JP3690062B2 - Cross coil type indicator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cross coil type indicating instrument used in vehicles, industrial equipment, and the like.
[0002]
[Prior art]
Conventionally, as this kind of cross coil type indicator, there is one as shown in Japanese Utility Model Publication No. 63-19804.
This cross coil type indicator is equipped with a hollow bobbin in which both cross coils are wound in a cross shape, and two pairs of terminal storage legs cross each other along the axial direction on the outer peripheral wall of this bobbin. They are formed at equiangular intervals between the coils.
[0003]
The bobbin is housed in a shield casing made of magnetic metal, and each leg of the bobbin is inserted into each through hole formed in the bottom wall at the bottom wall side end of the shield casing. .
[0004]
[Problems to be solved by the invention]
By the way, in the cross coil type indicating instrument, the bobbin is accommodated in the shield casing by press-fitting the outer peripheral wall of the bobbin into the inner peripheral wall of the shield casing. In addition, there is usually a gap between the outer peripheral surface of the bottom wall side end portion of each leg of the bobbin and the inner peripheral surface of each through hole portion of the bottom wall.
[0005]
On the other hand, since the bobbin is made of resin, if the temperature or heat of the bobbin fluctuates up and down due to its history phenomenon (hereinafter referred to as temperature history phenomenon or heat history phenomenon), the bobbin contracts irreversibly. End up.
Specifically, the entire bobbin contracts from its outer peripheral wall toward the axis. At this time, each leg of the bobbin also contracts from its outer peripheral surface toward its respective axis. Then, after contracting in this way, the entire bobbin does not return to the original shape and remains contracted.
[0006]
For this reason, as described above, even if the outer peripheral wall of the bobbin is press-fitted into the inner peripheral wall of the shield casing, when the bobbin contracts due to the temperature history phenomenon, the fitting between the bobbin and the shield casing becomes loose. End up. Along with this, backlash occurs between the outer peripheral wall of the bobbin and the inner peripheral wall of the shield casing.
Accordingly, there is a problem in that a positional deviation occurs between the bobbin and the shield casing, the balance of the magnetic shielding action of the shield casing is lost, and the indication accuracy is lowered. In addition, there is a problem in that contact noise is generated due to a displacement between the bobbin and the shield casing during mechanical vibration of the cross coil type indicating instrument.
[0007]
Therefore, in order to cope with the above, the present invention devised the shape of the leg of the resin bobbin and the bottom wall of the magnetic metal shield casing so that the bobbin is accommodated in the shield casing by press fitting. Therefore, an object of the present invention is to provide a cross coil type indicating instrument which prevents the occurrence of play between the bobbin and the shield casing even if it contracts due to a temperature history phenomenon.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, according to the first and third aspects of the present invention, each projection penetrates through the bottom wall of the shield casing from one axial end of each leg of the bobbin toward each other. It protrudes so as to contact the inner peripheral surface of the hole.
[0009]
As a result, even if the entire bobbin contracts from its outer peripheral wall toward the axis due to fluctuations in the temperature of the cross coil type indicator due to the temperature history phenomenon, the shape deformation due to the temperature of the shield casing is compared to the shape deformation of the bobbin. Since it can be almost ignored, each protrusion remains in contact with the inner peripheral surface of each through hole at a position facing each other.
Therefore, even if the bobbin contracts as described above, no positional deviation occurs between the bobbin and the shield casing, and no play occurs.
[0010]
As a result, when the balance of the magnetic shielding action of the shield casing is lost, the accuracy of the indication is reduced, or when the cross coil type indicator instrument is mechanically vibrated, a contact sound is generated due to the displacement between the bobbin and the shield casing. Absent. In addition, according to the inventions of claims 2 and 3, each axial end portion of each projection is directed in the direction opposite to the direction facing each other from the inner peripheral surface of each through hole portion of the bottom wall of the shield casing. It protrudes so that it may contact | abut to the outer peripheral surface.
