The intake preheating device of Santana car consists of intake manifold preheating thermistor switch, intake manifold preheating relay and intake manifold preheater, as shown in Figure 4-35. The cover of intake manifold preheating relay is marked with the words "1"; Installed in position 2 of the central circuit board. The intake manifold preheater is installed under the intake manifold. The preheater is made into multiple needles to increase the heating area, and then it is put into the air inlet. After the preheater is electrified, its surface temperature can reach about 180℃, the mixture is preheated when it is inhaled, and the unevaporated fuel can be evaporated when it passes through, thus obtaining a better mixture.
The heating element of the preheater adopts PTC electrothermal ceramic material with positive temperature coefficient, which has the characteristic that the resistance increases with the increase of temperature, so that the preheating temperature can be automatically controlled, that is, constant temperature control, which can save electric energy. The temperature and current characteristic curves of PTC electrothermal elements are shown in Figure 4-36. When the outside temperature is 25℃, its resistance value is 0.2-0.4 ohm. When the circuit is connected, the heating current will reach 40-60 A in an instant, and the temperature will rise rapidly. 1 min, the temperature can reach 60-80℃, and it can reach 180℃ in 3 minutes. At this time, the resistance tends to infinity, the current tends to zero, the temperature remains unchanged, and the circuit has almost no power consumption. As shown in figure 4-35:
The current flows from the ignition switch "15" to the black line → the A8 node of the central circuit board → the fuse S17 of the central circuit board → the D2 node of the central circuit board → the black line → the intake manifold preheating thermistor switch → the purple/black line → the D 13 node of the central circuit board → the intake manifold preheating relay post of the central circuit board → the relay excitation coil → the relay post B5.
Current flows from the positive pole of the battery to the P node of the central circuit board, to the "30" terminal of the intake manifold preheating relay, to the upper contact of the relay, to the lower contact of the relay, to the terminal of the relay B7, to the red line, to the heating resistor of the intake manifold preheater and to the ground.
I. Working conditions of air inlet preheating device
The inlet preheating thermal switch F35 is installed above the engine exhaust pipe.
When the outlet temperature of the engine is lower than 65℃, the thermal switch F35 is closed, the contact of relay J8 1 is closed, and relay J8 1 works, connecting the power supply of Line 30 with the intake preheater N5 1 with a conical radiating rod in the intake pipe to preheat the intake air and improve the working state of the engine cold machine. When the outlet water temperature of the engine is higher than 65℃, the thermal switch F35 is automatically turned off, and the contact of relay J8 1 is disconnected, thus cutting off the current of the preheater and stopping the intake air preheating.