Patent Grant
7775191
This invention relates to engines, specifically a fuel system used for engines making use of a fuel injection system.
Engine emission, such as auto emission, is one of the most contributing factors to air pollution. It is most noticeable in metropolitan areas during traffic jams, and around airports where numerous airplanes are idling in the secondary runway for 20 to 40 minutes on the average before taking off. Reducing the idle speed in internal combustion engines will save fuel when an engine is not doing much work other than keeping it alive. It also reduces exhaust emission, which converts to smog. The problem is most serious in metropolitan areas because there are more than 230 million units of light vehicles in the U.S. as of 2005, most of which are concentrated in the metropolitan areas. Another 16 million plus units of new vehicles is added to its population every year. Perhaps a more meaningful way of reducing pollution and improving energy is by measuring how much fuel is consumed per mile traveled by any vehicle at any speed. This measurement indicates the amount of fuel consumed and exhaust generated in the distance traveled. It becomes apparent that a better control of fuel consumption at slow speed (or idle) will have more impact on pollution control, fuel saving, and improvement on the city driving mileage.
Improving control of fuel consumption at low speeds must not adversely affect performance of the engine. For example, it is commonly known in physics that the kinetic energy of a moving vehicle is directly proportional to its mass (or weight). More energy is required to maintain a heavier vehicle at any speed than a lighter vehicle at the same speed. On the other hand, the amount of energy delivered by a gallon of gasoline is constant. As a result, more fuel is needed to move a heavier vehicle than a lighter one in highway driving. More fuel is also needed to accelerate a vehicle quickly. In view of these considerations, it is desirable to meet the energy demands of the engine over the full range of load conditions while also lowering fuel consumption, especially when the gas pedal is released including idle. The reduced fuel consumption will improve fuel efficiency, particularly for city driving.
Engine pistons deliver torque T to the flywheel. This is balanced by frictions of the engine and the drag by accessories like the cooling flywheel fan and generator when idle. To the first order of approximation, the balancing torque is proportional to the speed of rotation ω. The power required to keep the flywheel idling at a speed of rotation ω is Tω. It is supplied by fuel injected per second Q. The kinetic energy of the flying wheel is transmitted to the moving vehicle through mechanical means.
Since Energy delivered to the engine per second˜Q˜Tω Power produced by the engine
and Q˜ωq
hence, q˜T˜Iα˜Mω (1)
and Q˜q2 (2)
where ω is the engine speed in rps (or in rpm/60),
Fuel injectors are commonly used in today's automotive vehicles to replace earlier fuel feeding through carburetors. A fuel system generally has a fuel pump which may be either submerged in the fuel tank or positioned outside the tank, and which pumps fuel under pressure through the fuel line, to the fuel rail, into the fuel injectors. A fuel injector with a proper nozzle design sprays fuel mist at the air in-take manifold of a cylinder in an engine block. Fuel mist combined with air in proper ratio is drawn into an engine cylinder during the in-take stroke. An optimum air/fuel mix has a stoichiometric ratio of 14.7 to 1 that makes detonation easier and combustion more complete. Fuel injectors are located near (or inside) the engine cylinder at an elevated temperature. A spring loaded electro-mechanically controlled ball valve is used to seal off the nozzle of the fuel injector. This prevents pressurized fuel from seeping into the engine block when it is not running. Pressurized fuel reduces fuel vapor in the fuel line, which minimizes vapor lock; vapor lock may interfere with hot engine start-up. When an operator pushes the gas pedal, the pushing of the pedal is converted into an electric signal sent to a microprocessor. Together with the engine operating information from various sensors, the microprocessor then activates the fuel injector to deliver a pre-determined quantity of fuel to the engine cylinder through the fuel injection process.
The amount of fuel injected per pulse q is linearly proportional to the pulse width of the electrical pulse sent.
q=k(t−C) (3)
and k˜Pn (4)
where q is the amount of fuel injected per pulse,
The continuous injection rate k is a strong function of fuel pressure P. The quality of sprayed mist also depends upon the design of the shape of the nozzle. To the first order of approximation, “n” is about ½. The actual value varies between ½ and ⅓ with the latter value toward higher pressure. In other words, to double the fuel injection rate under identical operating conditions, the fuel pressure must be increased by at least 4-fold. The linearity and reproducibility must be maintained to within 1% in the linear operating range to avoid irregular engine behavior when vehicles are mass-produced. The microprocessor receives information from various sensors in the engine and determines the pulse width based upon the amount of fuel needed.