[0011]
Also by this, the same effect as that of the first aspect can be achieved. According to the third aspect of the present invention, the interval between the opposing portions of the protrusions is the shortest interval between the inner peripheral surfaces of the through-hole portions of the shield casing before the temperature history phenomenon acts on the bobbin. Is set to be slightly smaller (that is, small enough to allow the pair of legs to be inserted into the through-holes at one axial end thereof) , and the axial center distance between the axial one ends is It is set to be twice or more the interval between the axial center at one end in the axial direction and the opposing portion of the protrusion.
[0012]
Thereby, even after the bobbin contracts, the abutting action of the projection can be reliably maintained, and no positional deviation occurs between the bobbin and the shield casing, and no play occurs.
As a result, the operational effect of the invention according to claim 1 or 2 can be achieved more reliably.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 3 . FIG. 1 shows an example in which the present invention is applied to a cross coil type indicator for a vehicle. This cross coil type indicating instrument includes a resin hollow bobbin 10 as a housing, and this bobbin 10 is housed and held in a magnetic metal shield casing 20 having a U-shaped cross section. It is attached to a circuit board (not shown).
[0014]
Here, before the temperature history phenomenon or the heat history phenomenon acts on the bobbin 10, the bobbin 10 is accommodated in the shield casing 20 by coaxially press-fitting the outer peripheral wall of the bobbin 10 into the inner peripheral wall of the shield casing 20. Is retained. In addition, the thermal expansion coefficient of the forming material of the bobbin 10 is so large that the thermal expansion coefficient of the shield casing 20 can be ignored. The forming material of the bobbin 10 may be various resins such as a thermoplastic resin and a thermosetting resin.
[0015]
A pair of legs 10a are formed on the outer peripheral wall of the large-diameter hollow portion 11 of the bobbin 10 so as to face each other, and another pair of legs 10b are formed to face each other. Yes. Each leg 10a, 10b is located at equiangular intervals.
And each leg 10a, 10b is inserted in each penetration part 21a, 21b formed in the bottom wall 21 of the shield casing 20 corresponding to these in the axial direction one end part 12, 13, respectively by loose fitting. Has been.
[0016]
Here, one end 12 in the axial direction of each leg 10a is inserted into each penetration 21a of the bottom wall 21 in the axial direction, and one end 13 in the axial direction of each leg 10b is inserted in each penetration 21b in the bottom wall 21. Each is inserted in the axial direction.
Further, both cross coils 30 and 40 are wound around the outer wall of the large-diameter hollow portion 11 of the bobbin 10 so as to cross each other in a cross shape between the legs 10a and 10b. Each terminal is connected to the upper end of each terminal accommodated in each leg 10a, 10b.
[0017]
The pointer shaft 50 is coaxially inserted into the bobbin 10, and the pointer shaft 50 is rotatably supported at the lower end portion of the lower cylindrical small diameter portion 14 of the bobbin 10. The upper intermediate portion of the pointer shaft 50 is rotatably supported in the upper cylindrical small diameter portion 15 of the bobbin 10.
Thereby, the pointer shaft 50 is supported so as to be coaxially rotatable in the bobbin 10 and extends upward from the bobbin 10 at the upper end portion thereof.
[0018]
The magnet 60 is coaxially supported in the lower intermediate portion of the pointer shaft 50 in the large-diameter hollow portion 11 of the bobbin 10, and the magnet 60 generates a combined electromagnetic force from the cross coils 30 and 40. The pointer shaft 50 is rotated by receiving and rotating.
The scale plate 70 is attached to the bobbin 10 by fastening screws (not shown) to the other axial ends of the legs 10a and 10b. In addition, the pointer 80 is supported by the boss 81 by press-fitting coaxially from the outside to the upper end portion of the pointer shaft 50 extending through the central hole portion of the scale plate 70.
[0019]
Next, the structure of the principal part of this invention is demonstrated.
