Forklift combination switch performance instability solution

At present, the combination switch has been commonly used in our company's F series 2 to 4 t forklifts, but there are performance instability problems. After repeated inspections and analysis, the main reasons are as follows: The moment the handle knob is turned, the contact area between the contacts is very small, and the current changes greatly. After a long time, the contact heat is generated; after long-term use, the touch Point wear, oxidation, and corrosion increase the resistance between the contacts, causing the contacts to heat up.

The contact heat will cause the contact on the handle body to loose or stick, causing the combination switch to heat, unstable performance, or even function failure. The shape of the combination switch used and the position of the contacts are shown in Figure 1. The wiring of the combination switch and handle with additional gears is shown in Figure 2.

In order to stabilize the combined switch performance and extend the service life, the contact passing current should be reduced to reduce the heat generation of the contacts. The easiest way to reduce the contact current is to increase the bypass switch and shunt the current. After research and confirmation, the specific approach is to add a bypass auxiliary electromagnetic relay to the combination switch. The continuous model is HD4195A and the contact capacity is 40 A.



The combination switch improves the front and rear circuits as shown in Figure 3. The working principle of the reconfigured combination switch is as follows: Line No. 10 is the input end of the switching power supply, Line No. 11 is the output line of the wide light switch, and Line No. 9 is the output line of the headlight switch (the headlight power is 110 W, and the current is approximately Is 10 A). When the headlight switch is turned on, the contact of the combination switch 10, 9 is contacted, so that the relay solenoid is energized, and the relay main contact is connected with the 10, 9 connection. After the improvement, the energizing ability of the switch contact circuit is significantly enhanced. Even if the load current of the power supply fluctuates, the combination switch contact will not be damaged, thereby avoiding the burn-out of the combination switch due to the contact heat. Through experimental verification, the improved combination switch has achieved the desired effect, and the phenomenon of unstable relay performance has not occurred again.