JP2018071486A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine having two superchargers, in which the "sigh sounds" to be generated from an intake port in the upper end of an induction system are made to give a discomfort to a passenger.SOLUTION: In the case where there are different first and second paths from first and second air bypass valves individually through first and second upstream intake passages to an intake port individually, the time differences Δx till a pressure wave reaches the intake port from the two air bypass valves are calculated (at step ST2: time difference calculating means), thereby to shift the opening timings of the two air bypass valves by an extent of the time difference Δx (at Steps ST3 to ST5: valve control means).SELECTED DRAWING: Figure 3

Description

  The present invention relates to a control device for an internal combustion engine including a supercharger (hereinafter sometimes referred to as a supercharged engine), and particularly relates to control of an air bypass valve disposed in a passage that bypasses a compressor.

  Conventionally, for example, in a V-type supercharged engine, there is a compressor provided in each of an intake passage in the right bank and an intake passage in a left bank. In some cases, each intake passage is provided with a compressor. And in order to avoid the surge which generate | occur | produces in a compressor in such a supercharged engine, there exist some which provided the air bypass valve in the channel | path which bypasses the said compressor.

  For example, in the V-type engine described in Patent Document 1, first and second compressors are disposed in the first and second upstream intake passages, respectively, and the first and second compressors are respectively disposed in passages that bypass these compressors. An air bypass valve is provided. When the throttle opening is reduced during engine deceleration, etc., and the flow of intake air from the compressor loses its destination, the intake air from the compressor downstream to the upstream is opened by opening the air bypass valve before a surge occurs. To return.

  In particular, in the engine of Patent Document 1, the first and second air bypass valves are always opened simultaneously. That is, even if one of the two air bypass valves is opened, if the other remains closed, the intake air that has been supercharged by the other compressor and once taken into the intake system is opened. This is because it flows out from the other air bypass valve to the upstream intake passage and is released into the atmosphere.

Japanese Patent Laid-Open No. 2015-2222075

  By the way, when the air bypass valve is opened to avoid surge as in the conventional example (Patent Document 1), the pressure fluctuation generated here propagates to the upstream side of the intake system as a wave (pressure wave), and the upstream end An abnormal noise (hereinafter, sigh sound) is generated when the air is released from the air inlet of the air. When the two air bypass valves are opened at the same time as described above, if the path length from there to the intake port is different, a “sighing sound” will be generated twice with a time difference, which is There is a problem that it tends to give a sense of incongruity.

  In view of this point, an object of the present invention is to make it difficult for a “sighing sound” from the intake port to give the passenger a sense of incongruity when the two air bypass valves are opened as described above.

  In order to achieve the above object, the present invention is directed to a control device for an internal combustion engine including first and second superchargers, and on the upstream side of the flow of intake air in the intake system of the internal combustion engine, A first upstream intake passage in which the first compressor is disposed, a first air bypass valve disposed in a passage that bypasses the first compressor, and a second in which a second compressor is disposed. An upstream intake passage and a second air bypass valve disposed in a passage that bypasses the second compressor, and a throttle valve that restricts the flow of intake air is disposed downstream of the intake system. It shall be installed.

  The length of the first path from the first air bypass valve to the intake port at the upstream end via the first upstream intake path is the length of the second upstream intake path from the second air bypass valve. The first and second air bypass valves based on the length of each of the first and second paths and the intake air temperature when the length differs from the length of the second path to the intake port. A time difference calculating means for calculating a difference in time for the pressure wave to reach the intake port from each of the first and second air bypasses so that the pressure wave reaches the intake port at the same time. Valve control means for shifting the opening timing of the valve.

  According to the above configuration, each of the first and second paths is provided when the air bypass valve is opened under a predetermined condition in order to prevent the occurrence of a surge in the first or second compressor. The time difference calculation means calculates the time difference until the pressure wave reaches the intake port from the first and second air bypass valves based on the length of the intake air and the intake air temperature. Then, the opening timing of the first and second air bypass valves is shifted by the valve control means by the calculated time difference.

