JPH06307865A - Inclination sensor - Google Patents

Abstract

PURPOSE:To provide an air damper type inclination sensor, which can restrict a change of the detecting characteristic generated by a change of coefficient of viscosity of the air due to the temperature change. CONSTITUTION:In an air damper type inclination sensor 1, a ball 3 is sealed inside of a cylindrical case 2 with air, and the movement condition of the ball 3 is detected by magnetic sensors 5, 6, 7 provided outside of the cylindrical case 2. In this inclination sensor, a relative difference between the coefficient of linear expansion of the cylindrical case 2 and the coefficient of linear expansion of the ball 3 is set at a value, which can restrict a change of the operation characteristic of the inclination sensor generated by the change of the coefficient of viscosity of the air due to the temperature change.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a ball type tilt sensor using an air damper.

[0002]

2. Description of the Related Art Conventionally, a steel ball having a diameter slightly smaller than its inner diameter is enclosed in a cylindrical casing, and the movement of the steel ball depending on the occasional inclination is magnetically detected by a sensor provided outside the casing. There is known a tilt sensor that detects the degree of the tilt by performing a positive detection. By the way, in this type of inclination sensor, it is desired that a proper damper force be applied to the movement of the steel ball so that the steel ball moves downward at an appropriate speed when the inclination occurs. Therefore, there is known a configuration in which a highly viscous medium such as oil is filled in the casing.

[0003]

However, in the case of adopting a structure in which the casing is filled with a medium such as oil, the casing needs to have a liquid-tight structure, which causes a problem of increasing cost. In order to solve this problem, it is conceivable to use an air damper in which air is sealed in the casing, but the air damper method has a problem that the characteristics change greatly due to the temperature change of the viscosity coefficient of air. . Therefore, an object of the present invention is to provide an improved air damper type inclination sensor in which the detection characteristic does not become defective even if the viscosity coefficient of air changes with temperature.

[0004]

A feature of the present invention for solving the above-mentioned problems is that a ball made of a magnetic material and having an outer diameter slightly smaller than the inner diameter of the cylindrical case is enclosed together with air in the cylindrical case. However, in the air damper type inclination sensor configured to detect the movement state of the ball generated according to the inclination by the magnetic sensor provided outside the cylindrical case, the linear expansion coefficient of the cylindrical case and the The relative difference between the coefficient of linear expansion of the ball and the coefficient of linear expansion of the ball is a value capable of suppressing the change in the operating characteristics of the tilt sensor caused by the temperature change of the viscosity coefficient of air.

[0005]

The temperature characteristic of the viscosity coefficient of air is positive, and the viscosity damping coefficient increases as the temperature rises. On the other hand, the change in the gap length between the ball and the cylindrical case due to temperature is
It is determined by the relative difference between the linear expansion coefficients of the two, and the size of the gap length changes so as to cancel the influence of the change in the viscosity of the air. Therefore, when the temperature changes, the change in the operating characteristics of the tilt sensor with temperature can be suppressed.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. Referring to FIGS. 1 and 2, an inclination sensor 1 according to the present invention has a case 2 which is a bottomed cylindrical body having an inner diameter D1 and an outer diameter D2 which is slightly smaller than the inner diameter D1 and moves in a chamber 2a in the case 2. It has a steel ball 3 stored freely. Front end 2b of case 2
A plug 4 is airtightly fitted in the chamber 2a, and air is enclosed in the chamber 2a as a medium for giving a damper effect to the ball 3, whereby an air damper type ball-type inclination sensor 1 is provided.
The main part of is composed. On the other hand, a pair of detection coils 5 and 6 is disposed in the annular grooves 2c and 2d provided on the outer peripheral surface of the case 2, and these coil 5 and 6 and the ball 3 have a ring shape. A static magnetic field is given by the magnet 7.

In the tilt sensor 1 thus constructed, the ball 3 moves in accordance with the tilt, and a change in the magnetic field generated by the ball 3 is detected by the pair of detection coils 5 and 6, and the tilt state at that time is shown. Since the operation itself for extracting the detection signal is known, a detailed description thereof will be omitted.

In the above inclination sensor 1 according to the present invention, in order to minimize the change of the damper force acting on the ball 3 even if the viscosity coefficient of the air enclosed in the chamber 2a changes due to the temperature change, Gap length between chamber 2a X (=
The relative difference in the coefficient of linear expansion between the case 2 and the ball 3 is set so that the change state of D1-D2) due to the temperature has a value that compensates for the temperature change of the viscosity coefficient.

The value of such a linear expansion coefficient can be determined as follows. That is, in the case of FIG. 2, there may be a relationship between the damper coefficient C (X) and the gap length X such that C (X) = 0.0001986 × X ^−2.5 +0.00645 (1) , Confirmed by experiment. FIG. 3 shows the experimental result which was the basis for deriving the empirical formula (1). This experiment was conducted at a constant ambient temperature.

