JP2007231893A - Supercharger of internal-combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a supercharger of internal-combustion engine capable of reducing BPF sound generated due to revolution of compressor wheels. <P>SOLUTION: A supercharger 4 of an internal-combustion engine 1 is provided with a pair of compressor wheels 9 having the same number of blades 9a as each other, arranged as opposed to each other within a compressor housing 8, a variable nozzle mechanism 20 for adjusting a rotational speed of at least either one of the compressor wheels, and a rotation sensor 30 for outputting signals that correlate with phases of the blades 9a from a predetermined location Pd on a rotation route of the pair of compressor wheels 9, and rotational speeds of respective compressor wheels 9. The operation of the variable nozzle mechanism 20 is controlled such that phases of the blades 9a coincide with each other between the pair of compressor wheels 9, and the rotational speeds coincide with each other, based on output signals of the rotation sensor 30. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a supercharging device for an internal combustion engine having a pair of compressor wheels.

As a supercharging device for an internal combustion engine, a twin turbocharger device having a sensor capable of detecting the rotation speed (rotation speed) of a compressor wheel in order to synchronize the rotation of a pair of compressor wheels is known (Patent Literature). 1). An intermittent clutch is inserted between each of the drive shafts of the pair of superchargers and the crankshaft that drives them, and at the start of driving of each supercharger, one of the intermittent clutches is PWM-controlled to each supercharger. A turbocharger that synchronizes the response time of the machine is also known (see Patent Document 2). There is also known a twin turbocharger device in which a pair of turbine wheels are arranged so as to face each other (see Patent Document 3). In addition, there is Patent Document 4 as a prior art document related to the present invention.
JP 2000-45786 A JP-A-6-37533 Japanese Patent No. 2656559 Japanese Utility Model Publication No. 2005-273568

  When a turbocharger is driven, noise at a blade passing frequency (sometimes referred to as BPF for short) is generated as a pressure field formed around the blade of the compressor wheel rotates together with the blade. To do. In the supercharging device including a pair of superchargers, the energy of the BPF sound (BPF noise) is also doubled. The BPF sound is generated at the intake air inflow portion with respect to the compressor wheel, propagates to the outside through the air cleaner from the intake intake passage of the supercharger, and propagates to the outside through the compressor housing. The compressor housing has a complicated shape, and many high-order vibration modes exist on the surface of the compressor housing in the high frequency region to which the BPF belongs. It is difficult to eliminate these vibration modes by changing the shape of the compressor housing.

  Accordingly, an object of the present invention is to provide a supercharging device for an internal combustion engine that can reduce BPF noise generated due to rotation of a pair of compressor wheels by controlling rotation of the compressor wheels.

  The supercharging device for an internal combustion engine according to the present invention has a pair of compressor wheels that have an equal number of blades and are disposed in the compressor housing so as to face each other, and the rotational speed of at least one of the compressor wheels. A rotation speed adjusting means for adjusting; a rotation detecting means for generating and outputting a signal correlated with a phase of the blade from a predetermined position on a rotation path of the pair of compressor wheels and a rotation speed of each compressor wheel; and Rotation control for controlling the operation of the rotation speed adjusting means so that the phases of the blades of the pair of compressor wheels coincide with each other and the rotation speeds of the compressor wheels coincide with each other based on the output signal of the rotation detection means Means for solving the above-mentioned problem (claim 1).

  According to the supercharging device of the present invention, the number of blades of each compressor wheel is set to be equal to each other, and the rotation speeds of each compressor wheel are controlled to be equal to each other, so that the BPF generated due to the rotation of each compressor wheel The period of the sound matches each other. Moreover, since the rotation of the compressor wheel is controlled so that the blade phases are matched between the pair of compressor wheels, BPF vibration waves having the same phase are generated in the vicinity of each compressor wheel. And since a pair of compressor wheel is arrange | positioned so that it may mutually oppose, the vibration wave of BPF which generate | occur | produced in the vicinity of each compressor wheel advances symmetrically, and mutually overlaps with an antiphase. As a result, the vibration waves of the BPF cancel each other and the vibration mode of the BPF is canceled, and as a result, the BPF sound is reduced.

