JP3798035B2 - Method and apparatus for measuring contact resistance of reed switch - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method and an apparatus for measuring a contact resistance of a reed switch (Read Switch) used in an electronic apparatus, in particular, a contact resistance measuring method of a reed switch capable of detecting a contact failure due to the presence of fine particles.
[0002]
[Prior art]
Conventionally, a reed switch in which a magnetic lead is enclosed in a glass tube so that the tip as a contact portion is parallel, and a driving coil is wound around the outer wall of the glass tube, The overlapping parts touch and switch on. Such a reed switch has a feature that the structure is simple, there are few failures, and high-speed operation is possible. In such a reed switch, since the state of a product can be grasped by measuring the contact resistance of a contact, it is implemented at a manufacturing site or the like.
[0003]
One known method for measuring the contact resistance of a reed switch is to apply a constant current (current x number of coil turns = ampere turn) to the operating coil and use a milliohm meter or voltage drop method. is there.
[0004]
FIG. 7 is a circuit diagram showing a measurement circuit for measuring contact resistance using a milliohm meter. An operating coil 72 is fitted on the reed switch 71. A milliohm meter 73 is connected to the reed switch 71, and a DC power source 74 is connected to the operating coil 72. In such a configuration, when a predetermined coil current i is applied to the operating coil 72, the contact of the reed switch 71 is closed. Therefore, the contact resistance is measured with the milliohm meter 73 in this state.
[0005]
FIG. 8 shows a circuit diagram when the contact resistance is measured by the voltage drop method. Since the structure of the reed switch is the same as that shown in FIG. A constant current power supply 81 is connected between the magnetic leads, and a voltmeter 82 is also connected between the magnetic leads. A specified measurement current I (10 mA) is energized to the reed switch 71 by the constant current power supply 81, and the voltage difference generated between the magnetic leads at this time is measured by a voltmeter 82 (for example, a digital voltmeter).
[0006]
FIG. 9 is a timing chart showing the measurement timing in the conventional contact resistance measurement method. When energization of the operating coil 72 is started, the reed switch (R.SW) 71 is switched on simultaneously with the energization. On the other hand, when the operation coil 72 is de-energized, it is switched off. The period from switch-on to switch-off is the contact resistance measurement time range.
[0007]
[Problems to be solved by the invention]
However, in the above-described conventional technology, a contact pressure sufficient to maintain the contact operation state of the reed switch is applied to the contact portion at the time of measurement. For this reason, as shown in FIG. 10, even when the fine particles 104 exist around the contact portion 103 in which the surface contact state between the contacts 101 and 102 is stable, the contacts between the contacts of the contact portion 103 are in contact with each other. Therefore, the contact resistance value including the fine particles 104 could not be measured and detected.
[0008]
Further, in a reed switch in which fine particles are generated during use, as shown in FIG. 11, the fine particles 104 are interposed in the contacts and become point contacts, so that contact failure is increased due to an increase in contact resistance (several ohms). Since the probability of generation is extremely high, it must be detected in the initial stage before the device is installed. In addition, there is a problem in that, when fine particles with extremely high adhesion such as gold (Au) are formed during use and are interposed between the contacts as described above, the contacts adhere (soft-stick).
[0009]
FIG. 12 shows a contact opening model. In the stable operation state of the contact as shown in FIG. (A), the fine particles 104 exist around the stable contact portion 103, but the contact resistance is stabilized by a sufficient contact pressure by the stable contact portion 103. . Further, the contact resistance immediately before the contact is opened is that the fine particles 104 exist around the stable contact portion 103 as shown in FIG. When the fine particles 104 are present on the contact surface of the stable contact portion 103, the contact resistance of the stable contact portion 103 becomes a very large value. However, when conductive fine particles (Au) are present, the contact resistance is extremely small, indicating that the contact resistance is in a normal state. In addition, (c) figure has shown the state (separation | separation state) which the two contact points left | separated.
[0010]
FIG. 13 is an explanatory view showing a contact adhesion and sticking model.
