Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This standard is prepared in accordance with the rules given in GB/T 1.1-2009.
This standard replaces JT/T 721-2008 Requirements and test methods of electromagnetic retarder for the use of bus. The following main technical changes have been made with respect to JT/T 721-2008:
——The content of "General requirements" for retarder has been added (see Clause 4);
——The "independent brake of retarder" has been modified to "independent brake of retarder in full gear" (see 5.1, 5.2 and 5.3 herein, 5.1, 5.2 and 5.3 in 2008 Edition);
——The "retarder quickly enters working state" has been modified to "retarder quickly enters full gear working state" (see 6.2 herein, 6.2.1.2 in 2008 Edition);
——The test procedures have been modified (see 6.2, 6.3 and 6.4 herein; 6.2.1, 6.2.2 and 6.2.3 in 2008 Edition);
——The content of “Test conditions” has been modified (see 6.1 herein; 6.1 in 2008 Edition);
——The "rotor operating temperature shall not be higher than 450°C" has been deleted (see 5.2.1 in 2008 Edition);
——The part of bench test in the heat fade test has been deleted (see 6.2.2.1 in 2008 Edition).
This standard was proposed by and is under the jurisdiction of Subcommittee on Bus of National Technical Committee on Automobiles of Standardization Administration of China (SAC/TC 114/SC 22).
The previous edition of this standard is as follows: JT/T 721-2008.
Requirements and test methods of electromagnetic retarder for the use of bus
1 Scope
This standard specifies the performance requirements and test methods for electromagnetic retarder for bus.
This standard is applicable to buses with more than 22 passengers (excluding driver) and a maximum design total mass exceeding 5,000 kg. It may serve as a reference for other types of buses.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated reference, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 2408 Plastics — Determination of burning characteristics — Horizontal and vertical test
GB/T 3730.1 Motor vehicles and trailers — Types — Terms and definitions
GB/T 3730.2 Road vehicle — Masses — Vocabulary and codes
GB/T 12534 Motor vehicles — General rules of road test method
GB/T 26572 Requirements of concentration limits for certain restricted substances in electrical and electronic products
QC/T 29106 Technical specification of automobile wire harness
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 3730.1 and GB/T 3730.2 shall apply.
3.1
electromagnetic retarder
device that uses magnetoresistance (e.g. eddy current, hysteresis) generated by rotating parts under the action of magnetic field to provide braking efficiency for vehicles independently
4 General requirements
4.1 Electromagnetic retarder (hereinafter referred to as "retarder") shall have a controller local area network (CAN bus) interface or an interface linked with vehicle antilock brake system (ABS). When ABS detects the brake lock of the vehicle, the retarder controller shall be able to automatically turn off the working power supply of the retarder; when the ABS brake lock is released, the retarder shall automatically return to working state.
4.2 The retarder shall be set in a working gear corresponding to its braking torque, and the braking torque of the first gear shall not be greater than 1/2 of the maximum braking torque of the retarder.
4.3 The technical conditions of retarder wire harness shall meet the requirements of QC/T 29106.
4.4 The flame retardant grade of retarder wire harness and wrapping material shall meet V-0 requirement of GB/T 2408, and temperature adaptability shall be -40°C ~ 125°C.
4.5 The limit requirements of restricted substances for electronic components of retarder shall meet GB/T 26572.
4.6 The control mode of retarder is classified into manual control and foot control. If manual control is adopted, the manual switch shall be installed at a position convenient for the driver to operate; if foot control is adopted, ensure that the retarder works before the service brake.
5 Performance requirements
5.1 Break performance
The test vehicle runs at a constant speed of 50 km/h on a flat road, and the retarder is independently braked in full gear. When the test vehicle speed is 30 km/h, the deceleration (a) shall meet the requirements of 0.62 m/s2 ≤ a ≤ 1.0 m/s2 or the deceleration duration (t) shall meet the requirements of 5.6 s ≤ t ≤ 9.0 s.
5.2 Heat fade performance
After the test vehicle runs continuously at a speed of 50 km/h for 12 min under the action of independent brake of retarder in full gear, the brake performance shall not be less than 40% of the deceleration specified in 5.1 or not higher than 2.5 times of the specified brake time.
5.3 Repeatability
The test vehicle runs at a speed of 50 km/h under the action of independent brake of retarder in full gear. After the retarder works continuously in the highest gear for 12 min, it stops working for 18 min as a cycle. The performance of the retarder after 10 cycles shall meet the requirements of 5.1 and 5.2.
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 General requirements
5 Performance requirements
6 Test methods
JT/T 721-2017, JT 721-2017, JTT 721-2017, JT/T721-2017, JT/T 721, JT/T721, JT721-2017, JT 721, JT721, JTT721-2017, JTT 721, JTT721
Introduction of JT/T 721-2017
Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This standard is prepared in accordance with the rules given in GB/T 1.1-2009.
