In-depth analysis of the brake assembly in the

by:FUSAI     2020-05-28
?????Shandong Fuhua Axle Co., Ltd. has strict requirements on brakes in the production process, mainly from the following aspects: 1) Sufficient braking capacity The driving braking capacity is evaluated by the two indexes of braking deceleration and braking distance at a certain initial braking speed; slope. 2) Reliable operation The service brake has at least two independent lines for driving the brake. When one set of pipelines fails, the other set of intact pipelines should ensure that the braking capacity of the vehicle is not less than 30% of the specified value without failure. The service brake and the parking brake device may have a common brake, and the drive mechanism is independent. The service brake devices are all controlled by feet, and most of the other brake devices are manually operated. 3) At any speed braking, the car should not lose maneuverability and directional stability evaluation criteria related to directional stability. 4) Prevent water and sludge from entering the brake working surface. 5) The thermal stability of the braking capacity is required to be good. 6) The operation is light and has good followability. 7) The noise generated by the braking system is as small as possible during braking, and at the same time, it strives to reduce the emission of asbestos fibers and other substances that are harmful to the human body to reduce pollution. 8) The action hysteresis should be as short as possible. The action hysteresis refers to the braking reaction time, which is evaluated by the time required for the brake pedal to start to reach a given braking efficiency. The reaction time of air-brake vehicles is longer, and the requirement should not exceed 0.6s, and for trains should not exceed 0.8s. 9) The friction lining should have sufficient service life 10) After the friction pair is worn, there should be a mechanism that can eliminate the gap caused by wear, and the gap adjustment is easy to work, and an automatic gap adjustment mechanism should be set. 11) When any component of the brake driver device fails and its basic function is destroyed, the car brake system should be equipped with alarm devices such as audio or light signals. Prevents the wheels from being locked during braking, which is beneficial to improve the directional stability of the car during braking and the design of the front axle assembly of the light truck, shortening the braking distance, so in recent years, the brake anti-lock system (ABS) has been It has been rapidly developed and applied in automobiles. In addition, friction materials containing asbestos have been phased out due to the existence of asbestos carcinogenic hazards, and various non-asbestos-type materials have been successfully developed. There are several types of brakes including friction type, hydraulic type and electromagnetic type. Although electromagnetic brakes have the advantages of small lag, easy connection and reliable joints, they are only used as wheel brakes or reducers in some heavy vehicles due to their high cost. Hydraulic brakes are only used as retarders. At present, friction brakes are still widely used. Friction brakes are divided into three types: drum type, disc type and belt type according to the structure of friction pair. The belt type is only used as a central brake. ????The drum brakes used in the front axle assembly of the automobile produced by Fuhua Axle Co., Ltd. are divided into collar-shoe type, double-collar hoof type, bidirectional double-collar hoof type, double slave hoof type, unidirectional booster type, bidirectional booster There are several types. The main differences between different types of drum brakes are: ① The number and position of the fixed fulcrums of the shoe plates are different. ②The form and quantity of the opening device are different. ③ Is there any interaction between the two shoes during braking? Due to the different fixed fulcrum and opening force position of the shoe, the number of collars and slave shoes of different types of drum brakes are different, and the braking efficiency is different. ????The determination of the main parameters of the brake is mainly in the following aspects: 1) Brake drum inner diameter D: When the input force F0 is constant, the larger the brake drum inner diameter, the greater the braking torque and the stronger the heat dissipation capability. However, increasing D is limited by the inner diameter of the rim. There should be enough clearance between the brake drum and the rim. It is usually required to change the gap to not less than 20mm. Otherwise, not only will the brake drum heat dissipation conditions be too bad, but the rim may stick to the inner tube or burn the valve when heated. The brake drum should have sufficient wall thickness to ensure a greater rigidity and thermal capacity to reduce the temperature rise during braking. The diameter of the brake drum is small, the rigidity is large, and it is beneficial to ensure the processing accuracy of the brake drum. The range of the ratio of the brake drum diameter to the rim diameter D / Dr is as follows: Car: D / Dr = 0.64 ~ 0.74 Freight car: D / Dr = 0.70 ~ 0.83 The inner diameter of the brake drum is 382mm according to the above standards. ?2) Wiper lining width b and wrap angle: The choice of friction lining width b has an impact on the service life of the friction lining. If the width of the lining is narrower, the wear speed block and the life of the lining are shorter; if the width of the lining is wider, the quality is large, it is not easy to process, and the cost is increased. The width b of the friction plate is 67mm. After the brake drum radius R is determined, the friction area of ??the lining is Ap = R? B. The greater the total friction area ∑Ap of the brake shoe linings, the smaller the unit's positive pressure and energy load during braking, and the better the wear characteristics. The radius R of the friction plate is 340mm.
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