In the figure, (a) shows a stable operation state, and the highly adherent fine particles 104 are present around the stable contact portion 103. Further, FIG. 5B shows a state where the fine particles are present, immediately after the fine particles 104 are interposed in the stable contact portion 103. Further, FIG. 6C shows an adhesion state, and the contact portion is adhered with fine particles (for example, Au) having high adhesiveness, so that the contact cannot be separated (contact separation).
[0011]
As described above, conventionally, when particles exist in the contact portion of the reed switch, contact failure (increased contact resistance, adhesion, sticking, etc.) may occur during operation. There is a problem that it cannot be detected in the initial state.
[0012]
Therefore, an object of the present invention is to provide a method and an apparatus for measuring the contact resistance of a reed switch that can detect in the initial state fine particles that exist between contacts and that may cause contact failure during operation.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the method for measuring the contact resistance of a reed switch according to the present invention has a structure in which a magnetic lead is sealed in a sealing glass and an operating coil is externally fitted to the sealing glass. In the reed switch for energizing the operating coil to perform a switch operation, a magnetostriction is generated in the magnetic material lead by energizing the operating coil, and the first current value indicating that the reed switch is switched on, A waveform having a second current value higher than the current value of 1 and the magnetic lead having a sufficient contact pressure is set as a basic waveform, and the basic waveform is applied to the operating coil so that the reed switch is always in an ON state. The contact resistance is measured in the process of repeatedly energizing .
[0014]
In this case, after the basic waveform is repeatedly supplied to the operating coil, the current supplied to the operating coil is gradually decreased from the level of the first current value, and a disconnection failure is detected in the process. it can. Furthermore, before the basic waveform is repeatedly applied to the operating coil, the current supplied to the operating coil is gradually increased, and the moving value can be measured when the first current value is reached.
[0015]
The contact resistance measuring device for a reed switch according to the present invention includes a coil driving means for energizing an operating coil of the reed switch at the time of measurement, and a contact current supply for energizing the magnetic lead of the reed switch at the time of measurement. And a contact resistance measuring means for detecting a voltage or resistance value between the magnetic leads when energized by the contact current supplying means , and the coil driving means is configured to detect the magnetic lead by energization by the coil driving means. And a waveform having a first current value indicating that the reed switch is switched on and a second current value that is higher than the first current value and that allows the magnetic lead to obtain a sufficient contact pressure. As a basic waveform, the basic waveform is repeatedly energized to the operating coil so that the reed switch is always in an ON state.
[0016]
In addition, the coil driving means gradually lowers the current supplied to the operating coil from the first current value until the reed switch is switched off or less after the basic waveform is repeatedly supplied to the operating coil. Is.
[0017]
Further, the contact resistance measuring means performs contact resistance measurement and particle detection in the process of repeatedly energizing the operating coil with the basic waveform, and the separation failure in the process of gradually decreasing the current energizing the operating coil. Is to measure.
[0018]
Further, the coil driving means gradually increases the current value until the reed switch is turned on after the first process of energizing the stable operating current value with the rectangular wave, and after this first process, and then the stable operation is performed at once. A second step of gradually reducing the current until the switch is turned off after energizing to the current value, a third step of repeatedly energizing the operating coil to the operating coil, and the switch of the reed switch following the third step. It has each of the 4th processes of decreasing a current value gradually to off.
[0019]
Further, the contact resistance measuring means measures a touch value when the switch is turned on in the second process, measures a contact resistance after energizing to the stable operating current value, and measures a contact resistance in the third process. And a function of performing fine particle detection and measuring a separation failure in the fourth process.
[0021]
[Action]
According to the above-described means, if the first current value causes a magnetostrictive effect, the magnetic lead is stretched, and if fine particles are present in the contact portion, a force for moving the fine particles is formed, thereby causing non-conduction. Fine particles and adhesive fine particles can be removed. Further, the second current value larger than the first current value applies a sufficient contact pressure to the contact portion of the magnetic lead. Accordingly, it is possible to detect contact failure such as detection of fine particles and adhesion as well as measurement of contact resistance.