  That is, first, the air bypass valve with the longer path is opened, and then the air bypass valve with the shorter path is opened with the time difference. For example, when the first path is longer than the second path, the first air bypass valve is opened first, and then the second air bypass valve is opened. At the same time, it reaches the inlet. As a result, a “sighing sound” is generated almost simultaneously at the intake port, so that it is difficult for the vehicle occupant to feel uncomfortable.

  According to the control apparatus for an internal combustion engine according to the present invention, in an internal combustion engine having two superchargers, by opening the air bypass valves of the two compressors while appropriately shifting the pressure waves from these air bypass valves to the intake port, Can reach the same time, and “sighs” are generated almost simultaneously. As a result, it is possible to make it difficult for the occupant of the vehicle to feel uncomfortable with the “sighing sound”.

1 is a schematic configuration diagram of an intake / exhaust system of an engine according to an embodiment of the present invention. It is a surge characteristic figure which shows the relationship between the flow volume when a surge generate | occur | produces in a compressor, and a pressure ratio. It is a flowchart which shows the specific procedure of surge avoidance control.

  Hereinafter, an embodiment in which a control device for an internal combustion engine according to the present invention is applied to an engine 1 mounted on a vehicle will be described as an example. The engine 1 is a V-type six-cylinder engine having a right bank 2R and a left bank 2L. Although details are not shown, three cylinders 3 are provided in each bank 2R, 2L. In the following description of the embodiment, the same member installed corresponding to each of the right bank 2R and the left bank 2L is given the letter “R” or “L” after the same number. Represent.

  As shown in the figure, the intake system of the engine 1 is provided with a common surge tank 10 between the right bank 2R and the left bank 2L as an example, and the upstream side of the downstream intake passage 11 connected to the surge tank 10 The first and second upstream intake passages 12R and 12L are connected to be branched (upstream of the intake air flow). That is, two upstream intake passages 12R and 12L are provided on the upstream side of the intake system of the engine 1, and the downstream ends thereof are gathered in the downstream intake passage 11.

  In the present embodiment, the upstream ends of the two upstream intake passages 12R and 12L are connected to a common air cleaner 14 and communicated with the intake port 13 which is the upstream end of the intake system via the air cleaner 14. . Since the air cleaner 14 is arranged on the left side of the vehicle (upper side in FIG. 1) as shown in the figure, the first upstream intake passage 12R is longer than the second upstream intake passage 12L.

  In addition, air flow meters 101R and 101L for measuring the flow rate of the intake air are disposed in the vicinity of the air cleaner 14 in the upstream intake passages 12R and 12L, respectively. As an example, this is a hot wire type air flow meter that measures the mass flow rate of intake air, and incorporates compact thermistor type intake air temperature sensors 102R and 102L in order to measure the temperature of intake air.

  The first upstream intake passage 12R is provided with a first compressor 41R constituting the first turbocharger 4R, and a first throttle valve 15R for restricting the flow of intake air is provided downstream thereof. It is arranged. A bypass flow path 16R that bypasses the first compressor 41R is also provided, and is opened and closed by the first air bypass valve 17R.

  Similarly, a second compressor 41L constituting the second turbocharger 4L is disposed in the second upstream intake passage 12L, and a second throttle valve 15L is disposed downstream thereof. In addition, the second air bypass valve 17L is disposed in the bypass passage 16L that bypasses the second compressor 41L. These air bypass valves 17R and 17L are electromagnetically driven valves driven by solenoids (not shown).

  The first and second throttle valves 15R and 15L respectively disposed in the first and second upstream intake passages 12R and 12L are butterfly valves driven by an electric motor (not shown). Throttle opening sensors 103R and 103L for detecting the respective opening (throttle opening) are attached. Further, intake pressure sensors 104R and 104L are installed in the vicinity of the upstream of the throttle valves 15R and 15L, respectively.

