JP5684041B2 - Internal combustion engine with a supercharger - Google Patents

Description

  The present invention relates to a supercharged internal combustion engine including a first supercharger for intake air and a second supercharger for EGR gas.

  In a diesel engine, a turbocharger including a turbine inserted into an exhaust line and a compressor inserted into the intake line while being driven by the turbine is widely used to use exhaust energy for supercharging. Yes.

  In a diesel engine, at least part of the exhaust gas in the exhaust line is returned to the intake line, thereby reducing the combustion temperature and reducing NOx, and delaying the time until ignition to mix the fuel and air. EGR (exhaust gas recirculation) is also widely used.

  For example, Patent Document 1 below discloses a diesel engine provided with a variable displacement supercharger for EGR gas (VGT for EGR) in addition to a variable displacement supercharger for intake air (supercharging VGT). Has been.

  The configuration described in Patent Document 1 is useful in that the supercharging pressure and the EGR pressure can be individually controlled by the supercharging VGT and the EGR VGT, but has the following disadvantages.

  That is, in the configuration described in Patent Document 1, the turbocharger VGT turbine inserted in the exhaust line and the EGR VGT compressor inserted in the EGR line are connected in parallel to the exhaust manifold. Has been.

  In such a configuration, when the amount of EGR gas is increased, the amount of exhaust gas passing through the turbine of the supercharger VGT is reduced, and the exhaust energy recoverable by the supercharger VGT is reduced. .

  In Patent Document 1, the EGR line in which the EGR VGT compressor is inserted has an upstream end connected to the exhaust manifold and a downstream end connected to the intake manifold.

  In such a configuration, the compressor of the EGR VGT needs to pressurize the high-pressure exhaust gas from the exhaust manifold more than the intake pressure, and there is a problem that it is difficult to secure a sufficient amount of EGR gas.

  In particular, when an exhaust gas aftertreatment device such as an exhaust gas purification device (diesel particulate filter) or a heat exchanger is inserted in the EGR line, the pressure at the downstream end of the EGR line decreases. Therefore, a sufficient amount of EGR gas cannot be supplied to the intake manifold.

Japanese Patent No. 4049366

  The present invention has been made in view of such conventional technology, and is a supercharged internal combustion engine including a first supercharger for intake air and a second supercharger for EGR gas, While being able to supply the EGR gas amount, the exhaust gas can be effectively recovered by the first supercharger regardless of the increase or decrease of the EGR gas amount, and further, the supercharging capable of increasing or decreasing the EGR gas amount with good responsiveness. An object is to provide an internal combustion engine with a machine.

  In order to achieve the above object, the present invention provides an internal combustion engine body, an intake line that guides intake air to a combustion chamber of the internal combustion engine body, an exhaust line that serves as a passage for exhaust gas discharged from the combustion chamber, A first turbocharger having a first turbine inserted in the exhaust line and a first compressor inserted in the intake line while being driven by the first turbine, and an exhaust gas flow direction from the first turbine A second turbocharger having a second compressor driven by a second turbine and a front second turbine inserted in the exhaust line on the downstream side, and the first turbine and the second turbocharger with respect to the exhaust gas flow direction. An intermediate portion between the two turbines is connected to the exhaust line, and the other end is connected to the intake line upstream of the first compressor in the intake air flow direction. The EGR line in which the second compressor is inserted, one end connected to the intermediate part of the exhaust line, and the other end connected to the exhaust line downstream in the exhaust gas flow direction from the second turbine. A bypass control line, a first control valve inserted in the bypass line, a second control valve inserted in the EGR line downstream of the second compressor in the EGR gas flow direction, and one end portion of which is EGR An EGR discharge line connected to the EGR line between the second compressor and the second control valve with respect to the gas flow direction and having the other end connected to the exhaust line downstream of the second turbine in the exhaust gas flow direction. And a supercharged internal combustion engine comprising a third control valve inserted in the EGR release line.

  Preferably, the internal combustion engine with a supercharger may further include an exhaust gas aftertreatment device inserted in an EGR gas flow direction upstream side of the second compressor in the EGR line.

