JP4587923B2 - Turbo compound engine - Google Patents

Description

  The present invention relates to a turbo compound engine.

  Conventionally, a turbocharger that recovers power from exhaust gas and a power turbine that recovers power from exhaust gas that has passed through the turbine of the turbocharger are provided, and the power recovered by the turbocharger is used as supercharging power to pressurize the intake air. A turbo compound engine is known in which power recovered by a power turbine can be effectively used as engine driving force.

  FIG. 3 shows an example of a general turbo compound engine. In the example shown here, the energy of the exhaust gas 3 discharged from the engine body 1 through the exhaust manifold 2 is converted into the turbine 5 of the turbocharger 4. Is recovered as power, and the intake air (not shown) entering the engine body 1 is pressurized by the compressor 6 driven by the turbine 5, while further energy is recovered from the exhaust gas 3 passing through the turbine 5 by the power turbine 7 as power. The recovered power is transmitted to the crankshaft 11 of the engine body 1 via the first gear train 8, the fluid coupling 9, and the second gear train 10, and the exhaust gas 3 passing through the power turbine 7 is an exhaust pipe. 12 is discharged to the outside of the vehicle. In FIG. 3, 13 indicates an exhaust brake, and 14 indicates a flywheel.

  In recent years, such a turbo compound engine has a variable valve mechanism that can arbitrarily change the opening / closing timing and lift of each cylinder valve, and stops the valve opening operation when the vehicle is coasting due to accelerator off. It is considered that the engine friction is lowered to suppress the vehicle speed reduction.

  In other words, in a cylinder in which the valve opening operation is stopped, the valve is kept closed and air is sealed in the cylinder, but this air simply expands and contracts in the cylinder and reduces the output. Will not occur (because the resistance during compression is offset during expansion), rather, the resistance caused by the air going in and out when the valve opening operation is continued (when only fuel injection is cut) is avoided. Therefore, the engine friction is reduced and the speed reduction of the vehicle is suppressed, and the fuel consumption of the vehicle is greatly improved as compared with the prior art.

As prior art document information related to this type of turbo compound engine, there is the following Patent Document 1 and the like.
JP-A-9-2222026

  However, if the valve opening operation of each cylinder is stopped when the accelerator is off in the turbo compound engine as described above, the working fluid (air when the accelerator is off) is used as the driving force of the turbine 5 of the turbocharger 4. Since the rotation of the turbine 5 of the turbocharger 4 is significantly reduced, the turbine 5 of the turbocharger 4 must be driven from the greatly reduced rotational speed when the accelerator is depressed and reaccelerated next time. The turbo lag (time delay until the turbocharger starts to increase due to the actual increase in the amount of exhaust gas at the time of acceleration, etc.) will increase and may cause problems such as deterioration in acceleration and increase in black smoke was there.

  The present invention has been made in view of the above circumstances, and provides a turbo compound engine capable of suppressing turbo lag during re-acceleration even when the valve opening operation of each cylinder is stopped when the accelerator is off. With the goal.

  The present invention includes a turbocharger that recovers power from exhaust gas, and a power turbine that further recovers power from exhaust gas that has passed through the turbine of the turbocharger, and transmits power recovered by the power turbine to a crankshaft. In a turbo compound engine, when the accelerator is off, the valve opening operation of each cylinder is stopped by the valve operation stop means so that inertial running can be performed, branching from the exhaust pipe downstream from the power turbine to the exhaust manifold Characterized in that a bypass passage is provided, a first opening / closing valve is provided in the middle of the bypass passage, and a second opening / closing valve is provided downstream of the bypass passage branching position in the exhaust pipe. It is.

  In this way, when the accelerator is off, the valve opening operation of each cylinder is stopped by the valve operation stop means, and the valve of each cylinder is closed, so that the working fluid (accelerator off) However, sometimes the working fluid is not guided to the power turbine and the power cannot be recovered. However, the power turbine side is opposite to the original power transmission from the crankshaft rotating by inertial running. Power is transmitted to the power turbine to drive the power turbine.

