The present invention refers to a test bench for testing turbocharger assemblies particularly but not exclusively useful for carrying out balancing and/or flow tests of turbocharger assemblies.

For the purposes of the present description, the term turbocharger assembly generically means an assembly comprising a shaft at the opposite ends of which a turbine rotor and a compressor rotor are respectively fixed and the portion of which interposed between the two rotors is rotatably supported by one or more support elements by means of at least one bearing, for example a bush.

The turbocharger assembly as described above is known in the jargon as "core assy" or "cartridge" and is subjected to balancing tests, in order to perform which the shaft is set in rotation by compressed air.

The turbocharger assembly, moreover, can be completed with a first and a second volute-shaped housing in which the turbine rotor and the compressor rotor are respectively housed, which are known in the jargon of the field as turbine casing and compressor casing, respectively.

The turbine casing, as known, is equipped with an inlet opening for inletting the exhaust gases of an endothermal motor, which gases, in test conditions, are replaced by pressurised air and that give up their energy to the turbine rotor setting it in rotation, and with an outlet opening for outletting the exhaust gases or pressurised air.

The compressor casing, as known, is equipped with an inlet opening for inletting ambient air, which is sucked in by the compressor rotor during rotation, and with an outlet opening for outletting the ambient air thus compressed.

The turbocharger assembly is not described any further since it is of the type known to the person skilled in the art .

Known test benches generally comprise a work table on which means for supporting the turbocharger assemblies being tested, and the measuring instrumentation necessary for detecting relevant magnitudes for the balancing and/or flow tests, are mounted, defining a work area.

Moreover, means for supplying pressurised air, means for supplying lubricating oil and means for purging oil are provided.

The work table is generally surrounded by perimeter walls that delimit the work area and make a base structure .

The work area of the test bench is usually covered, before carrying out the test, by a dome or protective cover that is fixed to the work table, more specifically to the base structure formed by the perimeter walls, through closing means, in order to isolate the work area and protect the operator from possible risks for own safety.

The closing means most commonly used are electromechanical closing devices, per se known in the state of the art, which can be mounted inside or outside the protection dome and that can be operatively associated with locking and/or unlocking buttons.

In the latter case, at the end of the test step, the electromechanical closing device can be unlocked by actuating the relative button allowing the protection dome to open.

Alternatively, the electromechanical closing device can be configured to unlock automatically at the end of the test step.

The electromechanical closing devices currently used in known test benches remain forcibly closed in the absence of electrical power supply.

For this reason, such electromechanical closing devices can usually be unlocked manually with the help of unlocking tools or special keys. In both cases, it is nevertheless necessary for a technician to intervene, technician who is capable of carrying out the unlocking manoeuvres that in some cases can also be very complex. Moreover, it is not always possible for a technician to be available in a short time and this results in the operations of the workshop being slowed down.

The purpose of the present invention is to avoid the aforementioned drawbacks and in particular to devise a test bench for turbocharger assemblies that allows quick and easy opening of the protection dome in case of absence of electric power without necessarily needing the intervention of a technician.

This and other purposes according to the present invention are accomplished by making a test bench for testing turbocharger assemblies as outlined in claim 1. Further characteristics of the test bench for testing turbocharger assemblies are the object of the dependent claims . The characteristics and advantages of a test bench for testing turbocharger assemblies according to the present invention will become clearer from the following description, given as an example and not for limiting purposes, referring to the attached schematic drawings, in which:

- figure 1 is a schematic perspective view of a test bench for turbocharger assemblies according to the present invention with the protection dome in the closed position;

- figure 2 is a schematic perspective view of the test bench for turbocharger assemblies of figure 1 with the protection dome in the open position.

With reference to figures 1 and 2, a test bench for turbocharger assemblies is shown, wholly indicated with 10.

The test bench 10 comprises a work table 11 on which measuring instruments 13 and support means 12 for supporting a turbocharger assembly under test are mounted, defining a work area.

The support means 12 are preferably mounted on a base body 29 supported in an elastically yielding manner on the work table in order to be able to allow the detection of anomalous vibrations in the case of balancing tests.

The measuring instruments 13 comprise a plurality of probes and sensors adapted for making detections useful for balancing and/or flow tests, for example sensors (not illustrated) for detecting the vibrations of the turbocharger assembly under test associated with the base body 29, and sensors for detecting the number of revolutions 13 of the rotor of the turbocharger assembly under test. The measuring instruments are also connected to processing and display units like a dedicated personal computer that can be integrated in the test bench itself 10 outside the perimeter of the work table 11.