  On the other hand, in the exhaust system of the engine 1, an exhaust manifold 18R is connected to the right bank 2R, and a turbine 42R of the turbocharger 4R is attached thereto. When the turbine 42R is rotationally driven in response to the flow of exhaust, the first compressor 41R is rotated via the turbine shaft 43R. Similarly, an exhaust manifold 18L is connected to the left bank 2L, and a turbine 42L of the turbocharger 4L is attached to the left bank 2L to rotate the second compressor 41R via a turbine shaft 43L.

  In addition, although not shown in figure, the bypass flow path which bypasses each turbine 42R and 42L is also provided, and the waste gate valve is arrange | positioned at each. Further, a catalyst (not shown) is attached to the exhaust passages 19R and 19L on the downstream side of the exhaust flow from the turbines 42R and 42L, and on the downstream side after the two exhaust passages 19R and 19L are assembled. A silencer, not shown, is attached.

-ECU-
The engine 1 configured as described above is controlled by the ECU 100. The ECU 100 includes a known electronic control unit, and includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a backup RAM, and the like, although not shown. . The CPU executes various arithmetic processes based on the control program and map stored in the ROM. In addition, the RAM temporarily stores calculation results in the CPU, data input from each sensor, and the like, and the backup RAM stores data to be saved when the engine 1 is stopped, for example.

  The ECU 100 includes an air flow meter 101R, 101L, intake air temperature sensors 102R, 102L, throttle opening sensors 103R, 103L, intake pressure sensors 104R, 104L, a crank angle sensor, an accelerator opening sensor (not shown), An atmospheric pressure sensor is connected. Based on signals input from these various sensors, the ECU 100 controls the operation of the engine 1 by executing various control programs.

  That is, the ECU 100 outputs control signals to the first and second throttle valves 15R and 15L to control the throttle opening (that is, control of the intake air amount), as well as known fuel injection control and ignition. Control or the like is executed so that the output of the engine 1 conforms to the request of the driver of the vehicle. In the present embodiment, ECU 100 performs control to open first and second air bypass valves 17R and 17L as described below.

−Surge avoidance control−
That is, for example, when the engine 1 is decelerated while the vehicle is running, the ECU 100 causes the surge to open the air bypass valves 17R and 17L in order to avoid the occurrence of a surge in the compressors 41R and 41L. Perform avoidance control. That is, when the engine 1 is decelerated, the first and second throttle valves 15R and 15L are reduced in opening, while the rotations of the first and second compressors 41R and 41L are not immediately reduced. .

  For this reason, the flow of the intake air from the first and second compressors 41R, 41L loses its place and flows backward, so that a so-called surge may occur. Specifically, as shown in FIG. 2, the flow rate of the intake air in the compressors 41R and 41L is plotted on the vertical axis, and the downstream pressure ratio with respect to the upstream side of the compressors 41R and 41L is plotted on the horizontal axis. , A region where a surge occurs (surge region shown with hatching in the figure) appears on the lower right side of the figure.

  The upper limit of the flow rate in this surge region is the surge flow rate, and the surge flow rate increases as the pressure ratio increases, although it varies depending on the intake system of the engine 1, particularly the specifications of the compressors 41R and 41L. Therefore, such surge characteristics are examined in advance by experiments or the like, and for example, the flow rates of intake air in the first and second compressors 41L and 41R are estimated from the opening degrees of the first and second throttle valves 15R and 15L. , It can be predicted that a surge will occur when one of them becomes below the surge flow rate.

  In the present embodiment, the pressure downstream of the compressors 41L and 41R is measured by the intake pressure sensors 104R and 104L (supercharging pressure), and the pressure upstream of the compressors 41L and 41R is atmospheric pressure. Therefore, when the atmospheric pressure sensor is not provided, it is possible to define the surge characteristics using the supercharging pressure instead of the pressure ratio, assuming that the atmospheric pressure is a fixed value.