  In one form of the present invention, the compressor housing may be formed as an integral housing shared by a pair of compressor wheels. According to this embodiment, the vibration wave of the BPF generated in each compressor wheel propagates to the common compressor housing, and the vibration wave of the BPF overlaps before the BPF sound is emitted to the outside of the compressor housing. Vibration canceling action occurs. For this reason, the radiation of the BPF sound from the surface of the compressor housing to the outside can be further reduced.

  In the embodiment in which the compressor housing is integrally formed, the path length from the branch position to each compressor wheel in the intake air intake passage of the compressor housing to each compressor wheel may be set to be substantially the same. 3). According to this embodiment, the vibration waves of the BPF propagating from the compressor wheels so as to go back through the intake intake passage overlap with each other at the branch positions of the intake route in opposite phases. Thereby, it is possible to reduce the BPF sound released from the intake intake passage to the outside.

  In one embodiment of the present invention, the rotation axes of the pair of compressor wheels may be located on the same axis (claim 4). According to this aspect, the symmetry of the pair of compressor wheels can be ensured, and the action of canceling vibration waves of the BPF can be exhibited more effectively. For this reason, the BPF sound can be further reduced.

  As described above, according to the supercharging device of the present invention, a pair of compressor wheels arranged opposite to each other are rotated at the same speed, and the number of blades is the same between the compressor wheels. Since the phases of the blades are also matched with each other, BPF vibration waves having the same period and phase are generated in each compressor wheel, and these vibration waves travel symmetrically. It is possible to generate an oscillating wave canceling effect by superimposing them in opposite phases. Thereby, the vibration mode of BPF can be canceled and BPF sound can be reduced.

  FIG. 1 shows an internal combustion engine (hereinafter referred to as an engine) provided with a supercharging device according to an embodiment of the present invention. The engine 1 includes a pair of intake passages 2 and a pair of exhaust passages 3. The supercharging device 4 includes a pair of turbochargers 5 installed between the intake passage 2 and the exhaust passage 3. Each turbocharger 5 forms a turbine housing 6 provided so as to constitute a part of the exhaust passage 3, a turbine wheel 7 disposed inside the turbine housing 6, and a part of the intake passage 2. And a compressor wheel 9 disposed inside the compressor housing 8. The turbine wheel 7 and the compressor wheel 9 are coaxially connected via a turbine shaft 10, and both the wheels 7 and 9 can rotate integrally around the turbine shaft 10. That is, the center line of the turbine shaft 10 coincides with the rotational axis RA of the wheels 7 and 9. An air cleaner (not shown) for filtering the intake air is provided on the upstream side of the compressor housing 8, and an intercooler 11 for cooling the intake air compressed by the compressor wheel 9 is provided between the compressor housing 8 and the engine 1. .

  The pair of turbochargers 5 are arranged such that the turbine shafts 10 are coaxial, that is, on a common rotation axis RA, and the compressor wheels 9 face each other. The configuration around the compressor wheel 9 is shown enlarged in FIG. In FIG. 2, a substantially half portion from the rotation axis RA of the compressor wheel 9 is shown. As shown in FIG. 2, the compressor housing 8 is formed as an integral housing shared by a pair of compressor wheels 9, and the shape thereof is a virtual center plane CP orthogonal to the direction in which the compressor wheels 9 are arranged. Is set approximately symmetrical to the left and right. The compressor housing 8 is provided with a pair of compressor chambers 12 that respectively accommodate the compressor wheels 9 and a pair of intake intake passages 14 for guiding intake air from the intake intake ports 13 to the compressor chambers 12. The intake intake passage 14 is configured as an independent passage from the intake intake port 13 to the compressor chamber 12 by being partitioned by a partition wall 15 disposed along the center plane CP. The passage lengths from the branch position of the intake intake passage 13, in other words, the intake intake passage 14 to the compressor wheels 9 are equal to each other. The compressor chamber 12 is also symmetrical to the left and right with the partition wall 15 in between, and the compressor wheel 9 accommodated in the compressor chamber 12 is also arranged at an equal distance from the partition wall 15 with respect to the direction of the rotation axis RA. In the compressor housing 8, the shape of the wall surrounding the compressor chamber 12 and the intake intake passage 14 may be substantially symmetrical, and details such as stays and bosses for attaching the compressor housing 8 to the engine 1 and the like are asymmetric. It may be. The air cleaner disposed on the upstream side of the intake intake port 13 may be shared between the intake intake passages 14 or may be provided independently for each intake intake passage 14.

