Patent Application
20070160455
The present invention relates to a secondary air fan used in an exhaust system for a motor vehicle.
When an engine goes through a cold start condition a secondary air flow fan can be used to inject air into the engine's exhaust system. The reason the air is injected into the exhaust system is so that oxygen is present in the exhaust system and causes excess hydrocarbons to be combusted. This also helps the catalytic converter to perform efficiently or achieve optimal temperature in a shorter amount of time.
An impeller fan can be used to create the air movement in the secondary air flow system. One phenomena that can occur with secondary air flow systems is what is referred to as “dead head” condition. A dead head condition is when the air flow or output channel from the impeller becomes blocked. In other words, due to impeller design the pump will reach relatively high pressures at dead head and prevent the downstream valve from closing.
Furthermore, as the pressure increases the electrical current drawn by the motor increases. This is an undesirable condition because it is a drag on the vehicle electrical system. Therefore, it is desirable to develop an impeller that would reduce the pressure at the dead head condition, and thus reduce the amount of current drawn by the impeller.
The present invention relates a secondary air system having a regeneration air pump wherein the vanes of the impeller are tapered from a point along the length of the vane to the base of the vane inside the air pump. The tapered vanes create desirable flow characteristics. The impeller arrangement provides an ideal flow characteristic that prevents high pressure from restricting the movement of the downstream valve. Thus, the tapered vanes create a non-linear flow versus pressure characteristic. This non-linear characteristic created by the tapered vanes allows the secondary air system to maintain suitable operation at lower flow and pressure levels. In addition, the tapered vanes of the impeller fan also function as a relief feature which creates a pressure loss as pressure builds in the system. Since the pressure in the secondary air system is reduced, a lower pressure is obtained at a dead head condition. The impeller arrangement also improves overall pump efficiency. All in all the invention described herein provides a secondary air system where the dead head pressure characteristics created in the secondary air system will be lower than the standard dead head pressure so that the valve can function properly, out of the range of undesirable back pressures and high currents.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
a is a top plan view of a vane with Line A-A depicting the thickness of the vane;
b is a side plan view of a single vane with Line B-B depicting the height of the vane;
The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
Referring to
Vanes 32 are spaced circumferentially around the impeller frame 26. The spacing of the vanes 32 around the outer radial surface 18 creates vane grooves 34 between each of the vanes 32. The vanes 32 have a base 35 that is connected to an impeller frame 26. The vanes 32 are angled at a point 40, such that neither an outer angled surface 42 nor the base 35 extend directly radially from the impeller frame 26. The vanes 32 have an inner angled surface 38 and the outer angled surface 42, which meet at the point 40, and the angle at which the vane 32 extends from the impeller frame 26 can be altered. Thus, the point 40 can be anywhere along the length of the vane 32.
Furthermore, vanes 32 have a tapered thickness that is shown in
b and 2 depict a side view of an individual vane shown in
The pressure relief feature 37 in the height of the vanes 32 changes the flow characteristics of impeller fan 10, so that a dead head pressure is reduced when compared to the dead head pressure created by a standard impeller fan. The vanes 32 in combination with the pressure relief feature 37 all contribute to pressure relief provided by impeller 10. If the divider 36 is used, it will create an upper flow area 48 and a lower flow area 50. The impeller fan 10 having vanes 32 in conjuncture with the divider 36 increases the flow, whereas an impeller fan that has no divider decreases the flow.
The pressure relief feature 37 of the vanes 32 and the divider 36 create a flow rate in the upper flow area 48 and a flow rate in the lower flow area 50. Both the upper flow area 48 and the lower flow area 50 have a pressure leakage between the inlet and outlet along the sealing area via the pressure relief feature 37. The leakage reduces the pressure in the upper flow area 48 and the lower flow area 50, which in turn reduces the dead head pressure. Thus, the reduction of the dead head pressure also reduces the amount of current drawn by the impeller 10.
Referring to
The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.
