Patent Application
20120070316
This application claims the priority of German Patent Application, Serial No. 10 2010 011 147.3-15, filed Mar. 11, 2010, pursuant to 35 U.S.C. 119(a)-(d), the content of which is incorporated herein by reference in its entirety as if fully set forth herein.
The present invention relates to a pressure wave supercharger for installation on an internal combustion engine of a motor vehicle.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Internal combustion engines for motor vehicles are supercharged to increase efficiency. The gas exchange is improved during the intake cycle through increase of the charging degree of the cylinder. Supercharged engines consume less fuel compared to engines that are not charged. A supercharged motor is able to burn a same amount of air-fuel mixture as an engine with greater capacity, when the internal resistance is the same.
Supercharging systems to generate gas dynamic processes in closed gas channels for supercharging internal combustion engines are generally designated as pressure wave superchargers or pressure wave machines. Cell rotors used in pressure wave machines have typically a cylindrical configuration and have channels which have predominantly constant cross section and extend from the hot gas side to the cold gas side.
Pressure wave superchargers are currently operated by electric motors to replace belt drives used before to drive a cell rotor. Electric motors are connected via a coupling directly with the rotor shaft. As a result, the rotation speed can be freely selected within functional requirements depending on the operating state and independently controlled by the rotation speed of the crankshaft of the internal combustion engine.
As the available installation space in proximity of the internal combustion engine is limited, pressure wave superchargers should be dimensioned as compact as possible. In addition, the electric power consumption should be minimized. Thus, force-locking connections such as couplings and bearings should be dimensioned to encounter smallest possible friction while still realizing maximum system stiffness. To provide the required system stiffness to oppose flexure and vibration behavior, the provision of a combination of fixed bearing and movable bearing is proposed for the cell rotor or cell rotor shaft in order to secure these components in an axial position. The electric motor coupled to the shaft has hereby a separate bearing. The individual lengths and the individual frictions encountered in the bearings add to a total length and total friction, respectively, which adversely affect power loss of the rotor drive and structural size.
It would therefore be desirable and advantageous to address these problems and to obviate other prior art shortcomings.
According to one aspect of the present invention, a pressure wave supercharger includes a housing, a cell rotor arranged in the housing, an electric motor for driving the cell rotor, the electric motor including a rotating member which is connected to the cell rotor, and a fixed member, and a bearing assembly to simultaneously support the cell rotor within the housing and rotatably support the rotating member in relation to the fixed member.
The present invention resolves prior art problems by providing an electric motor which is configured as electromotive converter with a rotating member and a fixed member to generate mechanical energy. Friction is kept to a minimum by supporting the cell rotor in relation to the housing by the same bearing assembly that is provided to also support the fixed member (armature) in relation to the rotating member (stator) of the electric motor.
By providing a common bearing assembly, individual lengths of the components, i.e. bearings, can be reduced. The number of bearing points is reduced so that less friction is encountered and thus also less power loss. At the same time, the decrease in bearing components results in a pressure wave supercharger which can be made compact, lightweight, and thus requires less installation space.
According to an advantageous embodiment of the present invention, a cell rotor shaft can extend in one piece through the electric motor and is connected to the cell rotor, wherein the rotating member is mounted to the cell rotor shaft and surrounded by the fixed member to configure the electric motor as an internal rotor, with the bearing assembly supporting the cell rotor shaft and thereby supporting the rotating member in relation to the fixed member and supporting the cell rotor in relation to the housing. The fixed member is hereby secured to the housing. As the single-piece cell rotor shaft extends from the cell rotor and through the electric motor, the need for a separate output shaft of the electric motor and a coupling to connect a cell rotor shaft with the output shaft is now eliminated. The single-piece cell rotor shaft upon which the rotating member (armature) is arranged thus extends from the cell rotor. A first bearing point of the bearing assembly may hereby be provided between the cell rotor and the electric motor.
