JPH0720170A - Contact resistance measuring instrument - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide a contact resistance measuring instrument capable of improving load control resolution and resistance measurement accuracy. According to the present invention, in a contact resistance measuring device for measuring a contact resistance by applying a minute load between two electrodes 21 and 22, a flat electrode 21 and a pin electrode 22 to be measured,
Two conductive leaf springs A1 and B fixed to the flat electrode 21
1, a fine movement table 23 that moves the plane electrode 21 via the springs A1 and B1, electric wires A2 and B2 respectively connected to the springs A1 and B1, and a load meter 24 that measures the load applied to the pin electrode 22. And the electric wire A connected to the pin electrode 22.
3, B3, a power supply 25 for supplying a known current between the electric wires B2, B3, and a voltmeter 27 for measuring the voltage between the electric wires A2, A3.
It consists of and.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact resistance measuring device for accurately measuring contact resistance in contact parts such as relays and connectors.

[0002]

2. Description of the Related Art Conventionally, in designing contact parts such as relays and connectors, it is necessary to accurately grasp the relationship between contact force and resistance of contacts. The conventional contact resistance measuring device has a structure as shown in FIG. That is, one electrode to be measured (planar electrode) 1 is placed on the fine movement stage 3 via the support base 2, and the other electrode to be measured (pin electrode) 4 is the weighing pan 501 and the electronic balance main body 502.
It is fixed to the load cell 5. Electric wires E and F are connected to the electrodes 1 and 4, respectively, and the other ends of the electric wires E and F are connected to a power source 6, a voltmeter 7, and an ammeter 8. Microtremor 3
The electrodes 1 and 4 were sewn together by using the load meter 5, the contact force was measured by the load meter 5, and the resistance value was measured by the voltmeter 7 and the ammeter 8. Further, the support base 2 is made rigid so that the flat electrode 1 is not twisted by the electric wire E. Reference numerals 9 and 10 are solder joints, and 11 is a movable direction of the fine movement table 3.

[0003]

The conventional contact resistance measuring device has the following problems. First, the load suppression resolution was low. That is, in order to improve the measurement accuracy of the load, an electronic balance is usually used for the load meter 5, but the electronic balance main body 502 supports the weighing pan 501 by electromagnetic force so that the height is constant regardless of the load. The magnetic field generation current is adjusted to determine the load from this current value. Therefore, the weighing pan 501 has theoretically infinite rigidity, and even if the plane electrode 1 is moved by a small amount by the fine movement table 3, the load changes greatly. For this reason,
Although the load measurement accuracy was high, the control resolution was low, and the desired load value could not be applied accurately.

Secondly, the resistance measurement resolution is low and the operation is complicated. That is, in the conventional configuration, the measured resistance is the total value of the contact portions of the electrodes 1 and 4, the electric wires E and F, and the solder connection portions 9 and 10. In order to improve the load measurement accuracy, the electric wire F connected to the pin electrode 4 needs to have low rigidity. Therefore, the diameter is small and the resistance value is about 1Ω. Therefore, it is necessary to measure the resistance of the electric wire F in advance and subtract it. Furthermore, the wires E, F and the electrodes 1,
Since the resistance of the solder connection parts 9 and 10 of 4 cannot be measured,
The resistance value at this portion was an error.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a contact resistance measuring device capable of improving load control resolution and resistance measurement accuracy.

[0006]

In order to achieve the above object, a contact resistance measuring device of the present invention is a contact resistance measuring device for measuring contact resistance by applying a minute load between a plurality of electrodes. First and second electrodes of interest, a conductive spring fixed to the first electrode, a means for moving the first electrode through the spring, and a first connected to the spring, respectively. , A second electric wire, a means for measuring a load applied to the second electrode, third and fourth electric wires connected to the second electrode,
It is characterized in that it comprises a means for supplying a known current between the first and third electric wires and a means for measuring the voltage between the second and fourth electric wires.

