How does the common water cooling system work? What are the big cycle and the small cycle?

When the engine is working, the temperature of the cylinder combustion chamber can reach 2000-2500 degrees. Long-term operation will cause the engine temperature to be too high and affect performance, and even damage the parts. The cooling system is responsible for dissipating the heat of each part in time to prevent them from overheating. Common cooling systems are mainly divided into two categories: air cooling system and water cooling system. Because the water cooling system cools evenly, takes effect quickly and has low noise, it is widely used in household engines.

The water cooling system is mainly composed of a water pump, a radiator, a cooling fan, a thermostat, an engine body water jacket, a cylinder head water jacket, and a water pipe loop. After the engine is started, the water pump will be driven to work. Under the action of the water pump pressure, the coolant begins to enter the engine body water jacket from the water pipe. Since the engine body water jacket is distributed around the cylinder, the coolant will absorb heat when it flows through, and then continue to flow into the cylinder head water jacket, and then absorb heat from the cylinder head water jacket again and flow out, and then enter the thermostat. The thermostat is a temperature control valve that can automatically adjust the opening and closing of the valve according to the temperature to control the flow direction of the coolant. When the engine is just started, the temperature of the coolant is low. Under the control of the thermostat, the coolant flows directly back to the water pump, and then flows to the engine body again after being pressurized by the water pump. In this cycle, since the coolant flows in this small range of the water pipe loop, it is called a small cycle. The radiator does not participate in the work during the small cycle, so the heat of the engine will not be lost, which is conducive to engine warm-up. Therefore, in winter, you need to wait a few minutes after starting the vehicle before starting it again. This is conducive to the preheating of various engine parts and has the function of protecting the parts. After the engine has been running for a period of time, the temperature of various parts rises, and the temperature of the coolant also rises accordingly. When a certain temperature is reached, the thermostat will gradually open the valve leading to the radiator. At the beginning, the valve opening is small, and only part of the coolant will flow to the radiator. After the radiator dissipates heat and cools down, it returns to the water pump through the water pipe. This process is called a large cycle.

At the same time, another part of the coolant will flow directly back to the water pump through the thermostat. Therefore, both the large and small cycles will participate in the work in this process, and they work together. When the engine temperature continues to rise and the coolant temperature exceeds the standard value of the thermostat temperature, the thermostat valve will be fully opened, and the valve leading to the water pump will be automatically closed. At this time, all the coolant will flow to the radiator and enter the full large circulation mode. In this process, the coolant passes through the radiator and dissipates heat and cools down under the action of the cooling fan, and the heat is finally dissipated into the air. The cooled coolant continues to flow to the water pump through the pipeline, and the engine’s heat dissipation work continues in this way over and over again. This is the complete working process of the engine cooling system.

In conclusion, the component that prevents the engine from overheating is the thermostat. When it detects that the temperature rises, it will open the valve to start the heat dissipation function, so that the coolant can continue to cool the engine. The small circulation mode of the coolant is conducive to the preheating of the engine. It is best to warm up the engine for a few minutes before driving in winter, which helps protect the parts. The large circulation mode of the coolant system is a complete heat dissipation mode, at which time the cooling system fully dissipates heat for the engine.

What is PDC reversing radar?

Park Distance Control (PDC) is also commonly referred to as reversing radar. As an important safety auxiliary device in modern cars, PDC system mainly consists of ultrasonic sensors (commonly known as probes), controllers and displays (buzzers). When reversing, it helps the driver “see” things that the rearview mirror cannot see, and informs the driver of the surrounding obstacles with a more intuitive sound display, eliminating the trouble caused by the driver looking around when parking, reversing and starting the vehicle, and helping the driver eliminate the defects of blind spots and blurred vision, thereby improving driving safety.

