An automated test bench
for automotive gas injectors checkup
An electormagnetic gas injector is the basic metering component of the 4-th generation automotive gas-fuel system.
The identity of the gas injectors determines most of the basic specifications of the vehicle, running on gas: exhaust gases composition, dynamics, idle stability, gas fuel consumption.
The open status time of the gas injector on practice is not definitely proportional to controlling electric impulse duration. The time additionally depends upon many factors. Among these are: pressure drop on the injector, coil inductance and active resistance, core mass, spring resistance, the gap between the core and the seat, the injectors orientation (deviation from vertical) and so on. The identity of these factors must be ensured by the technology. On practice they differ from one injector to another. This results in the dispersion of the behaviors of the injectors being used jointly. The dispersion also depends upon the control impulse duration. That’s why the gas injectors behaviors comparison should be executed in dynamics only and in the conditions under which the injectors work on the engine. The basic conditions are pressure drop presence and controlling electric impulses supply.
There are also some more ‘external’ factors, that determine the injectors behaviors. The basic are:
- the length, the form and the cross section of the pipes that connect the injectors and the inlet manifold;
- the angles under witch the pipes are connected to the inlet manifold;
- the flow areas of the injectors outlet nozzles.
These ‘external’ factors differ in practice from injector to injector and from vehicle to vehicle. That’s why the possibility is important to check the pneumatic routs identities for each a cylinder on the way from pressure regulator to inlet manifold. The gas injectors installed under the bonnet once are hardly accessible after as a rule. It is difficult to extract them for checkup and to install back then. So very desirable is the opportunity to checkup the injectors without their extraction from under the bonnet. The defective injector only can be extracted if detected and replaced or repaired.
So, it is obvious, that compact, fast, highly productive, completely automatic, safety and efficient equipment is needed to fairly check up the vehicle gas injectors in every day work on auto-gas service.
The test bench is meant to checkup automotive gas injectors both alone and directly on a vehicle. During the checkup both safe gas and electric control impulses are supplied to the injectors. The injectors run just as under the bonnet and their supply characteristics are being directly measured as gas consumption via electric impulse duration. The characteristics curves are displayed on the computer monitor and compared automatically. The dispersion of the characteristics is automatically calculated and also can be estimated visually from the screen. Also can be estimated the linearity of the supply characteristics and the control electric impulse minimal duration to open each the injector.
There is ‘motor mode’ in the bench computer program. In the ‘motor mode’ the bench generates control pulses for gas injectors in any desirable mode: sequential, synchronous, coupled… In the ‘motor mode’ the ‘load’ and the ‘rotations’ can be delicately tuned via computer program controls and the gas consumption is being continuously measured. A professional can detect injectors characteristics dispersion even orally in this mode: the sound of the injectors that run under pressure is loud and very distinctive. The ‘motor mode’ can also be used in educational purposes to demonstrate both the 4-th generation automotive gas system and gas injectors functioning.
1. The bench checks normally closed injectors (closed with no electric current in coils).
Coil resistance: 1 Ohm or more.
2. Working gas to be used – any safe and non-aggressive gas:
- compressed air;
- compressed nitrogen;
- evaporated carbon dioxide.
Electrical heater is present to use high input pressures and evaporated carbon dioxide.
3. Input pressure:
- at high pressure input: 10-200bar;
- at low pressure input: 5-7bar with receiver volume 50liters or more and pressure maintaining system.
4. Pressure at the basic output: 1bar.
5. Pressure at the auxiliary output: up to 7bar.
6. Electric control pulses durations range: 1-25ms.
7. Checkup time for 4 injectors: 2.5min (common mode); 6min (precise mode); 30min (high precision mode).
8. Sensitivity: 3 ranges for weak, common and strong signals from injectors with various nozzles diameters.
9. Power supply: 1.5A 220V AC.
10. Personal computer to be used:
- windows XP;
- USB port;
- 800X600 or better screen resolution.
To test new injectors or ones dismounted from a vehicle. The pipe from the basic output being long enough, mounted injectors under the bonnet can also be checked with these connections.
To checkup injectors, mounted on a vehicle. Standard pressure regulator and standard gas supply valve, mounted on the vehicle, are also used and so are also being checked:
1. Test bench inlets, outlets and controls.
1 – heater LED;
2 – power ON LED;
3 – plug for injectors cable connection;
4 – high pressure input;
5 – low pressure input plug;
6 – basic output;
7 – auxiliary output;
8 – power plug;
9 – USB port plug;
10 – plug for standard gas valve control cable connection;
11 – standard gas valve plug fuse;
12 – plug for vehicle ground connection.
2. Test bench in use.
2.1. General view
2.2. Front view
2.3. Back view
2.4. Bottles with carbon dioxide
1. Space adjustment in 4-inj. rail.
Screen video. High resolution, sound.