JP2009250191A - Control device of internal combustion engine with supercharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device capable of changing an upper limit value of a used number of the rotation of a supercharger according to an operation state and sufficiently exerting the performance of the supercharger. <P>SOLUTION: This control device includes the first supercharger used for supercharging in both a first operation mode in which the number of superchargers used for supercharging is small and a second operation mode in which the number of superchargers used for supercharging is larger than that of the first operation mode, and the second supercharger which is used for supercharging in the first operation mode and not used for supercharging in the second operation mode, and provided with two or more superchargers connected to each other in parallel. The control device is provided with a control part for adjusting the upper limit value of the used number of rotation being the upper limit value of the number of the rotation of the first supercharger according to the first or second operation mode. The upper limit value of the used number of the rotation of the first supercharger in the first operation mode is set to be higher than that of the first supercharger in the second operation mode. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine having a plurality of superchargers, and in particular, optimizes the upper limit value of the rotational speed of the supercharger according to the operating state (the number of superchargers used for supercharging). Relates to the device.

  An internal combustion engine that has a plurality of superchargers and adjusts the number of superchargers used for supercharging according to the operating state has been proposed. For example, an internal combustion engine having a primary turbo and a secondary turbo connected in parallel corresponds to this. In such an internal combustion engine, there are a single turbo mode in which the secondary turbo is used for supercharging and the primary turbo and the secondary turbo are used for supercharging depending on the operating state, and a twin turbo mode in which the primary turbo and secondary turbo are used for supercharging. Used by switching.

Patent Document 1 discloses a device that delays the timing for switching from the single turbo mode to the twin turbo mode during acceleration as compared to during normal driving. As a result, the region operated in the single turbo mode is expanded, and it is possible to prevent the supercharging pressure from being lowered by switching to the twin turbo mode during acceleration.
Japanese Patent Laid-Open No. 02-191816

  However, switching from the single turbo mode to the twin turbo mode is performed before the upper limit value of the rotational speed that is the upper limit value of the rotational speed in actual use of the primary turbo is exceeded. The operating speed upper limit is a margin considering the pressure loss caused by other than the turbocharger itself, such as the pressure loss due to clogging of the air cleaner, from the maximum speed that is the upper limit of the speed that can be used as a single primary turbo. The number of rotations minus is set. The margin is not set to a different value depending on the operating state, but is set to a value that takes into account a large pressure loss that is assumed in the twin turbo mode, that is, a state where the most pressure loss occurs. Therefore, the device of Patent Document 1 delays the timing for switching from the single turbo mode to the twin turbo mode within a range that does not exceed the upper limit of the number of rotations used in consideration of a larger pressure loss, so the switching timing can be delayed. A sufficient width cannot be provided. That is, the performance of the turbocharger in the single turbo mode cannot be sufficiently exhibited.

  Accordingly, an object of the present invention is to provide an apparatus that changes the upper limit value of the rotational speed of the supercharger in accordance with the operating state and sufficiently exhibits the performance of the supercharger.

  The control apparatus for an internal combustion engine according to the present invention includes a first operation mode in which the number of superchargers used for supercharging is small, and a second number in which the number of superchargers used for supercharging is larger than that in the first operation mode. Including a first supercharger used for supercharging in any of the operation modes, and a second supercharger used for supercharging in the first operation mode and not used for supercharging in the second operation mode. And two or more superchargers connected to the controller, and a control unit that adjusts a use rotation speed upper limit value that is an upper limit value of the rotation speed of the first supercharger according to the first and second operation modes, The use rotation speed upper limit value of the first supercharger in the first operation mode is set higher than the use rotation speed upper limit value of the first supercharger in the second operation mode.