How does PDC parking radar work?
The working principle of the reversing radar is based on sound wave technology, which uses ultrasonic sensors. It transmits and receives sound waves through the ultrasonic sensor installed at the rear of the car. When the sound waves encounter obstacles, they will be reflected back, and then the system will calculate the distance and position of the obstacle. The controller will process these signals. When the distance reaches the preset safety range, the display or buzzer will issue a warning. For example, when we put the car in reverse gear and turn on the reversing radar system, the sensor will emit ultrasonic beams to the rear of the car. These beams will bounce and return to the sensor. The sensor can measure the time difference of these beams to calculate the distance and position of the obstacle from the car. Specifically, the reversing radar will emit hundreds of ultrasonic waves, which propagate at a very fast speed and interact with obstacles. When the beam hits the obstacle and returns, the sensor can measure the time difference of the beam. By calculating the speed of the sound wave, the system can determine the distance between the obstacle and the car. These distance data will be transmitted to the display screen inside the car and displayed to the driver in a visual way. When the vehicle approaches an obstacle, the PDC system will alert the driver through the alarm system, either with a beep or a display on the dashboard, telling the driver to pay attention to nearby obstacles and avoid collisions.

What is the role of the PDC reversing radar?
In terms of safety assistance, it can help the driver better judge the distance between the vehicle and surrounding objects, especially when the line of sight is limited. With it, driving and parking in narrow spaces are safer. In terms of avoiding accidents, it is easy to ignore potential dangers when reversing due to limited vision, but PDC can issue an alarm in time to effectively reduce the risk of reversing collision accidents. Not to mention the convenience of parking, it not only improves safety, but also makes parking super convenient, allowing drivers to park the car more easily, reducing tension and improving the overall driving experience.

How does a car’s hydraulic brake system work?

A speeding car can stop immediately by stepping on the brakes when it encounters an emergency. So what principle does the car use to brake and stop? In modern cars, the hydraulic brake system is the most commonly used brake system, which is what we often call the brake system. The principle of hydraulic braking is to seal the liquid in the brake line without air. Because the liquid cannot be compressed and can transmit power 100%, when the liquid is pressurized, the liquid transmits the pressure through the pipeline to the piston of the brake caliper of each wheel. The piston drives the brake caliper to clamp the brake pad, thereby generating huge friction to slow down the vehicle. Since the liquid can bend without being affected by the pipeline route, hydraulic braking is currently the most effective braking solution.

So what parts does the automobile hydraulic brake system use to achieve braking? First of all, there are brake pedals, brake push rods, brake control modules installed in iron boxes, master cylinders, brake oil tanks, and brake lines. When the driver steps on the brake pedal, mechanical force is transmitted to the brake push rod, which transmits power to the brake control module. The control module converts the mechanical force into vacuum liquid pressure and transmits it to the sealed master cylinder. The piston in the master cylinder pushes the brake oil to the four brake lines under the action of hydraulic pressure. When the pressure is released, the brake oil returns to the master cylinder. There must be enough brake oil in the tank to prevent it from entering the hydraulic system. When the wheel brakes, the brake pedal is stepped on. The brake control module converts the mechanical force into liquid pressure and pressurizes it, causing the brake oil in the master cylinder to flow to each brake line. The pressure of the brake oil is transmitted to the piston of each wheel brake caliper through the pipeline. The piston drives the brake caliper to clamp the brake disc and slow down the wheel. When the brake pedal is released, the brake oil returns to the master cylinder, the piston of the wheel brake caliper is released, and the wheel starts to turn again. This is the working principle of the hydraulic brake system.

How to adjust the rearview mirror?

We all know that improper adjustment of the car’s rearview mirror will create blind spots and increase driving risks. The ultimate goal of adjustment is to coordinate the three rearview mirrors to minimize the rear blind spot. A car has three rearview mirrors, namely the interior rearview mirror and the exterior rearview mirrors on both sides. The interior rearview mirror is mainly used to observe the situation of the vehicle behind, while the exterior rearview mirror is mainly used to observe the situation of the vehicle behind. Due to the different heights and observation angles that each of us is used to, the refracted images we see in the rearview mirror are also different. Therefore, before driving, you need to adjust the rearview mirror so that you can clearly observe the road conditions behind from the rearview mirror before you can go on the road. This is very important for driving.

