The invention relates to a fuel supply system for supplying an internal combustion engine of a motor vehicle, having two feed means, which are arranged in a fuel tank, for feeding fuel, and having a connecting piece for guiding the fuel fed by the feed means from two inlets, which are each connected to the feed means, to an outlet.
Fuel supply systems of this type are used, for example, for motor vehicles having a high power consumption and narrow fuel tanks, in which an individual feed means is frequently insufficient in terms of power, and are known in practice. Furthermore, fuel supply systems of this type are used in what are referred to as saddle tanks, in which the fuel tank has two chambers, with suction jet pumps which feed fuel into one or two baffles additionally being arranged in the individual chambers. The connecting pieces combine a flow from two lines, for example from the feed units, into one fuel line leading to the internal combustion engine or to one or two suction jet pumps. The connecting pieces of the known fuel supply system are conventional T-pieces.
A disadvantage of the known fuel supply system is that, for example, if one of two feed means is in operation, fuel may overflow from one of the feed means to the feed means which has been switched off. This results in an unnecessary circulation of the fuel and to energy losses in the feeding of the fuel to the internal combustion engine. In order to avoid this problem, a practical remedy is to use a respective nonreturn valve between the inlets and the feed means. However, this results in a very large structural outlay on the fuel supply system.
The invention is based on the problem of developing a fuel supply system of the type mentioned at the beginning in such a manner that an unnecessary overflowing of the fuel via the connecting piece is avoided and that the fuel supply system is constructed in a particularly simple manner.
This problem is solved according to the invention by the connecting piece having a mixer valve and by, when there is a difference in pressure between the inlets, the mixer valve closing the inlet with the low pressure.
This design makes it possible for the mixer valve to prevent fuel from being able to overflow from one inlet to the other inlet. In the case of two feed units which are connected to the inlets but only one of which is in operation, fuel can therefore be prevented from overflowing to the feed unit which has been switched off. Furthermore, the fuel supply system according to the invention does not require any additional nonreturn valves in the lines leading from the feed units to the connecting piece. The fuel supply system according to the invention is therefore composed of particularly few components which are to be assembled, and is therefore constructed in a particularly simple manner. Of course, by connecting a plurality of mixer valves one behind another, more than two feed means can be connected to a single outlet for the connection of a single fuel line. According to one advantageous development of the invention, the connection of the fuel flows fed by the feed means is structurally particularly simple if the inlets each have a valve seat, and if between the valve seats a valve body is guided moveably by the pressure in the inlets, and if the distance between the valve seats is greater than the width of the valve body. To avoid periodically occurring pressure fluctuations, the movement of the valve body may of course also be damped.
When there is approximately identical pressure in the inlets, the consumer can be supplied with fuel, according to one advantageous development of the invention, via the two feed means if in a central position of the valve body between the valve seats the two inlets are connected to the outlet. This ensures that, when the internal combustion engine requires a large quantity of fuel, both feed units can feed fuel jointly.
According to another advantageous development of the invention, a forward flow line leading to the internal combustion engine can be prevented from running dry if a nonreturn valve is arranged between the mixer valve and the outlet.
During a supplying of suction jet pumps with fuel, a pipette effect can be avoided, according to another advantageous development of the invention, if a control valve is arranged between the mixer valve and the outlet, which control valve, in the unpressurized state, connects the outlet to an opening leading into the fuel tank and, in the pressurized state, closes the opening. By means of this design, when the feed means are feeding, the opening is closed and fuel flows from the mixer valve of the connecting piece to the outlet and therefore to the suction jet pumps. However, when the feed means are switched off, the control valve prevents fuel from being sucked up via the outlet.
The installation of the fuel supply system according to the invention becomes particularly simple if the mixer valve together with the control valve or the nonreturn valve is designed as a structural unit. This makes it possible to preassemble the mixer valve together with the control valve or together with the nonreturn valve outside the fuel tank to form the structural unit and subsequently to insert it with little outlay into the fuel tank.
The fuel supply system according to the invention is manufactured particularly cost-effectively if the mixer valve and the control valve or the nonreturn valve have a common housing.
The manufacturing costs of the fuel supply system according to the invention are further reduced if the mixer valve and/or the control valve and/or the nonreturn valve have straight channels for receiving the valve body, and if the channels are closed by a closure means. The closure means is preferably designed as a cap or stopper connected to the housing in a form-fitting manner.
According to another advantageous development of the invention, the mixer valve becomes structurally particularly simple if one of the valve seats of the mixer valve is arranged in the closure means and the other of the valve seats is arranged in the housing.
If the feed means are divided into a basic-load feed means and a peak-load feed means, one of the inlets can easily be closed in the basic position if the valve body of the mixer valve is prestressed into a designated position.
According to another advantageous development of the invention, the guiding of the valve body between the two valve seats requires a particularly low outlay if the valve body of the mixer valve is designed as a ball.
The invention permits numerous embodiments. To further clarify its basic principle, a number of embodiments are illustrated in the drawing and are described below. In the drawing
The feed units 5, 5′ are in each case electrically driven and in each case have a preliminary stage 9 and a main stage 10. The main stages 10 feed fuel from the baffles 6, 6′ via a first connecting piece 11 to the internal combustion engine 2. The preliminary stages 9 feed fuel from the baffles 6, 6′ via a second connecting piece 12 to suction jet pumps 13, 13′ arranged in the chambers 3, 3′. The suction jet pumps 13, 13′ are thereby supplied with fuel as motive agent and feed fuel from the chambers 3, 3′ into the baffles 6, 6′. Furthermore, the baffles 6, 6′ each have a bottom valve 14 via which fuel flows from the fuel tank 1 into the baffles 3, 3′. Filters 15 of the main stages 10 are arranged in the baffles 6, 6′. The feed units 5, 5′ can be operated individually or together in accordance with the requirements of the internal combustion engine 2. If the internal combustion engine 2 requires a low amount of fuel, one of the feed units 5, 5′ is therefore switched off.
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10 2004 041 203 | Aug 2004 | DE | national |
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