Patent Publication Number: US-7721718-B2

Title: System for controlling an air to fuel ratio

Description:
PRIORITY 
   This application claims priority to U.S. Provisional Patent Application No. 60/900,096 filed Feb. 8, 2007, which is incorporated herein by reference in its entirety. 

   TECHNICAL FIELD 
   This disclosure relates to the field of internal combustion engines and in particular, but not exclusively, to controlling air to fuel ratios for such internal combustion engines. 
   BACKGROUND 
   Modern internal combustion engines, such as turbo charged diesel engines are the subject of stringent emission requirements. One characteristic that features in such requirements is the amount of particulates or visible smoke that an engine emits during running. Many factors influence the amount of particulates that an engine may emit such as fuel quality, operating environment and engine characteristics such as air-to-fuel ratio, speed, load and transient behaviour. One particular reason of smoke generation may be the lack of sufficient combustion air charge during aggressive transient states. One example of such transient state may be a rapid demand for the increase of power output of the engine by an operator who decides to increase the engine speed from idle to full speed by suddenly depressing the accelerator pedal fully. Since the engine accelerates in a delayed fashion, for a short time too much fuel is injected in relation to the amount of air available for combustion, which causes an incomplete combustion and possibly a drop in temperature in the combustion chamber and hence an excessive smoke development. Significant reduction of visible smoke emitted by turbocharged diesel engines upon acceleration has been achieved over the years by pressure sensitive devices such as aneroid controllers. Aneroid controllers influence the amount of fuel delivered to the injected system depending on the inlet manifold or boost pressure. 
   U.S. Pat. No. 4,727,839 describes such an aneroid controller. The controller as disclosed describes a multi-spring control arrangement to attain an improved fuel regulating characteristic rather than just a standard performance characteristic. Although the controller is compact and allegedly provides an improved regulating characteristic over the prior art, the design is complicated and may be prone to failure. The system is based on a spring loaded diaphragm having a mechanical arrangement attached for actuating a mechanism in a fuel injection pump. The diaphragm is being actuated under the influence of intake air pressure. The forces generated by the pressurized intake air are fairly weak and the system connected to the diaphragm balancing the gas forces must therefore not offer much resistance. A light spring arrangement is therefore preferred which may also improve the responsiveness of the system in general. Furthermore, as the controller is a “dry” controller, a sealing arrangement has to be in place to prevent any fuel from traveling up from the fuel injection pump into the controller. Normal tear and wear of the system in combination with the resistance offered by the sealing arrangement may hinder a proper operation of the controller. 
   The current disclosure is aimed at improving or overcoming at least some of the aforementioned disadvantages. 
   SUMMARY OF THE INVENTION 
   In a first aspect of the current disclosure there is provided a fuel system for an internal combustion engine comprising a boost control arrangement operably connectable to a fuel injection pump. The boost control arrangement has a first chamber and a second chamber separated from the first chamber by a moveable member. The first chamber is configured to receive a signal indicating a boost condition of the internal combustion engine. The second chamber is configured to contain fuel. The internal combustion engine further includes a fluid holding region fluidly connected with the second chamber and a fluid flow control arrangement between the second chamber and the fluid holding region for controlling the flow rate of fuel between the second chamber and the low pressure area. 
   In another aspect of the current disclosure there is provided a method of controlling an air to fuel ratio of an internal combustion engine. The method comprises receiving a request for a modification of a first flow of fuel to at least one combustion chamber and modifying the first flow of fuel in response to the request. The method further includes receiving a first signal indicative of a first air supply condition, displacing a second flow of fuel in response to the signal and controlling the modification of the first flow of fuel by the displacement of the second flow of fuel. 
   In yet another aspect of the current disclosure there is provided a valve arrangement for controlling flow rates into and out of a boost control arrangement of an internal combustion engine. The valve arrangement comprises a housing having a first passage portion and a second passage portion, a self-adjusting valve member slidingly engaged with said housing and positioned between the first passage portion and the second passage portion. The self-adjusting valve member has a first fluid passage fluidly connecting the first portion and the second portion of the housing. The valve arrangement further includes a second passage capable of fluidly connecting the first passage portion and the second passage portion of said housing, with the housing and the valve member being configured such that the self-adjusting valve member can adopt a position relative to the housing whereby in that position the second passage is restricted. 
   Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows an isometric representation of an internal combustion engine. 
       FIG. 2  shows a further isometric representation of the internal combustion engine of  FIG. 1 . 
       FIG. 3  is a schematical cross-sectional view of an exemplary boost control arrangement for use in conjunction with the internal combustion engine of  FIGS. 1 and 2 . 
       FIG. 4  is a diagrammatic representation of a fluid circuit for use in conjunction with the boost control arrangement of  FIG. 3 . 
       FIG. 5  is a schematical cross-sectional view of an embodiment of a fluid flow control arrangement for use in conjunction with the boost control arrangement of  FIG. 3 . 
       FIG. 6  is an isometric diagrammatical representation of a valve member of the fluid flow control arrangement of  FIG. 5 . 
   

   DETAILED DESCRIPTION 
   Now referring to  FIGS. 1 and 2 , an engine generally designated with numeral  10  is shown for exemplary purposes only. The engine  10  may for example be any suitable internal combustion engine such as a multi-cylinder turbocharged diesel engine. In one embodiment the engine  10  may be provided with an exhaust manifold  12 , an inlet manifold  14  and a turbocharger arrangement  16 . The turbocharger arrangement  16  may operate in a conventional manner such that at least a portion of exhaust gas expelled by the engine  10  flows from the exhaust manifold  12  towards the turbocharger arrangement. The exhaust gas may drive the turbocharger arrangement which in turn may then provide fresh air to the inlet manifold  14 . 
   The engine  10  may further be provided with a fuel system generally designated with numeral  17 , having a fuel injection pump  18  (FIP) which may be any suitable fuel injection pump such as a rotary or in-line mechanical fuel pump. The fuel injection pump  18  may provide fuel to any number of cylinders (not shown) of the engine  10  in a conventional manner such as via rigid fuel pipe and injector arrangements. 
   The FIP  18  may be provided with a boost control arrangement  20  (BCA) of which an exemplary embodiment is shown in  FIG. 3 . In one embodiment the BCA  20  may have a housing  22  defining two regions in the form of a first chamber  24  and a second chamber  26 . The housing  22  may be of any suitable construction and may for example be a two part housing whereby a first part  23  of the housing  22  may predominantly form the first chamber  24  and a second part  25  of the housing  22  may predominantly form the second chamber  26 . 
   The first and second chambers  24 ,  26  may be divided or separated by a moveable member  27 . The moveable member  27  may be a piston or the like and in one embodiment the moveable member  27  may be a flexible member such as a diaphragm. In the case that the moveable member  27  is a diaphragm, the moveable member  27  may be arranged such that a flange portion  28  of the moveable member  27  is clamped in between the first and second parts  23  and  25  of the housing  22 . An actuator  30  may be operably connected to the moveable member  27  such that movement of the moveable member  27  results in movement of the actuator  30 . The actuator  30  may be generally pin shaped and may be guided and or retained in a bore  32 . The actuator  30  may be operably connected with a metering portion (not shown) of the FIP  18  such that any movement of the actuator  30  may result in a changed setting of the FIP  18 . The actuator may be connected with a portion of the FIP  18  that contains pressurized fuel. The fuel may be at any suitable pressure such as for example FIP housing pressure. The clearance between the actuator  30  and the bore  32  may be selected as preferred and may be configured to act as a fuel passage  21  so as to allow the transfer of fuel from the FIP  18  to the second chamber  26 . 
   A resilient member  34 , such as for example a spring, may be arranged in the second chamber  26  so as to bias the moveable member  27  towards the first chamber  24 . The resilient member  34  may be arranged substantially central in the second chamber  26  such that the resilient member  34  surrounds at least a portion of the actuator  30 . Pressurized fuel in the second chamber  26  may also bias moveable member  27  towards the first chamber  24 . It is to be understood that the moveable member  27  may be biased towards the first chamber  24  by just the resilient member  34 , just fuel pressure in the second chamber  26  or a combination thereof. 
   The second chamber  26  may be fluidly connected with another region such as a fluid holding region  36 . The fluid holding region  36  may be any suitable region such as another chamber (not shown) or a return line to tank  36  and may be at any suitable pressure either positive, negative or neutral. It is to be understood that the fluid holding region does not imply the fluid is static, the fluid holding region may for example also include a transfer passage. In one embodiment the fluid holding region  36  is substantially pressureless. 
