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Common Rail Test Bench Design Principles

- May 21, 2018 -

What is a common rail test rig? As the name suggests, the test rig is a basic gantry for inspection tests. This gantry must realistically simulate the operating characteristics and fuel parameters of a common rail system under a specific working environment. The common rail injector test bench is the basic bench for simulating the real working characteristics of the common rail injector on the engine.

To realistically simulate the operating characteristics of the common rail injector on the engine, it is necessary to first meet the installation requirements of the injector on the vehicle, that is, a firm connection and no leakage. Secondly, the working procedure of the fuel injector solenoid valve on the engine is consistent with that of the test bench. That is, the process of the test bench controlling the solenoid valve of the injector is the same as the process and method of the ECU controlling the solenoid valve on the vehicle, because of the work of the solenoid valve. The process and response time affect the lift of the control valve, the pressure of the control chamber, the lift of the needle valve, and the injection rate, and directly affect the injection quantity of the injector. The opening time of the needle valve lift lags behind the opening time of the control valve lift and also lags behind the current opening time. In other words, parameters such as the on-time of the current directly affect the lift of the needle valve and ultimately affect the amount of injection and the time of injection.

However, the control of injector solenoid valves is a very difficult matter, both speed and accuracy. It is very difficult to control the level of ECU and it is difficult to meet the requirements of current waveform control.

The value of IPK1, the value between IB+ and IB-, the value between IS+ and IS- are all critical, and the time of the T1, T2, T3, T4, T5 segments must also be precisely controlled in microseconds. To meet the above requirements, the solenoid valve of the injector can be properly driven to meet the requirements of the ECU control process. This is also the most basic requirement for a common rail injector test rig.

In order to meet the solenoid valve control requirements of the injector, there is still another point that must be satisfied in the design of the test bench. That is the stability of the rail pressure. This stability is not only the stable display of the finger, but the actual pressure in the common rail. The stability can be detected with precision-grade ultra-high pressure gauges or electronic rail pressure gauges. If the rail pressure is not stable, the accuracy of the tested oil quantity is doubtful.

The above-mentioned solenoid valve control method and rail pressure stability are the most basic two points of the test bench. The other is the accuracy of the test oil and the filtering accuracy of the filter element, including the cleanliness of the pipeline and the temperature control stability. Things to think about. After the above design requirements are met, the injector database must be taken into consideration. The database can currently only use the databases of foreign advanced test benches. However, no matter which database is used, the control method and accuracy of the test benches must be tested. Taiwan is basically the same, or else it is impossible to meet the test conditions of the database. It's like we are running in the race. If the foreign players use the 100-foot mark distance, we use the 100-meter mark distance. If we do not convert the distance units, but use the second to calculate who is faster or slower, then there is no comparable. So whoever uses the database has to adopt who controls and achieves a certain degree of control accuracy.