JP2000182495A - Failure preventing device for contact switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a failure preventing device of a contact switch, whose operability can be improved by surely reducing the frequency of device stop caused by imperfect contact, without increasing the number of part items. SOLUTION: This device includes a contact switch and a control part 10 for forcibly opening or closing the contact switch, when the contact switch is not operating. When forcibly opening or closing the contact switch, the control part 10 should preferably open or close it plural times in a predetermined time. Furthermore, the control part 10 should forcibly open or close the contact switch on at least either of such occasions as at the input of a circuit power supply, at every period of an approximately predetermined time, or at the detection of imperfect contact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact switch failure prevention device which can prevent a control device using a switch having contacts from being stopped due to a contact failure.

[0002]

2. Description of the Related Art When a contact of a switch is closed, an excessive current flows when the switch is closed, and the contact may be welded, or dust or dust may adhere between the contacts, resulting in malfunction of the contact. In order to prevent the occurrence of such a contact malfunction, various preventive measures have been conventionally considered.For example, a switch is regularly maintained and inspected, or a switch is provided with a failure prevention device. Or

[0003] For example, Japanese Patent Application Laid-Open No. 7-282705 discloses that an insulating cover provided around a fixed contact and a movable contact of an electromagnetic contactor (switch) applies an arc and heat generated at the time of interruption to the outside. To provide a hole to release
Responsive to the breaking operation of the movable contact, the fixed contact and the movable contact are shielded at the contact position and the separation position of the hole of the insulating cover at the contact position and the separation position, and at the position during the breaking operation of the movable contact, the insulating member is insulated. An electromagnetic contactor provided with a shield that opens a hole of a cover has been proposed. JP-A-6-303
No. 717 discloses that, in order to confirm the operation of the a-contact (NO contact) of the auxiliary relay of the protective relay device, at the time of automatic inspection, the a-contact of the auxiliary relay is forcibly turned on to activate the monitoring relay. A technique has been disclosed in which the operation of the monitoring relay is monitored by monitoring means.

[0004]

However, the above-mentioned conventional techniques have the following problems. The electromagnetic contactor disclosed in Japanese Patent Application Laid-Open No. 7-282705 requires a shield and means for driving the shield so as to open and close the hole of the insulating cover at a position in the middle of the closing operation of the movable contact. However, there is a problem that the number of parts increases and the cost increases. Also, even if a contact failure occurs, it cannot be detected and cannot be recovered, so that a control device or the like using this electromagnetic contactor has to stop its function.
Further, the technique disclosed in Japanese Patent Application Laid-Open No. 6-303717 also requires a monitoring circuit and a monitoring means such as a monitoring relay, and has a problem that the number of components increases and the cost increases. Furthermore, even if the generated contact failure can be detected, it cannot be recovered, so that the control device and the like using this protective relay must also stop functioning, and the operation rate of the entire device is reduced. Has occurred.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a contact switch capable of improving the operation rate by reliably reducing the frequency of device stoppage due to defective contacts without increasing the number of parts. The purpose of the present invention is to provide a failure prevention device.

[0006]

In order to achieve the above object, a first aspect of the present invention provides a contact switch and a control unit for forcibly opening and closing the contact switch when the contact switch is not operated. And a configuration including:

According to the first aspect of the present invention, dust such as dust between the contacts is removed by the vibration of the contact or by the compression and elimination by the contact due to the forced opening and closing of the contact switch. Therefore, since the cause of the contact failure is eliminated, the failure frequency of the switch can be reduced and the failure can be prevented. In addition, since a normal switch is used without having any special parts or the like for preventing a failure, the failure can be prevented without increasing the cost.

According to a second aspect based on the first aspect, the control section opens and closes a plurality of times within a predetermined time when forcibly opening and closing.

According to the second aspect of the present invention, the contacts are opened and closed a plurality of times within a predetermined period of time, so that the dust easily moves each time the contactor is operated. As a result, in addition to the effect of the first invention, dust is more reliably removed from between the contacts, so that poor contact can be prevented.