   Interposed between the second chamber  26  and the fluid holding region  36  there may be provided a fluid flow control arrangement  40  which may be fluidly connected to the second chamber  26  and the fluid holding region  36  by a passage  41 . The fluid flow control arrangement  40  may be configured such that it is capable of influencing the flow rate of fuel between the second chamber  26  and the fluid holding region  36 . The fluid flow control arrangement  40  may be configured such that it includes geometric flow control features such that the discharge coefficient for fluid flow in one direction is substantially different to the discharge coefficient for fluid flow in the opposite direction. 
   In one embodiment the fluid flow control arrangement  40  may be configured such that it defines a first cross-sectional fluid flow area to allow a first fuel flow from the second chamber  26  to the fluid holding region  36  and a second cross-sectional fluid flow area to allow a second fuel flow from the fluid holding region  36  to the second chamber  26 , whereby the second cross-sectional fluid flow area may be greater than the first cross-sectional fluid flow area. Such relationship may for example be expressed in a fluid diagram as shown in  FIG. 4 . When fluid flows from the fluid holding region  36  to the second chamber  26 , fluid can flow both through the first passage  31  and the second passage  33 . However, when the fluid flows from the second chamber  26  to the fluid holding region  36 , the valve  35  which in this example is shown as a one-way shuttle valve, may be at least partially closed off so as to at restrict the flow through the passage  33 . Restricting in this context may be interpreted as the fluid either being hindered or blocked altogether. The valve may be of any suitable design. In one embodiment the valve  35  is self-adjusting in that it is responsive to a fluid flow and may react to the fluid flow without any external input, i.e. it is capable of adjusting its own position under the influence of a fluid flow. It can be seen that the cross-sectional fluid flow area is greater when the fluid flows from the pressure region  36  to the second chamber  26 , because both the passages  31  and  33  are fully open or at least more so than in the opposite direction. It is to be understood that the passage  31  may be sized so as to act as a restrictor or it may be provided with a restrictor such as an orifice so as to be able to tailor standardized bodies with suitable orifices. 
   In one embodiment the fluid flow control arrangement  40  may include a valve arrangement of which an exemplary embodiment is shown in  FIG. 5 . A valve arrangement generally designated with numeral  42  may have a housing  44 . The housing  44  may be a single piece construction or may be constructed from multiple pieces. A valve member  46  may be slidingly engaged with said housing. For ease of reference the housing  44  will be described as having a first passage portion  48  and a second passage portion  50  whereby the first passage portion  48  is that portion which is located left from the valve member  46  as seen in  FIG. 5  It follows that the second passage portion  50  is that portion which is located right from the valve member  46  as seen in  FIG. 5 . It is to be understood that the exact boundaries of the first and second portions  48  and  50  are relative and depend on the position of the valve member  46 . 
   One embodiment of a valve member  46  is show in more detail in  FIG. 6 . The valve member  46  may be manufactured as a single piece component. A first end portion  52  may be tapered so as to form a generally conical shaped nose portion that corresponds to a counter surface  57  of the housing  44 . The first end portion  52  may be provided with a longitudinal fluid passage  56  fluidly connecting a chamber  58  of the valve member  46  to the first passage portion  48 . A second end portion  54  may be provided with at least one radial fluid opening  60  fluidly connecting the chamber  58  to the second passage portion  50 . In one embodiment the fluid openings may for ease of manufacturing be formed as slots  62  in the second end portion  54  so as to create a castellated end portion  54 . However, any suitable alternative to connect the chamber  58  with the environment external of the valve member  46  may be chosen such as, for example, round passages formed by casting, moulding, sintering or a machining operation such as drilling. The valve member  46  may have a substantially circumferential shape as preferred. In one embodiment, the valve member may be provided with at least one surface  66  and at least one convex surface  64 . The convex surface  64  may be regarded as a positioning surface so as to position the valve member  46  relative to the body  44 . The surface  66  may be less convex than the convex surface  64  and may be for example be substantially flat or substantially concave. When the valve member  64  is engaged with the housing  44  the convex surface  64  may be spaced more closely to the internal wall  45  of the housing  44  than the surface  66 . The housing  44  and the surface  66  may therefore form a passage  68  external of the valve member  46  capable of allowing fluid to transfer between the first end portion  52  and the second end portion  54 . In this embodiment the passage  56  may perform the function of the passage  31  whilst the passage  68  may perform the function of the passage  33 . Whenever the valve member is in the position such that the first end portion  52  is close to, or contacts the corresponding counter surface  57 , the passage  68  may be at least partially blocked off and may therefore perform the function of the valve  35 . 