  The compressor wheel 9 also has a symmetrical shape with respect to the center plane CP of the partition wall 15. Further, as indicated by an arrow RD in FIG. 2, the rotation directions of the compressor wheels 9 are set to be equal to each other. FIG. 3 shows a state in which the pair of compressor wheels 9 viewed from the directions of arrows A and B in FIG. The rotation direction of each compressor wheel 9 is as shown by the arrow RD in FIG. Each compressor wheel 9 has a predetermined number of blades 9a arranged at equal intervals in the rotation direction. The number of blades 9a is equal between the two wheels 9. Further, the blades 9 a of one compressor wheel 9 have the same shape and the same size, and the blade 9 a of the other compressor wheel 9 has a symmetrical shape with respect to those of the one compressor wheel 9. Although details of the turbine wheel 7 are not shown, the turbocharger 4 of the present embodiment aims to rotate the pair of compressor wheels 9 at the same speed and in the same phase. It is desirable to have a shape and size.

  Returning to FIG. 1, each turbocharger 5 is provided with a variable nozzle mechanism 20 as a rotation speed adjusting means. The variable nozzle mechanism 20 operates a nozzle (not shown) arranged in the turbine housing 6 to change the cross-sectional area of the exhaust inflow passage of the turbine housing 6, thereby changing the flow velocity of the exhaust gas guided to the outer periphery of the turbine wheel 7. Change. The rotational speed of the turbine wheel 7 and the compressor wheel 9 changes due to the change in the exhaust flow velocity. This type of variable nozzle mechanism is publicly known, and the details of the mechanism are not the gist of the present invention, so that the description thereof is omitted.

  Each turbocharger 5 is provided with a rotation sensor 30 as rotation detection means for detecting the rotation speed of each compressor wheel 9 and the phase of the blade 9a. As shown in FIG. 3, each rotation sensor 30 includes a sign 30 a provided on the outer periphery of the turbine shaft 10, and a sensor body 30 b that detects the sign 30 a to generate and output a predetermined detection signal. . One mark 30 a is provided on each outer periphery of the pair of turbine shafts 10. The positional relationship between the mark 30 a and the blade 9 a regarding the rotation direction of the compressor wheel 9 is the same between the pair of compressor wheels 9. In the example of FIG. 3, each mark 30 a is provided in alignment with the position of one blade (hereinafter, this may be referred to as a specific blade) 9 a of each compressor wheel 9 in the rotation direction. The sensor main body 30b is arranged with its detection portion directed toward the radial center of the turbine shaft 10. In the rotation direction of the compressor wheel 9, the detection position DP of the mark 30 a by the sensor body 30 b also coincides with each other between the pair of compressor wheels 9. In the example of FIG. 3, the detection position DP of the sensor body 30 b is set directly above the rotation axis RA of each turbine shaft 10 in the vertical direction.

  According to the above rotation sensor 30, the detection signal of the marker 30a is output from the sensor body 30b every time the specific blade 9a arrives at the detection position DP in FIG. The period in which the detection signal is output correlates with the rotation speed of the compressor wheel 9, and the elapsed time and period from the output timing of the detection signal correlate with the phase of the specific blade 9a from the detection position of the sensor body 30b. The marker 30a only needs to function as a mark that can be detected by the sensor body 30b. For example, a notch formed on the outer periphery of the turbine shaft 10, a reflective member attached to the outer periphery of the turbine shaft 10, a magnet, and the like can function as the sign 30 a.

  Returning to FIG. 1, the output signal of the rotation sensor 30 (more precisely, the output signal from the sensor body 30 b) is input to an engine control unit (ECU) 40. The ECU 40 is configured as a computer unit that combines a microprocessor and peripheral devices such as ROM and RAM necessary for the operation of the microprocessor. The ECU 40 controls the operation state of the engine 1 to a target state by adjusting the fuel injection amount, the fuel injection timing, etc. with reference to output signals from a sensor group that detects the state of each part of the engine 1. Sensors referred to by the ECU 40 include an air flow meter that detects the intake air amount, an A / F sensor that outputs a signal corresponding to the air-fuel ratio in the exhaust gas, and the like, but these are not shown. Furthermore, the ECU 40 functions as the rotation control means of the present invention by appropriately executing the rotation control routine shown in FIG. 4 in parallel with other programs related to the operation control of the engine 1.

