JP6027318B2 - Multistage supercharging system - Google Patents

Description

  The present invention relates to a multistage turbocharging system including a plurality of stages of turbochargers.

  In recent years, a turbocharging system with two stages of turbochargers has been proposed in order to improve fuel efficiency, increase torque and achieve a high EGR rate in the low speed and light load range. As shown in FIG. 3, the high-pressure turbine 2 is operated by the exhaust G sent from the engine exhaust manifold 1 and the intake air A compressed by the high-pressure compressor 3 is sent to the engine intake manifold (not shown) via the intercooler 4. The high-pressure stage turbocharger 5 to be fed, and the low-pressure stage turbine 6 that is operated by the exhaust G sent from the high-pressure stage turbine 2 of the high-pressure stage turbocharger 5 and the intake air A compressed by the low-pressure stage compressor 7 And a low-pressure stage turbocharger 8 for feeding to the vehicle. 3 denotes an air cleaner that removes dust and dirt from the outside air and guides them to the low-pressure compressor 7 as clean intake air A.

  Thus, in such a two-stage turbocharging system, when the engine is in an operating state, after the exhaust G sent from the exhaust manifold 1 flows into the high-pressure turbine 2 and drives the high-pressure compressor 3, The intake air A that flows into the low-pressure turbine 6 and drives the low-pressure compressor 7 and flows into the low-pressure compressor 7 and is compressed is supplied to the high-pressure compressor 3 and is compressed again by the high-pressure compressor 3. Since it is fed to the intake manifold of the engine via the intercooler 4, it is possible to increase the amount of intake A delivered to each cylinder of the engine and increase the fuel injection amount per cycle. As a result, the engine output can be increased.

  The following Patent Document 1 is an example of a general technical level related to the two-stage supercharging system as described above.

JP 2007-71179 A

  However, in such a conventional two-stage turbocharging system, the exhaust G from the engine exhaust manifold 1 is first introduced when accelerating at a large rate of change, such as when suddenly starting from a stop waiting for a signal. The high-pressure turbine 2 to be rotated rotates before the low-pressure turbine 6, and as a result, the low-pressure compressor 7 rotates behind the high-pressure compressor 3. There is a problem that the inside of the intake system passage 10 connecting to the outlet instantaneously becomes negative pressure, and the lubricating oil is sucked out from the bearing of the low-pressure stage turbocharger 8. Repeated over a period of time, the low pressure compressor 7 and the high pressure compressor 3 (leakage of lubricating oil upstream of the intake system is Or led to a caulking to impeller for sound), there is a possibility that impair its performance and reliability.

  As a supplementary explanation, as shown in the graph of FIG. 4, when the accelerator pedal is depressed and the accelerator opening is suddenly increased, the engine speed increases following this, resulting in the rotation of the oil pump driven by the engine. The number of oil pressure increases, and the oil supply pressure of the lubricating oil immediately rises. However, the boost pressure rise by the low pressure compressor 7 rises with a slight delay due to the turbo lag. When the boost pressure on the stage compressor 7 side becomes a negative pressure, the supply hydraulic pressure is already sufficiently high, and the conditions for facilitating the suction from the bearing of the low-pressure stage turbocharger 8 to the low-pressure stage compressor 7 side are established. become.

  Note that the bearing of the low-pressure compressor 7 is provided with a seal ring (not shown) that prevents leakage of lubricating oil from the bearing to the low-pressure compressor 7 side. Since the sealing function is exerted by the action of positive pressure from the low-pressure stage compressor 7 during the supercharging operation, the function of the seal ring is reduced when the pressure inside the housing on the low-pressure stage compressor 7 side becomes negative. There was a fear of doing.

  The present invention has been made in view of the above circumstances, and can prevent the suction of lubricating oil from the turbocharger bearing due to negative pressure in the intake system path between the compressors of each stage during acceleration. It aims at providing a multistage supercharging system.

