JP2921635B2 - Cross coil type indicating instrument - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pointer-type cross-coil indicating instrument in which a pointer stops at its position when driving is stopped, and particularly to a fuel gauge.

[0002]

2. Description of the Related Art Generally, a current varying according to a measured amount is applied to a pair of coils that generate magnetic fields that intersect each other, and a magnet rotor is rotated in the direction of a composite magnetic field of the magnetic fields generated by the pair of coils. A cross-coil type in-vehicle indicating instrument for displaying a measured amount by a pointer rotating with the magnet rotor is often used. Pointer type refers to a type in which the pointer stays at this position when the current is interrupted and does not move thereafter. An index indicating how much the pointer has moved after the current interruption is referred to as a needle setting characteristic, and a small movement of the pointer is referred to as a good needle setting characteristic. Various proposals have been made to improve the needle placement characteristics. This will be described with reference to the drawings.

FIG. 6 is a sectional view of a movement portion of an example of a conventional needle-positioned cross-coil indicating instrument.

[0004] As shown in the figure, this movement has a magnetically shielded case 1 in which an upper bobbin 2 and a lower bobbin 3 are arranged. Inside the upper and lower bobbins, a magnet rotor including a substantially disk-shaped bushing 4 and a ring-shaped magnet 5 attached to a peripheral portion of the bushing 4 is arranged. The magnet 5
A pair of diametrically opposed S and N poles are formed. A rotor shaft 6 serving as a rotating shaft is attached to the center of the magnet rotor, and a lower end of the rotor shaft 6 is supported by a bearing recess 7 provided inside and below the lower bobbin 3. A filler 8 such as silicone oil for applying a braking force to the rotor shaft 6 to prevent unnecessary swing of the rotor shaft 6 is provided inside the bobbins 2 and 3 to a volume of about 5% of the storage volume inside the bobbin. It is filled to some degree. Two coils 9 are wound around the outside of the bobbins 2 and 3 so as to cross each other. The crossing two coils 9 generate crossing magnetic fields in accordance with the magnitude of the input signal, and the combined magnetic fields are generated. The magnet 5 is rotated at a predetermined angle in the direction of the magnetic field.

FIG. 7 is a sectional view of the magnet rotor of FIG. 6 and its rotor shaft.

On the upper surface of the movement constructed as described above, a dial plate on which predetermined characters, scales and the like are formed is fixed by screws, and the tip of the rotor shaft 6 penetrates this dial plate. At the end, a pointer is fixedly attached to form a cross coil type indicating instrument.

The indicating instrument is housed inside a combination meter (not shown), and the combination meter is mounted on an instrument panel of a vehicle such as an automobile.

In the indicating instrument described above, a predetermined current as a drive signal based on a predetermined measurement signal such as the remaining liquid level in the fuel tank is supplied to the two intersecting coils 9 so that each coil is generated. The magnet rotor is rotated by an angle corresponding to the measured amount in accordance with the combined magnetic field of the magnetic fields to be generated. As a result, the rotor shaft 6 is rotated, and the hands are rotated on the dial to display the measured amount. When the coil 9 is de-energized, as in the case where the ignition switch of the automobile is turned off, the pointer stops at the spot under the braking of the filler 8 and does not return to the zero point.

In such a cross-point indicating instrument of the needle setting type, as a method of improving the needle setting characteristics, (1) the friction between the rotor shaft 6 and the bearing recess 7 is increased. (2) Increase the magnetic permeability of the magnetic shielding case 1. (3) Reduce the magnetic force of the magnet 5. (4) Reduce the weight imbalance of the rotating part. The movement described with reference to FIG. 6 is mainly designed to improve the needle placement characteristics by a method of adding a filler such as silicone oil.

[0010]

However, in the movement having the above structure, the air gap between the magnet and the magnetic shielding case is small, and if the magnet is stopped at a certain position, the magnetic shielding case receives the magnetic field lines of the magnet. Magnetized and the magnetism remains. Thereafter, the indicating instrument operates to the point E (Empty point) or the point F (Full point), and when the power is stopped at that time, the magnet is pulled by the residual magnetism of the magnetic shielding case at the original position. There is a problem in that it moves in that direction and may not stop at the position where the normal energization was stopped.

It is an object of the present invention to provide a cross-coil indicating instrument which makes it difficult for residual magnetism to remain in a magnetically shielded case and improves needle placement characteristics.

[0012]

According to the present invention, there is provided a magnet rotor comprising a substantially disk-shaped bushing and a ring-shaped magnet attached to a peripheral portion of the bushing inside a bobbin accommodated in a magnetically shielding case. And a rotor shaft serving as a rotation axis is provided at the center of the magnet rotor, and a filler for braking the rotation of the magnet rotor is filled. Further, two coils are wound outside the bobbin in a direction crossing each other. In the cross-coil indicating instrument for rotating the magnet rotor in the direction of the combined magnetic field generated by the two coils, the diameter of the magnet is smaller than the diameter of the bushing.

