Browse Topic: Manual transmissions
ZF foresees hybrid powertrain technology becoming more popular for commercial transport in the coming years, and it's working earnestly to be a major player in that realm. The supplier unveiled the TraXon 2 Hybrid transmission to the North American commercial vehicle market at last year's ACT Expo and is now evaluating the technology in real-world conditions. The next-gen automated manual transmission (AMT) is optimized to improve fuel efficiency for plug-in and full hybrid heavy-duty trucks and coaches, as well as special applications such as medium- to heavy-duty mobile cranes.
In addition to providing safety advantages, sound and vibration are being utilized to enhance the driver experience in Battery Electric Vehicles (BEVs). There's growing interest and investment in using both interior and exterior sounds for pedestrian safety, driver awareness, and unique brand recognition. Several automakers are also using audio to simulate virtual gear shifting of automatic and manual transmissions in BEVs. According to several automotive industry articles and market research, the audio enhancements alone, without the vibration that drivers are accustomed to when operating combustion engine vehicles, are not sufficient to meet the engagement, excitement, and emotion that driving enthusiasts expect. In this paper, we introduce the use of new automotive, high-force, compact, light-weight circular force generators for providing the vibration element that is lacking in BEVs. The technology was developed originally for vibration reduction/control in aerospace applications, has been recently tested in various vehicles, and demonstrates the effectiveness for providing a real haptic feel across the entire vehicle. Shaking the vehicle globally provides a unique capability for BEVs, including Hybrid Electric Vehicles and for helping to create a smooth transition between Gas and Electric power, for example. The technology can be used to generate and emulate high-performance, high power, combustion engine feel, including idle, engine run-up/acceleration, simulated gear shifts, and Advanced Driving Assistance and Systems (ADAS) haptic indicators. The optional and customizable vibration can also mask road vibration which becomes very noticeable in otherwise smooth BEVs and can provide the perfect supplement to existing audio enhancements and gear shifting features. Additionally, the paper describes how the force generating device can be packaged in a light weight, compact, low-power manner. The technology will be compared to other force generating methods, and discuss its pros and cons.
Clutch wear is a significant factor affecting vehicle performance and maintenance costs, and understanding its dynamics is crucial for original equipment manufacturers (OEMs) to enhance product reliability and customer satisfaction. It is important to predict clutch wear to enable customers to understand the condition of their clutch and the remaining clutch life, to avoid sudden vehicle breakdowns. This paper explains the approach of measuring the clutch wear profile on an actual vehicle and simulating the same conditions on a powertrain test bench, with the establishment of a correlation in clutch wear profiles.
In current competitive automobile sector, gear shift quality has become significant factor for vehicle evaluation. OEMs are sensibly focusing on improving gear shift quality to meet customer’s expectations. Though there are different gear shifting habits in different drivers, diagonal shifting is the fastest way of shifting gears in manual transmission vehicle. So the components linked with shift system should be designed to facilitate smooth diagonal gear shift pattern. This paper enlightens the process of defining chamfers on internal gear shifting components for smooth diagonal shifting movement of gear shift lever. It is hard to define chamfers by analytical or practical approach. Creo-mechanism is very useful simulation tool which can be used to understand diagonal shift patterns and to define the chamfers.
This document describes a set of recommended actions to take to increase the likelihood of safe vehicle operation when a device (external test equipment, data collection device, etc.) whose normal operation has been compromised by a source external to the vehicle is connected to the vehicle’s diagnostic system. The term “diagnostic system” is intended to be a generic way to reference all the different ways that diagnostic commands might be injected into the system. The guidance in this document is intended to improve security without significantly impacting the ability for franchised dealer or independent aftermarket external test tools to perform legitimate diagnosis and maintenance functions. The goal is that intrusive services are only allowed to be performed when the vehicle is in a Safe State such that even if the intrusive service were to be initiated with adversarial intent the consequences of such a service would still be acceptable.