  In the first step S <b> 1 of the rotation control routine of FIG. 4, the ECU 40 detects the rotation speed of each compressor wheel 9 based on the output signal of the rotation sensor 30. For example, when the angular velocity ω (rad / sec.) Is detected as the rotational velocity, if the cycle in which the detection signal of the marker 30a is output from the rotation sensor 30 is T (sec.), The angular velocity ω is ω = 2π / T. Given in. Note that the rotation speed may be obtained as the number of rotations per unit time. In the subsequent step S2, the ECU 40 determines whether or not there is a difference in the rotational speeds of the compressor wheels 9. If the difference in rotational speed is within the allowable range from the viewpoint of suppression of BPF sound, it may be determined that there is no difference in rotational speed.

  If it is determined that there is a difference in the rotational speed, the ECU 40 proceeds to step S3 and executes an operation for correcting the rotational speed of the compressor wheel 9. The correction of the rotational speed is based on one of the compressor wheels 9, and the variable nozzle mechanism 20 corresponding to the other compressor wheel 9 so that the rotational speed of the other compressor wheel 9 matches that of the reference compressor wheel 9. This is performed by operating the nozzle. The opening degree of the nozzle of the variable nozzle mechanism 20 may be set so that the operation amount (opening adjustment amount) of the nozzle increases as the speed correction amount, that is, the difference between the rotational speeds of the two compressor wheels 9 increases. A map describing the correspondence between the speed correction amount and the nozzle operation amount may be created in advance and stored in the ROM of the ECU 40, and the nozzle operation amount corresponding to the speed correction amount may be acquired by referring to the map. . After executing the correction operation in step S3, the process returns to step S1, and the processes in steps S1 to S3 are repeated until there is no difference in rotational speed.

  When it is determined in step S2 that there is no difference in rotational speed, the ECU 40 proceeds to step S4 and detects the phase from the detection position PD of the specific blade 9a of each compressor wheel 9. For example, if the phase of the specific blade 9a is θ (rad.), The elapsed time from the output timing of the detection signal of the marker 30a in the rotation sensor 30 is t (sec.), And the period of the detection signal is T (sec.). In this case, the phase θ can be obtained by θ = 2π · t / T. In subsequent step S5, the ECU 40 determines whether or not there is a deviation in the phase of the blade 9a between the two wheels 9. Since each blade 9a is provided at equal intervals in the rotation direction, when the number of blades 9a is Nb, the interval Pb between the blades 9a on the same compressor wheel 9 is Pb = 2π / Nb (rad.). is there. Therefore, if the phase difference Δθ of each specific blade 9a detected in step S4 is divisible by the interval Pb of the blade 9a, that is, if the remainder when the phase difference Δθ is divided by the blade interval Pb is 0, the compressor wheel The phases of the blades 9a coincide with each other. Therefore, in step S5, it may be determined whether or not there is a phase shift from the remainder when the phase difference Δθ is divided by the blade interval Pb. If the phase shift is within an allowable range from the viewpoint of suppressing the BPF sound, it may be determined that there is no phase shift.

  If it is determined in step S5 that there is a phase shift, the ECU 40 proceeds to step S6 and executes a correction operation related to the phase shift. The correction of the phase shift is based on one of the compressor wheels 9 in the same manner as the correction of the rotational speed, and the phase of the blade 9a of the other compressor wheel 9 is matched with that of the blade 9a of the reference compressor wheel 9. The operation is performed by operating the nozzle of the variable nozzle mechanism 20 corresponding to the other compressor wheel 9. In this case, the opening degree of the nozzle of the variable nozzle mechanism 20 may be set in accordance with the phase shift amount so that the operation amount of the nozzle (opening adjustment amount) increases as the phase shift amount increases. A map describing the correspondence between the phase correction amount and the nozzle opening adjustment amount is created in advance and stored in the ROM of the ECU 40, and the operation amount of the nozzle corresponding to the phase correction amount is obtained by referring to the map. May be.

