CROSS REFERENCE TO RELATED APPLICATION(S)

The present application claims priority to German Patent Application No. 10-2020-206494.6 filed on May 25, 2020, the entire contents of which is incorporated herein for all purposes by this reference.

TECHNICAL FIELD

The present disclosure relates to a fuel pump for a liquid fuel water injection system of a motor vehicle, and more particularly, to a fuel pump for a gasoline water direct injection system of a motor vehicle. disclosure

BACKGROUND

In order to fulfill customer demands on passenger vehicles and to meet future CO2 emission as well as exhaust gas emission regulation targets, modern high-efficient gasoline combustion engines often rely on gasoline direct injection (GDI). This technology enables substantial benefits especially for engines with high specific power output and compliant with the newer exhaust gas regulations. GDI generally offers the possibility to reduce the number of assembled components as well as the overall weight.

The fuel supply architecture of modern GDI engines usually delivers gasoline from a fuel tank at low pressure of around 3 to 6 bar by a continuously driven supply pump. The gasoline is then passed to a high-pressure pump configured to pressurize the gasoline to a pressure of roughly 50 to 500 bar and pump the gasoline into an injection rail and from there further to the fuel injectors. The gasoline pressure is regulated by the engine control unit (ECU) of the vehicle via the pumps.

The high-pressure pump is typically mounted and fixed onto the assembly of the respective internal combustion engine (due to the high forces of ˜3500 N and higher a very rigid connection is required) and mechanically driven by a camshaft of the engine. Thus, pump frequency and/or pump rate of the high-pressure pump are coupled to the engine speed of the internal combustion engine. Furthermore, typical pump systems have a high energy demand and need to be matched to the fuel demands of the respective engine. Due to the fixed connection of the high-pressure pump, the pump's displacement needs to be matched to the highest injection quantity per stroke of the engine. As a result, typical systems may not reach the highest possible efficiencies and different types of vehicles may require different pump configurations, implying that various different pumps may be needed to fulfill consumer needs.

To stabilize pressure along an injection rail and to avoid high energy consumption, modern high pressure pumps usually employ a digital inlet valve (DIV), which regulates the amount of pressurized fuel that is transferred from low pressure to high pressure in a given time interval. DIV mostly utilize a valve that is electromagnetically actuated and emits sound at a high frequency of roughly 5 to 10 kHz. This generates mechanic noise known as “ticking”, which may be perceived as uncomfortable by end-users preferring a smooth driving experience (e.g., in particular due to the mounting position of the system on top of the engine assembly). To reduce these sound emissions, current solutions often rely on significant sound insulation around the high-pressure pump potentially leading to additional costs, weight and lowered performance due to fuel heat up. In addition, since pump systems usually are matched to engine fuel demands, high variety by possible system combinations may increase costs for the manufacturer.

Water injection into internal combustion engines has been known as a powerful tool to increase maximum power and/or decrease emissions. By injecting water, combustion temperatures may be cooled down to protect vehicle components like turbo charger and after treatment systems in situations with high engine demand. Direct injection of water into the combustion chamber, so-called Gasoline Water Direct Injection (GWDI), is often realized through the use of an emulsion with a variable water-fuel ratio. Since water and fuel need to be mixed with a high precision, in particular under highly dynamic engine conditions, and to ensure sufficient supply even at highest power and speed ranges, size and complexity of conventional injection systems may increase significantly. Moreover, the fuel water emulsion may decompose into its original components, in particular during inactive periods of engine operation. This effect may compromise stability of the emulsion, which then may adversely affect engine performance at a later point in time. Moreover, the two separated fluids may reside within engine parts such as rails and pipes, which may influence durability of the entire system.

SUMMARY

Hence, there is a need to find solutions for liquid fuel water injection systems with reduced costs, increased effectiveness and durability as well as reduced sound emissions. Accordingly, the present disclosure provides a fuel pump for a liquid fuel water injection system of a motor vehicle.

According to one aspect of the disclosure, a fuel pump for a liquid fuel water injection system, in particular a gasoline water direct injection system, of a motor vehicle may include a low-pressure pump configured to mix water from a water tank of the motor vehicle with liquid fuel from a fuel tank of the motor vehicle to a liquid fuel water emulsion and provide the liquid fuel water emulsion at a low pressure; a high-pressure pump in fluid communication with the low-pressure pump and configured to compress the liquid fuel water emulsion from the low pressure to a high pressure for injecting the liquid fuel water emulsion into an internal combustion engine of the motor vehicle via an injection rail of the motor vehicle; and a pump drive configured to drive the low-pressure pump and the high-pressure pump synchronously with a pump frequency independently from an engine speed of the internal combustion engine of the motor vehicle.

