JP2016061248A - Internal combustion engine and control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine which improves supercharging characteristics by shortening a turbo lag at acceleration, and can highly efficiently operate a supercharger over the whole region of an engine operation, and a control method of the internal combustion engine.SOLUTION: An internal combustion engine 10 which has a two-stage supercharging system 20 comprises a variable valve train mechanism 18 which can make the valve-closing timing of an intake valve 17a retard, and can make the whole of a valve-opening period of an exhaust valve 17b advance. A control device 30 which controls the variable valve train mechanism 18 performs intake-valve retardant closing control for making valve-closing timing retard without making the valve-opening timing of the intake valve 17a advance according to an engine rotation speed Ne and target supercharging pressure Pt. Furthermore, the control device performs exhaust-valve early-opening control for making the whole of the valve-opening period of the exhaust valve 17b advance according to the engine rotation speed Ne and the target supercharging pressure Pt at acceleration.SELECTED DRAWING: Figure 3

Description

  The present invention eliminates the need for setting a wastegate on the turbine side, reduces the amount of working gas, can avoid deterioration of pumping loss during high supercharging operation in a wide range of engine operating conditions, and in high supercharging conditions The present invention also relates to an internal combustion engine that can be operated with high efficiency and a method for controlling the internal combustion engine.

  Currently, in a diesel engine mounted on a vehicle, high supercharging operation is indispensable in order to achieve both high engine output and low exhaust gas level, and an exhaust turbo system is applied. In this case, there are problems that cannot be avoided in the system, such as the occurrence of turbo lag (supercharging delay) during acceleration and the increase in exhaust pressure due to high supercharging (high boost).

  In this regard, in order to improve engine start-up / acceleration with respect to an engine turbocharger equipped with a turbocharger, a high-stage pressure small turbocharger and a low-stage pressure large turbocharger are used. A large compressor and a small compressor are arranged in series in the intake passage in order from the upstream side, and the exhaust passage of the engine in which a small turbine and a large turbine are arranged in series from the upstream side in the exhaust passage. A feeding device has been proposed (see, for example, Patent Document 1).

  In this two-stage turbocharging system, it is desirable to use a turbocharger with a relatively small capacity in order to avoid the occurrence of turbo lag during acceleration. However, operating conditions other than when starting, especially the amount of working gas increases. In the high engine speed range, the engine cannot be supercharged with high efficiency, and the exhaust pressure rises excessively, so the engine performance deteriorates. Therefore, it is difficult to solve the turbo lag problem and the exhaust pressure increase problem at the same time.

  That is, FIGS. 13 to 16 show the supercharging pressure and exhaust pressure during full load operation due to the difference in supercharger capacity, and the compressor operating point. At the rated point of the engine where the exhaust gas flow rate is the highest. When the supercharger capacity is set, a relatively large capacity turbo is used as shown in FIGS. However, there is a problem that the supercharging pressure becomes low on the engine low speed side, and the turbo lag (supercharging delay) becomes longer during acceleration.

  On the other hand, as shown in FIGS. 15 and 16, when a relatively low flow type turbocharger is set, the turbo lag (supercharging delay) is shortened, but on the high speed operation side, the supercharging operating point starts from the high efficiency region. Will come off and the exhaust pressure will rise significantly. In addition to this, it is necessary to set a wastegate on the turbine side in order to suppress an increase in supercharging pressure and exhaust pressure during a transition.

JP 2011-214414 A

  The present invention has been made in view of the above, and its purpose is to shorten the turbo lag at the time of acceleration and improve the supercharging characteristics, while leaving the setting of the wastegate on the turbine side unnecessary. It is an object of the present invention to provide an internal combustion engine and a control method for the internal combustion engine that can operate a supercharger with high efficiency over the entire engine operation region.

  Moreover,

  In order to achieve the above object, an internal combustion engine of the present invention is an internal combustion engine equipped with a two-stage supercharging system that can retard the closing timing of the intake valve and advance the entire opening period of the exhaust valve. A control device configured to include a variable valve mechanism capable of turning, and to advance the opening timing of the intake valve according to the engine rotation speed and the target supercharging pressure. Without being configured, the intake valve delay close control is performed to retard the valve close timing.