In sequential multi-port injection, a fuel injector is mounted to the fuel in-take port to a given engine cylinder (or directly into the cylinder).
At full power, where maximum fuel injection is used, an exemplary engine is running at about 6,000 rpm. Fuel in-take strokes generally last only about 5 milliseconds. In the mean time, just “opening” and “closing” a spring-loaded ball valve physically takes more than one millisecond. This sets the minimum pulse width for fuel injection during idling to no less than 2 milliseconds. The fuel injection pulse width is thus limited by the time needed for operating a spring loaded ball valve and, as a result, may have an unpredictable amount of fuel injection and cause erratic engine performance. The typical linear range to operate a fuel injector is between 2 to 10 milliseconds, for a variety of different internal combustion engines. A manufacturer generally must choose the diameter of the nozzle at a given fuel pressure to achieve maximum power at a maximum pulse width. This limits the so-called dynamic range of the fuel injection system, as the system parameters need to be chosen to achieve the desired power with the available pulse width. As a result, fuel injection systems often have too much fuel injected at the lower end of the range, that is, where there is a minimum pulse width, when idling. Thus, the dynamic range of fuel injection has room for improvement.
For example, U.S. Pat. No. 5,355,859 to R. E. Weber changes the voltage applied to a fuel pump to generate and maintain variable fuel pressure. U.S. Pat. No. 5,762,046 to J. W. Holmes et al. uses a resistor in series with the fuel pump coil. By selectively bypassing the series resistor per control signal from the microprocessor, a fuel pump will have different applied voltages to create dual speed for the fuel delivery system. However, because a fuel pump generally has a large inductive load, varying the voltage applied to the fuel pump generally does not stabilize fuel pressure for a period of seconds. This delay in fuel pump stabilization in turn causes a delay in engine response and needs fine adjustment to compensate the voltage drop across the resistor in order to maintain smooth operation. Furthermore, since only a minute quantity of fuel is needed to keep an engine alive when idle, to assure the injection is operating within appropriate linear range, the fuel pump generally must run at very low speeds. To achieve such very low speeds in the fuel pump, the voltage applied to the pump generally must also be correspondingly low. When operated on such correspondingly low voltages, the fuel pump may run sluggishly, resulting in undesirable pressure fluctuations. Also, the pump may have a shorter life and decreased reliability if it runs at variable speeds with the associated frequent and sudden acceleration/decelerations of such variances.
The response time required to change the speed of the fuel pump is unacceptably slow in comparison to the fuel injection process. Since fuel metering depends on how much fuel is being delivered by the fuel pump, undesirable pressure fluctuation generally occurs at the time when fuel injection pulses are taking place. The attempts of the art to address the above-outlined drawbacks have had mixed results at best. Excess fuel supply, a pressure regulator, and a pressure gauge are often used to minimize the pressure fluctuation during fuel injecting. A pressure release valve and an excess-fuel-return line from the fuel rail are also installed to bleed the excess fuel accumulated in the fuel rail back to the fuel tank. The hot fuel returned to the fuel tank raises the temperature in the fuel tank during prolonged operation. Precautions are also needed to recover the hot fuel vapor in the fuel system.
A constant speed multi-pressure fuel injection system has been developed. The fuel system has a pump running at a constant drive (or at a constant speed) while at the same time multiple pressure levels are created through different means. It provides the capability to instantly increase fuel supply to an engine on-demand instead of waiting for the system to stabilize before being capable of delivering more fuel. The same system is also capable of delivering much less fuel to keep the engine running when idle to save fuel.
This invention describes the structure and process of fuel injection delivery systems which create multi-pressure-levels on-demand instantly by restricting the fuel flow at a given steady fuel pump speed. This increases the dynamic range of fuel injection and minimizes fuel pressure fluctuation. Hence, the same engine that incorporates the invention is capable of doing the following: (1) Delivering more power instantly at peak load on-demand, which accelerates the vehicle from stand still to 60 miles per hour in seconds; (2) Reducing the idle speed with the engine still running smoothly, which saves fuel, improves city-driving mileage, and further reduces exhaust when idle; (3) Not changing the fuel tank temperature regardless of how long the engine is in operation; and (4) Enhancing the life of the fuel pump because the pump is running at a constant speed without frequent acceleration/deceleration. Although fuel saving and exhaust control may not seem much to a single vehicle, the cumulative effect should be noticeable in a traffic jam, or anywhere large number of vehicles are crawling with engines running. The invention can be applied to internal combustion engines used in automobiles, airplanes, and diesel engines. Thus, it saves fuel to achieve better city-driving mileage. Most of the existing vehicles already in operation for years can also be modified with minimum effort to achieve a reduced idle speed and still be able to run smoothly. When the invention is applied to a large number of vehicles, the public can enjoy the cumulative effect of cleaner air in metropolitan areas.