First of all, when adjusting the interior rearview mirror, the most important point is to make the rear window glass fully present on the rearview mirror, so as to maximize the rear view and reduce the blind spot. After adjusting the interior rearview mirror, the horizon in the distance should be placed in the midline position, and the image of the right ear is just on the left edge of the mirror. When adjusting the exterior rearview mirror, we can press the left roller button on the steering wheel to choose whether to adjust the left or right rearview mirror. Then use the electric switch or manual adjustment to make the rearview mirror move up, down, left and right. When we adjust the left rearview mirror, we need to tilt our head toward the driver’s side glass (on the glass) until you can just see the rear of your car, so as to avoid repeated coverage of the range of the interior rearview mirror. After adjusting the left rearview mirror, the horizon should be placed in the midline position, the edge of the car body occupies 1/4 of the mirror image, and at the same time ensure that there is enough space on the side to observe other vehicles. When adjusting the right rearview mirror, we need to tilt our head to the right in the same way as the left side, until you can just see the rear of your car, so as to avoid repeated coverage of the range of the interior rearview mirror. After adjusting the right rearview mirror, the horizon should be placed at the 2/3 position, the edge of the car body should occupy 1/4 of the mirror image, and at the same time ensure that there is enough space on the side to observe other vehicles.

After the above adjustments, when a car passes you, you can see it in the rearview mirror first, and clearly know the road conditions behind, which can effectively improve driving safety. Of course, adjusting the rearview mirror does not mean that you can completely rely on it. During driving, we also need to pay attention to the changes in the surrounding environment at any time, whether there are other hidden obstacles or pedestrians, so as to ensure safe driving. In addition, before adjusting the rearview mirror, you should first adjust the position of the steering wheel and seat.

How do car fuel injectors work?

The engine fuel injector is a very important part of the engine. Its function is to spray fuel accurately according to the needs of the engine to achieve the best combustion effect. When the engine is started, the fuel pump pumps the fuel from the fuel tank, passes through the fuel filter and enters the injection channel of the fuel injector. At the entrance of the injection channel, the fuel is pushed by the high-pressure gas through the spray hole into the cylinder. In the cylinder, the fuel mixes with the high-temperature gas in the cylinder to form a combustible mixture. The size of the injection hole in the fuel injector can be adjusted as needed to control the amount of fuel injection to achieve the best combustion effect. In addition, the solenoid valve in the fuel injector can control the injection timing of the fuel according to the needs of the engine, making the fuel injection more accurate. Finally, the exhaust gas after combustion is discharged through the exhaust pipe and becomes the energy to drive the vehicle. The fuel injector plays a vital role in the engine, and its performance directly affects the performance and emissions of the engine.

What are the benefits of regular fuel injector cleaning?

After a long period of use, the problem of carbon deposits will gradually emerge. The reason for carbon deposits in the engine is very simple, that is, a kind of charred substance is produced under high temperature conditions by unsaturated olefins and colloids in the fuel. When this substance accumulates on the fuel injector, it will affect the fuel injector and cause the fuel injection to be poor, the injection angle, poor atomization, etc. In severe cases, it may even cause the fuel injector to be blocked, so it is very necessary to clean the fuel injector. The carbon deposit problem of the fuel injector will cause a serious drop in engine power, and when the fuel injector is cleaned, the engine power will be improved and restored to the best state. When the fuel injector is not spraying smoothly, the engine will shake significantly during operation, so when the fuel injector is cleaned, the engine shaking problem will be improved. After the fuel injector is cleaned, the problem of vehicle exhaust emission pollution can be improved.

What is the difference between an electronic thermostat and a mechanical thermostat?

The mechanical thermostat works on the principle of thermal expansion and contraction of paraffin, and controls the opening and closing of the thermostat by the temperature of the coolant. The center of the electronic thermostat is also filled with paraffin, but a heating device is installed inside the paraffin. This heating device is controlled by the electronic control unit ECU. The electronic control unit captures signals based on the engine water temperature sensor and the water temperature sensor on the radiator tank. When these signals reach the values set by the electronic control unit ECU, a heating instruction will be sent to control the heating of the heating device and the heating temperature can be accurately controlled. This is the implementation principle of the electronic thermostat. The electronic thermostat is more advanced than the mechanical thermostat. The main point is that the electronic control unit can dynamically control the heating of the heating device based on the sensor data of various sensors of the engine. That is to say, when the coolant has not reached the melting temperature of the paraffin, the electronic control unit can also control the melting of the paraffin in advance. This control is determined by the engine based on the sensor data of each sensor. The mechanical thermostat cannot achieve this effect. It can only start working after the coolant reaches a certain temperature. The above is the difference between mechanical and electronic thermostats.

