GB2526913A

GB2526913A - Fuel injection system and vehicle drive equipped therewith, together with motor vehicle and method for operating a fuel injection system

Info

Publication number: GB2526913A
Application number: GB1505789.6A
Authority: GB
Inventors: Oliver Berkemeier; Robin Ivo Lawther
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2014-04-03
Filing date: 2015-04-02
Publication date: 2015-12-09
Anticipated expiration: 2035-04-02
Also published as: GB201505789D0; DE102014206432A1; GB2526913B; DE102014206432B4

Abstract

A fuel line arrangement 5 for a fuel injection system 4 of a motor vehicle. The fuel line arrangement 5 comprises at least one provision line 7 and one valve device 14. The provision line 7 connects a fuel pump 6 to a fuel tank 3. Furthermore, a return line 13 is provided which extends between the fuel tank 3 and the fuel pump 6. The valve device 14 is arranged in the return line 13. Furthermore, the invention is directed to a fuel injection system 4 for an internal combustion engine 2 of a motor vehicle and to a vehicle drive 1 for a motor vehicle, together with a method for operating a fuel injection system 4 for an internal combustion engine 2 of a motor vehicle, the method also relating to dispersing fuel pressure waves into the fuel tank via the open valve 14 in the return line 13.

Description

Fuel injection system and vehicle drive equipped therewith, toqether with motor vehicle and method for operating a fuel iniection system The present invention relates to a fuel line arrangement for a fuel injection system of a motor vehicle] as per the preamble of claim 1, and to a fuel injection system for an internal combustion engine of a motor vehicle, as per the preamble of claim 5. The invention also relates to a vehicle drive for a motor vehicle, as per the preamble of claim 6, and to a correspondingly equipped vehicle having the features of claim 7, and also to a method for operating a fuel injection system, as per the preamble of claim 6.

Aside from internal combustion engines that are operated with diesel fuel, modern gasoline engines are preferably also equipped with a fuel injection system. These are in particular direct injection systems which provide an ignitable fuel-air mixture by direct injection of fuel into the individual combustion chambers. In relation to upstream mixture preparation by means of carburettor systems, lower specific consumption with simultaneously high efficiency is made possible in this way.

The mode of operation of such direct injection systems provides for the fuel for combustion to be pressurized by means of a fuel pump before being conducted onward in the direction of the internal combustion engine. This may be performed by means of an individual pump or multiple pumps, of which one may serve for the initial withdrawal of the fuel from the fuel tank and the other may serve for performing the actual pressurization. Normally, the pressurized fuel is in this case fed into a central collecting line. From there, said fuel can subsequently be branched off and, at a controlled point in time, injected in the required quantity into the respective combustion chambers. The injection itself is performed by way of suitable injection nozzles (injectors). Normally, the fuel pump provided for the build-up of pressure is in the form of a high-pressure pump in order to be able to generate the high injection pressure required for adequate atomization. While it is the case that, downstream of the fuel pump, a low-pressure provision line extending to the fuel tank is sufficient, the upstream distribution is performed by way of at least one corresponding high-pressure provision line.

I

In this context, it is known that the fuel pump arranged between the high-pressure provision line and the low-pressure provision line can, during the operation thereof, induce pressure waves in the low-pressure provision line. In this case, said pressure waves can reach frequencies which cause undesired noises, in particular within the vehicle. To counteract this disadvantageous effect, various solutions have already

been proposed in the prior art.

For example, DE 10 2011111 579 Al discloses a fluid delivery system which serves for the provision of fuel to an internal combustion engine of a motor vehicle. Said document proposes the use of a valve element in the form of a check valve for arrangement in the low-pressure provision line between the fuel pump, which operates with high pressure, and the fuel tank. In this way, the pulsation from the fuel pump into the low-pressure provision line is intercepted by virtue of the valve element briefly closing with every pressure wave that exceeds a pressure level.

