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4、0 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/standards.sae.org/J645_201708 SURFACE VEHICLE RECOMMENDED PRACTICE J645 AUG2017 Issued 1956-04 Revised 2017-08 Su
5、perseding J645 MAR2009 Automotive Transmission Terminology RATIONALE The Committee added several new definitions for current industry state of the art technologies. Also revised definitions of existing technologies for improved clarity to readers. 1. SCOPE The following listed definitions are intend
6、ed to establish terminology and criteria for describing the various kinds of automotive transmissions. A specific arrangement may be described by a combination of several of these definitions. 2. REFERENCES There are no referenced publications specified herein. 3. DEFINITIONS 3.1 TRANSMISSION A devi
7、ce for transmitting power at a multiplicity of speed and torque ratios. 3.2 TRANSAXLE A device which combines a transmission with a final drive unit that includes a differential. In all definitions using the word “transaxle”, the word “transmission” can also be substituted. 3.3 TRANSMISSION TYPES 3.
8、3.1 Automatic Transmission A transmission in which ratio changes are effected automatically without requiring manual assist. 3.3.2 Traction Drive Transmission A transmission or subsystem in which power transfer and ratio change is effected through friction drive members without direct, discrete mech
9、anical connections such as gear teeth. These contacts can be driven through belts, discs, or other friction contact elements. SAE INTERNATIONAL J645 AUG2017 Page 2 of 3 3.3.3 Hydrodynamic Transmission An automatic transmission or subsystem using either a fluid coupling or torque converter, typically
10、 as a launch device. 3.3.4 Hydrostatic Transmission A transmission or subsystem using a positive displacement pump to drive a positive displacement motor. 3.3.5 Countershaft or Layshaft Transmission A mechanical transmission or subsystem in which selectable gears are located on parallel shafts. 3.3.
11、6 Manual Transmission A transmission in which ratio changes can only be obtained by direct operator input. 3.3.7 Planetary Transmission A transmission or subsystem using epicyclic gears. 3.3.8 Overdrive Transmission A transmission which provides a speed ratio wherein the transmission output speed is
12、 greater than the input speed. 3.3.9 Split Torque Drive Transmission A transmission which comprises two or more parallel torque paths. The individual paths may be any of several types such as mechanical, hydrodynamic, hydrostatic, or electromechanical. 3.3.10 Continuously Variable Transmission A tra
13、nsmission or subsystem with infinitely variable speed ratios within a finite range, not including neutral. 3.3.11 Hydromechanical Transmission A transmission or subsystem having both hydrostatic pump and motor and mechanical elements in the power path. 3.3.12 Auxiliary Transmission A transmission or
14、 subsystem used to supplement the gearing in a main transmission. Two, three, or more speeds are typically included in the auxiliary unit. It may be manually or automatically shifted. 3.3.13 Transfer Case A device for transmitting power from one drive unit to one or more outputs. It may include addi
15、tional ratios. 3.3.14 Dual Clutch Transmission A single automatic unit which incorporates two discrete transmissions in parallel with a single output, where each has a friction clutch as its input device. 3.3.15 Infinitely Variable Transmission A transmission with infinitely variable speed ratios wi
16、thin a defined range which covers from a given forward ratio, through neutral, to a given reverse ratio. SAE INTERNATIONAL J645 AUG2017 Page 3 of 3 3.3.16 Step Ratio Transmission A transmission with multiple discrete speed ratios within a defined range which covers from underdrive to overdrive ratio
17、s and also include a given reverse ratio. 3.3.17 Electric Variable Transmission A transmission with infinitely variable speed ratios within a defined range by using electric motors / generators to ratio between defined gear ratios. 3.3.18 Hybrid Transmission A transmission connected to a prime mover
18、 with electric motors/generators, pump motors, or other reversable machines used as inputs and/or outputs to drive the vehicle. 4. NOTES 4.1 Revision Indicator A change bar (I) located in the left margin is for the convenience of the user in locating areas where technical revisions, not editorial ch
19、anges, have been made to the previous issue of this document. An (R) symbol to the left of the document title indicates a complete revision of the document, including technical revisions. Change bars and (R) are not used in original publications, nor in documents that contain editorial changes only. PREPARED BY THE SAE AUTOMATIC TRANSMISSION AND TRANSAXLE TECHNICAL STANDARDS COMMITTEE
