At present, the combination switch has been widely used in our company's F Series 2 ~ 4 t forklift, but it has the problem of unstable performance. After many times of disassembly, inspection and analysis, it is confirmed that the main reasons are as follows: at the moment of turning the handle knob switch, the contact area between the contacts is very small, while the current changes greatly, which will cause the contact to heat over a long time; After long-term use, the contacts are worn, oxidized and corroded, which increases the resistance between the contacts, resulting in more heating of the contacts.
Contact heating will cause the contact on the handle body to loosen or adhere, resulting in combined switch heating, unstable performance and even functional failure. The shape and contact position of the combined switch are shown in Figure 1, and the additional gear wiring of the combined switch and handle is shown in Figure 2.
In order to stabilize the performance and prolong the service life of the combined switch, the current passing through the contact should be reduced to reduce the heating of the contact. The most convenient way to reduce the contact current is to add a bypass switch to divert the current. The specific method is to increase the capacity of the auxiliary relay as 95A, and the specific method is to increase the capacity of the auxiliary relay as 41a.
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: wire No. 10 is the input end of the switching power supply, wire No. 11 is the output line of the side marker lamp switch, and wire No. 9 is the output line of the headlamp switch (the headlamp power is 110 W and the energizing current is about 10 A). When the headlamp switch is turned on, the combined switch contacts 10 and 9 to energize the relay solenoid coil, and then the main contact of the relay connects 10 and 9 wires. After the improvement, the power on capacity of the switch contact line is significantly strengthened. Even if the load current of the power supply fluctuates, the contact of the combined switch will not be damaged, so as to avoid the phenomenon of burning the combined switch due to contact heating. Through experimental verification, the improved combination switch has achieved the expected effect, and the instability of relay performance has not occurred again.
