Graduation Design (Dissertation) of Wuhan University of Technology

Automobile Wiper Design and Its Aerodynamic lift Analysis

School: School of International Education

Specialty＆Class: Automobile Engineering gj1304

Student name: Yan Chao

Tutor: Wang Yiping

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Abstract

This paper describes a design process for the front windshield wiper of a sedan, including the design and calculation of the motor selection, deceleration mechanism, four-bar mechanism and actuator, and the kinematics simulation of the four-bar mechanism. Out of the motion parameter graphics. And the aerodynamic simulation of the two popular wiper blades combined with the automobile body was carried out to obtain the aerodynamic lift and the contrast between the different scraping angles.

The paper mainly studies the floating problem of automobile wiper at high speed.

The main results show that the boneless blade wiper has a positive lift force when the scraping angle is less than 45 °, and the spoiler is obvious. After 45 °, the interaction with the airflow is weakened and the negative lift is generated.

Keywords: Wiper, Mechanical Design, Motion Simulation, Aerodynamic Uplift, Vehicle Aerodynamics

Contents

Abstract III

Chapter 1 Introduction 1

1.1 Background and significance of course selection 1

1.2 Research Status 2

1.3 Major Method and Content of the Research 2

Chapter 2 wiper design calculations 3

2.1 wiper design requirements 3

2.1.1 scraping area 3

2.1.2 Scratch frequency 4

2.1.3 Speed requirements 4

2.1.4 Other requirements 4

2.2 The overall location of the wiper 4

2.2.1 Body parameters 4

2.2.2 The layout of the wiper 4

2.4.1 Select material 7

2.4.2 Parameter Design 7

2.4.3 Strength Verification 9

2.5 four-bar mechanism design 11

2.6 Actuator design 13

2.6.1 selection of scraping tape 13

2.6.2 design with bone wiper bracket 13

2.6.3 design without bone wiper stent 14

2.6.4 Design of wiper arm 15

2.6.5 Design of wiper arm spring 16

2.6.6 Selection of rivets 18

2.7 Wiper Assembly 18

Chapter 3 Wiper mechanical movement simulation 20

3.1 Mathematical model of four - bar mechanism 20

3.2 motion simulation results 21

Chapter4 Aerodynamics Numerical Simulation Theory 23

4.1 Basic Theory of Automotive Aerodynamics 23

4.2 Calculate the basic theory of fluid mechanics 25

4.2.1 Control equations for fluid mechanics 25

4.2.2 Discretization of Computational Domains and Control Equations 25

4.2.3 Turbulence model 26

Chapter 5 Wiper Aerodynamic Analysis 28

5.1 Analysis of Aerodynamic Lifting of Boneless Wiper 28

5.1.1 Model description 28

5.1.2 Discretization of Computational Domains (Grid Generation) 28

5.1.3 Discrete control equations 29

5.1.4 Turbulence model 29

5.1.5 Boundary conditions and solution settings 29

5.1.6 Calculation results and post-processing 30

Chapter 6 Summary and Prospect 33

Acknowledgments 34

Reference 35

Appendix 37

Chapter 1 Introduction

1.1 Background and significance of course selection

With the continuous development of China's auto industry, the national car ownership rising, car driving safety has become considered an increasingly important aspect. Although China's annual traffic accidents are decreasing year by year, it is still one of the countries with the largest number of traffic accidents in the world. One of the bad weather is the cause of traffic accidents can not be ignored. 38% of the traffic accidents occurred in the rain, and with the greater rainfall, the accident rate continues to rise, when the rainfall reached heavy rain (24 hours rainfall of 18 mm to 38 mm), the accident rate reached its peak. In the case of heavy weather, especially heavy rain, due to the rain wind attached to the windshield, the light intensity of the outside is weakened, the vision becomes blurred, and the influence of the external environment on the human spirit, the environmental judgment and the reaction ability are diminished. At this time it must be continuously ensured that the driver in the car have enough vision.

The task of the front windshield wiper system is to remove the water, snow, dirt (mineral, organic, biological) on the windshield. In accordance with the standards proposed by GB15085-2013, the windshield wiper cover should cover at least 80% of the relevant area. Since it was invented th structure of it had little change, in general, for the motor-driven crank rocker arm mechanism, double blade wiper also has a connecting rod. The typical wiper structure consists of a turbine-driven motor, a control stick, a wiper system, a wiper arm and a wiper blade. A wide range of wipers, according to the activities of the blade, can be divided into parallel, opposite and cross types. According to the shape of the blade can be divided into conventional blade (with bone) and aero-type blade (without bone). In recent years, some improved design, with the introduction of a stretchable wiper, so extend wiping area close to 100%.