JP4746389B2 - Supercharging system - Google Patents

Description

  The present invention relates to a supercharging system suitable for a vehicle-mounted engine.

  In recent years, exhaust gas diverted from the engine exhaust path is cooled by an EGR cooler (EGR: Exhaust Gas Recirculation), which is a water-cooled tubular heat exchanger, and then returned to the engine intake path to lower the combustion temperature and reduce NOx generation. Exhaust gas recirculation is generally performed.

  In order to increase the output of the engine without changing the exhaust capacity, it is necessary to increase the fuel injection amount per cycle and increase the supercharging pressure by the turbocharger to increase the amount of intake air supplied to the cylinder.

  Further, in order to achieve a high EGR rate without reducing the amount of intake air supplied, it is necessary to increase the supercharging pressure using a turbocharger.

Conventionally, in order to improve the responsiveness during acceleration, it has been proposed to incorporate an electric supercharger in the engine intake path separately from the turbocharger (see, for example, Patent Document 1).
JP 2004-278430 A

Along with the increase in EGR , when the engine is operated at full load in a low speed range, there is a problem that the operation line of the compressor is close to the surge region. In addition, in order to ensure responsiveness and exhaust gas recirculation amount during transient operation such as acceleration, an intake air amount assist with a small turbo lag is required.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a supercharging system that can cope with compressor surge avoidance, energy recovery, and supercharging assistance during acceleration.

In order to achieve the above object, the present invention provides a turbocharger that operates a turbine by exhaust gas sent from an engine and supplies intake air compressed by a compressor to the engine, and a recirculation piping from the discharge port to the intake port of the compressor. And a flow control valve incorporated in the recirculation piping, an electric supercharger incorporated in the recirculation piping, capable of supplying the intake air sucked from the intake passage of the compressor to the engine, and having a power generation function, A check valve that stops intake air from the recirculation piping toward the discharge port of the compressor when the electric supercharger is activated, and a control unit;
The control unit is
By adjusting the opening of the flow rate adjustment valve and the rotational speed of the electric supercharger,
When the actual intake amount is insufficient, the electric supercharger is activated to supply the intake air drawn from the compressor intake path to the engine.
Before the operating status of the compressor enters the surge region, part of the intake air discharged from the compressor is returned from the compressor discharge port to the suction port through the recirculation piping, and electric supercharging is performed with the intake air passing through the recirculation piping at this time. It is configured to demonstrate the power generation function of the machine.

  When the actual intake amount of the engine is insufficient, the control unit operates the electric supercharger and supplies the shortage of intake air to the engine from the recirculation piping.

Before the compressor enters the surge region, the intake air is returned from the discharge port of the compressor to the suction port by recirculation piping to prevent the surge of the compressor. At this time, the control unit causes exert a power generation function of the electric supercharger, perform energy recovery.

  According to the supercharging system of the present invention, the following excellent effects can be obtained.

  (1) When the actual intake air amount of the engine is insufficient, the control unit activates the electric supercharger and supplies the intake air shortage to the engine separately from the compressor. Secured and can respond to acceleration of the vehicle.

(2) Before the compressor enters the surge region, the recirculation piping returns the intake air from the discharge port of the compressor to the intake port, thereby preventing the compressor surge. At that time, the control unit can exhibit the power generation function of the electric supercharger and recover the energy of the intake air passing through the recirculation piping.

  (3) In addition, the differential pressure between the compressor outlet pressure and the turbine inlet pressure is not reduced, and the recirculation amount of the exhaust gas passing through the EGR pipe is ensured even in a high load operation at a low speed, thereby achieving a high EGR rate. It becomes possible.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIGS. 1 and 2 show an example of a supercharging system according to the present invention. Intake A of an engine 1 is obtained by operating a turbine 3 by exhaust G sent from an exhaust manifold 2 of an in-vehicle engine 1 and compressing the intake A by a compressor 4. A turbocharger 6 for feeding to the manifold 5, an intercooler 7 for cooling the intake air A from the compressor 4 to the intake manifold 5, a recirculation pipe 8 from the air discharge port of the compressor 4 to the air intake port, and the recirculation The flow rate adjusting valve 9 incorporated in the distribution pipe 8, the electric supercharger 10 having a power generation function, the control unit 11, the pressure sensors 12, 13, and 14, the flow rate sensors 15 and 16, and the rotational speed sensors 17 and 18. A temperature sensor 19, an EGR pipe 20 extending from the exhaust manifold 2 to the intake manifold 5, and the EGR And a R EGR cooler 21 incorporated in the pipe 20 and the EGR valve 22.

  The air discharge port of the compressor 4 incorporates a check valve 23 for stopping the intake air A from the recirculation pipe 8 toward the compressor 4 when the electric supercharger 10 is operated.

  The electric supercharger 10 is accompanied by an inverter 24, and the inverter 24 operates the electric supercharger 10 at a rotation speed corresponding to the booster rotation speed Nb transmitted from the control unit 11. Or the electric power generation amount of the electric supercharger 10 is adjusted so that it may become the rotation speed suitable for the generator rotation speed Ng transmitted from the control unit 11.

  The control unit 11 performs control of the electric supercharger 10 and the flow rate adjusting valve 9 following steps S1 to S9 of the flowchart shown in FIG.

  In step S1, a command for opening degree Nv = 1 (fully open) is transmitted to the flow rate adjusting valve 9, and a command for booster rotation speed Nb = 0 is transmitted to the inverter 24 at the same time so that the electric supercharger 10 is in a standby state. Keep on.

