Turbo charger arrangement for an internal combustion engine

In a turbocharger arrangement for an internal combustion engine including an exhaust gas turbine with an exhaust gas pressure control valve (waste gate) and an operating motor for opening or closing the waste gate, wherein a charger is coupled to the turbine and has a suction side and a discharge side in communication with the engine for supplying charge air thereto and wherein a system control valve is provided which is in communication with the suction side and with the pressure side of the charger and also with the waste gate operating motor for supplying suction air pressure or discharge air pressure to the waste gate operating motor, the system control valve includes means for placing the suction air side of the charger in communication with the charger air discharge side for returning charger discharge air to the suction side of the charger.

BACKGROUND OF THE INVENTION 
The invention relates to a turbo charger arrangement for an internal 
combustion engine with a system control valve for operating a motor 
connected to a waste gate for controlling the engine exhaust gas pressure 
separately from an air return valve for returning compressed air through a 
short circuit line from the charger discharge side to the charger inlet 
side. 
FIG. 1 shows schematically a turbocharger control arrangement of Bosch for 
a turbocharged engine wherein a system control valve for controlling the 
operating motor for an exhaust gas waste gate is arranged separately from 
an air return circuit. The system control valve includes a first control 
line extending from the air intake pipe at the suction side of the charger 
to the system control valve includes a first control line extending from 
the air intake pipe at the suction side of the charger to the system 
control valve. A second control line extends from the system control valve 
to the discharge side of the charger and a third control line extends from 
the system control valve to the operating motor for actuating the waste 
gate. 
In a first control position of the system control valve, the operating 
motor of the waste gate is in direct communication with the suction side 
of the charger. In a second control position, the discharge side of the 
charger is in communication with the operating motor of the waste gate. 
When the engine is driven by the vehicle, the air return valve is opened 
whereby air discharged from the charger is returned to the charger inlet 
side. The air return valve is controllable by way of a separate control 
line. 
Such an arrangement for controlling turbocharged engines under the various 
operating conditions has the disadvantage that it requires a large number 
of components and an extensive connecting line arrangement for the 
interconnection of the components. 
It is the object of the present invention to provide a simple and 
relatively inexpensive turbocharger control arrangement for operating a 
turbocharged internal combustion engine under various operating 
conditions. 
SUMMARY OF THE INVENTION 
In a turbocharger arrangement for an internal combustion engine including 
an exhaust gas turbine with an exhaust gas pressure control valve (waste 
gate) and an operating motor for opening or closing the waste gate, 
wherein a charger is coupled to the turbine and has a suction side and a 
discharge side in communication with the engine for supplying charge air 
thereto and wherein a system control valve is provided which is in 
communication with the suction side and with the pressure side of the 
charger and also with the waste gate operating motor for supplying suction 
air pressure or discharge air pressure to the waste gate operating motor, 
the system control valve includes means for placing the suction air side 
of the charger in communication with the charger air discharge side for 
returning charger discharge air to the suction side of the charger. 
Since in the arrangement according to the invention the system control 
valve assumes also the functions of an air return valve, no additional air 
return valve is needed and also the space normally occupied by the air 
return valve is available. The function of the return valve is 
incorporated into the system control valve. This permits the elimination 
of a substantial number of building components which makes the arrangement 
according to the invention less expensive. For example, by the elimination 
of the return air valve also the control line for controlling the return 
valve is eliminated whereby the turbocharger arrangement is simplified. 
Furthermore, examination and maintenance of the arrangement is 
facilitated. Also, the arrangement is less trouble prone and easier to 
service and repair since only one system control valve is used. 
The invention will be described below in greater detail on the basis of the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
To facilitate understanding of the arrangement according to the invention, 
first a prior art arrangement is described with reference to FIG. 1, which 
is a schematic representation of part of a turbocharger control 
arrangement for a tubocharged internal combustion engine. The engine which 
is not shown in the figure, includes a charger 11, having a suction side 
with an air suction pipe 12 connected to an air mass flow meter 13. 
Downstream of an impeller 14, the charger 11 is connected to an engine 
intake duct 16 which leads to the internal combustion engine. The impeller 
14 is directly connected by means of a drive shaft 17 to a turbine 18 
which is disposed in the exhaust system 19 of the engine. Engine exhaust 
gas is supplied to the turbine 18 by way of an engine exhaust pipe 21 
Which is provided with a bypass line 23 for bypassing the turbine 18. The 
bypass line 23 includes an exhaust gas pressure control valve 22 (waste 
gate) for controlling the exhaust gas flow bypassing the turbine 18. The 
waste gate 22 is controllable by way of an operating motor 26 which is in 
communication with a system control valve 27. 
The system control valve 27 includes a first control line 28 which 
communicates with the air suction pipe 12 up-stream of the charger 11. 
Furthermore, the system control valve includes, opposite the first control 
line 28, a second and third control line 29 and 30. The second control 
line 29 extends to the pressure side of the charger 11 where it is 
connected to the intake duct 16. The third control line 30 extends to the 
waste gate operating motor 26. The system control valve further is 
provided with an electrical connection 31 by way of which the system 
control valve 27 receives control signals from an engine electronic 
control unit. 
The system control valve is a 3/2 way valve which has a first control 
position in which the first control line 28 is placed in communication 
with the third control line 30 so that the air suction pipe pressure is 
applied to the operating motor 26. In a second control position 42 of the 
system control valve, the second control line 29 is placed in 
communication with the third control line 30 so that the air pressure at 
the discharge side of the charger is applied to the operating motor 26. 
From the air intake duct 16, an air return pipe 33 branches off and rejoins 
the suction pipe 12. The air return pipe 33 includes a return air flow 
control valve 32 which is controllable via a control line 34. When the 
return air flow valve 32 is opened a short circuit is established between 
the suction side and the discharge side of the charger 11. 
FIG. 2 is a schematic partial view of a turbocharger arrangement for an 
internal combustion engine which includes many of the same components 
which have been described in connection with FIG. 1 and which are 
indicated by the same reference numerals and not again described in 
detail. In the arrangement according to the invention as shown in FIG. 2, 
there is provided, in contrast to the arrangement of FIG. 1, a 3/3 way 
system control valve 40 which includes first and second control positions 
41 and 42 corresponding to those of the system control valve 27 described 
in connection with FIG. 1. There is, however, a third control position 43 
in which the first control line 28, which is connected to the air suction 
pipe 12, is placed in communication with the control line 29 which is 
connected to the discharge side of the charger 11. In this manner, a short 
circuit can be established between the pressure and the suction sides of 
the charger 11 through the system control valve 40. Consequently, the 
return air flow control valve 32 and the control line 34 therefor as shown 
in FIG. 1 are eliminated as air return flow can be established through the 
system control valve 40. This reduces the amount of components needed and 
provides for a simplified turbocharger control arrangement. The system 
control valve is still operated by signals from the engine control unit 
which oversees and manages engine operation.