JP3528353B2 - Cross-coil instrument - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a cross-coil type instrument for highly accurate measurement.

[0002]

2. Description of the Related Art Conventionally, a cross-coil type meter which operates by a magnetic action of an external magnet and a set of cross-coils has been known as one of constant-current driven meters such as a circuit-driven ammeter (described later). See FIG. 2).

As shown in FIG. 2, which will be described later, the cross-coil type instrument has coils 11 and 12 wound around a bobbin 140 containing a movable magnet, and the rotary shaft 1 of the movable magnet.
50 is provided with a pointer 15. The bobbin 140 is housed in a magnetic shield case 16, and an external magnet 13 is provided between the bobbin 140 and the case 16 so as to have a magnetic effect on the movable magnet. .

As shown in FIGS. 10 and 11, in the coil circuit 10 constituted by the coils 11 and 12, a current I supplied from a sensor to be measured such as a pressure sensor flows and the magnitude of the current I changes. Proportional coil circuit magnetic fields B1, B2, B3 are generated. On the other hand, the external magnet 1
3, the external magnet magnetic field C corresponding to the magnetic force of the external magnet 13
Occurs.

Then, a composite magnetic field D1, D2, D3 is generated from both the magnetic fields B1, B2, B3 and C. Therefore, the pointer 15 attached to the movable magnet 14 rotates in accordance with the combined magnetic fields D1, D2, D3. As shown in FIG. 11, the directions of the synthetic magnetic fields D1, D2 and D3 change according to the magnitudes of the coil circuit magnetic fields B1, B2 and B3. Therefore, in the cross coil type instrument 9 having the above structure, the coil circuit 10 It is possible to measure the magnitude of the electric current flowing through.

[0006]

However, the magnetic force of the external magnet 13 changes as the temperature rises and falls. That is, the magnetic field of the external magnet has a temperature coefficient. However, since the coil circuit 10 is driven by a current having a constant magnitude, the magnitude of the magnetic field generated by the coil circuit 10 does not change.

That is, when the external magnet is a ferrite magnet, the temperature coefficient of magnetic force is about -0.18% / ° C.

Therefore, when the ambient temperature (ambient temperature) of the cross-coil type instrument 9 changes, the external magnet 13 causes the external magnet magnetic field C1 to change according to the change in the atmospheric temperature, as shown in FIG. , C2, C3. That is, when the external magnet 14 is a ferrite magnet and the ambient temperature changes from 20 ° C to 80 ° C, the magnetic field is about -1.
It changes by 0.8%. When the temperature changes from 20 ° C to -30 ° C, the magnetic field changes by about + 9.0%.

At this time, a current having a constant magnitude flows in the coil circuit 10, so that the coil circuit magnetic field B2 is generated.
As a result, the external magnet magnetic fields C1, C2, C3 and the coil circuit magnetic field B2 having a constant magnitude generate synthetic magnetic fields E1, E2, E3 having different directions and magnitudes.

The above-mentioned pointer 15 is the synthetic magnetic field E1, E2, E
Since it rotates according to 3, the situation in which the pointing position of the pointer differs even though the same amount of current flows. In this case, the pointing position of the pointer 15 observed in the cross coil type instrument 9 is not proportional to the value of the current to be measured, and accurate measurement cannot be performed.

In view of the above problems, the present invention aims to provide a cross-coil type instrument capable of performing accurate measurement regardless of changes in ambient temperature.

[0012]

According to the present invention, a coil is wound around a bobbin containing a movable magnet, a pointer is provided on the rotary shaft of the movable magnet, and the bobbin is housed in a case for magnetic shielding. In a cross-coil type instrument in which an external magnet that mutually exerts a magnetic action on the movable magnet is disposed between the coil and the case, the temperature coefficient of the current value flowing through the coil is included in the coil. The bypass circuit for changing the temperature of the external magnet according to the temperature coefficient
Tare connected in parallel to the coil is, and the bypass
The circuit is a cross-coil type instrument characterized by having a fixed resistor and a diode .