This standard replaces JT/T 721-2008 Requirements and test methods of electromagnetic retarder for the use of bus. The following main technical changes have been made with respect to JT/T 721-2008:
——The content of "General requirements" for retarder has been added (see Clause 4);
——The "independent brake of retarder" has been modified to "independent brake of retarder in full gear" (see 5.1, 5.2 and 5.3 herein, 5.1, 5.2 and 5.3 in 2008 Edition);
——The "retarder quickly enters working state" has been modified to "retarder quickly enters full gear working state" (see 6.2 herein, 6.2.1.2 in 2008 Edition);
——The test procedures have been modified (see 6.2, 6.3 and 6.4 herein; 6.2.1, 6.2.2 and 6.2.3 in 2008 Edition);
——The content of “Test conditions” has been modified (see 6.1 herein; 6.1 in 2008 Edition);
——The "rotor operating temperature shall not be higher than 450°C" has been deleted (see 5.2.1 in 2008 Edition);
——The part of bench test in the heat fade test has been deleted (see 6.2.2.1 in 2008 Edition).
This standard was proposed by and is under the jurisdiction of Subcommittee on Bus of National Technical Committee on Automobiles of Standardization Administration of China (SAC/TC 114/SC 22).
The previous edition of this standard is as follows: JT/T 721-2008.
Requirements and test methods of electromagnetic retarder for the use of bus
1 Scope
This standard specifies the performance requirements and test methods for electromagnetic retarder for bus.
This standard is applicable to buses with more than 22 passengers (excluding driver) and a maximum design total mass exceeding 5,000 kg. It may serve as a reference for other types of buses.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated reference, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 2408 Plastics — Determination of burning characteristics — Horizontal and vertical test
GB/T 3730.1 Motor vehicles and trailers — Types — Terms and definitions
GB/T 3730.2 Road vehicle — Masses — Vocabulary and codes
GB/T 12534 Motor vehicles — General rules of road test method
GB/T 26572 Requirements of concentration limits for certain restricted substances in electrical and electronic products
QC/T 29106 Technical specification of automobile wire harness
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 3730.1 and GB/T 3730.2 shall apply.
3.1
electromagnetic retarder
device that uses magnetoresistance (e.g. eddy current, hysteresis) generated by rotating parts under the action of magnetic field to provide braking efficiency for vehicles independently
4 General requirements
4.1 Electromagnetic retarder (hereinafter referred to as "retarder") shall have a controller local area network (CAN bus) interface or an interface linked with vehicle antilock brake system (ABS). When ABS detects the brake lock of the vehicle, the retarder controller shall be able to automatically turn off the working power supply of the retarder; when the ABS brake lock is released, the retarder shall automatically return to working state.
4.2 The retarder shall be set in a working gear corresponding to its braking torque, and the braking torque of the first gear shall not be greater than 1/2 of the maximum braking torque of the retarder.
4.3 The technical conditions of retarder wire harness shall meet the requirements of QC/T 29106.
4.4 The flame retardant grade of retarder wire harness and wrapping material shall meet V-0 requirement of GB/T 2408, and temperature adaptability shall be -40°C ~ 125°C.
4.5 The limit requirements of restricted substances for electronic components of retarder shall meet GB/T 26572.
4.6 The control mode of retarder is classified into manual control and foot control. If manual control is adopted, the manual switch shall be installed at a position convenient for the driver to operate; if foot control is adopted, ensure that the retarder works before the service brake.
5 Performance requirements
5.1 Break performance
The test vehicle runs at a constant speed of 50 km/h on a flat road, and the retarder is independently braked in full gear. When the test vehicle speed is 30 km/h, the deceleration (a) shall meet the requirements of 0.62 m/s2 ≤ a ≤ 1.0 m/s2 or the deceleration duration (t) shall meet the requirements of 5.6 s ≤ t ≤ 9.0 s.
5.2 Heat fade performance
After the test vehicle runs continuously at a speed of 50 km/h for 12 min under the action of independent brake of retarder in full gear, the brake performance shall not be less than 40% of the deceleration specified in 5.1 or not higher than 2.5 times of the specified brake time.
5.3 Repeatability
The test vehicle runs at a speed of 50 km/h under the action of independent brake of retarder in full gear. After the retarder works continuously in the highest gear for 12 min, it stops working for 18 min as a cycle. The performance of the retarder after 10 cycles shall meet the requirements of 5.1 and 5.2.
Contents of JT/T 721-2017
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 General requirements
5 Performance requirements
6 Test methods