  After starting the phase correction operation in step S6, the ECU 40 proceeds to step S7 to detect the phase of the specific blade 9a of each compressor wheel 9, and in step S8, the blade between the compressor wheels 9 is the same as in step S5. It is determined whether or not there is a phase shift of 9a. If there is a phase shift, the ECU 40 returns to step S6 and repeats the processes of steps S6 to S8 until the phase shift is eliminated. In the correction of the phase shift, the rotational speed of the compressor wheel 9 to be controlled is increased or decreased, so that a temporary difference occurs in the rotational speed between the compressor wheels 9. Therefore, it is desirable to control the operation amount of the nozzle of the variable nozzle mechanism 20 so that the difference in the rotational speed of the compressor wheel 9 decreases as the phase shift amount decreases. Therefore, not only the nozzle operation amount is changed proportionally according to the phase shift amount, but also the phase shift correction is completed by controlling the nozzle operation amount by appropriately combining differential control or integral control. It is desirable to operate the nozzles of the variable nozzle mechanism 20 so that the rotational speeds of the two compressor wheels 9 coincide at the time. If it is determined in step S8 that the phase shift has been eliminated, the ECU 40 returns to step S1.

  According to the supercharger 4 described above, a pair of compressor wheels 9 are arranged coaxially facing each other, the compressor wheels 9 are rotated at the same speed, and the phases of the blades 9a of the wheels 9 are also matched. Therefore, in the vicinity of each compressor wheel 9, BPF vibration waves having the same period and phase are generated. These vibration waves propagate symmetrically through the compressor housing 8 and overlap each other, thereby causing a vibration canceling action. As a result, higher-order vibration modes generated in the compressor housing 8 are canceled out, and radiation of BPF sound from the surface of the compressor housing 8 can be suppressed. Further, since the passage lengths from the compressor wheel 9 to the branch position of the intake intake passage 14 (intake intake port 13) are equal to each other, the intake passage 2 upstream of the intake intake port 13 is shared between the compressor wheels 9. If so, the vibration waves of the BPF propagating through the intake air intake passage 14 overlap with each other at the intake air intake port 13 in opposite phases, thereby causing a vibration canceling action. Thereby, release of BPF sound from the intake port 13 is also suppressed.

  This invention is not limited to said form, It can implement with a various form. For example, the compressor housing 8 is not limited to the illustrated form, and may be implemented in various forms. FIG. 5 shows another form of the compressor housing 8. In the form of FIG. 5, the partition of the compressor housing 8 is omitted. Accordingly, at least the upstream region of the intake intake passage 14 is shared between the pair of compressor chambers 12. Therefore, a branch position to each compressor wheel 9 in the intake intake passage 14, that is, a passage from the center of the region Pd where the intake air is divided into two toward the compressor wheel 9 in the intake intake passage 14 to each compressor wheel 9. The lengths are also the same. In this example, the vibration waves of the BPF generated in the vicinity of the compressor wheel 9 overlap each other in the intake intake passage 14 to cause a vibration canceling action. Thereby, the release of BPF sound from the intake port 13 is reliably suppressed. The form of FIG. 5 is particularly suitable when an air cleaner is shared between the compressor wheels 9.

  In each of the above embodiments, the compressor housing 8 is formed as an integral housing shared by the pair of compressor wheels 9. However, the present invention is not limited to this, and the compressor housing 8 is individually provided for each compressor wheel 9. It may be provided. Even in this case, by connecting the compressor housings 8 to each other, it is possible to superimpose the vibration waves of the BPF and to cancel the vibration waves of the BPF. Alternatively, even if the compressor housings 8 are separated without being connected, the vibration waves of the BPF overlap each other in the vicinity of the surface of the housing 8 when they are arranged close to each other, thereby causing a vibration canceling action. As a result, the BPF sound is reduced.