[0022]
If the contact portion is sticky, the contact will remain closed even after the power to the coil is cut off, resulting in poor separation of the contact portion. The detection of this separation failure is difficult to find if the rise / fall of energization to the coil is suddenly performed. Therefore, after energizing the coil intermittently, the current is gradually decreased, and the disconnection failure is measured from the electrical behavior of the contact portion when the switch is turned off. In this way, it is possible to reliably detect a disconnection failure.
[0023]
On the other hand, if the applied current is gradually increased, the current value at the time when the reed switch is turned on becomes a moving value. Thus, the moving value of the reed switch can be easily measured by the control for increasing the applied current and the grasp of the switch-on timing.
[0024]
Further, according to the contact resistance measuring device for a reed switch described above, an applied current to the coil having an arbitrary rising waveform and falling waveform can be formed by the coil driving means, and the magnetic material is supplied from the contact current supplying means when the coil is driven by this. A stable operating current is supplied to the leads, and the voltage or resistance value between the magnetic leads is detected by the contact resistance measuring means when the current is supplied, and measurement data is obtained. As a result, it is possible to detect contact failure such as detection of fine particles and adhesion as well as measurement of contact resistance.
[0025]
Then, the two types of current values generated by the coil driving means function as follows. That is, when the first current value is switched on and the magnetoresistive effect exerted on the magnetic material lead causes the magnetic material lead to be stretched, and if fine particles are present at the contact portion, a force for moving the fine particles is formed. The non-conducting fine particles and the adhesive fine particles can be removed. Furthermore, a sufficient contact pressure is applied to the contact portion of the magnetic lead by the second current value. Accordingly, it is possible to detect contact failure such as detection of fine particles and adhesion as well as measurement of contact resistance.
[0026]
Further, in the coil driving means, if the first current value and the second current value are energized repeatedly and the contact resistance is measured after the energization is completed, the contact resistance can be reliably measured with a simple configuration. It can be performed. Further, if the current is gradually decreased from the first current value until the reed switch becomes less than or equal to the switch-off, and the contact resistance measuring means is made to function in the process, the disconnection failure can be measured. .
[0027]
When the coil is driven by the coil driving means, a plurality of energization patterns, that is, (1) a process of energizing a stable operating current value with a rectangular wave, (2) after this energization, gradually the current value until the reed switch is turned on And then gradually reducing the current until the switch is turned off, (3) repeatedly applying the basic waveform to the operating coil, and (4) following the energization, the lead By continuously executing the four steps of gradually decreasing the current value until the switch is turned off, it is possible to continuously measure different contents in each step.
[0028]
Specifically, the moving value can be measured in the process (2) , the contact resistance can be measured in the process (3) , and the separation failure can be measured in the process (4) .
[0029]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a circuit diagram showing an embodiment of a contact resistance measuring apparatus for a reed switch according to the present invention.
[0030]
The contact resistance measuring device includes a coil driving circuit 1 (coil driving means) for energizing and driving the operating coil, and a contact current supply circuit 2 (contact current) for controlling the current necessary for resistance measurement between the pair of magnetic substance leads. Supply means), a contact resistance measuring circuit 3 (contact resistance measuring means) for taking in a voltage between a pair of magnetic leads of the reed switch and sending data to an MPU (micro processor unit) 4, and an MPU 4 ing.
[0031]
The MPU 4 is connected to each circuit via a bus 4a (control bus and data bus), and controls the coil drive circuit 1, the contact current supply circuit 2, and the contact resistance measurement circuit 3 in an integrated manner. Although not shown here, the MPU 4 comes with a ROM containing a program for executing processing such as contact resistance measurement, a memory such as a RAM for storing measurement data, and an interface circuit. ing.
[0032]
The coil drive circuit 1 is connected to an operating coil 6 that is externally fitted to the reed switch 5 in a wound state and applies a magnetic field to the magnetic lead. A contact current supply circuit 2 and a contact resistance measurement circuit 3 are connected to a pair of magnetic leads of the reed switch 5. The coil drive circuit 1 includes a D / A converter 7 connected to the MPU 4 and a driver 8 connected to the D / A converter 7. The contact current supply circuit 2 includes a D / A converter 9 connected to the MPU 4 and a constant current driver 10 connected to the D / A converter 9.
