JPH11101824A - Current sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a current sensor by which a restriction in its mounting operation can be relaxed sharply by a method wherein a saturable magnetic substance ring core on which a primary coil and a secondary coil are wound is mounted on a signal wire which is formed on the surface of a board. SOLUTION: A square spiral signal wire 4 is formed on the surface of a coil board 20, and a sensor chip C is mounted on, and fixed to, the formation face of the signal wire 4. The sensor chip C has a structure in which a saturable magnetic-substance ring core 1 is installed on the surface of a board 10 and in which a primary coil 2 for excitation and a secondary coil 3 for reception are wound. At this time, a positional relationship in which one side part of the square of the signal wire 4 is passed through the center of the saturable magnetic-substance ring core 1 is set. Both ends of the respective coils 2, 3 are connected to pads 2a', 2b', 3a', 3b' on the surface of the coil board 20. Then, the pads 2a', 2b' are connected to the supply circuit of a high-frequency signal for excitation, a current to be measured flows to pads 4a, 4b of the signal wire 4, and a voltage value across both ends is computed by a measuring and computing circuit to which the pads 3a', 3b' are connected. Thereby, it is sufficient that the board 20 on which the signal wire 4 is formed is mounted on a required place, and a restriction in the mounting operation of a current sensor can be relaxed sharply.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a current sensor,
In particular, the present invention relates to a fail-safe sensor for monitoring a movable state of a movable portion of a machine tool, an industrial robot, or the like, and a current sensor suitable for use as a sensor for monitoring a current flowing through a specific electric wire of a circuit.

[0002]

2. Description of the Related Art For example, in an industrial robot or the like, in order to prevent a danger due to a malfunction of the robot during a teaching operation or a maintenance inspection operation, a current flowing through a driving motor of a movable portion of the robot is generally monitored. A fail-safe mechanism or an interlock mechanism that immediately shuts off the driving power of the robot when an electric current flows is provided.

As a sensor for such a current monitor,
Conventionally, a signal line through which a current to be monitored flows, a primary coil for excitation to which a high-frequency signal is supplied, and a secondary coil for reception are wound around a common saturable magnetic ring core, and a current flows through the signal line. By using the fact that the saturable magnetic ring core becomes saturated and the signal transmission from the primary coil for excitation to the secondary coil for reception is attenuated, a current sensor that detects the current flowing in the signal line is used. It has been proposed (JP-A-6-201733).

[0004]

In the above proposal, the saturable magnetic ring core is of a bulk type,
For the ring core, each one consisting of a conducting wire
The secondary coil, the secondary coil, and the signal line coil are wound in a helical shape, that is, alternately passing inside and outside the ring core.

[0005] Therefore, in manufacturing an actual device, it is necessary to insert and wind three types of conductors many times in a small ring, which requires a great deal of labor.

In order to solve such a problem, the present inventors have proposed a saturable magnetic ring core 1, an excitation primary coil 2 and a reception secondary coil 3 as schematically shown in FIG. Is formed into a chip by forming a thin film on a substrate 10 and a signal line 4 is locally wound around the chip C (Japanese Patent Application No. 8-138).
No. 269). By adopting the structure using such a thin film, the man-hour for manufacturing the sensor is greatly reduced, and the number of turns of the signal line necessary to make the saturable magnetic ring core saturated is significantly reduced. Successful.

However, even with such a structure in which a signal line is wound around a sensor chip, there is still a problem in that the process of winding the signal line still requires a time-consuming operation and is not suitable for mass production.

Further, since the structure in which the conductor is wound around the outer periphery of the chip is special, there is also a problem that, for example, bonding cannot be easily performed and mounting restrictions are increased.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and has as its object to provide a current sensor having a structure suitable for mass production and capable of greatly reducing restrictions during mounting.

[0010]

The structure for achieving the above object will be described with reference to FIG. 1 showing an embodiment. The current sensor of the present invention comprises a signal line 4 through which a current to be measured flows. Is formed on the surface of the substrate 20, and the saturable magnetic ring core 1 on which the primary coil for excitation 2 and the secondary coil 3 for reception are wound is mounted thereon.

