JP2007139485A - Pendulum type sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a practical pendulum type sensor which can arbitrarily set the natural frequency of a pendulum body within a range from a few tenth of a Hz to ten-odd Hz, especially, from 1 Hz to 12 Hz and achieve downsizing and lightweight. <P>SOLUTION: The pendulum type sensor comprises a weight body having mass distribution in a housing, the pendulum body in which the center of gravity and rotation axis center of the weight body are provided at a predetermined distance, and a means for detecting the rotational position or angle of the pendulum body. The pendulum type sensor detects the rotational position or angle of the pendulum body by the detection means provided in the housing and the pendulum body. The natural frequency of the pendulum body is set to be 1.0 Hz to 12 Hz, and r/L≥1, more preferably, r/L≥3, wherein r is the average mass distribution equivalent radius of the mass distribution of the weight body, and L is the distance between the center of gravity and rotation axis center of the weight body. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pendulum type sensor that can detect low-frequency vibration generated in an earthquake or a large building (such as a high-rise building or a bridge) with high sensitivity, and in particular, the low-frequency vibration has a frequency of 1 to 12 Hz. The present invention relates to a pendulum type sensor that can detect the sensor with high sensitivity and high accuracy and can be reduced in size and weight.

  In general, the frequency of seismic waves generated by an earthquake and the vibration frequency of the large building caused by the seismic waves or strong winds during a typhoon are 0. It is known that the frequency is very low in the range of several Hz to several tens of Hz.

  In recent years, awareness of disaster prevention against natural disasters such as earthquakes and typhoons has increased, and there is a highly accurate and highly practical system that can quickly acquire necessary disaster prevention information by catching information on the earthquake waves and vibrations of large buildings. There is a demand for a vibration sensor that is compact, lightweight, highly sensitive, highly accurate, and highly practical.

  On the other hand, the pendulum type sensor has the moment of inertia due to the mass distribution of the weights installed in the casing, and the moment of inertia or L when the distance between the center of gravity of the weights and the rotation axis center of the pendulum is L. Can be arbitrarily set, the natural frequency of the pendulum body can be set arbitrarily. If the frequency is in the range of several Hz to several tens of Hz, there is a possibility that the vibration sensor can be small, light, highly sensitive, highly accurate, and highly practical.

Conventionally, a pendulum type sensor using the pendulum body has been developed as an inclination sensor for detecting an inclination angle of a moving body such as a vehicle disclosed in Patent Document 1 and Patent Document 2.
JP 2005-83957 A JP-A-2005-49321

  Since the conventional pendulum type sensor has been developed as the tilt sensor, an invention for increasing the rotational sensitivity of the pendulum body is disclosed. However, the inertia moment, the L and the natural frequency of the pendulum body are 0. A specific method for setting the frequency range from several Hz to several tens Hz is not clearly described. In particular, the method is not clearly shown in the 1 Hz to 12 Hz range which is important for the seismic wave or the like.

  Further, the natural frequency of the conventional pendulum type sensor is set to 0. In order to obtain a low frequency in the range of several Hz to several tens of Hz, in particular, in order to obtain the important 1 Hz to 12 Hz range in the seismic wave, it is necessary to lengthen the L. As a result, the pendulum body becomes large, and the pendulum becomes large. There is a problem that it is difficult to reduce the size and weight of the entire sensor. Therefore, it is very difficult to apply the sensor as a highly practical vibration sensor for obtaining information on the seismic wave or the vibration of the large building.

  The present invention has been made to solve the above-mentioned problems, and the natural frequency of the pendulum body is expressed by the following equation. An object of the present invention is to supply a highly practical pendulum type sensor that can be arbitrarily set in the range of several Hz to several tens of Hz, particularly in the range of 1 Hz to 12 Hz, and that can reduce the size and weight of the pendulum type sensor.

In order to solve the above-described problem, a pendulum sensor according to the present invention includes at least a weight body having a mass distribution in a housing, and a pendulum body provided at a distance in which a center of gravity position and a rotation axis center of the weight body are set. And a pendulum type sensor for detecting the rotation position or angle of the pendulum body by a detection means installed on the housing and the pendulum body, The natural frequency of the pendulum body is set from 1.0 Hz to 12 Hz,
If the average mass distribution equivalent radius of the mass distribution of the weight is r, and the distance between the center of gravity of the weight and the center of the rotation axis is L,
r / L ≧ 1 (1)
More desirably, r / L ≧ 3 (2)
It is set as the structure which is.
Here, the average mass distribution equivalent radius r means a radius r of a circular weight body having an inertia moment equivalent to the inertia moment of the weight body having a mass distribution.

  In the pendulum type sensor of the present invention, the average mass distribution equivalent radius r is in the range of 0.5 mm to 10 mm, and more preferably in the range of 1.0 mm to 7.0 mm.