   Alternatively a passage equivalent in function to passage  68  or  33  may be predominantly or completely formed in or by the body  44  rather than being predominantly formed by the surface  66  being spaced away from a surface of the body  44 . 
   It is to be understood that this valve arrangement may be regarded as self-adjusting as referred to above. 
   INDUSTRIAL APPLICABILITY 
   During use, the engine  10  operates in a conventional manner. The FIP  18  supplies fuel to the engine  10  which may be combusted with air supplied via the inlet manifold  14 . After combustion the exhaust gasses may be vented via the exhaust manifold  12 . The turbocharger arrangement  16  may be driven by the exhaust gasses flowing from the exhaust manifold  12 . The turbocharger arrangement  16  may in turn then pressurize air in the inlet manifold  14 . 
   During operation a request for a modification of a first flow of fuel to at least one combustion chamber may be received. For example, the engine  10  may be in a boost condition which may be described as a condition in which relatively large increase of power output of the engine  10  is requested in a relatively short period of time. This may for example happen when during operation of a work machine, the operator requests an increase in power output of the engine  10  by actuating a machine function such as for example moving an accelerator pedal or hand throttle (not shown) from a first position corresponding to a lower engine speed to a second position corresponding to a higher engine speed. In response to the request for the modification of the first flow of fuel the first flow of fuel may be modified. In such circumstances it is possible that the rate of increase of the fuel that is injected for combustion is higher than the rate of increase in the quantity of air required for a satisfactory combustion, i.e. the air-to-fuel ratio is not as well controlled as desired. The rate of increase in the quantity of air may be expressed via an indicative signal. For example, the gas pressure in one of the inlet manifold  14  and the exhaust manifold  12  may be used to receive a signal indicative of an air supply condition such as the amount of air available for combustion. In one embodiment the signal relates specifically to the gas pressure in the inlet manifold  14 . The signal may be generated in any form such as for example an electric signal generated by a sensor which may then be sent to, and received by, the BCA  20  either in a direct or indirect manner. In one embodiment the signal may be provided by having the BCA  20  fluidly communicate with a manifold such as the inlet manifold  14 , such that the BCA  20  may receive a gas pressure corresponding to the gas pressure in the inlet manifold  14 . The gas pressure may be received by the first chamber  24  and may act upon the moveable member  27  so as to displace the moveable member  27 . Displacing in this context may be interpreted as displacing at least a portion of the moveable member  27 . The moveable member  27  may in turn displace the actuator  30  such that the actuator  30  or another related mechanism influences the metering or output of the FIP  18 . It can therefore be seen that a signal corresponding to a higher gas pressure may influence the FIP  18  more than a signal corresponding to a lower gas pressure. 
   During a request for increase of power output of the engine  10 , the FIP  18  may increase its output in direct relationship to the request, for example, moving an accelerator pedal or hand throttle may directly increase the fuel output of the FIP  18 . In addition, the BCA  20  may increase the rate of fuelling even further in response to a signal indicative of a boost condition in which sufficient air is available to burn additional fuel in an acceptable manner. 
   To balance the BCA  20 , the resilient member  34  may bias the moveable member to the first chamber  24 . An increased signal generated by the gas pressure may therefore overcome the force provided by the resilient member  34  and the resilient member  34  may be compressed. If the resilient member is a spring, the relationship of force and compression may be substantially linear which therefore leads to a substantially linear counteracting force to the signal as transferred by the moveable member  27 . 