According to another advantageous feature of the present invention, the cell rotor shaft can be configured to taper in steps from the cell rotor in a direction of the electric motor. This creates bearing seats such as snug fits for bearings and also the required seat for the armature. A benefit of a configuration involving a shaft which extends from the cell rotor is the possibility to secure all following components in succession through shrinkage or pressing. When configured as an internal rotor, the electric motor is supported on the shaft of the cell rotor but not vice versa. The supporting cell rotor shaft may thus also be designated as a cell rotor shaft having bearing points on one side of the cell rotor but on both sides of the electric motor.
By eliminating the need for a bearing that is specifically provided for the electric motor, it is possible to install the electric motor virtually in a riding manner on the cell rotor shaft. The electric motor in turn is integrated in the housing of the pressure wave supercharger. There is no need for a separate housing for the electric motor. This saves weight and space. An essential feature, however, is the presence of a bearing assembly which supports the cell rotor shaft and at the same time supports the electric motor.
According to another advantageous embodiment of the present invention, the bearing assembly may include a bearing pin which is connected to the housing, with the fixed member being mounted to the bearing pin and surrounded by the rotating member to configure the electric motor as an external rotor, with the rotating member being connected to the cell rotor. The outer member of the electric motor is thus configured as rotating outer member which is connected with the cell rotor. The fixed member of the electric motor is thus positioned on the inside and arranged on the bearing pin. Suitably, the bearing pin is configured as hollow pin.
According to another advantageous feature of the present invention, the electric motor may be accommodated in the cell rotor. As a result, the electric motor is not positioned in axial offset relation to the cell rotor but is located directly inside the cell rotor. While this configuration may result in a cell rotor of greater diameter, its length is significantly reduced compared to a solution with axially offset electric motor.
The compact size with fixed hollow bearing pin allows the energy supply to the electric motor to be provided through the bearing pin. In addition, it is also possible to incorporate a coolant supply and coolant removal through the bearing pin. An example of coolant is fresh air that is drawn into the pressure wave supercharger. The coolant supply thus involves a vent channel.
In both the internal rotor variation and external rotor variation, a pivot bearing pair can be provided to support the armature together with the cell rotor in relation to the stator or housing. The housing provides hereby a torque support for the cell rotor and the armature. The cell rotor is thus rotatably supported solely by the pivot bearing pair in relation to the housing.
According to another advantageous feature of the present invention, an axial compressor can be arranged on the cell rotor shaft and constructed to raise a pressure level of cooling air being drawn into the cell rotor. Suitably, the axial compressor is positioned upstream (anteriorly) of the electric motor. The axial compressor forces a coolant flow through one or more compressor stages (bladed wheels).
Cooling of the stator winding of the electric motor is realized via the laminated stator core and the intake of fresh air which flows through the fan of the pressure wave supercharger. Heat dissipation takes place by heat conduction and convection and/or separate cooling channels which divert a portion of intake air directly to motor cooling.
A pressure wave supercharger according to the present invention has many benefits, which include compact size as a result of a reduced total system length. Compared to prior art approaches, at least three components are eliminated, namely a motor bearing, a coupling, and a motor support or motor flange. There is no friction between motor bearing and possible coupling frictional forces. The mass moment of inertia is reduced and smaller acceleration forces are required so that the pressure wave supercharger according to the invention can respond much faster.
Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:
Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.
Turning now to the drawing, and in particular to
The electric motor includes a rotating member 6 (rotor or armature) which is arranged on the cell rotor shaft 3 and a fixed member 7 (stator) which is disposed in surrounding relation to the rotating member 6. As in the embodiment of
As shown by way of example in
The electric motor 8 is cooled by cooling air sucked in and forced to flow through passageways (not shown) in the bearing pin 12. As indicated by arrows P in
Although not shown in detail, the bearing pin 12 may accommodate also an energy supply for the electric motor 8.
Referring now to
While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.
What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein:
| Number | Date | Country | Kind |
|---|---|---|---|
| 102010011147.3-15 | Mar 2010 | DE | national |
