CN1439076A - built-in fuel pump - Google Patents

Abstract

A fuel pump, which may be disposed within a fuel tank, comprising: a fuel pump housing (1); a pumping mechanism (5) provided in the housing (1) so as to pump the fuel; an electric motor (3) driving a pumping mechanism (5), the motor (3) being mounted in a motor cavity (10) through the housing (1); a fuel inlet of the pumping device; wherein the fuel pump housing (1) includes a breather arrangement (2) which allows air and fuel vapour within the cavity (10) to escape when displaced by fuel entering the motor cavity (10).

Description

built-in fuel pump

The present invention relates generally to fuel pumps for supplying fuel into internal combustion engines, and in particular the present invention relates to fuel pumps suitable for placement within a fuel tank.

There are two main fuel systems commonly used to supply fuel to internal combustion engines in motor vehicles such as automobiles, motorcycles, scooters, boats and aircraft. These fuel systems are carburetor-based fuel systems and injector-based fuel systems. A carburetor-based fuel system provides an air/fuel mixture into the engine's intake manifold, and the carburetor draws fuel from the fuel tank through a fuel conduit that extends into the tank. The fuel tank is usually almost completely emptied by means of the carburetor when the carburetor provides a vacuum within the conduit and when the conduit is positioned with its end adjacent to the bottom of the tank.

Injector-based fuel systems, especially direct injection fuel systems, require fuel pumps to deliver fuel at increased pressure into the fuel injectors. The fuel pump may be driven by an electric motor and may be conveniently located within the fuel tank. In many of these so-called built-in fuel pumps, the electric motor of the pump, especially the commutator and brushes of the electric motor, are arranged to be flooded by the fuel contained in the fuel tank, which helps to prevent A spark is created between the motor's commutator and brushes.

The applicant has invented a fuel injection system for use in small engine applications. An example of a small engine application is a scooter scooter having an engine with a displacement of approximately 50cc to 100cc. In these cases it is preferable to have a relatively inexpensive fuel pump which has a small current draw while providing sufficient pressure for the fuel injection system, especially for direct injection fuel systems which Fuel is required to be delivered at a higher pressure than the intake manifold (intake port) injection system. However, typical inline fuel pumps do not provide this combination of features and typically draw too high a current (on the order of 1.5 A or more), so accessory losses are relatively high for small engine applications employing fuel injection systems. Pumps with smaller power draws, on the other hand, typically deliver fuel at insufficient pressure for the fuel injection system to work efficiently.

One pump that offers these features is fitted with an elongated piston that is reciprocated by a cam and follower arrangement or by a linear slide mechanism. Such a pump is described in the applicant's International Application No. PCT/AU99/00601, the details of which are incorporated herein by reference. However, the described pump is particularly suitable for use as an in-line pump and has a completely sealed electric motor housing. Such a pump cannot be placed in a fuel tank when in use because the electric motor cannot be contained sufficiently so that it cannot be safely flooded with fuel.

Another problem with many existing inboard fuel pumps is that they are constructed in such a way that they do not completely empty the fuel tank and leave residual fuel in the tank. This limits the maximum range of the motor vehicle since it cannot use all the fuel in the tank. For small engine applications (which have smaller capacity fuel tanks), this residual fuel can represent a significant percentage of the fuel tank capacity.

It is therefore an object of the present invention to provide a fuel pump which can be arranged in a fuel tank which overcomes at least one of the problems associated with known fuel pumps.

With this in mind, there is provided a fuel pump that may be disposed within a fuel tank, comprising:

fuel pump housing;

a pumping mechanism disposed within the housing to pump fuel;

an electric motor, which drives the pumping mechanism, the motor is mounted in a motor cavity within the housing;

the fuel inlet of the pumping device;

Wherein the fuel pump housing includes breather means which, when expelled by fuel entering the motor cavity, allow air and fuel vapors within the cavity to escape.

Preferably, the ventilator works as a filter. Preferably, the breather prevents air from flowing out of and into the motor chamber after pump priming.

The provision of the breather means allows the motor cavity to be flooded with fuel when the fuel pump is disposed in the fuel tank and fuel is added to the tank to a level that submerges the motor cavity. Fuel may enter through the pump's fuel inlet and pass or permeate through the pumping mechanism and electric motor, thus forcing air trapped within the pump housing/motor cavity to pass through the breather. Accordingly, it is preferred that when the pump is arranged for use in a fuel tank, the fuel inlet is arranged below the breather. This allows the ventilator to help prime the pump.

The ventilator means may be in the shape of a convoluted ventilating plate or disc. The sintered breather may be positioned above the motor so as to be coextensive with or adjacent to the hole in the fuel pump housing, or it may be positioned on the end cover so that when the fuel pump is positioned in its service orientation, The end cap can be separated from the rest of the housing. The remainder of the housing is preferably sealed, so the ventilator forms the primary mechanism by which air is introduced into the motor chamber and by which air is removed from the motor chamber. The sintered breather may also be of sufficient thickness to act as a flame arrestor to prevent ignition or explosion of the commutator and/or brushes of the electric motor from burning or exploding within the motor cavity or fuel tank. That is, preferably, the breather has sufficient thickness so as to prevent any flames or hot gases generated in the motor cavity from escaping into the fuel tank. Thus, for example, the thickness of the sintered ventilator may be in the range of 2-2.5 mm. Preferably, the ventilator has a mesh of 100 microns (um), and preferably the sintered material is grade 60, and preferably the ventilator has a diameter of approximately 10.5mm and a thickness of approximately 2.5mm. It is envisioned that the ventilator could be formed from other materials. For example, ventilators may be formed from synthetic reverse osmosis materials that facilitate flow preferentially in one direction.

