Device for pressure-dependent opening of a suction intake

The invention relates to a device (6) for pressure-dependent opening of a suction intake (10), comprising a suction jet pump (11), comprising a feed line (12), an outlet line (13) and the suction intake (10); a valve body (15), displaceably arranged inside the feed line (12) in the delivery direction (14) of the suction jet pump (11) and having an effective area (16) exposed to the feed pressure of the suction jet pump (11); and a spring element (17), arranged between the feed line (12) and the valve body (15), for applying a force in opposition to the feed pressure inside the feed line (12); wherein the effective area (16) of the valve body (15), and the spring element (17) are designed so that the valve body (15) closes the suction intake (10) so that it is fluid-tight below a predefined pressure inside the feed line (12) and opens said intake when the predefined pressure inside the feed line (12) is exceeded. The invention further relates to a fuel tank, comprising a device (6) for pressure-dependent opening of a suction intake (10).

The invention relates to a device for pressure-dependent opening of a suction intake.

The fuel tanks nowadays used in motor vehicles are generally made of plastic by the injection molding or blow molding method and are disclosed, for example, by DE 100 63 414 A1.

Such fuel tanks comprise a separating device, such as a vapor bubble extraction vessel, for example, for separating the fuel from fuel vapors, the vapor bubble extraction vessel being connected to the surroundings by way of an activated charcoal filter. The activated charcoal filter serves to equalize the pressure of the chamber when refilling the fuel tank or in the event of a temperature change. Located in the line to the activated charcoal filter is a valve, which closes the line in extreme driving situations of the motor vehicle for example, or in the event of flashover, and thereby prevents fuel escaping from the fuel tank.

EP 1 504 943 B1 discloses the active extraction of the liquid contained in the vapor bubble extraction vessel by means of a suction jet pump and its return to the fuel tank.

In order to prevent fuel getting into the vapor bubble extraction vessel directly from the fuel tank, a non-return valve is arranged between the suction jet pump and the vapor bubble extraction vessel.

In a suction jet pump the suction effect is produced by a fluid jet, also called the motive fluid, which through momentum exchange draws in, accelerates and compresses/delivers another fluid, also called the suction fluid. The suction jet pumps generally used in motor vehicles nowadays generate a vacuum of 100 mbar, for example. If an additional non-return valve is situated between the suction jet pump and the vapor bubble extraction vessel, the vacuum generated must serve both to open the non-return valve and to extract the liquid contained in the vapor bubble extraction vessel. One disadvantage to the non-return valves, known in the state of the art, between the suction jet pump and the vapor bubble extraction vessel, which are embodied as so-called “mushroom valves”, for example, is that a proportion of the effective vacuum of the suction jet pump is lost due to the opening of the non-return valve. In order to reduce the loss of effective vacuum of the suction jet pump, the closing force of the non-return valve is generally limited, which, however, is detrimental to the leak-tightness of the non-return valve. Moreover, with a low closing force of the non-return valve, any fouling leads more rapidly to leakages.

The object of the invention, therefore, is to provide a device which with the suction jet pump running establishes a fluid connection between the suction jet pump and a separating device, such as a vapor bubble extraction vessel, for example, and which with the suction jet pump switched off tightly closes the fluid connection between the fuel tank and the separating device, in particular one which minimizes a loss of the effective vacuum of the suction jet pump.

According to the invention the object is achieved by a device for pressure-dependent opening of a suction intake, comprising a suction jet pump, comprising a feed line, an outlet line and the suction intake; a valve body, displaceably arranged inside the feed line in the delivery direction of the suction jet pump and having an effective area exposed to the feed pressure of the suction jet pump; and a spring element, arranged between the feed line and the valve body, for applying a force in opposition to the feed pressure inside the feed line; wherein the effective area of the valve body, and the spring element are designed so that the valve body closes the suction intake so that it is fluid-tight below a predefined pressure inside the feed line and opens said intake when the predefined pressure inside the feed line is exceeded.

