JP2008025402A - Turbocharger for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a turbocharger for an internal combustion engine capable of increasing the amount of intake that can be force-fed by a compressor, while controlling surging. <P>SOLUTION: The turbocharger 10 for an internal combustion engine 1 includes a compressor housing 11 and a compressor wheel 13 provided within the compressor housing 11 and having a plurality of blades 14. The compressor housing 11 is provided with an air inlet 11a so that a plurality of intake flow passages 15 formed between a compressor 20 for supplying compressed air and each blade 14 of a compressor wheel 13 are supplied with compressed air supplied from the compressor 20, from a portion of each intake flow passage 15. An air inlet passage 23 communicates the air inlet 11a with the compressor. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a turbocharger for an internal combustion engine that supercharges using exhaust energy of the internal combustion engine.

  There is known a supercharged internal combustion engine that includes an auxiliary compressor connected in parallel or in series with a turbocharger (see Patent Document 1). In addition, Patent Documents 2 to 5 exist as prior art documents related to the present invention.

JP 2002-021573 A Japanese Utility Model Publication No. 61-190442 JP-A-01-301920 JP 07-189716 A JP 2002-339757 A

  The compressor wheel provided in the compressor of the turbocharger has an upper limit value of the intake amount that can be pumped, that is, a so-called choke flow rate. This choke flow rate is defined by the channel cross-sectional area of the channel formed between a plurality of blades provided in the compressor wheel. Although the choke flow rate can be increased by increasing the flow path cross-sectional area, surging is likely to occur in this case. The above-described conventional internal combustion engine is intended to improve transient response and suppress the occurrence of surging, and does not consider increasing the amount of intake air that can be pumped by the compressor of the turbocharger.

  Therefore, an object of the present invention is to provide a turbocharger for an internal combustion engine that can increase the intake amount that can be pumped by a compressor while suppressing surging.

  A turbocharger for an internal combustion engine according to the present invention supplies compressed air in a turbocharger for an internal combustion engine comprising a compressor housing and a compressor wheel provided in the compressor housing and having a plurality of blades. The compressor housing is provided with compressed air supplied from the compressor to a plurality of intake passages formed between the compressor and each blade of the compressor wheel from the middle of each intake passage. The above-described problem is solved by providing an air introduction passage that communicates the air introduction port and the compressor.

  According to the turbocharger of the present invention, since compressed air can be supplied directly into the intake flow path, a larger intake flow rate than the choke flow rate defined by the cross-sectional area of the intake flow path is pumped. can do. Further, since the compressed air is directly supplied into the intake passage, the compressor wheel can be downsized by reducing the cross-sectional area of the intake passage. Thereby, since the surge limit can be improved, the occurrence of surging can be suppressed. Furthermore, since the capacity of the turbocharger can be reduced, the mountability can be improved.

  In one form of the turbocharger of the present invention, the air introduction port is set in each intake passage, and the compressed air enters a predetermined region where the intake air that has passed through the throat portion at the inlet of each intake passage flows next. May be provided in the compressor housing (claim 2). When the amount of intake air flowing into the compressor increases and the amount of intake air flowing through each intake passage increases, a shock wave is generated in the throat portion, and the pressure in a predetermined region is lower than the pressure before and after that. In this embodiment, since the air introduction port is provided so that the compressed air is supplied to the predetermined region, the work of the compressor can be reduced by introducing the compressed air when the pressure in the predetermined region is reduced. Can reduce the energy consumed.

  In one form of the turbocharger of the present invention, when the intake air amount acquisition means for acquiring the intake air amount of the internal combustion engine and the intake air amount acquired by the intake air amount acquisition means are larger than a predetermined value set in advance, Operation control means for controlling the operation of the compressor so that compressed air is supplied to a plurality of intake passages may be further provided. By controlling the operation of the compressor in this way, it is possible to prevent useless supply of compressed air by the compressor. Therefore, the work of the compressor can be further reduced, and the energy consumed by the compressor can be further reduced.

  In one form of the turbocharger of the present invention, the compressor may be an electric compressor. In this case, an appropriate amount of compressed air can be supplied to the turbocharger by operating the compressor regardless of the operating state of the internal combustion engine.

  As described above, according to the turbocharger for an internal combustion engine of the present invention, the compressed air is directly supplied to the plurality of intake passages formed in the compressor wheel. Therefore, it is possible to pump a larger intake flow rate than the choke flow rate specified. Moreover, since the compressor wheel can be downsized by reducing the cross-sectional area of each intake flow path, the surge limit can be improved and the occurrence of surging can be suppressed.