The present invention provides a multi-stage turbocharging system comprising a plurality of stages of turbochargers, wherein the intake system connecting the compressors of each stage of the turbocharger is opened only when the pressure in the intake system becomes negative, and the intake air The present invention relates to a multi-stage supercharging system characterized in that a check valve that opens a system path to the atmosphere is provided.

  Thus, in this way, when acceleration with a large change rate is performed, such as when suddenly starting from a stop waiting for a signal, the rotation increases in order from the turbine on the upstream side of the exhaust system path. Even if the pressure in the intake system path connecting the compressors at each stage decreases, as soon as negative pressure is generated in the intake system path, the check valve is opened and released to the atmosphere.

  As a result, it is possible to prevent the lubricating oil from being sucked out from the second stage and subsequent turbocharger bearings from the upstream side of the exhaust system passage, and by repeating such sucking out of the lubricating oil over a long period, It is possible to eliminate the risk of coking or impairing the performance and reliability of the turbocharger compressor impeller.

  During normal supercharging operation, the pressure in the intake system connecting the compressors at each stage is positive, so the check valve is closed and the boost pressure is reliably maintained. There is no concern that the efficiency of supercharging will be reduced due to omission.

  Further, in the present invention, a high-pressure stage turbocharger that operates a high-pressure stage turbine by exhaust sent directly from the engine and supplies intake air compressed by a high-pressure stage compressor to the engine, and a high-pressure stage of the high-pressure stage turbocharger The low-pressure stage turbocharger operates the low-pressure stage turbine by exhaust gas sent from the turbine and supplies the compressed air compressed by the low-pressure stage compressor to the high-pressure stage compressor. A check valve may be provided in an intake system path connecting between the outlets of the compressors.

  According to the multistage supercharging system of the present invention described above, various excellent effects as described below can be obtained.

  (I) Even if the pressure of the intake system path connecting the compressors of each stage during acceleration decreases, the check valve of the intake system path is opened and the intake system path is opened to the atmosphere, and between the compressors of each stage Since it is possible to reliably avoid negative pressure in the intake system path, it is possible to prevent the lubricating oil from being sucked out from the second stage and subsequent turbocharger bearings from the upstream side of the exhaust system path. As a result of the fact that the suction is repeated over a long period of time, it is possible to eliminate the possibility of causing caulking to the impellers of the compressors of the turbochargers at each stage and impairing the performance and reliability.

  (II) Since it can be implemented simply by adding a new check valve to the intake system path connecting the compressors of each stage of the turbocharger, the implementation cost can be reduced at a low cost. Remodeling can also be realized without significant cost increase.

It is the schematic which shows an example of the form which implements this invention. It is a graph which shows the relationship between the boost pressure in this example, and the oil supply pressure of lubricating oil. It is the schematic which shows a prior art example. It is a graph which shows the relationship between the boost pressure and the supply oil pressure of lubricating oil in a prior art example.

  Embodiments of the present invention will be described below with reference to the drawings.

  1 and 2 show an example of an embodiment for carrying out the present invention, and portions denoted by the same reference numerals as those in FIG. 3 represent the same items.

In the present embodiment, as in the case of the conventional example of FIG. 3 described above, the high-pressure turbine 2 is operated by the exhaust G sent from the exhaust manifold 1 of the engine and the intake air A compressed by the high-pressure compressor 3 is A high-pressure stage turbocharger 5 that is fed to an intake manifold of an engine (not shown) via a cooler 4, and a low-pressure stage compressor 6 that operates a low-pressure stage turbine 6 by exhaust G that is sent from the high-pressure stage turbine 2 of the high-pressure stage turbocharger 5. A two-stage supercharging system is constituted by the low-pressure stage turbocharger 8 that feeds the intake air A compressed in 7 to the high-pressure stage compressor 3. in the middle of the intake system passage 10 connecting the up, the intake system passage open only when the intake system passage 10 becomes negative pressure 0 is characterized in that provided a check valve 11 which is opened to the atmosphere.

