechanisms. The tilt detectors trigger the switch or breaker to cut off operation of the appliances if the appliances are upset during an earthquake, for example.
Such conventional tilt detectors have typically used spring power. However, a disadvantage of such spring-powered tilt detectors is that they sometimes generate false alarms, that is, are triggered by the shock of vibration even in the absence of a tilt.
As a consequence, tilt detectors employing a combination of magnets and magnetoelectric transducers have come into widespread use. The advantages of such tilt detectors lie in their ability to reduce the number of false positive readings generated by the typical spring-powered tilt detector and by the high degree of accuracy and precision such tilt detectors afford.
A cross-sectional view of a typical conventional magnetic tilt detector is shown, for example, in FIG. 1, reproduced from Japanese Laid-Open Patent Application No. 8-261758.
As shown in the diagram, the tilt detector 5a supports 1a and 1b form an upwardly concave surface area portion 2a, along which a permanent magnet 3a moves freely, with magnetic detectors 4a positioned so as to detect the permanent magnet 3a. 
In such a tilt detector 5a, a second, downwardly convex portion 2b coaxial with the upwardly concave portion 2a is spaced evenly opposite such concave portion 2a by a certain distance. The permanent magnet 3a is inserted in the curved slot formed between the surfaces of the two portions 2a and 2b, with at least three magnetic detectors positioned around the edges of the downwardly convex portion 2b. The permanent magnet 3a consists of a core covered by a resin compound, with the curved portions 2a and 2b being made of metal plates. A lubricating oil is inserted as necessary in the space between the two portions, to allow the permanent magnet 3a to slide more smoothly.
Additionally, FIG. 2 is a cross-sectional view of a conventional tiltmeter, reproduced, for example, from Japanese Laid-Open Patent Application No. 9-501498.
As shown in FIG. 2, a tiltmeter 5b uses a spherical base element 7 that contains a magnet 3b suspended in an inert fluid 6, such that the magnet 3b generates an imbalance in weight distribution as it moves.
The tiltmeter 5b maintains the uneven weight distribution with respect to the pull of gravity on the base element 7, with the position of the magnet 3b on the base element 7 with respect to a housing 8 being detected by a pair of symmetrically disposed Hall effect sensors 4b mounted on the housing 8. Since the magnet 3b is disposed so as to rotate freely, for example, detection in two directions is possible.
However, a drawback of the conventional magnetic tilt detectors and tiltmeters described above is that, in instances in which the tilt detector is placed not on a level surface but on a tilted surface, it becomes more difficult to obtain precise and accurate detection of the degree of tilt because the relative positions of the magnet (which is trying to attain a perpendicular position) and the magnetic detectors (which are aligned with the tilted surface) have changed and the gap between the two has widened. An added drawback of such conventional magnetic tilt detectors and tiltmeters is that the magnet either slides along another member or moves through a fluid, thus slowing the response time to a tilt.
Additionally, it should be noted that the conventional tilt detector has a further drawback in that the structure of such a device imposes sharp limits on the range through which tilt can be detected.
Accordingly, it is an object of the present invention to provide an improved and useful tilt detector in which the above-described disadvantage is eliminated.
A further and more specific object of the present invention is to provide an improved and useful tilt detector in which a tilt condition can be sensed precisely and accurately over a wide range of angles.
Another, further and more specific object of the present invention is to provide an improved and useful tilt detector in which precise and accurate tilt readings can be provided rapidly.
Still another, further and more specific object of the present invention is to provide an improved and useful tilt detector capable of providing prompt, precise and accurate readings even when necessity requires that it be mounted on an inclined surface.
The above-described objects of the present invention are achieved by a tilt detector comprising:
a magnet;
a plurality of magnetoelectric transducers;
a container; and
a mounting member for mounting the magnet,
the mounting member rotatably supported within the container by a bearing mechanism,
the plurality of magnetoelectric transducers being mounted on the container,
the tilt detector detecting a tilt condition from signals generated by the magnetoelectric transducers due to changes in a relative position of the magnet and the magnetoelectric transducers as the mounting member rotates within the container.
According to this aspect of the invention, the mounting member is rotatably supported by the bearing mechanism, eliminating the possibility of vertical blurring present with those conventional tilt detectors that rely solely on fluid-encapsulation of the mounting member because the bearing mechanism maintains the mounting member at a precise predetermined axis point, thus providing improved precision and accuracy in detecting tilt positions. Additionally, by providing the magnet on a mounting member that is free to rotate, a tilt can be sensed over a wide range of angles, and the low resistance offered by the bearing mechanism to the movement of the mounting member enables the tilt detector to provide rapid readings of a tilt condition.
Additionally, the above-described objects of the present invention are also achieved by the tilt detector as described above, further comprising a weight mounted on the container.
According to this aspect of the invention, by arranging the magnet and the weight at an appropriate distance from each other at an initial inclined condition, it is possible to adjust the distance separating the magnet and the magnetoelectric transducers as desired, with the result that a tilt can be detected precisely and accurately even when the tilt detector is mounted on an inclined surface to begin with.
According to another aspect of the present invention, the space between the interior surface of the container and the exterior surface of the mounting member is filled with a lubricating fluid so as to immerse the bearing mechanism in the fluid, thus obtaining the advantage of retarding sharp movements of the mounting member (caused, for example, by the shock of impact to the target object) together with the stability of positioning of the mounting member within the container provided by the use of the bearing mechanism. The result is that it becomes possible to reduce the number of false alarm readings caused by momentary and unstable high tilt detection readings, thus improving overall tilt detection accuracy.