Patent Application
20080190399
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.
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.
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.
Now referring to
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
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 (not shown) 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
In one embodiment the fluid flow control arrangement 40 may include a valve arrangement of which an exemplary embodiment is shown in
One embodiment of a valve member 46 is show in more detail in
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.
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
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.
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.
| Number | Date | Country | |
|---|---|---|---|
| 60900096 | Feb 2007 | US |