The fuel pump may include a fuel outlet through which fuel pumped by the pumping mechanism exits the pump and enters the fuel supply circuit of the fuel injected internal combustion engine. Fuel from the fuel outlet may pass through a bypass regulator of the fuel supply circuit which typically returns a significant portion of the fuel to the fuel pump. Typically, at least 50% of the fuel is expected to be returned to the fuel pump under normal operating conditions. Under engine idle conditions, the fuel return can be up to about 98%. The returning fuel may flow to a gap (or space) provided above the sinter ventilator, allowing the returning fuel to wet the ventilator. The bushing may support a fuel return line that may allow fuel to flow to the space above the breather. When the level of fuel in the fuel tank drops below the level of the breather, some or all of the fuel from the fuel return passage can pass through the breather and into the motor cavity, thereby falling to the motor or the fuel in the cavity containing the motor on top. This ensures that the motor remains at least partially flooded with fuel even if the fuel level in the fuel tank in the fuel pump drops below the level of the breather in the fuel pump. It also helps to lubricate the motor as the fuel that falls into the rotor diffuses through the moving parts of the motor. In addition, maintaining fuel in the motor cavity helps to maintain the air/fuel ratio in the motor cavity at a level rich enough to extinguish the flame in the cavity, which helps to suppress the possible fire and/or explosion from the motor.

Accordingly, it is preferred that the motor is located midway between the ventilator and the inlet, so that the auxiliary advantage of the motor having fuel flowing through it is also achieved.

The fuel return arrangement described above keeps the sintered ventilator in a wet condition. This results in a special operating advantage: the fuel pump can almost completely empty the fuel tank. This is because, when the level of fuel in the fuel tank is lowered below the level of the breather and the breather is wet, typically under the action of the fuel return line, it is believed that the surface tension effect on the breather can act on the motor fuel pump A partial vacuum is created within the housing causing fuel to be drawn through a vent or channel provided on the fuel inlet side of the inlet valve and into the pump mechanism and into the motor cavity.

Correspondingly, the ventilator has been observed to aid in pump priming as it allows air trapped in the motor cavity to escape. And when the level of fuel in the tank decreases to less than the level of the breather, it is believed that the wetted breather creates a partial vacuum in the motor cavity that assists in the pumping of the fuel. In this sense, the breather can operate to selectively prevent the flow of air through the pump housing.

When the fuel pump of the present invention is used in small engine applications such as scooters, it is preferred that the fuel pump has a small current draw, for example 0.5 amps at 14V, preferably no more than 0.8 amps at 14V amps while providing fuel at sufficient pressure for small engine port injection fuel systems or direct fuel injection systems. Accordingly, it is preferred that the pump supplies fuel at a pressure in excess of 400Kpa (Kilo pascal), more preferably in excess of 600Kpa, for such a magnitude of current consumption. A typical two-fluid direct injection fuel system (also known as a low pressure direct injection fuel system) delivers fuel at a pressure of 750Kpa, and the pump has been observed to deliver fuel at this pressure with a current draw of less than 0.8 amps, and typically around 0.6 ampere. The pump was also observed to deliver fuel at a pressure of approximately 20 bar.

The pumping mechanism may comprise an elongated piston having a length substantially greater than the cross-sectional diameter of the piston. A piston is slidably mounted within the elongated piston passage. When the piston is mounted within the piston passage, the piston defines a variable displacement pump chamber in fluid communication with a fuel inlet and a fuel outlet of the fuel pump. The piston can be actuated to reciprocate by means of a crank pin and slide mechanism or a linkage mechanism. Such a mechanism may include a crank pin supported on and extending from a drive shaft of the motor. The crank pin can engage a sliding mechanism connected to one end of the elongated piston. It is also conceivable that the piston could be driven by a connecting rod supported at one end on the motor drive shaft and at the other end on the piston. Such a drive arrangement is described in the applicant's above-mentioned international application.

The above described drive arrangement of the piston mechanism may be provided in a chamber which is provided in the fuel pump and communicates with the chamber in which the motor is located. A vent line may connect this chamber with the fuel inlet, thereby facilitating the flow of fluid into this chamber and thus into the motor. A partial vacuum is created within the motor cavity and this vent line helps to communicate fuel from the inlet valve area into the motor cavity. In this way, the fuel level in the motor cavity can be greater than the fuel level in the fuel tank. It is believed that the fuel in the motor cavity acts as a secondary fuel source to the valve.

A filter may be provided at the fuel inlet to filter fuel entering the fuel pump from the fuel tank. Preferably the filter has a mesh size of less than 100 um, preferably the filter is of a similar size to any filter employed in the fuel injectors of the fuel system provided by the pump.

Therefore, the fuel pump of the present invention is particularly suitable for use in a fuel tank, where the electric motor is easily flooded with fuel, thereby preventing sparks from being generated between the rectifier and the brushes. Also, if such a spark occurs, the breather unit also acts as a flame arrestor. The fuel pump also has the ability to substantially completely drain the fuel pump, thus helping to maximize the potential driving range of a motor vehicle equipped with such a fuel pump.

According to another aspect of the present invention, a fuel pump of a fuel circuit of an internal combustion engine is provided; The auxiliary channel, in which the motor of the fuel pump is therefore arranged, in use.

In another aspect, this aspect provides a fuel circuit for an internal combustion engine, the fuel circuit comprising a fuel pump and an auxiliary fuel passage; the fuel pump being adapted to fit the auxiliary fuel passage and, in use, the motor of the pump being set in the auxiliary channel.

Preferably said secondary fuel passage is a fuel return circuit which, in use, returns excess fuel to said fuel tank.

