Suction jet pump

The subject matter of the invention is a suction jet pump, comprising a driving jet nozzle, a mixing tube, an intake opening, a working-fluid line connected to the driving jet nozzle and a valve which is arranged in the working-fluid line. Suction jet pumps are used in fuel tanks of motor vehicles.

Such suction jet pumps are used in fuel tanks in order to supply fuel from various regions of the fuel tank to a feed unit, which feed unit feeds fuel from the fuel tank to an internal combustion engine of the motor vehicle. In order to drive the suction jet pump, a portion of the fuel fed by the fuel pump is branched off and supplied via the working-fluid line of the suction jet pump. When starting the internal combustion engine, the fuel pump should feed fuel in a sufficient quantity to the internal combustion engine as fast as possible. To this end, a valve is arranged in the working-fluid line, which valve only opens when the system pressure is reached so that, particularly in the event of a starting process, all the fed fuel is first supplied to the internal combustion engine.

In order to improve the starting behavior of the motor vehicle, it is known to increase the pressure in the feed line for a short time. To this end, the flow rate of the fuel pump is increased for a short time during the starting process. However, the effect of the valve in the working-fluid line is thus cancelled out, which valve is supposed to release the working-fluid line only when the system pressure is reached. This has the disadvantage that, as a result of the increase in pressure, the valve opens, which valve is supposed to separate the suction jet pump from the fuel supply for the starting process. A portion of the fuel thus reaches the suction jet pump and is not available for the internal combustion engine. In order to nevertheless ensure a sufficient supply of the internal combustion engine with fuel during a starting process, the fuel pump must be dimensioned such that it, as well as the increased demand on the internal combustion engine, also supplies the increased feed quantity for the suction jet pump as a result of the opened valve. These two increased feed quantities lead to an overdimensioning of the fuel pump. Such fuel pumps require significantly more space and are more costly.

The object of the invention is therefore to create a suction jet pump which only operates when the fuel supply system operates with system pressure.

According to the invention, the object is achieved in that a throughflow opening is arranged in the housing, that a valve body is arranged on both sides of the throughflow opening such that the throughflow opening can be closed both on the inlet side and on the outlet side, and that at least one spring is arranged within the housing such that it holds the valve body in a position closing the throughflow opening on the outlet side until the system pressure is reached.

The valve arranged in the working-fluid line of the suction jet pump is closed in the depressurized state in that the spring holds the valve body on the outlet side in a position closing the throughflow opening. As soon as the fuel pump reaches system pressure, the force acting on the valve body is larger than the spring force, as a result of which the valve body is moved out of the position closing the throughflow opening on the outlet side. The valve is thus open and fuel can reach the suction jet pump. If the pressure rises above the system pressure during a starting process, the valve body is moved further counter to the spring force until it reaches a position closing the throughflow opening on the inlet side, as a result of which the valve closes. The valve according to the invention allows operation of the suction jet pump in a presettable pressure range, wherein the suction jet pump is switched off above and below this pressure range. This means that the suction jet pump operates only under normal conditions, while, in critical situations in which the supply of the internal combustion engine with fuel is supposed to be ensured, the fuel fed by the fuel pump only reaches the internal combustion engine. The fuel pump can thus be of smaller dimensions since the flow rate of the fuel pump is only determined by the internal combustion engine and the suction jet pump in the case of system pressure, while in the case of operation of the fuel pump above the system pressure the flow rate is exclusively determined by the internal combustion engine as a result of the switching off of the suction jet pump.

The throughflow opening is of a particularly simple configuration if it is embodied as a diaphragm.

A reliable sealing off is achieved according to another advantageous configuration in that the valve body possesses two sealing elements which interact on the inlet side and the outlet side with a sealing seat at the throughflow opening.

The sealing elements of the valve body respectively comprise in a simple and thus low-cost formation an annular disk, which annular disks are arranged on the valve body.

The structure of the valve body is simplified according to another configuration if the sealing elements are arranged on both sides of the diaphragm relative to the direction of flow such that they surround the throughflow opening.

A defined position of the valve body in the open position in the case of system pressure is achieved in a further configuration in that a second spring is arranged relative to the first spring, wherein the first spring is designed with respect to the opening pressure and the second spring allows a further movement of the valve body only above the system pressure. In this manner, a movement of the valve body is prevented in the case of a system pressure in the open position.

The springs used can be both pressure springs and tension springs, wherein the springs are arranged between the housing and the valve body.

Insofar as pressure springs are used, these can also be arranged in a different configuration between the valve body and the throughflow opening. For improved guidance and receiving of the pressure springs, a shoulder is formed on the valve body in a further configuration.