[0007]

With the above-described means, the contact resistance measuring device according to the present invention firstly fixes one electrode to the fine movement table via a spring. As a result, the apparent rigidity of the load cell decreases,
The control resolution of load is improved. Secondly, a plurality of electric wires are fixed to the other electrode, and the resistance is measured by the 4-terminal method using these springs and electric wires. As a result, with a simple configuration, it is possible to eliminate the influence of the electric wire and the connecting portion and measure the resistance of only the contact portion.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. The contact point is composed of a flat electrode 21 and a pin electrode 22 having a sharp tip. The planar electrode 21 has two conductive leaf springs A1 and B1.
(B1 is hidden behind A1 and is not shown in the figure), and is fixed to the fine movement table 23. The pin electrode 22 is fixed to the weighing pan 241 of the load meter 24. The load meter 24 is composed of a weighing pan 241 and an electronic balance main body 242. Electric wires A2 and B2 are connected to the leaf springs A1 and B1, and electric wires A3 and B3 are connected to the pin electrode 22. Electric wire B2
B3 is connected to the power supply 25 and the ammeter 26, and the electric wires A2 and A
3 is connected to the voltmeter 27. Reference numerals 28 and 29 denote solder connection portions, and 30 denotes a movable direction of the fine movement table 23.

FIG. 2 is a detailed view of the vicinity of the contact points of the electrodes 21 and 22. The leaf springs A1 and B1 are fixed to the flat electrode 21 with a conductive adhesive such as a conductive paste so as to sandwich a contact point on the flat electrode 21 therebetween. Leaf spring A
Wires A2 and B on the mounting part to the fine motion table 23 on B1 and B1
2 is soldered. On the side surface of the pin electrode 22,
The electric wires A3 and B3 are soldered to the opposite positions on the circumference.

Next, the operation principle of the present invention will be described with reference to FIG.
In the above, the fine movement table 23 is moved up and down in the direction of arrow 30, the flat electrode 21 is pressed against the pin electrode 22, and the contact force is measured by the electronic balance main body 242. The electronic balance main body 242 has infinite rigidity, but since the leaf springs A1 and B1 are bent, the apparent rigidity is lowered, and the electronic balance main body 242 can be pressed with an arbitrary load. That is, if the total rigidity of the leaf springs A1 and B1 is set to (required load control resolution) ÷ (movement resolution of the fine movement table) or less, the pressing force can be controlled with a desired load resolution.

The contact resistance is measured by the 4-terminal method.
FIG. 3 shows a principle diagram of the 4-terminal method. The measurement resistance R is given as the quotient of the measured values of the voltmeter 27 and the ammeter 26. In general, the measurement circuit has parasitic resistances r1 and r2, which mainly occur at the connection points N1, N2, N3 and N4. As shown in FIG. 3, the connection point N1, between the ammeter 26 and the power supply 25,
If the connection points N2 and N3 of the voltmeter 27 are arranged inside N4, the influence of the parasitic resistance r1 can be eliminated. Further, if the internal resistance of the voltmeter 27 is sufficiently large, the parasitic resistance r2
Since almost no current flows through, this effect can be eliminated.

FIG. 4 shows a virtual current path in this embodiment. In the figure, for the sake of explanation, only the vicinity of the contact is schematically shown. The broken line shows the circuit configuration (current path) of the 4-terminal method. Connection points N2, N of the voltmeter 27 in FIG.
3 corresponds to the current branch points M2 and M1 in FIG.
The influences of the solder connection portions 28, 29 and the conductive pace used for connecting the flat electrode 21 and the leaf springs A1, B1 can be almost completely eliminated. Further, these current branch points M1 and M2
Since is close to the contact point, the influence of the resistance in the electrode is small. As a result, only the contact resistance can be accurately measured.

FIG. 5 shows an example of the contact resistance / load relationship measured by the contact resistance measuring instrument of this embodiment. A load control resolution of 5 μN and a resistance measurement resolution of 1 mΩ were obtained, and the contact resistance in the minute load area can be measured accurately.

Although the load measurement resolution of this embodiment is the same as the conventional one, the load control resolution is not comparable.
With the conventional balance, the load could not be controlled and the measurement could not be performed on the object having a large rigidity as the object to be measured.

By attaching the spring, the measurement can be performed regardless of the rigidity of the object to be measured, and the control resolution can be controlled by changing the spring constant. In addition, the load control resolution can be improved from the current 5 μN.

The performance of the resistance measuring device itself (ammeter, voltmeter) has conventionally been capable of measuring about μΩ (the measurement accuracy of FIG. 5 is mΩ, the accuracy of the measuring device is simply mΩ).
Because it was. ). However, if the object to be measured is a contact material, the measurement terminal is attached to the contact material, so
Most of the error exists in the portion where the measuring terminal is attached to the contact, and the error is several 100 mΩ in the conventional method, and the measurement resolution is several 100 mΩ due to this error.

