JP3245675B2 - Structure of servo accelerometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo accelerometer structure, and more particularly to an improvement in a joint structure between a central magnetic core and a cylindrical magnetic core constituting a pot-shaped core for accommodating a pendulum (pendulum) and a torque coil.

[0002]

2. Description of the Related Art A pendulum 6 of a servo accelerometer shown in FIG. 5 is integrated with a hinge 6a for supporting it.
The nature of the material of pendulum 6 has a significant effect on the performance of the accelerometer. For this reason, the material of the pendulum 6 has a very good spring characteristic and hardly generates thermal stress, such as fused quartz. Therefore, pendulum materials such as fused quartz generally have a small coefficient of thermal expansion. Therefore, in order to maintain good performance as an accelerometer, the material of the magnet housing (also referred to as a cylindrical magnetic core) 3, which is a structure supporting the pendulum 6, is made of an inverter material having a small coefficient of thermal expansion.

However, the thermal expansion coefficient of the magnet 1 made of a Sm-Co-based material is generally much larger than the thermal expansion coefficient of the material of the magnet housing 3. Therefore, simply magnet 1 and magnet housing 3
When adhesive bonding is performed, the bonded portion is peeled off due to a temperature change. Therefore, conventionally, (a) as shown in FIG. 6A, the magnet 1 is joined to the magnet housing 3 using a flexible adhesive 2.

(B) As shown in FIGS. 6B and 6C, the magnet 1 is adhesively bonded to a pole piece bottom 5 made of metal (pure iron or the like) having a small difference in thermal expansion coefficient from the magnet 1. The bottom 5 and the magnet housing 3 are provided with a through hole 3a at the bottom of the magnet housing 3,
The lower part of the pole piece bottom 5 is fitted into the through hole 3a,
The circumferential portion of the through hole 3a is joined by bonding or welding. With this configuration, when a thermal stress is applied, a compressive stress is applied in the radial direction, but it is not a shear stress. Such a method was taken.

[0005]

In the case of (a) described in the prior art, the position of the magnet 1 is not stable against environmental conditions such as temperature change and vibration because the adhesive has flexibility. For this reason, there has been a problem that a slight displacement of the magnet 1 causes a change in magnetic flux passing through the magnetic circuit, which adversely affects the performance of the accelerometer.

In the case (b), the diameter of the fitting portion between the magnet housing 3 and the pole piece / bottom 5 must be matched, so that precise processing is required and the cost is increased. The present invention solves these conventional problems, stabilizes the position of the magnet 1 against temperature changes, vibrations, and the like, as well as the conventional pole piece bottom 5.
It is an object of the present invention to eliminate the need for precision machining for fitting the cylindrical core 3 with the magnetic core 3.

[0007]

According to a first aspect of the present invention, there is provided a servo accelerometer having a pendulum for detecting acceleration, a pickoff for detecting a change in the position of the pendulum, and a torquer current corresponding to the pickoff output. A servo amplifier that generates the following, a Toruca coil attached to the pendulum and through which a Toruca current flows, and a pot-shaped core that houses the pendulum and the Toruca coil.
A pair of upper and lower pot-shaped cores symmetrical to each other are arranged close to and opposed to each other via a gap, and the upper and lower pot-shaped cores have a central core arranged in the axial direction, an inner end opened, and an outer end closed. The pendulum is disposed in the gap at right angles to the axis, and the upper and lower pot-shaped cores accommodate the cylindrical torquer coils with the axis as the center line.

In particular, the central magnetic core has a columnar magnet and a disk-shaped pole piece bottom bonded to the cylindrical core side end surface of the magnet having substantially the same thermal expansion coefficient as the magnet. At the closed end of the cylindrical core, a through hole considerably smaller than the diameter of the magnet is formed along the axis, and the closed end and the pole piece bottom are welded along the inner peripheral edge of the through hole that is in contact with each other. .

(2) In the second aspect of the present invention, in the above (1), the through hole formed at the closed end of the cylindrical magnetic core has a hollow cylindrical shape, and the closed end and the pole piece bottom are
Spot welding is performed at a plurality of locations along the inner peripheral edge of the through hole. (3) In the invention of claim 3, in (1), the through-hole formed in the cylindrical magnetic core has a funnel shape with a small diameter on the bottom side of the pole piece.

[0010]

1 and 4 show an embodiment of the present invention.
The same reference numerals as in FIG. 5 denote the same parts. FIG.
In the figure, reference numeral 6 denotes a pendulum for detecting an acceleration, which is supported by a hinge 6a and vibrates up and down by an input acceleration. Reference numeral 7 denotes a pick-off for detecting the position of the pendulum 6 based on a change in capacitance. Numeral 10 denotes a torquer through which a torquer current flows. A torquer coil 10a is wound around a cylindrical bobbin 10b having an axis L as a center line. Bobbin 10b is pendulum 6
Bonded on both sides.

11 (comprising 11a, 11b, 11c)
Is the housing of the accelerometer, the upper end of which is L axis,
It has a cylindrical shape with its lower end closed. Reference numerals 12 and 13 denote C mounted around the upper and lower magnet housings 3.
The ring 14 is a terminal led out from the wiring board 9. In the example of FIG. 1, a center core 20 is formed by the magnet 1 and the pole piece top 4 and the pole piece bottom 5 adhered to both end surfaces thereof.