  In the pendulum type sensor of the present invention, it is preferable that the distance L between the center of gravity of the weight body and the center of the rotation axis is in the range of 0.1 mm to 3.3 mm, more preferably 0.2 mm to 2.0 mm. The configuration is a range.

  In the pendulum sensor of the present invention, the weight body and the pendulum body are made of the same member, and the center of the rotation axis is provided in the weight body.

  In the pendulum type sensor according to the present invention, the weight body is flat and has a circular shape, a polygonal shape, an elliptical shape, or a shape similar to these.

  In the pendulum type sensor according to the present invention, the detection means includes a magnetic flux generation means provided on the weight body and a magnetic sensor that detects a change in the magnetic flux.

  In the pendulum type sensor according to the present invention, the magnetic flux generating means is a permanent magnet of the whole or a part of the weight body, and the magnetic sensor is composed of at least one hall element.

  In the pendulum type sensor of the present invention, one or a plurality of the partial permanent magnets are provided, and the thickness and density thereof are substantially equal to the weight body.

  In the pendulum type sensor of the present invention, a plurality of the permanent magnets are arranged symmetrically with respect to a straight line connecting the rotating shaft and the position of the center of gravity.

In the pendulum type sensor of the present invention, one or a plurality of the permanent magnets having a density different from the density of the weight body is provided, and a distance between the center of gravity of the weight body and the center of the rotation axis is rd. When the average mass distribution equivalent radius is Ld,
rd / Ld ≧ 1 (3)
More desirably, rd / Ld >> 3 (4)
It is set as the structure which is.

According to the pendulum type sensor of the present invention, at least a weight body having a mass distribution in the housing, a pendulum body provided at a distance in which a gravity center position and a rotation axis center of the weight body are set, and the pendulum body Means for detecting the rotational position or angle of the pendulum body, and detecting the rotational position or angle of the pendulum body by means of detection means installed on the housing and the pendulum body, wherein the natural vibration of the pendulum body The number is set from 1.0 Hz to 12 Hz,
If the average mass distribution equivalent radius of the mass distribution of the weight is r, and the distance between the center of gravity of the weight and the center of the rotation axis is L,
r / L ≧ 1 (1)
More desirably, r / L ≧ 3 (2)
By doing so, the effect of reducing the natural frequency of the pendulum body by the moment of inertia of the weight body is increased, and the design of a very low natural frequency in the range of 1.0 Hz to 12 Hz can be easily performed. As apparent from the formula (1) and in particular, the formula (2), the length of the pendulum body is almost the same as the length of the weight body, that is, without increasing the length of the pendulum, It is possible to reduce the natural frequency while reducing the size. Furthermore, in a very low frequency region where the natural frequency f ₀ such as a seismic wave is 5 Hz or less, the formula (2) is effective, and the pendulum type sensor can be reduced in size and weight while having a very low natural frequency. .

  Furthermore, by setting the average mass distribution equivalent radius r in the range of 0.5 mm to 10 mm, more preferably in the range of 1.0 mm to 7.0 mm, the natural frequency in the range of 1.0 Hz to 12 Hz. The total length of the pendulum body can be set to 20 mm or less, and in particular, the total length of the pendulum body can be set to 10 mm or less under the condition of the formula (2).

  Further, by setting the distance L between the center of gravity of the weight body and the center of the rotation axis in the range of 0.1 mm to 3.3 mm, more preferably in the range of 0.2 mm to 2.0 mm. The total length of the pendulum body having a natural frequency in the range of 0.0 Hz to 12 Hz can be set to 20 mm or less, and in particular, the total length of the pendulum body can be set to 10 mm or less under the condition of formula (2), and the entire pendulum type sensor can be made very small. .

  Further, since the weight body and the pendulum body are made of the same member and the center of the rotation axis is provided in the weight body, the weight body and the pendulum body can be formed of the same part. The structure of the pendulum body is prevented from becoming complicated, the overall length can be shortened, the size of the pendulum sensor can be reduced, and the processing accuracy of the r and the L can be easily improved. The frequency can be set with high accuracy. In addition, the number of parts can be reduced and the cost of the pendulum sensor can be reduced.

  Further, the weight is flat, circular, polygonal, elliptical, or a shape approximate to these, so that the maximum moment of inertia due to mass distribution (roundness) in the weights having the same mass. Or a value close to the maximum value can be obtained, so that the total length of the pendulum body can be shortened in the weight set with the same natural frequency, and the pendulum sensor can be reduced in size and weight. In other words, the natural frequency can be easily reduced without changing the length of the pendulum body, that is, without increasing the size of the pendulum sensor.

  Furthermore, the detecting means is a magnetic flux generating means provided on the weight body and a magnetic sensor for detecting a change in the magnetic flux, so that in principle the distance between the pendulum body and the magnetic sensor is as close as possible. Therefore, it greatly contributes to the miniaturization of the pendulum type sensor. Further, the means for detecting the change in magnetic flux has an advantage that the detection sensitivity is improved as the distance is shorter.