  More preferably, the internal combustion engine with a supercharger may further include a fourth control valve inserted in the EGR gas flow direction upstream side of the exhaust gas aftertreatment device in the EGR line.

  According to the internal combustion engine with a supercharger according to the present invention, the exhaust gas discharged from the combustion chamber of the internal combustion engine body is supplied to the first turbine of the first supercharger for intake air and passes through the first turbine. Since at least a part of the exhaust gas is returned to the intake line via the EGR line, the entire amount of exhaust gas discharged from the internal combustion engine body passes through the first turbine regardless of the increase or decrease of the EGR gas amount. Therefore, it is possible to recover the exhaust energy by the first supercharger as effectively as possible regardless of the increase or decrease in the amount of EGR gas.

  Furthermore, according to the internal combustion engine of the present invention, the exhaust gas discharged from the combustion chamber of the internal combustion engine body is directly pressurized by the second compressor of the second supercharger for EGR gas, and the intake manifold Rather than returning to, at least a portion of the exhaust gas discharged from the combustion chamber and driving the first turbine of the first supercharger is pressurized by the second compressor of the second supercharger. Since the intake line is configured to be supplied to the upstream side in the intake air flow direction from the first compressor of the first supercharger, without increasing the size and performance of the second supercharger. If necessary, a sufficient amount of EGR gas can be supplied to the intake line.

  Further, according to the internal combustion engine according to the present invention, by controlling the first control valve, the rotational speed of the second turbine of the second supercharger is changed, and the second control valve is controlled. Since the EGR line pressure can be changed by changing the opening width of the EGR line and controlling the third control valve, the amount of EGR gas supplied to the intake line via the EGR line is responsive. Can increase or decrease well.

  If an exhaust gas aftertreatment device is provided upstream of the second compressor in the EGR gas flow direction in the EGR line, the EGR gas can be purified in a relatively low pressure state before being pressurized by the second compressor. Therefore, it is possible to improve the durability of the exhaust gas aftertreatment device itself while improving the durability of the internal combustion engine body and the second compressor by purifying EGR gas.

  If a fourth control valve is further provided on the upstream side of the exhaust gas aftertreatment device in the EGR line in the EGR gas flow direction, the exhaust gas can be supplied when the EGR gas does not need to be recirculated to the intake line. Intrusion into the exhaust gas aftertreatment device can be prevented, and further durability of the exhaust gas aftertreatment device can be improved.

FIG. 1 is a block diagram of an internal combustion engine with a supercharger according to an embodiment of the present invention. FIG. 2 is an example of a control flowchart in the internal combustion engine shown in FIG.

Hereinafter, an embodiment of an internal combustion engine with a supercharger according to the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a schematic diagram of an internal combustion engine 1 with a supercharger according to this embodiment.

  As shown in FIG. 1, the internal combustion engine 1 serves as an internal combustion engine body 10, an intake line 20 that guides intake air to a combustion chamber of the internal combustion engine body 10, and a passage for exhaust gas discharged from the combustion chamber. The exhaust line 30, the first supercharger 40 for intake air, the second supercharger 50 for EGR gas, and at least a part of the exhaust gas in the exhaust line 30 are used as EGR gas to the intake line 20. And an EGR line 60 for returning.

The internal combustion engine body 10 is configured to supply fuel to compressed air for combustion, and to obtain rotational power from the expansion energy generated by the combustion.
The internal combustion engine body 10 includes a cylinder block including a cylinder and a piston, and a cylinder head connected to the cylinder block so as to close an opening of the cylinder, and the cylinder, the piston, and the cylinder head A combustion chamber is defined.

The cylinder head is provided with a fuel injection valve that injects fuel into the combustion chamber.
The fuel injection valves are provided in the same number as the number of the combustion chambers, and fuel is supplied from the respective combustion injection valves to the corresponding fuel chambers.
By controlling the amount of fuel injected by the fuel injection valve, the output rotational speed and torque of the internal combustion engine body are changed.