How does the thermostat control the flow of coolant?

In the engine cooling system, the element that controls the flow of coolant is called a thermostat. The thermostat is a temperature-controlled valve that can automatically adjust the opening and closing of the valve according to the engine load and the temperature of the coolant to control the flow of the coolant to achieve large and small cycles. In layman’s terms, the thermostat is a three-way valve, one side of which is connected to the engine water outlet, one side is connected to the water inlet of the water pump, and one side is connected to the radiator. It can adjust the direction of the water flow according to the water temperature. When the water temperature is low, the coolant flows downward to achieve a small cycle; when the water temperature is high, the coolant flows upward to achieve a large cycle. It is usually installed in the engine water circuit to control the engine temperature. The engine mainly uses paraffin thermostats, which use the thermal expansion and contraction characteristics of paraffin to open and close the valve. Paraffin thermostats are divided into two categories: mechanical and electronic. Their implementation principles are the same, but the difference lies in the different trigger mechanisms of paraffin heating. First, let’s look at the mechanical thermostat. Let’s look at its components. It is a container, and the substance inside is paraffin. At low temperatures, paraffin becomes solid. Under the action of the spring, the thermostat valve closes the coolant channel between the engine and the radiator. The coolant returns to the engine through the water pump for a small cycle in the engine. At high temperatures, the paraffin melts and expands and gradually becomes liquid. The volume increases and compresses the rubber tube to shrink. While the rubber tube shrinks, it pushes the push rod upward. The push rod pushes the valve downward to open the valve. At this time, the coolant passes through the radiator to the thermostat valve and then circulates through the water pump to the engine for a large cycle. The main valve, return spring, base, lower bracket, bypass valve spring, bypass valve and other components form a whole and are sealed in the thermostat air shell. The base and lower bracket are fixed and play a fixing role. They cannot move during operation.

The linkage effect of the mechanical thermostat: The thermostat is held upward by the return spring and fixed to the base by the push rod passing through the piston. At low temperatures, the main valve and the base are sealed, and the bypass valve below and the wall of the sewer pipe are open. At this time, the coolant enters and exits to form a small cycle. When the temperature rises, the paraffin begins to melt and expand, and the piston will be pushed upward under the action of the expansion tension. Since the piston is fixed by the push rod and cannot move, the thermostat will be forced to move downward under the action of the reverse thrust. The thermostat moves downward under the action of the reverse thrust. At this time, the main valve is separated from the base, resulting in a certain opening, and the bypass valve below is combined with the wall of the sewer pipe to produce a certain degree of closeness. Since the water temperature at this time has not reached the peak value of the thermostat, the main valve above and the bypass valve below are not fully opened and closed, so the coolant will flow in two directions. At this time, the large and small cycles work at the same time. When the water temperature continues to rise and exceeds the thermostat peak, the main valve will be fully opened and the bypass valve below will be fully closed. At this time, all the coolant will flow through the main valve to the radiator and enter a full circulation mode. The above is the implementation principle of the mechanical paraffin thermostat.

How does the drum brake system brake by external force?

