CN201410943Y - Brake system temperature automatic control device - Google Patents

Abstract

The utility model discloses an automatic temperature control device for a brake system, which includes a temperature detection unit, a liquid level detection unit, a man-machine interface unit and a microcomputer control unit, wherein the input end of the temperature detection unit is connected to the output end of the brake system, and the temperature detection unit is connected to the output end of the brake system. The output terminal of the unit is connected to the input terminal of the microcomputer control unit, and the microcomputer control unit is bidirectionally connected to the man-machine interface unit. The output terminal of the microcomputer control unit is connected to the input terminal of each water cooling system of the vehicle, and the output terminal of the water cooling system is connected in series The detection unit is connected with the input terminal of the microcomputer control unit. The utility model improves the service life of the braking system, and at the same time enhances the driving safety of the vehicle.

Description

Brake system temperature automatic control device

technical field

The utility model relates to a brake system temperature automatic control device, which belongs to the technical field of temperature measurement and control of the vehicle brake system.

Background technique

The car brake system is an extremely important part of the vehicle. As we all know, the braking system of modern automobiles adopts the friction braking method, and the required braking force is generated by the mutual friction between the working parts. Therefore, in the braking system, the stability of the friction coefficient of the working parts directly affects the stability of the braking system and the safety of the vehicle.

Due to the friction braking method, during the entire braking process, the mechanical energy of the vehicle will be converted into heat energy and released, causing the temperature of the braking system to rise, resulting in thermal fading. The so-called "thermal decay phenomenon" here refers to a phenomenon in which the friction coefficient of working parts decreases when the initial braking speed is high, the pressure increases, and the braking frequency increases, resulting in the temperature of the braking system rising. For this reason, the braking performance of the vehicle will be significantly reduced or even lost, resulting in safety accidents. At the same time, too high temperature can easily cause oxidation of the working parts of the brake system, accelerate the loss of parts, and reduce the service life of the brake system. This type of problem is particularly noticeable when the vehicle is traveling through continuous downhill sections or on poor roads for extended periods of time.

At present, a lot of research work has been done at home and abroad on how to solve the thermal recession of the vehicle brake system, increase the service life of the brake system, and improve the driving safety of the vehicle, and some practical solutions have been proposed. However, most of these solutions start with the material composition and structural arrangement of the brakes to improve the brake system, rather than solving the safety problems caused by the thermal recession phenomenon by properly controlling the temperature of the vehicle brake system.

For example, in terms of the materials of the working parts of the brake system, for powder metallurgy brake pads, the liquefaction of the low-melting-point metal contained in the material in a high-temperature environment is the key to the phenomenon of thermal decay in such working parts. Therefore, As long as the content of low-melting point metals is well controlled, or replaced by other non-metallic elements, powder metallurgy materials can be guaranteed to have sufficient mechanical strength and good thermal recession resistance. For resin brake pads, as long as the heat resistance of the resin material is improved, its thermal decomposition temperature can be increased, and the decomposition and oxidation rate can be delayed. In this way, the brake pads can have stable friction performance in high temperature environments. The use of various modified phenolic resins can greatly increase the decomposition temperature of the resin.

For the structural improvement of the braking system, it is typical to add a retarder to the vehicle. As an auxiliary braking component of the vehicle, the retarder is called the "fourth brake". It was first used to solve the problem of short-distance braking and deceleration of trains. Later, Western European countries promoted it and applied it to heavy trucks and large and medium-sized passenger cars driving on highways and mountainous areas to improve the braking effect of vehicles. At present, retarders are widely used in developed countries. The main advantages of this equipment are: 1) Effectively improve the safety of vehicle driving and reduce the generation of brake heat fading, 2) Improve the economy of vehicle operation (prolong the service life of brake system parts and reduce maintenance costs), 3) Reduce the labor intensity of the driver and improve the comfort of the vehicle. At present, all kinds of retarders can be divided into electric eddy current type, hydraulic type, permanent magnet type, engine retarder type and electric motor type according to their working principles. The latter is only used for electric vehicles and electric transmission vehicles.

Although many methods that can effectively alleviate the thermal degradation of the vehicle brake system, improve vehicle driving safety, and prolong the service life of the brake system have been proposed, and related hardware equipment has also been put into actual production and application. At the same time, my country has also issued GB7258 and GB12676 standards to regulate the braking devices of various passenger cars and trucks to improve the safety of vehicles. But in real life, the hardware equipment used to solve this kind of problem is often expensive, and the operating cost will increase after the vehicle is installed. Moreover, due to some problems of the vehicle itself, for the installation of this type of equipment, it is also necessary to install the equipment in the vehicle other equipment for replacement. Therefore, the actual configuration of this type of equipment is not very ideal. In addition, because many of these devices only increase the conditions required for the occurrence of thermal recession, delay the occurrence time, or provide certain auxiliary safety protection measures when thermal recession occurs. However, it did not choose to control the temperature of the brake system to fundamentally eliminate the safety hazard caused by the phenomenon of thermal recession. Therefore, even if equipped with hardware devices such as retarders, it is sometimes impossible to well overcome the potential safety hazard caused by the phenomenon of thermal decay.