The clutch pedal in manual transmission plays a significant role in defining the comfort of driver as the component is one of the end user’s direct interface in the vehicle. Whenever driver operates the clutch pedal, comfort and NVH refinement should be felt over the complete pedal travel. The expectations of customer on NVH refinements, such as pedal vibration felt on foot during actuation, becomes the part of perceived quality and hence addressing the concern is very crucial. Due to advancements of technology and down-sizing of engines, NVH becomes the challenging area where the clutch pedal vibrations need to be eliminated to improve the comfort. In this paper we are explaining the problem statement and NVH solution to eliminate the clutch pedal vibration observed during clutch pedal actuation. Pedal vibrations were very severe at 10% clutch pedal pressed condition, and the same tends to diminish till 50% clutch pedal pressed condition. From initial position (0% clutch pedal pressed condition) to 10% clutch pedal pressed condition and after 50% clutch pedal pressed condition, the vibrations are not felt. Through Fast Fourier transform (FFT) analysis of measured results, it is found that the peak-to-peak linear acceleration of this clutch pedal vibration was between 3 to 8 m/s2 in idle condition. Also, it is found that the vibrations are following 0.5 engine excitation order and its harmonics (Frequency: 6.67 Hz) at idle condition. Such Low frequency high amplitude vibration creates numbness on the foot. Trials were conducted by varying the opening pressure and location of vibration cancellers on clutch high pressure pipe and by introducing flexible hoses of various stiffness and lengths and plastic pipes with various profiles in between the clutch high pressure pipe along with the foresaid dampers. While the higher opening pressure damper with the low stiffness rubber hose solves the pedal vibration concern, clutch system reserve in the total pedal travel got deteriorated thereby affecting the gear shifting quality of the system. This paper explains the effective method for finding optimal solution to resolve clutch pedal vibration concern without compromising the pedal travel and load efficiency of clutch system and significance of location of pedal vibration canceller in addressing the concern.
In emerging markets like India, manual transmission vehicles are still most preferred & contributes to 85% of passenger vehicle sales due to its cost benefit. However, customer expects good NVH behavior for comfortable driving experience in the vehicle to maneuver effortlessly in the highly congested traffic conditions in India. Clutch & its hydraulic release system in manual transmission of IC engines are the significant components which affects the NVH behavior & maneuverability of the vehicle and the driver comfort significantly. This paper focuses on the clutch pedal vibration & groan noise concern observed during clutch pedal actuation in high power density SUV vehicle developed for Indian market. The vehicle had highly efficient & light weight engine which has high engine axial vibrations. Axial vibrations are caused due to engine firing impulses & crankshaft bending causes flywheel axial movement. This movement in turn leads to vibrations in clutch cover diaphragm fingers which are transmitted to clutch pedal through hydraulic fluid pulsation via clutch release system which comprises of CSC, bleeder, clutch high pressure pipe & CMC. Engine vibrations which are transferred through clutch system to clutch pedal is felt on driver foot and causing discomfort during clutch pedal actuation/modulations while launching, creeping and for shifting of the gears in the vehicle. During pedal actuations at higher rpm for shifting gears, low frequency vibrations becomes high frequency and heard as groan noise inside the passenger cabin which results in uneasiness to driver and passengers. This paper describes the literature available, root cause analysis of the concern, effect of clutch disc, cover assembly, hydraulic release system design variables and the optimum solution which does not affect the other performance of the clutch function while reducing the clutch pedal vibration & groan noise concern through simulation & vehicle measurement results.
Agricultural Tractors consisting of a conventional manual transmission and dry friction clutch are mostly assembled with a mechanical type of clutch release mechanism where a defined amount of free play needs to be maintained between the clutch and Release Mechanism. A defined free play is required for efficient operation of clutch, Release Bearing as well as to ensure the durability of the system. As the clutch disc wears the free play between diaphragm spring or levers (as the case may be) and the release bearing is reduced. The rate at which the clutch disc wears is dependent on many factors like working condition of the tractor, grade of the friction lining material, experience of the driver, etc. This makes it very difficult to predict the exact timeline when the free play needs to be adjusted even though an approximate indication is given in instruction manuals. In today’s situation the adjustment of the free play is carried out manually and approximately. Many times, the adjustment activity is neglected, and this leads to early failures of the clutch release bearings and / or clutch. The purpose of this solution is to ensure that the free play adjustment is automatically carried out ensuring longer life of components. The system used for automation consists of a sensorized bearing, smart logic controller, and an actuator motor. As the adjustment would be carried out digitally, it would check and ensure the required free play is always available in the system, as well as eliminate manual intervention. The same can be extended to other areas of applications like commercial vehicles etc. where a mechanical release system is used. This paper describes the innovative ways to automatically maintain a fixed value of free play between the Diaphragm Spring fingers and the clutch release bearing at any point of time as well as to automate this process without manual intervention.
During the vehicle launch (i.e. moving the vehicle from “0” speed), the clutch would be slowly engaged by the Driver or Transmission Control Unit (in Automatic Transmission/Automatic Manual Transmission vehicle) for smooth torque transfer between engine and transmission. The clutch is designed to transfer max engine torque with min heat generation. During the clutch engagement, the difference in flywheel and gearbox input shaft speed is called the clutch slipping phase which then leads to a huge amount of energy being dissipated in terms heat due to friction. As a result, clutch surface temperature increases consistently, when the surface temperature crosses the threshold limit, the clutch wears out quickly or burns spontaneously. Hence it is crucial to predict the energy dissipation and temperature variation in various components of clutch assembly through virtual simulation. During the development process of the vehicle, the clutch is tested over many duty cycles to ensure the temperature, wear rate does not exceed the material thresholds. However, performing these tests for every prototype and for every variant can be expensive and time consuming. In this paper we have proposed a simulation methodology to replicate the vehicle test cycle (Hill- Fade test,) i.e. launching the vehicle on 15% grade followed by a cooling cycle and repeated over 150 cycles in the developed virtual simulation methodology using GT-SUITE application to accurately calculate the dissipated energy and the heat transfer through the components in the clutch housing. The developed simulation model can predict the surface temperature of clutch over the defined cycle, can predict the clutch life and can perform a Design Of Experiments analysis to optimize the vehicle or clutch parameter to meet the required customer targets. With the developed simulation model results and real-world vehicle testing results has been validated. The predicated simulation results have 90% correlation with the vehicle test data.