  In step S2, after starting the engine 1, information on the actual intake air amount Ga by the flow sensor 15, information on the fuel flow rate Gf by the flow sensor 16, and information on the engine speed Ne by the rotation sensor 17 are read. The information on the fuel flow rate Gf can be substituted by a calculated value calculated from the engine speed Ne and the accelerator opening obtained by another sensor.

  In step S3, the target intake air amount Gat is calculated based on the information on the fuel flow rate Gf and the information on the engine speed Ne, and the target intake air amount Gat and the actual intake air amount Ga are compared.

  Step S4 targets the actual intake air amount Ga <the target intake air amount Gat (when the intake air amount is insufficient).

  Here, the booster rotational speed Nb of the electric supercharger 10 required to compensate for the difference ΔGa between the actual intake air amount Ga and the target intake air amount Gat is obtained, and a command for the booster rotational speed Nb is transmitted to the inverter 24.

  In other words, the electric turbocharger 10 is operated at a rotational speed corresponding to the booster rotational speed Nb, and the target intake air amount Gat is ensured, which can cope with acceleration of the vehicle (see FIG. 1).

  Step S5 is targeted for the actual intake air amount Ga ≧ target intake air amount Gat (when the intake air amount is secured).

  Here, information on the turbine rotational speed Nt by the rotation sensor 18, information on the boost pressure Pb by the pressure sensor 12, information on the atmospheric pressure Patm by the pressure sensor 13, information on the compressor inlet pressure Pi by the pressure sensor 14, compressor by the temperature sensor 19 Information on the inlet temperature Ti is read.

In step S6, the boost flow rate Gab is calculated from the information on the turbine speed Nt, the information on the boost pressure Pb, the information on the atmospheric pressure Patm, and the information on the compressor inlet pressure Pi , and the surge flow rate Gas is calculated on the information on the boost pressure Pb and the atmospheric pressure Patm. And the boost flow rate Gab and the surge flow rate Gas are compared with each other.

  Step S7 is targeted for boost flow rate Gab <surge flow rate Gas (when entering the surge region).

  Here, the generator rotational speed Ng is obtained from the boost pressure Pb and the compressor inlet pressure Pi, and a command for the generator rotational speed Ng is transmitted to the inverter 24.

  Further, a command for the opening degree Nv corresponding to the difference ΔGab between the surge flow rate Gas and the boost flow rate Gab is transmitted to the flow rate adjustment valve 9.

  That is, the energy of the intake air A that is adjusted through the recirculation pipe 8 from the air discharge port of the compressor 4 to the air intake port is adjusted so that the electric power generation amount of the electric supercharger 10 is adjusted so as to match the generator rotation number Ng. In addition, the surge of the compressor 4 is prevented and it is possible to cope with full load operation in a low rotation speed range (see FIG. 2).

Further, the differential pressure between the outlet pressure of the compressor 4 and the inlet pressure of the turbine 3 is not reduced, and the recirculation amount of the exhaust G passing through the EGR pipe 20 is ensured even in a high load operation at a low rotation speed.

  Step S8 reads the signal Sig of the key switch (not shown) for the boost flow rate Gab ≧ surge flow rate Gas (when not in the surge region) or after the execution of the above-described steps S4 and S7.

  In step S9, it is determined whether the signal Sig = 1 (ON) or the signal Sig = 0 (OFF). If it is ON, the process returns to the above-described step S2.

  Note that the supercharging system of the present invention is not particularly limited only to the above-described embodiment, and it is needless to say that changes can be made without departing from the gist of the present invention.

  The supercharging system of the present invention can be applied to various internal combustion engines.

It is a conceptual diagram which shows an example (acceleration state) of the supercharging system of this invention. It is a conceptual diagram which shows an example (low-speed-range full load driving | running state) of the supercharging system of this invention. It is a flowchart of the control unit relevant to FIG.1 and FIG.2.

Explanation of symbols

1 Engine 2 Exhaust manifold (exhaust path)
3 Turbine 4 Compressor 5 Intake manifold (intake path)
6 Turbocharger 8 Recirculation piping 9 Flow control valve 10 Electric supercharger 11 Control unit 20 EGR piping 21 EGR cooler 22 EGR valve 22 Recirculation piping 23 Recirculation piping A Intake G Exhaust

Claims (2)

The turbocharger that operates the turbine by exhaust gas sent from the engine and supplies the intake air compressed by the compressor to the engine, the recirculation piping from the discharge port of the compressor to the intake port, and the recirculation piping An electric supercharger that is incorporated in the flow rate adjusting valve and the recirculation pipe and that can supply intake air sucked from the intake path of the compressor to the engine and has a power generation function, and a recirculation when the electric supercharger is in operation. A check valve that stops intake air from the piping to the compressor outlet, and a control unit.
The control unit is
By adjusting the opening of the flow rate adjustment valve and the rotational speed of the electric supercharger,
When the actual intake amount is insufficient, the electric supercharger is activated to supply the intake air drawn from the compressor intake path to the engine.
Before the operating status of the compressor enters the surge region, part of the intake air discharged from the compressor is returned from the compressor discharge port to the suction port through the recirculation piping, and electric supercharging is performed with the intake air passing through the recirculation piping at this time. A supercharging system characterized in that the power generation function of the machine is exhibited . 2. The supercharging system according to claim 1, wherein an EGR pipe extending from an upstream side of a turbine in an engine exhaust path to a downstream side of a compressor in an engine intake path is provided, and an EGR cooler and an EGR valve are incorporated in the EGR pipe .

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