How to realize the electrical control of the car c

2022-08-23
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[expert clinic] how does the automobile cooling system realize electrical control

[expert clinic] how does the automobile cooling system realize electrical control

18:15 source://

original title: [expert clinic] how does the automobile cooling system realize electrical control

host expert: Wang Xuehui

senior technician of automobile maintenance, who has been working in the front line of maintenance for more than 20 years

Shenzhen auto maintenance industry distinguished experts

the first excellent technician in Shenzhen

automobile expert specially appointed by Shenzhen Consumer Commission

guest of the "car loving" column of Shenzhen communications radio

guests of FAW Toyota's "car in the air forum"

won the third place in the national Toyota skill competition in 2000

expert clinic

question 1:

when troubleshooting a BMW car "the water temperature is close to boiling", a prompt of "the temperature regulation actuator" working improperly appears when retrieving the fault code, which obviously belongs to the fault of the electronic control components of the engine cooling system. In the engine cooling system of Toyota cars that are usually repaired, only the thermostat with pure mechanical control regulates the temperature, and there is no electrical control system. Please ask Mr. Wang, how does the automobile cooling system realize electrical control

answer:

the so-called "temperature regulating actuator" refers to the "thermostat" in the engine cooling system. Thermostat is essentially a "thermostat", which is used to change the circulation mode of engine coolant according to the temperature of cooling water, automatically adjust the amount of water entering the radiator, control the heat dissipation capacity of the cooling system, and ensure that the engine works within the appropriate temperature range, such as taking more complex parameters as required

traditional engines use a wax thermostat, which senses the temperature of the coolant through thermal paraffin, so that the paraffin volume expands to different sizes, so as to push the central rod of the thermostat, and then control the opening size of the valve to realize the switching of the coolant size cycle. The thermostat must be in good technical condition, otherwise it will seriously affect the normal temperature of the engine. However, due to the influence of scale deposition on the surface of the temperature sensitive paraffin on the mechanical thermostat, it is often unable to sensitively sense the temperature, thus affecting the accurate opening of the valve. If the main valve of the thermostat is opened too late, the engine temperature will be too high and the heat cannot be dissipated in time; If the main valve is opened too early, the engine temperature will be too low, the preheating time will be extended, and the fuel consumption will be increased

in BMW, Audi, Volkswagen and some European and American vehicles, such as Audi 4-cylinder 1.6L, the cooling system of the electronically controlled engine is now used. Figure 1 shows the outline of BMW electronic thermostat. This cooling system includes coolant temperature regulation, coolant circulation mode control and cooling fan speed control. The coolant temperature regulating actuator is equivalent to adding an electric control device to the traditional thermostat, so it is called "electronic thermostat". This is a thermostat with more sensitive temperature sensing and better temperature control effect

Figure 1 the shape of BMW electronic thermostat

is different from the traditional thermostat in that "temperature adjustment actuator" has a thermal wax device that senses the water temperature, and a heating resistor element is installed in the temperature sensor. By controlling the resistance plus anyway, we are) some machines have a fuel filler in it. The amount of heat can accurately control the opening of the thermostat valve and the shaft rotation time of the strand photoelectric encoder. Heating resistance elements are in the form of heating rods and thick film resistors

"electronic thermostat" temperature sensing paraffin, equipped with a resistance value of about 12 ω When the resistance is powered on, it heats the paraffin, and the paraffin expansion causes the valve to shift and open. The linear adjustment between the displacement and the voltage can realize more accurate control of the coolant circulation, and then can fine adjust the temperature of the engine coolant. The voltage applied to the heating resistor is adjusted by the coolant control computer

compared with the traditional thermostat, the electronic thermostat can control the water temperature more accurately, which is more beneficial to the cycle of the engine and lower the fuel consumption of the vehicle. Some riders have carefully tested that when the electronic thermostat is in normal condition, the fuel consumption of the engine is about 9.5l per hundred kilometers, and the fuel consumption of vehicles that need to go through multiple processes such as fiber surface treatment and sizing will increase to 10.6l per hundred kilometers when the electronic thermostat is damaged

in the actual maintenance, it is found that the damage of the "electronic thermostat" is often caused by the poor connector of the heating resistance or the broken wire of the heating resistance, which will cause the expanded paraffin in the thermostat to be unable to be electrically heated. At this time, the expansion displacement of the paraffin becomes smaller, it is difficult to realize the large circulation of the cooling liquid, and the coolant cannot effectively dissipate heat through the radiator, so the engine temperature has been running at a high level. Figure 2 shows that the heating resistance of BMW electronic thermostat is broken, resulting in the damage of the electronic thermostat

Figure 2 heating resistance of BMW electronic thermostat has been disconnected

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