Preferably, the pump includes a filter disposed at an intermediate position between the auxiliary channel and the motor. Preferably, the filter is a ventilator, preferably the motor is disposed within the motor cavity and the ventilator prevents the flow of air into the motor cavity, wherein in use the ventilator A partial vacuum is created in the cavity. Preferably said breather provides said resistance in use when wetted by fuel from said secondary channel and preferably provides minimal resistance when dry. Preferably, said resistance is sufficient to create a partial vacuum which allows the fuel to rise from the inlet filter at least into the inlet valve, more preferably it is raised into the motor cavity through a vent line which Connect the area adjacent the inlet valve to the motor cavity. The applicant has found that when the ventilator is dry, the fuel can be lifted by a height of 20-25mm when the pump is operated at a terminal voltage range of 8V to 14V, and, when the ventilator is wet, the terminal voltage For the range of 8V-14V, the fuel can lift the height of 55-65mm. Thus, it was observed that the wet breather increased the height through which the fuel was lifted by 35-40mm when using the breather with a mesh size of 100um.

According to another aspect of the present invention there is provided a fuel pump for an internal combustion engine, said pump comprising a fuel inlet positioned at a lower level than said pump's ventilator; said ventilator providing air flow through said The resistance of the pump thus creates at least a partial vacuum within said pump; said partial vacuum cooperates with said inlet to facilitate the drawing of fuel through said fuel inlet.

Preferably, said ventilator is operatively arranged in communication with a first chamber spaced from the outlet side of said inlet valve; Regional connectivity. Preferably, said first chamber is the housing of a motor of said pump, a vent line providing fluid communication between said housing and said region adjacent the inlet side of said inlet valve.

According to another aspect of the present invention there is provided a fuel circuit for at least a dual-fluid fuel injection system, wherein the fuel provided by the fuel circuit comprises the first said fluid and the propellant fluid comprises the second said fluid, said fuel circuit comprising: a fuel pump adapted to supply fuel under pressure in intermittent pulses; and a pressure regulator which feeds said fuel into a fuel measuring device; said pressure regulator at The pressure difference is the difference between the fuel pressure and the pressure of the second fluid; the pressure difference is smaller than the pressure pulse, so the fuel measuring device can accurately measure the pressure within a predetermined error. Said fuel.

Preferably, the fuel pump is a single chamber pump. Preferably, the pressure difference is less than 1/4 of the pressure pulsation, more preferably, it is less than 1/5 of the pressure pulsation.

Preferably, said second fluid is air supplied at approximately 500 KPa, said fuel is supplied at approximately 750 KPa, said pump has a displacement of 0.041 cc (cubic centimeter) per stroke, and said fuel circuit Fuel is fed into a 50cc engine. Preferably, the pump has a DC motor which draws a current in the range of 600mA to 200mA when the terminal voltage is changed between 14V and 17V. But at 12V, which is also preferred, the pump consumes about 450mA. At 14V, preferably, the DC motor operates at approximately 3900 RPM (revolutions per minute), and at 12V, approximately 3300-3400 RPM. The pump can operate outside of these specified ranges, however, these specified ranges are preferred operating parameters. In particular, it has been observed that a pump of 0.041 cc per stroke typically consumes less than 8.4 watts of electrical power when delivering fuel at 750 Kpa, which translates to between 16 and 30 watts of mechanical power. A typical 50cc engine produces about 3.75KW, so these pumps have accessory losses of less than 1% of the mechanical power produced by the engine.

The invention is described conveniently with reference to the accompanying drawings, which show at least one possible embodiment. Other embodiments of the invention are possible, and therefore the particularity of the drawings and description is not to be construed as superseding the generality of the foregoing description of the invention.

in the accompanying drawings;

Figure 1 is a typical fuel injected small engine motorcycle.

Figures 2a and 2b are schematic diagrams of fuel injected engines and associated fuel supply circuits suitable for use in the scooter of Figure 1 and other small engine applications.

Figure 3 is a perspective view of a fuel pump employed in the fuel circuit of Figures 2a and 2b.

FIG. 4 is a cross-sectional view of the fuel pump of FIG. 3 .

These embodiments are particularly suitable for use as built-in fuel pumps for small internal combustion engine vehicles, such as scooter scooters, which use port injection fuel systems, low pressure direct injection fuel systems, and other direct injection fuel systems of internal combustion engines. Examples of low-pressure dual-fluid direct injection fuel systems for internal combustion engines are described in detail in the applicant's patents US4693224 and US4934329, which are hereby incorporated by reference. Small engine vehicles and other applications typically have a displacement of about 50 cc to 100 cc, and they typically have smaller battery capacities, therefore, are particularly suitable for low current pump motors of about 0.5 amps.

These embodiments also find application in fuel supply circuits that pump fuel from a fuel source, such as a fuel tank, into an internal combustion engine and then return excess fuel to the fuel source.

In order to better understand the environment in which these embodiments are applied, FIG. 1 is now described, which is a schematic diagram of a scooter 300 showing a small engine application of an internal pump. The scooter has front wheels 305 and rear wheels 310 which support the frame and associated plate structure 315 off the road surface 320 . The frame and plate structure 315 includes a rider area 325 that typically has a seat that can support two riders. Rider area 325 is located above rear wheel 310 . The engine and associated drive mechanism 330 are mounted midway between the driver's area 325 and the rear wheel 310 . Steering handle 335 is rotatably mounted to frame and plate structure 315 and also supports shock absorber 340 which sets front wheel 305 to scooter 300 .

