JP2012092800A - Electrically-assisted turbocharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrically-assisted turbocharger that reduces iron loss of an electric motor and prevents deterioration of shaft vibration of a turbo shaft.SOLUTION: The electrically-assisted turbocharger includes: an exhaust turbine 3 having a turbine wheel 2 rotated by exhaust gas; an intake compressor 5 having a compressor wheel 4 for compressing air by rotation; a turbo shaft 6 integrated with the turbine wheel 2 and the compressor wheel 4 so as to transmit rotation from the exhaust-turbine side to the intake-compressor side; a driven gear 7 attached to the node part of shaft vibration of the turbo shaft 6; a drive gear 8 meshed with the driven gear 7 and having a larger number of teeth than the driven gear 7; and an electric motor 9 for rotating the drive gear 8.

Description

  The present invention relates to an electric assist turbocharger in which an electric motor is combined with a turbocharger, and relates to an electric assist turbocharger that reduces iron loss of an electric motor and does not deteriorate shaft vibration of a turbo shaft.

  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 electrically assisted turbocharger in which an electric motor is combined with a turbocharger is known. The electric assist turbocharger can quickly increase the intake air amount by assisting the drive of the turbo shaft by the power of the electric motor at the time of low engine speed or transient operation.

  As shown in FIG. 4, a conventional electrically assisted turbocharger 301 includes an exhaust turbine 303 having a turbine wheel 302 rotated by exhaust gas, an intake compressor 305 having a compressor wheel 304 that compresses air by rotation, and a turbine. A turbo shaft 306 that is integrated with the wheel 302 and the compressor wheel 304 and transmits rotation from the exhaust turbine side to the intake compressor side, and a rotor of the electric motor 307 that is coaxial with the turbo shaft 306 and integrated with the turbo shaft 306 (see FIG. And a stator (not shown) of the electric motor 307 located on the outer periphery of the rotor.

JP 2004-169629 A JP 2006-320143 A

  As described above, in the conventional electrically assisted turbocharger 301, the rotor of the electric motor 307 is arranged coaxially with the turbo shaft 306 and integrated with the turbo shaft 306, so the rotor is the same as the turbo shaft 306. It rotates at the rotation speed.

  However, as shown in FIG. 5, a general electric motor has 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. The eddy current loss can be obtained by equation (1).

In equation (1), the operating frequency f is proportional to the rotational speed. It can be seen from the term f ^{2 in} equation (1) that the eddy current loss increases as the rotational speed increases.

  Thus, since the general electric motor has a large iron loss when the rotational speed is high, the range of several thousand rpm to 20,000 rpm is set as an appropriate rotational speed.

  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.

  Thus, in the conventional electrically assisted turbocharger 301, the rotor of the electric motor 307 has the same rotational speed as that of the turbo shaft 306. Therefore, the electric motor 307 is used in a rotational speed region that is not recommended. Wasteful power consumption due to 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.

  In general, when a turbocharger rotates at a high speed, shaft vibration occurs on the turbo shaft. At this time, the shaft vibration nodal portion is located on the exhaust turbine side so that a heavy load due to the shaft vibration of the turbo shaft is not applied to the bearing bearing the exhaust shaft side of the turbo shaft and the bearing supporting the intake compressor side of the turbo shaft. In addition, the position is set so as not to be biased toward the intake compressor side. However, when a member that exerts a mechanical action on the turbo shaft is added, the position of the node portion is shifted, and there is a possibility that a heavy load is applied to any of the bearings. Therefore, when adding a member for reducing iron loss, it is necessary to sufficiently consider shaft vibration.

  Accordingly, an object of the present invention is to provide an electric assist turbocharger that solves the above-described problems, reduces iron loss of an electric motor, and does not deteriorate shaft vibration of a turbo shaft.

  In order to achieve the above object, the present invention integrates an exhaust turbine having a turbine wheel rotated by exhaust gas, an intake compressor having a compressor wheel for compressing air by rotation, and the turbine wheel and the compressor wheel. A turbo shaft that transmits rotation from the exhaust turbine side to the intake compressor side, a driven gear attached to a shaft vibration portion of the turbo shaft, and a drive gear that meshes with the driven gear and has more teeth than the driven gear. And an electric motor for rotating the drive gear.

  The number of teeth of the driven gear may be five times or more the number of teeth of the driven gear.

  The present invention exhibits the following excellent effects.

  (1) The iron loss of the electric motor can be reduced.

  (2) The shaft vibration of the turbo shaft is not deteriorated.