DE 10 2010 000 508 Al has also disclosed a direct injection system for an internal combustion engine which has a fuel pump arranged between the fuel tank and the injection valves for the purpose of building up the required pressure. Furthermore, a pulsation reduction device is provided which is arranged in the fuel supply system and which serves for the reduction of the pressure pulsation in the fuel. The fuel pump forms a unit composed of two pumps, one of which is provided for drawing fuel out of the fuel tank, and the other of which is provided for pressurization purposes. In this case, the pulsation reduction device is itself arranged between the fuel pump and a fuel filter which is positioned upstream of the injection valves.

The construction of said pulsation reduction device provides a housing with a valve body that is displaceable counter to a spring element. The valve body has an axial bore which does not extend all the way through it. Furthermore, the valve body has two branch ducts which are oriented radially with respect to, and are connected in fluid-conducting fashion to, the axial bore. By contrast, the housing comprises three ports, of which a first, axial port is connected to the fuel pump, a second, circumferential pod is connected to the fuel filter, and a third, circumferential port is connected to a return line back to the first port for the fuel pump. Within the return line there is arranged a spring-loaded valve element through which flow-restricting openings extend. The displaceable valve body can be moved such that a respective one of its branch ducts is placed in overlap with the second or third circumferential port. At the same time, the axial bore of said valve body is permanently connected in fluid-conducting fashion to the first port.

During normal operation, the fuel flows through the pulsation reduction device by virtue of said fuel flowing from the fuel pump into the valve body via the first port, and flowing from there through the fuel filter via a branch duct which is connected to the second port. When the fuel pressure rises above a preset value, the valve body is displaced axially such that the connection to the fuel filter is interrupted. At the same time, a fluid-conducting connection is produced between the fuel pump and the return line. Pressure waves that now occur are attenuated by virtue of the fact that they strike the valve element arranged in the return line and set said valve element in vibration. Damping of the pressure waves occurs owing to the presence of the fuel in combination with the openings in the valve element. The brief increase in pressure of said fuel is expanded back into the first port of the housing via the return line.

US 5,624,072 A and DE 695 05 730 T2, as the German translation of EP 0 682 177 Al, present direct injection systems which likewise exhibit reduced fuel backf low pulsation. For this purpose, an impulse reduction device is provided which is arranged in an overflow duct that extends between the injection pump and an overflow valve. Aside from the overflow duct, there is also provided a return flow duct which likewise extends between the injection pump and the overflow valve. Here, the overflow valve permits the selective formation of a connecting duct between the overflow duct and the return flow duct to the injection pump. At the same time, the overflow valve makes it possible for the respective connecting duct to be closed during a compression stroke of the injection pump. The impulse reduction device itself comprises a damper chamber into which a pressure increase in the fuel triggered by a pressure wave can be expanded. The rising pressure in the damper chamber is subsequently utilized again to compensate a negative pressure or a low pressure, which, as it were, follows the pressure wave, by virtue of the energy of said rising pressure being released again to the fuel flowing in the overflow duct.

US 6,805,106 B2 and US 2003/0041 842 Al are based on the object of reducing the gases generated in the fuel tank owing to heat, in order thereby to ensure stable control of the injection quantity of fuel. For this purpose, a pressure equalization arrangement arranged between the injection guide at the internal combustion engine and the fuel tank is proposed. The pressure equalization arrangement is in this case connected in fluid-conducting fashion to a provision line, which extends from the fuel pump, situated in the region of the fuel tank, to the injection guide, and to a return line, which runs from the injection guide back to the fuel tank.

The solutions in the prior art which are directed targetedly to reducing the noise-generating pressure waves provide either complex or simple arrangements. In the latter case in particular, it can be assumed that only a limited damping action will be attained. In the light of the known embodiments, it is therefore very much the case that the injection of fuel by means of fuel injection systems still has room for improvement.

Against this background, it is the object of the invention to further develop a fuel line arrangement for a generic fuel injection system and a fuel injection system for an internal combustion engine of a motor vehicle, such that these, while being of relatively simple construction, exhibit improved damping with regard to pressure waves, and associated reduced noise generation, during operation. It is also sought to specify a vehicle drive having a fuel injection system and a correspondingly equipped vehicle, together with a method for operating a fuel injection system, by means of which the damping of pressure waves, and the associated emission of noise, can be improved.

