Standard No.:	GB 12676-2014
English Name:	Technical requirements and testing methods for commercial vehicle and trailer braking systems
Chinese Name:	商用车辆和挂车制动系统技术要求及试验方法
Chinese Classification:	T24    Braking system
Professional Classification:	GB    National Standard
ICS Classification:	43.040.40 43.040.40    Braking systems 43.040.40
Issued by:	AQSIQ, SAC
Issued on:	2014-10-10
Implemented on:	2015-7-1
Status:	valid
Superseding:	GB 12676-1999 GB 12676-1999 Systems - Structure, Performance and Test Methods
Language:	English
File Format:	PDF
Word Count:	42000 words
Price(USD):	300.0
Delivery:	via email in 1 business day

1 Scope This Standard specifies the technical requirements and testing methods for commercial vehicle and trailer braking systems. This Standard applies to motor vehicles of categories M2, M3, and N and category O trailers, as specified in GB/T 15089. This Standard does not cover: —— vehicles with a design speed not exceeding 25km/h; —— trailers which may not be coupled to motor vehicles with a design speed exceeding 25km/h; 2 Normative References The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. GB/T 3730.1 Motor Vehicles and Trailers - Types - Terms and Definitions GB/T 3730.2 Road Vehicle - Masses - Vocabulary and Codes GB/T 5345 Road Vehicles - Labelling of Containers for Petroleum-based or Non-petroleum-based Brake Fluid GB/T 5620 Road Vehicles - Braking of Automotive Vehicles and Their Trailers - Vocabulary GB/T 5922 Motor Vehicles and Towed Vehicles - Pressure Test Connection for Compressed-air Pneumatic Braking Equipment GB/T 13594-2003 Antilock Braking Performance and Test Procedure for Motor Vehicles and Their Trailers GB/T 15089 Classification of Power-driven Vehicles and Trailers GB/T 20716.1 Road Vehicles - Connectors for the Electrical Connection of Towing and Towed Vehicles - Part 1: Connectors for Braking Systems and Running Gears of Vehicles with 24V Nominal Supply Voltage GB/T 20716.2 Road Vehicles - Connectors for the Electrical Connection of Towing and Towed Vehicles - Part 2: Connectors for Braking Systems and Running Gears of Vehicles with 12V Nominal Supply Voltage ISO 11992-1 Road Vehicles - Interchange of Digital Information on Electrical Connections between Towing and Towed Vehicles - Part 1: Physical and Data-link Layer ISO 11992-2:2003 Road Vehicles - Interchange of Digital Information on Electrical Connections between Towing and Towed Vehicles - Part 2: Application Layer for Brakes and Running Gear 3 Terms and Definitions For the purposes of this Standard, the following terms and definitions as well as those given in GB/T 3730.1, GB/T 3730.2, GB/T 5620 and GB/T 15089 apply. 3.1 General Terms and Definitions 3.1.1 Vehicle type 3.1.1.1 Motor vehicle Vehicles which do not differ in the following essential respects with regard to braking system: —— the vehicle category; —— the maximum design total mass; —— the distribution of mass among the axles; —— the maximum design speed; —— the type of braking system, with more particular reference to the presence or otherwise of trailer braking system or electric regenerative braking system; —— the number and arrangement of the axles; —— the engine type; —— the number and transmission ratio of gears; —— the final drive ratios; —— the tyre dimensions. 3.1.1.2 Trailer Vehicles which do not differ in the following essential respects with regard to braking system: —— the vehicle category; —— the maximum design total mass; —— the distribution of mass among the axles; —— the type of braking equipment; —— the number and arrangement of the axles; —— the tyre dimensions. 3.1.2 Braking system The combination of components whose function is progressively to reduce the speed of a moving vehicle or to bring it to a halt, or to keep it stationary if it is already halted; the system consists of the control device, the transmission device, and the brake, etc.; 3.1.3 Actuation Both application and release of the control device. 3.1.4 Transmission device The combination of components comprised between the control device and the brake and linking them functionally. The transmission device may be mechanical, hydraulic, pneumatic, electric or mixed. Where the braking power is derived from or assisted by a source of energy independent of the driver, the accumulator is likewise part of the transmission device. The transmission device is divided into two independent functions: the control transmission and the energy transmission. Whenever the term "transmission" is used alone in this Standard, it means both the "control transmission" and the "energy transmission". The control and supply lines between towing vehicles and trailers shall not be considered as parts of the transmission device. 3.1.4.1 Control transmission device The combination of the components of the transmission device which control the operation of the brakes, including the control function and the necessary accumulator. 3.1.4.2 Energy transmission device The combination of the components which supply to the brakes the necessary energy for their function, including the accumulator necessary for the operation of the brakes. 