[0010] In a third aspect based on the first or second aspect, the control section is configured to provide at least one of at the time of power-on of the circuit, at a regular time approximately every predetermined time, or at the time of detecting a contact failure. Open and close forcefully.

According to the third aspect of the present invention, the circuit is forcibly opened and closed at least at the time of turning on the power of the circuit, at a regular time substantially every predetermined time, or at the time of detecting contact failure. It is possible to avoid a stop of a device (control device or the like) due to poor contact. Therefore, in addition to the effects of the first or second invention, the operation rate of the device can be improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described in detail below with reference to FIGS. 1 to 4 by taking a switch used in a traveling motor control circuit of a battery forklift as an example.

FIG. 1 shows an example of a traveling motor control circuit of a battery forklift. Referring to FIG. 1, a circuit to which a contact switch (hereinafter, referred to as a contactor) to be controlled by a failure prevention device according to the present invention will be described. I do. The positive terminal of the battery 1 is connected to one end of the armature 5a of the traveling motor 5 via the regenerative contactor 3 and the current detector 4, and the other end of the armature 5a of the traveling motor 5 is connected to the forward contactor 6. It is connected to the negative terminal of the battery 1 via the parallel circuit of the reverse contactor 7 and the chopper element 9. In the parallel circuit of the forward contactor 6 and the reverse contactor 7, the output contact common terminals 6a and 7a are connected to both ends of the field coil 5c of the traveling motor 5, and the output contact a terminal of the forward contactor 6 and the reverse contactor 7 And b
One of the terminals (here, terminal a) is armature 5a
And the other terminal (here, terminal b) is connected to the chopper element 9 (large current transistor, FET, etc.). The series circuit of the regenerative contactor 3, the current detector 4, and the armature 5a has a preliminary excitation circuit 2 including a resistor and a transistor for preliminary excitation of the field coil 5c.
And a parallel circuit with the plugging diode 12 are connected in parallel. Further, a flywheel diode 11 is connected in parallel to the series circuit of these parallel circuits and the parallel circuit of the forward contactor 6 and the reverse contactor 7, and a regenerative diode 13 is connected to a series circuit from the current detector 4 to the chopper element 9. Are connected in parallel.

The current detection signal of the current detector 4 is transmitted to the control unit 10
The control signals from the control unit 10 are output to the pre-excitation circuit 2, the chopper element 9, the coil 3c of the regenerative contactor 3, the coil 6c of the forward contactor 6, and the coil 7c of the reverse contactor 7, respectively. Also, the voltage across the contact of each contactor is input to the control unit 10. In the present embodiment, an example is shown in which the voltage between both ends of the regenerative contactor 3 is input to the control unit 10, but the same applies to other contactors.

The control unit 10 comprises a central processing unit such as a microcomputer and a numerical processing unit and an input / output interface circuit. The control unit 10 controls the preliminary excitation circuit 2, the chopper element 9, the coil 3c of the regenerative contactor 3, and the coil 6c of the forward contactor 6.
And a control signal is output to the coil 7c of the reverse contactor 7 to control the current of the traveling motor 5 to control the power running operation, the plugging operation, and the regenerative operation during normal traveling.