The intake line 20 includes an intake manifold 21 and an intake pipe 22.
The intake manifold 21 is a member for evenly distributing intake air to a plurality of combustion chambers, and is fixed to the cylinder head.
That is, the intake manifold 21 has one end connected to the intake pipe 22 and the other end branched to the same number as the combustion chambers and connected to a plurality of combustion chambers.

The intake pipe 22 is disposed on the most upstream side in the intake air flow direction, and a downstream end is connected to one end of the intake manifold 21.
Preferably, an air cleaner is inserted in the intake pipe 22.

The exhaust line 30 includes an exhaust manifold 31 and an exhaust pipe 32.
The exhaust manifold 31 is a member that collects exhaust gas discharged from the combustion chamber, and is fixed to the cylinder head.
That is, the exhaust manifold 31 has one end branched to the same number as the combustion chamber, connected to the plurality of combustion chambers, and the other end connected to the exhaust pipe 32.

  The exhaust pipe 32 is disposed on the most downstream side in the exhaust gas flow direction, and an upstream end is connected to the other end of the exhaust manifold 31.

  The first supercharger 40 includes a first turbine 41 inserted into the exhaust line 30 so as to receive the entire amount of exhaust gas discharged from the combustion chamber of the internal combustion engine body 10, and the first turbine 41. And a first compressor 42 inserted in the intake line 20 in a state driven by the compressor.

  In the present embodiment, as shown in FIG. 1, an intercooler 25 is inserted in the intake line 20 downstream of the first compressor 42 in the intake air flow direction.

  The second supercharger 50 is driven by the second turbine 51 and the second turbine 51 inserted into the exhaust line 30 on the downstream side of the first turbine 41 in the exhaust gas flow direction. And a second compressor 52 inserted in the line 60.

  One end of the EGR line 60 is connected to the exhaust line 30 at an intermediate portion 30a between the first turbine 41 and the second turbine 51 in the exhaust gas flow direction, and the other end is connected to the first compressor 42. It is connected to the intake line 20 on the upstream side in the intake air flow direction.

  Thus, in the present embodiment, the entire amount of exhaust gas discharged from the internal combustion engine body 10 is first flowed into the first turbine 41 of the first supercharger 40, and the first turbine 41 At least a part of the exhaust gas that has passed through is returned to the intake line 20 via the EGR line 60.

  According to such a configuration, the entire amount of exhaust gas discharged from the internal combustion engine body 10 is supplied to the first turbine 41 regardless of the increase or decrease of the EGR gas amount. Therefore, as much exhaust energy as possible can be recovered by the first supercharger 40 regardless of the increase or decrease in the amount of EGR gas.

  Further, in the present embodiment, the exhaust gas discharged from the internal combustion engine main body 10 and having a relatively low pressure after driving the first turbine 41 is sent out of the intake line 20 through the EGR line 60. The pressure is returned to the low pressure region 20a upstream of the first compressor 42 in the intake air flow direction.

  According to such a configuration, a sufficient amount of EGR gas as needed is supplied to the intake air without requiring an increase in size and performance of the second supercharger 50 that pressurizes the EGR gas in the EGR line 60. Return to line 20.

  Further, since it is not necessary to pressurize the EGR gas to be higher than the intake pressure of the internal combustion engine body 10, an exhaust gas aftertreatment device such as an exhaust gas purifying device (diesel particulate filter), an oxidation catalyst, or a scrubber is provided in the EGR line 60. Even if a heat exchanger is inserted, the amount of EGR gas as required can be easily secured.

  In the internal combustion engine 1 according to the present embodiment, as shown in FIG. 1, an exhaust gas aftertreatment device 65 is inserted in the EGR line 60 upstream of the second compressor 52 in the EGR gas flow direction, as shown in FIG. Has been.

  According to such a configuration, the exhaust gas aftertreatment device 65 purifies the EGR gas in a relatively low pressure before being pressurized by the second compressor 52, and the exhaust gas aftertreatment is performed. The durability of the device 65 can be improved.

