JPS6375568A - Acceleration detector - Google Patents

Abstract

PURPOSE:To measure acceleration with extremely small variation with time by utilizing a hollow cylinder body which has a closed part whose air vent is sealed with an expansion film and the piezoelectric resistance effect pressure sensor of a silicon single crystal. CONSTITUTION:When a mass body 2 is moved by applying force to a detector as shown by an arrow, the mass body is in slide contact with the inner peripheral wall 1c of a hollow part by a sealing member 3, so it is to stop at a reference position by inertia. Namely, the hollow cylinder body 1 with the closed part 6 whose air vent 6a is sealed with the expansion film 9 and the mass body 2 move relatively and this movement is transmitted as a rise in a temperature to the pressure sensor through noncompressed fluid 5. The pressure in the hollow part 1b, on the other hand, does not move the noncompressed liquid 5 to the hollow part 1e by the sealing member 3 and is not discharged to the atmosphere from the hollow part 1e by the expansion film 9. Thus, an electric signal output proportional to the pressure is obtained from the pressure sensor 4.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is applicable to detection of acceleration of devices that move people and objects, such as vehicles, conveyors, robot arms, etc., and detection of collisions and contact with objects. The present invention relates to an acceleration detector used for detecting acceleration and changes thereof.

(Prior Art) In various devices intended to move large objects such as vehicles and elevators, it is desirable to make people feel as little change in acceleration as possible.

In other words, if the mass of a person is M, the force F applied to the person is F = Mα (α; acceleration), and if the acceleration is constant, the human body will only feel a constant force and will not feel shaken. do not.

In automobiles, etc., acceleration, deceleration, and sudden handling that generate a force that exceeds the grip force of the tires are dangerous and also cause discomfort to the occupants.

These things apply not only to people but also to things.

For these reasons, detecting acceleration is considered important in these devices.

2. Description of the Related Art Conventionally, many acceleration detectors using piezoelectric effects have been used because they have many practical advantages.

The piezoelectric effect is a phenomenon in which an electric charge is generated when a certain element is subjected to force and strain, and this element is called a piezoelectric element.

For example, there are typical piezoelectric elements such as barium titanate porcelain, and recently many elements have been developed, including special organic plastics.

(Problem to be solved by the invention) However, since conventional acceleration detectors attempt to detect acceleration by measuring electric charges, it is difficult to measure accelerations that change over time (for example, gravitational acceleration). Not suitable. However, it is desired that the frequency characteristics of the accelerometer be 1- in the range up to the low frequency range.

Conventional acceleration detectors have had problems, such as that it is difficult to achieve a flat frequency range of 1142 or below, and that they require an amplifier with an extremely high input impedance, ie, a charge amplifier.

In order to solve these drawbacks, the present invention provides an acceleration detector using a silicon single crystal piezoresistive pressure sensor.

(Means for Solving the Problems) The present invention for achieving the above object will be explained using FIG. 1 corresponding to an embodiment.

In the acceleration detector according to the present invention, a pressure sensor is connected to a hollow part 1b of a hollow cylindrical body 1, which has a through hole 6a at one end and a closed part in which the through hole 6a is sealed with an elastic membrane 9, through an opening 1a at the other end. The pressure introduction pipe 4a of the pressure chamber 4f of No. 4 is inserted, and the mass body 2, which has a seal member 3 fixed to its outer peripheral surface, slides into the inner peripheral wall 1c of the hollow portion 1b through the seal member 3. The hollow part 1d between the mass body 2 and the pressure introduction pipe 4a and the pressure sensor 4
The pressure chamber 4f and the hollow portion 1e between the mass body 2 and the elastic membrane 9 are filled with an incompressible fluid 5.

