JPS5816703B2 - Moving magnet type instrument - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a movable magnet type instrument that allows easy finger adjustment.

It is necessary to adjust the index of the pointer so that the measured value is displayed correctly in various meters, but adjusting the index of the movable magnet type meter is extremely difficult.

The conventional index adjustment method for movable magnet type instruments is as follows: ■, Demagnetization of permanent magnet for excitation 2. Demagnetizing the movable magnet 3. Change of magnetic coupling coefficient of excitation magnetic field 4. Changing the magnetic coupling coefficient of the driving magnetic field etc. were being carried out.

However, the method of adjustment by demagnetization requires equipment for demagnetization, which has the drawback of increasing the size of the manufacturing equipment, and it is extremely difficult to make fine adjustments. However, there were drawbacks such as the need for equipment for this purpose.

Furthermore, the materials used for the permanent magnets have been limited to cast magnets that can be relatively easily magnetized and demagnetized.

On the other hand, in the method of adjusting by changing the magnetic coupling coefficient, it is necessary to provide an adjustment mechanism in the meter itself, which increases the size of the meter and requires hot wire for adjustment, which hinders productivity. There were drawbacks.

The present invention solves the above-mentioned drawbacks and provides a movable magnet type instrument that allows for extremely easy index adjustment without requiring special skill or large equipment such as a magnet attachment/detachment device. It was done for a purpose.

An embodiment of the present invention will be described in detail below with reference to FIGS. 1 to 6.

FIG. 1 is a cross-sectional view showing an embodiment of a movable magnet type instrument according to the present invention, and FIG. 2 is a longitudinal cross-sectional view thereof.

In these figures, reference numeral 11 denotes a movable magnet, which is rotatably supported by a shaft 12 provided at the center, and has N, S, and two poles magnetized in parallel in the radial direction.

The shaft 12 is held by a bobbin 14 surrounding the rotation of the movable magnet 11, and a pointer 13 is fixed to the upper end of the shaft 12 protruding from the top of the bobbin 14.

An excitation permanent magnet 15.15' is attached to the bobbin 14 so as to face the magnetic pole of the movable magnet 11, and a drive coil is placed above the excitation permanent magnet 15.15' on the X axis. 16 are wound.

In this embodiment, two excitation permanent magnets 15 and 15' are provided, but the number may be one, or two or more may be provided.

Furthermore, in this embodiment, the drive coil 16 is wound around the excitation permanent magnet 15, 15';
Excitation permanent magnets 15 and 15' may be provided on the coiled magnet 6.

The bobbin 14 is a bearing part for the movable magnet 11, and 1. It also serves as a winding frame for the drive coil 16 and a base for assembling other parts, but these are housed in a shield case 17 so as not to be affected by external magnetic fields.

The movable magnet 11 in this shield case 17
A pair of finger index adjustment screws 18, 18' made of magnetic material and whose advancing and retreating directions face the magnetic neutral point of the movable magnet 11 are screwed onto opposing positions equidistant from both poles.

The magnetic neutral point of the movable magnet 11 refers to the center of the movable magnet 11, that is, the non-magnetized point where the S pole, which is magnetized in parallel in the radial direction, changes to the N pole. , 0° to 180° is the S pole, 180° to 360° (
0°) is the north pole, and its waveform is as shown in FIG. 8, so the magnetic neutral point is at rAJ.

According to the present invention, the above-mentioned adjusting screw 1
By advancing 8.18' into the shield case 17 or retracting it to the outside, the index of the pointer 130 is adjusted.Next, these operations will be explained.

The drive coil 16 is wound on the X axis as shown,
The magnetic flux ±φC generated by the flow of the measurement current is the excitation torque generated by the excitation permanent magnets 15 and 15', which is applied to the movable magnet 1.
90° to the magnetic flux φF generated by acting on
It has a phase difference of ＋ in the figure
Since the X-axis vector is φ+■ and φF is constant, these combined vectors are φA as shown in Figure 4.
One deflection angle is θ or ■.

