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Constant-velocity (CV) joints have become standard design and an integral part of modern vehicles, primarily due to their superiority in terms of CV torque transfer. Despite widespread usage of constant velocity joints there are certain aspects of their friction, wear, and contact characteristics that are not well understood. In this article, the n...
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... Based on both the friction and GAF models, one can establish a better understanding of CV joint friction and use these models for designing vehicle components with improved performance. The test apparatus and instrumentation used in this work, are shown in Fig. 1 and is described in detail in Lee and Polycarpou [5]. The apparatus uses complete CV joint assemblies and consists of dynamic sliding and height adjustment mechanisms and a static torque generator. ...
Constant velocity (CV) joints have been favored for automotive applications, compared to universal joints, due to their superiority of constant velocity torque transfer and plunging capability. High speed and sport utility vehicles with large joint articulation angles, demand lower plunging friction inside their CV joints to meet noise and vibration requirements, thus requiring a more thorough understanding of their internal friction characteristics. In this paper, a phenomenological CV joint friction model was developed to model the friction behavior of tripod CV joints by using an instrumented CV joint friction apparatus with tripod-type joint assemblies. Experiments were conduced under different operating conditions of oscillatory speeds, CV joint articulation angles, lubrication, and torque. The experimental data and physical parameters were used to develop a physics-based phenomenological CV joint dynamic friction model. It was found that the proposed friction model captures the experimental data well, and the model was used to predict the external generated axial force, which is the main source of force that causes vehicle vibration problems.
Description
Thirty chapters provide a comprehensive overview of various lubrication aspects of a typical powertrain system including the engine, transmission, driveline, chassis, and other components. The manual addresses major issues and current development status of automotive lubricant test methods.
Topics also cover advanced lubrication and tribochemistry of the powertrain system, such as diesel fuel lubrication, specialized automotive lubricant testing development, filtration testing of automotive lubricants, lubrication of constant velocity joints, and biodegradable automotive lubricants.
Major chapters cover:
The angles between the drive shafts and the power output shaft (hereinafter called the angles of the drive shafts) will generate the axial force. Excessive axial force will cause the vehicle to swing laterally. A vehicle, which appears lateral swing when accelerating at wide open throttle in third gear, is found that the frequency of the third-order vibration of the drive shafts is in good agreement with the frequency of lateral swing. The test result of the coordinate measuring machine (CMM) shows that the value of the angles of the drive shafts is larger than the design value. After reducing the angles of the drive shafts by adding weight, the lateral swing of the vehicle (hereinafter called lateral swing) is significantly weakened. In order to exclude the influence of the weight on the test results and considering the space constraints of engine room, the length of suspension spring is changed to reduce the angles of the drive shafts, and both subjective evaluation and test results show that the lateral swing is significantly weakened. Therefore, that the lateral swing is strongly related to the angles of the drive shafts is verified. This article could provide reference for the analysis of the lateral swing.KeywordsThe angles of the drive shaftsAxial forceLateral swingFrequency
div class="section abstract"> Electric vehicles (EV’s) are very much noise, vibration and harshness (NVH) sensitive due to the absence of engine noise. The outline of this paper is based on vehicle level turning noise evaluation. The impact of the driveshaft angle in the frequency range of 1000-2000Hz. The level of noise while turning at driver and co-driver side is evaluated first. Then the possible countermeasure to address such noise issues are also discussed. The impact on the angular adjusted roller (AAR) joint and driveshaft angle is studied along with the impact on other parameters like powertrain mount stiffness, ground clearance and vehicle architecture.
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A real-time wear measurement system for tripod type Constant Velocity (CV) joints is proposed in this study. Adhesive wear on tripod type CV joints is very crucial to the life time of CV joints but it is very difficult to measure the wear depth of a tripod type CV joint separate from the drive shaft assembly. The wear measurement system developed in this study can measure the wear depth of a tripod type CV joint in real-time as it applies kinematics and forces to the CV joint.