  Thus, in this way, the exhaust G from the exhaust manifold 1 of the engine is first introduced when acceleration with a large change rate is performed, such as when suddenly starting from a stop waiting for a signal. The high-pressure stage turbine 2 rotates before the low-pressure stage turbine 6, whereby the low-pressure stage compressor 7 rotates behind the high-pressure stage compressor 3, so that the interval between the high-pressure stage compressor 3 and the low-pressure stage compressor 7 exits. Even if the pressure of the intake system path 10 connecting the two decreases, as soon as a negative pressure is generated in the intake system path 10, the check valve 11 is opened and released to the atmosphere.

  That is, as shown in the graph of FIG. 2, even if the accelerator is depressed and the accelerator opening is suddenly increased, the boost pressure that rises behind the increase of the engine speed and the supply hydraulic pressure following the accelerator immediately increases. No negative pressure.

  As a result, the lubricating oil is prevented from being sucked out from the bearing of the low-pressure stage turbocharger 8 (the second stage turbocharger from the upstream side of the exhaust system passage), and such a sucking out of the lubricating oil is repeated for a long period of time. As a result, coking of the impeller of the low-pressure compressor 7 and the high-pressure compressor 3 (because the leakage of lubricating oil on the upstream side of the intake system also affects the downstream compressor) causes its performance and reliability. It is possible to eliminate the possibility of damaging.

  During normal supercharging operation, the intake valve 10 that connects between the inlet of the high-pressure compressor 3 and the outlet of the low-pressure compressor 7 is all positive, so the check valve 11 is closed and boosted. The pressure is reliably maintained, and there is no concern that the supercharging efficiency will be reduced due to a pressure drop or the like.

  Therefore, according to the above embodiment, the pressure of the intake system path 10 (the intake system path connecting the compressors in each stage) connecting between the inlet of the high-pressure stage compressor 3 and the outlet of the low-pressure stage compressor 7 during acceleration decreases. Even so, it is possible to reliably prevent the intake system passage 10 from being opened to the atmosphere by opening the check valve 11 of the intake system passage 10 and the negative pressure in the intake system passage 10 being avoided. It is possible to prevent the lubricating oil from being sucked out from the bearings of this type, and the caulking of the impellers of the low-pressure stage compressor 7 and the high-pressure stage compressor 3 is caused by the fact that such sucking out of the lubricating oil is repeated over a long period of time. The possibility of impairing the performance and reliability can be eliminated.

  In addition, since it can be implemented simply by additionally installing a check valve 11 in the intake system passage 10 connecting the inlet of the high-pressure compressor 3 to the outlet of the low-pressure compressor 7, the implementation cost can be reduced at a low cost. The existing equipment can be remodeled without significant cost increase.

  Note that the multistage turbocharging system of the present invention is not limited to the above-described embodiment, and in addition to a two-stage configuration including a high-pressure stage turbocharger and a low-pressure stage turbocharger, a three-stage or more turbocharger system. Of course, it may be composed of a charger, and various changes can be made without departing from the scope of the present invention.

2 High-pressure stage turbine 3 High-pressure stage compressor 5 High-pressure stage turbocharger 6 Low-pressure stage turbine 7 Low-pressure stage compressor 8 Low-pressure stage turbocharger 10 Intake system 11 Check valve A Intake G Exhaust

Claims (2)

In a multi-stage turbocharging system consisting of a multi-stage turbocharger, the intake system path is opened to the intake system path connecting the compressors of each stage turbocharger only when the pressure in the intake system becomes negative, and the intake system path is opened to the atmosphere. A multistage supercharging system characterized by a check valve that opens.   A high-pressure stage turbocharger that operates a high-pressure stage turbine by exhaust gas sent directly from the engine and supplies intake air compressed by a high-pressure stage compressor to the engine, and exhaust gas sent from the high-pressure stage turbine of the high-pressure stage turbocharger A low-pressure stage turbocharger that operates the low-pressure stage turbine and feeds the intake air compressed by the low-pressure stage compressor to the high-pressure stage compressor, and has a structure between the inlet of the high-pressure stage compressor and the outlet of the low-pressure stage compressor. The multistage turbocharging system according to claim 1, wherein a check valve is provided in the intake system path to be connected.

Images