In FIG. 2, the leaf springs A1 and B1 are electrodes 21 and 2.
Although it is arranged so as to sandwich the contact point of No. 2, even if the leaf springs A1 and B1 are arranged on the same side of the contact point of the plane electrode 21 and the pin electrode 22 as shown in FIG.
Also, the influence of the internal resistance of the wires A2, A3, B2, B3 can be eliminated. In this case, since the branch point of the current is separated from the contact point, the resistance in the plane electrode 21 causes an error. However, the resistance thereof is lower than that of the connection portion between the leaf springs A1 and B1 and the flat electrode 21 and the solder connection portions 28 and 29, and the error is significantly smaller than that of the conventional configuration. The same applies to the connection between the electric wires A3 and B3 and the pin electrode 22.

In FIG. 7, the leaf springs A1 and B1 are connected to the plane electrode 2
It is attached to the opposite side of the first pin electrode 22. At this time, if the two leaf springs A1 and B1 are arranged so as to sandwich the pin electrode 22 and the planar electrode 21 is made of a uniform material,
Measurement accuracy similar to that of the first embodiment can be obtained. The measurement accuracy of the resistance value is not affected by the resistance value of the conductive paste used for connecting the leaf springs A1 and B1 and the flat electrode 21 at all. This is because, like the first embodiment, the connection portion made of the conductive paste is arranged outside the current branch point in FIG.

However, as shown in FIG. 8, the contact material 212 is plated or sputtered on the surface of the base material 211 to form the planar electrode 2.
1 is made, the branch point M2 in FIG. 4 may be the contact material 2 depending on the difference in resistance value between the base material 211 and the contact material 212.
Since it exists inside the base material 211 instead of inside 12, the error increases as the distance between the branch points M1 and M2 becomes longer.
Reference numeral 31 is a conductive paste.

As still another embodiment, it is possible to use a coil spring or a parallel leaf spring as the conductive spring. Leaf springs are simple, but the contact surface tilts slightly when a load is applied. With a coil spring or a parallel leaf spring, even if the spring deforms, the contact surface does not tilt, and more accurate measurement is possible.

As a simpler configuration than this embodiment, for example,
It is possible to use one leaf spring. In this case, however, the current branch point is inside the leaf spring, and the resistance inside the leaf spring / flat electrode portion and the inside of the leaf spring are mixed in as an error, and the measurement accuracy is significantly reduced. It is also conceivable to directly fix the electric wires A and B to the flat electrode without intervening the leaf spring. However, in this case, due to the rigidity and weight of the wires A and B, a force such as a twist is applied to the plane electrode, and the load measurement accuracy is significantly reduced.

[0023]

As described above, the contact resistance measuring device according to the present invention can remarkably enhance the accuracy of load control and resistance measurement with a simple structure. As a result, it is possible to contribute to high reliability and improvement in design accuracy of contact parts such as relays and connectors.

[Brief description of drawings]

FIG. 1 is a configuration explanatory view showing a first embodiment of the present invention.

FIG. 2 is a side view showing the vicinity of the contact in the embodiment of FIG.
It is a top view and a front view.

FIG. 3 is a circuit diagram showing the principle of contact resistance measurement by the 4-terminal method.

FIG. 4 is an explanatory diagram showing current paths in the embodiment of FIG.

5 is a characteristic diagram showing an example of resistance / load characteristics of a contact measured by the embodiment of FIG.

6A and 6B are a side view and a plan view showing a second embodiment of the present invention.

FIG. 7 is a side view, a plan view, and a third embodiment of the present invention.
It is a front view.

8 is a structural explanatory view showing the vicinity of a contact in the embodiment of FIG.

FIG. 9 is a structural explanatory view showing a conventional contact resistance measuring device.

[Explanation of symbols]

21 ... Planar electrode, 22 ... Pin electrode, 23 ... Fine movement stage, 24
… Load cell, 25… Power supply, 26… Ammeter, 27… Voltmeter,
28, 29 ... Solder connection part, 30 ... Movable direction, 241 ...
Weighing pan, 242 ... Electronic balance main body, A1, B1 ... Conductive leaf spring, A2, A3, B2, B3 ... Electric wire.

Claims (1)

[Claims] 1. A contact resistance measuring device for measuring a contact resistance by applying a minute load between a plurality of electrodes, wherein the contact resistance is fixed to the first and second electrodes to be measured and the first electrode. A conductive spring, means for moving the first electrode through the spring, first and second electric wires respectively connected to the spring, and means for measuring a load applied to the second electrode, From the third and fourth electric wires connected to the second electrode, means for passing a known current between the first and third electric wires, and means for measuring the voltage between the second and fourth electric wires A contact resistance measuring device characterized by being configured.