It is a block diagram of the electrically assisted turbocharger which shows one Embodiment of this invention. It is a block diagram of the engine system carrying the electrically assisted turbocharger of this invention. It is an image figure for demonstrating the shaft vibration of a turbo shaft. It is a block diagram of the conventional electrically assisted turbocharger. It is a rotational speed versus torque characteristic view in a general electric motor.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, an electrically assisted turbocharger 1 according to the present invention includes an exhaust turbine 3 having a turbine wheel 2 that is rotated by exhaust gas, and an intake compressor 5 having a compressor wheel 4 that compresses air by rotation. A turbo shaft 6 integrated with the turbine wheel 2 and the compressor wheel 4 to transmit rotation from the exhaust turbine side to the intake compressor side, a driven gear 7 attached to a shaft vibration portion of the turbo shaft 6, and a driven gear 7 is provided with a drive gear 8 having a larger number of teeth than the driven gear 7 and an electric motor 9 for rotating the drive gear 8.

  The electric motor 9 is a general electric motor, and a rotor (not shown) rotates integrally with the rotary shaft 10. A drive gear 8 is attached to the rotating shaft 10.

  The turbo shaft 6 is supported at two locations by a bearing 11 on the exhaust turbine side and a bearing 12 on the intake compressor side. The driven gear 7 is located between the two bearings 11, 12, more specifically, at the node portion of the shaft vibration of the turbo shaft 6. The shaft vibration will be described in detail later. The drive gear 8 has a larger number of teeth than the driven gear 7, and therefore, the rotation of the electric motor 9 is increased and transmitted to the turbo shaft 6.

  As shown in FIG. 2, an engine system 21 equipped with the electrically assisted turbocharger 1 of the present invention includes a high pressure side exhaust pipe 24 connected to an exhaust manifold 23 of the engine 22, and a high pressure side exhaust pipe 24 that is connected to the exhaust turbine 3. The electric assist turbocharger 1 connected to the inlet of the exhaust gas turbine, the low pressure side exhaust pipe 25 connected to the outlet of the exhaust turbine 3, and the low pressure side intake pipe 26 connected to the inlet of the intake compressor 5 of the electric assist turbocharger 1. And a high-pressure side intake pipe 28 that is connected to the outlet of the intake compressor 5 and feeds intake air to the intake manifold 27.

  An EGR pipe 29 that circulates exhaust gas is provided from the high-pressure side exhaust pipe 24 to the high-pressure side intake pipe 28. The EGR pipe 29 is provided with an ERG cooler 30 and an EGR valve 31. The low pressure side exhaust pipe 25 is provided with an exhaust gas purification device 32, an exhaust throttle 33, and a silencer 34. The high pressure side intake pipe 28 is provided with an intercooler 35 and an intake throttle 36. An air filter 37 is provided in the low pressure side intake pipe 26.

  A power supply unit 41 and a turbo driver unit 42 are electrically connected to the electric motor 9 of the electric assist turbocharger 1, and the electric power applied from the power supply unit 41 to the electric motor 9 is adjusted and input in the turbo driver unit 42. By turning off / on, the power assisting power can be applied, eliminated, or increased or decreased. The turbo driver unit 42 is controlled by an electronic control circuit (Engine Control Module; hereinafter referred to as ECM) 43 according to a preset program.

  Next, the operation of the electric assist turbocharger 1 of the present invention will be described.

  In the electrically assisted turbocharger 1, when the rotational speed of the turbo shaft 6 is low and the intake air amount supercharged from the intake air compressor 5 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 6 is assisted from the drive gear 8 through the driven gear 7 by rotating the electric motor 9. At this time, since the rotation of the electric motor 9 is accelerated and transmitted to the turbo shaft 6, the electric motor 9 may be rotated at a lower rotational speed than the desired rotational speed of the turbo shaft 6.

  During a transient operation (for example, during overtaking operation) in which the engine state is changed to a higher-load engine state with the rotation speed of the turbo shaft 6 being high, the rotation of the turbo shaft 6 is performed by rotating the electric motor 9. To assist. At this time, the rotational speed of the turbo shaft 6 is high, but the rotational speed of the electric motor 9 is lower than the desired rotational speed of the turbo shaft 6, so that the electric motor 9 operates in a rotational speed region where the iron loss is small. used.