Next, the operation of the present invention will be described. In the cross-coil type instrument of the present invention, the bypass circuit is provided in parallel with the circuit provided with the coil, that is, the coil circuit. Therefore, (current flowing in the cross coil type meter) = (bypass circuit current) + (coil circuit current). The current flowing through the cross-coil type instrument is a current supplied from a sensor of a measurement target such as a pressure sensor, and means a constant current according to the phenomenon of the measurement target. Also, the voltages in the coil circuit and the bypass circuit are equal.

Therefore, as shown in Embodiment 1 described later, by setting the bypass resistance in the bypass circuit to an appropriate value, the coil circuit current changes in accordance with the temperature coefficient of the external magnet. . That is, the coil circuit current has a temperature coefficient corresponding to that of the external magnet. Therefore, accurate measurements can be made according to the atmosphere in which the crossed coil type instrument is placed.

The coil is composed of a conductor wire made of an electric conductor such as a copper wire. The bypass circuit can be composed of, for example, an element and a lead wire for connecting the element to the coil circuit. The element has a temperature coefficient equal to or lower than the temperature coefficient of the resistance value of the conductive wire forming the coil.

Specific examples of the above element are shown below. That is, the bypass circuit, having a fixed resistor and a diode
It Alternatively, the bypass circuit, that having a zener diode having a fixed resistor and a negative temperature coefficient.

The temperature coefficient of the resistance value of the fixed resistor is generally equal to zero. Further, the temperature coefficient of the internal resistance value of the diode is negative (eg Toshiba 1S158
8 was -0.256% / ° C). Further, since the Zener diode has a negative temperature coefficient up to the Zener voltage, it is necessary to appropriately select a Zener diode according to the usage environment of the cross coil type instrument to configure the bypass circuit.

Since the fixed resistor is an inexpensive electric component,
The manufacturing cost and the like can be made almost the same as the conventional one.
Further, by using a diode and a Zener diode in combination with the fixed resistor to form a bypass circuit, the temperature coefficient can be corrected more actively.

Further, since the resistance value of the thermistor resistor has a temperature coefficient, the temperature coefficient of the external magnet and the temperature coefficient of the coil circuit current can be accurately matched even in a wide temperature range.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Reference Example 1 FIG. 1 shows a cross coil type instrument according to a reference example of the present invention.
~ It demonstrates using FIG. As shown in FIGS. 1 and 2, in the cross-coil type instrument 1 of this example, the coils 11 and 12 are wound around a bobbin 140 containing a movable magnet, and a pointer 15 is provided on a rotary shaft 150 of the movable magnet. In addition, the bobbin 140 is housed in the magnetic shield case 16. Further, an external magnet 13 is provided between the bobbin 140 and the case 16 so as to have a mutual magnetic action with the movable magnet.

In the coil circuit 10 constituting the coils 11 and 12, the temperature coefficient of the current value (coil circuit current Ic) flowing in the coil circuit is changed in accordance with the temperature coefficient of the external magnet 13. The bypass circuit 2 is connected in parallel to the coils 11 and 12. Note that Fig. 1
Reference numeral 19 is a ground connected to the coil circuit.

In the cross coil type instrument 1, the coils 11 and 12 are made of copper wires having a resistance value of a temperature coefficient of + 0.393% / ° C. Further, the bypass circuit 2 has a fixed resistor 21, and the fixed resistor 21
The temperature coefficient of the resistance value of is almost zero.

A constant current I is applied to the cross coil type instrument 1. The constant current I is supplied from a sensor such as a pressure sensor, and means a current according to the phenomenon of the measurement target. Then, the constant current I is divided into a coil circuit current Ic and a bypass circuit current Ib flowing through the coil circuit 10 and the bypass circuit 2.

Next, the function and effect of this example will be described. In the cross-coil type instrument 1 of this example, a constant current I having a constant magnitude according to the measurement phenomenon flows. The bypass circuit 2 is connected in parallel to the coil circuit 10. Therefore, the sum (Ic + Ib) of the coil circuit current Ic and the bypass circuit current Ib is always the constant current I.
Further, the voltages in the coil circuit 10 and the bypass circuit 2 are equal.

