STUDY ON VEHICLE PULL CHARACTERISTICS ACCORDING TO TIRE TREAD PATTERN

International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 5, May 2018, pp. 891 896, Article ID: IJMET_09_05_098 Available online at http://www.iaeme.com/ijmet/issues.asp?jtype=ijmet&vtype=9&itype=5 ISSN Print: 0976-6340 and ISSN Online: 0976-6359 IAEME Publication Scopus Indexed STUDY ON VEHICLE PULL CHARACTERISTICS ACCORDING TO TIRE TREAD PATTERN NamWoong Kim and Bongsoo Kim Vehicle Test Team, R&D Center, NEXEN TIRE, 201 Gukgasandanseo-ro, Guji-myeon, Dalseong-gun, Daegu, South Korea 43011 HaengMuk Cho* Division of Mechanical and Automotive Engineering, Kongju National University 1223-24, Cheonan Daero, Seobuk-gu, Cheonan-si, Chungcheongnam-do 331-717, South Korea * ABSTRACT For this thesis, research on vehicle pull at the time of acceleration in accordance with the tire tread pattern changes was conducted. NP tire was used for more diversified tread pattern changes and tires were produced with tread block angle, kerf position and stiffness as the variables. In addition, 3 vehicles with different driving format and output were used to confirm the correlation of pulling phenomenon in accordance with vehicle changes. GPS equipment was used to quantitatively measure the extent of vehicle pull and dynamic foot-print measurement equipment was used to measure the force acting on contact patch in the transverse direction of the tire and road surface. As the results of the research, the factor that imparted the greatest effect on the vehicle pull was found to the tread block angle, with kerf and stiffness imparting effect on vehicle pull to certain extent. Vehicle pull occurred irrespective of the driving format of the vehicle and it was confirmed that there was no effect of torque steer, which was of concern at the initial stage of the research. Keywords: Vehicle Pull, Dynamic Foot-print, Tread Block Stiffness, Tread Block Angle, Tread Block Kerf, Torque Steer Cite this Article: NamWoong Kim, Bongsoo Kim and HaengMuk Cho, Study on Vehicle Pull Characteristics According to Tire Tread Pattern, International Journal of Mechanical Engineering and Technology, 9(5), 2018, pp. 891 896. http://www.iaeme.com/ijmet/issues.asp?jtype=ijmet&vtype=9&itype=5 1. INTRODUCTION Due to the recent trend of downsizing and advancement of hybrid technologies in the automobile industry, it has become easier for ordinary drivers to have access to high-output and high-torque vehicles. Although more pleasing and efficient driving has become possible due to the increase in output and torque of the engines, it is not particularly welcome news for tire that needs to ultimately deliver driving/braking force to the road surface it is not in http://www.iaeme.com/ijmet/index.asp 891 editor@iaeme.com

Study on Vehicle Pull Characteristics According to Tire Tread Pattern contact with. This is because the stress that tire needs to bear increases with increase in output and torque. Moreover, phenomenon of vehicle pull at the time of acceleration that did not manifest in the past occurs frequently. As such, manufacturers are focusing their efforts in coming up fundamental means of coping with and reducing such phenomenon. Therefore, this thesis will concentrate on examination of the phenomenon of vehicle pull at the time of acceleration of the vehicle. 2. EXPERIMENT 2.1. Vehicle Pull Vehicle pull refers to the phenomenon in which the vehicle tends to deviate to left or right without the manipulation of steering handle or other disturbance while driving. When vehicle pull occurs, the driver needs to maintain prescribed level of steering input in the opposite direction of the pull, which increases the fatigue experienced by the driver. In addition, severe vehicle pull can induce safety problem. Accordingly, evaluation of vehicle pull has become an important factor at the time of the evaluation of the performances of tire or vehicle. There are 4 major causes of vehicle pull including vehicle, tire, road surface and external environment. Although it would be appropriate to pursue research the extent of the pulling effects comprehensively by detailed factors of each cause for each of their levels, it is difficult due to the efficiency issues of the research. Therefore, for this thesis, research on the extent of the effects of tire patterns on the vehicle pull at the time of acceleration was executed first. Table 1 Factors of vehicle pull Vehicle Tire Road Other Cross Caster Cross Camber Cross Scrub Torque Steer Crown Shape Plane Bending Conicity Construction Plysteer Pattern Crown Speed Load Pressure Wear SW Friction Wind 2.2. Equipment Equipment used in this research can be divided largely into 2 types. First, VBOX 3i of Race Logic was used for quantitative measurement of vehicle pull. It is widely used GPS-based measurement equipment mostly by vehicle related companies. With simple and easy installation, it can compute the distance of transverse direction shift over prescribed sector with the Heading value at the time of departure of vehicle as the reference by using GPS data. Second, dynamic foot-print measurement equipment of A&D was used to measure the 3- axis forces and distribution of these forces acting on the contact patch of the tire at the time of vehicle pull. This equipment is installed on the road surface that the actual vehicle is driven on and data is acquired as though scanning the tire by using 3 small component force sensors (7.5mm x 7.5mm / Fx, Fy and Fz). Since it is installed on the actual road surface, it is able to analyze the characteristic of dynamic foot-print under a diverse range of driving conditions to which the geometry of the vehicle has been reflected. In addition, it is possible to materialize the desired friction coefficient of the road surface through roughness processing of the dimples and plates of the sensors. [1] [2] http://www.iaeme.com/ijmet/index.asp 892 editor@iaeme.com