  Further, as shown in FIG. 1, the internal combustion engine 1 according to the present embodiment includes first and second EGR lines 60 that are respectively inserted upstream and downstream of the second compressor 52 in the EGR gas flow direction. And second EGR coolers 66 and 67.

  As shown in FIG. 1, the internal combustion engine 1 according to the present embodiment further has one end connected to the intermediate portion 30 a of the exhaust line 30 and the other end from the second turbine 51. A bypass line 70 connected to the exhaust line 30 on the downstream side in the direction, a first control valve 81 inserted in the bypass line 70, and the EGR line 60 on the downstream side in the EGR gas flow direction from the second compressor 52. A second control valve 82 interposed between the second compressor 52 and the second control valve 82 with respect to the direction of EGR gas flow, and the other end is connected to the second control valve 82. An EGR discharge line 75 connected to the exhaust line 30 on the downstream side in the exhaust gas flow direction from the turbine 51 and the EGR discharge line 75 And a third control valve 83.

The internal combustion engine 1 according to the present embodiment can increase or decrease the amount of EGR gas with good responsiveness by including such a configuration.
In the present embodiment, as shown in FIG. 1, one end portion of the bypass line 70 is downstream in the exhaust gas flow direction from the connection point between the intermediate portion 30 a of the exhaust line 30 and the EGR line 60. However, it is of course possible to connect the intermediate portion 30a upstream of the connection point in the exhaust gas flow direction.

  That is, by controlling the first control valve 81 inserted in the bypass line 70, the intermediate portion 30a of the exhaust line 30 (between the first and second turbines 41 and 51 in the exhaust gas flow direction). The pressure of the portion located) can be adjusted, whereby the rotation speed of the second turbine 51 can be changed, and the degree of pressurization of the EGR gas can be changed.

  Further, the opening width of the EGR line 60 can be adjusted by controlling the second control valve 82, and the pressure of the EGR line 60 can be adjusted by controlling the third control valve 83.

  Specifically, when the amount of EGR gas is increased, the first and third control valves 81 and 83 are throttled to increase the pressure of the EGR line 60 and the second control valve 82 is opened. To widen the opening width of the EGR line 60.

  Conversely, when reducing the amount of EGR gas, the pressure of the EGR line 60 is lowered by opening the first and third control valves 81, 83 and the second control valve 82 is throttled. The opening width of the EGR line 60 is narrowed.

  Preferably, the internal combustion engine 1 according to the present embodiment detects an operating state detection sensor 91 that detects an operating state of the internal combustion engine body 10 and an EGR gas amount that is returned from the EGR line 60 to the intake line 20. An EGR gas amount detection sensor 92 and a control device (not shown), and the control device performs the first to first operations based on signals from the operation state detection sensor 91 and the EGR gas amount detection sensor 92. The three control valves 81 to 83 can be configured to perform operation control.

  Specifically, the control device includes a calculation unit (CPU) including a control calculation unit that executes calculation processing based on signals input from the sensors 91 and 92, and a ROM that stores a control program, control data, and the like. , An EEPROM in which the set values are not lost even when the power is turned off and the set values can be rewritten, and a RAM that temporarily stores data generated during the calculation by the calculation unit Including a storage unit.

As the EGR gas amount detection sensor 92, for example, a CO ₂ sensor can be used.
The operating state detection sensor 91 can take various forms as long as the operating state of the internal combustion engine body 10 can be detected. In the present embodiment, a rotation speed sensor that detects the output rotation speed of the internal combustion engine body 10 is used as the operating state detection sensor 91, but an accelerator opening sensor, a boost pressure sensor, or the like is used. You can also.

The control device has EGR control data for calculating a target EGR gas amount based on a signal from the operating state detection sensor 91 as the control data stored in the storage unit.
The EGR control data is, for example, a control conversion formula or LUT (Look Up Table).

  The control device has an EGR control program for performing operation control of the first to third control valves 81 to 83 based on signals from the operation state detection sensors 91 and 92 as the control program.