According to another aspect of the disclosure, a motor vehicle has an internal combustion engine and a liquid fuel water injection system configured to inject liquid fuel into the internal combustion engine via an injection rail. The liquid fuel water injection system has a fuel pump according to the disclosure.

According to yet another aspect of the disclosure, a method for operating a fuel pump according to the disclosure may include mixing water from the water tank of the motor vehicle with liquid fuel from the fuel tank of the motor vehicle to a liquid fuel water emulsion; pumping the liquid fuel water emulsion with the low-pressure pump at the low pressure; and compressing the liquid fuel water emulsion from the low pressure to the high pressure with the high-pressure pump for injecting the liquid fuel water emulsion into the internal combustion engine of the motor vehicle via the injection rail of the motor vehicle. The low-pressure pump and the high-pressure pump may be driven synchronously by the pump drive with a pump frequency independently from an engine speed of the internal combustion engine of the motor vehicle.

The present disclosure decouples the pumps from the internal combustion engine and instead drives the low-pressure and the high-pressure pump together with a dedicated pump drive, e.g. an electric machine. Accordingly, the same pump configuration may be used for various different engines and vehicle types, resulting in a reduction of total costs and a simplification of the vehicle supply infrastructure. In addition, the pump system no longer needs to be mounted on top of the internal combustion engine and hence sound emissions, in particular those of the DIV, may be reduced or completely avoided. In fact, the pump system may be installed anywhere in the vehicle, e.g. in an underfloor or in an isolated box within the engine cabinet spaced apart from the actual engine. Moreover, the DIV of the pump system may be eliminated entirely. By utilizing one common drive for both pump systems, power consumption may be reduced significantly by optimized state of operation.

According to the disclosure, the pump drive may be configured to drive the pumps with a pump frequency independently from an engine speed of the internal combustion engine of the motor vehicle. Due to the presence of a dedicated pump drive, the pumps no longer need to be mechanically driven by a camshaft of the engine. Hence, the pump frequency does not need to be coupled to the engine speed anymore. Accordingly, the pump configuration and behavior may be tuned in an optimized way for each type of vehicle, type of engine and driving situation with one single type of pump. The resulting system may thus be optimized to provide the highest possible efficiency or other features such as start ability and independent rail pressure for each case without having to compromise due to an interconnection with the engine.

Additionally, the present disclosure may simplify the mixing process of water and liquid fuel by introducing a single low-pressure pump receiving both water and fuel directly from the respective supply tanks, mixing them and pressurizing them to a low pressure, e.g. 3 to 6 bar. The low-pressure pump is thus able to function as a soak (e.g., suction) pump that receives water and fuel without the requirement of any dedicated supply pumps for each of these substances. For example, both mixing components may be provided within their respective tanks at pressure below 1 bar. Accordingly, cost and power consumption of the pump system may further be reduced. The emulsion components may be mixed directly within the low-pressure pump. As the pump system is driven independently of the engine speed, the total volume flow of the mixed fluid may be adjusted in an optimal way according to the current need of the driving situation. Even high-volume flows required for sport engines, e.g. 130 l/h and more, may be provided. For example, a side channel pump capable of soaking gas media may be employed as low-pressure pump, which would allow direct mixing via an internal swirl movement of the medium.

It is to be understood that the fuel pump of the disclosure may also be operated in a mode where only liquid fuel is pumped into the internal combustion engine from the fuel tank without any admixture of water. In fact, during normal engine operation water injection is often not required. Water injection is particularly relevant in dynamic driving situations and for high engine loads. Hence, the amount of water in the liquid fuel water emulsion may be set to minimal values or even zero by the fuel pump in certain driving situations, e.g. by closing the connection to the water tank by a valve. Accordingly, the present system is able to selectively admix water to the liquid fuel stream based on the driving situation and/or engine condition. It is thus to be understood in the following that the system may also transport liquid fuel instead of a liquid fuel water emulsion and inject it into the engine.

The solution of the disclosure may be particularly employed for GDI systems. However, the disclosure is also applicable to other fuel injection systems based on liquid and/or liquefied fuels comprising but not limited to liquefied natural gas (LNG), compressed natural gas (CNG), liquefied petroleum gas (LPG), hydrogen and so on.

According to an exemplary embodiment of the disclosure, the fuel pump may further include a throttle valve configured to adjust an amount of water provided from the water tank to be mixed with the liquid fuel to the liquid fuel water emulsion within the low-pressure pump. Additionally, or alternatively, also the liquid fuel amount from the fuel tank may be adjusted via a throttle valve. Accordingly, mixing levels may be controlled during the pre-mixing in a simplified and yet precise way by adjusting inlet flow ratios via the throttle valve. This also means that the emulsion mixture may be adjusted at any point in time dynamically.