  Further, the magnetic flux generating means is a permanent magnet provided on all or part of the weight body, and the magnetic sensor includes at least one hall element, so that the magnetism generating means of the weight body includes an electromagnet or the like. A mechanism is not necessary, and the Hall element can make a significant contribution to miniaturization of the pendulum type sensor by taking advantage of the fact that it can be easily miniaturized by making it a thin film element or the like. Furthermore, the detection by the Hall element can accurately measure the rotational position or angle of the pendulum body without depending on the speed and acceleration of the pendulum body. Therefore, the vibration frequency of the pendulum body and the amplitude of the angle can also be accurately measured. It is also possible to measure.

  Furthermore, one or a plurality of the permanent magnets are provided, and the thickness and density of the permanent magnets are substantially equal to the weight body, so that the weight body is equivalent to a uniform material, so that the natural frequency can be designed. In addition to improving the accuracy, it is possible to prevent the pendulum sensor from becoming large without changing the set natural frequency.

  Further, a plurality of the permanent magnets are installed symmetrically with respect to a straight line connecting the rotation axis and the position of the center of gravity, so that a magnetic flux distribution formed from the plurality of permanent magnets is in the straight line. Since it is line symmetric or point symmetric about one point on the straight line, the center of the magnetic flux distribution is always on the straight line, and the magnetic sensor and the Hall element in the casing are set at arbitrary positions. In addition, the rotational position or angle of the pendulum body can be accurately measured. Therefore, the magnetic sensor and the Hall element can be arranged at a position where the pendulum type sensor can be most miniaturized, which is effective for reducing the size and weight of the pendulum type sensor.

Further, when one or a plurality of the permanent magnets having a density different from the density of the weight body is provided, the distance between the center of gravity of the weight body and the center of the rotation axis is rd, and the average mass distribution equivalent radius is Let Ld be
rd / Ld ≧ 1 (3)
More desirably, rd / Ld >> 3 (4)
Thus, even if the density of the weight body and the density of the permanent magnet are different, the effect of reducing the natural frequency of the pendulum body due to the moment of inertia becomes large, and the natural vibration is very low in the range of 1.0 Hz to 12 Hz. A number of designs can be accepted. Further, as apparent from the formula (3) and particularly the formula (4), the length of the pendulum body is almost equal to the length of the weight body, that is, without increasing the length of the pendulum, that is, a pendulum type sensor. It is possible to reduce the natural frequency while reducing the size.

FIG. 1 is a schematic front sectional view of a pendulum type sensor according to the present invention.
FIG. 2 is a schematic side sectional view of FIG.

  1 and 2, a pendulum sensor 1 is rotated freely around a rotation axis center 4 of a weight body 3 on a housing 2 composed of two parts joined by a housing joint 51. It is clamped between the shaft 53 and the rotary bearing 55. Further, the weight body 3 has a mass distribution having an average mass distribution equivalent radius r7 centered on the gravity center position 5, and is installed at a position of a distance L6 between the gravity center position 5 and the rotation axis center 4, and the pendulum body as a whole. 8 is configured. Here, the average mass distribution equivalent radius r means the radius of a disk-shaped weight body having an inertia moment equivalent to the inertia moment of the weight body 3 having a mass distribution. 1 and 2, the weight body 3 is a regular disk, and the average mass distribution equivalent radius r7 is the radius of the weight body 3.

  Further, the housing 2 and the pendulum body 8 are provided with means 9 (for example, a permanent magnet 9a, a hall element 9b) for detecting the rotational position or angle of the pendulum body 8, and the rotational position or angle of the pendulum body 8 Is detected.

Here, the natural frequency f ₀ of the pendulum body 8 is set to 1.0 Hz to 12 Hz mainly generated in an earthquake or a large building (high-rise building, bridge, etc.), and the average mass distribution equivalent radius r7, The distance L6 between the center of gravity position 5 and the rotation axis center 4 is r / L ≧ 1 (1)
More desirably, r / L ≧ 3 (2)
It is comprised so that.
1 and 2, for the purpose of detecting seismic waves, the natural frequency f ₀ is set to 3.03 Hz (design value), and the measured value is set to about 3.0 Hz.
The average mass distribution equivalent radius r7 is 4 mm, and the distance L6 between the center of gravity position 5 and the rotation axis center 4 is 0.3 mm.
Therefore, r / L≈13.3.