[0033]
Further, the contact resistance measurement circuit 3 includes an A / D converter 11 connected to the MPU 4, a flip-flop circuit (F / F) 12 connected to the MPU 4, an amplifier 13 connected to the output terminal of the A / D converter 11, Each of the resistors 14 and 15 for adjusting the gain of the amplifier 13 and a switch 16 for switching these resistors are provided. By switching the switch 16, the gain of the amplifier 13 can be selected to be 1 time (× 1) or 100 times (× 100), so that the contact resistance value can be measured accurately.
[0034]
FIG. 2 is a timing chart for explaining the operating conditions of the basic operating waveform when measuring the contact resistance measuring method and apparatus according to the present invention.
[0035]
In the figure, (a) shows the current waveform of the operating coil 6, and from 0 [AT] (current x number of coil turns = ampere turn) to the reed switch 5 (shown as R.SW in FIG. 2) as shown in (b). The AT value is increased to a level at which the output of is turned on. Pi [AT] in the process (this is referred to as a moving value: Pull In) is the time when the reed switch 5 is turned on. Further, a level at which the contact can be sufficiently contacted (a level at which 100 [AT] is energized to the operating coil 6) is set as AT2. Further, the time when the output of the reed switch 5 is turned off by performing an operation of gradually decreasing the current from the AT2 level is defined as Do [AT] (this is referred to as an open value: Drop Out). These are the basic characteristics of the reed switch 5.
[0036]
Note that AT1 is the time when ΔDo [AT] is added so that the output of the reed switch 5 does not open to the Do value. When this is converted to the peak-to-peak (PP) waveform of the basic coil waveforms AT1 and AT2 of (c), the reed switch 5 is always in the ON state. Summarizing the conditions at this time, the operating conditions of the basic operating waveform are the following two.
(1) AT1: AT value at which the reed switch 5 is not opened (turned off).
(2) AT2: AT value at which sufficient magnetostriction can be obtained (usually using a magnetic saturation ampere turn).
[0037]
FIG. 3 is an explanatory diagram showing the magnetostrictive effect. FIG. 4 is a timing chart showing the operation of each part of the contact resistance measuring device at the time of detecting a fine particle, and FIG. 5 is a timing chart showing the operation of each part at the time of detecting a separation failure.
[0038]
FIGS. 3A to 3D show the operation states of the contacts when the basic coil waveforms AT1 and AT2 of FIG. 4 are input. FIG. 3 (e) corresponds to ΔDo = 0AT in FIG. 5 (a), and is a state in which a separation failure occurs due to the presence of adhesive fine particles (Au).
[0039]
Further, each case will be described. FIG. 3 (a) shows a state where the contacts are separated, FIG. 3 (b) shows a state of the basic coil waveform AT1, and the contact is Δl (due to the magnetostriction effect). It shows a state of being shifted by about 1 μm). FIG. 3C shows the state of AT2, the magnetostriction effect is reduced, and the fine particles have moved into the contact. In this state, the contact resistance is high because fine particles are present in the contact and the contact pressure is low, and a defect can be detected depending on the value of the contact resistance. FIG. 3D shows the same operation as in the state of FIG. 3B even though fine particles are present at the contacts. As a result, the contact contact pressure increases and the contact resistance value shows a normal value. However, in some cases, it may be possible to detect a defect in the state (d), but there is no problem in detection.
[0040]
As described above, the basic waveforms AT1 and AT2 are repeated in the (b) and (c) states (indicating the magnetostriction effect). The state (e) shows a state in which adhesion is caused by the repeated opening and closing of the states (b) and (c) and the presence of the adhesive fine particles (Au) in addition to the magnetostrictive effect.