That is, during power running operation, the regenerative contactor 3 is turned on, and the excitation command to the pre-excitation circuit 2 is turned off, and the forward contactor 6 or the reverse contactor 7 is turned on in response to forward or backward travel. The chopper element 9 is switched at a predetermined switching time and cycle so that the current value detected by the current detector 4 becomes a predetermined target drive current. Thereby, from the battery 1, the regenerative contactor 3, the traveling motor 5, the forward contactor 6 (or the reverse contactor 7), the field coil 5c, and the reverse contactor 7
A drive current of a predetermined magnitude flows through the traveling motor 5 via the (or forward contactor 6) and the chopper element 9 in sequence. Further, when the forward / reverse lever is switched during the powering operation, if the excitation command to the pre-excitation circuit 2 is off, the plugging operation is performed, and the forward contactor 6 and the reverse contactor 7 are switched to the field coil 5c. An exciting current reverse to that during the power running flows through the flywheel diode 11 and the regenerative contactor 3, whereby the traveling motor 5 becomes a generator, and the traveling current from the traveling motor 5 passes through the plugging diode 12 and the regenerative contactor 3. , The plugging braking is applied to the traveling motor 5. When the reversing contactor 3 is turned off when the forward / reverse lever is switched during the powering operation, the regenerative operation is performed. At this time, an excitation command to the preliminary excitation circuit 2 is turned on for a predetermined time to activate the field coil 5c. Pre-excitation is performed, whereby the traveling motor 5 changes from an electric motor to a generator. Thereafter, when the chopper element 9 is turned on, the armature 5a of the traveling motor 5, the forward contactor 6 (or the reverse contactor 7), the field coil 5c, reverse contactor 7 (or forward contactor 6), chopper element 9, regenerative diode 1
3, and the generated current (regenerative current) circulates via the armature 5a of the traveling motor 5, and when the chopper element 9 is turned off, this current is generated by the armature 5a of the traveling motor 5, the forward contactor 6
(Or the reverse contactor 7), the field coil 5c, the reverse contactor 7 (or the forward contactor 6), the flow through the flywheel diode 11, the battery 1 and the regenerative diode 13, and thus the rotational energy until the traveling motor 5 reverses. To the battery 1. At this time, regenerative braking is applied to the traveling motor 5.

Further, the control unit 10 inputs the voltage between both ends of each contactor as described above, performs a predetermined arithmetic processing described later based on the voltage value, and determines whether or not each contactor has a failure. When it is determined that there is a failure, a predetermined contactor opening / closing operation is performed to recover the failed contact.

There are several possible timings for the above-mentioned contactor failure diagnosis as follows. 1) When the power-on switch of the control device is turned on (for example, when the power key switch of the battery forklift is turned on here). 2) During periodic failure diagnosis. 3) When a contact failure is detected. It should be noted that it is also possible to combine these.

FIG. 2 shows an example of a control flowchart of the control unit 10 when the power-on switch is turned on. In addition, each processing step number is represented by adding S. First, S1
Confirms that the power is turned on, and then opens and closes each contactor a predetermined number of times for a predetermined time in S2. Thereafter, a normal control process is performed in S3. That is, in the present embodiment, the opening and closing of each of the contactors 3, 6, 7 is controlled in order to perform power running control, regeneration control, and plugging control of the traveling motor 5.

FIG. 3 shows an example of a control flowchart at the time of periodic failure diagnosis, which will be described below with reference to FIG. In S11, a normal control process is performed in the same manner as in S3. Next, in S12, it is checked whether or not the forward / reverse lever is in neutral at a predetermined cycle time (ie, a fixed time for measuring the failure diagnosis cycle time). If it is not neutral, the timer value of the failure diagnosis cycle measurement timer is cleared in S13, and the process returns to S11 to repeat the above-described processing and wait until it becomes neutral. Then, when the neutral state is obtained in S12, the timer value of the timer for measuring the failure diagnosis cycle is increased by 1 in S14, and then in S15
It is checked whether or not the increased timer value is larger than a predetermined set value.
The process returns to 1 and the above processing is repeated until the value becomes larger than the set value. If it exceeds the set value, it is determined in S16 that the failure diagnosis cycle time has been reached, and the timer value is cleared for the next measurement of the failure diagnosis cycle time.
At 7, a predetermined contactor is opened and closed a predetermined number of times for a predetermined time. Then, the above processing is repeated from S11.

