With yearly increase in global car ownership and human awareness of environmental protection, pollution emissions from vehicles are increasingly affected by the world's attention, the development of world emissions regulations are more stringent. As the Environmental Protection Agency requires a more accurate method to detect emissions caused by rising engine performance problems, OBD (On-BoardDiagnostic: on-board diagnostic) system came into being. Latest second-generation on-board diagnostic system is one of the effective means to monitor vehicle emissions. The most important point is that the design of the system is the second generation on-board diagnostic system is designed to detect vehicle exhaust emissions HC, CO, NOx and fuel evaporative emission value exceeds the emission limits. The system does not replace the regular OBD emissions test, but will play the role of monitor vehicle emissions. The EU as a responder vehicle emissions regulations in the near future, China must implement EOBD (EuropeanOn-BoardDiagnostic: Europe on-board diagnostic system).
One, OBD System Overview
System development process 1.OBD
OBD systems experienced OBD I (first-generation on-board diagnostic system) and OBD II (second generation on-board diagnostic system), EOBD2 stages. OBD I was first used by the U.S. state of California in 1991, features a relatively simple, mainly complete failure diagnosis and emissions-related components. OBD I no uniform standard, most OBD connector socket, fault codes and other forms of content in different communication protocols, to electric car fault diagnosis and repair a lot of inconvenience. The second stage OBD II, EOBD system is very complex. OBD II, EOBD emission-related components in addition to the complete failure of the diagnosis, but also due to the aging of components for excessive emissions, in part due to the failure to diagnose. Therefore, OBD II, EOBD system is to achieve a real sense of the emissions in the range of control over the life of the car. OBD II, EOBD using uniform standards, as long as a single instrument can perform diagnostic tests on a variety of vehicles, which gives the global automotive maintenance detection provides great convenience.
Because the United States and Europe, using two different emission regulations, so the second-generation on-board diagnostic system OBD II, EOBD two forms. U.S. implementation of OBD II, and the use of European countries to implement emission regulations EOBD system. From the source, the American OBD II system implemented earlier and more stringent standards. EPA regulations in 1996 after the production of cars and light trucks (load at 6.5t or less) of electronically controlled systems require configuration OBD II system and start all car manufacturers cars and light trucks in the January 1, 2000 are you must configure the OBD II system. In 1998, Canada implemented OBD II system. Europe began the gradual implementation from 2000 EOBD system in 2001 all new production of cars in Europe (Load 2.5t or less) is limited to the gasoline engine configuration EOBD system, and the requirements for diesel engine cars to the 2004 mandatory EOBD system configuration. In the relevant provisions of the Central European emissions regulations no OBD II our current standard has been promulgated in, but with the implementation of the Euro Ⅲ standard, EOBD use certainly on the agenda.
2.OBD system works
Cars in normal operation, the automobile electronic control system signal input and output (voltage or current) will change regularly with a certain range; electronic control circuit when the signal is abnormal and beyond the normal range of variation, and this anomaly does not disappear at a certain time (three continuous stroke) within, ECU determines that a failure of this part, the fault indicator lamp is lit while the fault monitor in the form of code stored in the internal RAM ( RandomAccessMemory: Random Access Memory), is the fault code stored in the maintenance can be read by the fault indicator lights or OBD2 scanner. If the fault is no longer present, the monitor after three consecutive times to the relevant signal is not received, the command displays the fault light goes out. Fault indicator light turns off after engine warm cycle about 40 times, the fault code will automatically be removed from memory.
The main features of the system 3.OBD
OBD II compared with OBD I, the biggest improvement is that OBD II has a uniform standard, which gives the fault diagnosis and testing and maintenance electric cars offer a lot of convenience. In 1988, SAE (Society of American Engineers) created the first fault diagnostic connector jack and a fault code as a standard promotion, the EPA adopted as the standard SAE recommended for most standard and unified worldwide use. All OBDII EOBD equipment or vehicles must include the following hardware and software standardization: standardized data diagnostic interface (SAE-J1962), standardized decoder (SAE-J1978), standardized electronic communication protocol (kW2000, CAN, CLASSII, ISO9141 etc.), standardized diagnostic trouble codes (DTC, SAE-J2012), standardized intelligence service (SAE-J2000).
Detection object two, OBD systems
OBD II required to detect any emission-related component or system. Focuses on the detection of fuel and air measurement system failure, intermittent ignition system failure or engine flameout failure, auxiliary emission control device failure.
Limitations of three, OBD systems
1.OBD system can not measure vehicle emissions CO, NOx and HC, etc., just play the role of monitor vehicle emissions. So, if you need an accurate analysis of vehicle exhaust emissions status, still need other means of monitoring or with other exhaust gas analyzer.
System reliability 2.OBD affected vehicles operating environment, in certain work situations, such as harsh operating conditions and abnormal operating environment, OBD system may be wrong, this time to suspend the work of the general OBD system. And the wrong fault indication OBD system will reduce the credibility of the user, so that some users will disregard the OBD fault warning issued after that OBD proper function can not be achieved.
3.OBD system does not indicate how the vehicle repairs, it can only be real-time monitoring of vehicles, the detected faults in the form of code stored in memory, to light the lamp failure to notify the driver or indicate faulty parts there is a fault diagnosis, to remind the driver of the vehicle to be repaired.
4.OBD system can not diagnose all faults within the automotive electronic control system, it can only monitor the automotive electronic control systems 70% to 80% of the failures. Relying only way fault indicator can not effectively judge the deterioration of automotive systems.
5.OBD system software brings a huge challenge. OBD software is about half of the entire electric car software. Any one software error can lead to erroneous fault indication or violation. The accuracy of the software, even though 99.9 percent accuracy will still cause a lot of system problems.
In addition, there are many difficulties on the OBD system software and testing, such as too sensitive, too sensitive and accurate detection is not so.
OBD is a very complex self-diagnostic system for detecting faults affect vehicle emissions components and systems. The purpose of the OBD system is to determine whether the components or sub-systems due to the failure cause emissions to exceed the maximum value. Currently, the domestic automobile emissions control system is basically mature products directly from abroad, domestic OBD field of research is still in its infancy. Due to increasingly stringent vehicle emissions regulations, OBD will be referred to a very important position. With the continuous improvement of emission regulations, the Chinese government is bound to develop strict OBD regulations controlling emission levels in cars. Despite the limitations OBD system also some aspects, but it is currently on the true meaning of the emissions in the range of control over the life of the car. With the implementation of Euro III emission regulations, delphi ds150e OBD automotive industry has become a hot topic.