  As a result, the first operation mode when the number of superchargers used for supercharging such as the single turbo mode is small is switched to the second operation mode when the number of superchargers used for supercharging such as the twin turbo mode is large. 1 engine speed is set to the second engine speed at the time of switching from the first operation mode to the second operation mode in such a manner that the upper limit value of the use speed in the first operation mode is matched with the upper limit value of the use speed in the second operation mode. Compared to it, it becomes possible to make it higher. When the engine speed at the switching point becomes high, the region that can be operated in the first operation mode is widened, and the performance of the first supercharger can be sufficiently exhibited.

  Further, it is possible to widen the hysteresis of the engine speed for switching between the first operation mode and the second operation mode. Normally, a certain number of engine speed ranges, which are the width of hysteresis, are required, but some of them can be realized by increasing the upper limit value of the number of revolutions used in the first supercharger in the first operation mode. Thus, the turbocharger can be reduced in size. Since the turbocharger can be reduced in size, fuel efficiency can be improved.

  As the internal combustion engine of the present invention, an internal combustion engine constituting a parallel twin turbo system having a primary turbo and a secondary turbo can be considered. However, it may be an internal combustion engine in which three or more superchargers are connected in parallel and the number of superchargers used for supercharging varies depending on the operating state. In this case, when the number of superchargers used for supercharging is small, the upper limit value of the turbocharger used is set high, and when the number of superchargers used for supercharging is large, The machine use rotation upper limit is set low.

  Preferably, the use rotation speed upper limit value of the first supercharger in the first operation mode is determined based on a pressure loss caused by a portion related to the first supercharger in the first operation mode, and the second operation mode The upper limit value of the rotational speed of the first supercharger at is determined based on the pressure loss due to the portion related to the first supercharger in the second operation mode.

  The upper limit value of the rotational speed of the first supercharger is the pressure loss caused by the portion related to the first supercharger from the maximum rotational speed that is the upper limit value of the rotational speed that can be used as a single unit of the first supercharger. A value obtained by subtracting the margin degree considering the above is set. Since the amount of intake air in the first operation mode is smaller than the amount of intake air in the second operation mode, the pressure loss at this portion is also relatively small, and therefore, based on the pressure loss (margin degree) that differs depending on the operation mode. Thus, the use rotation speed upper limit value of the first supercharger in the first operation mode can be set higher than the use rotation speed upper limit value of the first supercharger in the second operation mode. The pressure loss due to the portion related to the first supercharger includes pressure loss due to aging such as clogging of the air cleaner and pressure in piping such as an intake passage constituting the internal combustion engine including the first supercharger. Variations in loss can be mentioned.

  As described above, according to the present invention, it is possible to provide a device that changes the upper limit value of the rotation speed of the supercharger in accordance with the operating state and sufficiently exhibits the performance of the supercharger.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The internal combustion engine 1 includes a control unit 5, a primary turbo 13, a secondary turbo 14, an engine body 30, a compressor inlet side intake passage 51, a compressor outlet side intake passage 52, an intake manifold 55, a turbine inlet side exhaust passage 72, and a turbine outlet side. An exhaust passage 73 is provided.

The control unit 5 includes a CPU, a ROM that stores a control program, and a RAM that stores various data. The control unit 5 receives signals from various sensors, and outputs control signals to the intake air switching valve 19 and the like to generate an internal combustion engine. Control each part of the vehicle including the engine 1. In particular, in the present embodiment, the control unit 5 is in a state where the upper limit value of rotation speed N _lim of the primary turbo 13 is different between the twin turbo mode and the single turbo mode (the first upper limit value N ₁ or the second upper limit value N ₂ ), The operation of the internal combustion engine 1 is controlled.

  During the operation of the internal combustion engine 1, air is sucked into the combustion chamber of each cylinder of the engine body 30 via the compressor inlet side intake passage 51, the compressor outlet side intake passage 52, and the intake manifold 55 (see FIG. 1). (See solid arrow). The fuel injected from the injector forms an air-fuel mixture with the sucked air. The air-fuel mixture is combusted by ignition of the spark plug based on the ignition signal from the control unit 5. A crankshaft (not shown) rotates by the reciprocating motion of the piston according to the explosive force caused by the combustion of the air-fuel mixture. The exhaust gas generated by the combustion is exhausted through the exhaust manifold 71, the turbine inlet side exhaust passage 72, and the turbine outlet side exhaust passage 73 (see the broken line arrow in FIG. 1).