According to the invention, the object is achieved by means of a fuel line arrangement for a fuel injection system having the features of claim 1. Further particularly advantageous refinements of the invention are disclosed in the respective dependent claims.

It is pointed out that the features and measures specified individually in the following description may be combined with one another in any desired technically meaningful way and thus disclose further refinements of the invention.

Below, there will firstly be presented a fuel line arrangement which is suitable for arrangement in or on a fuel injection system for a motor vehicle. The fuel line arrangement comprises at least one provision line and one valve device. The provision line is designed to connect a fuel pump to a fuel tank of the motor vehicle in fluid-conducting fashion. In this case, the fuel pump is provided for charging the fuel, which is ultimately intended for injection into the combustion chamber of an internal combustion engine, with the pressure required for this purpose beforehand.

According to the invention, a return line is also provided in addition to the provision line. Said return line is designed to be arranged between the fuel pump and the fuel tank. In this case, said return line extends, for example, parallel to the provision line.

Here, both the provision line and the return line connect the fuel pump and fuel tank to one another in fluid-conducting fashion. It is crucial here that the valve device is arranged in the return line. In this respect, aside from the provision line and the return line under discussion here, the valve device is also situated, in terms of its arrangement upstream of the fuel pump, on a low-pressure side. By contrast, a high-pressure line running for example from the fuel pump to the internal combustion engine is situated on a high-pressure side.

The advantage resulting from this can be seen in the fact that any pressure waves induced by the fuel pump toward the low-pressure side can, by means of the valve device, be dissipated back into the fuel tank through the return line. For this purpose, the valve device is opened in accordance with the occurring pressure peaks, such that an advantageous release of pressure into the fuel tank is possible.

This yields the advantage, in relation to simple systems which exhibit merely the arrangement of a check valve within the provision line, of a clear separation.

Accordingly, a distinction is made between provision line and return line, wherein the return line serves merely for the discharge of the pressure waves. In this way, the pressure waves do not run back into the provision line. Moreover, during the occurrence of said pressure peaks, the provision line is not closed, such that the fuel flow itself is not abruptly stopped. In particular, the simple closure of the provision line by means of a check valve can itself lead to undesired generation of noise.

As a result, with the relatively simple construction according to the invention, considerably improved damping with respect to pressure waves is achieved during operation. This has the result that the associated generation of noise is greatly reduced, or can even be eliminated entirely. Owing to the configuration according to the invention, the pressure waves are distributed more uniformly, whereby significant pressure peaks that generate audible noises are no longer generated during operation.

It is particularly preferably possible for the valve device to be arranged as close as possible, during operation, to the fuel pump. In other words, that subsection of the return line which is situated between the fuel pump and the valve device is as short as possible. In this way, the vibrations, which trigger pressure waves, in said short subsection of the return line are reduced before these are, as it were, smoothed by the valve device. In this way, the possibility for noise generation in the subsection of the return line is limited, and can have an effect only there, if at all.

It is self-evidently also possible for the valve device to be integrated in or arranged on the fuel pump such that no subsection of the return line which can be set in vibration exists at all between the fuel pump and valve device.

In one advantageous refinement of the basic concept of the invention, the valve device may be in the form of, or may comprise, a check valve. In this case, the check valve is preferably designed to permit a return flow of fuel to the fuel tank in the event of an exceedance of a fuel pressure within or in the direction of the return line. Here, the invention assumes that the exceedance of a fuel pressure refers to the pressure peaks of the pressure waves. In other words, during operation, there may prevail between the fuel pump and valve device a normal fuel pressure, at which the valve device is closed. In this way, no fuel passes back into the fuel tank via the return line.

In this case, the occurrence of pressure waves should be equated to pressure shocks in rapid succession which lead to a temporary pressure increase. When the pressure waves exceed a threshold value, the valve device correspondingly opens such that the respective pressure peak can expand in the direction of the fuel tank.

