GB 12676-2014 PDF English (GB 12676-1999: Older version)
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GB 12676-2014: PDF in English GB 12676-2014
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 43.040.40
T 24
GB/T 12676-2014
Replacing GB/T 12676-1999
Technical Requirements and Testing Methods for
Commercial Vehicle and Trailer Braking Systems
ISSUED ON: OCTOBER 10, 2014
IMPLEMENTED ON: JULY 01, 2015
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine of PRC;
Standardization Administration of PRC.
Table of Contents
Foreword ... 4
1 Scope ... 9
2 Normative References ... 9
3 Terms and Definitions ... 10
4 Specifications ... 16
5 Tests and Performance Requirements ... 43
6 Approval of Vehicle Type and Extension of Approval ... 61
7 Conformity of production (COP) ... 63
Annex A (Normative) Procedure for Monitoring the State of Battery Charge ... 64
Annex B (Normative) Method of measuring the response time on vehicles equipped
with compressed-air braking systems ... 65
Annex C (Normative) Provisions relating to energy sources and energy storage devices
(energy accumulators) ... 71
Annex D (Normative) Provisions relating to specific conditions for spring braking
systems ... 79
Annex E (Normative) Distribution of braking among the axles of vehicles and
requirements for compatibility between towing vehicles and trailers ... 82
Annex F (Normative) Test procedure to assess the functional compatibility of vehicles
equipped with electric control lines ... 96
Annex G (Normative) Inertia dynamometer test method for brake linings ... 103
Annex H (Normative) Special requirements to be applied to the safety aspects of
complex electronic vehicle control systems ... 107
Annex I (Normative) Test conditions for trailers with electrical braking systems ... 112
Annex 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 ... 115
Annex K (Normative) Alternative procedures for Type-I and Type-III tests for trailer
brakes ... 117
Annex L (Normative) Conditions governing the testing of vehicles equipped with inertia
(overrun) braking systems ... 124
Foreword
All specifications of this standard are compulsory.
This standard was drafted in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB 12676-1999, Road vehicle-Braking systems-Structure, performance and
test methods. Compared with GB 12676-1999, the following significant changes have been made:
Deleted the content of the vehicles of Category M1;
Added the following terms and definitions: Braking system, Control, Transmission, Brake,
Different types of braking systems, Component of a braking system, Continuous braking,
Semi-continuous braking, Automatic braking, Inertia (or overrun) braking, Progressive and
graduated braking, Phased braking, Endurance braking system, Laden, Unladen, The
distribution of mass among the axles, Wheel/axle load, Maximum stationary wheel/axle load,
Electric regenerative braking, Simultaneous lockup of the front and rear wheels, Electric
control line, Data communication, Point-to-point, Coupling force control, Nominal value,
Automatically commanded braking, Selective braking and Reference braking forces, etc.;
Deleted the following terms: Approval of a vehicle, braking of the same type, spring braking
system, pressure defined by the manufacturer and controllable braking, etc.;
Added the requirements for electric control line in the connections, for compressed-air braking
systems, between power-driven vehicles and trailers (See 4.1.3, or 4.1.5 in GB 12676-1999);
Added the provisions for the periodic technical inspection of braking systems (See 4.1.4);
Added the provisions on safety of complex electronic control system (See 4.1.5);
Added the requirements for distribution of the action of service braking system between the
wheels of one and the same axle (See 4.2.1.8 and 4.2.2.5);
Added the scope of vehicle categories that shall be equipped with an anti-lock braking system
(See 4.2.1.22 and 4.2.2.13);
Added the additional requirements for vehicles of categories M2, N1 and category N2 5,000
kg equipped with an electric regenerative braking system (See 4.2.1.24);
Added the special additional requirements for the electric transmission of the parking braking
system (See 4.2.1.25);
Added the special additional requirements for service braking systems with electric control
transmission (See 4.2.1.26 and 4.2.2.15);
Added the special requirements for coupling force control system (See 4.2.1.27);
Added the Free running test (See 5.1.5.4);
Added the Type-III test (See 5.1.7);
Added the scope of vehicle categories that shall be subject to the Type-II A test: (See 5.1.8.1);
Added the minimum braking performance requirements for the power-driven vehicles that are
allowed to be coupled with the unbraked trailer (See 5.2.1.2);
Added the additional failure check and performance requirements for vehicles employing