(Function) According to the present invention, a pressure sensor 4 that utilizes the piezoresistance effect of a silicon single crystal is used, and a sealing member 3 is fixed to the outer peripheral surface of the hollow portion 1b as a pressure transmission method.
The relative movement between the mass body 2 housed in the hollow part 1b and the hollow cylindrical body 1 with the seal member 3 in sliding contact with the inner circumferential wall of the incompressible fluid 5 generates pressure on the pressure sensor 4 Since the acceleration is transmitted, it is possible to obtain an electrical signal output from the pressure sensor 4 in accordance with the acceleration applied to the acceleration detector.

(Example) FIG. 1 is a sectional view illustrating an acceleration detector according to an example of the present invention, in which 1 is a metal hollow cylinder, 2 is a mass body,
3 is a sealing member, 4 is a pressure sensor, 5 is an incompressible fluid,
6 is a closed portion provided with 68 through holes, one end of which is sealed with a stretchable membrane 9.

Further, 1a is an opening of the hollow cylinder 1, 1b is a hollow part of the hollow cylinder 1, and 1c is an inner circumferential wall of the hollow part 1b.

As shown in FIG. 2, the pressure sensor 4 includes a pressure introduction pipe 4a communicating with a pressure chamber 4f, a diaphragm 4b, and a diaphragm 4c.
A lead pin of 4D and a temperature characteristic compensation board of 4D are fixed to a case of 40.

The lead pin 4c is connected to the amplifier 4h.

When pressure is transmitted from the pressure introduction pipe 4a to the diaphragm 4b of the pressure chamber 4f via the incompressible fluid 5, strain is applied to the piezo pressure sensitive resistor (not shown) formed in the shape of a Wheatstone bridge on the diaphragm 4b. This causes the resistance value to change and the bridge to become unbalanced, causing a change in the output voltage for a certain input voltage. A piezoresistive pressure sensor utilizes the fact that this output voltage is proportional to strain, that is, pressure.

Next, the present invention will be explained in detail. 3 and 4 are cross-sectional views with the pressure sensor 4 removed.

Now, assuming the position of the mass body 2 as shown in FIG. 3 as a reference, when force is applied to the acceleration detector in the direction of the arrow in FIG. Since it is in sliding contact with the peripheral wall 1c, it tends to stay at the reference position due to inertia.

That is, the hollow cylindrical body 1 and the mass body 2 move relative to each other, and the movement is transmitted to the pressure sensor 4 through the incompressible fluid 5 as a pressure increase. On the other hand, the pressure in the hollow part]-b does not move the incompressible fluid 5 to the hollow part 1e by the seal member 3, and is not released from the hollow part 1e into the atmosphere by the elastic membrane.

In this way, as described above, the pressure sensor 4 can obtain an electrical signal output proportional to the pressure, so that it can function as an acceleration detector.

In the present invention, since the pressure sensor 4 utilizes a piezoresistance effect, unlike the piezoelectric effect type, a constant voltage is applied to the pressure sensitive resistor formed in the shape of a bridge, and the strain in the diaphragm 4b caused by the pressure is reduced. Since the output is obtained from the corresponding resistance change, if the temporal change is slow (for example, due to gravitational acceleration), the output appears as a DC component. Therefore, the frequency characteristics as a detector can be flat down to an extremely low frequency range, and a charge amplifier is not required.

The sealing member 3 and the mass body 2 are made of a diaphragm 3a for the sealing member 3, and a lead material having a relatively high specific gravity for the mass body, as shown in Figs. 5 to 7 (Fig. 5). .

Alternatively, a magnetic fluid 3b is used for the sealing member 3, and a magnet 7 and a ferromagnetic material 8 are used for the mass body 2 (FIG. 6).

Alternatively, it is suitable to use high viscosity oil 3c for the sealing member 3 and lead with relatively high specific gravity for the mass body 2 (FIG. 7).

Furthermore, the compressibility of the incompressible fluid 5 is 2°×10
-6 Cal/kg f) or less, the viscosity is 1-02 (Pa
・S) The above liquids are suitable, but liquid paraffin is suitable for the sealing member 3 shown in FIG. Alternatively, glycerin is suitable because it does not mix with magnetic fluid.