The most direct, effective and cheap solution to the hidden dangers of vehicle driving safety caused by thermal fading should be realized by temperature control of the brake system.

At present, although many drivers will cool down the brake system while the vehicle is running, and control the temperature of the brake system to eliminate the potential safety hazards caused by thermal recession as much as possible, but due to the lack of necessary hardware equipment, the process It can only be done manually. Drivers often need to stop the vehicle after driving for a certain distance according to their own practical experience, and reduce the temperature of the brake system by natural cooling or water cooling. Such an approach can alleviate the overheating of the brake system to a certain extent, but due to the lack of real-time temperature monitoring of the brake system, the driver often cannot obtain an accurate parking time only by virtue of personal experience. If there is too little parking, the brake system will still have the problem of overheating, which will cause safety hazards; if there are too many parking, it will not only affect the work efficiency, increase fuel consumption, but also increase the driver's work intensity. Simultaneously, the driver may also forget to cool down the braking system of the vehicle due to personal negligence.

Utility model content

The purpose of the utility model is to provide an automatic temperature control device for a braking system aiming at the defects in the prior art.

For realizing the above object, the utility model adopts the following technical solutions:

The utility model brake system temperature automatic control device is characterized in that it includes a temperature detection unit, a liquid level detection unit, a man-machine interface unit and a microcomputer control unit, wherein the input end of the temperature detection unit is connected to the output end of the brake system, and the temperature detection unit The output terminal of the microcomputer control unit is connected to the input terminal of the microcomputer control unit, and the microcomputer control unit is bidirectionally connected with the man-machine interface unit. The output terminal of the microcomputer control unit is connected to the input terminal of each water cooling system of the vehicle, and the output terminal of the water cooling system is connected in series The unit is connected to the input end of the microcomputer control unit.

The utility model adopts a temperature sensor to detect the real-time temperature of the brake system of the automobile, and a microcomputer generates corresponding control output according to the detected temperature signal to control the temperature of the brake system. When the temperature of the brake system is too high, it can automatically realize the cooling function. The utility model can not only improve the service life of the brake system, but also enhance the safety of the vehicle running, and has certain use value and application prospect.

Description of drawings

Figure 1: Structural schematic diagram of the utility model.

Figure 2: Circuit diagram of temperature sensor parasitic power supply.

Figure 3: External power supply circuit diagram.

Figure 4: Installation position diagram of the proximity switch measuring head.

Figure 5: Key input circuit diagram.

Figure 6: Showing the circuit diagram.

Figure 7: Voltage regulator circuit diagram.

Figure 8: Basic circuit diagram of a microcomputer.

Figure 9: The overall circuit diagram of the microcomputer control unit.

Detailed ways

Below in conjunction with accompanying drawing, the technical scheme of utility model is described in detail:

As shown in Figure 1, the brake system temperature automatic control device is characterized in that it includes a temperature detection unit, a liquid level detection unit, a man-machine interface unit and a microcomputer control unit, wherein the input end of the temperature detection unit is connected to the output end of the brake system, The output terminal of the temperature detection unit is connected to the input terminal of the microcomputer control unit, and the microcomputer control unit is bidirectionally connected with the man-machine interface unit. The liquid level detection unit is connected to the input end of the microcomputer control unit. It mainly includes four parts: temperature detection unit, liquid level detection unit, man-machine interface unit, and microcomputer control unit. The utility model utilizes a 12V automobile power supply, and supplies power after the voltage is stabilized to 5V by the LM7805 chip. The system supports multi-point measurement of temperature, and detects the temperature of the brake system every second. When the temperature exceeds the set limit value, the microcomputer sends a control signal to cool down the brake system by spraying water. At the same time, the utility model also provides a simple water tank liquid level detection function. When the water tank is short of water, the system turns off the automatic cooling function and sends out an alarm. The system is flexible and convenient in actual use, and the temperature sensor supports plug-and-play without complex initialization. At the same time, the system also provides a basic man-machine interface unit, through which the user can set the temperature limit value to achieve different temperature control effects. At the same time, through the LED digital tube, the measured temperature value can be observed in real time.