3.1.5 Brake The part in which the forces opposing the movement of the vehicle develop. It may be a friction brake (when the forces are generated by friction between two parts of the vehicle moving relatively to one another); an electrical brake (when the forces are generated by electro-magnetic action between two parts of the vehicle moving relatively to but not in contact with one another); a fluid brake (when the forces are generated by the action of a fluid situated between two parts of the vehicle moving in relation to one another); or an engine brake (when the forces are derived from an artificial increase in the braking action, transmitted to the wheels, of the engine). 3.1.6 Different types of braking system Braking equipment which differ in the following essential respects: —— components having different characteristics; —— components made of materials having different characteristics, or components differing in shape or size; —— a different assembly of the components. 3.1.7 Component of the braking system One of the individual parts which, when assembled, constitute the braking system. 3.1.8 Continuous braking The braking of a combination of vehicles through a device having the following characteristics: —— a single control device which the driver actuates progressively, by a single movement, from his driving seat; —— the energy used for braking the vehicles constituting the combination is furnished by the same source (which may be the muscular energy of the driver); —— the braking device ensures simultaneous or suitably-phased braking of each of the constituent vehicles of the combination, whatever their relative positions; 3.1.9 Semi-continuous braking The braking of a combination of vehicles through a device having the following characteristics: —— a single control device which the driver actuates progressively, by a single movement, from his driving seat; —— the energy used for braking the vehicles constituting the combination is furnished by two different sources (one of which may be the muscular energy of the driver); —— the braking device ensures simultaneous or suitably-phased braking of each of the constituent vehicles of the combination, whatever their relative positions; 3.1.10 Automatic braking The braking of the trailer or trailers occurring automatically in the event of separation, including such separation through the breakage of a coupling. 3.1.11 Inertia (or overrun) braking The braking by utilizing the forces generated by the trailer's moving up on the towing vehicle. 3.1.12 Progressive and graduated braking/modulatable braking The braking during which, within the normal operating range of the equipment, the driver can adjust the braking force with sufficient precision by acting on the control device at will to increase or decrease the braking force proportionally along with the action on the control (monotonic function). 3.1.13 Phased braking Two or more sources of braking are operated by same control device, whereby one source may be given priority by phasing back the other source(s), so as to make increased control movement necessary before they begin to be brought into operation. 3.1.14 Endurance braking system An additional braking system having the capability to provide and to maintain a braking effect over a long period of time without a significant reduction in performance. The term "endurance braking system" covers the complete system including the control device. This definition does not cover the vehicles equipped with electric regenerative braking system. The endurance braking system may comprise a single device or a combination of several devices. Each device may have its own control. 3.1.14.1 Independent endurance braking system An endurance braking system whose control device is separated from that of the service and other braking systems. 3.1.14.2 Integrated endurance braking system An endurance braking system whose control device is integrated with that of the service braking system in such a way that both endurance and service braking systems are applied simultaneously or suitably phased by operation of the combined control device. 3.1.14.3 Combined endurance braking system An integrated endurance braking system, which in addition has a "cut-out" device, which allows the combined control device to control the service braking system alone. 3.1.15 Unladen condition The complete vehicle kerb mass + 110kg. 3.1.16 Laden condition Except where otherwise stated, a vehicle so laden as to attain its maximum design total mass. 3.1.17 The distribution of mass among the axles The distribution of the gravity on the loading mass of the vehicle and/or its contents among the axles. 3.1.18 Wheel/axle load The vertical static reaction (force) of the road surface in the contact area on the wheel/wheels of the axle. 3.1.19 Maximum stationary wheel/axle load The stationary wheel/axle load achieved under the condition of the laden vehicle. 3.1.20 Electric regenerative braking system; RBS A braking system which, during deceleration, provides for the conversion of vehicle kinetic energy into electrical energy. 3.1.20.1 Electric regenerative braking control device A device which modulates the braking action of the electric regenerative braking system. 3.1.20.2 Electric regenerative braking system of category A An electric regenerative braking system which is not part of the service braking system. 3.1.20.3 Electric regenerative braking system of category B An electric regenerative braking system which is part of the service braking system. 