As shown in FIGS. 1 and 2, the both legs 10 a of the bobbin 10 are integrally provided with protrusions 12 a at their respective axial one ends 12, and the respective protrusions 12 a are provided at the respective axial one ends 12. It protrudes in a triangular shape from a part of the outer peripheral surface.
Here, each protrusion 12a extends from each axial end portion 12 to the opposite direction to the shrinking direction due to the temperature history phenomenon between each axial end portion 12 of each through hole 21a of the bottom wall 21 of the shield casing 20. It protrudes so as to come into contact with the inner peripheral surface.
[0020]
In other words, each projection 12a is in contact with the inner peripheral surface of each penetration portion 21a on a line connecting the tops of the projections 12a (opposite end portions of the projections 12a) between the axial end portions 12. (See FIGS. 1 and 2).
However, if the interval between the tops of the two protrusions 12a is A (see FIG. 2), the interval A is equal to each of the through holes 21a of the shield casing 20 before the temperature history phenomenon acts on the bobbin 10. It is somewhat smaller than the shortest distance C between the inner peripheral surfaces (see FIG. 3). Further, the interval W between the axial centers of the two axial end portions 12 (see FIG. 2) is an interval H (hereinafter referred to as a protrusion) between the axial center of the axial one end portion 12 and the top of the projection 12a of the axial one end portion 12. It is set to a value more than twice the height H of 12a).
[0021]
In the present embodiment configured as described above, when the temperature of the cross coil type indicator changes due to the temperature history phenomenon, the bobbin 10 contracts from the outer peripheral wall toward the axial center over the whole. At this time, each axial one end portion 12 contracts from its outer peripheral surface toward the axial center. Since the thermal expansion coefficient of the shield casing 20 is negligibly small as compared with that of the bobbin 10 as described above, the shape deformation due to heat can be ignored compared to the contraction deformation of the bobbin 10.
[0022]
Here, if the irreversible shrinkage rate of the resin constituting the bobbin 10 is k (> 0), the height H of each protrusion 12a is caused by the shrinkage associated with the temperature history phenomenon of each axial end portion 12 due to shrinkage. = H · (1-k).
Further, the interval W between the axial centers of the two axial end portions 12 is Wa = W · (1−k) due to contraction accompanying the temperature history phenomenon of each axial one end portion 12.
[0023]
Thus, before the temperature history phenomenon acts on the bobbin 10, the distance A between the tops of both protrusions 12a, which was A (= W−2H), becomes after the temperature history phenomenon acts on the bobbin 10. Ao = (W−2H) · (1−k) . As a result, when the change ΔA of the interval A due to the temperature history phenomenon is calculated, ΔA = (Ao−A) = (− k) · (W−2H).
[0024]
Here, as described above, since W ≧ 2H is set before the temperature history phenomenon acts on the bobbin 10, (W−2H) ≧ 0 is always satisfied.
Therefore, the change ΔA of the interval A due to the temperature history phenomenon always satisfies ΔA ≦ 0.
Therefore, the change ΔA of the interval A changes in the direction in which the degree of contact increases with respect to the inner peripheral surface of each penetrating portion 21a on the line connecting the tops of the protrusions 12a (that is, the direction of tightening). For this reason, each protrusion 12a will contact | abut strongly in the direction which mutually opposes to the internal peripheral surface of each penetration part 21a on the line | wire which connects the each top part.
[0025]
Thereby, each protrusion 12a is firmly abutted and maintained on the inner peripheral surface of each penetrating portion 21a symmetrically with respect to each axis of the bobbin 10 and the shield casing 20, so that the bobbin 10 and the shield casing 20 There is no misalignment between the two.
Therefore, even if the bobbin 10 contracts as described above, the balance of the magnetic shield action with respect to the magnet 60 and the two crossing coils 30 and 40 of the shield casing 20 is not lost, and the indication accuracy is not reduced. Further, during mechanical vibration of the cross coil type indicating instrument, there is no displacement between the bobbin 10 and the shield casing 20, and the generation of contact noise between the two can be prevented.