  FIG. 1 is a schematic view showing an internal combustion engine in which a turbocharger according to one embodiment of the present invention is incorporated. An internal combustion engine (hereinafter also referred to as an engine) 1 in FIG. 1 is mounted on a vehicle as a driving power source, and includes an engine body 2, an intake passage 3, and an exhaust passage 4. The intake passage 3 is provided with a compressor 10 a of the turbocharger 10 and an intercooler 5 for cooling the compressed intake air, and the exhaust passage 4 is provided with a turbine 10 b of the turbocharger 10.

  The engine 1 includes a compressor 20 that compresses air separately from the turbocharger 10. The compressor 20 is driven by an electric motor 21 connected to the drive shaft 20a. The compressor 20 sucks intake air through the branch passage 22 branched from the intake passage 3 and supplies compressed air directly into the compressor 10 a of the turbocharger 10 through the air introduction passage 23. The air introduction passage 23 is provided with a valve 24 that opens and closes the air introduction passage 23.

  FIG. 2 is an enlarged view of a part of the compressor 10 a of the turbocharger 10. As shown in FIG. 2, the compressor 10 a includes a compressor housing 11 and a compressor wheel 13 that is provided in the compressor housing 11 so as to be rotatable about a rotation shaft 12. FIG. 3 shows a part of the compressor wheel 13 as viewed from the upstream side in the flow direction of intake air, that is, from the left side of FIG. As shown in FIG. 3, the compressor wheel 13 is provided with a plurality of blades 14, and an intake passage 15 is formed between the blades 14. As shown in FIG. 2, the compressor housing 11 is provided with an air introduction port 11 a, and the air introduction port 11 a communicates with the compressor 20 through an air introduction passage 23. Further, as shown in FIG. 2, the air introduction port 11a is connected to the negative pressure region 15b set immediately downstream of the throat portion 15a at the inlet of each intake passage 15, in other words, the intake air that has passed through the throat portion 15a is next. It is provided so that compressed air is supplied to the negative pressure region 15b that flows in. That is, the negative pressure region 15b corresponds to a predetermined region of the present invention.

  The operations of the compressor 20 and the valve 24 are respectively controlled by an engine control unit (ECU) 30. The ECU 30 is a well-known computer unit that is configured as a computer including a microprocessor and peripheral devices such as RAM and ROM necessary for its operation, and controls the operating state of the engine 1 based on signals input from various sensors. . For example, an intake air amount sensor 31 is connected to the ECU 30 as an intake air amount acquisition unit that outputs a signal corresponding to the intake air amount. Although various sensors are connected to the ECU 30 in addition to this, illustration is omitted.

  FIG. 4 shows a compressor control routine that the ECU 30 repeatedly executes at a predetermined cycle while the engine 1 is operating. In the control routine of FIG. 4, the ECU 30 first acquires the operating state of the engine 1 such as the intake air amount in step S11. In the next step S12, the ECU 30 determines whether or not the intake air amount of the engine 1 is larger than a predetermined threshold value. For example, a choke flow rate defined by the shape of the compressor wheel 13 is set as the predetermined threshold value. Since the choke flow varies depending on the characteristics of the turbocharger 10 and the characteristics of the engine 1, the predetermined threshold value is appropriately set according to the engine 1 and the turbocharger 10 to which the present invention is applied. Further, since the choke flow rate changes according to the rotational speed of the turbocharger 10, the predetermined threshold value may be appropriately changed according to the rotational speed of the turbocharger 10.

  When it is determined that the intake air amount is larger than the predetermined threshold value, the process proceeds to step S13, where the ECU 30 starts the compressor 20 and opens the valve 24. If the compressor 20 has already been started and the valve 24 has been opened, this state is maintained. Thereafter, the current control routine is terminated. On the other hand, when it is determined that the intake air amount is equal to or less than the threshold value, the process proceeds to step S14, where the ECU 30 stops the compressor 20 and closes the valve 24. Thereafter, the current control routine is terminated.

  FIG. 5 shows an example of the characteristic curve of the compressor 10a. 5 indicate an example of the relationship between the flow rate and the pressure ratio when compressed air is supplied by the compressor 20, and the dotted lines D to F indicate compressed air at the compressor 20. An example of the relationship between the flow rate and the pressure ratio when no pressure is supplied is shown. Further, a solid line S in FIG. 5 indicates a surging line. Since the relationship between the flow rate and the pressure ratio can be changed from the dotted lines D to F to the solid lines A to C by supplying compressed air from the compressor 20 as shown in FIG. A larger amount of intake air can be pumped than the choke flow rate.

  In the turbocharger 10 of the present invention, the compressed air is directly supplied into the intake passage 15, so that the cross-sectional area of the intake passage 15 can be reduced. Therefore, the compressor wheel 13 can be downsized and the surging line S in FIG. 5 can be moved in the upper left direction in FIG. Thereby, the surge limit of the compressor 10a can be improved and the occurrence of surging can be suppressed.