Global warming is the driver for introduction of CO2 and fuel consumption legislation worldwide. Indian truck manufacturers are facing the introduction of Indian fuel efficiency norms. In the European Union the CO2 emission monitoring phase of the most relevant truck classes was completed in June 2020 by usage of the Vehicle Energy Consumption Calculation TOol VECTO. Indian rule makers are currently considering an adaptation of VECTO for the usage in India, too. Indian truck market has always been very cost sensitive. Introduction of Bharat Stage VI Phase I has already led to a significant cost increase for emission compliance. Therefore, it will be of vital importance to keep the additional product costs for achievement of future fuel consumption legislation as low as possible as long as the real-world operation will not be promoted by the government. Especially when focusing on technologies that are needed to satisfy CO2 fleet approaches, a modular transmission family offers interesting possibilities, even with positive effects on gradeability and driving comfort. A transmission family on the base of an AMT (Automated Manual Transmission) allows reproducible engine operation and thus eliminates driver specific impacts on fuel consumption. This is then leading to higher fuel efficiency and a decrease in CO2 emissions. To demonstrate this effect, the comparison of the fuel efficiency values for a 9-speed manual transmission, 12- speed manual transmission and a 12-speed automated manual transmission will be done by a simulation with the official European Union certification tool VECTO.
Synchronizers are the critical element in manual transmission to match the speed of target gear, and allows smooth gear shifting. Generally, synchronizer failures are related to design parameters, like geometrical construction, material, and lubrication. This paper throws light on one different parameter for synchronizer design namely the angular accelerations which are imposed on synchronizer, due to vehicle level systems. The recent developed high-power density engines develop angular accelerations due to smaller flywheels. These angular accelerations are detrimental to the life of synchronizers. Brass synchronizers exhibit structural damage in synchronizer due to the angular acceleration. The carbon liner synchronizers do not withstand the angular acceleration and fail rapidly due to liner wear. The synchronizer rings can move freely in the available space due to rattling. The synchronizers which experience higher angular acceleration fails immediately. The simulation of synchronizer failure on vehicles with different configurations and interface conditions are cumbersome and time-consuming activity. A test setup was developed to simulate the vehicle level angular accelerations and to prove its effect on synchronizer life. Multiple solutions were tried out with the test set up to get an optimal solution for synchronizer life. The optimal solution was tested on the vehicle for final prove out. This test set up and methodology has been successfully used for resolution of very uncommon failure mode in synchronizer. The detailed progressive path for this evolved methodology has captured in this paper. This paper presents the influence of angular acceleration on the life of the synchronizer ring and the methods to overcome the failure.
Synchronizers are shifting elements in transmissions with power interruption, such as manual transmissions (MT) and automated manual transmissions (AMT). Synchronizers are also used in dual clutch transmissions (DCT) for shifting the preselected idler gear in the load-free branch of the transmission. Electric drive units (EDU) mainly consist of a two-stage transmission combined with a high-speed electric motor. Synchronizers realize the power flow from an idler gear to a gear shaft of the transmission. Automotive transmissions are usually operated with lubricating oils in order to minimize friction and wear of the mechanical components. Lubricating oil has a major influence on torque losses and on vibration behavior of transmission components. Torsional vibrations of mechanical components in transmissions lead to natural vibrations with high impact forces and thus to high radiated airborne sound levels. This occurs in particular when hard surfaces impact and the components have a high level of spring stiffness in addition to low damping properties. A drive torque that has a rotational irregularity leads to torsional vibrations of the components outside the power flow and is the starting point for transmission noises. Synchronizers have a function-related circumferential backlash in order to be able to shift the gear in a synchronized manner and therefore contribute to undesirable transmission noises. The aim of this work is to measure the vibrations of a synchronizer ring due to torsional vibration excitation while varying various parameters and to show the influences of the parameters. In particular, the lubricating oil has an influence on the torque losses and on the vibration behavior of a synchronizer. Lubricating oil with a low coefficient of friction due to its chemical structure leads to lower torque losses of the synchronizer and reduces the vibrations, which leads to a 1-2 dB(A) lower noise level of the transmission.