By adjusting constrictions of fuel flow, the fuel injection system has a wider dynamic range (defined as the ratio of the maximum amount versus minimum amount of fuel injected per second) so that it can provide instantly very low yet steady fuel pressure to deliver a minute quantity of fuel to be injected per pulse to keep the engine running smoothly even at very low speed (or idle). The same fuel injection system can also provide additional fuel pressure on-demand instantly to deliver more power when the operator has to quickly accelerate. All of these functions are accomplished while the fuel pump is running steadily at a constant speed.
In addition, a fuel-return line diverts a small portion of fuel from the output of the pump (or from the main filter) to the fuel tank to stabilize the fuel system at the predetermined pressure. In other words, the fuel-return line system minimizes fuel pressure fluctuation caused by pump metering action. It also takes away the need to bleed the excess hot fuel at the fuel rail and return it to the fuel tank to avoid pressure built-up at the fuel rail. Without hot fuel returning to the tank, the temperature in the fuel tank will remain unchanged regardless of how long the vehicle is in operation.
Depending upon the operator's desire and sensor signals from the engine, such as, but not limited to, airflow, engine speed, torque, and temperature, the fuel system can be switched from one steady state to another state at a new pressure level almost instantly without changing the drive (or speed) of the fuel pump. The stabilization of fuel pressure allows a microprocessor to predict a proper fuel injection pulse width for delivering the desired amount of fuel per pulse. It also minimizes the guessing processes to deliver a proposed fuel quantity per pulse in the split injection process commonly used in a diesel engine.
An important objective of this invention is the capability to change the fuel pressure from one steady state to another state instantly and precisely, while the pump is running at a constant speed. The pressure at each state is steady with minimum pressure fluctuation. It assures a more accurate estimate of the amount of fuel to be delivered to the engine.
Another objective of this invention is to be able to change from a normal operating fuel pressure to a very low and steady pressure instantly with minimum ripple for idle and for low speed driving while the pump is running at a constant speed at a comfortable voltage.
A further objective of this invention is to instantly switch from normal operating pressure to a higher fuel pressure on-demand for quick acceleration without changing the driving voltage applied to the fuel pump.
Yet a further objective of this invention is to constantly circulate fuel through the fuel-return line to maintain a constant fuel pressure and to avoid excess fuel and pressure built-up at the fuel-rail. Thus, hot fuel from the fuel rail does not need to return to the fuel tank and the temperature in the tank will remain unchanged regardless of how long the vehicle is in operation. Constant fuel pressure also assures a more predictable amount of fuel injected per pulse.
All of these objectives can be achieved while the fuel pump is running at a constant speed (or the drive voltage applied to the fuel pump is set at a constant value well within a comfortable linear operating range of the fuel injector). Because the fuel pump is not subjected to frequent and sudden acceleration/deceleration, the life of the pump may be prolonged.
In the drawings, which are discussed below, one or more preferred embodiments are illustrated, with the same reference numerals referring to the same pieces of the invention throughout the drawings. It is understood that the invention is not limited to the preferred embodiment depicted in the drawings herein, but rather it is defined by the claims appended hereto and equivalent structures.
While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, the invention will now be further described by reference to the following detailed description of preferred embodiments taken in conjunction with the above-described accompanying drawings.
The structures of fuel injection systems of the current invention are shown in
A. Basic Fluid System that Creates Dual-Pressure Instantly
Fuel by-pass control 30 preferably has an electromechanically controlled valve (normally closed or open depending upon its operation). Lines 35, 37 and by-pass control 30 comprise a by-pass for fuel to be partially diverted from the main fuel line 53. When fuel by-pass control 30 is normally closed, fuel pump 11 supplies fuel to the fuel injectors only. When by-pass control 30 is open, fuel pump 11 will deliver additional fuel to be by-passed through fuel lines 35, 37 back to fuel tank 10 (or pass through line 38 to fuel in-take line 51 to fuel pump 11.)