  When the occurrence of a surge is predicted in one of the first and second compressors 41L and 41R as described above, the corresponding air bypass valves 17R and 17L are opened to move from the downstream side to the upstream side of the compressors 41L and 41R. Although the intake air can be returned and the occurrence of a surge can be prevented, an abnormal sound (hereinafter referred to as a sigh sound) is generated at the intake port 13 at this time, and there is a possibility that the vehicle occupant may feel uncomfortable. It was.

  That is, when the air bypass valves 17R and 17L are opened as described above, the pressure fluctuation generated here becomes a wave (pressure wave) and propagates upstream through the upstream intake passages 12R and 12L. It generates a “sighing sound” when it is released to the atmosphere. In the present embodiment, the lengths of the first and second upstream intake passages 12R and 12L are different, so that a “sighing sound” may occur twice. Easy to give.

  Specifically, as shown in FIG. 1, the length L1 of the first path from the first air bypass valve 17R to the intake port 13 via the first upstream intake path 12R is from the second air bypass valve 17L. It is longer than the length L2 of the second path that reaches the intake port 13 via the second upstream intake path 12L. Therefore, the time until the pressure wave reaches the intake port 13 from the first and second air bypass valves 17R and 17L is longer in the first path.

  For this reason, if the first and second air bypass valves 17R and 17L are opened at the same time, first, the pressure wave from the second air bypass valve 17L reaches the intake port 13 and a "sighing sound" is generated. After alerting the occupant, the pressure wave from the first air bypass valve 17R reaches the intake port 13 and a “sighing sound” is generated again. Thereby, the occupant particularly recognizes the second “sighing sound” and feels uncomfortable.

  In consideration of this point, in the present embodiment, the time until the pressure wave reaches the intake port 13 as described above is based on the lengths L1, L2, etc. of the first and second paths. The difference Δx is calculated. Then, the opening timing of the two air bypass valves 17R and 17L is shifted so as to eliminate the time difference Δx, in other words, the first air bypass valve 17R is opened earlier by the time difference Δx.

  Hereinafter, a specific procedure of surge avoidance control will be described with reference to the flowchart of FIG. This control routine is repeatedly executed at a predetermined timing in the ECU 100. First, in step ST1, whether the occurrence of a surge in the first or second compressor 41L, 41R during the operation of the engine 1 is predicted. Judge whether or not. As described above with reference to FIG. 2, this estimates the flow rate of intake air in the first and second compressors 41L and 41R, and predicts that a surge will occur when one of them becomes the surge flow rate or less.

  If the determination is negative (NO), the routine is temporarily terminated, whereas if the determination is affirmative (YES), the process proceeds to step ST2, and pressure waves are taken in from the first and second air bypass valves 17R and 17L, respectively. A time difference Δx is calculated until the mouth 13 is reached. Specifically, using the first and second path lengths L1, L2 (L1> L2) and the respective intake air temperatures T1, T2 (calculated from signals from the intake air temperature sensors 102R, 102L), the pressure The wave propagation speeds V1 and V2 are calculated by the following equations (1) and (2), respectively.

V1 = 331.5 + 0.6 × T1 (1)
V2 = 331.5 + 0.6 × T2 (2)
Then, the times x1 and x2 until the pressure waves reach the intake port 13 from the first and second air bypass valves 17R and 17L are x1 = L1 / V1 and x2 = L2 / V2, respectively. The time difference Δx = x1−x2 can be calculated. In consideration of the time difference Δx thus calculated, in step ST3, first, the first air bypass valve 17R having a long path is opened.

  Subsequently, in step ST4, it is determined whether or not a time corresponding to the time difference Δx has elapsed since the opening of the first air bypass valve 17R as described above. If a negative determination (NO) is made, the process waits. On the other hand, if the time difference Δx has elapsed and the determination is affirmative (YES), the process proceeds to step ST5, and this time the second air bypass valve 17L having the shorter path is opened, and the routine is ended (END).