Here, in the present invention, the primary coil 2 for excitation, the secondary coil 3 for reception, and the saturable magnetic ring core 1 do not necessarily need to be formed of a thin film, but as shown in FIG. In addition, it is preferable to adopt a configuration in which these are formed on another substrate 10 separately prepared by a thin film (Claim 2), since the structure is most suitable for mass production.

According to the present invention, by arranging a signal line close to a saturable magnetic ring core without winding the signal line around the saturable magnetic ring core, a saturable magnetic material is formed by a current flowing through the signal line. This saturates the ring core and enables its current to be detected. According to an experiment employing the configuration of the present invention, when the value of the current flowing through the signal line changes from 0 to 300 mA, the current value of the
An output signal of 0 could be obtained.

According to the structure of the present invention, the signal lines are formed on the surface of a printed circuit board or the like, and the primary and secondary lines are formed thereon.
Since it has a structure with a saturable magnetic ring core around which the next coil is wound, there is no need to wind signal wires,
In addition, since the mounting method may be such that the substrate on which the signal lines are formed is mounted at a necessary position, the restriction is greatly eased.

If a structure in which a primary coil for excitation, a secondary coil for reception, and a saturable magnetic ring core are formed on a separate substrate with a thin film is adopted, the structure as a whole is suitable for mass production. A mounting method equivalent to that of a normal sensor or a semiconductor chip becomes possible.

[0015]

FIG. 1 is a schematic plan view of an embodiment of the present invention, in which an upper insulating layer 6 of a sensor chip C described later is seen through. FIG. 2 is a schematic longitudinal sectional view of a main part of the sensor chip C.

The sensor chip C is formed on a surface of a substrate 10 made of, for example, quartz or the like, and a saturable magnetic ring core 1 made of a thin film is provided around the upper and lower insulating layers 5 and 6 for an excitation film made of a thin film. It has a structure in which the primary coil 2 and the receiving secondary coil 3 are formed in a spiral shape.

That is, as shown in FIG. 2, a lower pattern Pu of the primary coil 2 for excitation and the secondary coil 3 for reception is formed on the surface of the substrate 10. The pattern Pu of each of the coils 2 and 3 is, for example, a pattern as shown in FIG. 3A, on which the saturable magnetic ring core 1 is formed via the lower insulating layer 5. An upper insulating layer 6 is further formed on the ring core 1, and an upper pattern Pa of the excitation primary coil 2 and the receiving secondary coil 3 is formed on the upper insulating layer 6. The upper pattern Pa is connected to the lower pattern Pu by a contact hole H penetrating the lower insulating layer 5 and the upper insulating layer 6, and the primary coil 2 for excitation and the secondary coil 3 for reception are eventually A structure in which the periphery of the saturable magnetic ring core 1 is wound around the saturable magnetic ring core 1 via upper and lower insulating layers 5 and 6 in a three-dimensional shape as schematically shown in a perspective view in FIG. Have.

The material of the saturable magnetic ring core 1 is a material having a high magnetic permeability such as CoZrNb or Co amorphous, and the material of the primary coil 2 for excitation and the secondary coil 3 for reception employs Cu or the like. be able to.
The insulating layers 5 and 6 may be made of polyimide or the like.

On the other hand, the coil substrate 20 is formed of, for example, a printed circuit board, and has a signal line 4 formed of a rectangular spiral conductive pattern such as Cu on the surface thereof. And
The sensor chips C are mounted on the surface of the coil substrate 20 on which the signal lines 4 are formed, and are fixed to each other by an appropriate adhesive.

The positional relationship between the sensor chip C and the signal line 4 is as follows.
One side of the square of the signal line 4 is a saturable magnetic ring core 1
Are positioned so as to pass through the center.

Both ends of the excitation primary coil 2 and the reception secondary coil on the sensor chip C are connected to pads 2a, 2b and 3a, 3b formed on the surface of the substrate 10, and these pads are 2a, 2b, 3a, 3b are pads 2 formed on the surface of the coil substrate 20, respectively.
a ', 2b', 3a ', 3b' are connected by wires W.