In operation, the riders position themselves in the rider's area and place their legs on the footrests 345 provided on the shallow pan floor 350 of the frame and associated plate structure 315 . These footrests 345 are provided on the middle portion between the bottom of the steering handlebar 335 and the driver's area 325 . The handlebar 335 has a mechanical throttle actuation mechanism that can be actuated by the rider rotating their hand. Steering handlebar 335 also has an ignition switch that actuates the electrical circuit between the battery and electrical control components adjacent to the engine and associated drive mechanism 330 and other electrical components such as the fuel pump and headlights 355 .

Scooters have single cylinder fuel injected engines with smaller displacements of about 50cc to 100cc, although increased displacement engines are also available. A fuel tank supporting the built-in pump may be located below the rider area 325 . An inline pump supplies fuel into a fuel supply circuit that communicates with fuel injectors of the engine.

Referring now to Figures 2a and 2b, each schematically illustrates an engine and associated fuel supply circuit suitable for use with the scooter of Figure 1 and other fuel injection applications, particularly small engine applications use.

The engine and associated fuel system of Figure 2a is a direct-injection single-cylinder two-stroke engine 50 having a fuel tank 1 which feeds fuel into fuel injectors 5 via a fuel pump 3 arranged at Inside the fuel tank 1, as described in this specification. The fuel supply circuit also includes a fuel pressure regulator 4 and a fuel supply line 52 and a fuel return line 53 . The fuel injector 6 measures the fuel supplied to the fuel supply injector 7 based on a measurement signal received from an engine control unit (ECU) 11 . The fuel supply injector 7 is in fluid communication with compressed air through an air supply line 70 which receives compressed air from the air compressor 13 . The compressor 13 is driven by a roller follower driven by an eccentric cam 68 which is mounted on or forms part of a flywheel 67 . The fuel supply injector 7 uses compressed air as a propellant to deliver the fuel measured by the fuel injector 5 into the combustion chamber 61 of the engine 50 . Other examples of these fuel systems can be found in the applicant's US Pat.

The fuel supply injector 7 delivers a fuel jet into the combustion chamber 61 in such a manner that the fuel passes through the spark gap of the spark plug 8 . The spark plugs are controlled by the ignition coil 10 which itself is driven by the ECU 11 . Under certain engine operating conditions (these conditions are typically low-to-moderate load and low-to-moderate speed conditions), the engine operates by forming a stratified charge of fuel in the combustion chamber, and the stratified charge is passed through Spark plug 8 to ignite. Preferably, the spark plug ignites the fuel jet as it exits the fuel delivery injector 7, thereby creating a jet directed combustion system.

Airflow is provided into combustion chamber 61 through air box 18 and air filter 19 . Airbox 18 is in fluid communication with intake manifold 65 located between throttle valve 16 and intake reed valve 64 . A combined manifold absolute pressure (MAP) sensor and humidity sensor 20 , often referred to as a TMAP sensor, is disposed in the intake manifold. The TMAP sensor provides a MAP signal to the ECU 11 , which shows the pressure within the intake manifold 65 , and likewise a temperature signal to the ECU 11 , which shows the temperature of the air entering the engine 50 . The TMAP sensor 20 is an analog sensor, and the signal of the sensor can be pulse-modulated by the ECU 11 by using the analog-to-digital conversion technology and the digital pulse modulation filtering technology.

Airflow into the engine is locally controlled by the position of throttle valve 16 . This position is indicated to the ECU 11 via the throttle position sensor 15 .

Oil is supplied to the engine 50 by means of an oil pump 17 which is controlled by the ECU 11 and receives oil from the oil tank 12 .

Electric power is supplied to the engine (including the fuel pump) by means of the battery 22 and ignition switch 21, at least at start-up.

The ECU 11 receives information on the position of the piston 60 in the combustion chamber 61 through the crankshaft position sensor 14 and the code wheel 66 mounted on the flywheel 67 . The encoder wheel 66 includes a number of teeth, typically 24 teeth (one of which can be removed to provide a standard tooth), which pass through the position sensor 14 . These teeth interact with the position sensor 14 to generate a square wave signal that is input into the ECU 11 . The square wave is typically the leading edge of the pulse detected by the ECU 11 , which detects each leading edge of the code wheel 66 as it passes the position sensor 16 .

Information about the position of the piston 60 within the combustion chamber 61 is commonly referred to as the engine crank angle. A two-stroke engine cycle is considered to have a crank angle of 360 degrees, while a four-stroke engine cycle is considered to have a crank angle of 720 degrees. Thus, in operation, the engine crank angle corresponds to the instantaneous position of the engine in the current engine cycle. This position is measured relative to the engine's top dead center (TDC) position, which for a two-stroke engine is the point of maximum compression in any engine cycle, and for a four-stroke engine it is the intake stroke ( That is, the maximum compression point of the compression stroke), which is often called TDC ignition. The 24-tooth encoder provides 15 degrees of crank angle resolution for two-stroke and four-stroke engines.

Figure 2b is a schematic illustration of a single cylinder four-stroke port injection engine 150 similar to the two-stroke engine 50 of Figure 4a. The four-stroke engine 150 has a fuel tank 101 that supplies fuel to the fuel injector 11 through a fuel filter 102 , an inboard fuel pump 103 and a fuel pressure regulator 104 under the control of the ECU 116 . The fuel pressure regulator 174 is integral with the pump 103 , or if not integral with the pump at a location where the pump is installed into the fuel tank 101 . Accordingly, a fuel supply line 172 extends from regulator 174 into fuel injector 172 . A fuel return passage 173 extends from regulator 174 into pump 103 .

Air enters the combustion chamber 161 through the air box 105 and the intake manifold 165, the air box 105 is equipped with an air filter 106, and the intake manifold 165 is equipped with a throttle valve 109, a TMAP sensor 107, a throttle air bypass Through valve 108 and fuel injector 111.

