Patent Publication Number: US-2010115929-A1

Title: Current limiting driver for electric air pump

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a PCT International Application which claims the benefit of U.S. Provisional Application No. 60/920,161, filed Mar. 27, 2007. The disclosure of the above application is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a current limiting arrangement for a vehicle secondary air supply system. 
     BACKGROUND OF THE INVENTION 
     When an engine goes through a cold start condition a secondary air supply device can be used to inject air into the engine&#39;s exhaust manifold. This allows oxygen to be introduced to the exhaust and cause excess hydrocarbons to be combusted. This also helps the catalytic converter achieve optimal temperature in a shorter amount of time. 
     Using secondary air supply devices can cause electric current surges into an actuator of an air pump when the actuator is initially energized from the cold start condition. This power surge is known as in-rush current. A surge of in-rush current into the actuator can cause undesirable conditions in the vehicle electrical system. Therefore, it is desirable to develop a current limiting arrangement wherein the actuator of the secondary air supply device is operably connected to a pulse width modulated controller to control the in-rush current. 
     SUMMARY OF THE INVENTION  
     The present invention relates to a secondary air supply arrangement having an actuator operably connected to an air pump for creating air flow between an inlet and outlet of the air pump. A pulse width modulated controller is operably connected to the actuator for applying a pulse width modulated voltage to the actuator. The pulse width modulated controller controls the initial in-rush electric current when the actuator is activated. 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of the secondary air supply arrangement having the pulse width modulated controller connected remotely; 
         FIG. 2  is a perspective view of the secondary air supply arrangement having the pulse width modulated controller mounted to the air pump; 
         FIG. 3  is an exploded view of the secondary air supply arrangement having the pulse width modulated controller integrated within the actuator; 
         FIG. 4  is a schematic diagram showing a current limiting arrangement; 
         FIG. 5   a  is a line graph illustrating the implications of in-rush current when no pulse width modulation is applied; and 
         FIG. 5   b  is a line graph showing the current controlled when the actuator of the secondary air supply arrangement is operably connected to the pulse width modulated controller. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     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 generally to  FIGS. 1-4  a secondary air supply arrangement is generally shown at  10  wherein the actuator generally shown at  12  receives electric current and is operably connected to the air pump generally shown at  14 . The actuator  12  is covered by a casing  16  that is connected to a housing  18  of the air pump  14 . The air pump  14  has an inlet  20  and an outlet  22  in which the air flows in and out of the air pump  14  respectfully. 
     The actuator  12  energizes the air pump  14  causing an impeller  24  to rotate and cause air to flow through the inlet  20  and outlet  22 . It is understood, however, that a pumping fan or other mechanism can be used as an alternative to the impeller  24 . 
     The pulse width modulated controller  26  is connected to a battery  28  and receives energy from the battery  28 . It is understood, however, that any conventional energy source can be used. The pulse width modulated controller  26  is operably connected to the actuator  12  and controls the amount of voltage applied to the actuator  12 . The air flow generated by the air pump  14  corresponds with the amount of voltage applied to the actuator  12  by the pulse width modulated controller  26 . The in-rush current experienced by the actuator  12  can be controlled to be less than or equal to 150 amps. when the actuator  12  is initially activated. However, the current range can vary depending on the needs of a particular application. 
     A pump relay  30  is coupled to or integrated with the pulse width modulated controller  26  and operably connected to the actuator  12 . The pump relay  30  receives a signal from an electronic control unit  32  and acts as an on/off switch for allowing the application of voltage and flow of current to the actuator  12 . However, it is not necessary for the pump relay  30  to be present for the pulse width modulated controller  26  to control the amount of voltage applied to the actuator  12 . 
     A valve  34 , as shown in  FIG. 4 , is operably connected to the outlet  22  of the air pump  14  for controlling the flow of air to the engine&#39;s exhaust manifold  36 . A valve relay  38  is operably connected to the valve  34  and acts as an on/off switch to energize the valve  34 . The valve relay  38  can be coupled to the pulse width modulated controller  26  and the pump relay  30 , generally shown at  40 , however, the valve relay  38  controls the activation of the valve  34 . 