  According to this configuration, by performing the intake valve slow closing control, the working gas amount is reduced while the setting of the waste gate on the turbine side is unnecessary, and the high supercharging operation is performed under a wide range of engine operating conditions. Since deterioration of the pumping loss can be avoided, it becomes possible to operate with high efficiency even under high supercharging conditions.

  In the internal combustion engine, the control device is configured to perform exhaust valve early opening control for advancing the entire valve opening period of the exhaust valve in accordance with the engine speed and the target boost pressure during acceleration. The

  In addition, by performing exhaust valve early opening control during acceleration, the exhaust enthalpy can be increased instantaneously, the turbine rotational speed can be increased quickly, and the target boost pressure can be reached with a minimum turbo lag. it can.

  Therefore, the turbo lag at the time of acceleration is shortened to improve the supercharging characteristics, and the turbocharger can be operated with high efficiency over the entire engine operating range while eliminating the need for setting the wastegate on the turbine side. Is possible.

  In the internal combustion engine, the control device is configured to increase the retard amount as the target supercharging pressure increases when performing the intake valve delay close control for retarding the valve closing timing of the intake valve. As a result, the effect of the intake valve slow closing control is further increased.

  In the internal combustion engine, when the control device performs exhaust valve early opening control for advancing the entire valve opening period of the exhaust valve, the supercharging pressure is measured, and the measured supercharging pressure and the target supercharging are measured. When the advance amount is increased as the pressure difference increases, the effect of the exhaust valve early opening control is further increased.

  And the control method of the internal combustion engine of the present invention for achieving the above object comprises a two-stage supercharging system, can retard the closing timing of the intake valve, and extends the entire opening period of the exhaust valve. In a control method for an internal combustion engine equipped with a variable valve mechanism that can advance, the valve closing timing is retarded without advancing the opening timing of the intake valve according to the engine speed and the target boost pressure. In this method, the intake valve slow closing control is performed.

  In the internal combustion engine control method, exhaust valve early opening control is performed to advance the entire opening period of the exhaust valve in accordance with the engine speed and the target boost pressure during acceleration. According to these methods, the same effects as the above-described internal combustion engine can be achieved.

  According to the internal combustion engine and the control method of the internal combustion engine of the present invention, the turbo lag at the time of acceleration is shortened by the intake valve slow closing control to improve the supercharging characteristic and the setting of the waste gate on the turbine side is unnecessary. Thus, the supercharger can be operated with high efficiency over the entire engine operation region.

  Furthermore, by performing exhaust valve early opening control during acceleration, the exhaust enthalpy can be increased instantaneously, the turbine rotational speed can be increased quickly, and the target boost pressure can be reached with a minimum turbo lag. it can.

  Therefore, by using both of these controls in combination, the turbo lag at the time of acceleration is shortened to improve the supercharging characteristics, and the setting of the wastegate on the turbine side is made unnecessary, and the entire engine operation range is maintained. It becomes possible to operate the turbocharger with high efficiency

It is a figure showing composition of an internal-combustion engine of an embodiment concerning the present invention. It is a figure which shows the structure of the cylinder periphery of the internal combustion engine of embodiment which concerns on this invention. It is a figure which shows typically the timing of opening and closing of the intake valve and exhaust valve in this invention. It is a figure which shows typically the intake valve late closing control area | region in this invention. It is a figure which shows typically the timing of opening and closing of an exhaust valve and an intake valve in the intake valve late closing control in this invention. It is a figure which shows the relationship between the engine speed of intake valve late closing control in this invention, and the amount at the time of intake valve late closing. It is a figure which shows the relationship between the engine speed at the time of using the intake valve slow closing control in this invention, a supercharging pressure, and exhaust pressure. It is a figure which shows the relationship between the air quantity at the time of using the intake valve late closing control in this invention, and a compressor pressure ratio. It is a figure which shows typically the exhaust valve early opening control area | region in this invention. It is a figure which shows typically the timing of opening and closing of an exhaust valve and an intake valve at the time of acceleration at the time of using the exhaust valve early opening control of this invention. It is a figure which shows typically the timing of opening and closing of an exhaust valve and an intake valve at the time of acceleration by simultaneous use of intake valve late closing control and exhaust valve early opening control in the present invention. It is a figure which shows the example of the improvement of the supercharging response at the time of acceleration by simultaneous use of intake valve late closing control and exhaust valve early opening control in this invention. It is a figure which shows the relationship between an engine speed, a supercharging pressure, and an exhaust pressure at the time of making it match in an engine high-speed rotation area using a high capacity | capacitance supercharger with the supercharging system of a prior art. It is a figure which shows the relationship between the air quantity at the time of using a large capacity | capacitance supercharger with the supercharging system of a prior art, and making it match in an engine high speed rotation area. It is a figure which shows the relationship between an engine speed, a supercharging pressure, and an exhaust pressure at the time of making it match in an engine low speed rotation area using a small capacity | capacitance supercharger with the supercharging system of a prior art. It is a figure which shows the relationship between the air quantity at the time of using a small capacity | capacitance supercharger with the supercharging system of a prior art, and making it match in an engine low speed rotation area, and a compressor pressure ratio.