Intake valve 151 is actuated by action of a cam (not shown) to communicate air within the intake manifold with the combustion chamber. Fuel injector 111 injects fuel into the intake manifold, which is then delivered by intake air into combustion chamber 161 , thereby forming a uniform fuel charge within combustion chamber 161 . The spark plug 112 operates under the control of the ignition coil 113 which itself is controlled by the ECU 116 . During the exhaust stroke, exhaust valve 152 is actuated by camming to allow combustion gases to flow from the combustion chamber. The engine temperature sensor 114 indicates the engine temperature to the ECU 116 .

The engine 150 has an engine position sensor 115 and a corresponding encoder wheel showing the instantaneous crank angle of the engine when in operation.

An engine 150 (including a fuel pump 103 ) is powered by a battery 118 and an ignition switch 117 at least during start-up.

Reference is made to Figures 3 and 4 which show details of a preferred embodiment of a fuel pump suitable for placement within a fuel tank such as fuel tank 101 and fuel tank 1 described in detail above. The fuel pump comprises a fuel pump housing 1 in which an electric motor 3 and a pump device 5 are arranged. An intake filter 7 for filtering fuel entering a fuel inlet 9 of the fuel pump is provided on one end of the fuel pump housing 1 . When the fuel pump is arranged in the fuel tank, the filter 7 is arranged on or near the bottom of the fuel tank, and may be arranged in a groove in the bottom of the fuel tank. Fuel entering the fuel inlet 9 through the filter 7 passes through the intake valve assembly 11 . The intake valve assembly 11 is described in detail in the applicant's International Application No. PCT/AU99/00601 and therefore will not be described in any detail here, however, it should be noted that this arrangement does provide a The pump has high efficiency at high pressure. Compared with the small efficiency pump of the same displacement (the displacement is about 0.04cc per stroke), this high pressure facilitates the pump motor to absorb a smaller flow. Another feature of the pump is that it can be arranged to set in smaller fuel quantities at high pressures suitable for small engine fuel injection applications. Compared to a typical fuel pump (in addition to being relatively efficient), the pump has a smaller current draw by displacing a smaller amount of fuel, which is a benefit for small engine applications (where the engine power of a high current fuel pump The attachment loss is more obvious) advantage. The construction of the pump arrangement 5 means that the output of the pump has a pulsating or intermittent character. Here, details of the effect of this intermittent characteristic are provided.

The intake filter 7 may be a woven fabric such as nylon, polyester or other suitable plastic and/or fibers, which are well known in the art, and preferably have a particle size of less than 100 um, although smaller particle sizes may also be used , this smaller particle size is comparable to any mesh used as a filter for a fuel injector that is supplied with fuel by a fuel pump.

Preferably, the intake filter is of the type with an inlet tube extending into the bottom of the filter. The inlet tube has holes adjacent the bottom of the filter so that fuel is drawn from near the bottom of the filter through the inlet valve assembly.

In operation, fuel passes from the inlet valve assembly 11 into the pump chamber 13 of the pumping device 5 . The pumping device 5 comprises an elongated piston 15 arranged in a piston channel 17 which defines a variable volume pump chamber 13 . Piston 15 is driven to and fro by drive means 19 comprising a crank pin 21 supported on drive shaft 6 of electric motor 3 and extending therefrom. The crank pin 21 cooperates at one end of a linkage 23 supported at the other end by the piston 15 . Preferably, the connecting rod, its supporting structure and the engagement mechanism (such as the bore) with the crank pin 21 is constructed of a self-lubricating plastic suitable for high pressure velocity applications, such as polyether ether ketone (PEEK), as described in the Society of Automotive As described in Engineers (SAE) paper 970244 "Lubriacted Thermoplastic Composites for High P-V Application" WilliamsE.H. Other materials such as PPS(OBG) and PPA(BQU) may form suitable replacements and are also described in SAE970244 Williams, E.H.

The drive device 19 is supported in a chamber 25 which is arranged below the electric motor 3 and opens into the electric motor 3 . An internal ventilation line 27 communicates this chamber 25 with the fuel inlet 9 at a point on the inlet side of the fuel inlet valve assembly 11 . Preferably, the vent line 27 is adjacent to the inlet side of the fuel inlet valve assembly 11 so that the fuel inlet valve assembly 11 can draw fuel from the chamber 25 or supply excess fuel from the chamber 25 through the vent line 27 .

Fuel pumped from the pumping chamber 13 passes through the fuel outlet valve 29 and through the fuel output channel 31 to the fuel outlet 33 of the fuel pump. In these embodiments, the height of the fuel inlet is less than the height of the fuel outlet. This is an advantage in some built-in applications, although not believed to be necessary for the embodiments to work. Pressure relief valve 50 communicates fuel from outlet passage 31 into chamber 25 when the pressure within outlet passage 31 exceeds a predetermined minimum value. Pressure relief valve 50 operates according to principles well known in the art and therefore will not be described further.

The electric motor 3 is supported in the motor chamber 10 of the fuel pump housing 1 . The cavity 10 is closed at the top by an end cap 12 . The sinter vent 2 is supported within the end cap 12 . The sinter vent 2 is arranged adjacent to the hole 8 which passes through the end cap 12 . The breather allows air to flow from the motor cavity to a location outside the pump.

When the fuel pump is disposed within the fuel tank, the fuel pump is generally submerged in the fuel. In these cases fuel can pass through the fuel inlet 9 , through the internal ventilation line 27 to the chamber 25 and thus through the motor chamber 10 . Fuel passes or percolates through the electric motor 3 and any air or fuel vapors within the motor chamber 10 exits the fuel pump through the sintered breather 2 and holes 8 . This allows the fuel to rise within the motor cavity 10 to the level of fuel in the tank, which itself allows the motor 3 to be submerged when the pump is submerged or at least partially submerged by the fuel in the tank. Flooding the motor with fuel helps prevent sparks between the electric motor commutator and brushes (not shown).