  Next, the configuration of each part of the internal combustion engine 1 will be described focusing on the primary turbo 13 and the secondary turbo 14. The primary turbo 13 and the secondary turbo 14 are connected in parallel. The primary turbo 13 operates from a low intake air amount region to a high intake air amount region, and the secondary turbo 14 stops in the low intake air amount region. Accordingly, in the low intake air amount region, the operation is performed in the single turbo mode in which the secondary turbo 14 is not used for supercharging and the primary turbo 13 is used for supercharging, and in the high intake air amount region, the primary turbo 13 and secondary The operation is performed in a twin turbo mode in which the turbo 14 is used for supercharging.

  The primary turbo 13 has a first turbine 13t and a first compressor 13c, and the secondary turbo 14 has a second turbine 14t and a second compressor 14c. The inlet sides of the first turbine 13 t and the second turbine 14 t are connected to a turbine inlet side exhaust passage 72 that communicates with the exhaust manifold 71. The outlet sides of the first turbine 13t and the second turbine 14t are connected to a turbine outlet side exhaust passage 73 that communicates with an exhaust gas purification catalyst (not shown).

The inlet sides of the first compressor 13c and the second compressor 14c are connected to the compressor inlet side intake passage 51. The compressor inlet side intake passage 51 is provided with an air cleaner 11 and an air flow meter 12 for detecting the amount of air flowing through the air cleaner, that is, the amount of intake air A. In the present embodiment, the intake air amount A is used to calculate the maximum intake manifold pressure _Pmax . The outlet sides of the first compressor 13 c and the second compressor 14 c are connected to a compressor outlet side intake passage 52 that communicates with the intake manifold 55. An intercooler 23 and a throttle valve 25 are provided in the compressor outlet side intake passage 52.

  In order to switch between the twin turbo mode and the single turbo mode, that is, to switch the operation and stop of the secondary turbo 14, the exhaust gas to the second turbine 14 t is provided on the inlet side of the second turbine 14 t in the turbine inlet side exhaust passage 72. Exhaust gas switching valve 31 is provided for switching between blocking and opening the flow, and blocking the flow of air from the second compressor 14c to the intake manifold 55 on the outlet side of the second compressor 14c in the compressor outlet side intake passage 52. And an intake switching valve 19 for switching between open and open.

  In order to smoothly switch from the single turbo mode to the twin turbo mode, on the compressor outlet side intake passage 52, between the outlet of the second compressor 14 c and the intake air switching valve 19, and on the compressor inlet side intake passage 51. An intake bypass passage 53 that communicates with the inlet side of one compressor 13c is provided. The intake bypass passage 53 is provided with an intake bypass valve 17 that switches between blocking and opening the air flow.

  In the single turbo mode, both the intake switching valve 19 and the exhaust switching valve 31 are closed, and the intake bypass valve 17 is opened, thereby operating the primary turbo 13 and stopping the secondary turbo 14. To do. In the twin turbo mode, both the intake switching valve 19 and the exhaust switching valve 31 are opened, and the intake bypass valve 17 is closed, whereby the primary turbo 13 and the secondary turbo 14 are operated.

  An intake reed valve 21 that opens and closes according to the pressure difference is provided in an intake reed passage (bypass passage of the intake air switching valve 19) 54 that communicates the upstream and downstream of the intake switching valve 19. That is, when the intake air switching valve 19 is closed, when the outlet pressure of the second compressor 14c becomes larger than the outlet pressure of the first compressor 13c by a predetermined amount, the valve opens and the air opens the intake reed valve 21. Flows from the upstream side to the downstream side.

  The intake bypass passage 53 and the intake lead passage 54 are set narrower than the compressor inlet side intake passage 51 and the compressor outlet side intake passage 52.

