Abstract:
An engine idle speed control device enhances engine cold-start performance even in engines of large displacement. The device reduces noise created by intersecting air flows after bypassing the throttle valve. The device includes first and second passages, each mounted on a throttle body for enabling air flow bypassing the throttle valve, an ISA so mounted as to control the opening of the first passage, and temperature valve unit so mounted as to control the opening of the second passage in response to engine temperature.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an engine idle speed control device adapted to bypass an engine throttle valve to provide air to an engine combustion chamber, and, more particularly, to an engine idle speed control device adapted to improve starting ability when an engine is cold and to accurately effect engine idle control.  
         BACKGROUND OF THE INVENTION  
         [0002]    [0002]FIG. 1 illustrates a conventional idle speed control device using a step motor. A throttle body  1  is mounted with an Idle Speed Control (ISC) passage  3  for bypassing a throttle valve  2 . The ISC passage  3  is equipped with an Idle Speed Control Actuator (ISA  4 ) for controlling the opening of ISC passage  3  by way of step motor, and in parallel therewith, a Fast Idle Air Valve (FIAV  5 ) is mounted to smooth engine start when the vehicle is cold-started. When the engine is cold-started, the FIAV( 5 ) is in a state of opening the ISC passage ( 3 ), such that additional air is supplied to air provided through passage  3  and ISA( 4 ), to thereby facilitate initial startup.  
           [0003]    However, there is a problem in the engine idle speed control device thus described in that the ISA( 4 ) and the FIAV( 5 ) are mounted in parallel on a single ISC passage  3 . Thus, even if the opening of FIAV( 5 ) is large, the air supplied to the combustion chamber via ISC passage  3  is restricted by the cross-sectional area of ISC passage  3 , such that full and smooth cold-starting of the engine cannot be accomplished in large displacement engines.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention provides an engine idle speed control device that facilitates cold-starting, including in large displacement engines. In accordance with a preferred embodiment of the present invention, first and second passages are mounted on a throttle body to enable air flow bypassing the throttle valve. An ISA is mounted to control the opening of the first passage. Temperature valve means is mounted to control the opening of the second passage in response to engine temperature. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    For fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings in which:  
         [0006]    [0006]FIG. 1 is a schematic drawing illustrating an engine idle speed control device according to the prior art;  
         [0007]    [0007]FIG. 2 is a rear perspective view of a throttle body mounted with an engine idle speed control device according to the present invention;  
         [0008]    [0008]FIG. 3 is a sectional view taken along line III of FIG. 2;  
         [0009]    [0009]FIG. 4 is sectional view taken along line IV of FIG. 2;  
         [0010]    [0010]FIG. 5 is a sectional view taken along V of FIG. 2;  
         [0011]    [0011]FIG. 6 is a sectional view according to another embodiment of the present invention; and  
         [0012]    [0012]FIG. 7 is a perspective view of an alternative embodiment as shown in FIG. 6. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]    Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.  
         [0014]    As shown in FIGS. 2, 3 and  4 , an engine idle speed control device according to the present invention includes a throttle body  100  equipped with a throttle valve  108  for controlling amount of air drawn into a combustion chamber in response to a driver&#39;s manipulation of the accelerator pedal. The air passage mounted with the throttle valve  108  is referred to as main passage  102 . Throttle body  100  also defines a first passage  104  and a second passage  105  for bypassing the throttle valve  108  to allow the air to pass therethrough. The first and second passage  104  and  105  are air passages communicating with an upper flow side and a lower side of the main passage  102  relative to the throttle valve  108 .  
         [0015]    First passage  104  includes therein an ISA  103  in order to control the opening size of the first passage  104  as illustrated in FIG. 3. Second passage  105  includes therein temperature valve means  107  for controlling the opening of the second passage in response to engine temperature. In a preferred embodiment, the valve means comprises a wax-driven temperature valve containing wax that is expanded or shrunken according to the temperature of engine cooling water to open the second passage when the temperature is below a predetermined temperature and to close the second passage when the temperature is above a predetermined temperature.  
         [0016]    In one preferred embodiment, the predetermined temperature for the wax-driven temperature valve to block the second passage  105  is about 50 degrees celsius. Thus, when the temperature reaches 50 degrees Celsius, the second passage  105  is completely shut off to stop additional air flow through the second passage  105 . The predetermined temperature may be appropriately otherwise selected according to engine model and operation by one of ordinary skill in the art.  