The magnetic circuit of the servo accelerometer is a magnet 1
And a magnet housing (cylindrical magnetic core) 3. As described above, the cylindrical core 3 is made of a pendulum 6 made of a material having a small coefficient of thermal expansion such as fused silica.
A metal material having a small coefficient of thermal expansion, such as an invar material, is used for bonding. The magnet 1 attached to the cylindrical magnetic core 3 is made of, for example, an Sm-Co (samarium-cobalt) -based material, and generally does not have a material having a small thermal expansion coefficient such as an invar material. Therefore, if the magnet 1 and the cylindrical magnetic core 3 are simply joined as they are, the joint will peel off due to the difference in thermal expansion coefficient between the two when the temperature changes. In order to prevent this, (a) A pole piece bottom made of a material having a small difference in thermal expansion coefficient from the magnet 1, for example, pure iron, is joined to the magnet 1.

(B) The pole piece bottom 5 and the cylindrical magnetic core 3 are joined by forming a through hole 3a in the center of the bottom of the cylindrical magnetic core 3 and the inner peripheral wall of the through hole 3a and the pole piece. -The contact part of the bottom 5 is joined by welding. The diameter of the through hole 3a is sufficiently smaller than the diameter of the magnet 1.
According to (a), magnet 1 and pole piece bottom 5
Has a small difference in thermal expansion coefficient, so that peeling due to a temperature change does not occur. According to (b), the joint between the cylindrical magnetic core 3 and the pole piece bottom 5 is only the inner peripheral portion of the through hole 3a. Since the diameter of the through hole 3a serving as the joining portion is considerably smaller than the diameter of the magnet 1 (for example, 以下 or less), the joining portion has a larger temperature difference than the case where the magnet 1 is directly joined. However, the difference in elongation due to the difference in thermal expansion coefficient between the two joining materials is small, and the thermal stress is reduced. In addition, as shown in FIG. 3, no stress is generated outside the joint because the pole piece bottom 5 expands and contracts while being in contact with the bottom of the cylindrical magnetic core 3.

[0014] The joining by welding may be welding of the entire circumference or a spot welding of several points as shown in FIG. FIG. 2A shows a case where the through hole 3a of the cylindrical magnetic core 3 is formed in a hollow cylindrical shape. It is also possible to make the through hole 3a extremely small in diameter and to weld this portion at one point or in a state very close to one point.

At the time of welding by laser welding or the like, the shape of the through hole 3a has a large diameter at the bottom surface and a diameter at the contact portion on the pole piece bottom 5 side as shown in FIG. Can be funnel-shaped. The magnet 1 is made by sintering or the like, and is difficult to weld. Therefore, the magnet 1 is bonded to the pole piece bottom 5 made of pure iron or the like, which is easy to weld, and then the pole piece bottom 5 and the cylindrical magnetic core 3 are welded.

The thermal expansion coefficient of each member is as follows. Pendulum 6 (fused quartz): 0.4 to 0.55 [ppm
/ ° C] Cylindrical magnetic core 3 (invar): about 1.8 to 2 [ppm /
° C] Pole piece bottom 5 (iron): 11.8 [ppm / ° C] Magnet 1 (Sm-Co type): about 12 to 13 [ppm
/ ℃]

[0017]

According to the present invention, the joint between the magnet 1 and the cylindrical magnetic core (magnet housing) 3 is not destroyed due to the difference in thermal expansion coefficient between the two, and is resistant to environmental conditions such as temperature change and vibration. Since the magnet 1 is stably held, the performance of the accelerometer is also stabilized. In addition, since the pole piece bottom 5 and the cylindrical magnetic core 3 are fitted to each other as in the related art, it can be realized without performing complicated and precise processing on these.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention.

FIG. 2 is a magnet housing (cylindrical magnetic core) 3 of FIG.
FIG. 3 is a vertical cross-sectional view showing a joint state between the magnetic core and a central magnetic core 20.

FIG. 3 is an enlarged cross-sectional view showing the periphery of a welding location P in FIG. 2A.

FIG. 4 is a plan view of a through hole 3a showing an arrangement of a welding portion P in FIG. 3;

FIG. 5 is a view showing a structure of a conventional servo accelerometer, wherein A is a perspective view with a part cut away, and B is a principle structural view.

FIG. 6 is a view showing a center magnetic core 20 and a magnet housing 3 shown in FIG. 5;
FIG. 3 is a longitudinal sectional view showing a joined state of FIG.

Claims (3)

(57) [Claims] 1. A pendulum for detecting acceleration, a pickoff for detecting a change in the position of the pendulum, a servo amplifier for generating a torquer current in accordance with the pickoff output, and a servo amplifier attached to the pendulum and through which the torquer current flows. A torca coil, and a pot-shaped core for accommodating the pendulum and the toruca coil. The magnetic core comprises a central magnetic core arranged in the axial direction, a cylindrical magnetic core having an open inner end and a closed outer end, wherein the pendulum is arranged in the gap at a right angle to the axis, and the upper and lower pots are provided. In the structure of a servo accelerometer in which a cylindrical Toruca coil having the axis as a center line is housed in a shaped magnetic core, Has a cylindrical magnet, a disk-shaped pole piece bottom adhered to the cylindrical core side of the magnet having substantially the same thermal expansion coefficient as the magnet, and the cylindrical core has a closed end. A hole substantially smaller than the diameter of the magnet is formed in the part along the axis, and the disc-shaped pole piece bottom magnet is bonded
And the closed end in contact with this surface
A structure of a servo accelerometer, wherein an inner peripheral edge of a through hole of a portion is welded . 2. The structure of the servo accelerometer according to claim 1, wherein the through-hole formed in the closed end of the cylindrical magnetic core has a hollow cylindrical shape, and the closed end has Part and the pole piece
The servo accelerometer structure, wherein the bottom is spot-welded at a plurality of locations along the inner peripheral edge of the through hole. 3. The structure of the servo accelerometer according to claim 1, wherein the through hole formed in the cylindrical magnetic core has a small diameter funnel (funnel) on the bottom side of the pole piece. ) The structure of a servo accelerometer, characterized in that