JPS6358269A - Method and device for electrically measuring electromechanical relay armature excess movement - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for testing electromechanical relays, and more particularly to an apparatus and method for measuring electromechanical relay armature overtravel.

A typical electromechanical relay includes a coil that, when energized, acts as a solenoid to move an armature. As the armature moves, it contacts one or more moving contacts of the relay. This moving contact moves with the armature until it contacts the relay stationary contact.

-g, the relay is configured such that the armature continues to move past the point where the stationary and moving contacts make contact, and eventually the armature stops when it hits a mechanical stop. The distance that the armature travels beyond the point where the stationary and moving contacts touch is known as armature overtravel. Armature excess travel determines contact mating force and can significantly affect relay performance. For example, insufficient overtravel can cause unstable contact resistance, excessive contact bounce, and premature contact failure.

Generally, relay armature overtravel is adjusted to the desired amount during construction of the relay by adjusting the positions of the contacts and armature stops. And calibrated shims are often employed by skilled workers to measure and adjust for excess travel during relay construction.

Once relay configuration is complete, subsequent processing, testing and handling may result in misadjustment or loss of proper over-travel, which can easily go undetected. Mechanical measurements of overtravel require special tools and trained personnel and are therefore not useful for field testing. In the case of sealed relays, there is no way to physically check for excess travel once the relay is sealed.

Accordingly, it is an object of the present invention to provide a new and improved method of measuring electromechanical relay armature overtravel.

Another object of the present invention is to provide a method for electrically measuring electromechanical relay armature overtravel that does not require mechanical measurements or access to the interior of the relay.

These and other objects of the present invention are achieved by a method of measuring armature overtravel distance from a point where a designated moving contact touches a corresponding stationary contact to a mechanical stop during energization of a relay coil.

The method includes electrically monitoring the moving and stationary contacts when the stationary and moving contacts touch.

The relay coil current waveform as a function of time is also monitored.

When the relay coil is energized, a first point in time is established when both contacts touch each other. When the armature hits the stopper, a recurve occurs in the coil current waveform. Said first
The duration of time from the point in time until the occurrence of current recursion is measured.

Its measured time duration is proportional to armature overtravel.

Other objects, features and advantages of the invention will become apparent from a consideration of the specification in conjunction with the drawings.

In FIG. 1, a schematic diagram of a typical electromechanical relay 10 of the type to which the present invention is directed is shown. relay 1
0 includes a coil 12 and an armature 14. The armature 14 can rotate around a shaft 16 and is biased by a spring 18 to a de-energized position W 14 a. A set of stationary contacts is provided, including a normally closed contact 20 and a normally open contact 22.

A resiliently moving contact 24 pivots between contacts 20 and 22 about an axis 26 and is in physical and electrical contact with the normally closed contact 20 (e.g., by a spring or its own resiliency) in a de-energized position 24a. is energized by

Relay 10 is energized by applying a voltage across coil 12 at conductor 28,30. When energized, coil 12 acts as a solenoid and armature 14
generates a magnetic force that rotates the moving contact 24 toward the moving contact 24. Insulation 32 is provided on the armature 14 to isolate it from the contacts 24.

As armature 14 rotates, it engages contact 24, which moves with the armature until it touches and makes electrical contact with normally open contact 22. The positions of the armature 14 and the moving contact 24 at this point are indicated by dotted lines in FIG.
4b and 24b.

Armature 14 continues to rotate until it hits mechanical stop 34, as shown by dotted line 14c. In this position, the elastically movable contact 24 is slightly deformed as shown by the dotted line 24c.

The distance that armature 14 moves from position 14b to position 14c is referred to as armature overtravel. The resiliency of the moving contact 24 allows it to flex and accommodate excessive movement of the armature. The amount of excess travel determines the mating force between contacts 22 and 24, which directly affects relay performance characteristics such as contact resistance, bounce and life.

Excess travel in a particular relay is typically caused by static contacts 22
and stop 34 during configuration. Once set, the excess travel distance will probably not change. However, in practice, subsequent relay processing, testing and handling can change the overtravel distance. Prior to the present invention, the method of ascertaining overtravel distance was through physical measurements, which is virtually impossible in the case of sealed relays.