  Here, the total length of the pendulum body 8 is a length obtained by adding a distance L6 between the center of gravity position 5 and the rotation axis center 4 to a diameter of the weight body 3, that is, a length twice the average mass distribution equivalent radius r7. 2 × r + L, since the distance L6 between the center of gravity position 5 and the rotation axis center 4 is 0.3 mm, the total length of the pendulum body 8 is 4 mm × 2 + 0.3 mm = 8.3 mm. The length of the weight 3 is approximately the length of 4 mm × 2 = 8 mm. Therefore, even if the means 9 for detecting the rotational position or angle of the pendulum body 8 is included, the entire pendulum sensor 1 can be a pendulum sensor having a size of 10 mm × 10 mm.

The size of the pendulum type sensor 1 is very small and light compared to other pendulum type sensors and vibration sensors around the natural frequency f ₀ = 3 Hz.

The configuration principle of the present invention will be described in detail with reference to FIGS.
Here, FIGS. 3 to 5 are diagrams for explaining the relationship among the weight body 3 having the inertial mass, the pendulum body 8, and the natural frequency f ₀ of the pendulum body 8.

First, FIG. 3 explains the operation of a general pendulum. The weight body 3 having the average mass distribution equivalent radius r7 is supported by the weight support part 57 at the center of gravity position 5 and the rotation axis center 4 and the distance L6 to the rotation axis center 4, and the pendulum body as a whole. 8 is constituted. The pendulum body 8 performs pendulum vibration along the rotation direction 61 around the vertical line 59 of the rotation axis center 4.
Here, it is assumed that the weight body 3 has a plate shape with a uniform thickness, and the weight support part 57 has a string or bar shape, and the mass can be almost ignored.

The natural period T of the pendulum body 8 shown in FIG.
^{T = 2π × √ {(L} 2 + r 2/2) / (g × L)} ... (5)
(5). Here, g is a gravitational acceleration (≈9.8 m / sec ² ).
Therefore, the natural frequency f ₀ of the pendulum body 8 is
f ₀ = 1 / T
From the relationship of (5) and
_{f 0 = 1 / {(2π} × √ {(L 2 + r 2/2) / (g × L)} ... (6)
(6).

Further, the pendulum body 8 shown in FIG. 4 has the same configuration as the pendulum body 8 shown in FIG. 3, but shows the case of an average mass distribution radius r7 = 0 mm of the weight body 3 and a complete mass point. The natural frequency f ₀ is given by the equations (5) and (6):
_{T 0 = 2π × √ (L} / g) ... (7)
f ₀ = 1 / (2π × √ (L / g) (8)
And is the most widely known equation as the period T and the natural frequency f ₀ of the pendulum body 8.

Here, looking at the equations (5) to (8), when trying to realize the pendulum body 8 having a natural frequency f ₀ of 12 Hz or less, which is mainly generated in the seismic wave or the large building, particularly a few Hz, The center of gravity of the weight body 3 and the rotation center 4 and the distance L become long, and it is very difficult to reduce the size and weight. For example, in the example of the natural frequency f ₀ = 3 Hz described in the best mode, when the weight 3 shown in the equation (8) is a mass point, the L is about 27.5 mm, Accordingly, the pendulum type sensor is 30 mm to 40 mm or more, and is very large and unpractical for mounting on a general electronic device, and a reduction in size and weight is strongly desired.

  Therefore, the present inventors have reexamined the expressions (5) and (6), and revisited the position of the center of gravity of the weight body 3, the rotation center 4, the average mass distribution equivalent radius r7, and the length of the pendulum body 8 in detail. Study was carried out.

The operation and configuration of the pendulum body 8 examined in FIG. 5 will be described.
The weight body 3 has an average mass distribution equivalent radius r7 similarly to the pendulum body 8 described with reference to FIGS. 3 and 4, and the rotation center 4 has a distance L6 between the gravity center position 5 and the rotation position 4 of the weight body 3. The pendulum body 8 as a whole is supported.
The feature of the pendulum body 8 in FIG. 5 is different from the pendulum body in FIGS.
This is a point where r ≧ L.

The feature of the pendulum body 8 is that the distance L6 between the gravity center position 5 of the weight body 3 and the rotating position 4 is very short or the average mass distribution equivalent radius r7 of the weight body 3 is very large. The effect of reducing the natural frequency f ₀ due to the moment of inertia of the weight body 3 expressed by the equation (6) is used to the maximum extent. At the same time, as apparent from FIG. 5, the distance L6 between the center of gravity position 5 of the weight body 3 and the rotating position 4 is very short and is included in the average mass distribution equivalent radius r7. It is possible to reduce the natural frequency f ₀ without increasing the height, which is extremely effective for downsizing the pendulum sensor 1.

Here, using the equation (6), the distance L6 between the center of gravity of the weight body 3 of the pendulum body 8 shown in FIG. 5 and the rotation center 4 and the average mass distribution equivalent radius r7 are used as parameters, and the natural frequency f. the results were determined _0, shown in the table of FIG. In the table, the natural frequency f ₀ was obtained with the row parameter being the average mass distribution equivalent radius r7 and the column parameter being the distance L6 between the center of gravity of the weight body 3 and the rotation center 4. The average mass distribution equivalent radius r7 is in the range of 0.5 mm to 10 mm, and the gravity center position, the rotation center 4 and the distance L6 of the weight body 3 are in the range of 0.1 mm to 3.3 mm.