  Hereinafter, an internal combustion engine according to an embodiment of the present invention and a control method for the internal combustion engine will be described with reference to the drawings.

  As shown in FIGS. 1 and 2, an engine (internal combustion engine) 10 according to an embodiment of the present invention includes an engine body 11, an intake passage 12, an exhaust passage 13, and an EGR passage 14. The engine body 11 includes a cylinder 15, a fuel injection device 16, an intake valve 17 a at a portion communicating with the intake passage 12, an exhaust valve 17 b at a portion communicated with the exhaust passage 13, and these intake valves 17 a. A variable valve timing mechanism 18 having a variable valve timing for opening / closing the exhaust valve 17b is provided. A piston 19 is inserted into the cylinder 15. The engine 10 includes a two-stage turbocharging system 20 including a low-pressure stage turbocharger (turbo-type supercharger) 21 and a high-pressure stage turbocharger 22.

  As shown in FIGS. 1 and 2, air (fresh air) A introduced from the atmosphere is, in the intake passage 12, an air cleaner (not shown), the low-pressure stage compressor 21 a of the low-pressure stage turbocharger 21, and the high-pressure stage turbo. Via the high-pressure compressor 22a of the charger 22, the intercooler 23, the intake manifold 11a of the engine body 11 and the intake valve 17a, the fuel is fed into the cylinder 15 and mixed and compressed with the fuel injected from the fuel injection device 16. When the fuel is ignited and burned, the piston 19 is pushed down, and the crankshaft 19a is rotated to generate power.

  As shown in FIGS. 1 and 2, the exhaust gas G generated by the combustion in the cylinder 15 flows out to the exhaust passage 13 via the exhaust valve 17b and the exhaust manifold 11b, and a part thereof is the EGR cooler 24. And the EGR gas Ge is branched into the EGR passage 14 where the EGR valve 25 is provided, and the remaining exhaust gas Go is purified by an aftertreatment device (not shown) via the high pressure turbine 22b and the low pressure turbine 21b, The purified exhaust gas Go is discharged to the atmosphere via a muffler (not shown).

  Moreover, the control apparatus 30 which controls the engine 10 is provided. The control device 30 is configured to control the intake valve 17a and the exhaust valve 17b via the variable valve mechanism 18 based on information of various sensors provided in the engine 10 or various sensors provided in a vehicle on which the engine 10 is mounted. It is a control device called ECU (engine control unit) that performs general control of the engine 10 and general control of the vehicle, such as opening / closing control, fuel injection control of the fuel injection device 16, and opening degree control of the EGR valve 25.

  In the present invention, as shown in FIGS. 1 and 2, a pressure sensor (MAP sensor: Manifold Absolute Pressure Sensor) 31 for measuring the pressure inside the intake manifold 11a is provided, and the control device 30 controls the pressure. The supercharging pressure Pin can be monitored (monitored) by the sensor 31.

  And in the engine 10 of the high supercharging system provided with these two superchargers 20A and 20B, the variable valve mechanism 18 is configured to take in the intake and exhaust timings of the intake valve 17a and the exhaust valve 17b as shown in FIG. For the valve 17a, the valve closing timing is indicated by the middle line Aa and the thick line Ab without delaying the valve opening timing with respect to the normal valve closing timing (normal cam position: thin line) An. In addition, it is possible to retard. Further, with respect to the exhaust valve 17b, the entire valve opening / closing valve timing is advanced with respect to the normal valve opening / closing valve timing (normal cam position: thin line) as shown by the middle line Ba and the thick line Bb. Configured to be possible.