[0041]
In actual measurement, an operating current (for example, 100 AT) flowing through the operating coil 6 is applied from the coil driving circuit 1. The state at this time is the rising peak AT2 of the basic coil waveform shown in FIG. 4, the value reaches a high level together with the magnetostrictive contact pressure, and the contact resistance value is stabilized at a low level. At the next rising peak AT1, both the magnetostrictive contact pressure and the contact contact pressure are at a low level, and the contact resistance value is ΔRC for a normal product. The measurement timing is the peak of each of AT1 and AT2, and data is read from the A / D converter 11 at this timing. In this reading, a measurement current (for example, 10 mA) is supplied to the reed switch 5, the gain of the amplifier 13 is set to × 100, and contact resistance data is read from the A / D converter 11 by the MPU 4. If the resolution at this time is 1 mΩ and the 12-bit A / D converter 11 is used, it is possible to measure up to 4096 mΩ.
[0042]
The failure (NG) determination is a peak waveform exceeding the NG level as shown in the “error” waveform of the contact resistance value in FIG. 4, and this makes it possible to determine the failure of the measured result. The waveform cycle (time) of the operation waveform of the particle detection can be arbitrarily changed. In addition, as long as the operating condition is a basic operation waveform, the waveform can be arbitrarily changed as shown in FIG.
[0043]
FIG. 5 shows an operation timing for detecting a separation failure in the present invention. The basic coil waveforms AT1 and AT2 are in the same operation state as the particle detection operation waveforms AT1 and AT2 (operation conditions of the basic operation waveform), and the waveform cycle (time) can be arbitrarily changed. The actual separation failure detection waveform is the cycle in which the AT level gradually drops from the waveform AT1 after the repeated operation of AT1 and AT2, and the level at which the output waveform of the reed switch (R.SW) is turned off is one cycle of the Do value. And Assuming that the changed Do after 2 cycles is ΔDo, (i) No normal fluctuation: Do = ΔDo, (ii) Sticking: Do> ΔDo, (iii) Adhesion: 0 = ΔDo, and detection of separation failure is possible become.
[0044]
FIG. 6 is a timing chart showing basic characteristics of the reed switch and operation waveforms for simultaneous detection of defects.
[0045]
When a stable operating current (for example, 100 AT) is applied to the operating coil 6 from the coil drive circuit 1, a stable contact contact state is formed on the reed switch 5. The state at this time is 60 in FIG. 6, which is a basic characteristic of the reed switch 5. Next, in order to measure the moving value Pi [AT], which is a basic characteristic of the reed switch, the operating current is gradually supplied to the operating coil 6 and the time when the output of the reed switch is turned on is defined as Pi [AT]. Pi [AT] at this time is measured.
[0046]
Next, the contact resistance CR is measured when a stable operating current (for example, 100 AT) is supplied to the operating coil 6. Next, the stable operating current is gradually decreased, and the time when the output of the reed switch is turned off is defined as Do [AT]. At this time, Do [AT] is measured by the contact resistance measuring circuit 3. The particle detection and separation detection waveforms performed after this are the same as described above, and a description thereof will be omitted.
[0047]
【The invention's effect】
As described above, the method of measuring the contact resistance of a reed switch according to the present invention has a structure in which a magnetic lead is sealed in a sealing glass and an operating coil is externally fitted to the sealing glass. In a reed switch in which a coil is energized to perform a switch operation, a first current value indicating that magnetostriction occurs in the magnetic material lead due to energization of the energizing coil and the reed switch is switched on, and the first current The basic waveform is a waveform having a second current value that is higher than the value and the magnetic lead obtains a sufficient contact pressure, and the basic waveform is repeatedly energized to the operating coil so that the reed switch is always on. Since the contact resistance is measured in the process, it is possible to detect the contact failure such as the detection of fine particles and adhesion as well as the measurement of the contact resistance.
[0048]
The contact resistance measuring device according to the present invention includes a coil driving means for energizing the operating coil of the reed switch at the time of measurement, a contact current supplying means for energizing the magnetic lead of the reed switch at the time of measurement, The contact resistance measuring means for detecting the voltage or resistance value between the magnetic lead when energized by the contact current supply means can similarly detect the contact resistance such as the detection of fine particles and the contact failure such as adhesion. It becomes possible.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing an embodiment of a contact resistance measuring device for a reed switch according to the present invention.
FIG. 2 is a timing chart showing operating conditions of basic operation waveforms at the time of measurement by the contact resistance measuring device according to the present invention.
FIG. 3 is an explanatory diagram showing a magnetostriction effect according to the present invention.