In the present invention, excess migration can be measured electrically as follows. In FIG. 2, relay coil 12 is connected in series with current measuring resistor 36. In FIG.

This series circuit is connected via a switch 38 to a voltage source V1, which is set to the nominal coil voltage. In the following discussion, all voltages are taken in relation to the ground terminal in the figure. The voltage developed across resistor 36, as sensed on line 39, is proportional to relay coil current 1c. Current coil voltage appearing on line 40 ■. approximately equal to.

The stationary contact 22 is connected to a voltage source 2 set at any suitable voltage suitable for detecting relay contact closure.

The moving contact 24 is grounded via a resistor 42. Resistor 42 together with voltage source 2 establishes the nominal contact current level. Voltage on line 44 ■. The presence of the symbol indicates that the contact point 24 is in contact with the contact point 22.

FIG. 3 shows the coil current ■ as a function of time after closure of switch 38 in the circuit of FIG. 2 due to the voltage appearing on line 39 and the voltage appearing on line 44. It is a graph showing the waveform of.

Coil current■. is upper bound to the well-known exponential formula. Eventually, sufficient magnetic force can be utilized to move the armature 14, which carries the moving contacts 24 with it. When contact 22 is touched, a step change in voltage appears on line 44, an event shown in FIG. 3 as occurring at time T1. Armature 14 continues its movement until it hits stopper 34.

The sudden change in speed when the armature 14 hits the stopper 34 causes a relay coil current ■ due to the magnetic coupling between the armature 14 and the coil 12. It has been found that a recursion point 46 occurs in the waveform of . As shown in Figure 3, this inflection point generally occurs as the current waveform resumes its exponential rise.
It is characterized by a negative slope of the current waveform followed by a relatively sharp transition to a positive slope. The recursion point 46 is at time T in FIG.
It is shown as occurring in 2.

It has also been found that for a given relay design, a relationship may be established between the armature overtravel distance and the time interval from time T1 to time T2 in FIG. This is because, for a fixed set of environmental conditions and coil voltages, armature speed does not vary appreciably between relays of a common design.

One way to determine the relationship between the above time intervals and armature overtravel for relays of common design is as follows. That is, a large number of such relays may be constructed and the armature overtravel in each of them may be physically measured using, for example, calibrated shims. Ideally, some of the relay prototypes in this group would be adjusted to the minimum amount of excess travel and some would be adjusted to the maximum allowable limit of excess travel.

Record the measured distances so they can be correlated to each relay. Each relay is then connected to the circuit of FIG. 2, and the desired time interval is measured and recorded. From the correlation of this data, a satisfactory time duration range representing a satisfactory overtravel range is arrived at by establishing a relationship between the time interval and the overtravel distance.

From the above description, it can be seen that the present invention provides a method for electrically measuring armature overtravel applied to a relay without the need for access to the interior of the relay or the need for any physical measurements.

The circuit of FIG. 2 can be made to automatically test for relay overtravel by combining it with the circuit shown in block diagram form in FIG.

In FIGS. 2 and 4, a signal appearing on line 39 and representing coil current I is provided as an input signal to slope detection circuit 48. In FIG. The purpose of the circuit 48 is to detect the inflection point 46 by detecting a change in the current waveform, for example from a negative slope to a positive slope. Circuits of this type are well known to those skilled in the art.

The output signal from circuit 48 is provided to a stop input terminal of timer 50. The signal appearing on line 44, used to indicate the closure of contacts 22.24 as described above, is activated by timer 5.
0 is applied to the start input terminal. Representing coil operation,
The signal appearing on line 40 is applied to the momentary reset input of timer 50.

The output signal from timer 50 is provided to the input terminal of a numerical display 52, such as an LED or LCD display. This timer output signal is also applied to the input terminal INICt of the window comparator 54. A signal representing the upper limit of allowable time duration (representing the maximum allowable overtravel distance) for the class of relays under test is provided on line 56 to the upper limit input terminal UL of comparator 54. A signal representing the lower limit of time duration is provided on line 58 to the lower limit terminal LL of comparator 54.

The Bus J output signal from comparator 54 is provided to a "pass" indicator 60 and the "fail" output signal from comparator 54 is provided to a "fail" indicator 62.