         [0017]    One surface of main passage  102  is formed with a noise-proof groove  109  connecting the outlets of the first and second passages  104 ,  105  in a downstream direction. In a preferred embodiment, where the throttle body  100  is mounted on a suction side structure (M) of the engine, such as surge tank and the like, the noise-proof groove  109  is formed between a cut-away part at the throttle body  100  and the suction side structure (M). Alternatively, the noise-proof groove  109  may be formed on the throttle body  100  independently instead of being formed with the suction side structure (M) thus mentioned.  
         [0018]    As shown in FIGS. 3 and 5, an outlet area ( 104 - 1 ) of the first passage  104  includes a curved edge part  106  to form an outlet having a smaller sectional area than the average sectional area of ISC passage  104 . The curved edge part  106  reduces or prevents noise generation when air infused into the engine via main passage  102  and air infused via the first passage  104  abruptly collide upon engine acceleration, and serves to cushion the air supplied through the first passage  104  and smooth the air flow at the intersection with the main passage.  
         [0019]    Outlet area  104 - 1 , as shaped by curved edge part  106 , forms a nozzle-like passage that directs flow from first passage  104  so as to minimize flow resistance and impact on the flow in main passage  102 . Curved edge part  106  is preferably oriented with the curved edge  106 - 2  along the upstream edge of outlet area  104 - 1 . Also, an inclined or rounded-over surface  106 - 1  on curved edge part  106  is thus preferably formed on the underside of the upstream edge of outlet area  104 - 1  (See FIG. 5) to prevent sudden collision between the air flows and to provide a streamlined route of air flow through the first passage, thereby minimizing flow resistance.  
         [0020]    In a second alternative embodiment, illustrated in FIGS. 6 and 7, the curved edge part  106  has the curved edge  106 - 2  formed only at one corner of the upstream edge of outlet area ( 104 - 1 ) into main passage  102 . When the throttle valve  108  is not in the wide open state, much more flow of air is generated at the central main passage  102 . As one of the forms to reduce the noise created thereat, part  106 - 2  is provided.  
         [0021]    Now, operation of the present invention thus constructed will be described.  
         [0022]    When an engine is started in a cold state, temperature valve  107 , disposed in second passage  105 , opens the second passage  105  in response to lower sensed temperature. Additional air is thus supplied to the air provided to the combustion chamber side of the engine through the first passage  104 .  
         [0023]    Air added through the second passage  105  can be supplied independently from the air having passed the ISA  103  to enable supply of much more air to the combustion chamber side of the engine. This is unlike the prior art where the air having passed the ISA is added by the air having passed the FIAV. As a result, even in the case where much air is required in a large displacement engine, a smooth cold starting of engine can be obtained. Also, when the engine is started at a normal temperature, an accurate engine idle control can be realized when the amount of air to the first passage  104  is accurately controlled through the ISA  103 , while the second passage  105  is completely blocked.  
         [0024]    When air is provided through the first and second passage  104  and  105  thus described, noise that might be generated as air passes the rear part of the throttle body  100  can be avoided by the noise-proof groove  109 . Noise-proof groove  109  allows the air flows supplied through the first passage  104  and the second passage  105  to be mixed smoothly and to be introduced into the combustion chamber with increased shock absorption and decreased resonance such that noise generated from the throttle body side in cold start of the engine can be avoided.  
         [0025]    When the engine reaches a normal operating condition, air passes through the main passage  102  in response to the accelerator pedal being depressed by the driver. In this hotter operating state the second passage  105  is blocked by valve  107  due to the heat of the engine cooling water. Air is thus supplied through the first passage  104  creating a chance that noise can be created by collision of air flows as described. However, noise can be avoided by prevention of sudden air flow collision by installation of rounded edge part  106 , which allows the air supplied through the first passage  104  to move along a streamlined route and to join the main air flow having already passed the main passage.  
         [0026]    As apparent from the foregoing, there is an advantage in the engine idle speed control device thus described according to the present invention in that good cold-starting can be obtained, even in an engine of large displacement. Another advantage is that air flow supplied to the engine through the first passage and air flow introduced through the main passage are smoothly joined to have the same flow direction, thereby reducing the generation of noise and obtaining a quieter engine operation.