According to an exemplary embodiment of the disclosure, the pump drive may be configured as an electric motor. It is to be understood however that the pump drive may be another power source driven independently of the engine speed of the internal combustion engine. For example, the pump drive may be a pneumatic motor, a hydraulic motor and so on.

According to an exemplary embodiment of the disclosure, the pump drive may include at least two electric submachines axially coupled to each other between the low-pressure pump and the high-pressure pump. For example, two brushless direct current (DC) motors may be used to generate a sufficient power output, e.g. 500 W or more, and an additional boost functionality to manage high engine gradients, e.g. to boost the power output from 500 W up to 1000 W on very short time scales. As a result, flexibility for high pressure and/or flow gradients may be realized. Moreover, a stable injection rail pressure may be secured over the full dynamic range of the engine/vehicle. In other exemplary embodiments, even three, four or more electric submachines may be coupled to each other to further increase flexibility of the system.

According to an exemplary embodiment of the disclosure, each electric submachine may include a helical cooling channel configured to flush the liquid fuel water emulsion from a low-pressure side to a high-pressure side along a helical path around an axial direction of the respective electric submachine. Accordingly, the liquid fuel water emulsion (or, alternatively, only fuel) may be used to cool down the pump drive, which inevitably generates a certain amount of heat. As the electric submachines are mounted between the low-pressure pump and the high-pressure pump, the liquid may be used for this purpose travelling between the low-pressure side and the high-pressure side. For example, the liquid may be guided through an outer hull of the electric submachines.

As an additional benefit, the liquid fuel water emulsion may be maintained under constant movement as it tumbles along the helical cooling channels. This means that the homogeneity of the mixture may be stabilized merely by flushing the liquid fuel water emulsion through the cooling channels. It will be clear to the person of ordinary skill in the art that a similar cooling mechanism may also be employed in case that the pump drive is not split up into two or more submachines. In particular, the pump drive may still be mounted between the low-pressure pump and the high-pressure pump and may carry one or several helical cooling channels, e.g. along an outer side or hull, from the low-pressure side to the high-pressure side.

Additionally, according to an exemplary embodiment of the disclosure, each helical cooling channel may be integrated into an outer hull of the respective electric submachine. Accordingly, a cooling flow along the complete outer side or surface of the electric submachines may be accomplished for optimized cooling of the pump drive. The fuel pump may further include a hydraulic regulator configured to provide a pressure regulated connection between the electric submachines for conducting the liquid fuel water emulsion between the electric submachines.

The hydraulic regulator may be configured to adjust the internal flow of the liquid and maintain internal pressure of the liquid flow. The internal pressure regulation system may help to properly fill the fuel pump with the liquid and to cool the pump drive. The hydraulic regulator may include an overflow return valve for pressure regulating a backflow of liquid from the high-pressure side to the low-pressure side.

Since the low-pressure pump typically requires a higher displacement of ˜10-20% than the high-pressure pump, any surplus liquid may be flushed back to the low-pressure side. The hydraulic regulator thus may provide a regulation line besides a main supply line. This may become necessary in certain applications for three reasons. First, the fuel pump may need to uphold a certain relative pressure. Second, first soaking may require recirculation to evacuate the system. Third, any liquid remaining after the engine is shut off may heat up, which could increase an internal pressure as well as a vapor content. An increasing pressure could be released through this valve.

The regulation may provide additional advantages over conventional systems. The usually utilized pressure membranes are not required anymore. And furthermore, such a pressure stabilization may allow to use various liquefied fuels like LNG, LPG, CNG etc. The overflow return valve may, for example, be configured as a naturally closed poppet valve or the like, which opens at a predefined pressure level, e.g. 5 bar. Alternatively, the overflow return valve may however also be actuated electrically, for example.

According to an exemplary embodiment of the disclosure, the overflow return valve may be configured to deliver the backflow of liquid to the low-pressure fuel pump for mixing of the liquid fuel water emulsion. For example, liquid fuel may be flushed back to an inlet of the low-pressure pump. Similarly, a surplus of liquid fuel water emulsion may be flushed back to the inlet of the low-pressure pump.

According to an exemplary embodiment of the disclosure, the fuel pump may further include an emulsion separation device configured to separate water and liquid fuel from the liquid fuel water emulsion. The overflow return valve may be configured to deliver the backflow of liquid to the emulsion separation device. For example, a surplus of liquid fuel water emulsion may be conducted to the separation device where it is then separated back into the liquid fuel component and the water component. Both components of the emulsion may then be transported separately either back into their respective supply tanks or directly to an inlet of the low-pressure pump for instant usage.