From the table, the above-mentioned In each parameter range of the average mass distribution equivalent radius r7 and the weight element 3 of the position of the center of gravity and the center of rotation 4 and the distance L6 is a substantial number of the in the parameter natural frequency f ₀ is the seismic wave and large buildings in which primarily fall within the natural frequency f ₀ following 12Hz occurring, especially for 5Hz frequencies below the main vibration frequency of the seismic wave is within the parameter range. Further, looking at the r / L value, it is shown that the natural frequency f ₀ decreases as the r / L value increases.

Here, from the results of the table and including consider reducing the natural frequency f ₀ and at the same time to miniaturize the pendulum body 8 effectively,
First, when the average mass distribution equivalent radius r7 is in the range of 0.5 mm to 10 mm, the distance L6 between the center of gravity of the weight body 3 satisfying r / L ≧ 1 and the rotation center 4 is in the range of 0.1 mm to 3.3 mm. As is apparent from the above table, the natural frequency f ₀ can be set in the range of 1 Hz to 12 Hz. Here, it can be seen from the table that the same natural frequency f ₀ can be obtained by combining a plurality of the matrix parameters.

Further, when r / L ≧ 1, the rotation axis center 4 is in the weight body 3, and the effect of reducing the natural frequency f ₀ due to the moment of inertia of the weight body 3 can be used effectively. By selecting the combination that can shorten the length (= 2 × r + L) of the pendulum body 8 among the combinations of the plurality of matrix parameters, the natural frequency f ₀ in the range of 1 Hz to 12 Hz is The pendulum body 8 can be formed within a maximum length of about 20 mm, which can greatly contribute to the reduction in size and weight of the pendulum type sensor 1.

More preferably, by making r / L ≧ 3, the effect due to the moment of inertia is used more effectively, and the natural frequency f ₀ from 1 Hz to 12 Hz is within the combination of the matrix parameters in the table. By selecting the combination that can shorten the length of the pendulum body 8, the pendulum body 8 has a natural frequency f ₀ of 5 Hz or less, which is the main vibration frequency of the seismic wave. The length of the body 8 can be reduced to a few tens of mm or less at the maximum, and the pendulum type sensor 1 can greatly contribute to the reduction in size and weight.

The average mass distribution equivalent radius r7 is in the range of 1.0 mm to 7 mm, and the distance L6 between the center of gravity of the weight body 3 satisfying the range of r / L ≧ 1 and the rotation center 4 is in the range of 0.2 mm to 2 mm. And selecting the matrix parameter combination that can minimize the length of the pendulum body 8, the natural frequency f ₀ in the range of 1 Hz to 12 Hz is obtained from the table, and the length of the pendulum body 8 is The pendulum type sensor 1 can be formed in a small and light size of 10 mm square or less.

More preferably, the average mass distribution equivalent radius r7 is in the range of 1.0 mm to 7 mm, and the distance L6 between the center of gravity of the weight body 3 satisfying the range of r / L ≧ 3 and the rotation center 4 is 0.2 mm to 2 mm. By selecting the matrix parameter combination that can minimize the length of the pendulum body 8 from the table, the natural frequency f ₀ in the range of 1 Hz to 12 Hz is obtained from the table, and the length of the pendulum body 8 is The pendulum type sensor 1 can be achieved with a size of 10 mm square or less, and the pendulum type sensor 1 can be made extremely small and light.

In the embodiment of the present invention described with reference to FIGS. 1 and 2, the pendulum type sensor 1 as a whole can be reduced in size and weight to about 10 mm square even if it has a very low natural frequency f ₀ of 3 Hz.

1 and 2, the pendulum body 8 according to the present invention includes the weight body 3, the rotation center 4, the gravity center position 5, and the gravity center position of the weight body 3 and the rotation center 4. The distance L6 is set in the weight body 3, and the pendulum body 8 can be formed of the same member as the weight body 3. Therefore, the structure of the pendulum body 8 is prevented from becoming complicated, the overall length can be further shortened, and the pendulum sensor 1 can be downsized. In addition, the distance L6 between the center of gravity of the weight body 3 and the rotation center 4 and the machining accuracy of the mean mass distribution equivalent radius r7 is facilitated, can be set the natural frequency f ₀ of the pendulum member 8 is set with high accuracy. Moreover, the number of parts can be reduced and the cost of the pendulum sensor 1 can be reduced.