The automobile brake system is a safety guarantee for vehicle driving. Currently, the widely used ones are mainly disc systems and drum brake systems. Although the drum brake system is gradually withdrawing from the mainstream market, it is still used in some economical cars because of its low cost and stable braking effect. It is mainly used in the rear wheels with small braking loads and the hand brake when parking. A typical drum brake system is mainly composed of a back plate assembly, a brake drum, a wheel, and a wheel nut. First, let’s look at the brake drum and the back plate assembly. The brake drum is generally cast from iron, which has high strength, wear resistance and heat resistance. The brake drum is connected to the wheel. When braking, its inner wall rubs against the brake pad to generate huge friction resistance, and the brake drum is forced to slow down and stop rotating. The back plate assembly is composed of a combination of various parts, and each component plays its unique role. The back plate base is also cast from iron. It has many concave and convex grooves and various holes on it. Its function is to provide a solid chassis support for other components. The two semicircular arc parts are brake shoes, also called brake blocks. It is two steel frames fixed on the back plate base, and high-density friction material brake pads are attached to their outer walls.

Let’s look at the wheel cylinder. There is a hydraulic piston at each end of the wheel cylinder. When the brake pedal is pressed, the hydraulic system applies pressure to the wheel cylinder. Under the action of the hydraulic pressure, the two pistons are forced to push to both ends. The brake shoes on both sides will also open outward under the influence of the piston thrust. At this time, the brake pads on the outer wall of the brake shoes are attached to the brake drum and produce friction to form braking resistance, and the wheels are forced to slow down. Let’s look at the two pressure springs, which are responsible for fixing the brake shoes to the back plate. The fixed spring, when the brake pedal is released, the fixed spring can return the brake shoes to their original position, so that the braking force disappears and the wheels can turn again. Next is the automatic brake clearance adjuster, which is an automatic device. When the brake pads are worn, the gap between the brake pads and the brake drum will increase. This device can automatically adjust the gap between the brake pads and the inner wall of the brake drum so that they always maintain a standard distance. This can solve the problem that the brake pedal must be stepped on to the bottom to work after the brake pads are worn and thinned. Next, let’s take a look at the working principle of the clearance adjuster. The adjuster can be divided into three sections. The black part in the middle is a gear shaft. When it rotates one circle, the adjuster will automatically increase a little. Every time the brake is applied, the adjuster will be linked to self-adjust, so there is no need to manually adjust the excess clearance.

Finally, let’s look at the braking principle of the handbrake. The brake cable is connected from the back of the backplate base and is connected to the brake handbrake. When the handbrake is pulled, the brake cable pulls the brake rod. Under the influence of the fulcrum, the brake rod will push the left brake shoe to the left through the clearance adjuster to open it. At this time, the brake pad on the shoe fits with the inner wall of the brake to form resistance, thus successfully locking the brake drum and the wheel.

How does the car air conditioning system turn hot air into cool air?

The automobile air conditioning system is mainly composed of condenser, cooling fan, dryer, expansion valve, evaporator, blower, and compressor components.

How does a car’s air conditioning system work?

The working process of the automobile air conditioning system: The compressor is responsible for compressing the gas. It is driven by the engine crankshaft. When working, the gaseous refrigerant in the evaporator flows back into the compressor and becomes high-pressure steam after compression. The gaseous refrigerant flowing back from the evaporator will become high-temperature and high-pressure steam after compression. The refrigerant is always in gaseous state during this process. Next, the refrigerant flows to the condenser through the pipeline. The condenser is a heat converter. It is usually installed in front of the radiator water tank of the front of the car. The high-temperature and high-pressure gaseous refrigerant will condense into liquid after releasing heat through the condenser. The gaseous refrigerant enters through the pipe below the condenser and gradually flows upward. The gaseous refrigerant will absorb moisture through the dryer to improve the purity. At the same time, under the action of the cold wind coming in from the front of the car, the temperature drops rapidly and finally condenses into liquid and flows out from the pipe above the condenser. At this time, the refrigerant is in the form of high-pressure liquid. Then the high-pressure liquid refrigerant enters the expansion valve, which is a high-pressure valve. After the high-pressure liquid refrigerant is ejected through the expansion valve, it is converted into a low-pressure gas and pressed into the evaporator box. This is a pressure relief process. During the gasification conversion process, the high-pressure liquid will absorb the heat from the surrounding air, so the temperature of the air outside will become lower. At the same time, since the blower at the rear has been continuously pumping hot air into the car, a large amount of hot air will be absorbed when passing through the evaporator box, so there will be continuous cold air blowing into the car. At the same time, due to the absorption of heat from the air, the temperature of the refrigerant in the evaporator box will rise, and it will continue to flow to the compressor, and after being pressurized by the compressor, it will be pushed to the condenser again. This cycle repeats, and the temperature conversion work continues to cycle. The above is the working principle of the automotive air-conditioning system. Since the power of the compressor comes from the crankshaft of the engine, the fuel consumption of the automotive air-conditioning system will increase when it is working.

