JP2012092707A - Electrically-assisted turbocharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrically-assisted turbocharger that reduces iron loss of an electric motor, effectively suppresses vibration of a turbo shaft, and allows use of an inexpensive rolling bearing as a bearing of the turbo shaft.SOLUTION: The electrically-assisted turbocharger 10 is configured by connecting a turbocharger 11 and an electric motor 12 by a reduction gear mechanism 13. The reduction gear mechanism 13 includes: a turbo-side gear 19 attached to a turbo shaft 16 of the turbocharger 11; and an electric-motor-side gear 21 attached to a rotor 20 of the electric motor 12 and connected to the turbo-side gear 19 while having a larger number of teeth than the turbo-side gear 19. The turbo-side gear 19 is mounted on the antinode of vibration of the turbo shaft 16.

Description

  The present invention relates to an electrically assisted turbocharger in which an electric motor (motor) is combined with a turbocharger.

  In a system in which a turbocharger is added to the engine, when the engine speed is low and the torque is low, the exhaust gas energy is small, so that the exhaust turbine has a low speed and the amount of intake air supercharged by the intake compressor is small. For this reason, if a high torque is required at the time of low engine rotation, the intake amount is insufficient with respect to the request coming from the fuel injection amount. In addition, during transient operation where the engine condition fluctuates, the rotation of the turbocharger is delayed in response to fluctuations in the engine condition due to the rotational inertia of the turboshaft. For example, the vehicle rapidly increases the fuel injection amount for acceleration. When you want to make it happen, the turbocharger rotates slowly and the intake volume does not increase rapidly.

  On the other hand, an electric assist turbocharger in which an electric motor is combined with a turbocharger is known. The electric assist turbocharger can rapidly increase the intake air amount by assisting the driving of the turbo shaft by the power of the electric motor at the time of low engine speed or transient operation.

  A conventional electrically-assisted turbocharger is a turbocharger having an exhaust turbine rotated by exhaust gas and an intake compressor connected to the exhaust turbine via a turboshaft. And an electric motor having a stator positioned at the center.

  In this electrically assisted turbocharger, since the rotor of the electric motor is provided integrally with the turbo shaft, the rotor rotates at the same rotational speed as the turbo shaft.

JP 2004-169629 A JP 2006-320143 A

  However, in a general electric motor, there is a region where the copper loss is large in a region where the rotational speed is low, and a region where the iron loss is large in a region where the rotational speed is high. Copper loss is due to the current flowing in the winding. Iron loss occurs because electrical energy is consumed by eddy currents flowing through the iron core. More specifically, the iron loss includes eddy current loss and hysteresis loss, both of which increase according to the rotational speed.

  Since a general electric motor has a large iron loss when the rotation speed is high, an appropriate use rotation speed is set in a range of several thousand rpm to 20,000 rpm.

  On the other hand, the turbocharger rotates at a higher speed as the exhaust gas increases. For example, a turbocharger mounted on a small engine may have a rotation speed of 100,000 to 200,000 rpm. This rotational speed corresponds to a region where eddy current loss is large in a general electric motor.

  As described above, in the conventional electric assist turbocharger, the rotor of the electric motor has the same rotational speed as that of the turbo shaft, so the electric motor is used in a rotational speed region that is not recommended, and wasteful power consumption due to iron loss. Is inevitable.

  Although there is an ultra-high-speed motor that can suppress an increase in iron loss even at ultra-high speed rotation exceeding 100,000 rpm, it is expensive because it uses a special material and structure, and is not suitable for mounting on a popular vehicle.

  The turbocharger is an ultra-compact ultra-high-speed rotating machine with a maximum rotational speed of several hundred thousand rpm as described above. The turbo-shaft bearing is an overhang type with impellers attached to both ends of the rotating shaft. Has a structure.

  A sliding bearing is often used as a bearing for supporting such a high-speed rotating rotor. However, since a self-excited vibration called an oil whip is generated in a perfect circular bearing, a floating bush bearing is used.

  However, this floating bush bearing has a special structure, and if the floating bush bearing is used, there is a problem that the cost of the entire machine is increased.

  Accordingly, an object of the present invention is to provide an electric assist turbocharger that can reduce iron loss of an electric motor, effectively suppress vibration of a turbo shaft, and can use an inexpensive rolling bearing as a bearing of the turbo shaft. There is to do.

  The present invention devised to achieve this object is an electrically assisted turbocharger configured by connecting a turbocharger and an electric motor with a reduction gear mechanism, and the reduction gear mechanism is connected to a turbo shaft of the turbocharger. An attached turbo side gear; and an electric motor side gear attached to the rotor of the electric motor and connected to the turbo side gear and having more teeth than the turbo side gear, and the turbo side gear, It is an electrically assisted turbocharger attached to the vibration belly of the turbo shaft.

  The bearing for bearing the turbo shaft may be a rolling bearing.

  According to the present invention, there is provided an electric assist turbocharger that can reduce iron loss of an electric motor, effectively suppress vibration of a turbo shaft, and can use an inexpensive rolling bearing as a bearing of the turbo shaft. Can do.

1 is a side view showing an electrically assisted turbocharger according to an embodiment of the present invention. It is a front view which shows the reduction gear mechanism of the electrically assisted turbocharger of FIG. (A), (b) is a figure explaining the positioning method of the turbo side gear.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a side view showing an electrically assisted turbocharger according to a preferred embodiment of the present invention.