  At this time, if the first on-off valve is opened and the second on-off valve is closed at the same time as the accelerator is turned off, the air remaining in the exhaust system is passed through the bypass passage by the power turbine driven by the inertia traveling. Since the rotation of the turbine of the turbocharger is maintained by the circulating flow of air from the exhaust manifold and is re-accelerated by depressing the accelerator, the turbo lag is greatly suppressed.

  In more specific implementation of the present invention, for example, the valve operation stop means for stopping the valve opening operation of each cylinder when the accelerator is off is constituted by a variable valve mechanism, or the second opening / closing valve is It may also serve as an exhaust brake.

  According to the turbo compound engine of the present invention described above, even if the valve opening operation of each cylinder is stopped in order to reduce engine friction and improve fuel efficiency when the accelerator is off, the bypass passage is opened and the exhaust system is opened. The remaining air can be circulated to the exhaust manifold, and the rotation of the turbocharger turbine can be maintained by the circulating air flow from the exhaust manifold. It can be greatly suppressed, and an excellent effect can be obtained that problems such as deterioration in acceleration and increase in black smoke can be avoided in advance.

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

  FIG. 1 shows an example of an embodiment for carrying out the present invention. In this embodiment, a valve opening operation of each cylinder is described later with respect to a turbo compound engine configured substantially the same as FIG. This is configured so that the inertial running can be performed by being stopped by the valve operation stop means, and a bypass flow path 15 branched from the exhaust pipe 12 downstream from the power turbine 7 to reach the exhaust manifold 2 is provided. 15 is provided with an opening / closing valve 16 (first opening / closing valve), and an exhaust brake 13 (second opening / closing valve) downstream from the branch position of the bypass passage 15 in the exhaust pipe 12.

  Here, the exhaust brake 13 has a function of narrowing the flow path of the exhaust pipe 12 when the accelerator is off and switching the flow of the remaining air in the exhaust system to the bypass flow path 15 side. If it is closed when the accelerator is off under the condition that the valve opening operation is normally performed and the bypass flow path 15 is disconnected, it functions as an exhaust brake, the valve opening operation of the valve is stopped, and the bypass flow path 15 is opened. If it is closed when the accelerator is off under the condition, it functions as a second opening / closing valve for switching the flow path.

  FIG. 2 shows an example of the valve operation stop means employed in the turbo compound engine of this embodiment. The opening / closing timing and lift of the valve 17 (exhaust valve is shown in the figure) can be arbitrarily changed. As a means, a conventionally known variable valve mechanism 18 is employed as a valve operation stop means.

  That is, in the hydraulic variable valve mechanism 18 illustrated in FIG. 2, the camshaft 20 extending in the direction in which the cylinders 19 are arranged is connected to the intake and exhaust cams 21 (exhaust in the drawing) corresponding to the cylinders 19. The rocker shaft 22 extending in parallel in the vicinity of the camshaft 20 is provided with a rocker arm 23 that is tilted by being pushed up by the cam 21 through a roller 23a. Yes.

  Then, one end of the rocker arm 23 pushes up the master piston 25 provided in the upper hydraulic unit 24 to generate hydraulic pressure in the valve opening oil passage 26 drilled in the hydraulic unit 24 to directly above the bridge 31. The slave piston 27 is lowered, and both valves 17 can be opened by the slave piston 27 via the bridge 31 to open the valve.

  Here, the valve opening oil passage 26 in the hydraulic unit 24 is connected via a three-way solenoid valve 28 (hydraulic supply means) for switching between holding and releasing the oil pressure of the valve opening oil passage 26. An oil supply passage 29 is connected, and hydraulic oil 30 fed by an unillustrated engine-driven oil pump is introduced into the valve opening oil passage 26 to fill the valve opening oil passage 26, and when the master piston 25 is in operation. The opening and closing timing and the lift of the valve 17 can be adjusted by appropriately switching the holding and opening of the hydraulic pressure in the valve opening oil passage 26 and controlling the follow-up timing and operation amount of the slave piston 27.

  That is, when the master piston 25 is operated, if the solenoid valve 28 holds the hydraulic pressure of the valve opening oil passage 26, the slave piston 27 immediately operates following the operation of the master piston 25. If the oil pressure of the valve opening oil passage 26 generated by the operation of the valve 25 is released to the accumulator or the like by switching the solenoid valve 28, the slave piston 27 will not follow even if the master piston 25 is operated. The amount of operation can be reduced, and furthermore, the valve opening operation of the valve 17 can be completely stopped.