The processing method of the control unit 10 when detecting a contact failure will be described with reference to the control flowchart shown in FIG. First, in S20, the opening / closing operation flag used for the subsequent control processing is set to off. Next, in S21, a normal control process is performed in the same manner as described above. In S22, it is checked whether an ON command for the regenerative contactor 3 has been output. If not, the process proceeds to S23 and the contact voltage of the regenerative contactor 3 is changed. Check whether (the voltage between both ends) is not equal. If they are not equal, the opening / closing operation flag is set to OFF in S25, and then the process returns to S21 to repeat the above processing. If they are equal, it is a case where the regenerative contactor 3 is prying and remains ON, etc. S2
The processing shifts to 6. If the ON command of the regenerative contactor 3 is output in S22, it is checked in S24 whether the contact voltages (both ends voltage) of the regenerative contactor 3 are equal, and if they are equal, the opening / closing operation flag is set to OFF in S25. After that, the process returns to S21 to repeat the above-mentioned processes. If they are not equal, it is a case of contact failure, and the process proceeds to S26. Then, in S26, it is checked whether the opening / closing operation flag is on. If the opening / closing operation flag is off, a command to open / close the regenerative contactor 3 a predetermined number of times for a predetermined time is output in S27.
At 28, the opening / closing operation flag is turned on, and the process returns to S21 to repeat the above processing. If the open / close operation flag is ON in S26, it is determined that a failure has occurred in S29, and then the vehicle is stopped in S30.

As described above, according to the present embodiment, when the regenerative contactor 3 is not operated, the regenerative contactor 3 is forcibly opened and closed, so that a predetermined vibration is given to the contact and a dust between the contacts is generated. The function of compressing and eliminating etc. works. As a result, even if an insulator such as dust or dust is mixed between the contacts of the regenerative contactor 3, dust and the like are removed by the vibration and the elimination action. Further, by continuously opening and closing the regenerative contactor 3 a predetermined number of times during a predetermined time, even if there is a contact failure, the possibility that the contact failure is released increases. Therefore, power running control of the traveling motor of the battery forklift
A problem that regenerative braking and plugging braking do not work can be avoided, and the traveling motor control can be reliably performed. Moreover, when the control device is turned on, periodically, or when a contact failure is detected, the switching operation for contact recovery as described above is performed, so that the contacts of the regenerative contactor 3 can be normally maintained at all times. Thus, the traveling motor can be more reliably controlled.

As described above, according to the present invention, the forcible opening and closing of the contact switch causes dust such as dust between the contacts to be removed.
It is removed by vibration of the contact or by compression and rejection by the contact. Therefore, since the cause of the contact failure is eliminated, the failure frequency of the switch can be reduced and the failure can be prevented. In addition, since a normal switch is used without having any special parts or the like for preventing a failure, the failure can be prevented without increasing the cost.

Further, since the contacts are opened and closed a plurality of times within a predetermined time, dust is more likely to move each time the contactor is operated. As a result, dust is more reliably removed from between the contact points, thereby preventing poor contact.

Furthermore, since the circuit is forcibly opened and closed at the time of turning on the power of the circuit, at a regular time approximately every predetermined time, or at the time of detecting a contact failure, the device always has a contact failure. (Control devices and the like) can be prevented from being stopped. Therefore, the operation rate of the device can be improved.

[Brief description of the drawings]

FIG. 1 is an example of a traveling motor control circuit of a battery forklift using a contact switch to be controlled by a failure prevention device according to the present invention.

FIG. 2 is an example of a control flowchart when a power-on switch is turned on in a control unit of the failure prevention device according to the present invention.

FIG. 3 is an example of a control flowchart at the time of periodic failure diagnosis in the control unit of the failure prevention device according to the present invention.

FIG. 4 is an example of a control flowchart when a contact failure is detected in the control unit of the failure prevention device according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 battery 2 pre-excitation circuit 3 regenerative contactor 4 current detector 5 traveling motor 5a armature 5c field coil 6 forward contactor 7 reverse contactor 9 chopper element 10 control unit 11 flywheel diode 12 plugging diode 13 regenerative diode

Claims (3)

[Claims] An apparatus for preventing failure of a contact switch, comprising: a contact switch; and a control unit for forcibly opening and closing the contact switch when the contact switch is not operated. 2. The contact switch failure prevention device according to claim 1, wherein the control unit (10) opens and closes a plurality of times within a predetermined time when forcibly opening and closing. Failure prevention device. 3. The failure prevention device for a contact switch according to claim 1 or 2, wherein the control unit (10) is configured to control at least at the time of turning on the power of the circuit, at a regular time of approximately every predetermined time, or at the time of detecting a contact failure. A failure prevention device for a contact switch, which is forcibly opened and closed in any case.