7 and 8 show schematic front sectional views of other embodiments of the pendulum type sensor 1 according to the present invention. FIG. 7 shows an embodiment in which the shape of the weight 3 is close to an elliptical plate, and FIG. 8 shows an embodiment in which the shape of the weight 3 is an octagonal plate. The basic configuration of the pendulum sensor 1 shown in FIGS. 7 and 8 is the same as that of the pendulum sensor 1 of the embodiment of FIG. 1, but each of the weights 8 is not a perfect circle. 7 and an average mass distribution equivalent radius r7 indicated by a dotted line in FIG.
In the embodiment of FIG. 7, a rotation stopper 63 for preventing the pendulum body 8 from rotating is installed.

The natural frequency f ₀ of each pendulum body 1 in the embodiment of FIGS. 7 and 8 was also set to 3 Hz as in the embodiment of FIG. Similarly, the distance L6 between the center of gravity of the weight 3 and the rotation center 4 is 0.3 mm, and the average mass distribution equivalent radius r is 4 mm.
As is apparent from the respective drawings, even if the weight 3 is formed in a shape close to the elliptical plate or a shape such as an octagonal plate, the length is the same as in the case of the round shape of the embodiment of FIG. Almost the same, the overall size of the pendulum sensor can be designed to be approximately the same, with the length and width being about 10 mm square and the thickness being 3 mm.

Therefore, by making the weight body 3 flat, circular, polygonal, elliptical, or a shape similar to these, the maximum value of the moment of inertia due to mass distribution in the weight 3 having the same mass ( (In the case of a perfect circle) or a value almost close to the maximum value can be obtained, so that the total length of the pendulum body 8 can be shortened in the weight body 3 having the same natural frequency f _0. 1 can be easily reduced in size, in other words, the natural frequency f ₀ can be easily reduced without changing the length of the pendulum body 8, that is, without increasing the size of the pendulum sensor 1.

  Furthermore, FIG. 9 shows a schematic front sectional view of another embodiment of the pendulum type sensor 1 according to the present invention. The basic configuration of the embodiment of FIG. 9 is the same as that of the embodiment of FIG. 1, and the means for detecting the rotational position or angle of the pendulum body 8 is a magnetism generating means 12 comprising a permanent magnet 11 provided in the weight body 3. And a magnetic sensor 14 composed of a Hall element 13. In the present embodiment, each of the magnetic generation means 12 and the magnetic sensor 14 is provided as one, but the weight 3 may be the magnetic generation means 12 composed entirely of the permanent magnet 11.

  As is apparent from the above embodiment, when the magnetism generating means 12 and the magnetic sensor 14 are used as means for detecting the rotational position or angle of the pendulum body 8, the distance between the pendulum body 8 and the magnetic sensor 14 is in principle. Can be made as close as possible, which greatly contributes to the miniaturization of the pendulum type sensor. Further, the means for detecting the change in magnetic flux has an advantage that the detection sensitivity is improved as the distance is shorter. Further, it is obvious that the means is effective also in the embodiment of the present invention shown in FIGS. 1, 7 and 8.

  Further, by using the permanent magnet 11 for the magnetic flux generating means 12 and the Hall element 13 for the magnetic sensor 14, a mechanism such as an electromagnet is not required for the magnetic generating means in the weight body 3, and the hall The element 13 can be formed into a thin film element such as an indium antimony (InSb) thin film formed by a vacuum deposition method, a sputtering method, or the like. Therefore, the Hall element 13 can be extremely miniaturized. This can greatly contribute to the downsizing. Further, the detection by the Hall element 13 can accurately measure the rotational position or angle of the pendulum body 8 independently of the speed and acceleration of the pendulum body 8 unlike the electromagnetic induction type sensor system. It is also possible to accurately measure the vibration frequency of the body 8 and the amplitude of the angle. It is obvious that this means is also effective in the embodiment of the present invention shown in FIGS. 1, 7 and 8.

9, the natural frequency f ₀ is 3 Hz, the average mass distribution equivalent radius rd 7 is 4 mm, the center of gravity position 5 and the rotation axis center 4 are the same as in the embodiment of FIG. The distance Ld6 to 0.3 mm can be designed so that the entire pendulum sensor 1 can be designed to have a size of 10 mm × 10 mm.

Further, in the embodiment of the present invention shown in FIG. 9, a brass plate having a thickness of 0.4 mm and a density of 8.5 g / cm ³ are used for the weight ³ , and a thickness of 0. A samarium cobalt magnet disk having a diameter of 4 mm and a diameter of 1.8 mm and a density of 8.4 g / cm ³ were used. Said By substantially the same as the weight member 3 thickness and density of the permanent magnet 11, the weight body 3 becomes uniform material equivalent, at the same time it is possible to improve the design accuracy of the natural frequency f _0, without changing the natural frequency f ₀ is set, the pendulum type sensor 1 it is possible to prevent the upsizing. In this embodiment, when the natural frequency f ₀ is set to 3 Hz and the diameter of the samarium cobalt magnet disk is changed from 5 mm to 25 mm without changing the overall size of the pendulum sensor, The design accuracy of the natural frequency f ₀ is in the range of 3 Hz ± 0.2 Hz, which is very high as a small pendulum type sensor. It is obvious that this means is also effective in the embodiment of the present invention shown in FIGS. 1, 7 and 8.