  Thus, when the vehicle is in a normal driving state except when it is desired to apply braking by the exhaust brake 13 on a long downhill or the like, and when it is desired to suppress a decrease in vehicle speed during inertial driving for the purpose of improving fuel efficiency, the accelerator is off. (Even if the accelerator off is not directly detected by an accelerator sensor or the like, the engine control computer [ECU: Electronic Control Unit] may be used to determine the fuel injection stop signal in the fuel injection control system) If the solenoid valve 28 of the variable valve mechanism 18 is kept open to the accumulator, the slave piston 27 does not follow even if the master piston 25 is operating, and as a result, the valve opening operation of the valve 17 in each cylinder 19 is stopped. As a result, the valve 17 of each cylinder 19 is closed and the working fluid (air when the accelerator is off) is energized. It will no longer be discharged from the down main body 1.

  As a result, since the working fluid does not enter the turbine 5 of the turbocharger 4 in FIG. 1, the working fluid is not guided to the power turbine 7 and the power cannot be recovered. Power is transmitted to the power turbine 7 side through the second gear train 10, the fluid coupling 9, and the first gear train 8 in the opposite direction to the power transmission, and the power turbine 7 is driven.

  At this time, if the open / close valve 16 is opened and the exhaust brake 13 is closed simultaneously with the accelerator off, the air remaining in the exhaust system is exhausted via the bypass passage 15 by the power turbine 7 driven by the inertia traveling. 2, and the rotation of the turbine 5 of the turbocharger 4 is maintained by the circulating flow of air from the exhaust manifold 2, so that the turbo lag when the accelerator is depressed and re-accelerated next time is greatly suppressed. Become.

  Therefore, according to the above embodiment, even if the opening operation of the valve 17 of each cylinder 19 is stopped in order to improve the fuel consumption by reducing the engine friction when the accelerator is off, the bypass passage 15 is opened and the exhaust system is opened. The remaining air can be circulated to the exhaust manifold 2, and the rotation of the turbine 5 of the turbocharger 4 can be maintained by the circulating flow of air from the exhaust manifold 2. In this case, the turbo lag can be greatly suppressed, and problems such as deterioration in acceleration and increase in black smoke can be avoided in advance.

  The turbo compound engine according to the present invention is not limited to the above-described embodiment. The valve operation stopping means may be any variable as long as it can stop the valve opening operation of each cylinder. The valve mechanism may not be used as a valve operation stop means, and the second opening / closing valve does not necessarily have to be used as an exhaust brake, and may be provided separately from the exhaust brake, Of course, various modifications can be made without departing from the scope of the present invention.

It is the schematic which shows an example of the form which implements this invention. It is sectional drawing which shows an example of the valve operation stop means employ | adopted as this form example. It is the schematic which shows a prior art example.

Explanation of symbols

2 exhaust manifold 3 exhaust gas 4 turbocharger 5 turbine 7 power turbine 11 crankshaft 12 exhaust pipe 13 exhaust brake (second on-off valve)
15 Bypass flow path 16 Open / close valve (first open / close valve)
17 Valve 18 Variable valve mechanism (valve operation stop means)
19 cylinders

Claims (3)

  In a turbo compound engine comprising: a turbocharger that recovers power from exhaust gas; and a power turbine that further recovers power from exhaust gas that has passed through the turbine of the turbocharger, wherein the power recovered by the power turbine is transmitted to a crankshaft. The bypass passage that opens from the exhaust pipe downstream from the power turbine and reaches the exhaust manifold is configured such that when the accelerator is off, the valve opening operation of each cylinder is stopped by the valve operation stop means and coasting can be performed. And a first open / close valve in the middle of the bypass flow path, and a second open / close valve downstream of the bypass flow path branch position in the exhaust pipe.   2. The turbo compound engine according to claim 1, wherein the valve operation stop means is constituted by a variable valve mechanism.   The turbo compound engine according to claim 1, wherein the second opening / closing valve also serves as an exhaust brake.

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