The test bench 10 preferably comprises perimeter walls that surround the work table and the work area making a base structure 22, as illustrated in figures 1 and 2. The test bench 10 also comprises means for supplying pressurized air 14 and means for supplying lubricant 15a, for example oil, for lubricating the support bearings of the rotor of the turbocharger assembly under test, and means for purging lubricant 15b.

The test bench 10 also comprises connection means 16, for example flexible tubes, to connect the outlet mouth of the turbine casing of the turbocharger assembly under test with a silencer (not illustrated) associated with the test bench itself.

The means for supplying pressurized air 14 comprise at least one compressed air tank (not illustrated) and a compressor (not illustrated) that can be actuated electrically and one or more air conveying tubes 14 that reach the work area to be coupled with the turbocharger assembly under test (turbine inlet side) . The means for supplying lubricant 15a comprise at least one pump (not illustrated) connected to a conveying tube 15a for the lubricant that reaches the work area to be coupled with the turbocharger assembly under test so as to be able to lubricate the bearings that support the rotor in rotation.

The lubricant purging means 15b comprise a solenoid valve (not illustrated, incorporated in the test bench) operatively connected to an injection tube 15b for allowing the injection of compressed air into the circuit for supplying lubricant 15a so as to purge the lubricant from the core assy under test, said lubricant thus returning into a collection tank (not illustrated, incorporated in the test bench 10) .

The means for supplying air 14, the means for supplying lubricant 15a and the means for purging lubricant 15b are not described any further since they are of the type known to the person skilled in the art.

The test bench 10 also comprises a protection dome or cover 17 arranged to assume a closed position in which it is arranged above the work table 11 covering the work area and an open position in which the work area is freely accessible.

The protection dome or cover 17 is preferably of the pivoted type, like the one illustrated in figures 1 and 2, i.e. associated directly or indirectly with the work table 11 in a rotating manner about a hinging axis so as to be able to rotate reversibly from the open position to the closed position.

The protection dome 17, therefore, can be hinged to the work table 11 or to the base structure 22 made by the perimeter walls that surround the table itself.

The test bench 10 also comprises closing means 18, 19 to fix the protection dome 17 in the closed position. According to the present invention the closing means comprise at least one electromagnetic closing device 18, 19 adapted to be connected to an electrical power supply line and configured to pass, during normal operation and in case of absence of electric power supply, from a locked position, in which it holds the protection dome 17 in the closed position, to an unlocked position, in which it leaves the protection dome 17 free to be taken into the open position.

The electromagnetic closing device 18, 19, therefore, unlocks automatically in the case of absence of electrical power supply.

Preferably, the at least one electromagnetic closing device 18, 19 comprises a plate of ferromagnetic material 18 and an electromagnet 19 associated directly or indirectly one with the protection dome 17 and the other with the work table 11 or vice-versa so as to come into contact with one another when the protection dome 17 is in the closed position. For example, if the ferromagnetic plate 18 is fixed to the protection dome 17 the electromagnet 19 can be fixed to the work table 11 or to the base structure 22. Vice-versa, if the electromagnet 19 is fixed to the protection dome 17 the ferromagnetic plate can be fixed to the work table 11 or to the base structure 22.

When the protection dome 17 is arranged in the closed position and the electromagnet 19 is supplied with electricity, it generates a magnetic attraction force that holds the ferromagnetic plate 18 in contact thus bringing the electromagnetic closing device 18, 19 into the locked position.

In case of absence of electric power supply, the electromagnet 19 stops exerting the attraction force towards the ferromagnetic plate 18 taking the closing device automatically into the unlocked position in a delay time interval that depends essentially on the demagnetisation time of the electromagnet 19.

Preferably, the test bench 10 comprises a first control button 20 configured to interrupt, when it is pressed, the power supply of the electromagnetic closing device 18, 19 taking the latter into the unlocked position. The first control button 20 is, therefore, capable of opening the connection between the electromagnetic closing device 18, 19 and the electrical power supply line only until it remains pressed. As soon as the first control button 20 is released, the electromagnetic closing device 18, 19 is power supplied again and, if the electromagnet 19 and the ferromagnetic plate 18 are close to or in contact with one another, it assumes the locked position thus keeping the protection dome 17 in the closed position. Preferably, the test bench 10 comprises at least one pair of electromagnetic contacts 21 associated directly or indirectly one with the protection dome 17 and the other with the work table so as to come into contact with each other when the protection dome 17 is in the closed position, and a control circuit (not illustrated) configured to stop the operation of the means for supplying pressurized air 14, of the means for supplying lubricant 15a and of the means for purging lubricant 15b when the protection dome is taken into the open position and the electromagnetic contacts 21 move apart from one another.