Flooding the motor and the motor chamber means that, in operation, fuel is sucked from the filter 7 and the motor chamber 10 through the ventilation line 27 , through the inlet 9 and the transducing chamber 13 . However, it is believed that the main suction work is through the inlet filter 7 .

During operation of certain fuel circuits, a substantial portion of the fuel pumped by the fuel pump is returned to the fuel source, such as a fuel tank. Typically, at least 50% of the fuel is returned during engine operation and up to 98% at idle. According to one embodiment, fuel delivered from the fuel pump into the fuel circuit passes through a bypassed regulator (not shown) which ensures that fuel (which the fuel circuit does not deliver to the engine) returns to the fuel circuit via the return line. source.

In a preferred embodiment, the return line is connected to the fuel return bushing of the fuel pump. This allows return fuel to enter the space 37 above the sinter ventilator 2 . This ensures that the ventilator 2 is kept wet by the fuel when the amount of fuel in the fuel tank in which the pump is installed falls below the height of the sintered ventilator 2 .

It has been found that if the sintered breather 2 is wet and the fuel level in the fuel tank is reduced to less than the level of the sintered breather, the resulting surface tension action in the breather creates a partial vacuum in the fuel pump housing 1 . This results in fuel being drawn into the cavity 25 through the fuel inlet 9 through the vent line 27 which has been observed to keep the fuel in the motor cavity 25 at a higher level than the fuel level in the fuel tank. It is believed that this increase in negative discharge pressure assists the fuel pump to continue pumping fuel even when the fuel level decreases below the level of the inlet valve 11 . In practice, it has been found that the fuel pump will continue pumping until the fuel level has dropped close to the bottom of the sensitive element 41 of the filter 7 . Therefore, the fuel pump of the present invention can almost completely empty the fuel tank. On the other hand, it is believed that ventilators that provide resistance to air flow also provide this partial vacuum. This partial vacuum is achieved due to the provision of a pump housing which is sealed from the ventilator and inlet 9 .

It is also believed that some, if not all, of the fuel returning along the fuel return passage may pass through the breather and into the motor in the motor cavity. This helps keep the motor wet with fuel. It is believed that the fuel acts as a lubricant for the motor and it is therefore believed that a fuel return passage through the motor is particularly advantageous where the level of fuel in the fuel tank is such that the motor is no longer flooded.

Another advantage of the return passage through the motor cavity is that the extra fuel in the motor cavity helps to reduce the air/fuel ratio in cavity 10 to less than the stoichiometric ratio which helps suppress the any flame.

In this regard, it is believed that by using a ventilator thick enough to suppress any flames that may develop within the motor compartment, thereby preventing the flames from entering the fuel tank normally, and preventing an explosion from occurring, and thereby preventing the hot gases from re-igniting once they pass through the ventilator. The breather may be formed from sintered metal. A thickness between 2mm-2.5mm is believed to be effective, but 2.3mm has been found to be sufficient for fuel pumps for small engine applications. A ventilator has been found to be particularly effective: its diameter is close to 10.5mm, its thickness is close to 2.5mm, and the ventilator is formed from a grade 60 sintered material, thus having a mesh of approximately 100um, but is believed to have a mesh in the 80um to 120um range. The ventilator inside the mesh is also effective. It is also believed that other materials that provide resistance to air flow also provide effective alternatives to the sintered vent material described in detail. For example, a metal braid or alternative forms of flame arrestors are also suitable.

Alternative embodiments may not have a fuel return circuit, or may not provide a fuel return passage adjacent to the bore into the cavity in which the motor is mounted. In these embodiments, additional fuel passages such as a main supply line or a branch line from the return line can be designed that feed fuel into the ventilator to keep the ventilator wet, or to keep the fuel flowing over the motor .

It is often not necessary to provide a breather in the fuel circuit which returns fuel through the inboard motor, but in some applications it is preferred that such a circuit have such a breather or filter. On the other hand, satisfactory operation is believed to be obtained from a pump with a ventilator and a fuel return line that bypasses the ventilator.

As described in detail above, the inboard fuel pump mechanism of Figures 4a and 4b is a single chamber arrangement which provides improved fuel efficiency at high pressures and smaller flow rates compared to standard fuel pumps (which are approximately 15% efficient) Higher efficiency (about 30%). This allows the pump to draw less than 800mA, typically 500mA when used in small engine applications such as scooters.

In achieving this small current draw, the pump has an intermittent output, which can be seen as fuel pressure pulses in the fuel supply circuit. In the dual fluid fuel injection systems described above, fuel is typically metered through a fuel injector to a pneumatic delivery injector, which is typically used in port injection systems. In order to accurately meter fuel, a fuel injector needs to experience a relatively constant fuel pressure at its fuel inlet.

In a two-fluid system, the fuel pressure experienced at the fuel injector inlet is generally set relative to the pressure of the second fluid, typically compressed air. Typically, the delivery injector is in continuous communication with a pressurized source of the second fluid. Accordingly, the fuel supply circuit typically has a higher pressure than the second fluid so it can be measured against the pressure of the second fluid into the delivery injector. A differential pressure control regulator is typically used to obtain this differential pressure between the fuel supply pressure and the second fluid pressure.