  In the above embodiment, the pair of compressor wheels 9 are provided symmetrically across the center plane CP, but the present invention is not limited to such a form. For example, even if the size (diameter or thickness in the direction of the rotation axis RA) of the compressor wheel 9 is different between the left and right, by rotating the wheels at the same speed and making the blade phases coincide with each other Further, it is possible to reduce the BPF sound by causing a vibration canceling action by superposing the vibration waves of the BPF. Even when the pair of compressor wheels 9 are not arranged on the common rotation axis RA, the rotational speeds of the compressor wheels 9 and the phases of the blades 9a are matched so that the BPF generated in the vicinity of each compressor wheel 9 can be reduced. It is possible to vibrate the compressor housing 8 symmetrically on the left and right with respect to the arrangement direction of the wheels 9 by the vibration wave with the same phase and the same period, thereby causing a canceling action due to the overlap of vibrations and reducing the BPF sound. . The rotation directions of the pair of compressor wheels do not necessarily have to be the same, and BPF noise can be reduced as long as the rotation speeds of both compressor wheels and the phases in the rotation direction of the blades coincide.

  The rotation speed adjusting means is not limited to the variable nozzle mechanism, and various devices can be used. For example, a waste gate valve for discharging a part of the exhaust gas without introducing it to the turbine housing 6 can be used as the rotation speed adjusting means. In the case of a so-called motor-assisted turbocharger in which a rotating electrical machine is incorporated in the turbine shaft, the rotating electrical machine can be used as a rotational speed adjusting means by adjusting the rotational torque or braking torque applied by the rotating electrical machine. The supercharging device according to the present invention is not limited to the one provided with a pair of turbochargers, but is a supercharging device provided with a pair of mechanical superchargers that drive a compressor wheel using a rotational motion extracted from a crankshaft or the like of an engine. It can also be applied to. In that case, a clutch as a rotational speed adjusting means may be interposed between a drive shaft such as a crankshaft and the compressor wheel, and the rotational speed of the compressor wheel may be adjusted by operating the clutch. Alternatively, a continuously variable transmission such as a variable pulley mechanism is interposed as a rotational speed adjusting means between a drive shaft such as a crankshaft and the compressor wheel, and the speed ratio of the continuously variable transmission is controlled by operating the gear ratio of the continuously variable transmission. The rotation speed may be adjusted. The target for adjusting the rotation speed to match the rotation speed or phase of the compressor wheel is not limited to one compressor wheel, and the rotation speed and phase are adjusted by controlling the rotation speed of both compressor wheels in parallel. May be.

The figure which shows the supercharging device of the internal combustion engine which concerns on one form of this invention. The enlarged view around the compressor wheel. The figure which showed the state which looked at a pair of compressor wheel from the arrow A and B direction of FIG. 2 side by side. The flowchart which shows the rotation control routine which ECU of FIG. 1 performs. The figure which shows the other form of the compressor housing shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 4 Supercharging device 5 Turbocharger 6 Turbine housing 7 Turbine wheel 8 Compressor housing 9 Compressor wheel 9a Blade 10 Turbine shaft 11 Intercooler 13 Intake intake port 14 Intake intake passage 20 Variable nozzle mechanism (rotational speed adjustment means)
30 Rotation sensor (Rotation detection means)
40 Engine control unit (rotation control means)

Claims (4)

A pair of compressor wheels having an equal number of blades and disposed in the compressor housing opposite each other;
Rotation speed adjusting means for adjusting the rotation speed of at least one of the compressor wheels;
Rotation detection means for generating and outputting a signal correlated with the phase of the blade from a predetermined position on the rotation path of the pair of compressor wheels and the rotation speed of each compressor wheel;
Rotation for controlling the operation of the rotation speed adjusting means so that the phases of the blades of the pair of compressor wheels coincide with each other and the rotation speeds of the compressor wheels coincide with each other based on the output signal of the rotation detection means Control means;
A supercharging device for an internal combustion engine, comprising:   The supercharging device according to claim 1, wherein the compressor housing is formed as an integral housing shared by a pair of compressor wheels.   The supercharging device according to claim 2, wherein passage lengths from branch positions to the compressor wheels in the intake air intake passage of the compressor housing to the compressor wheels are set to be substantially the same.   The supercharging device according to any one of claims 1 to 3, wherein rotation axes of the pair of compressor wheels are coaxially positioned.

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