How does a disc brake system stop the wheels and stop the car?

The disc brake system is controlled by hydraulic pressure. Its working principle is to convert mechanical power into liquid pressure, and then the hydraulic pressure creates a huge friction force to slow down the wheel. The friction force is converted into heat energy, which is finally dissipated into the air. At present, hydraulic disc brake systems are widely used in family cars.

What are the components and functions of a disc brake system?

A typical disc brake system consists of the following components: wheel hub assembly, brake disc, brake caliper, wheel, and wheel nut. The wheel hub assembly is connected to the chassis of the car and also serves to fix the brake disc and other components. There is a bearing in the wheel hub assembly, which can control the wheel to make it rotate smoothly. The brake disc is an important component. It consists of two metal discs, one of which is equipped with a heat dissipation system. Because when braking, the friction between the brake pad and it will generate huge friction, and the huge friction will generate high temperature, especially on a long downhill. If the downhill speed is not controlled, the brake disc is easy to burn red. The heat dissipation system can accelerate air circulation and play a role in cooling and exhaust. The brake caliper is the main braking component. It can squeeze the brake pad through pressure so that the brake pad can stop the brake disc. It generally consists of a hydraulic piston, a bracket and a brake pad component. When we step on the pedal, the brake oil flows into the hydraulic piston in the brake caliper through the brake pipe under the pressure of the hydraulic brake system. The piston is squeezed out, and when the brake pedal is released, the piston returns to its original position. There is a sealing ring on the outside of the piston, which can prevent dust and dirt and protect the piston. Let’s look at the bracket component. It is generally installed on the car wheel hub to fix the brake pad and the caliper body. The piston assembly can be moved after the sliding pin is inserted. The brake pad is composed of four parts. The gasket reduces vibration and noise. The back plate is the rigid basis of the friction material. The interlayer between the back plate and the friction material plays a bonding role, which is responsible for bonding the friction material and the back plate together, and can also play a role in heat insulation. Finally, there is the friction material made of various compounds. It must have the characteristics of wear resistance, heat resistance, high strength and long life. The two brake pads are installed on the bracket and fixed by spring cuts. The brake pads are used very frequently and need to be replaced in time after wear, otherwise it will affect the braking performance.

How does a disc brake system work?

The working principle of the disc brake system: When the driver steps on the brake pedal, the mechanical force is converted into liquid pressure. The hydraulic pressure forces the brake oil to enter the piston assembly. The piston is pushed out to press the inner brake pad against the brake disc. Under the influence of friction, the brake disc begins to slow down. Since the inner brake pad can no longer move, no further pressure can be applied. When the hydraulic system continues to increase pressure, it will force the brake caliper body to move backward along the bearing. At this time, the outer brake pad begins to work. Under the joint action of the brake pads on both sides, the brake disc is stopped and the wheel stops rotating. When the brake pedal is released, the pressure is released and the piston returns to its original position.

How often do brake pads need to be replaced?

Brake pads generally need to be replaced after 3-5 km for front brake pads and 6-8 km for rear brake pads, but each car owner has different braking habits, so it depends on the actual wear and tear. Generally, the thickness of a new brake pad is about 1-1.5 cm. As the number of times increases, the thickness of the brake pad gradually becomes thinner, and the limit of use is 3 mm. If the thickness of the brake pad is only about 1/3 of the original thickness (about 0.5 cm), the brake pad needs to be replaced. When stepping on the brake, it is obvious that the brake is weak and soft. It is necessary to step on the brake deeply to achieve the previous braking effect. At this time, the braking distance becomes longer, which seriously affects driving safety and requires the replacement of brake pads.