NamWoong Kim, Bongsoo Kim and HaengMuk Cho 2.3. Test Vehicle and Tire Information on vehicles and tires used in this research are given in the Tables 2 & 3 below. 3 units of vehicles in the same segment but with different driving format and output, and 6 tires with different pattern block configurations were used. Information on angles of the tire blocks are given in the Figure 1. All the variables other than the pattern block configuration including the structure and compound used for the tires are the same. Table 2 Factors of vehicle pull Group Engine HP/Torque Lay out A B C 3,778cc 3,778cc 5,038cc 315hp / 40.5kg.m 311hp / 40.5kg.m 425hp / 53.0kg.m AWD RWD RWD Table 3 Information on tires evaluated Group Angle 1 Angle 2 Angle 3 Angle 4 A 9 43.1 26.6 50.8 B A Group angle + in/out rib kerf C 4.5 21.6 13.3 25.4 D C Group angle + in/out rib kerf E 4.5 21.6 26.6 50.8 F 9 43.1 13.3 25.4 Figure 1 Shows the photograph of the experimental setup 2.4. Test Vehicle and Tire All evaluations were executed through highly skilled driver in preparation for the improvement of repetitive reproducibility and safety accident of the test. Tests were conducted by categorizing the evaluations largely into evaluation of the extent of effect of torque steer of the vehicle and evaluation of the extent of effect of pulling in accordance with the pattern. The following final test conditions are set through preliminary evaluation. Table 4 Evaluation condition Group Gear Start RPM Gas Pedal Torque Steer Acceleration 1 st / 2 nd 3000 WOT (Wide open throttle) http://www.iaeme.com/ijmet/index.asp 893 editor@iaeme.com

Study on Vehicle Pull Characteristics According to Tire Tread Pattern 3. RESULT 3.1. Result of verification of torque steer Torque steer refers to the phenomenon in which vehicle pull occurs due to the generation of left/right deviation of the secondary moment due to the difference in the angle/length of drive shaft on the right and right or other reasons. Test on measurement of the driving force on the left and the right was executed in order to assess the extent of effect of torque steer in RWD vehicle prior to the execution of the main test. The results are illustrated in the Figure 2. Evaluation was executed 5 times for each vehicle and average values of the findings were used. [2] Figure 2 Longitudinal force deviation Longitudinal force was computed by applying integral calculus on Force X graph generated on the contact patch. As the results of evaluation, it was found that there is no deviation in driving force between the left and right of the Vehicle A. Deviation in the Vehicles B and C was at about 3% level of the total longitudinal force generated, which is a level that can be ignored. Quantity of shift in the transverse direction of the actual vehicle was also within the prescribed value. As the result, it is determined that there is no effect of torque steer of the RWD vehicles used in the evaluation. 3.2. Results of Evaluation of the Extent of Effect on Pulling for each Pattern Acceleration test and evaluation of the extent of effects on vehicle for each of the tires were executed. Evaluation was executed 5 times for each condition and average value of the findings was used. The results of test on Vehicle B are given in Figure 3. If vehicle pull occurs, there also is occurrence of deviation of lateral force between the left and the right generated on the contact patch of the tire. In addition, it was possible to confirm that the vehicle pull increases with increase in this deviation. V1 V2 V3 V4 V5 V6 Tire Force Dv. 625 673 429 652 124 338 Figure 3 Tire information & lateral force deviation In the cases of V1, V2, V3 and V4, it was possible to confirm that the pattern angles are the same and results in accordance with the presence of kerf. When kerf is situated at In-Out Side, slightly more pull occurred. Moreover, in the case of V5 and V6, it was possible to confirm the difference in pull according to the angle of In-Out Side pattern, and, in the case of V1 and V3, difference in pull according to the pattern angle. http://www.iaeme.com/ijmet/index.asp 894 editor@iaeme.com