3.1.20.4 Electric state of charge The ratio of available capacity stored in storage battery relative to its rated capacity, see Appendix A for the testing method. 3.1.20.5 Traction battery A battery pack used for powering the traction motor(s) of the vehicle. 3.1.21 Hydraulic braking system with stored energy The braking equipment where energy is supplied by a hydraulic fluid under pressure, stored in accumulator; the hydraulic fluid under pressure is supplied by hydraulic pump(s) fitted with pressure limiting device, the pressure limiting value is specified by the manufacturer. 3.1.22 Simultaneous lockup of the front and rear wheels The condition when the time interval between the first occurrence of lockup of the last (second) wheel on the mid or rear axle (group) and the first occurrence of lockup on the last (second) wheel on the front axle (group) is less than 0.1s. 3.1.23 Electric control line The electrical connection between motor vehicle and trailer, providing the braking control function to a trailer. It comprises the cable, connector, the parts for data communication and the electrical energy supply parts for the trailer control transmission. 3.1.24 Data communication The transfer of digital data under the rules of a protocol. 3.1.25 Point to point A topology of a communication network with only two units. Each unit has an integrated termination resistor for the communication line. 3.1.26 Coupling force control system A system to balance automatically the braking strength of towing vehicle and trailer. 3.1.27 Nominal value The braking reference performance obtained to put a value on the transfer functions of the braking system, relating input to output for vehicles individually and when used in combination, which is used to characterize the relationship between the braking strength of the vehicle on its own and the level of braking input variable. "Nominal value" is defined, for a motor vehicle, as characteristic parameter which relates braking strength of the vehicle on its own to the level of the braking input variable. "Nominal value" is defined, for a trailer, as the characteristic parameter which relates the braking strength to the coupling head signal. "Nominal demand value" is defined, for coupling force control, as the characteristic parameter which relates the coupling head signal to the braking strength. 3.1.28 Automatically commanded braking A function within a complex electronic vehicle control system where actuation of the braking system(s) or brakes of certain axle is made for the purpose of generating vehicle retardation, resulting from the automatic assessment of on-board initiated information. 3.1.29 Selective braking A function within a complex electronic control system where actuation of individual brakes is made by automatic means in which vehicle retardation is secondary to vehicle behaviour modification. 3.1.30 Reference braking forces The braking forces of one axle generated at the circumference of the tyre on a roller brake tester. 3.2 Terms and Definitions of Complex Electronic Vehicle Control Systems 3.2.1 Safety concept A description of the measures designed into the system, for example within the electronic units, so as to address system integrity and thereby ensure safe operation even in the event of an electrical failure. Maintaining partial operation or providing a back-up system for vital vehicle functions may be a part of the safety concept. 3.2.2 Electronic control system A combination of units, designed to cooperate in the production of the stated vehicle control function by electronic data processing. Such systems, often controlled by software, are built from discrete functional components such as sensors, electronic control units and actuators and connected by transmission links. They may include mechanical, electro-pneumatic or electro-hydraulic elements. "The system", referred to herein, is the electronic control system to be subjected to test. 3.2.3 Complex electronic vehicle control systems Those electronic control systems which are subject to override control and observe the principle that the lower-level electronic control system/function may be controlled by a higher-level electronic control system/function. A function which is under control becomes part of the complex system. 3.2.4 Higher-level control systems/functions The systems/functions which employ additional processing and/or sensing devices to modify vehicle behaviour by commanding variations in the normal function(s) of the vehicle control system. This allows complex systems to automatically determine priority order and change their control objectives according to the sensed circumstances. 3.2.5 Units The smallest divisions of system components. The combinations of these components will be treated as single entities for purposes of identification, analysis or replacement. 3.2.6 Transmission links Inter-connecting distributed units for the purpose of conveying signals, operating data or an energy supply. This equipment is generally electrical but may, in some part, be mechanical, pneumatic, hydraulic or optical. 3.2.7 Range of control An output variable and defines the range over which the system is likely to exercise control. 3.2.8 Boundary of functional operation The boundaries of the external physical limits within which the system is able to maintain control.