   The second chamber  26  of the BCA  20  may be provided with fuel that flows from the FIP  18  via the passage  21  between the actuator  30  and the bore  32 . The passage  21  may be relatively small which may therefore result in the second chamber  26  being filled at a relatively low rate. During operation a first signal may arrive at the BCA  20  whereby the signal may be indicative of a first air supply condition such as a first boost condition. This may for example be a condition wherein a sharp increase of power output from the engine  10  is requested. The signal may in case of a BCA  20  having a moveable member  27 , displace the moveable member  27  against the resistance offered by the resilient member  34 . The displacement of the moveable member  27  increases the fluid pressure in the second chamber  26 . Not all of the fluid present in the second chamber  26  may be able to escape back to the FIP  18  via the passage  21  due to the passage  21  being relatively small. The pressurized fluid in the second chamber  26  may then be displaced as a second flow of fuel towards the fluid holding region  36  via the passage  41  and the fluid flow control arrangement  40 . It is therefore to be understood that the second flow of fuel is displaced in response to receiving the signal. As described above, the fluid flow control arrangement  40  may be provided with a particular first cross-sectional fluid flow area to allow a first fuel flow rate from the second chamber  26  to the fluid holding region  36 . Therefore when the moveable member  27  displaces the fluid from the second chamber  26  towards the fluid holding region  36  the rate of the fuel escaping the second chamber  26  may be tailored such that an additional resistance is provided to the moveable member  27  in conjunction with the resilient member. The rate of displacement of the moveable member  27  is therefore dependent on the resistance as offered by the resilient member  27  which may be substantially linear and the resistance as offered by the displacement of the fluid over the fluid flow control arrangement  40  which may be substantially non-linear. Hence by sizing the passage  31  a non-linear resistance to displacing the fluid may be selected. The displacement may for example be influenced by forcing the fluid to flow through an orifice. By influencing the rate of adjustment of the metering portion of the FIP  18  it is possible to tailor the increase of fuel as provided by the FIP  18  for combustion in relation to the air available for combustion, i.e. the modification of the first flow of fuel is controlled by the displacement of the second flow of fuel. The restriction as offered by the fluid flow control arrangement  40  may also be tailored to different engine applications such as for example heavy duty agricultural work, light duty construction work etc. 
   During operation a second signal may be received by the BCA  20  whereby the signal may be indicative of a second air supply condition such as for example a second boost condition wherein a request for a sharp increase of power output from the engine  10  is interrupted. This may be related to the first signal such that the second signal is indicative of a second gas pressure, whereby the first gas pressure is higher than the second gas pressure. In this condition the resistance offered by the resilient member  34  and any fluid pressure in the chamber  26  may force the moveable member  27  back towards the first chamber  24 . It is desirable to replace the fluid previously displaced from the second chamber  26  so as to prepare the second chamber for the next event similar to the first boost condition. However, due to the passage  32  being relatively small and incapable of rapidly providing a sufficient quantity of fuel, there is a risk of the second chamber being only partially refilled when the next event commences. This may be undesirable and at least a portion of the fluid that was previously displaced into the passage  41  may return to refill the second chamber  26  so as to replace the previously displaced fluid. Because a rapid refill is desirable it may be preferred to provide an increased discharge coefficient or increased cross-sectional flow area, such as an additional passage, that allows an unhindered or less restricted flow of fluid towards the second chamber. Hence during the second boost condition fuel can flow from the pressure region  36  towards the second chamber  26  via the passage  33 , but additionally it can flow through the passage  33  and the valve  35 . By allowing fuel to flow back through both the passages  31  and  33  a greater fuel flow cross-sectional area is provided enabling a higher rate of fuel flow into the second chamber  26  as compared to allowing the fuel to flow just through the passage  31 . 
   In an embodiment using the valve arrangement  42  as shown in  FIGS. 5 and 6  the process may be as follows. During a first boost condition the fluid may flow from the second passage portion  50  to the first passage portion  48 . The flow acts upon the valve member  46  such that the valve member assumes a first position such that the first end portion  52  and the counter surface  57  may come together thereby restricting the passage  68  which is equivalent to restricting the passage  33  as shown in  FIG. 4 . Restricting in this context may be interpreted as a partial or total closing of at least one passage. Hence most or all of the fluid may then flow from the second passage portion  50  through the chamber  58  and the longitudinal fluid passage  56  towards the first passage portion  48 . During a second boost condition the fluid may flow from the first passage portion  48  to the second passage portion  50 . The flow acts upon the valve member  42  such that the valve member  46  is forced in a direction which is generally away from the first passage portion  48 , thereby assuming a second position and opening, or further opening the passage  68 . In this case fluid may flow from the first passage portion  48  to the second passage portion  50  via the longitudinal fluid passage  56  and the chamber  58 . In addition the fluid may flow from the first passage portion  48  to the second passage portion  50  via the passage  68 , the radial fluid opening  60  and again the chamber  58 . 
   It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed system. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed method and apparatus. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.