  As shown in FIG. 1, the electrically assisted turbocharger 10 according to the present embodiment is configured by connecting a turbocharger 11 and an electric motor 12 by a reduction gear mechanism 13.

  The turbocharger 11 coaxially connects the exhaust turbine 14 rotated by exhaust gas, the intake compressor 15 that compresses air by rotation, the exhaust turbine 14 and the intake compressor 15, and the intake compressor 15 from the exhaust turbine 14 side. And a turbo shaft 16 for transmitting rotation to the side. The turbo shaft 16 is supported at two locations by a bearing 17 on the exhaust turbine 14 side and a bearing 18 on the intake compressor 15 side.

  The bearings 17 and 18 are generally used sliding bearings or inexpensive rolling bearings.

  As shown in FIG. 2, the reduction gear mechanism 13 is attached to the turbo side gear 19 attached to the turbo shaft 16 of the turbocharger 11, the rotor 20 of the electric motor 12, and connected to the turbo side gear 19. And a motor-side gear 21 having more teeth than the side gear 19.

  As shown in FIG. 3, the turbo-side gear 19 analyzes the vibration of the turbo shaft 16 in advance (FIG. 3 (a)), and based on the analysis, the vibration antinode (the place where the amplitude becomes the largest during vibration). Is positioned and attached (FIG. 3B).

  Next, the operation of the electric assist turbocharger 10 will be described.

  In the electrically assisted turbocharger 10, when the rotational speed of the turbo shaft 16 is low and the intake air amount supercharged from the intake compressor 15 is small, it is necessary to increase the intake air amount in order to increase the fuel injection amount.

  In such a case, the rotation of the turbo shaft 16 is assisted from the motor side gear 21 through the turbo side gear 19 by rotating the motor 12. At this time, since the rotation of the electric motor 12 is accelerated and transmitted to the turbo shaft 16, the electric motor 12 may be rotated at a lower rotational speed than the desired rotational speed of the turbo shaft 16.

  During a transient operation (for example, during overtaking operation) in which the engine state is changed to a higher-load engine state with the rotational speed of the turbo shaft 16 being high, the rotation of the turbo shaft 16 is performed by rotating the motor 12. Assist. At this time, the rotational speed of the turbo shaft 16 is high, but the rotational speed of the electric motor 12 is lower than the desired rotational speed of the turbo shaft 16, so the electric motor 12 is used in a rotational speed region where the iron loss is small. The

  In the electrically assisted turbocharger 10 according to the present embodiment, the turbo-side gear 19 is attached to the antinode of the vibration of the turbo shaft 16, so the vibration of the turbo shaft 16 (vibration in the vertical direction in FIG. 3B). Can be suppressed. As a result, it is not necessary to use an expensive floating bush bearing as the bearings 17 and 18 of the turbo shaft 16, and a generally used sliding bearing or an inexpensive rolling bearing can be used.

  As described above, the electrically-assisted turbocharger 10 according to the present embodiment only needs to rotate the electric motor 12 at a lower rotational speed than the desired rotational speed of the turbo shaft 16 and reduce the iron loss of the electric motor 12. be able to. That is, according to the electrically assisted turbocharger 10, wasteful consumption of electric power due to iron loss is reduced, and as a result, fuel consumption is suppressed, so that fuel efficiency can be improved.

  Further, in the electrically assisted turbocharger 10 according to the present embodiment, since the electric motor 12 is operated at a low rotational speed, it is not necessary to employ an ultra-high speed motor, and an electric motor having a general material and structure can be employed. Can be suppressed.

  Further, since the turbo gear 19 is attached to the antinode of the vibration of the turbo shaft 16, the vibration of the turbo shaft 16 can be suppressed, and sliding bearings generally used as the bearings 17 and 18 of the turbo shaft 16 can be suppressed. Or an inexpensive rolling bearing can be used.

  The gear ratio between the motor-side gear 21 and the turbo-side gear 19 is preferably 5: 1 to 20: 1. For example, if the gear ratio is 10: 1, the motor 12 is rotated when the rotational speed of the turbo shaft 16 is 200,000 rpm. The rotational speed of 20,000 rpm is sufficient.

  The electric assist turbocharger 10 can obtain regenerative power by using the electric motor 12 as a generator when the exhaust gas energy has a surplus. In this case as well, the power generation efficiency decreases when the electric motor 12 is at a high rotational speed, but in the present embodiment, the electric power generation efficiency can be improved by decelerating the rotation of the turbo shaft 16 and transmitting it to the electric motor 12.

DESCRIPTION OF SYMBOLS 10 Electric assist turbocharger 11 Turbocharger 12 Electric motor 13 Reduction gear mechanism 14 Exhaust turbine 15 Intake compressor 16 Turbo shaft 17 Bearing (exhaust turbine side)
18 Bearing (intake compressor side)
19 Turbo side gear 20 Rotor 21 Motor side gear

Claims (2)

An electrically assisted turbocharger configured by connecting a turbocharger and an electric motor with a reduction gear mechanism,
The reduction gear mechanism is
A turbo-side gear attached to a turbo shaft of the turbocharger;
The motor-side gear attached to the rotor of the motor and connected to the turbo-side gear, and having more teeth than the turbo-side gear;
The electric assist turbocharger, wherein the turbo side gear is attached to a vibration belly of the turbo shaft.   The electrically assisted turbocharger according to claim 1, wherein the bearing that supports the turbo shaft is a rolling bearing.

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