Furthermore, for the sealing member 3 and mass body 2 shown in FIGS. 5 and 7, not only the above-mentioned liquid paraffin and glycerin but also silicone oil, vacuum oil, machine oil, etc. are suitable.

Further, FIGS. 8 and 9 are partially enlarged views of a structure in which a diaphragm 9a and a bellows 9b are used in the elastic membrane 9. A diaphragm 9a is used as the stretchable membrane 9, and FIG. 9 shows the stretchable membrane 9.
This uses bellows 9b.

(Effects of the Invention) As explained below, according to the present invention, a piezoresistive pressure sensor is used as an acceleration detector, so the frequency characteristics in the extremely low frequency range starting from the DC component are flattened. It has the advantage that it does not require an amplifier with extremely high input impedance.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a sectional view of the configuration of a pressure sensor, Figs. 3 and 4 are sectional views showing the principle of pressure generation, and Fig. 5 is a sealing member. Figure 6 is a cross-sectional view using a diaphragm as a sealing member, Figure 7 is a cross-sectional view using a high-viscosity oil as a sealing member, and Figure 8 is a cross-sectional view using a diaphragm as an elastic membrane. Cross-sectional view, FIG. 9 is a cross-sectional view in which a bellows is used as an elastic membrane. 1.Hollow cylindrical body 1a...Opening part 1b...Hollow part (
]O) 1c... Inner peripheral wall 1d... Hollow part 1e... Hollow part 2... Mass body 3... Seal member 3a... Diaphragm 3b... Magnetic fluid 3c... High viscosity oil 4... Pressure sensor 4a.・Pressure introduction pipe 4b・・Diaphragm 4c・・Lead pin 4d・・Temperature characteristic compensation board 4e・・Case 4f・・Pressure chamber 4g・・Through hole 4h・・Amplifier 5・・Incompressible fluid 6・・Occluded part 6a・・Through hole 7・・Magnet 8・・Ferromagnetic material 9・・Stretchable membrane 9a・・Diaphragm 9b・・Bellows Patent applicant Copal Electronics Co., Ltd. Engraving of drawings (no changes in content) Fig. 1 Fig. 2 3 Figure 5 1d 2 1e Figure 5 Figure 6 Figure 7 Figure 8 Figure 5 1e Procedural amendment (method) % formula % 1. Indication of case 1985 Patent Application No. 21.7902 3. Person making the amendment Relationship to the case Patent applicant 5, number of inventions increased by amendment 6, subject of amendment drawings (all) 7, content of amendment

Claims (1)

[Claims] 1. Introducing the pressure of the pressure chamber of the pressure sensor from the opening at the other end into the hollow part of a hollow cylindrical body having a through hole at one end and a closed part where the through hole is sealed with a stretchable membrane. A pipe is inserted, and a mass body having a sealing member fixed to its outer circumferential surface is housed in the hollow part in a state in sliding contact with the inner peripheral wall of the hollow part through the sealing member, and the mass body and the pressure introduction pipe and a pressure chamber of the pressure sensor and a hollow part between the mass body and the elastic membrane are filled with an incompressible fluid. The acceleration detector 3 according to claim 1, wherein the pressure sensor is a pressure sensor that utilizes the piezoresistance effect of a silicon single crystal, the mass body is a metal with a high specific gravity, and the seal member is a diaphragm. The acceleration detector 4 according to claim 1, wherein the mass body is made of a permanent magnet or a combination of a permanent magnet and a ferromagnetic material, and the sealing member is made of a magnetic fluid. Acceleration detector 5 according to claim 1, characterized in that the mass body is made of metal with a large specific gravity, and the seal member is made of high viscosity oil. In the acceleration detector 6 described in item 1, the incompressible fluid has a compressibility of 20×10^-^6 (
cm^2/kgf) or less, viscosity is 10^2 (Pa・S)
Claim 1 characterized in that the liquid is
Acceleration detector 7 according to claim 1, wherein the elastic membrane is a diaphragm or a bellows.