  Further, in the control of the valve mechanism 18, the control device 30 opens and closes the normal valve closing timing in the intake valve 17 a in the normal valve region Ran based on map data as shown in FIG. 4 set in advance. In the intake valve slow closing control region Rac that is controlled in advance, the supercharging pressure Pin is monitored by the pressure sensor 31, and in accordance with the “engine rotational speed Ne” and the “target supercharging pressure Pt”, As shown in FIG. 5, the intake valve slow closing control for delaying the valve closing timing for retarding the valve closing timing is performed without advancing the valve opening timing of the intake valve 17a. The exhaust valve 17b performs normal opening / closing control of the valve closing timing in both the normal valve region Ran and the intake valve slow closing control region Rac.

  Further, for example, as shown in FIG. 6, the delay closing amount Δθ1, which is the degree of retardation, is controlled so as to increase as the boost pressure Pin increases. The relationship between the supercharging pressure Pin and the slow closing amount Δθ1 can be set in advance through experiments or the like. Although this relationship is shown by a straight line in FIG. 6, it is not necessarily a straight line, and it is preferable to obtain this relationship experimentally.

  For example, the valve opening timing of the intake valve 17a is in the range of 320 degrees (°) ATDC to 370 degrees ATDC as the crank angle, as in the prior art, and the valve closing timing is 540 degrees ATDC from the conventional crank angle. The angle is retarded by about 0 to 100 degrees from the range of 590 degrees ATDC. It should be noted that the lift amount of the intake valve 17a may be maintained or may be different when the valve closing timing is retarded by the mechanism of the variable valve mechanism used.

  Normally, in order to suppress a transient increase in the exhaust pressure Pout under high supercharging operation conditions, it is necessary to provide a wastegate on the exhaust turbine side to suppress the maximum rotation speed. As shown in FIG. 16, it will deviate from the high efficiency operation region. Therefore, in the present invention, by performing the intake valve slow closing control, the operation gas amount is reduced while setting the wastegate on the turbine side is unnecessary, and the operation is performed with high efficiency even under high supercharging conditions. Make it possible. Thereby, deterioration of the pumping loss at the time of high supercharging operation can be avoided in a wide range of engine operating conditions. Therefore, by this intake valve slow closing control, as shown in FIGS. 7 and 8, it is possible to perform high supercharging with high efficiency under a wide range of engine operating conditions, and avoid deterioration of pumping loss.

  Further, in the control of the valve operating mechanism 18, the control device 30 monitors the supercharging pressure Pin with the pressure sensor 31 during acceleration, and based on the preset map data as shown in FIG. 9, the normal valve region Rbn. In FIG. 10, normal normal valve control is performed, but when the exhaust valve is in the early opening control region Rbc, the engine rotational speed Ne and the difference ΔP between the supercharging pressure Pin and the target supercharging pressure Pt are shown in FIG. And as shown in FIG. 11, it is comprised so that the exhaust valve early opening control which advances the whole valve closing timing of the exhaust valve 17a may be implemented. The variable phase amount Δθ2 that is the degree of advance is controlled so as to increase as the difference ΔP between the boost pressure Pin and the target boost pressure Pt increases. The relationship between the difference ΔP between the supercharging pressure Pin and the target supercharging pressure Pt and the variable phase amount Δθ2 can be set in advance by experiments or the like. Although this relationship is shown by a straight line in FIG. 9, it is not always a straight line, and it is preferable to obtain this relationship experimentally.

  FIG. 10 shows the case in the normal valve region Ran (FIG. 4) related to the intake valve, and FIG. 11 shows the case in the intake valve late close region Rac (FIG. 4) related to the intake valve.

  For example, the valve opening timing of the exhaust valve 17b is opened by advancing about 0 to 80 degrees from the range of 120 degrees ATDC to 170 degrees ATDC in the conventional crank angle, and the valve closing timing is the crank angle of the conventional technique. From the range of 360 degrees ATDC to 400 degrees ATDC, the valve is similarly advanced by about 0 degrees to 80 degrees to close the valve. It should be noted that the lift amount of the exhaust valve 17b may be the same or different when the entire valve opening period is advanced by the mechanism of the variable valve mechanism used.