The threshold value for the opening of the valve device may particularly preferably be structurally predefined or variable and adjustable. The latter possibility enables, for example, the respective combination of fuel pump and valve device to be coordinated with one another such that the greatest possible smoothing of pressure waves can be achieved.

The valve device may advantageously be designed so as to be spring-loaded.

Spring-loaded means that, for example, a valve body arranged in the valve device can be displaced for the purpose of opening and closing the valve device, wherein the displacement thereof must for example be performed counter to a spring element. The respective spring constant of the spring element may in this case be selected such that the force of said spring element corresponds to the required threshold value for the actuation of the valve device. The valve device is particularly preferably designed such that the spring element, in the normal state, effects a closure of the valve device. By contrast, in the event of a corresponding fuel pressure exceeding the threshold value, the spring element is for example deflected or compressed, as a result of which the valve device opens. In this way, the valve device can produce the fluid-conducting connection when a fuel pressure directed counter to the spring loading exceeds the threshold value.

The spring element may for example be a helical spring. Owing to the characteristics of the fuel and possible contact between the spring element and said fuel, the spring element may exhibit corresponding resistance. Accordingly, the helical spring embodiment may for example involve a helical spring composed of metal. The valve device may self-evidently contain, for example, a compressible fluid for permitting the above-described opening and closing process.

The invention provides that the valve device can be adapted, with regard to its opening and/or closing behavior, to the respective injection pressure. Accordingly, the valve device may be designed to open when the fuel pressure within the return line is higher than the required injection pressure. It is ensured in this way that the required injection pressure prevails continuously and is not dissipated in the direction of the fuel tank as a result of premature opening of the valve device.

By means of the fuel line arrangement according to the invention proposed here, the noise-generating pressure waves induced in the low-pressure part by the fuel pump can be conducted via the return line back into the fuel tank such that said pressure waves can no longer incite vibrations that can lead to an audible noise nuisance.

Furthermore, the invention is directed to a fuel injection system which is suitable in particular for supplying fuel to an internal combustion engine. This may preferably be the internal combustion engine of a vehicle; more specifically of a motor vehicle. The fuel injection system has a fuel pump and a fuel line arrangement which comprises a provision line and a valve device.

The fuel line arrangement may preferably be a fuel line arrangement according to the invention as described above.

The fuel pump that is used may be a high-pressure pump in order to make it possible for the required injection pressure for the fuel to be generated. The provision line is designed to connect the fuel pump to a fuel tank of the motor vehicle in fluid-conducting fashion. According to the invention, a return line is also provided. The return line may preferably be connected to the fuel pump, with the free end of said return line being connectable to the fuel tank. The return line is thus designed to connect the fuel pump and the fuel tank to one another in fluid-conducting fashion.

With regard to the position of the valve device, it is provided that the latter is arranged in or on the return line.

The advantages arising from this have already been presented in conjunction with the fuel line arrangement according to the invention discussed in more detail above, such that, at this juncture, reference is made to the statements given above in this regard. The advantageous refinements and embodiments of the fuel line arrangement already discussed above in this connection apply correspondingly to the fuel injection system now proposed. In this respect, a combination of the features explained above in conjunction with the fuel line arrangement and the fuel injection system according to the invention is also envisaged, and correspondingly claimed.

This furthermore also applies to the vehicle drive according to the invention yet to be explained below, and to the correspondingly equipped vehicle, more specifically motor vehicle, according to the invention.

The invention is thus furthermore directed to a vehicle drive which is provided for integration into a motor vehicle. The vehicle drive comprises an internal combustion engine and a fuel tank and also a fuel injection system having a fuel line arrangement which comprises a fuel pump and also a provision line and a valve device.

The fuel injection system used here and/or the fuel line arrangement used here may preferably be the fuel injection system according to the invention and/or the fuel line arrangement according to the invention as have already been described above.

The fuel pump and the fuel tank are connected to one another in fluid-conducting fashion by the provision line. Also provided according to the invention is a return line for the fuel, which return line likewise connects the fuel pump to the fuel tank in fluid-conducting fashion. According to the invention, the valve device is arranged in the return line.