Additionally, according to an exemplary embodiment of the disclosure, the hydraulic regulator may include an injection rail relief configured to receive liquid from the injection rail back into the hydraulic regulator. Correspondingly, the injection rail may include a pressure relief valve configured to purge liquid from the injection rail to the fuel pump. The method may thus particularly include purging the liquid fuel water emulsion from the injection rail by the pressure relief valve. Moreover, the method may include separating the purged liquid fuel water emulsion into water and liquid fuel by an emulsion separation device.

The present pump system thus also functions as a purging system for purging the emulsion or the particular components, e.g. fuel. This is possible in the present system mainly because the whole supply system of low- and high-pressure pumps is able to run independently of the engine. Thus, recirculation of any liquid in the injection system is possible, in particular surplus fluid in the injection rail and the connection pipes. Accordingly, any fluid remaining in the injection system may be reused, that is, remixed during operation and, in particular, during engine start (e.g. start/stop). Moreover, draining of the liquids within the injection system is possible after engine shut off to avoid fuel aging which further increases the durability of the system.

Liquid may thus be constantly mixed and drained during operation, which means that stability of the emulsion may be preserved. For example, the lower density media phase of the emulsion may be drained from the injection system, e.g. gasoline in case of a gasoline-water mixture (in case that the emulsion separates/dissolves into the individual substances, which will happen according to the density of the respective substance).

The injection rail relief may be provided as a naturally closed poppet valve or the like. However, alternatively, an electrically actuated mechanism may be used as well. For example, the pressure relief valve may be operated and actuated by the engine control unit (ECU) to permanently (partially) open as long as the pressure in the injection rail is greater than a predefined pressure threshold, e.g. about 2 bar. Alternatively, the pressure relief valve may open completely to release the liquid abruptly above a certain pressure threshold.

According to an exemplary embodiment of the disclosure, the high-pressure pump may include a suction piston for compressing the liquid fuel water emulsion conducted from the low-pressure pump to the high-pressure pump and a crank drive driven by the pump drive and configured to drive the suction piston. In the present case, a crank drive actuated by the pump drive may replace the typically employed camshaft driven by the internal combustion engine. The suction piston (or plunger) may be configured in an optimized way to provide a convenient lift range (e.g., lift range for low mass per lift, however high enough to compress and deliver enough liquid). The solution may employ one common shaft for synchronous liquid flow via the low-pressure pump to the high-pressure pump.

According to an exemplary embodiment of the disclosure, the fuel pump may be configured to operate in a pump frequency range between 0 rpm and about 16.000 rpm with a flow rate between 0 kg/h and about 100 kg/h. The pressure at the injection rail may be stabilized and adjusted precisely in case the liquid is delivered in such small hubs over such a large frequency range. Additionally, the low pressure may be in a range between 1 bar and about 10 bar and/or the high pressure may be in a range between about 50 bar and 500 bar. For example, the low pressure may be between roughly about 3 bar and 6 bar. The high pressure on the other hand may be between about 250 bar and 350 bar, for example.

According to an exemplary embodiment of the disclosure, the pump drive may be a brushless DC motor. The electric motor may provide enough power and torque required by the present solution. The electric motor may have a maximum power output of at least 500 W at an operating voltage of 48 V. The fuel pump may further include a pump controller configured to operate the fuel pump based on pressure control commands based on on-board diagnostics CAN signals.

The pump controller may include a rail pressure control logic, e.g. based on an actual rail pressure and a rail pressure set point. By using on-board diagnostics CAN signals (OBD-CAN) the system may be further simplified as OBD messages may be used for simple control features, e.g. rail pressure control. Since these types of messages follow international standards, it may be possible to provide the fuel pump in any vehicle independently from the manufacturer.

According to an exemplary embodiment of the disclosure, the fuel pump may be mechanically detached from the internal combustion engine of the motor vehicle. However, the fuel pump may be in fluid communication with the injection rail of the internal combustion engine via a liquid supply line. For example, the fuel pump may be mounted within an underfloor of a vehicle and thus be spaced apart from the internal combustion engine. A hose, tube or pipe may provide the necessary fluid connection to an injection rail of the engine. The supply line length of the liquid supply line should be as short as possible to prevent the emulsion from separating along the length of the line.

According to an exemplary embodiment of the disclosure, the fuel pump may be powered by a vehicle battery of the motor vehicle. For example, a standard 12 V battery may be employed. When a 48 V electric motor is used, a DC/DC converter may be coupled between the battery and the electric motor. According to an exemplary embodiment of the disclosure, the pump controller of the fuel pump may be communicatively coupled to an engine controller of the motor vehicle. Thus, a dedicated pump controller may be provided, which may, for example, receive power from a battery of the vehicle and may power the pump drive of the fuel pump. However, in other exemplary embodiments, the pump controller may be integrated into the engine controller.

The disclosure will be explained in greater detail with reference to exemplary embodiments depicted in the drawings as appended.