NamWoong Kim, Bongsoo Kim and HaengMuk Cho Characteristics of dynamic foot-print of lateral force of V1 are illustrated in Figure 4. It was confirmed that greater deviation occurred in the trailing side than the leading side, and same phenomenon was confirmed in all versions. Figure 4 Lateral force distribution. Left tire (L) Right tire (R) Although the same results were obtained from the Vehicle A (AWD), there was less occurrence of pull phenomenon given the characteristics of the vehicle. Greater pull phenomenon occurred in the Vehicle C (RWD). It was demonstrated that pull at the time of acceleration due to PTN is related to the size of driving force and driving characteristics. 3.3. Performance of Single Tire Changes in Residual Cornering Force values of the single tire according to the pattern changes are illustrated in Figure 5 below. RCF is one of the important factors in vehicle pull and all tires fundamentally have RCF value in accordance with their corresponding structure. It was confirmed that RCF values can be changed sufficiently by means of altering the pattern characteristics. Figure 5 Changes in RCF performances in accordance with pattern changes In addition, changes in the direction of lateral force occurred according to the input direction of longitudinal force, and it was confirmed that the directions of pull at the time of acceleration and braking were opposite at the time of evaluation of actual vehicle. 4. CONCLUSIONS For this thesis, research on vehicle pull at the time of acceleration in accordance with the changes in tire tread pattern was carried out and the following conclusions were arrived at. http://www.iaeme.com/ijmet/index.asp 895 editor@iaeme.com

Study on Vehicle Pull Characteristics According to Tire Tread Pattern First, vehicle pull at the time of acceleration can be generated due to tire with the tire block angle making the greatest contribution in such generation. Generation mechanism: Pattern moment occurs according to the changes in pattern characteristics, which in turn induces changes in RCF of sing tire and generates vehicle pull. Key factors can be defined in the order of angle, distance and stiffness of pattern block. Second, changes in the direction of lateral force occur according to the direction of longitudinal force, which will in turn determine the direction of vehicle pull. If right pull occurs at the time of vehicle acceleration, left pull will occur at the time of deceleration of vehicle through braking. Third, selection of appropriate patterns must be executed in accordance with the vehicles since the effects of other factors of vehicle on pull must be considered. [5] Following this research, we are planning to execute further researches on vehicle pull under more diversified conditions in the future. REFERENCES [1] NamWoong K., Myung-il K. and BongSoo K. Study on tire footprint characteristics according to vehicle driving conditions. Proceeding KSAE Annual Autumn Conference & Exhibition. 2015. pp 514~514. [2] NamWoong K. The effect of change of driving force on tire footprint characteristics. Proceeding KSAE Annual Autumn Conference & Exhibition. 2016. pp 1123~1123. [3] NamWoong K., Bongsoo K. Technology trends of tire footprint characteristics research. KSAE Auto Journal 2016. pp 51-53. [4] Kiho Y., Hyo-Seok K., Chulwoo L., Influence of tire footprint shape on vehicle drift sensitivity. Annual Autumn Conference & Exhibition. 2008. pp 286~286. [5] Kiho Y., Juho K., Jeongho K., Optimization on tire PRAT for vehicle drift/pull improvement. Annual Autumn Conference & Exhibition. 2007. pp 1126~1131. http://www.iaeme.com/ijmet/index.asp 896 editor@iaeme.com