Therefore, the equation (1) represented by Ic * Rc = Ib * Rb = (I-Ic) * Rb (1) is established. Further, from the equation (1), the following equation (2) showing the relationship between the Ic and Ib is established. Ic = I × Rb / (Rb + Rc) (2) where Rc is the resistance value of the coil circuit 10 and Rb is the resistance value of the bypass circuit 2. In calculating Rc and Rb, the resistance value of the portions other than the coils 11 and 12 and the fixed resistor 21 is regarded as 0.

Next, assuming that Rc is the resistance value of the coil circuit 10 at an ambient temperature of 20 ° C., the resistance value Rc of the coil circuit 10 increases with the ambient temperature, and the resistance value Rc (21) of the coil circuit 10 at a temperature of 21 ° C. Is the coil 1
The temperature coefficient of the resistance value of the copper wires constituting 1, 12 is 0.39
Since it is 3%, it can be seen that Rc (21) = 1.03993 × Rc (3).

Therefore, the coil circuit current at an ambient temperature of 20 ° C. is Ic (20), the coil circuit current at 21 ° C. is Ic (21), and the coil circuit resistance value at a temperature of 20 ° C. is Rc (20), a coil circuit at 21 ° C. When the resistance value is 1.00393 × Rc (20), Ic (20) = I × [Rb / {Rb + Rc (20)}] (4) Ic (21) = I × [Rb / {Rb + 1. It can be seen that 00393 × Rc (20)}] (5).

By the way, the magnitude of the magnetic field generated by the coil circuit current Ic is proportional to the magnitude of the coil circuit current Ic. Therefore, in order for the above magnetic field to have a temperature coefficient (−0.18% / ° C.) equivalent to the magnetic field of the external magnet 13,
It suffices that the temperature coefficient of the coil current Ic be the same as the temperature coefficient of the magnetic field of the external magnet. Therefore, it can be understood from the above equations (4) and (5) that {Ic (21) -Ic (20)} / Ic (20) =-0.0018 (6).

From the above, it can be seen that Rb = 1.179Rc. That is, the resistance value R of the coil circuit 10
1.1794 times larger than c (that is, 1.17 times)
94RcΩ) and the fixed resistor 21 having a bypass circuit 2
At least the ambient temperature of 20 ° C to
When changing between 21 ° C., the rate of change of the magnetic field of the external magnet 13 and the rate of change of the magnetic field generated by the coils 11 and 12 match. The above calculation is 20 ~ 21 ℃
Although the example of the narrow range is shown, this is the same for a wide temperature range (for example, ± 10 ° C.).

Therefore, the inclination of the pointer 13 of the cross-coil type instrument 1 changes purely in proportion to the magnitude of the constant current I, that is, the current supplied from the sensor to be measured.
Therefore, in this example, it is possible to provide the cross-coil type instrument 1 capable of performing accurate measurement regardless of changes in the ambient temperature.

FIG. 3 shows a diagram in which the horizontal axis represents the atmospheric temperature change ΔT with respect to the reference temperature, and the vertical axis represents Rb / Rc (optimum resistance ratio) derived by calculation as described above. As is known from the figure, the value of the optimum resistance ratio fluctuates according to ΔT. Since the resistance value of the fixed resistor 21 does not depend on temperature, the ratio of the resistance value of the fixed resistor to the resistance value of the coil circuit may deviate from the optimum resistance ratio depending on the change of the ambient temperature. However, as shown in Reference Example 2 to be described later, even if the resistance ratio is slightly different from the optimum resistance ratio, the cross-coil type meter 1 shown in this example has much higher temperature than the conventional cross-coil type meter. Small dependency and excellent measurement accuracy.

Reference Example 2 As shown in FIGS. 4 to 6, this example is intended to compare and explain the cross coil type instrument according to Reference Example 2 together with a comparative example. This cross-coil type instrument has the same configuration as that shown in Reference Example 1. That is, the temperature coefficient of the external magnet is −0.18% / ° C., the temperature coefficient of the resistance value of the copper wire forming the coil is 0.393% / ° C., and the temperature coefficient of the fixed resistor is 0. Furthermore, the resistance value Rc of the coil circuit is 2
300Ω at 0 ° C, resistance value of bypass circuit Rb is 3
It is 20Ω.