The fuel supply circuit is subjected to pressure pulses resulting from the use of, for example, a chamber to reciprocate the fuel pump mechanism, preferably the differential between the fuel supply pressure and the pressure of the second fluid exceeds the magnitude of the pressure pulse by such an amount , so as to experience a generally constant pressure at the inlet to the fuel injector that measures the fuel entering the fuel delivery injector. This generally constant pressure should be sufficient to measure fuel entering the fuel delivery injector within a predetermined measurement error.

For example, in the 50cc scooter engine of Fig. 2a, it was found sufficient that the pump of the above embodiment had a plunger of 4mm diameter, at a pressure difference of 250Kpa between the fuel pressure and the compressed air, The plunger delivers 0.041cc per stroke. For this, the fuel pressure is close to 750Kpa and the pressure of the compressed air is close to 500Kpa. The pump is powered by a DC motor with a frequency of 3900 strokes per minute at 14V across the terminals and typically between 3300 and 3400 strokes per minute at 12V. Accordingly, it is expected that a typical pump in production will draw less than about 11.2 Watts (i.e., less than 0.8 A at 14 V), which typically has 20 to 30 Amps depending on the efficiency of the alternator or magneto driving the pump's electric motor. Mechanical work between watts. A typical 50cc engine produces approximately 3.75KW of power, correspondingly a typical production pump may have less than 1% engine parasitic mechanical power.

The diameter of the plunger may be greater than 4mm. For various pumps delivering fuel at 750Kpa with 14V across the motor terminals, the following details have been observed: Plunger diameter (mm) Flow Rate(L/h) Current Consumption (mA) 4.0 9.4 500 5.0 13.1 680 6.0 16.4 870

It has also been found that a typical pump with a 4 mm plunger can generate up to 20 Bar pressure in the fuel line.

It was also observed that the pump (the pump had a 4mm plunger and a ventilator with a diameter of approximately 10.5mm, a thickness of approximately 2.5mm, and a mesh of approximately 100um) passed through a dry ventilator, a 20 to 25mm negative The suction lift and terminal voltage are in the range of 8-14V to boost the fuel. It was also observed that with a wet ventilator, as provided by placing the ventilator in the fuel return channel, the negative suction lift range increased to 55-65mm for the same terminal voltage. This increased negative suction lift is believed to occur when the breather is wet and when the level of fuel in the fuel tank is less than the level of the breather, with the result that a partial vacuum is created in the motor cavity by surface tension. It is also believed that this increased negative suction draws fuel along the vent line 27 and delivers fuel into the motor cavity, causing the fuel level in the motor cavity to often exceed the fuel level in the fuel tank. It is believed that this negative suction lift allows the pump to almost completely empty the fuel tank (ie allows the pump to draw fuel from below the level of the inlet valve assembly 11).

These embodiments provide a fuel pump that may be positioned within a fuel tank and submerged in fuel. For direct injection fuel systems, the fuel pump provides fuel at a sufficient pressure and with a sufficiently small power consumption that it can be used in small engine applications.

Variations and improvements of the invention and the embodiments described herein are within the scope of the appended claims.

Claims (41)