The vehicle, more specifically motor vehicle, according to the invention comprises an internal combustion engine and a fuel injection system with a fuel line arrangement.

The fuel injection system and/or the fuel line arrangement are/is particularly preferably such as have/has been described above.

The invention is also directed to a method which serves for the operation of a fuel injection system for an internal combustion engine of a motor vehicle. The fuel injection system may particularly preferably be the fuel injection system according to the invention as described above.

During the operation of the internal combustion engine, the latter is provided with fuel provided from a fuel tank. Said fuel is drawn out of the fuel tank by means of a fuel pump which is connected in fluid-conducting fashion to the fuel tank via a provision line. Furthermore, the fuel that is drawn out is charged with pressure by means of the fuel pump and is conducted onward to the internal combustion engine. It is self-evidently also possible here for the fuel to be drawn out by means of a fuel pump other than that which serves for the pressurization of the fuel.

According to the invention, there is furthermore provided a return line which connects the fuel pump to the fuel tank in fluid-conducting fashion and which has a valve device. Here, the invention provides that pressure waves induced in the fuel by the fuel pump are dissipated into the fuel tank by virtue of the valve device being correspondingly at least partially opened.

In a preferred refinement, the valve device that is used may be spring-loaded. In this case, the invention provides that the valve device can be at least partially opened by pressure waves, directed counter to the spring loading, in the fuel.

It is advantageously possible for the valve device to be opened when a fuel pressure within the return line is higher than a required injection pressure. It is ensured in this way that the fuel pressure required for the injection of said fuel is not dissipated in the direction of the fuel tank as a result of premature opening of the valve device.

Further advantageous details and effects of the invention are explained in more detail below on the basis of an exemplary embodiment schematically illustrated in figure 1, which is described below.

Figure 1 shows a vehicle drive 1 according to the invention which comprises an internal combustion engine 2 and a fuel tank 3 and a fuel injection system 4. The fuel injection system 4 has a fuel line arrangement 5 and a fuel pump 6. The fuel tank 3 typically serves for storing a volume of fuel K with which the internal combustion engine 2 can be operated.

The fuel line arrangement 5 is designed to connect in particular the internal combustion engine 2 and the fuel tank 3 to one another in fluid-conducting fashion.

For this purpose, the fuel line arrangement 5 has a provision line 7 which extends between the fuel pump 6 and the fuel tank 3. In this case, the provision line 7 is connected to the fuel tank 3 with the interposition of a delivery pump 8.

The delivery pump 8 serves for the withdrawal of the fuel K from the fuel tank 3, from where said fuel is conducted onward in a feed direction V to the fuel pump 6. By means of the operating fuel pump 6, the fuel K is subsequently charged with pressure and fed through a supply line 9 into a central collecting line 10. This arrangement is also referred to as a high-pressure rail. From the collecting line 10, the pressurized fuel K is injected, according to demand, into individual combustion chambers 12 of the internal combustion engine 2 by means of injectors 11 which are connected in fluid-conducting fashion to the collecting line 10.

As can be seen, the fuel line arrangement 5 also comprises a return line 13 which extends between the fuel pump 6, which serves for pressurization purposes, and the fuel tank 3. The return line 13 is in this case designed to connect the fuel pump 6 and the fuel tank 3 to one another in fluid-conducting fashion. In the present case, the return line 13 is, for this purpose, connected to the delivery pump 8. Furthermore, the fuel line arrangementS has a valve device 14 which is arranged in the return line 13.

In this case, the valve device 14 is in the form of a check valve, which is spring-loaded by means of a spring element 15.

In its function as a check valve, the valve device 14 is designed to at least partially open when a fuel pressure prevailing within the return line 13 and acting counter to the spring loading exerted by the spring element 15 is exceeded. This permits a return flow of fuel to the fuel tank 3 in a return direction R. In this way, a pressure wave induced in the fuel K by the operating fuel pump 6 can be dissipated into the fuel tank 3 by virtue of the valve device 14 being correspondingly at least partially opened. Specifically, when the pressure wave arises, the fuel pressure prevailing in the return line 13 rises above the required injection pressure, which according to the invention is expanded into the fuel tank 3.