Proper restrictions are imposed on the by-pass fuel flow outlined above. For example, one may choose the size of the fuel by-pass lines 35, 37, 38 so that they provide proper flow resistance or introduce a restriction by other means. For those familiar with fluid control, the means include, but are not limited to, using a needle valve or a diaphragm-like plate with a hole that has a proper diameter for fuel restriction. Regardless of what the state of fuel by-pass control 30 is in (open or closed), fuel pump 11 runs continuously under a constant voltage drive (or at a constant speed). The changes in the fuel flow rate through the fuel pump under a constant drive create different steady fuel pressure states for the fuel supply system.
A fluid system has certain similarities to an electrical circuit, where the fuel pump is equivalent to a power source and the fuel flow rate is equivalent to current in an electrical circuit. The fluid supply system as a whole provides a steady state impedance to the pump. When the fuel by-pass control is closed (normal operating condition), the fluid system is stabilized at a quiescent state at pressure PH for a given fluid flow rate F1 (
In this invention, the higher fuel pressure PH is set for start-up and normal operation, and the maximum pulse width (about 10 milliseconds) is set for the nominal maximum power (or slightly more). When the vehicle is operating in idle or driving at slow speed, the fuel-by-pass control is switched to open. This makes the fuel system operate at a lower pressure state PL while the fuel pump is running at the same speed as before. Because not much fuel is needed other than keeping the engine alive when the vehicle is idling, a manufacturer can set fuel injection pulse width at a minimum rate (about 2 milliseconds) and set a constraint on the fuel-by-pass line to obtain the lowest fuel pressure PL which accomplishes the fuel spraying properly and allows the engine still to run smoothly. The amount of fuel injected can be very small so that it barely keeps the engine running while still running the engine smoothly.
The action to open or close the fuel by-pass control can be done manually by flipping a control switch. It can also be controlled using an embedded controller where an electronic signal is sent to activate a control circuit which activates the actuator of the fuel by-pass control switch. Suitable programming logic is used by the controller, the steps of which are shown in the flow-charts of
Generally, under a given quiescent fuel pressure P, a fuel injector operating within its linear range (typical pulse width about 2- to 10-milliseconds) has a dynamic range as shown in
i.e., (qMax)L>q>(qmin)H,
two values of pulse width exist for any given q. The design team chooses between higher pressure PH and lower pressure PL depending upon the expected driving condition and for a smooth transition without feeling roughness during the transition of pressure switching over. For those who are familiar with the state of the art of the technology, many alterations and combinations to the values for q, PH, and PL can be selected for different applications. The voltage applied to the fuel pump can also be changed to create different sets of pressure P. The combination of the new fuel system design and the changes in applied voltage will provide enough flexibility for any vehicle to run smoothly from the fuel injection point of view.
(qMax)H>qMax,(qmin)L<qmin;
and (qMax)H/(qmin)L>qMax/qmin (5)
Using the dual pressure injection system can save fuel when compared to actual single pressure injection. For example,
B. Fuel-Return Line for Fuel Pump Stabilization Temperature Stability in Fuel Tank, and Delivering An Instant Excess Power On-Demand
Using the same principle as described in the previous section, we can further improve the fuel injection fluid system by adding an extra fuel-return as shown in
The structure minimizes the dependence for the fuel pump to provide the exact amount of fuel for fuel injection and eliminates the need to return the unused excess fuel from fuel rail 17 (hot fuel) to fuel tank 10 to avoid pressure built-up. The structure also reduces the critical dependence to a fuel regulator, which contains numerous high-precision mechanical parts. Hence, the small amount of the fuel through a fuel-return line 31, 33 can stabilize the pressure and make the operation of the fuel pump steady. This minimizes the pulsating pressure spikes during fuel metering. Since no more hot fuel is returned to the fuel tank, fuel temperature in the fuel tank will remain unchanged regardless of how long the vehicle is in operation.
The amount of flow restriction imposed by fuel-return line 33 determines the value of the first quiescent pressure PH. Typically, the lower the amount of fuel flowing through the fuel-return line, the higher the quiescent pressure PH will be.
C. Fuel Injection System that Incorporates Both Inventive Features
Should the operator or system designer have a strong desire for instant high power on-demand, the system is structured to respond by closing both fuel-by-pass control 30 and fuel-return control 32 for quick acceleration. Such an operation may exceed the rating of the engine. Hence, the system should preferably allow the operator, or be otherwise designed, to perform such an operation under emergency bases and only for short time periods.
