Solution to unstable performance of electric forklift combination switch

At present, the combination switch has been widely used on our company's F series 2 to 4 t electric forklifts, but there is a problem of unstable performance. After many times of disassembly, inspection and analysis, it is confirmed that the main reasons are as follows: the moment of turning the handle knob switch, the contact area between the contacts is small, and the current changes greatly, which will cause the contacts to heat up over time; after long-term use, the touch The points are worn, oxidized and corroded, which increases the resistance between the contacts, causing the contacts to heat up more.　　 Contact heating will cause the contacts on the handle body to loosen or stick, causing the combined switch to heat up, its performance is unstable, or even its function fails. The shape and contact position of the combined switch used are shown in Figure 1, and the wiring of the combined switch and the additional gear of the handle is shown in Figure 2.　　In order to make the combined switch performance stable and prolong its service life, the current passing through the contacts should be reduced to reduce the heating of the contacts. The most convenient way to reduce the current through the contact is to add a bypass switch to divert the current. After research, it is determined that the specific method is to add a bypass auxiliary electromagnetic relay to the combined switch, the relay model is HD4195A, and the contact capacity is 40 A.　　The circuit before and after the improvement of the combination switch is shown in Figure 3. The working principle of the modified combination switch is as follows: line number 10 is the input terminal of the switching power supply, line number 11 is the output line of the width indicator light switch, and line number 9 is the headlight switch output line (headlight power is 110 W, and the current is about Is 10 A). When the headlight switch is turned on, the contacts of the combination switches 10 and 9 are contacted, so that the solenoid coil of the relay is energized, and the main contacts of the relay are connected to the wires 10 and 9. After the improvement, the energizing capacity of the switch contact circuit has been significantly strengthened. Even if the power load current fluctuates, the combined switch contacts will not be damaged, thereby avoiding the burning of the combined switch due to the heating of the contacts. After experimental verification, the improved combination switch achieved the expected effect, and the unstable performance of the relay did not occur again.
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