Indicators 60,62 may be visual or audible indicators. Window comparator 54 provides a pass output signal when its input signal falls between the upper and lower limits provided on conductors 56, 58, and otherwise provides a fail signal.

The operation of the circuit of FIG. 4 together with the circuit of FIG. 2 is as follows. That is, when the relay under test is energized by closing switch 38, a signal appears on conductor 40 that instantaneously resets timer 50 to zero. When contact between contacts 24 and 22 occurs, a signal appearing on line 44 is activated by timer 50.
start.

When a recursion point 46 occurs in the current waveform, as detected by circuit 48, an output signal is provided by this circuit to stop timer 50. Next, the timer 50 causes the display 5 to
The output signal applied to comparator 52 and comparator 54 represents the desired time duration indicative of excess travel path 1f, which is displayed by indicator 52. This time-duration signal is compared to predetermined upper and lower limits by comparator 54, which provides a pass or fail indication using indicators 60 and 62.

The circuit described above provides fast path/
Gives a fail indication. Of course, the comparator 54 can also be configured to provide a pass/fail indication for the window comparator operations described above based on exceeding only the upper limit or falling below only the lower limit.

Although the present invention has been disclosed above and specific embodiments have been described in detail,
The present invention is not limited only to these examples. Many variations within the spirit and scope of the invention will occur to those skilled in the art. Accordingly, the scope of the present invention is limited only by the scope of the claims.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a typical electromechanical relay,
FIG. 2 is a schematic diagram showing the connection between the relay coil and the contacts employed in carrying out the present invention; FIG. 2 is a graph showing the coil current waveform and contact closure as a function of time as measured at various points in time in the circuit of FIG. 2; FIG. FIG. 2 is a block diagram of a test circuit. [Explanation of symbols of main parts] lO... Relay 12... Coil 14... Armature 20.22... Stationary contact 2.1... Moving contact 34... Mechanical stopper 36...・Current measurement resistor 48...Gradient detection circuit 50...Timer 52...Numeric display 54...Window comparator 60.62...Display Ft (,,4 = ヱ蝮数

Claims (1)

[Claims] 1. A method for measuring an armature excessive travel distance from a point where a designated moving contact contacts a corresponding stationary contact at the same time as energizing a coil of an electromechanical relay to a mechanical stopper, comprising: and electrically monitoring the moving and stationary contacts to detect when the moving contacts touch; electrically monitoring the coil current waveform as a function of time; and energizing the relay coil. , establishing a first time point simultaneously with the occurrence of mutual contact between the two contacts; detecting the occurrence of a recursion in the coil current waveform caused by the armature contacting the stopper; and the first time point. a method for measuring armature overtravel distance comprising the steps of: measuring the time duration from to detection of the occurrence of coil current recursion, and relating the measured time duration to armature overtravel. 2. Claim 1 further includes: providing a first predetermined time interval; comparing the measured time interval with the first predetermined time interval; is less than a predetermined time interval. 3. Claim 1 or 2 further includes: providing a second predetermined time interval; comparing the measured time interval with the second predetermined time interval; and the measured time. providing an indication if the interval is greater than a second predetermined time interval. 4. In a device that measures the armature overtravel distance from the point where a designated moving contact touches the corresponding stationary contact at the same time as the coil of an electromechanical relay touches the corresponding stationary contact, when the stationary and moving contacts touch. means for electrically monitoring the moving and stationary contacts to detect when the contacts are moving; means for electrically monitoring the coil current waveform as a function of time; means for energizing the relay coil; means for establishing a first time point simultaneously with the occurrence of contact; means for detecting the occurrence of a recursion in the coil current waveform caused by the armature contacting the stopper; and means for relating the measured time duration to armature overtravel by measuring the time duration until detection of the occurrence. 5. Claim 4 further includes: means for providing a first predetermined time interval; means for comparing the measured time interval with the first predetermined time interval; and the measured time interval is the first predetermined time interval. means for providing an indication if the time interval is less than a predetermined time interval. 6. Claims 4 or 5 further include: means for providing a second predetermined time interval; means for comparing the measured time interval with the second predetermined time interval; and the measured time. and means for providing an indication if the interval is greater than a second time interval.