On the other hand, the cross-coil type meter according to the comparative example is constituted by an external magnet having the same structure and the same temperature coefficient as the reference example 2 except that it does not have a bypass circuit.

Next, a current was applied to the above-mentioned two cross-coil type instruments, and the change in magnetic force generated by the coil and the external magnet was measured while changing the ambient temperature from -30 ° C to 100 ° C. The results are shown in FIGS. 4 and 5.

As shown in FIG. 4, in the cross-coil type instrument according to the second reference example , the change in magnetic force of the coil was substantially the same as the change in magnetic force of the external magnet. However, as shown in FIG. 5, in the cross coil type instrument according to the comparative example,
Although the change in magnetic force of the coil circuit is almost zero,
It was found that the magnetic force of the external magnet decreased in proportion to the increase in temperature.

Further, FIG. 6 is a diagram in which magnetic force ratio = {(magnetic force of external magnet) / (magnetic force of coil)} in the reference example 2 and the comparative example is plotted on the ordinate and the ambient temperature is plotted on the abscissa. Indicates. As can be seen from the figure, in Reference Example 2 ,
It can be seen that the coil has a magnetic force change that approximately matches the magnetic force change of the external magnet.

The resistance value of the bypass circuit of the cross coil type instrument according to this embodiment is 320Ω as described above.
However, according to the optimum resistance value shown in Reference Example 1,
At least when the change of the ambient temperature is within the range of 20 ° C to 21 ° C, the resistance value of the bypass circuit is 353.8Ω (3
00Ω × 1.1794 times). That is,
The resistance value of the bypass circuit of the above-mentioned cross coil type instrument (320
Ω) is different from the optimum resistance value (353.8 Ω). However,
According to the measurement results in this example, have a somewhat different resistance value than the optimum resistance value, it was found that the object of their can be sufficiently achieved.

Embodiment 1 As shown in FIGS. 7 to 9, this embodiment will explain the structure of a bypass circuit using various elements. Figure 7
A bypass circuit 2 including a fixed resistor 21 and a diode 22 is provided in the coil circuit 10 shown in FIG.

The coil circuit 10 shown in FIG. 8 is for reference only.
As shown, a bypass circuit 20 including a thermistor resistor 23 is provided. The coil circuit 10 shown in FIG. 9 is provided with a bypass circuit composed of a fixed resistor 21 and a Zener diode 24. Others are the same as those in Reference Example 1. Although various elements are arranged one by one in FIGS. 7 to 9, a plurality of each element may be arranged.

In the bypass circuit 2 shown in FIG. 7 of the present example, the internal resistance of the diode 22 has a negative temperature coefficient, so that the resistance value of the bypass circuit 2 can be set large. As a result, of the current of the cross coil type instrument, the bypass circuit 2
The bypass circuit current that is shunted to the coil circuit 10 is reduced.
It is possible to increase the coil circuit current that is shunted to.
Therefore, the driving torque of the cross-coil type instrument increases,
Accuracy is improved.

For example, the resistance value of the coil circuit Rc = 300Ω Temperature coefficient = + 0.393% / ° C. Internal resistance value of the diode = 77Ω Temperature coefficient = −0.256% / ° C. Ambient temperature change = 1 ° C. (initial 20 ° C. change 21 ° C. later), the optimum resistance value is Rb = 1.181 × Rc. In this case, the resistance value of the bypass circuit 2 is 1.1810 × 300 + 77 = 431.3Ω, and the resistance value of the bypass circuit 2 can be set large.

Further, in the bypass circuit 2 shown in FIG. 8 as a reference example, the internal resistance of the Zener diode 24 has a larger internal resistance value and a larger negative temperature coefficient than that of a normal diode. The resistance value can be set larger. As a result, of the currents of the cross-coil type instrument, the bypass circuit current shunting to the bypass circuit 2 can be made small and the coil circuit current shunting to the coil circuit 10 can be made large. Therefore, the driving torque of the cross-coil type instrument is increased and the accuracy is improved.