FIG. 10 shows another embodiment of the pendulum type sensor according to the present invention. The embodiment shown in FIG. 10 has the same configuration as that of the embodiment of FIG. 9, but three permanent magnets 11 are installed on the weight body 3 as the magnetism generating means 12. The three permanent magnets 11 are arranged symmetrically with respect to a straight line 15 connecting the gravity center position 5 and the rotation center 4. In this embodiment, the natural frequency _{f 0} 3 Hz, 4 mm the average mass distribution equivalent radius RD7, and the distance Ld6 between the rotation axis center 4 and the center of gravity position 5 and 0.3 mm.

  The three permanent magnets 11 are disposed symmetrically with respect to a straight line 15 that connects the center of gravity position 5 and the rotation axis center 4, so that the magnetic flux distribution formed connects the center of gravity position 5 and the rotation axis center 4. It becomes symmetrical with respect to the straight line 15. Therefore, the rotational position or angle of the pendulum body 8 can be accurately measured even if the magnetic sensor 14 and the hall element 13 in the housing 2 are set at arbitrary positions. Therefore, the magnetic sensor 14 and the Hall element 13 can be arranged at a position where the pendulum type sensor 1 can be most miniaturized, which is effective for reducing the size and weight of the pendulum type sensor 1. However, the entire pendulum type sensor 1 can be designed to have a size of 10 mm × 10 mm. It is obvious that this means is also effective in the embodiment of the present invention shown in FIGS. 1, 7, 8 and 9.

  Further, as in the embodiment of FIG. 1, an even number of permanent magnets 11 are arranged symmetrically with respect to a straight line 15 connecting the center of gravity position 5 and the rotation axis center 4, and the polarity of the permanent magnets 11 is anisotropic. The magnetic flux distribution density in the case of being arranged in the above is a point-symmetrical shape with respect to one point of a straight line 15 connecting the center of gravity position 5 and the rotation axis center 4, but the effect is the same as the line symmetry because of the use of symmetry. The same.

  Here, the present inventors examined the case where the permanent magnet 11 having a density different from the density of the weight body 3 was used in the embodiment of the present invention shown in FIGS.

  If the distance between the center of gravity 5 of the weight body 3 including the permanent magnets 11 having different densities and the rotation axis center 4 is Ld, and the mass distribution equivalent radius of the weight body 3 including the permanent magnets 11 having different densities is rd. By designing the mass distribution equivalent radius rd as appropriate, the basic operation is the same as the operation of the embodiment of FIG. 1, and it is obvious that the same effect can be expected.

In the embodiment of the present invention of FIG. 9, the weight 3 is made of a plastic material having a density of 1.4 g / cm ³ , and the permanent magnet 11 is made of a bonded magnet having a density of 6.8 g / cm ^3. The natural frequency f ₀ of the pendulum body 8 is set from 1.0 Hz to 12 Hz,
rd / Ld ≧ 1 (3)
More desirably, rd / Ld >> 3 (4)
A trial manufacture of the pendulum sensor 1 having the structure as described above was performed. When the natural frequency f ₀ was set to 3 Hz, the size of the pendulum type sensor 1 could be made 12 mm square vertically and horizontally by optimally arranging the permanent magnet 11 made of the bonded magnet. At this time, the distance between the center of gravity 5 of the weight body 3 including the permanent magnets 12 having different mass densities with the mass distribution equivalent radius rd = 4 mm and the rotation axis center 4 is Ld = 0.3 mm, and rd / Ld≈13. .3, and the same effect as described in the embodiment of FIG. Therefore, even if the density of the weights 3 and the density of the permanent magnets 11 are different, the effect of reducing the natural frequency f ₀ of the pendulum body 8 due to the moment of inertia is large as in the embodiment of the present invention of FIG. Thus, the design of the very low natural frequency f _{0 in} the range of 1.0 Hz to 12 Hz can be made acceptable, and furthermore, as is clear from the formula (5) and particularly the formula (6), The length is almost the same as the length of the weight body 3, and the natural frequency can be lowered without increasing the length of the pendulum, that is, while keeping the pendulum sensor 1 downsized. .

  In all the embodiments of the present invention described above, as the means 9 for detecting the rotational position or angle of the pendulum body 8, the magnetism generating means 12 and the magnetic sensor 14 are used. However, a technique using an optical element and an optical sensor is used. Obviously, a means for detecting by electrostatic capacity or a technique using a magnetic encoder can be applied.