FIG. 4 is a timing chart showing the operation of each part of the contact resistance measuring device when fine particles are detected.
FIG. 5 is a timing chart showing the operation of each part when a separation failure is detected.
FIG. 6 is a timing chart showing basic characteristics of the reed switch and operation waveforms for simultaneous detection of defects.
FIG. 7 is a circuit diagram showing a measurement circuit using a milliohm meter.
FIG. 8 is a circuit diagram showing a circuit when contact resistance is measured by a voltage drop method.
FIG. 9 is a timing chart showing measurement timings in a conventional contact resistance measurement method.
FIG. 10 is an explanatory diagram showing an example in which fine particles exist outside a contact.
FIG. 11 is an explanatory diagram showing an example in which fine particles are present in a contact.
FIG. 12 is an explanatory diagram showing a contact breaking model.
FIG. 13 is an explanatory view showing a contact adhesion and sticking model.
[Explanation of symbols]
1 Coil Drive Circuit 2 Contact Current Supply Circuit 3 Contact Resistance Measurement Circuit 5 Reed Switch 6 Operating Coil

Claims (8)

In a reed switch that has a structure in which a magnetic lead is sealed in a sealing glass and an operating coil is externally fitted to the sealing glass, and the operating coil is energized to perform a switch operation.
Energization of the operating coil causes magnetostriction in the magnetic lead and the reed switch indicates that the switch is turned on, and the magnetic lead has a sufficient contact pressure higher than the first current value. A reed switch having a waveform having a second current value as a basic waveform and measuring contact resistance in a process of repeatedly energizing the operating coil with the basic waveform so that the reed switch is always in an on state. Contact resistance measurement method. After the basic waveform is repeatedly applied to the operating coil, the current supplied to the operating coil is gradually decreased from the level of the first current value, and a disconnection failure is detected in the process. The contact resistance measuring method of the reed switch according to claim 1. The current value applied to the operating coil is gradually increased before the basic waveform is repeatedly applied to the operating coil, and the moving value is measured when the first current value is reached. The contact resistance measuring method of the reed switch according to 1. A reed switch contact resistance measuring device for use in the reed switch contact resistance measuring method according to claim 1,
Coil driving means for energizing the reed switch operating coil during measurement, contact current supplying means for energizing the magnetic lead of the reed switch during measurement, and the magnetic lead when energized by the contact current supplying means Contact resistance measuring means for detecting the voltage or resistance value between ,
The coil driving means includes a first current value in which magnetostriction is generated in the magnetic lead by energization by the coil driving means and the reed switch is switched on, and the magnetic lead is higher than the first current value. A reed switch characterized in that, with a waveform having a second current value for obtaining a sufficient contact pressure as a basic waveform, the basic waveform is repeatedly energized to the operating coil so that the reed switch is always on . Contact resistance measuring device. The coil driving means gradually lowers the current supplied to the operating coil from the first current value until the reed switch is switched off or less after the basic waveform is repeatedly supplied to the operating coil. The contact resistance measuring device for a reed switch according to claim 4 . The contact resistance measuring means performs contact resistance measurement and particle detection in the process of repeatedly energizing the operating coil with the basic waveform, and measures a disconnection failure in the process of gradually decreasing the current energizing the operating coil. The contact resistance measuring apparatus for a reed switch according to claim 5 . The coil driving means has a first process of energizing the stable operating current value with a rectangular wave, and after this first process, the current value is gradually increased until the reed switch is turned on, and then the stable operating current value is A second step of gradually decreasing the current until the switch is turned off, a third step of repeatedly applying the basic waveform to the operating coil, and the third step until the reed switch is turned off. 5. The reed switch contact resistance measuring device according to claim 4, further comprising: a fourth step of gradually decreasing the current value. The contact resistance measuring means measures a touch value at the time when the switch is turned on in the second process and measures the contact resistance after energizing to the stable operating current value. In the third process, the contact resistance measurement and fine particles are measured. 8. The reed switch contact resistance measuring device according to claim 7 , further comprising a function of detecting and further measuring a disconnection failure in the fourth step.

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