  By executing step ST2 of the flow, the ECU 100 performs the first and second air bypass valves 17R, 17L based on the lengths L1, L2 and the intake air temperatures T1, T2 of the first and second paths, respectively. The time difference calculating means for calculating the time difference Δx until the pressure wave arrives at the intake port 13 from each time. Further, by executing the steps ST3 to ST5, the ECU 100 shifts the opening timings of the first and second air bypass valves 17R and 17L by the time difference Δx so that the pressure wave reaches the intake port 13 at the same time. The control means is configured.

  Therefore, according to the engine control apparatus of the present embodiment, in the engine 1 including the first and second turbochargers 4R and 4L, the first and second throttle valves are used, for example, during deceleration operation. By opening the first and second air bypass valves 17R and 17L when the opening of 15R and 15L is reduced and a surge is predicted to occur in either the first or second compressor 41R or 41L Surge can be prevented in advance.

  In addition, the time difference Δx until the pressure wave reaches the intake port 13 from the first and second air bypass valves 17R and 17L at that time is calculated, and the first and second air bypass valves are correspondingly calculated. Since the opening timings of 17R and 17L are shifted, it is possible to generate a “sighing sound” almost simultaneously at the same time when the pressure waves reach the intake port 13 from these two air bypass valves 17R and 17L. . Therefore, it is difficult to give a sense of discomfort to the vehicle occupant.

-Other embodiments-
The configuration of the present invention is not limited to the above-described embodiment, but includes other various forms. That is, in the above-described embodiment, the first and second throttle valves 15R and 15L are disposed in the intake system of the engine 1. However, the present invention is not limited to this, and a single throttle valve is provided in the downstream intake passage 11. May be provided.

  Of course, the internal combustion engine is not limited to the V-type 6-cylinder engine 1 as in the above-described embodiment. For example, in addition to V8, V10, etc. The present invention can also be applied to a case where each is provided with a turbocharger.

  Further, the turbocharger is not limited to the turbochargers 4R and 4L as in the above embodiment, and the supercharger may be a mechanical supercharger, or the engine 1 may be, for example, a direct injection type in a cylinder. Alternatively, in addition to the intake port injection type gasoline engine, an in-cylinder direct injection type multi-fuel engine, a diesel engine, or the like may be used.

  The present invention, in an internal combustion engine including two superchargers, can make it difficult for an abnormal noise generated for avoiding a surge of a compressor to give an uncomfortable feeling to a vehicle occupant. Is expensive.

1 Engine 4R, 4L 1st and 2nd turbocharger (supercharger)
13 Intake port 12R, 12L First and second upstream intake passages 15R, 15L First and second throttle valves 16R, 16L First and second bypass passages (passing passages)
17R, 17L First and second air bypass valves 100 ECU (time difference calculation means, valve control means)
L1, L2 Length of first and second paths t1, T2 Intake air temperature Δx time difference in first and second paths

Claims (1)

A control device for an internal combustion engine comprising two first and second superchargers,
On the upstream side of the flow of intake air in the intake system of the internal combustion engine, a first upstream intake passage provided with a first compressor and a first passage provided in a passage bypassing the first compressor. An air bypass valve, a second upstream intake passage in which a second compressor is disposed, and a second air bypass valve disposed in a passage that bypasses the second compressor, A throttle valve that restricts the flow of intake air is arranged downstream of the intake system.
The length of the first path from the first air bypass valve through the first upstream intake path to the upstream end inlet is from the second air bypass valve through the second upstream intake path. Different from the length of the second path to the inlet;
Time difference calculating means for calculating a difference in time for the pressure wave to reach the intake port from each of the first and second air bypass valves based on the length of each of the first and second paths and the intake air temperature; ,
Valve control means for shifting the opening timings of the first and second air bypass valves by the calculated time difference so that the pressure wave reaches the intake port at the same time. Control device.

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