For example, one of the two electromagnetic contacts 21 can be fixed to the work table 11 or to the base structure 22.

In particular, the electromagnetic contacts 21 are preferably of the cigarette type, but more generally they can be of any type and of any shape. The term electromagnetic contacts of the cigarette type is meant to indicate cylinder-shaped contacts having the diameter of the cross section smaller than the longitudinal length.

In the case in which the protection dome 17 is of the pivot type, the test bench 10 preferably comprises at least one pair of thrusting elements, preferably of the gas spring type 23, associated directly or indirectly with the protection dome 17 and with the work table 11 and configured to dampen the passage from the open position to the closed position of the protection dome 17 and to assist the automatic opening of the protection dome 17 when the electromagnetic closing device 18, 19 is in unlocked position. For example, the thrusting elements 23 can be fixed on one side to the protection dome 17 and on the other side to the work table 11 or to the base structure 22.

In order to take the protection dome 17 automatically into the open position, the first control button 20 must stay pressed for at least the time necessary for the ferromagnetic plate 18 to move away from the electromagnet 19 by an extent such as not to allow the interaction thereof.

In the opposite case, when the first control button 20 is released before the aforementioned time period, the electromagnetic closing device 18, 19 goes back into locked position keeping the protection dome 17 in the closed position.

Still in the case in which gas springs 23 are present, the first control button 20 can also be connected to the aforementioned control circuit configured, when the button is pressed, to stop the operation of the means for supplying lubricant 15a within the delay time interval of the electromagnetic closing device 18, 19 to pass from the locked position to the unlocked position .

In addition, preferably, the control circuit is also configured to actuate the means for purging lubricant 15b so as to carry out the purging of the lubricant up to the moment when the electromagnetic contacts 21 move apart from one another ceasing to interact with each other due to the opening of the protection dome 17. This happens by keeping the first button 20 pressed and in sequence after the stopping of the means for supplying lubricant 15a.

In this way it is possible to stop the means for supplying lubricant 15a and purge the lubricant itself from the turbocharger assembly under test by actuating the means for purging lubricant 15b when the protection dome 17 is in the closed position of the work area. When the first control button 20 is released before the ferromagnetic plate 18 and the electromagnet 19 move apart from one another so as not to interact with each other, the electromagnetic closing device 18, 19 goes back into the locked position keeping the protection dome 17 in the closed position.

This is very useful because it allows test launches to be carried out in continuous sequence, as desired, in a short space of time.

The test bench 10 also comprises a second control button 26 for actuating and stopping the means for supplying air 14 in automatic mode and a control lever 27 for actuating and stopping the means for supplying air 14 in manual mode; in this case, the test bench 10 also comprises a launch mode selector 25 to select the manual or automatic mode to actuate and stop the means for supplying air 14. The actuation and stopping of the means for supplying air 14 in manual mode, with the control lever 27, is very useful for the oil seal test of the turbocharger assembly at extremely low revs of the rotor; indeed, the critical point of the possibility of oil leaking from the oil sealing bands of the turbocharger assembly actually occurs at low speeds of the rotor.

The test bench 10 is also provided with a third control button 24 for actuating the means for supplying lubricant 15a that only operates in the test step and only with protection dome 17 closed. In this way, after having pressed and released the first control button 20 so as to stop the means for supplying lubricant 15a and keep the protection dome 17 in the closed position, it is possible to press the third control button 24 to carry out a subsequent test. These operations can, therefore, be repeated cyclically to carry out the desired number of tests.

The test bench 10 also comprises a fourth control button (or emergency button) 28 that still offers the possibility of immediately interrupting the general electric and pneumatic power supply of the bench; in this case, the electromagnetic closing device 18, 19 is also unlocked and thus the protection dome 17 does not remain forcibly closed, but can be easily brought into the open position even automatically if the gas springs are provided. Preferably, moreover, the closing means also comprise a safety mechanical closing device (not illustrated) able to be actuated manually, for example a key latch. From the description that has been made the characteristics of the test bench for testing turbocharger assemblies object of the present invention are clear, just as the relative advantages are also clear.

Indeed, thanks to the presence of the electromagnetic closing device that unlocks automatically in the case of sudden absence of electrical power supply, the protection dome does not remain forcibly closed, but can be easily brought into the open position, even automatically if the gas springs are provided.

In this way time and money are saved, since it is no longer necessary to require the intervention of a technician to open the dome.

Finally, it is clear that the test bench for turbocharger assemblies thus conceived can undergo numerous modifications and variants, all of which are encompassed by the invention; moreover, all of the details can be replaced by technically equivalent elements. In practice, the materials used, as well as the sizes, can be whatever according to the technical requirements .