1. A fuel pump, which can be arranged in a fuel tank, comprising: fuel pump housing; a pumping mechanism disposed within the housing to pump fuel; an electric motor, which drives the pumping mechanism, with the motor mounted in the motor cavity through the housing; the fuel inlet of the pumping device; Wherein the fuel pump housing includes breather means which, when expelled by fuel entering the motor cavity, allow air and fuel vapors within the cavity to escape. 2. The fuel pump of claim 1, wherein the breather is also adapted to operate as a filter. 3. A fuel pump as claimed in claim 1 or 2, characterized in that the breather prevents the flow of air out of and into the motor chamber after pump priming. 4. A fuel pump as claimed in any one of claims 1 to 3, wherein when the pump is arranged for use in a fuel tank, the fuel inlet is arranged below the breather, whereby the breather assists in priming the pump. 5. A fuel pump as claimed in any preceding claim, wherein the breather means is in the form of a wound breather plate or disc. 6. A fuel pump as claimed in claim 5 wherein the sintered breather is positioned above the motor adjacent to an aperture in the fuel pump housing or on the end cap so that when the fuel pump is in its Positionally, the end cap is separated from the rest of the housing. 7. A fuel pump as claimed in claim 5 or 6, wherein the sintered breather is of sufficient thickness to function as a flame arrestor for the electric motor. 8. A fuel pump as claimed in any one of claims 5 to 7, characterized in that the sintered breather is dry during pump start-up so that collected air can come out of the pump and remain wet during pump operation state, thereby helping to provide a partial vacuum. 9. A fuel pump as claimed in any one of claims 1-4, characterized in that the breather means is in the form of a plate or disc formed of a synthetic reverse osmosis material which facilitates the flow of air, preferably in one direction. flow. 10. A fuel pump as claimed in any one of the preceding claims, wherein the pump includes a fuel outlet through which fuel pumped by the pumping mechanism exits, wherein fuel from the fuel outlet passes through a bypass regulator, Thus returning a significant portion of the fuel to the fuel pump. 11. The fuel pump of claim 10, wherein at least 50% of the fuel is returned to the fuel pump under normal operating conditions and up to about 98% of the fuel is returned under engine idling conditions. 12. A fuel pump as claimed in claim 10 or 11, characterized in that the returned fuel flows to a space arranged above the breather means, whereby when the fuel level is lowered below the height of the breather means, the motor remains at least partially flooded with fuel. 13. A fuel pump as claimed in claim 12, wherein the motor is positioned intermediate the breather means and the inlet opening to facilitate fuel flow through the motor during pump operation. 14. A fuel pump according to any one of the preceding claims, wherein the pumping mechanism comprises an elongated piston having a length substantially greater than the cross-sectional diameter of the piston, the piston being slidably mounted in the elongated piston passage Inside, thereby defining a variable displacement pump chamber, the pump chamber is in fluid communication with the fuel inlet and fuel outlet of the fuel pump. 15. The fuel pump of claim 14, wherein: The piston is actuated to reciprocate by means of a drive comprising a crank pin supported on and extending from a drive shaft of the motor and a sliding mechanism comprising a crank pin The pin engages a sliding mechanism connected to one end of the elongated piston. 16. The fuel pump of claim 14, wherein the piston is drivable to reciprocate by drive means comprising a cam supported on the motor drive shaft and abutting the cam follower, Instead, the follower is arranged on said end of the piston. 17. A fuel pump as claimed in claim 15 or 16, characterized in that the drive means are arranged in a chamber which is arranged in the pump below the motor. 18. A fuel pump as claimed in claim 17, wherein a vent line connects the chamber with the fuel inlet to facilitate the flow of fluid into the chamber and thus into the motor. 19. A fuel pump for a fuel circuit of an internal combustion engine, the fuel pump is suitable for being arranged in a fuel tank, the fuel circuit has an auxiliary fuel passage, and the fuel pump is also suitable for installing the auxiliary passage, so that when in use, A motor of the fuel pump is disposed in the auxiliary passage. 20. A fuel pump as claimed in claim 19 wherein said auxiliary fuel passage is a fuel return circuit which, in use, returns excess fuel to said fuel tank. 21. The fuel pump according to claim 19 or 20, wherein the pump includes a filter disposed at an intermediate position between the auxiliary passage and the motor. 22. The fuel pump of claim 21, wherein the filter is a breather, the motor is disposed in a motor cavity, the breather prevents air from flowing into the motor cavity, and in use , the ventilator creates a partial vacuum in the motor cavity. 23. A fuel pump as claimed in claim 22 wherein said breather, in use, provides said resistance when wetted by fuel from said secondary passage, and said breather when dry, Ventilators provide minimal resistance. 24. The fuel pump of claim 23, wherein the resistance is sufficient to create a partial vacuum that allows fuel to rise from the inlet filter into the inlet valve. 25. The fuel pump of claim 24, wherein the partial vacuum lifts the fuel to a height of about 30mm. 26. A fuel circuit for an internal combustion engine, the fuel circuit comprising a fuel pump and an auxiliary fuel passage; said fuel pump being adapted to fit said auxiliary fuel passage, and in use, said pump motor being disposed within said auxiliary passage . 27. A fuel pump for an internal combustion engine, said pump comprising a fuel inlet positioned at a lower level than said pump's ventilator; said ventilator providing resistance to air flow through said pump and thus in said At least a partial vacuum is created within the pump; the partial vacuum cooperates with the inlet to facilitate drawing fuel through the fuel inlet. 28. A fuel circuit for at least a dual fluid fuel injection system, wherein said fuel circuit provides fuel comprising a first said fluid and a propellant fluid comprising a second said fluid, said fuel circuit Comprising: a fuel pump adapted to deliver fuel under pressure in intermittent pulses; and a pressure regulator which supplies said fuel to a fuel measuring device; said pressure regulator operates under pressure differential, the The differential pressure is the difference between the pressure of the fuel and the pressure of the second fluid; the differential pressure is greater than the pressure pulse so that the fuel measuring device can accurately measure the fuel within a predetermined error. 29. The fuel circuit of claim 28, wherein the fuel pump is a single chamber pump. 30. A fuel circuit as claimed in claim 28 or 29, characterized in that said pressure pulse is less than 1/4 of said differential pressure, preferably it is less than 1/5 of said differential pressure. 31. The fuel circuit according to any one of claims 28-30, wherein the second fluid is air, the air is supplied at about 500KPa, the fuel is supplied at 750KPa, and the pump has 0.041cc displacement, and the fuel circuit feeds fuel into a 50cc engine. 32. A fuel circuit as claimed in claim 31, characterized in that the pump has a DC motor which draws a current in the range of 600mA to 200mA when the terminal voltage is changed between 14V and 17V. 33. The fuel circuit of claim 32 wherein the pump consumes approximately 450mA at 12V. 34. A fuel circuit as claimed in claim 32 or 33 wherein the DC motor operates at about 3900 RPM at 14V and approximately 3300-3400 RPM at 12V. 35. A scooter having an internal combustion engine having at least one fuel injector that receives fuel from a fuel supply circuit that includes a fuel pump disposed within a fuel tank that generates Accessory losses of less than 1% of the mechanical power produced by the engine are achieved. 36. The scooter of claim 35, wherein said fuel injector is a direct injection fuel injector which accepts fuel at a pressure in excess of 600 KPa. 37. A scooter as claimed in any one of claims 35 or 36 wherein said engine has a displacement of about 100 cc or less. 38. A scooter with a fuel pump as claimed in any one of claims 35-37, wherein said pump has a pumping mechanism, wherein said pump is arranged to generate Negative suction lift of at least 55 mm, while the pumping device has a piston with a diameter of approximately 4 mm. 39. The scooter of claim 38, wherein said negative suction lift is created at least when the fuel in the fuel tank is lowered to a level less than that of a ventilator, wherein said ventilator is provided by a fuel return passage Keep the container wet. 40. The scooter according to any one of claims 35-39, wherein the fuel pump further comprises a pumping mechanism, the pumping mechanism sucks fuel through the fuel inlet valve and discharges fuel through the fuel outlet valve, the fuel pumping The mechanism is driven by an electric motor disposed in a motor cavity having a breather arrangement to draw fuel into the motor cavity from a fuel tank or a fuel return line. 41. The scooter of claim 40, wherein said motor cavity is in fluid communication with a location immediately adjacent the inlet side of said inlet valve.

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