electric regenerative braking systems in emergency brake test (See 5.2.2.6);
Modified the evaluation indicators for the laden stopping distance of Category M2 and the
unladen stopping distance of Category N1 (See 5.2.4.1, or 5.2.2 in GB 12676-1999);
Incorporated the Clause 6 “braking system test method” into the Clause 5, and cancelled the
optional test (See Clause 5, or Clause 6 in GB 12676-1999);
Added the approval of vehicle type and extension of approval (See Clause 6);
Added the conformity of production (See Clause 7);
Added the procedure for monitoring the state of battery charge (See Annex A);
Added the method of measuring the response time on vehicles equipped with compressed-air
braking systems (See Annex B);
Added the provisions relating to energy sources and energy storage devices (energy
accumulators) (See Annex C);
Added the provisions relating to specific conditions for spring braking systems (See Annex D);
Added the test procedure to assess the functional compatibility of vehicles equipped with
electric control lines (See Annex F);
Added the special requirements to be applied to the safety aspects of complex electronic
vehicle control systems (See Annex H);
Added the test conditions for trailers with electrical braking systems (See Annex I);
Technical Requirements and Testing Methods for
Commercial Vehicle and Trailer Braking Systems
1 Scope
This Standard specifies the technical requirements and testing methods for commercial vehicle and
trailer braking systems.
This Standard applies to power-driven vehicles of categories M2, M3 and N AND trailers of category
O, as specified in GB/T 15089.
This Standard does not cover:
Vehicles with a design speed not exceeding 25 km/h;
Trailers which may not be coupled to power-driven vehicles with a design speed exceeding
25 km/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 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
The number and ratios of gears;
The final drive ratios;
The tyre dimensions;
3.1.1.2 Trailer
With regard to braking system, the vehicles which do not differ in such essential respects as:
The vehicle category;
The maximum design total mass;
The distribution of mass among the axles;
A different type of braking equipment;
The number and arrangement of the axles;
The tyre dimensions;
3.1.2 "Braking system" means the combination of parts whose function is progressively to reduce
the speed of a moving vehicle or bring it to a halt, or to keep it stationary if it is already halted. The
system consists of the control, the transmission, and the brake proper;
3.1.3 "Actuation" means both application and release of the control.
3.1.4 "Transmission device" means the combination of components comprised between the control
and the brake and linking them functionally. The transmission 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 reserve of energy in the system is likewise part of the
transmission.
The transmission 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.
3.1.4.1 "Control transmission device" means the combination of the components of the transmission
which control the operation of the brakes, including the control function and the necessary reserve(s)
of energy.
3.1.4.2 "Energy transmission device" means the combination of the components which supply to the
The braking installation ensures simultaneous or suitably-phased braking of each of the
constituent vehicles of the combination, whatever their relative positions;
3.1.10 "Automatic braking" means braking of the trailer or trailers occurring automatically in the
event of separation of components of the combination of coupled vehicles, including such
separation through the breakage of a coupling, the effectiveness of the braking of the remainder of
the combination not being thereby destroyed;
3.1.11 "Inertia (or overrun) braking" means 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" means braking during which,
within the normal operating range of the equipment and during actuation of the brakes, the driver
can at any moment increase or decrease the braking force by acting on the control and the braking
force varies proportionally as the action on the control (monotonic function), which can be easily
regulated with sufficient precision;
3.1.13 "Phased braking" is a means which may be used where two or more sources of braking are
operated from a common control, 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" means 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 doesn’t 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" means 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" means 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" means an integrated endurance braking system,
which in addition has a cut-out device, which allows the combined control to apply the service
braking system alone.