Foreword i 1 Scope 2 Normative References 3 Terms and Definitions 3.1 General Terms and Definitions 3.2 Terms and Definitions of Complex Electronic Vehicle Control Systems 4 Technical Requirements 4.1 General Requirements 4.2 Characteristics of Braking Systems 5 Test and Performance Requirements 5.1 Test Requirements 5.2 The Performance Requirement for Systems of Vehicles of Categories M and N 5.3 Performance Requirements for Braking System of Type Q Vehicle 5.4 Response Time 6 Vehicle Type Approval and Extensions 6.1 Vehicle Type Approval 6.2 Extension of Approved Vehicle Types 7 Conformity of Production Appendix A (Normative) Procedure for Monitoring the State of Traction Battery Charge A.1 Scope A.2 Inspection Procedure Appendix B (Normative) Method of Measuring the Response Time on Vehicles Equipped with Air Braking Systems B.1 General B.2 Motor Vehicles B.3 Trailers B.4 Examples of Simulator Appendix C (Normative) Provisions relating to Energy Supply and Energy Storage Devices (Energy Accumulators) C.1 Air Braking Systems C.2 Vacuum Braking System C.3 Hydraulic Braking System with Stored Energy Appendix D (Normative) Provisions relating to Specific Conditions for Spring Braking Systems D.1 Overview D.2 General D.3 Auxiliary Release System Appendix E (Normative) Distribution of Braking among the Axles of Vehicles and Requirements for Compatibility between Towing Vehicles and Trailers E.1 General Requirements E.2 Symbols E.3 Requirements for Motor Vehicles E.4 Requirements for Semi-trailers E.5 Requirements for Full and Centre-axle Trailers E.6 Requirements to be Met in case of Failure of the Braking Distribution System E.7 Markings E.8 Vehicle Testing Appendix F (Normative) Test Specifications for Assessing Function Compatibility of Vehicles Equipped With Electric Control Lines F.1 General F.2 Information Document F.3 Towing Vehicles F.4 Trailers Appendix G (Normative) Inertia Dynamometer Test Method for Brake Linings G.1 General G.2 Test Equipment G.3 Test Conditions G.4 Test Procedure G.5 Inspection of Brake Linings Appendix H (Normative) Special Requirements to be Applied to The Safety Aspects of Complex Electronic Vehicle Control Systems H.1 General H.2 Documentation H.3 Verification and Test Appendix I (Normative) Test Conditions for Trailers with Electrical Braking Systems I.1 General I.2 Requirements of Trailer I.3 Performance Requirements I.4 Compatibility of the Braking Rate of the Trailer and the Mean Fully Developed Deceleration of the Towing vehicle/Trailer Combination (trailer laden and unladen) Appendix J (Normative) Cases in which Type-I and/or Type-II (or Type-IIA) or Type III Tests do not have to be Carried out Appendix K (Normative) Alternative Procedures for Type-I and Type-III Tests for Trailer Brakes K.1 General K.2 Symbols K.3 Test Methods K.4 Test Requirements K.5 Test Procedures K.6 Performance Requirements for Automatic Brake Adjustment Devices Appendix L (Normative) Testing of Vehicles Equipped with Inertia (Overrun) Braking Systems L.1 General Requirements L.2 Symbols and Units L.3 General Requirements L.4 Requirements for Control Devices L.5 Tests and Measurements to be Carried out on the Control Devices L.6 Requirements for Brakes and Testing Conditions L.7 Tests and Measurements to be CARRIED put on the Brakes L.8 Compatibility between the Control Device and the Brakes of a Vehicle L.9 General Comments L.10 Test Reports L.11 Legends