  Incidentally, as shown in FIG. 3, the turbo shaft 6 has a turbine wheel 2 integrally attached to one end and a compressor wheel 4 integrally attached to the other end. 11 and a bearing 12 on the axial center side of the compressor wheel 4. However, here, it is assumed that the driven gear 7 is not attached to the turbo shaft 6. In such a structure, when the turbo shaft 6 rotates at a high speed exceeding 100,000 rpm, shaft vibration occurs. The shaft vibration is a motion in which the end portion of the turbo shaft 6 is displaced in the radial direction from the center of rotation as shown in the figure, and the locus of the turbo shaft 6 draws a cone, so it is also called a rake motion. The portion corresponding to the tip of the cone is a node portion, the displacement is zero, and the displacement in the vicinity thereof is minute.

  When the displacement of the shaft vibration increases, a heavy load is applied to the bearings 11 and 12 and the bearing is damaged. However, the shaft vibration itself has a slight imbalance in the gas behavior in the turbine wheel 2 and the compressor wheel 4. Therefore, it is difficult to eliminate the shaft vibration itself. Therefore, the nodal portion of the shaft vibration is set at an optimum position so that neither the exhaust turbine side nor the intake compressor side is biased so that the displacement becomes small at the positions of the bearings 11 and 12, and a heavy load is applied to the bearings 11 and 12. Absent.

  However, when a new member called the driven gear 7 is added to the turbo shaft 6, the weight balance is changed, and further, the force from the drive gear 8 is applied. When the vibration mode of the shaft vibration is changed, the position of the node portion is deviated from the optimum position, and the displacement of either one of the bearings 11 and 12 is increased and a heavy load is applied.

  On the other hand, in the electrically assisted turbocharger 1 of the present invention, the driven gear 7 is attached to the shaft vibration node of the turbo shaft 6, and the force from the drive gear 8 is applied via the driven gear 7. Even if a member or an external force is applied to the node portion of the shaft vibration, the vibration mode is not affected. Therefore, the position of the node portion does not deviate from the optimum position, and the displacement of the bearings 11 and 12 due to the shaft vibration does not increase.

  As described above, the electrically assisted turbocharger 1 of the present invention includes the driven gear 7 attached to the turbo shaft 6, the drive gear 8 that meshes with the driven gear 7 and has more teeth than the driven gear 7, and the drive gear 8. Therefore, the electric motor 9 may be rotated at a lower rotational speed than the desired rotational speed of the turbo shaft 6, and the iron loss of the electric motor 9 can be reduced.

  Thus, according to the electrically assisted turbocharger 1 of the present invention, 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.

  In addition, since the electric motor 9 is operated at a low rotational speed, the electric assist turbocharger 1 according to the present invention does not need to employ an ultra-high speed motor, and can employ an electric motor having a general material and structure, and can reduce the cost. The rise can be suppressed.

  Further, since the electrically driven turbocharger 1 of the present invention has the driven gear 7 attached to the node portion of the shaft vibration of the turbo shaft 6, the shaft vibration of the turbo shaft 6 is not deteriorated by the addition of the driven gear 7. 11 and 12 are protected.

  The gear ratio between the drive gear 8 and the driven gear 7 is preferably 5: 1 to 20: 1. For example, when the gear ratio is 10: 1, the rotation speed of the electric motor 9 is obtained when the rotation speed of the turbo shaft 6 is 200,000 rpm. 20,000 rpm is sufficient.

  The electric assist turbocharger 1 can obtain regenerative power by using the electric motor 9 as a generator when the exhaust gas energy has a surplus. Also in this case, the power generation efficiency decreases when the electric motor 9 is at a high rotation speed. However, in the present invention, the power generation efficiency can be improved by decelerating the rotation of the turbo shaft 6 and transmitting it to the electric motor 9.

DESCRIPTION OF SYMBOLS 1 Electric assist turbocharger 2 Turbine wheel 3 Exhaust turbine 4 Compressor wheel 5 Intake compressor 6 Turbo shaft 7 Driven gear 8 Drive gear 9 Electric motor 10 Rotating shaft

Claims (2)

An exhaust turbine having a turbine wheel rotated by exhaust gas;
An intake compressor having a compressor wheel for compressing air by rotation;
A turboshaft integrated with the turbine wheel and the compressor wheel to transmit rotation from the exhaust turbine side to the intake compressor side;
A driven gear attached to a shaft portion of the shaft vibration of the turbo shaft;
A drive gear that meshes with the driven gear and has more teeth than the driven gear;
An electrically assisted turbocharger comprising an electric motor for rotating the drive gear.   2. The electrically assisted turbocharger according to claim 1, wherein the number of teeth of the driven gear is five times or more of the number of teeth of the driven gear.