This deflection angle θ and ■ are the rotation angles of the movable magnet 11 based on the measurement current ■ flowing through the drive coil 16, in other words, the deflection angle of the pointer 13.

By the way, if the deflection angle on the scale plate that the pointer 13 should indicate when a measurement current of 10 mm flows is θ+1, then it is necessary to correct the above-mentioned θ+1 to θ+×o.

This correction is carried out by adjusting screws is, is'.

That is, the envious movable magnet 1 shown in FIGS. 7 and 8
The equivalent magnetic circuit of FIG. 1 incorporating 1 is as shown in FIG. 9. Therefore, by moving the adjusting screws 18 and 18' back and forth, φF in FIG. 3 can be decreased - φF can be generated. In addition, as shown in Fig. 10, the magnetic flux φ18 caused by the drive coil 16 forms a closed loop passing from the center of the coil through the screw 18°187 and the shield case 17, so the magnetic flux φ18' is caused by the driving coil 16. When the coil is brought closer to the center of the drive coil 16, the magnetic resistance of the coil magnetic flux φ16 decreases, and the apparent φ
+■ increases by 10Δφ+■ (on the contrary, screws 18 and 18
' is retracted and moved away from the center of the drive coil 16, φ
+1 decreases by one Δφ or ■).

The desired deflection angle θ+I as shown in FIG. 5 can be obtained by decreasing φF and increasing φ and □ by moving the screws 18 and 18' back and forth, but this is due to the difference between φF-φp/ and φ+
The composite vector with Δφ+1 is φB, and the deflection angle at this time is θ+■o.

In addition, in the fingertip adjustment by these screws 18 and 18', the contribution rate of 10Δφ+I is about 10% and the contribution rate of -φF/ is about 90%, so the fingertip adjustment by screws 18 and 18' is mainly made by one This is done by φFl.

Note that even if a measurement current of 1 is applied to the drive coil 16, the deflection angle of the pointer 13 can be adjusted to match the scale plate by adjusting the adjustment screws 18 and 18' in the same manner.

For reference, measurement data obtained when the present invention is applied to a general automotive ammeter is shown in Fig. 6 for a shunt type ammeter with an internal resistance of 148 mΩ and a full scale IA.

In this figure, 211fi shows the index characteristic before adjustment, 22 shows the appropriate index characteristic, and 23 shows the maximum sensitivity index characteristic. The range of adjustment is approximately ±40%.

As described above, according to the present invention, it is possible to provide a movable magnet type instrument in which the finger index can be adjusted simply by operating an adjustment screw, and the adjustment does not require special skill, and the instrument itself does not need to be large-sized. It is not necessary, and furthermore, it does not require large manufacturing equipment for magnetization and demagnetization, and its effects are remarkable.

It goes without saying that the present invention is not limited to the above-mentioned embodiment, but can be implemented with various modifications without departing from the scope of the invention.

Further, the present invention can be implemented in a crossed coil type movable magnet type meter, and similar effects can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of a movable magnet type instrument according to the present invention, FIG. 2 is a vertical cross-sectional view thereof, and FIGS. 3 to 5 are vector diagrams for explaining the present invention in detail. , FIG. 6 is a diagram showing an example of the characteristics of a meter to which the present invention is applied, FIG. 7 is a diagram showing the magnetization relationship between the N pole and S pole of the movable magnet, and FIG. 8 is a diagram showing the waveform thereof. 9 and 10 are magnetic circuit diagrams for explaining the present invention in detail.

Claims (1)

[Claims] 1. In a movable magnet type instrument that applies excitation torque from the excitation magnetic flux generation means and drive torque generated by the measurement current flowing through the drive coil to a movable magnet, the excitation magnetic flux generation means, the drive coil, and the movable magnet are accommodated. Screwing a pair of index adjustment magnetic screws whose forward and backward directions are directed toward the magnetic neutral point of the movable magnet at opposing positions equidistant from both poles of the movable magnet in the shield case;
A movable magnet type instrument characterized in that a demagnetizing torque is generated relative to the excitation torque by the excitation magnetic flux generating means by advancing and retracting the screw.