  Usually, in order to minimize the turbo lag during engine acceleration, it is necessary to increase the turbo rotation speed quickly. For this purpose, it is necessary to increase the exhaust enthalpy. Is an effective means for increasing the exhaust enthalpy. At this time, by performing exhaust valve early opening control, as shown in the comparison between the embodiment shown in FIG. 12 and the conventional example, the exhaust enthalpy is shown. Can be increased instantaneously. Therefore, the turbine rotational speed can be quickly increased and the target boost pressure Pt can be reached with the minimum turbo lag, so that the target boost pressure Pt can be obtained quickly. In FIG. 12, an example in which both intake valve slow closing control and exhaust valve early opening control are performed is compared with a conventional example in which both are not performed.

  Therefore, according to the internal combustion engine and the control method for the internal combustion engine having the above-described configuration, the turbo valve is shortened during acceleration to improve the supercharging characteristics by the intake valve slow closing control, and the waste gate is not required to be set on the turbine side. It is possible to operate the supercharger with high efficiency over the entire engine operation region.

  Furthermore, by performing exhaust valve early opening control during acceleration, the exhaust enthalpy can be increased instantaneously, the turbine rotational speed can be increased quickly, and the target boost pressure can be reached with a minimum turbo lag. it can.

  Therefore, by using both of these controls in combination, the turbo lag at the time of acceleration is shortened to improve the supercharging characteristics, and the setting of the wastegate on the turbine side is made unnecessary, and the entire engine operation range is maintained. It becomes possible to operate the turbocharger with high efficiency

10 Diesel engine (compression ignition internal combustion engine)
11 Engine body 11a Intake manifold 11b Exhaust manifold 12 Intake passage 13 Exhaust passage 14 EGR passage 15 Cylinder
16 Fuel injection device 17a Intake valve 17b Exhaust valve 18 Valve mechanism 19 Piston 19a Crankshaft 20 Two-stage supercharging system 21 Low-pressure stage turbocharger (turbo supercharger)
21a Low-pressure stage compressor 21b Low-pressure stage turbine 22 Low-pressure stage turbocharger (turbo supercharger)
22a Low-pressure stage compressor 22b Low-pressure stage turbine 23 Intercooler 30 Control device (ECU)
31 Pressure sensor A Air (fresh air)
G Exhaust gas Go Exhaust gas (remaining exhaust gas with EGR gas removed)
Pin Supercharging pressure Pt Target supercharging pressure Ran Normal valve control area (intake valve)
Rac Intake valve slow closing control region Rbn Normal valve control region (exhaust valve)
Rbc Exhaust valve early opening control region Δθ1 Slow closing amount Δθ2 Variable phase amount

Claims (6)

In an internal combustion engine equipped with a two-stage supercharging system,
A control device configured to include a variable valve mechanism that can retard the closing timing of the intake valve and advance the entire valve opening period of the exhaust valve, and to control the variable valve mechanism, In accordance with the engine speed and the target boost pressure, the intake valve slow closing control is performed to retard the valve closing timing without advancing the valve opening timing of the previous intake valve,   The control device according to claim 1, wherein the control device is configured to perform exhaust valve early opening control for advancing the entire valve opening period of the exhaust valve according to an engine rotation speed and a target supercharging pressure during acceleration. Internal combustion engine.   3. The internal combustion engine according to claim 1, wherein when the control device performs intake valve delay closing control for delaying the valve closing timing of the intake valve, the amount of delay increases as the target boost pressure increases. .   When the control device performs the exhaust valve early opening control to advance the opening timing of the exhaust valve, the supercharging pressure is measured, and as the difference between the measured supercharging pressure and the target supercharging pressure increases. The internal combustion engine according to claim 1, wherein the advance amount is increased. In a control method for an internal combustion engine comprising a two-stage supercharging system, comprising a variable valve mechanism capable of retarding the closing timing of an intake valve and advancing the entire opening period of an exhaust valve,
A control method for an internal combustion engine, characterized by performing intake valve slow closing control for retarding the valve closing timing without advancing the valve opening timing of the intake valve in accordance with an engine rotational speed and a target supercharging pressure. .   6. The control method for an internal combustion engine according to claim 5, wherein the exhaust valve early opening control is performed to advance the entire valve opening period of the exhaust valve in accordance with the engine rotation speed and the target boost pressure during acceleration.

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