By the way, the equation expressing the temperature characteristic of the viscosity coefficient of air is expressed by η (t) as the viscosity coefficient of air at t (° C).
Then, η (t) = 0.0466t + 16.93 (2)

Letting C (x) t be the viscous damping coefficient for the value x of the gap length at t (° c), the following formula (3) is used between the size of the gap and the resonance point gain G (x) t. The relationship shown is established. G (x) = 20log [2mk / {C (x) t (4mk-C (x) t 2) -0.5}] ··· (3) where, coefficient of linear expansion and the case of the ball 3 The diameter of the ball 3 (D2) at a difference of α, 25 (° C)
If the value of B is φ, then C (x) t is given by the following equation (4). C (x) t = η ( t) /18.1 [0.0001986 / {X + α (t -25) (Bφ + x / 2)} 2.5 -0.00645 ] (4)

As described above, since the relational expression between the clearance in which the ambient temperature is variable and the viscous damping coefficient C (x) is obtained, the value of α for obtaining the air damper effect with good temperature characteristics is shown in FIG. A diagram was used.

That is, C for each value of α when the atmospheric temperature is changed from -40 (° C) to 25 (° C)
Set the value of (x) (characteristic line (a)) and the ambient temperature to 80 (°
The value of C (x) (characteristic line (b)) for each value of α in the case of changing from C) to 25 (° C) is obtained by using the equation (4), and the changing points of these two curves The value of α at 6.4 × 1
0 ^-6 was obtained as a relative difference of the ideal.

In this case, as can be seen from FIG.
Since the value of the coefficient of linear expansion of the ball must not be larger than that of the ball 3, the material of Case 2 has a coefficient of linear expansion of 0.64 × more than the coefficient of linear expansion of the ball 3 of steel, 1.18 × 10 ^-5. only 10 ^-5 large, it is understood that it is sufficient to use a material of 1.82 × 10 ^-5.

However, in practice, it may not be easy to obtain a material having a linear expansion coefficient value as calculated, and in this embodiment, the linear expansion coefficient of 1.13 is the closest value. An epoxy resin of × 10 ^-5 is used as a material for the case 2.

FIG. 5 shows that -40 (°
C), 25 (° C), and 80 (° C) at each temperature, the step response of the inclination sensor is shown with the elapsed time t on the horizontal axis and the displacement δ on the vertical axis. Since 0.12 × 10 ⁻⁵ is used with respect to the ideal value of α of 0.64 × 10 ⁻⁵ , a change in the characteristics depending on the temperature appears, but the change is within the practical range.

Although one embodiment of the present invention has been described above, the present invention is not limited to the structure of the above-mentioned one embodiment, and the change in the operating characteristics of the tilt sensor, that is, its damper coefficient due to temperature change is suppressed as much as possible. Therefore, the difference in linear expansion coefficient between the ball and the case may be set so that the gap length X changes depending on the temperature change of the viscosity coefficient of air.

[0018]

According to the present invention, as described above, in the air damper type inclination sensor, the difference between the linear expansion coefficient of the cylindrical case and the linear expansion coefficient of the ball is caused by the temperature change of the viscosity coefficient of air. Since the value is such that the change in the operating characteristic of the sensor can be suppressed, the operating characteristic having excellent temperature characteristics can be obtained, and the detection accuracy thereof can be remarkably improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of an air damper type inclination sensor according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a graph showing an experimental result showing a relationship between a damper coefficient and a gap length of the tilt sensor shown in FIG.

FIG. 4 is a relative difference in linear expansion coefficient and a viscous damping coefficient when a predetermined temperature difference occurs in order to determine a relative difference in linear expansion coefficient between a ball and a case, which is necessary for obtaining the best temperature characteristics. A graph showing the relationship between and.

5 is a graph showing temperature characteristics of step response characteristics in the case of the embodiment of the tilt sensor shown in FIG.

[Explanation of symbols]

 1 Inclination sensor 2 Cylindrical case 3 Ball 5, 6 Sensor coil 7 Magnet X Gap length

Claims (1)

[Claims] 1. A cylindrical case made of a magnetic material and having an outer diameter slightly smaller than the inner diameter of the cylindrical case is enclosed together with air, and the state of motion of the ball generated according to the inclination is regulated by the cylindrical case. In an air damper type inclination sensor configured to be detected by a magnetic sensor provided outside, the relative difference between the linear expansion coefficient of the cylindrical case and the linear expansion coefficient of the ball is the temperature change of the viscosity coefficient of air. A tilt sensor having a value capable of suppressing a change in the operating characteristics of the tilt sensor caused by the above.