JP2000009744A - Acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acceleration sensor, free of malfunctions, even in the outdoors which have severe temperature changes or the like, and capable of detecting only the acceleration in the measuring object direction, and having high measuring accuracy. SOLUTION: This acceleration sensor has a displacement detection part having a hollow, slender, cylindrical glass tube 7, a moving body, namely a cylindrical weight 8 arranged slidably along the inner wall along longitudinal direction, moving-body holding means, namely springs 9, 9' for pressurizing the moving body from the both sides of the sliding direction in the opposite directions respectively with equal pressures and for returning it to a prescribed position, optical displacement detection means, namely, LED 11, 11' for detecting a displacement quantity of the moving body by the change of a received light quantity, and quarts transistors 12, 12', and also has a data processing part for electrically processing the change of the received light quantity which is detected by the displacement detection part and for converting it into acceleration, and a recording part for recording the acceleration converted by the data processing part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor used to detect, as acceleration, an impact received while a vehicle is running.

[0002]

2. Description of the Related Art As a conventional acceleration sensor belonging to the above technical field, a strain gauge type acceleration sensor which applies a strain due to acceleration to a metal or semiconductor resistance through a seismic system and detects the acceleration based on a rate of the resistance change, And a piezoelectric acceleration sensor utilizing the property of generating a charge when a piezoelectric element such as lead zirconate / barium titanate / quartz is pressed by acceleration. However, when these are used outdoors, a pyroelectric effect appears in a place where the temperature difference is sharp, which causes a malfunction. Further, when it is desired to detect an acceleration only in a specific direction, an acceleration other than the measurement target acceleration direction is detected. Conventional acceleration sensors have a vertical / horizontal sensitivity ratio of 5%.
The measurement accuracy is low.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an acceleration sensor having a high measurement accuracy capable of detecting only an acceleration in a direction to be measured without malfunction even in a severe outdoors such as a temperature change. I do.

[0004]

In order to achieve the above object, an acceleration sensor is provided with a hollow elongated container, a moving body slidably disposed in the container along a longitudinal inner wall, and this moving body. A displacement detection unit having moving body holding means for returning to a predetermined position by pressing in opposite directions with equal pressure from both sides in the sliding direction and optical displacement detection means for detecting the amount of displacement of the moving body by a change in the amount of received light; It is characterized by having a data processing unit that electrically processes a change in the amount of received light detected by the detection unit and converts the change into acceleration, and a recording unit that records the acceleration converted by the data processing unit. .

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on examples with reference to the drawings. FIG. 1 is an explanatory diagram showing an outline of the acceleration sensor. Plastic protective case 1
Inside, a displacement detection unit 2, a data processing unit 3, a memory 4 constituting a recording unit, a time output unit 5, and a small battery 6 as a power supply are sealed.

FIG. 2 is a schematic front view showing the displacement detecting section 2, and FIG. 3 is an operational amplifier 13 of the data detecting section 3 from the displacement detecting section 2.
FIG. 2 is a circuit diagram illustrating a system in which a current is sent to the system. A cylindrical weight 8 as a moving body is slidably disposed along the inner wall of the glass tube 7 inside a transparent cylindrical glass tube 7 as a container. Further, one end of a spring 9 serving as a moving body holding means is fixed to a left wall portion in the glass tube 7, and one end of a spring 9 'is fixed to a right wall portion in the glass tube 7.
Then, the weights 8 are pressed by equal pressures from both sides at the other ends of the springs 9 and 9 ′, and the weights 8 are held at a central position between the left and right walls of the glass tube 7. Shielding plates 10, 10 ′ are provided so as to be slidable integrally with the weight 8, respectively, from the center of both sides of the weight 8, and the tips project from the left and right walls of the glass tube 7, respectively. An LED 11 constituting an optical displacement detecting means is provided above the tip of the shielding plate 10, and a photo transistor 12 is also provided below the tip of the shielding plate 10. ing. The tip of the shielding plate 10 is set at a position where the light emitted from the LED 11 is slightly blocked. Regarding the tip of the shielding plate 10 ′, the LED 11 ′ constituting the optical displacement detecting means is provided on the upper side and the phototransistor 1 is provided on the lower side.
2 'are similarly arranged. LED 11, 1
1 'is set to the same light emission amount. The phototransistors 12 and 12 ′ have the same characteristics and generate the same amount of current when the amount of received light is the same. When the weight 8 is located at the center of the glass tube 7,
The magnitudes of the currents generated from 2 and 12 'are set to be the same.

The time output unit 5 operates electrically, measures the current time, and outputs the current time to the data processing unit 3.

The data processing unit 3 includes a phototransistor 1
2, 12 ', the memory 4, and the time output unit 5, and the light receiving amounts of the phototransistors 12, 12' and the current time of the time output unit 5 are always input. The data processing unit 3 includes a differential amplifier 13, a dual wave detector 14, and a moving average circuit 1 as moving average value calculating means.
5. It has a comparator 16 as a comparing means, a sample and hold circuit 17, and a data processing circuit 18.