Further, a pressure sensor 27 for detecting the intake manifold pressure P is provided in the intake manifold 55. In this embodiment, operation control is performed such that the intake manifold pressure P does not exceed the maximum intake manifold pressure _Pmax .

Next, details of operation control of the internal combustion engine 1 will be described. In the single turbo mode, the use _engine speed upper limit N _lim of the primary turbo 13 is set to a first upper limit value N ₁ lower than the maximum engine speed N _max of the primary turbo 13 (N _lim = N ₁ <N _max , (See step S12 in FIG. 4). In the twin turbo mode, the use engine speed upper limit value N _lim of the primary turbo 13 is set to a second upper limit value N ₂ lower than the first upper limit value N ₁ (N _lim = N ₂ <N ₁ , (See step S13).

The maximum rotational speed N _max is an upper limit value (for example, 170,000 rpm) of the rotational speed that can be used as a single unit of the primary turbo 13. The first upper limit N ₁ is the number of rotations of the upper limit value of the primary turbo 13 internal combustion engine 1 is in a single turbo mode including primary turbo 13 (eg 160,000 rpm). The second upper limit value _{N 2} is the rotational speed of the upper limit value of the primary turbo 13 internal combustion engine 1 is in the twin turbo mode including primary turbo 13 (eg 155,000 rpm). Therefore, the primary turbo 13 can be used as a single unit by increasing the rotational speed to the maximum rotational speed N _max. However, in the single turbo mode, the use is limited to the first upper limit value N ₁ or less. the twin turbo mode, used in the second upper limit value N ₂ or less is limited.

A maximum speed N _max, the first difference between the first upper limit value N _1, the pressure loss due to the sites associated with the primary turbo 13 in the single turbo mode, specifically, aging clogging of the air cleaner 11 And a difference in rotational speed (margin) based on pressure loss (about 2 kPa) due to pressure and pressure loss variation (about 2 kPa) in piping such as an intake passage constituting the internal combustion engine 1. Similarly, the second difference between the maximum rotation speed N _max and the second upper limit value N ₂ is a pressure loss caused by a portion related to the primary turbo 13 in the twin turbo mode, specifically, clogging of the air cleaner 11. The difference in rotational speed (margin) is based on the pressure loss (about 5 kPa) due to aging and the like, and the pressure loss variation (about 5 kPa) in the piping such as the intake passage constituting the internal combustion engine 1. The first difference is smaller than the second difference because the amount of intake air in the single turbo mode is smaller than the amount of intake air in the twin turbo mode, so that the pressure loss at this portion is relatively small. Based on the pressure loss (margin degree) that varies depending on the operation mode, the upper limit value N _lim of the primary turbo 13 in the single turbo mode is compared with the upper limit value N _lim of the primary turbo 13 in the twin turbo mode. To a higher value.

When it is operated in the single turbo mode, as the rotation speed of the primary turbo 13 does not exceed the first upper limit value N _1, i.e., intake manifold pressure P, based on the first upper limit value N ₁ and the intake amount A The operation control is performed so as not to exceed the maximum intake manifold pressure _Pmax calculated in the above. Specifically, the engine speed at the first switching point PO ₁ (see the black circles in FIGS. 2 and 3) corresponding to the first upper limit value N ₁ that is the upper limit value of the speed of the primary turbo 13 in the single turbo mode. Until the intake manifold pressure P exceeds the maximum intake manifold pressure _Pmax , the single turbo mode is switched to the twin turbo mode. When operating in the twin turbo mode, the rotation speed of the primary turbo 13 does not exceed the second upper limit value N ₂ , that is, the intake manifold pressure P is set to the second upper limit value N ₂ and the intake air amount A. Operation control is performed so as not to exceed the maximum intake manifold pressure _Pmax calculated based on the above. Specifically, the output point PO _max corresponding to the second upper limit value N ₂ is the upper limit value of the rotational speed of the primary turbo 13 in twin turbo mode engine speed in _(Fig. 2, star reference mark point in FIG. 3) Adjustment is performed such as reducing the fuel injection amount until the intake manifold pressure P exceeds the maximum intake manifold pressure _Pmax .