D. Flow Chart of the Microprocessor Controlled Fuel Injection Supply System
In a fuel injection supply system as shown in
An electronic pulse of the pulse width is sent to a control circuit (not shown in the
The only overriding signal occurs when the engine is overheating. In that case, the fuel-return valve will remain Open and the fuel-by-pass valve is closed. The fuel system will stay at a higher-pressure state PH. Because the engine may operate beyond its normal rating, the operation as described in
E. Modification of Vehicles Already In-Use for Improved City-Driving-Mileage & Reduced Auto Exhaust
Any vehicle already in use which uses a single pressure fuel injection system can be modified easily to include the present invention and thereby increase its city-driving mileage, save fuel, and reduce auto exhaust emission. The modification adds an electromechanical fuel-by-pass control 30 (normally closed) and fuel by-pass lines with flow constraint 35, 37 that connect from the output of fuel filter 13 (or output of fuel pump 11) to fuel tank 10 (or to the fuel in-take line 51 to fuel pump 11) as shown in
Fuel by-pass control 30 is normally closed. The modification will not affect the normal operations of the existing vehicle. When the vehicle is being used for city driving or is sitting idle, the fuel by-pass control will be open. Fuel by-pass lines 35, 37 add extra fuel through the fuel pump resulting in a reduced steady pressure PL. Hence, less amount of fuel will be injected per pulse for the same pulse width. This reduces engine idle speed, saves fuel, improves city-driving mileage, and reduces auto emission. The modification is simple and inexpensive. The benefits are especially significant in metropolitan areas where large numbers of vehicles are in operation.
It is well known that air and fuel must be mixed close to stoichiometric all the time for complete combustion and power over the entire operating range of fuel injection. The systems described above use one or two fuel by-pass paths (generic) in one of four configurations using flow restraint to stabilize fuel pressure and binary valves to create multi-pressure levels off line. During operation, the Engine Management Control constantly adjusts the opening of the throttle valve and operations of air accessories, such as a turbo charger, super charger, and coordinate the operations continuously to provide adequate air supply in response to changing fuel demand at various pressure levels.
One of the distinctive advantages of the systems described above in comparison with today's on-demand fuel injection system is the quick response (or speed) to pressure level switching, where the effect of switching is only a few milliseconds in the present systems. The pressure spike and multi-reflection of pressure waves will be over in about one or two revolutions at 3,000 rpm (instead of fractions of a second in most on-demand systems). Thus, in an example using the present system, an engine rated for 220 HP maximum power in highway driving is capable of operating like a 70 HP engine to save fuel and reduce exhaust emission in city driving. The same engine with air accessories, such as a turbo charger, supercharger, and a heavier duty fuel pump, is capable of delivering a burst of 310 HP power instantly for a short duration when there is urgent need for power producing a sport-car-like performance.
As discussed in the last paragraph, Section A in the description above, about one third of fuel will be saved every time the gas pedal is released including idling. That reduces about one third of the gap between city-driving and highway-driving mileages; or about 3 miles per gallon more in city driving mileage. A pre-fabricated kit at low cost can also be used to plug-in into the main fuel line to upgrade most existing vehicles already in-use. America has more than 230 million units of light vehicles in-use as of 2005. If similar technologies are used, potentially 5.6 billion gallons of fuel (or 340 million barrels of crude oil) a year will be saved. That translates to 950 billion cubic feet of CO2 a year (or 10 million tons of pollutants a year), which will be removed from the air in metropolitan areas. The reduced smog would provide cleaner air to greatly benefit millions of people living in the crowded metropolitan areas.
The system described above provides different fuel pressure levels under a constant fuel pump speed and has been described with reference to certain internal combustion engines. However, the system can be applied to any number of internal combustion engines or other engines making use of a fuel injection system. As such, the systems described above are applicable to diesel engines and aircraft engines that use fuel injection processes. One skilled in the art would have no difficulty applying the systems described above to other kinds of engines.
Additional advantages and variations will be apparent to those skilled in the art, and those variations, as well as others which skill or fancy may suggest, are intended to be within the scope of the present invention, along with equivalents thereto, the invention being defined by the claims attended hereto.
This application is a continuation U.S. patent application Ser. No. 10/143,657, filed on May 10, 2002 now U.S. Pat. No. 7,318,414, which is hereby incorporated by reference.
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| Number | Date | Country | |
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| Number | Date | Country | |
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| Parent | 10143657 | May 2002 | US |
| Child | 12014013 | US |