The selection of temperature detection components is an extremely important link for designing accurate and efficient temperature detection components. In the past, we often used thermal resistance or thermocouple as the basic component of measurement, and converted the temperature signal into a current or voltage signal through an analog circuit, and then used A/D conversion to convert the analog signal into a digital signal, and input it into a microcomputer for measurement. control. Designing the temperature detection unit in this way, although the basic temperature measurement function can also be realized, the hardware circuit is complicated, takes up more ports, and the system reliability is not high. Improper handling of any circuit link may greatly reduce the accuracy of temperature measurement, thereby affecting the control performance of the entire temperature control system.

For this reason, in this utility model, adopt the digital temperature sensor DS18B20 that American Dallas semiconductor company introduces as temperature sensing element.

As shown in Figure 2, the hardware circuit design of the sensor can use the parasitic power supply circuit shown in Figure 2. In this circuit, the power transmission and data transmission of the sensor are realized through the data line. In order to provide enough current in the effective sensor clock cycle to ensure the normal operation of the sensor, it is necessary to add a MOSFET for control. When the sensor performs temperature conversion, the microcomputer sends a control signal to the MOSFET, and the data line is forcibly pulled up to meet the power supply requirement ^[16] .

In addition to the parasitic power supply circuit, an external power supply circuit as shown in Figure 3 can also be used. In this circuit, the data line of the temperature sensor is only used for data transmission, and the power required for its operation is provided by the external power supply connected to the power pin.

Comparing the above two circuits, the advantages of the parasitic power supply circuit are: 1) no local power supply is required for remote temperature detection, and 2) the sensor can still work normally when there is no external power supply. However, in order to realize these advantages, it needs to occupy more mouth lines, and the control is complicated. In this design, considering that the temperature measurement distance is not far away and there is a reliable external power supply, in order to improve the reliability of the system and reduce the design difficulty, the external power supply circuit is selected as the sensor hardware circuit.

As shown in Figure 4, the liquid level detection unit is designed to automatically start the cooling function to spray water on the brake system to cool down. Therefore, it is necessary to monitor the liquid level of the water tank to prevent cooling failure due to lack of water in the water tank. Since there is no need to know the specific liquid level here, as long as an alarm is generated when the water tank is short of water, the proximity switch can be used as the basic detection element.

Since the measured object is water in this unit, after comprehensive consideration of the measurement effect and cost, a capacitive normally open proximity switch is selected as the detection element. The so-called capacitive proximity switch is mainly made of the influence of the measured object on the dielectric constant. In the actual detection, the measuring head of the capacitive proximity switch and the measured object constitute the bipolar plates of the capacitance. When the measured object moves, the dielectric constant changes, causing the capacitance value to change. This change can control the opening and closing of the switch.

According to the above description, the measuring head of the proximity switch can be installed at the bottom of the water tank, as shown in Figure 8. When there is water in the water tank, the proximity switch is closed and outputs a corresponding signal; otherwise, the switch is disconnected and no signal is output. Appropriate level conversion is done on the output signal to generate the liquid level detection signal. When the water tank is short of water, the liquid level detection signal is a high-level signal, otherwise, it is a low-level signal. The microcomputer can detect the liquid level of the water tank through this signal.

As shown in Figure 5, in order to enhance the flexibility of temperature control, so that users can adjust the temperature control effect according to the actual environment, and also to allow users to observe the temperature measurement value in real time, a human-machine interface unit is added. The unit mainly realizes two functions of key input and display output.

For the button input part, three normally open buttons are used as input devices, through which functions such as temperature limit value setting and buzzer switch are realized. The specific functions corresponding to each button are listed in Table 1. Each key is connected to a pin of the microcomputer. When the button is pressed, the circuit is connected, and the signal input terminal generates a low level input to the microcomputer. On the contrary, the circuit is disconnected and the input signal becomes high level. The microcomputer detects the corresponding port signal, and executes the corresponding function if a low-level signal is detected.

Table 1 Button Function Table

As shown in Figure 6, for the display output part, a 4-bit common anode LED digital tube is used to realize the temperature display function. The 2 to 4 digits of the digital tube are used to display the maximum temperature value measured by each temperature sensor at the same time, and the first digit displays the number of the sensor that measured the temperature value. In the display circuit, the microcomputer sends 7-segment display codes to the digital tube through the pins a to g to control the displayed value. At the same time, through the LEDEN1 to LEDEN4 ports, the display bit enable control signal is sent to the digital tube. In the actual display process, the circular scanning method is used to enable each display bit in turn. When a certain bit is enabled, send the 7-segment code corresponding to the displayed value of the bit to the digital tube. When the cyclic scanning period is properly adjusted, the phenomenon of persistence of vision of the human eye can be used to produce a phenomenon in which each display bit displays a corresponding value at the same time. Utilizing this point, the desired display function can be realized.