Next, a procedure for setting the use _engine speed upper limit N _lim of the primary turbo 13 will be described with reference to the flowchart of FIG. A procedure for calculating the maximum intake manifold pressure P _max based on the intake air amount A and the use rotation speed upper limit value N _{lim of the} primary turbo 13 will be described with reference to the flowchart of FIG. These processes are always performed during the operation of the internal combustion engine 1 (for example, at regular intervals). However, using the rotational speed upper limit _{N lim} primary turbo 13 in the single turbo mode (= first limit value _{N 1)} around and, using the rotational speed upper limit value of the primary turbo 13 in twin turbo mode _{N lim} (= second upper limit N ₂ ) may be performed only when driving near the vehicle.

In the process of setting the use rotation speed upper limit N _lim of the primary turbo 13, it is determined in step S11 whether or not the operation is performed in the single turbo mode. Such a determination is made based on the opening degree of the exhaust gas switching valve 31 or the like. If it is operated in the single turbo mode, in step S12, using the rotational speed upper limit N _lim primary turbo 13 is set to a first upper limit value N _1. When the engine is operated in the twin turbo mode, the use rotation speed upper limit value N _lim of the primary turbo 13 is set to the second upper limit value N ₂ in step S13. The use rotation speed upper limit value N _lim of the primary turbo 13 set in step S12 or step S13 is used in step S31 in the control for calculating the maximum intake manifold pressure P _max described later.

In the process of calculating the maximum intake manifold pressure _Pmax , in step S31, the intake air amount A detected by the air flow meter 12, the compressor map of the primary turbo 13 (see FIG. 6), and the use rotational speed upper limit value of the primary turbo 13 Based on N _lim , the maximum pressure ratio πc in the primary turbo 13 is calculated. In step S32, the relationship between the intake air amount A and the pressure difference (precompressor pressure loss ΔP1) generated between the air flow meter 12 and the inlet of the first compressor 13c and the intake air amount A (see FIG. 7). Based on this, the pressure at the inlet of the first compressor 13c (pre-compressor pressure P1) is calculated (P1 = atmospheric pressure−ΔP1). In step S33, the maximum pressure at the outlet of the first compressor 13c (maximum compressor outlet pressure P3) is calculated based on the maximum pressure ratio πc and the compressor pre-pressure P1 (P3 = πc × P1). In step S34, the pressure loss ΔPic in the intercooler 23 is calculated based on the intake air amount A and a specific empirical formula. In step S35, the maximum intake manifold pressure _Pmax is calculated based on the maximum compressor outlet pressure P3 and the intercooler pressure loss ΔPic ( _Pmax = P3-ΔPic).

Conventionally, the upper limit of rotation speed N _{lim of the} primary turbo 13 has been set using a margin considering the pressure loss in the twin turbo mode, that is, in the single turbo mode and the twin turbo mode, The use rotation upper limit value N _max was set to the second upper limit value N ₂ . Therefore, in the single turbo mode, the operation control is performed within a range not exceeding the use rotation upper limit value (N _lim = N ₂ <N ₁ ) corresponding to the excessively estimated margin.

In the present embodiment, in order to optimize the robustness that has been overestimated in the single turbo mode, the use rotation upper limit N _lim of the primary turbo 13 in the single turbo mode is set to the use of the primary turbo 13 in the twin turbo mode. It is set higher than the rotation upper limit value N _lim . As a result, the first engine speed NE ₁ at the time of switching from the single turbo mode to the twin turbo mode (see the first switching point PO ₁ , and the black circles in FIGS. 2 and 3) is used as the rotation of the primary turbo 13 in the single turbo mode. The second engine speed at the time of switching from the single turbo mode to the twin turbo mode in such a manner that the upper limit of the number is matched with the upper limit of the rotational speed in the twin turbo mode (see the second switching point PO ₂ , the white circles in FIGS. 2 and 3). It becomes possible to make it higher than NE ₂ (rotational speed difference d = NE ₁ −NE ₂ = about 100 rpm). When the engine speed at the switching point is increased, a region where the engine can be operated in the single turbo mode is widened, and the performance of the primary turbo 13 in the single turbo mode can be sufficiently exhibited. It is also possible to suppress torque shock and deterioration of exhaust emission when switching from single turbo mode to twin turbo mode.