In order to apply the same motions as the motions of an actual CV joint, kinematics of the CV joint has been analyzed. As a result, reciprocating stroke and yaw motions have been completely implemented in the system. The wear measurement system comprises four parts. The first part is for applying normal forces to a set of spherical roller and housing track. One servo motor, spur gear and ball screw sets were employed to generate and augment the normal forces. The second and third parts are for applying reciprocating stroke and yaw motions, respectively. These parts synchronize with each other to make the same motion profiles as the actual CV joint. The fourth part is for measurement. This part consists of load cell and rotary encoder to measure the surge normal forces caused by the flaking phenomena and the wear depth caused by the adhesive wear. In the case of the encoder, the wear depth is augmented by the ball screw and spur gear sets so 0.18°/μm of measurement resolution can be achieved.
For the validation of the system, a tripod type CV joint was selected, and its wear depth was measured by the system and the results were compared with the wear depth measured by a profilometer.
High performance greases with separate additive formulations for low friction and wear have been developed specifically for constant-velocity (CV) joints. CV joint grease performance was studied utilizing a versatile pin-on-disk tribometer. Tests were conducted under dry and submerged grease lubricated conditions using two CV joint greases containing different additives. Grease B with solid EP additives showed better friction performance at normal contact pressures below 300 MPa, at which point grease A became superior due to its organo-molybdenum pressure sensitive additives. Grease B achieved better wear performance over grease A, but this trend was not readily apparent with negligible differences in wear depths of the disks. Balancing combinations of low friction and anti-wear additives were necessary in the development of CV joint greases to improve CV joint performance and durability. This is an abstract of a paper presented at the 2006 STLE Annual Meeting Conference Proceedings (TELUS Convention Centre Calgary, Alberta, Canada 5/7-11/2006).
Constant Velocity (CV) joints are an integral part of modern vehicles, significantly affecting steering, suspension, and vehicle vibration comfort levels. Each driveshaft comprises of two types of CV joints, namely fixed and plunging types connected via a shaft. The main friction challenges in such CV joints are concerned with plunging CV joints as their function is to compensate for the length changes due to steering motion, wheel bouncing and engine movement. Although CV joints are common in vehicles, there are aspects of their internal friction and contact dynamics that are not fully understood or modeled. Current research works on modeling CV joint effects on vehicle performance assume constant empirical friction coefficient values. Such models, however are not always accurate, especially under dynamic conditions which is the case for CV tripod joints. In this research, an instrumented advanced CV joint friction tester was developed to measure the internal friction behavior of CV joints using actual tripod-type joint assemblies. The setup is capable of measuring key performance parameters, such as friction and wear, under different realistic operating conditions of oscillatory speeds and CV joint installation angles. The tester incorporates a custom-installed tri-axial force transducer inside the CV joint to measure in-situ internal CV joint forces (including friction). Using the designed test setup, we investigated the interfacial parameters of CV joints in order to understand their friction mechanism. Specifically the slip-to-roll ratio of the roller inside the CV joint was measured to better understand the sliding and rolling friction between the tripod's roller and housing. Intrinsic interfacial parameters, such as torque, articulation angle, plunging velocity and rotational phase angle of CV joints were also varied in order to examine their effects on the friction. Based on these experiments, one can establish a better understanding of CV joint friction and develop a model that can be used in designing improved CV joints.
To analyze the contact between two spherical bodies with different radii of curvature, the three-dimensional (3D) Hertz theory for elliptical contact is typically used. When the two contacting bodies have high conformity, such as the case for ball-in-groove, the Hertz theory may break down. In this research, finite element analysis (FEA) was used to assess the validity of 3D Hertz theory as found in the roller-housing contact of constant velocity joints. The contact area, normal approach, and contact pressure results show that Hertz agrees with FEA predictions for low compressive loads, where the contact ellipse is within the geometrical contact dimensions. At higher loads the contact ellipse extends beyond the contacting geometrical dimensions and the simplified analytical Hertz results diverge from the FEA results. [DOI: 10.1115/1.4000735]