AT89C51 single-chip microcomputer, as the hardware core part of this design, is closely connected with the above-mentioned hardware units. The control of each hardware unit is realized through a microcomputer. The hardware circuit design of this part is as follows.

As shown in Figure 7, in order for the microcomputer to work normally, it must first provide a 5V DC regulated power supply, and the power supply voltage of the car is 12V. If the microcomputer is directly powered, the chip will be burned. Therefore, the LM7805 voltage regulator chip is used to step down the car power supply, adjust the voltage to 5V, and then supply power to the microcomputer.

As shown in FIG. 8, configure the basic working circuit of the microcomputer, as shown in FIG. 12 specifically. This part of the configuration is divided into three steps, the first is the oscillation circuit setting. The oscillating circuit is used to generate the clock signal required for the operation of the microcontroller. After comprehensively considering system performance requirements and cost and other factors, a 12MHz crystal oscillator and a 30pf capacitor are selected to form an oscillation circuit. Through this circuit, the operating frequency of the microcomputer can reach 12MHz. After the first step of the configuration is completed, the reset circuit of the microcomputer needs to be set. In this design, a 10uf electrolytic capacitor and an 8.2k resistor are used to form an automatic power-on reset circuit ^[27] . When the system is powered on, the microcomputer automatically resets Reset correctly. At the end of the configuration, it is also necessary to ensure that the No. 31 pin of the microcomputer maintains a high level, otherwise, the microcomputer will not be able to execute the program in the on-chip program memory.

After the basic circuit configuration of the microcomputer is completed, each hardware unit needs to be connected with the microcomputer to be controlled. At the same time, a corresponding indicator light needs to be added to facilitate the use of the user. The circuit design of this part is shown in Figure 9.

In the figure, the data lines of the four temperature sensors are respectively connected to pins 32 to 35 of the microcomputer for information interaction operation. At the same time, on pins 21 to 24 of the microcomputer, each temperature sensor Configure a corresponding indicator light. When the sensor works normally and the measured temperature is lower than the limit value, the indicator light is normally on; when the temperature exceeds the standard, the indicator light flashes to prompt. For the two liquid level sensors, connect them to pins 8 and 13 of the microcomputer, and make the indicator lights on pins 36 and 37 correspond to them. When there is water in the water tank and the sensor is working normally, the indicator light is on; if the water tank is short of water, the indicator light also flashes to prompt. For the connection between the microcomputer and the human-machine interface unit, it is necessary to focus on the selection of the SET button connection pin. Considering that in practical applications, the operation frequency of entering the setting state and switching the buzzer is relatively low. If the system is in the temperature measurement and control state, the regular scanning method is used to determine whether the SET button is pressed, which will consume a lot of system resources. , resulting in unnecessary waste. Therefore, connect the SET key with the No. 12 pin of the microcomputer, and respond to it through an external interrupt. In this circuit, a buzzer is also configured for the system. When the water tank is short of water or the temperature of the brake system exceeds the standard for a long time, it will prompt an alarm. Finally, the microcomputer generates corresponding control signals according to the values collected by each sensor, and outputs them externally through pins 38 and 39. So far, the design of each hardware unit of the system has been completed.

Claims (4)

1. An automatic temperature control device for a brake system, characterized in that it includes a temperature detection unit, a liquid level detection unit, a man-machine interface unit and a microcomputer control unit, wherein the input end of the temperature detection unit is connected to the output end of the brake system, and the temperature detection unit The output terminal of the unit is connected to the input terminal of the microcomputer control unit, and the microcomputer control unit is bidirectionally connected to the man-machine interface unit. The output terminal of the microcomputer control unit is connected to the input terminal of each water cooling system of the vehicle, and the output terminal of the water cooling system is connected in series The detection unit is connected with the input terminal of the microcomputer control unit. 2. The automatic temperature control device for the brake system according to claim 1, wherein the temperature detection unit adopts an external power supply circuit. 3. The brake system temperature automatic control device according to claim 1 or 2, characterized in that the man-machine interface unit includes a key input circuit and a display output circuit, wherein the key input circuit is connected to the input terminal of the microcomputer control unit, and the display The output circuit is connected to the output end of the microcomputer control unit. 4. The automatic temperature control device for the brake system according to claim 1 or 2, characterized in that the temperature detection unit adopts a digital temperature sensor with a model number of DS18B20.

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