Further, when the engine speed at the switching point increases, it is the difference between the third engine speed NE ₃ and the first engine speed NE ₁ at the time of switching from the twin turbo mode to the single turbo mode (third switching point). The engine speed width W (width of hysteresis) can be increased (see FIG. 3). Normally, the engine speed width W, which is the width of the hysteresis, is required to be about 400 to 500 rpm, of which about 100 rpm is used as the second upper limit value for the rotational speed upper limit value N _lim of the primary turbo 13 in the single turbo mode. This can be realized by changing from N ₂ to the first upper limit value N ₁ , and the primary turbo 13 can be downsized accordingly. By reducing the size of the turbo, it becomes possible to improve the fuel efficiency by about 0.5 to 1%.

  Although the present embodiment has been described using an internal combustion engine constituting a parallel twin turbo system having two superchargers, three or more superchargers are connected in parallel, and supercharging is performed according to operating conditions. Other forms (internal combustion engine) in which the number of superchargers used and the upper limit value of the number of revolutions used can be changed. In this case, when the number of superchargers used for supercharging is small, the upper limit value of the turbocharger used is set high, and when the number of superchargers used for supercharging is large, The machine use rotation upper limit is set low.

It is a block diagram of the internal combustion engine in this embodiment. It is a figure which shows the compressor performance map of the primary turbo in a single turbo mode and a twin turbo mode. It is a figure which shows the relationship between an engine speed and a torque. It is a flowchart which shows the procedure of the control which sets the use rotation speed upper limit of a primary turbo. It is a flowchart which shows the procedure of the control which calculates the maximum intake manifold pressure. It is a figure which shows the compressor performance map of the primary turbo used in order to calculate the highest pressure ratio. It is a figure which shows the relationship between the amount of intake air, and the pressure loss before a compressor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 5 Control part 11 Air cleaner 12 Air flow meter 13 Primary turbo 13c 1st compressor 13t 1st turbine 14 Secondary turbo 14c 2nd compressor 14t 2nd turbine 17 Intake bypass valve 19 Intake switching valve 21 Intake reed valve 23 Intercooler 25 Throttle Valve 27 Pressure sensor 30 Engine body 31 Exhaust switching valve 51 Compressor inlet side intake passage 52 Compressor outlet side intake passage 53 Intake bypass passage 54 Intake lead passage 55 Intake manifold 71 Exhaust manifold 72 Turbine inlet side exhaust passage 73 Turbine outlet side exhaust passage

Claims (2)

Used for supercharging in both the first operation mode in which the number of superchargers used for supercharging is small and the second operation mode in which the number of superchargers used for supercharging is large compared to the first operation mode And two or more superchargers connected in parallel, including a first supercharger that is used for supercharging in the first operation mode and a second supercharger that is not used for supercharging in the second operation mode. A machine,
A control unit that adjusts a use rotation speed upper limit value that is an upper limit value of the rotation speed of the first supercharger according to the first and second operation modes;
The upper limit value of the rotation speed of the first supercharger in the first operation mode is set higher than the upper limit value of the rotation speed of the first supercharger in the second operation mode. Control device for internal combustion engine. The upper limit value of the rotational speed of the first supercharger in the first operation mode is determined based on a pressure loss caused by a portion related to the first supercharger in the first operation mode,
The use upper limit value of the first supercharger in the second operation mode is determined based on a pressure loss caused by the part in the second operation mode. Control device.

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