Pads 4a and 4b are formed at both ends of the signal line 4 on the coil substrate 20, and a current to be measured flows through the pads 4a and 4b. The pads 2a 'and 2b' on the coil substrate 20 are connected to a circuit for supplying a high-frequency signal for excitation, and the pads 3a 'and 3b' are also connected to a measurement operation circuit. The square root of the average value (rms) is calculated.

According to the structure of the above-described embodiment, the signal line 4 exists only below the saturable magnetic ring core 1, and the structure shown in FIG. The wires 4 exist above and below the saturable magnetic ring core 1, and the number of signal lines for saturating the ring core 1 is substantially reduced to half. It has been confirmed by experiment that it works.

FIG. 4 is a graph showing the result of actually measuring the current flowing through the signal line 4 according to the embodiment of the present invention described above. At the time of this measurement, the number of turns of the signal line 4,
In other words, the number of signal lines 4 intersecting the saturable magnetic ring core 1 below the sensor chip C is set to 10, and the root-mean-square (rms) of the voltage across the receiving secondary coil 3 is set.
Took.

As is apparent from this graph, it has been confirmed that the embodiment of the present invention can provide the same sensitivity as that of a conventional sensor of this type.

In the above embodiment, the signal lines 4 are formed on a printed circuit board.
A ceramic substrate, a glass substrate, or a silicon substrate may be used.

In the above-described embodiment, the signal line 4 partially closes to the ring core 1 so that the signal line 4 partially saturates the saturable magnetic ring core 1. Although the pattern is shown as an example, the pattern of the signal line 4 may be made larger so that substantially the entire saturable magnetic ring core 1 is saturated.

Further, in the above embodiment, the ring core and the sensor chip C in which the primary and secondary coils are formed as a thin film on the substrate 10 are mounted on the coil substrate 20. A structure in which primary and secondary coils are wound may be mounted, and the technical scope of the present invention includes this structure.

[0029]

As described above, according to the present invention, a signal line through which a current to be detected flows is formed on a substrate surface, and a primary and a secondary coil are wound on the signal line. Since a structure with a ring core is adopted, the signal line is wound directly around the saturable magnetic ring core, or the signal line is wound around the sensor chip including the saturable magnetic ring core. In comparison, the step of winding the signal line is not required, so that a current sensor suitable for mass production and with less restrictions on mounting can be obtained.

Further, the saturable magnetic ring core and the exciting primary coil and the receiving secondary coil wound therearound are formed as thin films to form a sensor chip, and the sensor chip is mounted on a substrate having signal lines formed on its surface. Adopting the mounted structure eliminates the need for any wire winding process,
A current sensor that is more suitable for mass production and has less restrictions on mounting can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of an embodiment of the present invention showing a state in which an upper insulating layer 6 of a sensor chip C is seen through;

FIG. 2 is a schematic longitudinal sectional view of a main part of a sensor chip C according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a plane pattern (A) and a three-dimensional pattern (B) of an excitation primary coil 2 or a reception secondary coil 3 according to an embodiment of the present invention.

FIG. 4 is a graph showing an example of a current measurement result according to the embodiment of the present invention;

FIG. 5 is a schematic plan view showing a configuration of a conventional current sensor in which a saturable magnetic ring core, a primary coil for excitation, and a secondary coil for reception are formed of a thin film, and a signal line composed of a conductive wire is wound around the thin film. Figure

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Saturable magnetic ring core 2 Primary coil for excitation 3 Secondary coil for reception 4 Signal line 5 Lower insulating layer 6 Upper insulating layer 10 Substrate 20 Coil substrate C Sensor chip

Claims (2)

[Claims] An exciting primary coil through which a high-frequency signal flows, a receiving secondary coil, a saturable magnetic ring core around which these are wound, and a signal line through which a current to be measured flows are provided. A sensor for detecting a current to be measured by utilizing the fact that when a current flows through a wire, the saturable magnetic ring core is saturated and signal transmission from the primary coil for excitation to the secondary coil for reception is attenuated. 3. The current sensor according to claim 1, wherein the signal line is formed on a substrate surface, and a saturable magnetic ring core having the primary and secondary coils wound thereon is mounted thereon. 2. The current sensor according to claim 1, wherein the primary coil for excitation, the secondary coil for reception, and the ring core are formed by a thin film on a substrate different from the substrate. .