  As described above, according to the present invention, the natural frequency of the pendulum body is expressed by the following equation. It can be set arbitrarily in the range of several Hz to several tens Hz, particularly in the range of 1 Hz to 12 Hz, and the pendulum type sensor can be reduced in size and weight, and a highly practical pendulum type sensor can be supplied. The value is very high.

  The pendulum type sensor according to the present invention is an unprecedented very small and light and has a natural frequency of ultra-low frequency of several Hz, and has a wide range of applications to highly sensitive vibration sensors, tilt sensors, acceleration sensors, etc. Obviously it is possible.

1 shows a schematic front cross-sectional view of a pendulum sensor according to the present invention. FIG. 2 shows a schematic side cross-sectional view in FIG. 1. It is a diagram illustrating the relationship between the natural frequency f ₀ of the weight body and the pendulum having an inertial mass. It is a diagram illustrating the relationship between the natural frequency f ₀ of the weight body and the pendulum having an inertial mass. It is a diagram illustrating the relationship between the natural frequency f ₀ of the weight body and the pendulum having an inertial mass. 7 is a table in which the natural frequency f ₀ of the pendulum body 8 is obtained using the distance L between the center of gravity and the rotation center of the weight body and the average mass distribution equivalent radius r as parameters. FIG. 3 shows a schematic front sectional view of another embodiment of the pendulum type sensor according to the present invention. FIG. 3 shows a schematic front sectional view of another embodiment of the pendulum type sensor according to the present invention. The schematic front sectional drawing of the other Example of the pendulum type sensor which concerns on this invention is shown. Another embodiment of the pendulum type sensor according to the present invention will be described.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pendulum type sensor 2 Case 3 Weight body 4 Center of rotation axis 5 Center of gravity position 6 Distance between center of gravity position of weight body and center of rotation axis L
7 Average mass distribution equivalent radius r
8 Pendulum body 9 Means for detecting rotational position or angle 9a Means for detecting rotational position or angle 9b Means for detecting rotational position or angle 11 Permanent magnet 12 Magnetic flux generating means 13 Hall element 14 Magnetic sensor 15 Center of gravity position and center of rotational axis Straight line connecting the casing 51 casing joint 53 rotating shaft 55 rotating bearing 57 weight support component 59 vertical line 61 rotating direction 63 rotating stopper

Claims (10)

At least a weight body having a mass distribution in the housing, a pendulum body provided at a set distance between the center of gravity and the center of rotation of the weight body, and means for detecting the rotational position or angle of the pendulum body; A pendulum sensor that detects the rotational position or angle of the pendulum body by means of detection means installed on the housing and the pendulum body, wherein the natural frequency of the pendulum body is set to 1.0 Hz to 12 Hz. ,
If the average mass distribution equivalent radius of the mass distribution of the weight is r, and the distance between the center of gravity of the weight and the center of the rotation axis is L,
r / L ≧ 1 (1)
More desirably, r / L ≧ 3 (2)
A pendulum type sensor characterized by
Here, the average mass distribution equivalent radius r means a radius r of a circular weight body having an inertia moment equivalent to the inertia moment of the weight body having a mass distribution.   2. The pendulum sensor according to claim 1, wherein the average mass distribution equivalent radius r is in the range of 0.5 mm to 10 mm, and more preferably in the range of 1.0 mm to 7.0 mm.   The distance L between the center of gravity of the weight body and the rotation axis center is in the range of 0.1 mm to 3.3 mm, and more preferably in the range of 0.2 mm to 2 mm. Pendulum type sensor.   4. The pendulum sensor according to claim 1, wherein the weight body and the pendulum body are made of the same member, and the center of the rotation axis is provided in the weight body.   5. The pendulum sensor according to claim 1, wherein the weight has a flat plate shape and has a circular shape, a polygonal shape, an elliptical shape, or a shape similar to these shapes.   6. The pendulum sensor according to claim 1, wherein the detecting means is a magnetic flux generating means provided on the weight body and a magnetic sensor for detecting a change in the magnetic flux.   7. The pendulum type sensor according to claim 6, wherein the magnetic flux generating means is a permanent magnet of all or part of the weight body, and the magnetic sensor is at least one Hall element.   8. The pendulum sensor according to claim 7, wherein one or a plurality of the permanent magnets are provided, and the thickness and density thereof are substantially equal to the weight body.   9. The pendulum sensor according to claim 7, wherein a plurality of the permanent magnets are installed symmetrically with respect to a straight line connecting the position of the center of gravity and the center of the rotation axis. One or a plurality of the permanent magnets having a density different from the density of the weight body is provided, the distance between the center of gravity of the weight body and the center of the rotation axis is rd, and the average mass distribution equivalent radius is Ld Then,
rd / Ld ≧ 1 (3)
More desirably, rd / Ld >> 3 (4)
The pendulum type sensor according to claim 7 or 9, characterized in that

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