     Referring to  FIG. 1 , one secondary air supply arrangement  10  includes the pulse width modulated controller  26  located remotely from a secondary air supply device  42 . Electric current from the battery  28  flows through a connection to the pulse width modulated controller  26 . The pulse width modulated controller  26  applies a pulse width modulated voltage to the actuator  12  either through the pump relay  30  or directly. The actuator  12  energizes the air pump  14  causing air to flow through the inlet  20  and outlet  22  respectfully. 
     The pulse width modulated controller  26  and the pump relay  30  can alternatively be coupled to or integrated with the electronic control unit  32  located remotely from the secondary air supply device  42 . The pulse width modulated controller  26  applies a pulse width modulated voltage to the actuator  12  either through the pump relay  30  or directly. 
     Referring to  FIG. 2 , an alternative secondary air supply arrangement  10  includes the pulse width modulated controller  26  as a solid state device connected on a top of a cover  46  of the air pump  14 . However, it is understood that the pulse width modulated controller  26  can be connected anywhere on the outside of the secondary air supply arrangement  10 . Electric current from the battery  28  flows through a connection to the pulse width modulated controller  26 . The pulse width modulated controller  26  applies a pulse width modulated voltage to the actuator  12  either through the pump relay  30  or directly. 
     Referring to  FIG. 3 , yet another alternative of the secondary air supply arrangement  10  is shown, wherein the pulse width modulated controller  26  is coupled to or integrated with the actuator  12 . However, it is understood that the pulse width modulated controller  26  can be integrated anywhere within the secondary air supply device  42 . The actuator  12  is operably connected to the air pump  14  for creating air flow between the inlet  20  and outlet  22  of the air pump  14 . The housing  18  of the air pump  14  houses the impeller  24  and includes an electrical port  48 . A lower flow chamber  50 , having the outlet  22 , is connected to the housing  18  and houses a particulate filter  52 . The cover  46 , having the inlet  20 , is connected to the lower flow chamber  50 . Air flows in and out of the inlet  20  and the outlet  22  of the air pump  14  respectfully. 
     The battery delivers electric current through the electrical port  48  to the pulse width modulated controller  26 . The pulse width modulated controller  26  is operably connected to the actuator  12  and directly controls the voltage applied to the actuator  12 . However, it is understood that the pump relay can be coupled to or integrated with the pulse width modulated controller  26 , wherein the pulse width modulated controller  26  applies a pulse width modulated voltage to the actuator  12  through the pump relay. 
     Referring to  FIG. 4 , a schematic diagram of a secondary air supply arrangement  10  having the valve relay  38  is shown. Electric current commanded by the electronic control unit  32  flows through the connection to the pump relay  30  that is coupled to or integrated with the pulse width modulated controller  26 . The pulse width modulated controller  26  applies a pulse width modulated voltage to the actuator generally shown at  12  either through the pump relay  30  or directly. The actuator  12  energizes the air pump generally shown at  14  causing the impeller to rotate and cause air to flow through the inlet  20  and the outlet  22  respectfully. A valve relay  38  is operably connected to the valve  34  and acts as an on/off switch to energize the valve  34  and control the air flow to the engine&#39;s exhaust manifold  36 . The valve relay  38  can be coupled to the pulse width modulated controller  26  and the pump relay  30 , generally shown at  40 , however, the valve relay  38  controls the activation of the valve  34 . 
     Referring to  FIG. 5   a , the graph illustrates the in-rush current developed due to activation of the air pump when it is initially activated at the engine&#39;s cold start condition until full flow is achieved. A Line  54  depicts the unfavorable condition of the in-rush current exceeding 150 amps. and the pulse width modulated controller is not in use. 
     Referring to  FIG. 5   b , Line  56  depicts the in-rush current controlled to less than or equal to 150 amps. when the pulse width modulated controller is used to apply a pulse width modulated voltage to the actuator of the secondary air supply device. The in-rush current can be controlled to be less than or equal to 150 amps. When the actuator is initially energize, however, the specific amperes can vary depending on the needs of a particular application. 
     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.