FIG. 2 shows a flowchart of an example of the EGR control program.
For example, the EGR control program is started in response to the start of driving of the internal combustion engine body 10.

  In step 10, the control device calculates an EGR gas amount target value based on the signal from the operating state detection sensor 91, and in step 11 acquires an EGR gas amount current value based on the signal from the EGR gas amount detection sensor 92. To do.

  Then, the control device determines in step 12 whether or not the current value is below the target value. If YES, the control device shifts to step 20, and if NO, the control device shifts to step 13.

  If YES in step 12, that is, if it is determined that the current value of EGR gas is lower than the target value of EGR gas amount, the control device, in step 20, the first and third control valves 81, 83 is throttled and the second control valve 82 is opened to increase the amount of EGR gas supplied from the EGR line 60 to the intake line 20.

  In the case of NO in step 12, the control device determines whether or not the current value exceeds the target value in step 13, and proceeds to step 30 in the case of YES.

  In the case of NO in step 13, assuming that the current value matches the target value, the states of the first to third control valves 81 to 83 are maintained as they are.

  If YES in step 13, that is, if it is determined that the EGR gas amount current value exceeds the EGR gas amount target value, the control device, in step 30, the first and third control valves 81, 83 is opened and the second control valve 82 is throttled to reduce the amount of EGR gas supplied from the EGR line 60 to the intake line 20.

As described above, the internal combustion engine 1 according to the present embodiment includes the exhaust gas aftertreatment device 65 inserted in the EGR line 60.
In such a configuration, preferably, as shown in FIG. 1, the EGR line 60 further includes a fourth control valve 84 inserted upstream of the exhaust gas aftertreatment device 65 in the EGR gas flow direction. Can do.

  According to such a configuration, exhaust gas enters the exhaust gas after-treatment device 65 by closing the fourth control valve 84 when it is not necessary to circulate the EGR gas to the intake line 20. Thus, the durability of the exhaust gas aftertreatment device 65 can be improved.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 10 Internal combustion engine main body 20 Intake line 30 Exhaust line 30a Middle part 40 of exhaust line 1st supercharger 41 1st turbine 42 1st compressor 50 2nd supercharger 51 2nd turbine 52 2nd compressor 60 EGR line 65 Exhaust gas aftertreatment device 70 Bypass line 75 EGR release line 81 First control valve 82 Second control valve 83 Third control valve 84 Fourth control valve

Claims (3)

  An internal combustion engine body, an intake line for introducing intake air to a combustion chamber of the internal combustion engine body, an exhaust line serving as a passage for exhaust gas discharged from the combustion chamber, a first turbine interposed in the exhaust line, and the A first turbocharger having a first compressor inserted in the intake line in a state driven by the first turbine; and a first turbocharger inserted in the exhaust line downstream of the first turbine in the exhaust gas flow direction. A second turbocharger having a second compressor driven by two turbines and a front second turbine, and one end portion in the exhaust line at an intermediate portion between the first turbine and the second turbine in the exhaust gas flow direction The other end is connected to the intake line upstream of the first compressor in the intake air flow direction, and the second compressor is inserted. An EGR line, a bypass line having one end connected to the intermediate portion of the exhaust line and the other end connected to the exhaust line downstream of the second turbine in the exhaust gas flow direction, and the bypass line An inserted first control valve, a second control valve inserted in the EGR line downstream of the second compressor in the EGR gas flow direction, and one end portion of the second compressor and the EGR gas flow direction An EGR discharge line connected to the EGR line between the second control valves and having the other end connected to the exhaust line on the downstream side in the exhaust gas flow direction from the second turbine, and the EGR discharge line. And a third control valve. An internal combustion engine with a supercharger.   2. The supercharged internal combustion engine according to claim 1, further comprising an exhaust gas aftertreatment device that is inserted upstream of the second compressor in the EGR gas flow direction in the EGR line.   The internal combustion engine with a supercharger according to claim 2, further comprising a fourth control valve inserted in the EGR line upstream of the exhaust gas aftertreatment device in the EGR gas flow direction.

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