The cooperative relationship between the components of the data processing unit 3 is as follows. That is, the impact causes the weight 8 and the shielding plates 10 and 10 'to slide integrally with the displacement X in proportion to the magnitude of the impact. And the phototransistor 1
In order to increase the cutoff of one of the light receptions 2 and 12 'and reduce the cutoff of the other light, the respective light reception amounts change. Accordingly, the current generated from the phototransistors 12 and 12 'changes, and a difference occurs between the generated currents. The difference between the generated currents is input to the operational amplifier 13, amplified and output as a positive or negative electric signal. This electric signal is input to the dual-wave detector 14, and the positive and negative values are replaced with the absolute value, which is output as the absolute value | a1 | of the electric signal. |
a1 | is a moving average circuit 1 through one of two branches
5, a moving average value | a2 | is calculated and output. Subsequently, a comparison target value | a4 | obtained by adding the threshold value | a3 | to the moving average value | a2 | is input to the comparator 16, and is directly sent from the double wave detector 14 to the comparator 16 through another crossroad. It is compared with the absolute value | a1 | of the input electric signal.
If the comparison results in | a1 |> | a4 |, it is determined that an impact has occurred, and the comparator 16 outputs an ON signal. The moving averaging circuit 15 and the threshold value are provided because the weight 8 and the shielding plates 10 and 10 'slide and the acceleration is detected even when normal acceleration or deceleration is performed in a vehicle or the like. This is to exclude an acceleration caused by deceleration and to output an ON signal from the comparator 16 only when an impact is received. Only when the ON signal is output in this way, the interrupt processing circuit 1 in the data processing circuit 18
9 operates to output an interrupt command signal, to take in the electric signal | a1 | taken into the sample hold circuit 17, convert it into acceleration by the A / D converter 20, and record the value in the memory 4. At the same time, the data processing circuit 1
8 stores the time information output from the time output unit 5 in the memory 4;
To record. Thereby, the acceleration due to the impact and the time at which the impact was received are simultaneously recorded in the memory 4.

When the acceleration sensor having the above structure is fixedly mounted on a vehicle such as a train so that the direction of the glass tube 7 is aligned with the traveling direction of the vehicle, the vehicle may move from the outside in the traveling direction for some reason during traveling. When a shock is received, the operation is performed as described above, and the acceleration due to the shock and the time when the shock is received are simultaneously recorded.

When the acceleration sensor is mounted outside the vehicle, the protection case 1 protects the components of the sensor from external warmth, wind, rain, noise and electric field, so that there is little fear of damage or malfunction. Further, since no vibration or impact other than the traveling direction of the vehicle, such as the vertical direction, is detected, the measurement accuracy is high.
Therefore, it is possible to know exactly when and what kind of impact was received.

In the above-described embodiment, the container is a transparent cylindrical glass tube. However, the present invention is not limited to this. Any container may be used as long as a movable body can be slidably disposed inside.
Further, the moving body is not limited to the weight, and may be anything that slides in the container by impact or acceleration / deceleration. Further, the moving body holding means is not limited to a spring, and may be any means that can press the moving body uniformly from both sides and return to a predetermined position when the impact or acceleration is eliminated, for example, an elastic member such as rubber or a solid member. Other things may be used. Further, the optical displacement detecting means is not limited to the LED and the phototransistor. Further, the data processing unit is not limited to the one described in the embodiment, but may be another processing system as long as it can perform the same processing. The power source is not limited to a small battery, but a small battery can make the sensor smaller. Furthermore, the protective case is not limited to a plastic case, but may be any as long as it has high insulation and durability.
For applications, it is not limited to the detection of impacts received by moving vehicles and the like, but can also be used to detect impacts received by fixed objects such as iron bridges, but high electric fields and noise, such as vehicles, especially train pantographs, The acceleration sensor according to the present invention is suitable for installation in a place exposed to severe environmental conditions such as a severe temperature difference.

[0013]

As described above, the present invention does not detect an acceleration in a direction other than a specific direction, so that a measurement error can be reduced. In addition, since all the components are housed in a protective case that can be isolated from the external environment that may cause malfunctions, it can be installed in places exposed to severe environmental conditions such as high electric fields, noise, and severe temperature differences. It is hard to cause breakage and measurement error.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an outline of an acceleration sensor.

FIG. 2 is a schematic front view showing a displacement detection unit 2.

FIG. 3 is a circuit diagram showing the displacement detection unit 2 and the relationship between the displacement detection unit 2 and the operational amplifier 13 of the data processing unit 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Protective case 2 Displacement detection part 3 Data processing part 4 Recording part 5 Time output part 15 Moving averaging means 16 Comparison means

Claims (4)

[Claims] 1. A hollow elongate container, a moving body slidably disposed in the container along a longitudinal inner wall, and the moving body is pressed in opposite directions from both sides in the sliding direction by equal pressures. A displacement detecting section having a moving body holding means for returning to a position and an optical displacement detecting means for detecting a displacement amount of the moving body by a change in a received light quantity, and electrically processing a change in the received light quantity detected by the displacement detecting section; An acceleration sensor comprising: a data processing unit that converts the acceleration into an acceleration; and a recording unit that records the acceleration converted by the data processing unit. 2. A moving averaging means for converting a change in the amount of received light into an electric signal and calculating the electric signal as a moving average value, and moving and calculating a value obtained by adding a predetermined threshold value to the calculated moving average value. The electric signal inputted without passing through the averaging means is compared with the electric signal, and when the magnitude of the electric signal inputted without passing through the moving averaging means exceeds the sum of the moving average value and the threshold value, 2. The acceleration sensor according to claim 1, wherein comparison means for recording the acceleration is provided in the data processing unit. 3. The acceleration sensor according to claim 1, further comprising a time output unit for simultaneously recording the time when the recording unit records the acceleration converted by the data processing unit. 4. An acceleration sensor having a protective case for isolating a component according to claim 1, 2 or 3 from an external malfunction environment.