For example, the resistance value of the coil circuit Rc = 300Ω Temperature coefficient = + 0.393% / ° C. Zener diode internal resistance value = 269Ω Temperature coefficient = −0.66% / ° C. (in case of Zener voltage 3V specification) Ambient temperature When the change is 1 ° C. (initial 20 ° C. and change 21 ° C.), the optimum resistance value is Rb = 16.774 × Rc. In this case, the resistance value of the bypass circuit 2 is 16.774 × 300 + 269 = 5301.2Ω, and the resistance value of the bypass circuit 2 can be set large.

The temperature coefficient of the in the bypass circuit 2 shown in FIG. 8 of the resistance value of the thermistor resistor 23 having a temperature coefficient, even in a wide temperature range, the temperature coefficient of the external magnet and accurately coil circuit current Can be matched. And other, either case of Figs. 7 to 9, Reference Example 1
It has the same effect as.

[0045]

As described above, according to the present invention, it is possible to provide a cross-coil type instrument capable of performing accurate measurement regardless of changes in ambient temperature.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a bypass circuit of a cross coil type meter in Reference Example 1.

FIG. 2 is a perspective view of a cross coil type instrument in Reference Example 1.

FIG. 3 is a diagram showing a relationship between an optimum resistance ratio and a change in ambient temperature with respect to a reference temperature in Reference Example 1.

[4] in the reference example 2, graph showing the relationship between the magnetic force change and the ambient temperature in the coil and the external magnet intersection difference coil type meter.

FIG. 5 is a diagram showing a relationship between a change in magnetic force between a coil and an external magnet of a cross coil type meter according to a comparative example in Reference Example 2 and an ambient temperature.

[6] according to Example 2 and specific Comparative Examples, graph showing the relationship between the force ratio and the ambient temperature at the cross coil type meter.

FIG. 7 is an explanatory diagram of a bypass circuit of a cross coil type instrument according to the first embodiment.

FIG. 8 is an explanatory diagram of a bypass circuit of a cross coil type meter as a reference in the first embodiment.

FIG. 9 is an explanatory diagram of a bypass circuit of another cross coil type instrument according to the first embodiment.

FIG. 10 is an explanatory view of a cross coil type instrument in a conventional example.

FIG. 11 is an explanatory diagram showing a composite magnetic field generated between a magnetic field generated in a coil and a magnetic field generated in an external magnet according to the magnitude of a flowing current in a conventional example.

FIG. 12 is an explanatory diagram showing a problem in the conventional example.

[Explanation of symbols]

1. ． ． Crossed coil type instrument, 11, 12. ． ． coil,
13. ． ． External magnet, 140. ． ． Bobbin, 15. ． ．
Guidelines, 150. ． ． Axis of rotation, 16. ． ． Case,
2. ． ． Bypass circuit, 21. ． ． Fixed resistor, 2
2. ． ． Diode, 23. ． ． Thermistor resistor, 2
4. ． ． Zener diode,

Claims (2)

(57) [Claims] 1. A coil is wound around a bobbin containing a movable magnet, and a pointer is provided on the rotating shaft of the movable magnet, and the bobbin is housed in a case for magnetic shielding, and the bobbin is provided between the case and the case. In the cross-coil type instrument in which an external magnet that mutually exerts a magnetic action on the movable magnet is arranged, the temperature coefficient of the current value flowing in the coil is set to the external magnet. A cross-coil type instrument characterized in that a bypass circuit for changing the temperature coefficient of is connected in parallel to the coil, and the bypass circuit has a fixed resistor and a diode. 2. A coil is wound around a bobbin containing a movable magnet, a pointer is provided on the rotary shaft of the movable magnet, and the bobbin is housed in a case for magnetic shielding, and further between the bobbin and the case. In the cross-coil type instrument in which an external magnet that mutually exerts a magnetic action on the movable magnet is arranged, the temperature coefficient of the current value flowing in the coil is set to the external magnet. wherein the bypass circuit for changing in correspondence with the temperature coefficient, Yes connected in parallel to the coil, and upper Symbol bypass circuit having a zener diode having a fixed resistor and a negative temperature coefficient of A crossed coil type instrument.