  When the amount of intake air flowing into the compressor 10a increases and the amount of intake air flowing through each intake passage 15 increases, a shock wave is generated in the throat portion 15a, and the pressure in the negative pressure region 15b set immediately downstream of the throat portion 15a Lower than the front and back pressure. In the turbocharger 10 of the present invention, compressed air is supplied to the negative pressure region 15b, so that the work of the compressor 20 can be reduced and the energy consumed by the compressor 20 can be reduced.

  The efficiency of the compressor 10a has a correlation with the temperature and pressure ratio of the intake air after passing through the compressor 10a, and the efficiency is improved as the temperature of the intake air after passing through the compressor 10a is lower and the pressure ratio is higher. The In the present invention, the compressed air is supplied from the compressor 20 to improve the pressure ratio on the large flow rate side and improve the efficiency of the compressor 10a as shown in FIG. 5, so the temperature of the intake air in the compressor 10a can be improved. Can be suppressed, and the temperature of the intake air after passing through the compressor 10a can be lowered. Therefore, for example, when blow-by gas is returned to the intake passage 3, oil coking that deposits in the compressor housing 11 due to the oil contained in the blow-by gas can be suppressed.

  In the present invention, the shape of the compressor wheel 13 and the predetermined threshold value may be set so that the supply of compressed air from the compressor 20 is necessary when the engine 1 is operated near the maximum output. Thus, the operation frequency of the compressor 20 can be reduced by setting the shape of the compressor wheel 13 and a predetermined threshold value. Thereby, durability and reliability of the compressor 20 can be improved.

  The ECU 30 functions as the operation control means of the present invention by executing the control routine of FIG. 4 and controlling the operation of the compressor 20.

  FIG. 6 shows a modification of the turbocharger 10 of the present invention. 6 that are the same as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted. In the modification shown in FIG. 6, the compressor 20 is driven by the crankshaft 2 a of the engine 1. The drive shaft 20 a of the compressor 20 and the crankshaft 2 a of the engine 1 are connected via an electromagnetic clutch 40. The operation of the electromagnetic clutch 40 is controlled by the ECU 30. The ECU 30 switches the electromagnetic clutch 40 to an ON state when the intake air amount is larger than a predetermined threshold, connects the crankshaft 2a of the engine 1 and the drive shaft 20a of the compressor 20, and starts the compressor 20. On the other hand, when the intake air amount is less than or equal to a predetermined threshold value, the electromagnetic clutch 40 is switched to an off state, the crankshaft 2a of the engine 1 and the drive shaft 20a of the compressor 20 are disconnected, and the compressor 20 is stopped. The valve 24 is controlled similarly to the control routine of FIG. By controlling the operation of the electromagnetic clutch 40 in this way, the same operational effects as those of the turbocharger 10 shown in FIG. 1 can be obtained in this modified example.

  This invention is not limited to the form mentioned above, It can implement with a various form. For example, the position where the air inlet 11a is provided is not limited to the position shown in FIG. It is only necessary to provide each intake passage formed in the compressor wheel at a position where compressed air can be supplied from the middle of the intake passage.

1 is a schematic view showing an internal combustion engine in which a turbocharger according to one embodiment of the present invention is incorporated. The figure which expands and shows a part of compressor of a turbocharger. The figure which looked at the compressor wheel from the upstream of the flow direction of intake air. The flowchart which shows the compressor control routine which ECU performs. The figure which shows an example of the performance curve of the turbocharger of this invention. The figure which shows the modification of the turbocharger of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 10 Turbocharger 11 Compressor housing 11a Air inlet 13 Compressor wheel 14 Blade 15 Intake flow path 15a Throat part 15b Negative pressure area (predetermined area)
20 Compressor 23 Air introduction passage 30 Engine control unit (operation control means)
31 Intake amount sensor (intake amount acquisition means)

Claims (4)

In a turbocharger for an internal combustion engine comprising a compressor housing and a compressor wheel provided in the compressor housing and having a plurality of blades,
The compressor for supplying compressed air, and the compressed air supplied from the compressor to a plurality of intake passages formed between the blades of the compressor wheel so that the compressed air is supplied from the middle of each intake passage. A turbocharger for an internal combustion engine, comprising: an air introduction port provided in a compressor housing; and an air introduction passage communicating the compressor.   The air inlet is set in each intake passage, and is provided in the compressor housing so that compressed air is supplied to a predetermined region where the intake air that has passed through the throat portion at the inlet of each intake passage flows next. The turbocharger for an internal combustion engine according to claim 1, wherein   Intake amount acquisition means for acquiring the intake amount of the internal combustion engine, and compressed air is supplied to the plurality of intake passages when the intake amount acquired by the intake amount acquisition means is larger than a predetermined value set in advance. The turbocharger for an internal combustion engine according to claim 1, further comprising operation control means for controlling operation of the compressor.   The turbocharger for an internal combustion engine according to any one of claims 1 to 3, wherein the compressor is an electric compressor.

Images