For 4x4 enthusiasts who see the electric-vehicle (EV) future as the conclusive death-blow to manual transmissions, there is hope. Jeep engineers have unveiled the first battery-electric Wrangler and it's fitted with a 6-speed manual gearbox. The clever prototype powertrain is the centerpiece of the Wrangler Magneto concept vehicle, developed to show that the world's original 4-wheel-drive utility vehicle can sustain the transition to zero-emissions propulsion without losing any off-road capability. The Magneto's mission is to prove it's in fact got even more mojo in the dirt, mud and on slickrock than its combustion-engine cousins. Many in the trail-driving community believe that quiet electric drivelines will help keep off-roading alive, and even expand it, as emissions and noise regulations tighten.
In this current fast-paced world, releasing a defect free product on time is of utmost importance in the automotive domain. The automobile powertrain is designed with a fine balance of weight and power. Clutch, an intermediate part between engine & transmission in manual transmission vehicle plays crucial role for vehicle smooth drive & functionality. Hydraulic clutch slave cylinder (CSC) which is a part of clutch release system was observed with one failure mode in one of the vehicles during internal road validation. It facilitates to actuate the clutch diaphragm in order to disengage the clutch when clutch pedal is pressed and to re-engage the clutch back when the clutch pedal is released. CSC failure directly disconnects the response of leg to clutch and thus driver may lose vehicle control and can possibly cause a severe vehicle crash. After investigation and dismantling the failed part, wear marks were observed on anti-rotation pin (which locks CSC hydraulic chamber against plastic body) and on elliptical O-ring, which locks oil flow to the plastic chamber. Unique in the industry, a component-level test setup was developed for validation and improved CSC design. Few samples were successfully tested for failure simulation and results were very encouraging. For strengthening of the CSC, design modification was done, and the new designed parts were tested on the same component-level test setup for validation. The sample passed the component-level test, and subsequently vehicle level test, and was approved for production. The component-level test methodology helped to test multiple design iterations and samples within a postulated time and cost. This methodology can be used as a part of front-loading support for all future projects.
Gear rattle noise is one of the important characteristics of manual and dual-clutch transmission，it is generated by the impact of unloaded meshing gear pairs in the transmission due to engine torsional vibration. Based on a front-drive manual transmission and a five dynos drivetrain NVH test bench with high-speed sine wave generator function, this paper designs an experimental program suitable for transmission rattle noise. By driving dynamometer to simulate the torque fluctuation of real engine, the main research is to study the characteristics of the transmission rattle noise under different excitation amplitudes and different excitation frequencies, and the sensitivity of rattle noise under different gears, different oil temperatures, different excitation amplitudes and excitation frequencies is analyzed. Finally, the transmission maps of rattle noise in different gears can be obtained. The research results in this paper provide a credible basis and method for the development and design of the transmission NVH and its verification test. Meanwhile, it also provides important data support for the matching selection and engine calibration development of the traditional and hybrid powertrain, which has strong engineering guiding significance. The follow-up work is also prospected at the end of the paper.
The following article aims to compare the performance parameters between a continuously variable transmission (CVT) and a 6-gear manual transmission. The manual transmission is a usual type of transmission system, consisting in a clutch and a transmission gearbox, containing a set of gears which, according to the coupling chosen, creates a reduction between the speed of the engine and the gearbox output. Meanwhile, the continuously variable transmission (CVT) is a type of transmission that outputs any reduction, between certain limits, in a continuous way, from two pulleys linked through a metallic belt. Due to the characteristics of both transmission systems, it is possible to infer that there are differences on the vehicle’s performance. The comparison between both types of transmissions, applied to a passenger’s vehicle is done through the mathematical modeling considering the same usage profile. Thus, parameters such as vehicle speed, traveled distance, engine speed and transmission reduction were obtained by the dynamic computational analysis and compared, explicating advantages and disadvantages of each system.
Purpose-built from the ground up, the next-generation Western Star 49X vocational truck is underpinned by a stronger, lighter chassis and equipped with a new X-series steel-reinforced aluminum cab that's claimed to be the segment's largest with 10 to 13% more space while being 8% lighter. Technology upgrades that bolster productivity, safety and uptime for the vocational market include Detroit Assurance active safety systems such as Side Guard Assist and the Detroit DT12 Vocational series of automated manual transmissions, which debuts on the Class 8 vocational truck. “We've completely rethought the foundation of the 49X to make it easier to upfit,” David Carson, senior vice president, vocational segment, Daimler Trucks North America, stressed during a virtual press event introducing the new truck. Engineers focused on clear back-of-cab packaging and features that contribute to easier upfitting: forward-mounted DEF tanks; standard in-cab battery box; multiple air tank mounting locations; air dryer mounted under hood (SBA) or under cab (SFA); and dual vertical exhaust stacks.
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