[0013]

According to the present invention, since the diameter of the magnet is made smaller than the diameter of the bushing and the air gap between the magnetic shielding case and the magnet is increased, the magnetization of the magnetic shielding case is reduced, and the residual magnetism is reduced. Smaller. Further, since the contact area between the bushing and the filler is kept as small as possible, the influence of the residual magnetism can be reduced without changing the braking effect, and the needle setting characteristics are improved.

[0014]

FIG. 1 is a sectional view of an embodiment of the present invention, and FIG. 2 is a sectional view of a magnet rotor and a rotor shaft portion of FIG.
The same or corresponding portions as those described in the description of the related art are denoted by the same reference numerals, and description thereof will be omitted.

The cross coil type indicating instrument according to this embodiment is different from the conventional one in that the diameter of the magnet 5 is smaller than the diameter of the bushing 4 and the area of the bottom surface of the bushing 4 is as close as possible to the bobbin storage area. Further, the outer diameter of the bushing 4 is also as close as possible to the storage section inside the bobbins 2 and 3. Thereby, the air gap G between the magnet 5 and the magnetic shielding case 1 can be made larger than before, and the residual magnetism of the magnetic shielding case 1 can be reduced.

FIG. 3 is a sectional view for explaining an air gap between the magnet and the magnetic shielding case. In the figure, the air gap G is defined by the distance between the inner surface of the magnetic shielding case 1 and the outermost periphery of the magnet 5. FIG. 4 is a correlation diagram showing a relationship between the air gap amount and the residual magnetism. As shown in the figure, it can be seen that the residual magnetism remaining in the magnetic shielding case 1 rapidly decreases as the air gap amount increases. In this embodiment, since the diameter of the magnet 5 is smaller than the diameter of the bushing 4 and the air gap G is increased, the magnetism remaining in the magnetic shielding case 1 is reduced. Therefore, when the next driving of the instrument is stopped, the magnet 5 does not stop at that position and is less likely to be moved by being pulled by the residual magnetism of the magnetic shielding case 1, thereby improving the needle setting characteristics.

Also, the outer diameter of the bushing 4 is not reduced so that the contact area between the bushing 4 and the filler 8 is not reduced, and the braking effect of the silicone oil as the filler on the viscous bushing and the rotation of the magnet is reduced. Since it is not changed, the braking effect increases as the residual magnetism decreases, and the needle setting characteristics are improved.

The bushing 4 may be made of a non-magnetic metal, but if it is made of a light material such as a synthetic resin, the weight can be reduced, the inertia is reduced, the braking effect by the filler 8 is increased, and the needle setting characteristic is improved. Is further improved.

FIG. 5 is a perspective view of another embodiment of the present invention. As shown, a braking rib 10 extending upward is provided around the bushing 4. Since the braking rib 10 increases the contact area with the filler 8, the braking effect is further enhanced.

[0020]

As described above, according to the present invention, the diameter of the magnet is made smaller than the diameter of the bushing so that the contact area between the bushing and the filler does not change as much as possible. As the gap was increased, the magnetism remaining in the magnetic shielding case was reduced, and the effect of the residual magnetism on stopping the magnet rotor was reduced.
Improvement of the needle setting characteristics can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view of one embodiment of the present invention.

FIG. 2 is a cross-sectional view of the magnet rotor of FIG. 1 and a drive shaft portion thereof.

FIG. 3 is a cross-sectional view illustrating an air gap between a magnet and a magnetic shielding case.

FIG. 4 is a correlation diagram showing a relationship between an air gap device and residual magnetism.

FIG. 5 is a perspective view of another embodiment of the present invention.

FIG. 6 is a sectional view of a movement portion of an example of a conventional cross-coil type indicating instrument.

FIG. 7 is a sectional view of the magnet rotor of FIG. 6 and a rotor shaft portion thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic shielding case 2 Upper bobbin 3 Lower bobbin 4 Bushing 5 Magnet 6 Rotor shaft 7 Bearing recess 8 Filler 9 Coil 10 Braking rib G Air gap

Claims (1)

(57) [Claims] 1. A magnet rotor comprising a substantially disk-shaped bushing and a ring-shaped magnet attached to a peripheral portion of the bushing is provided inside a bobbin accommodated in a magnetic shielding case. A rotor shaft serving as a rotation axis is provided at the center, and a filler that brakes the rotation of the magnet rotor is filled, and further, two coils are wound around the bobbin in a direction crossing each other,
A cross-coil type indicator for rotating the magnet rotor in a direction of a combined magnetic field generated by the two coils, wherein a diameter of the magnet is smaller than a diameter of the bushing.