3.1.15 “Unladen condition” means the complete vehicle kerb mass adding 110 kg.
3.1.24 "Data communication" means the transfer of digital data under the rules of a protocol.
3.1.25 "Point-to-point" means 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" means a system/function to automatically balance the
braking rate of towing vehicle and trailer.
3.1.27 "Nominal value" definitions for braking reference performance are required to put a value on
the transfer function of the braking system, relating output to input for vehicles individually and when
used in combination.
"Nominal value" is defined, for a power-driven vehicle, as the characteristic which relates the
braking rate of the vehicle on its own to the level of the braking input variable.
"Nominal value" is defined, for a trailer, as the characteristic which relates the braking rate to the
coupling head signal.
"Nominal demand value" is defined, for coupling force control, as the characteristic which relates the
coupling head signal to the braking rate.
3.1.28 "Automatically commanded braking" means a function within a complex electronic control
system where actuation of the braking system(s) or brakes of certain axles is made for the purpose
of generating vehicle retardation with or without a direct action of the driver, resulting from the
automatic evaluation of on-board initiated information.
3.1.29 "Selective braking" means 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 behavior modification.
3.1.30 "Reference braking forces" means 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 system
3.2.1 "Safety concept" is 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.
The possibility of a fallback to partial operation or even to a back-up system for vital vehicle
functions may be a part of the safety concept.
3.2.2 "Electronic control system" means a combination of units, designed to co-operate in the
production of the stated vehicle control function by electronic data processing.
Standard. The braking response time on vehicles equipped with compressed-air braking systems
shall comply with the specifications in Annex B. The energy sources and energy storage devices of
braking system shall comply with the specifications in Annex C. The spring braking system shall
comply with the specifications in Annex D.
4.1.1.2 The braking system shall be so designed, constructed and fitted as to be able to resist the
corroding and ageing phenomena to which it is exposed.
4.1.1.3 Brake linings shall not contain asbestos.
4.1.1.4 The effectiveness of the braking systems, including the electric control line, shall not be
adversely affected by magnetic or electrical fields.
4.1.1.5 A failure detection signal may interrupt momentarily (< 10 ms) the demand signal in the
control transmission, provided that the braking performance is thereby not reduced.
4.1.2 Functions of the braking system
4.1.2.1 Service braking system
The service braking system shall make it possible to control the movement of the vehicle and to halt
it safely, speedily and effectively, whatever its speed and load, on any up or down gradient. It shall
be possible to graduate this braking action. The driver shall be able to achieve this braking action
from his driving seat without removing his hands from the steering control.
4.1.2.2 Secondary braking system
The secondary braking system shall make it possible to halt the vehicle within a reasonable
distance in the event of failure of the service braking system. It shall be possible to graduate this
braking action. The driver shall be able to obtain this braking action from his driving seat while
keeping at least one hand on the steering control. For the purposes of these provisions it is
assumed that not more than one failure of the service braking system can occur at one time.
4.1.2.3 Parking braking system
The parking braking system shall make it possible to hold the vehicle stationary on an up or down
gradient even in the absence of the driver, the working parts being then held in the locked position
by a purely mechanical device. The driver shall be able to achieve this braking action from his
driving seat, subject, in the case of a trailer, to the provisions of paragraph 4.2.2.10 of this Standard.
The trailer air brake and the parking braking system of the towing vehicle may be operated
simultaneously provided that the driver is able to check, at any time, that the parking brake
performance of the vehicle combination, obtained by the purely mechanical action of the parking
braking system, is sufficient.