[0026]
In carrying out the present invention, in the above-described embodiment, the protrusion 12a is integrally formed on the axial end portion 12 of both legs 10a. Instead, the protrusion 12a is formed on the axial end portion 13 of both legs 10b. Corresponding protrusions may be formed integrally, and in addition to the protrusions 12a at the axial end portions 12 of both legs 10a, protrusions corresponding to the protrusions 12a are formed at the axial end portions 13 of both legs 10b. You may make it do.
[0027]
In the above embodiment, the projection 12a of each leg 10a has been described as an example projecting in a triangular shape from a part of the outer peripheral surface of each axial end portion 12, but the shape of each projection 12a is not limited thereto. May be changed as appropriate, and may be any shape as long as it protrudes from a part of the outer peripheral surface of each axial end portion 12.
Further, in the implementation of the present invention, unlike the above-described embodiment, the protrusions corresponding to the protrusions 12 a are formed at the temperatures of the axial end portions 12 from the inner peripheral surface of the through portions 21 a of the bottom wall 21 of the shield casing 20. Even if it protrudes so that it may contact | abut to the outer peripheral surface of each axial direction one end part 12 along each axial direction one end part 12 toward the shrinkage direction by a log | history, the effect similar to the said embodiment can be achieved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a cross coil type indicating instrument according to the present invention.
2 is a bottom view of a bobbin around which both crossed coils of FIG. 1 are wound. FIG.
3 is a bottom view of the shield casing of FIG. 1. FIG.
[Explanation of symbols]
10 ... bobbins, 10a, 10b ... legs, 12, 13 ... one end in the axial direction,
12a ... projection, 20 ... shield casing, 21 ... bottom wall,
21a, 21b ... hole, 50 ... pointer shaft, 60 ... magnet.

Claims (3)

A resin-made hollow bobbin having at least a pair of legs (10a, 10b) facing each other at its outer peripheral wall and extending along the axial direction;
A pointer shaft (50) supported coaxially and rotatably in the bobbin and extending from the bobbin;
A magnet (60) supported in an intermediate portion of the pointer shaft in the bobbin;
Crossed coils (30, 40) that are wound around the bobbin between the legs and generate electromagnetic force that rotates the magnet in response to an inflow current;
A magnetic metal shield casing (20) formed by press-fitting the bobbin,
The pair of legs are inserted into the respective through-hole portions (21a, 21b) formed in the bottom wall (21) of the shield casing correspondingly at one axial end portion thereof,
The cross coil type indicating instrument in which each protrusion (12a) protrudes so as to contact the inner peripheral surface of each through-hole portion in a direction facing each other from each axial end portion. A resin-made hollow bobbin having at least a pair of legs (10a, 10b) facing each other at its outer peripheral wall and extending along the axial direction;
A pointer shaft (50) supported coaxially and rotatably in the bobbin and extending from the bobbin;
A magnet (60) supported in an intermediate portion of the pointer shaft in the bobbin;
Crossed coils (30, 40) that are wound around the bobbin between the legs and generate electromagnetic force that rotates the magnet in response to an inflow current;
A magnetic metal shield casing (20) formed by press-fitting the bobbin,
The pair of legs are inserted into the respective through-hole portions (21a, 21b) formed in the bottom wall (21) of the shield casing correspondingly at one axial end portion thereof,
The cross coil type indicating instrument in which each protrusion protrudes from the inner peripheral surface of each through-hole portion in a direction opposite to the direction facing each other so as to abut on the outer peripheral surface of each axial end portion. The interval between the opposing portions of the protrusions is such that the pair of legs can be inserted into the through-hole portions at one end in the axial direction before the temperature history phenomenon acts on the bobbin. It is small fence set than the shortest distance between the inner peripheral surface of the part,
The axial center interval between each axial end portion is set to be twice or more the interval between the axial center end portion and the opposing portion of the projection. The cross coil type indicating instrument described in 1.

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