List of reference signs: 1 Vehicle drive 2 Internal combustion engine of 1 3 Fuel tank of 1 4 Fuel injection system Fuel line arrangement of 4 6 Fuel pump of4 7 Provision line of 5 8 Delivery pump at 3 9 Supply line Collecting line 11 Injector 12 Combustion chamber of 2 13 Returnlineof5 14 Valve device of 5 Spring element of 14 K Fuel V Feed direction of K R Return direction of K In -Ii-

Claims

Patent claims: 1. A fuel line arrangement for a fuel injection system (4) of a motor vehicle, comprising at least one provision line (7) and one valve device (14), the provision line (7) being designed to connect a fuel pump (6) to a fuel tank (3) of the motor vehicle in fluid-conducting fashion, characterized by a return line (13) which is designed to connect the fuel pump (6) and the fuel tank (3) to one another in fluid-conducting fashion, the valve device (14) being arranged in the return line (13). I0
2. The fuel line arrangement as claimed in claim 1, wherein the valve device (14) is a check valve which is designed to permit a return flow of fuel to the fuel tank (3) in the event of an exceedance of a fuel pressure within the return line (13).
3. The fuel line arrangement as claimed in claim 1 or 2, wherein the valve device (14) is spring-loaded, wherein the valve device (14) opens under the action of a fuel pressure directed counter to the spring loading.
4. The fuel line arrangement as claimed in one of the preceding claims, wherein the valve device (14) is designed to open when a fuel pressure within the return line (13) is higher than a required injection pressure.
5. A fuel injection system for an internal combustion engine (2) of a motor vehicle, having a fuel pump (6) and a fuel line arrangement (5), in particular as claimed in one of the preceding claims, which fuel line arrangement comprises a provision line (7) and a valve device (), the provision line (7) being designed to connect the fuel pump (6) to a fuel tank (3) of the motor vehicle in fluid-conducting fashion, characterized by a return line (13) which is designed to connect the fuel pump (6) and the fuel tank (3) to one another in fluid-conducting fashion, the valve device () being arranged in the return line (13).
6. A vehicle drive for a motor vehicle, comprising an internal combustion engine (2) and a fuel tank (3) and also a fuel injection system (4) with a fuel line arrangement (5), in particular as claimed in one of the preceding claims, which fuel injection system comprises a fuel pump (6) and also a provision line () and a valve device (14), the fuel pump (6) and the fuel tank (3) being connected to one another in fluid-conducting fashion by the provision line (7), wherein the fuel pump (6) and the fuel tank (3) are connected to one another in fluid-conducting fashion by a return line (13), the valve device (14) being arranged in the return line (13).
7. A motor vehicle having a vehicle drive (1) as claimed in one of the preceding claims, said vehicle drive comprising an internal combustion engine (2) and a fuel injection system (4) with a fuel line arrangement (5).
8. A method for operating a fuel injection system (4) for an internal combustion engine (2) of a motor vehicle, in particular as claimed in one of the preceding claims, in which method, by means of a fuel pump (6) which is connected in fluid-conducting fashion to a fuel tank (3) via a provision line (7), fuel (K) is drawn out of the fuel tank (3) and conducted onward, under pressure, to the internal combustion engine (2), wherein a return line (13) is provided which connects the fuel pump (6) to the fuel tank (3) in fluid-conducting fashion and which has a valve device (14), with pressure waves which are induced in the fuel (K) by the fuel pump (6) being dissipated into the fuel tank (3) by virtue of the valve device (14) being correspondingly at least partially opened.
9. The method as claimed in claim 8, wherein the valve device (14) is spring-loaded, the valve device (14) being at least partially opened by pressure waves, directed counter to the spring loading, in the fuel (K).
10. The method as claimed in claim 8 or 9, wherein the valve device (14) is opened when a fuel pressure within the return line (13) is higher than a required injection pressure.