4.1.3.5 A trailer may be equipped as defined in paragraph 4.1.3.1c), provided that it can only be
operated in conjunction with a power-driven vehicle with an electric control line which satisfies the
requirements of paragraph 4.2.1.18b) In any other case, the trailer, when electrically connected,
shall automatically apply the brakes or remain braked. The driver shall be warned by the separate
yellow warning signal specified in paragraph 4.2.1.28a).
4.1.3.6 The electric control line shall conform to ISO 11992-1 and 11992-2:2003 and shall be a
point-to-point type using the seven pin connector according to GB/T 20716.1 or GB/T 20716.2. The
data contacts of the connector shall be used to transfer information exclusively for braking (including
ABS) and running gear (steering, tyres and suspension) functions as specified in ISO 11992-2. The
braking functions have priority and shall be maintained in the normal and failed modes. The
transmission of running gear information shall not delay braking functions. The power supply,
provided by the GB/T 20716.1 or 20716.2 connector, shall be used exclusively for braking and
running gear functions and that required for the transfer of trailer related information not transmitted
via the electric control line.
4.1.3.7 The functional compatibility of towing and towed vehicles equipped with electric control lines
as defined above shall be assessed at the time of type approval by checking that the relevant
provisions of ISO 11992-1 and 11992-2:2003, are fulfilled. Annex F of this Standard provides an
example of tests that may be used to perform this assessment.
4.1.3.8 When a power-driven vehicle is equipped with an electric control line and electrically
connected to a trailer equipped with an electric control line, a continuous failure (> 40 ms) within the
electric control line shall be detected in the power-driven vehicle and shall be signaled to the driver
by the yellow warning signal specified in paragraph 4.2.1.28a), when such vehicles are connected
via the electric control line.
4.1.3.9 If the operation of the parking braking system on the power-driven vehicle also operates a
braking system on the trailer, then the following additional requirements shall be met:
a) When the power-driven vehicle is equipped according to paragraph 4.1.3.1a), the
actuation of the parking brake system of the power-driven vehicle shall actuate a braking
system on the trailer via the pneumatic control line.
b) When the power-driven vehicle is equipped according to paragraph 4.1.3.1b), the
actuation of the parking brake system on the power-driven vehicle shall actuate a braking
system on the trailer as prescribed in paragraph 4.1.3.9a) In addition, the actuation of the
parking brake system may also actuate a braking system on the trailer via the electric
control line.
c) When the power-driven vehicle is equipped according to paragraph 4.1.3.1c) or, if it
satisfies the requirements of paragraph 4.2.1.18b) without assistance from the pneumatic
control line, paragraph 4.1.3.1b), the actuation of the parking braking system on the
power-driven vehicle shall actuate a braking system on the trailer via the electric control
according to paragraph 4.1.4.5a) above.
c) The reference braking forces shall be declared such that the vehicle is capable of
generating a braking rate equivalent to that defined in Section 5 for the relevant vehicle (50
percent in the case of vehicles of category M2, M3, N2, N3, O3 and O4 except semi-trailers,
45 percent in the case of semi-trailers), whenever the measured roller braking force, for
each axle irrespective of load, is not less than the reference braking force for a given brake
actuator pressure within the declared operating pressure range.
4.1.4.7 It shall be possible to verify, in a simple way, the correct operational status of those complex
electronic systems which have control over braking. If special information is needed, this shall be
made freely available. The means implemented to protect against simple unauthorized modification
of the operation to the verification means chosen by the manufacturer (e.g. warning signal) shall be
confidentially outlined. Alternatively, this protection requirement is fulfilled when a secondary means
of checking the correct operational status is available.
4.1.5 Complex electronic control system
The requirements of Annex H shall be applied to the safety aspects of all complex electronic vehicle
control systems which provide or form part of the control transmission of the braking function
included those which utilize the braking system(s) for automatically commanded braking or selective
braking. However, systems or functions, which use the braking system as the means of achieving a
higher level objective, are subject to Annex H only as far as they have a direct effect on the braking
system. If such systems are provided, they shall not be deactivated during testing of the braking
system.
