Patent Application
20090139494
The present disclosure relates to fuel pumps. More particularly, the present disclosure relates to dual piston direct injection fuel pumps.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Conventional gasoline engines are designed to use an electronic fuel injection system, replacing the traditional mechanical carburation systems. Port-Fuel Injection (PFI), where the fuel is injected through each intake port, is currently one of the popular systems used today. Although PFI provides a drastic improvement in response and quality, it is still limited due to the fuel and air mixing prior to entering the engine's cylinder.
In order to further increase response time and combustion efficiency, while lowering the fuel consumption and increasing output, designers are turning towards direct injection systems. Gasoline direct injection engines are engineered to inject the gasoline directly into the engine's cylinder in a manner similar to diesel direct injection engines.
Direct injection systems are designed to allow greater control and precision, resulting in better fuel economy. This is accomplished by enabling combustion of an ultra-lean mixture under many operating conditions. Direct injection is also designed to allow higher compression ratios and to deliver higher performance with lower fuel consumption.
In a direct injection system, the gasoline is highly pressurized because it is injected via a common rail fuel line directly into the combustion chamber of each cylinder. In PFI systems, or low pressure applications, turbine impeller fuel pumps can be used to deliver fuel from the fuel tank to the fuel rails and cylinders of the engine. However, conventional turbine impeller fuel pumps cannot deliver fuel at the pressures required by the direct injection systems. Piston type fuel pumps are more capable of delivering the fuel at these higher fuel pressures.
Current designs for piston type fuel pumps incorporate a single piston/cylinder design. The newer designs for vehicle engines include engines that have higher outputs and/or engines for flex fuel vehicles. These newer designs for engines require a higher flow rate of fuel and the current single piston/cylinder designs for fuel pumps are not able to meet this increased flow rate requirement.
One typical solution is to add a second fuel pump to an engine which would then double the amount of fuel delivery. Although this does solve the problem, adding a second fuel pump is expensive and packaging space to mount the second pump is limited.
The present disclosure provides a fuel pump which meets the increase in flow rate requirements without adding a second pump. The pump design of the present disclosure is a dual piston design which makes use of one pump which has twice the delivery rate. Even though the dual piston pump is larger in size due to the second cylinder, the overall packaging required to mount the pump is less than the overall packaging for a second pump.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
Fuel tank 16 is typically located in the rear of vehicle 10 with fuel tank module 18 being located within fuel tank 16. Fuel supply line 20 extends from fuel tank module 18 to direct injection pump 26 which is typically located on or near engine 12 located in the front of vehicle 10. Direct injection pump increases the fuel pressure between fuel supply line 20 and fuel injector rail 22. Each fuel injector 24 is in communication with fuel injector rail 22 to receive fuel which is then injected directly into one of the cylinders of engine 12.
Direct fuel injection system 14 does not have a fuel return line from fuel injector rail 22 to fuel tank 16. Because of this, a fuel pump 30 within fuel tank module has its voltage varied to adjust the amount of fuel supplied to direct injection pump 22 which then supplies pressurized fuel to fuel injector rail 22 to maintain a specified fuel pressure within direct fuel injection system 14 as is dictated by the fuel demand from engine 12.
Referring to
Referring now to
Cylinder head 60 defines two pumping cylinders 70. Each piston is disposed within a respective cylinder 70 and reciprocates within its respective cylinder 70 to pump fuel. Cylinder head 60 defines an inlet 72 leading to cylinders 70 and an outlet 74 leading from cylinders 70. An inlet check valve 76 is disposed between inlet 72 and each cylinder 70 and an outlet check valve 78 is disposed between outlet 74 and each cylinder 70 as illustrated in
Lower housing 62 is sealingly attached to cylinder head 60. The pair of cams 66 are rotatably disposed on the engine camshaft 68. Each cam 66 engages an end of a respective piston 64 and each cam 66 has an exterior contour which provides the reciprocal movement of pistons 64 in cylinders 70 when cams 66 are rotated. A return spring or biasing member 82 attached to each piston 64 urges piston 64 into contact with its respective cam 66. Engine camshaft 68 causes rotation of cams 66 and the pumping of fuel by pistons 64 in cylinders 70.