4.2 Characteristics of braking systems
4.2.1 Vehicles of categories M and N
4.2.1.1 The set of braking systems with which a vehicle is equipped shall satisfy the requirements
laid down for service, secondary and parking braking systems.
4.2.1.2 The systems providing service, secondary and parking braking may have common
components so long as they fulfill the following conditions:
a) There shall be at least two controls, independent of each other and readily accessible to
the driver from his normal driving position. This requirement shall not apply to a parking
brake control (or that part of a combined control) when it is mechanically locked in an
applied position;
b) The control of the service braking system shall be independent of the control of the parking
braking system;
paragraph 4.2.1.6 are met.
h) Certain parts, such as the pedal and its bearing, the master cylinder and its piston or
pistons (hydraulic systems), the control valve (hydraulic and/or pneumatic systems), the
linkage between the pedal and the master cylinder or the control valve, the brake cylinders
and their pistons (hydraulic and/or pneumatic systems), and the lever-and-cam assemblies
of brakes, shall not be regarded as liable to breakage if they are amply dimensioned, are
readily accessible for maintenance, and exhibit safety features at least equal to those
prescribed for other essential components (such as the steering linkage) of the vehicle.
Any such part as aforesaid whose failure would make it impossible to brake the vehicle
with a degree of effectiveness at least equal to that prescribed for secondary braking shall
be made of metal or of a material with equivalent characteristics and shall not undergo
notable distortion in normal operation of the braking systems.
4.2.1.3 Where there are separate controls for the service braking system and the secondary braking
system, simultaneous actuation of the two controls shall not render both the service braking system
and the secondary braking system inoperative, either when both braking systems are in good
working order or when one of them is faulty.
4.2.1.4 The service braking system shall, whether or not it is combined with the secondary braking
system, be such that in the event of failure in a part of its transmission a sufficient number of wheels
are still braked by actuation of the service brake control; these wheels shall be so selected that the
residual performance of the service braking system satisfies the requirements laid down in
paragraph 5.2.4.
However, the foregoing provisions shall not apply to tractor vehicles for semi-trailers when the
transmission of the semi-trailer's service braking system is independent of that of the tractor
vehicle's service braking system;
The failure of a part of a hydraulic transmission system shall be signaled to the driver by a device
comprising a red warning signal, as specified in paragraph 4.2.1.28a). Alternatively, the lighting up
of this device when the fluid in the reservoir is below a certain level specified by the manufacturer
shall be permitted.
4.2.1.5 Where use is made of energy other than the muscular energy of the driver, there need not
be more than one source of such energy (hydraulic pump, air compressor, etc.), but the means by
which the device constituting that source is driven shall be as safe as practicable.
In the event of failure in any part of the transmission of a braking system, the feed to the part not
affected by the failure shall continue to be ensured if required for the purpose of halting the vehicle
with the degree of effectiveness prescribed for residual and/or secondary braking. This condition
shall be met by means of devices which can be easily actuated when the vehicle is stationary, or by
automatic means.
4.2.1.28a). This requirement shall apply for all conditions of loading when compensation exceeds
the following limits:
a) A difference in transverse braking pressures on any axle of:
25 percent of the higher value for vehicle decelerations ≥ 2 m/s2;
A value corresponding to 25 percent at 2 m/s2 for decelerations below this rate.
b) An individual compensating value on any axle of:
> 50 percent of the nominal value for vehicle decelerations ≥ 2 m/s2;
A value corresponding to 50 percent of the nominal value at 2 m/s2 for decelerations
below this rate.
Compensation as defined above, is permitted only when the initial brake application is made at
vehicle speeds greater than 10 km/h.
4.2.1.9 Malfunctions of the electric control transmission shall not apply the brakes contrary to the
driver's intentions.
4.2.1.10 The service, secondary and parking braking systems shall act on braking surfaces
connected to the wheels through components of......
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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