The device according to the invention has the advantage that it opens and closes the suction intake between the suction jet pump and the separating device as a function of the pressure in the feed line of the suction jet pump. The pressure prevailing in the feed line when the suction jet pump is in operation therefore actuates a valve, closed in the inoperative state, thereby opening the suction intake. If the pressure in the feed line of the suction jet pump falls below a predefined pressure, the valve is returned to the inoperative state and the suction intake is closed so that it is fluid-tight. The opening force of the device according to the invention may be freely selected through the size of the effective area of the valve body in connection with the feed pressure of the suction jet pump. The closing forces applied by the spring element must be designed according to the desired sealing forces, taking into account the feed pressure of the suction jet pump and the effective area of the valve body, so that the device according to the invention opens the feed line when a predefined pressure is reached inside the feed line.

A particular distinguishing feature of the device according to the invention is a very low pressure loss between the suction jet pump and the separating device, thus increasing the efficiency of the suction jet pump.

According to a variant of the invention, at least one first sealing element is arranged between the feed line and the valve body. The first sealing element serves to prevent the fluid transported in the feed line escaping through the joint between the feed line and the valve body displaceably arranged therein.

According to a further variant of the invention, a second sealing element is arranged on the valve body in the area of the suction intake of the suction jet pump. The second sealing element serves to improve the leak-tightness of the device according to the invention in the area of the suction intake below the predefined pressure inside the feed line.

According to a variant of the invention, the valve body comprises a fluid-transmitting passage, which is arranged in the delivery direction of the suction jet pump and which serves as part of the feed line of the suction jet pump. By means of the passage, therefore, the valve body serves as part of the feed line. This affords the most rectilinear fluid flow possible through the feed line, thereby minimizing the pressure losses due to the device according to the invention.

In a further variant of the invention, the cross section in the area between the feed line and the outlet line has a constriction, formed by two opposing cones, for example, which are united at the point of the smallest diameter. A fluid line connected to the suction intake is arranged in the immediate vicinity of the constriction. If a fluid is delivered through the feed line at a specific feed pressure, the dynamic pressure at the constriction is at a maximum, and the static pressure at a minimum, so that the velocity of the delivered fluid increases. At the same time the pressure falls in the fluid line to the suction intake. The resulting vacuum serves to draw in a fluid through the suction intake.

According to a further variant of the invention, the suction jet pump further comprises a nozzle, arranged at the end of the feed line in the delivery direction of the suction jet pump. For the purposes of the invention, a nozzle is a tubular, technical device which may have the same area over its entire length, or which may widen, taper or have other complex forms. The nozzle serves to convert the pressure prevailing inside the feed line into kinetic energy, thereby further increasing the effective vacuum of the suction jet pump.

According to an especially suitable variant of the invention, the valve body and the nozzle are integrally formed. In particular, the effective area of the valve body, and the spring element are designed so that under the displacement of the valve body usually occurring the nozzle is arranged in the optimum position relative to the outlet line of the suction jet pump, in order to obtain the greatest possible suction effect of the suction jet pump. Since the pressure usually prevailing in the feed line is known, the effective area of the valve body, and the spring element can be designed so that under the displacement of the valve body usually occurring at the pressure usually prevailing in the feed line the nozzle, integrally formed with the valve body, is optimally arranged in relation to the outlet line of the suction jet pump, thereby maximizing the suction effect of the suction jet pump.

The invention further relates to a fuel tank, comprising a device for pressure-dependent opening of a suction intake according to the preceding description.

In a variant of the fuel tank, the feed line is connected to a fuel supply pump via a first fuel line, the outlet line is connected to the interior of the fuel tank via a second fuel line and the suction intake is connected to a separating device, in particular to a vapor bubble extraction vessel. Here the device according to the invention is designed so that the separating device is drained by the suction jet pump when the fuel supply pump provides a predefined pressure inside the feed line.

Alternatively, the suction intake is connected to the wall of a swirl pot. When the fuel supply pump delivers fuel through the feed line and outlet line of the suction jet pump, fuel is likewise delivered by means of the suction jet pump via the suction intake arranged in the wall of the swirl pot. When the fuel supply pump is switched off, the pressure inside the feed line falls below the predefined pressure and the suction intake in the wall of the swirl pot is closed by the valve body of the device according to the invention. The swirl pot, in which the fuel supply pump is usually arranged, can therefore not run empty when the fuel supply pump is idle.

FIG. 1schematically shows a sectional view through a fuel tank1having a chamber for receiving fuel. The fuel tank1comprises a filler neck2for filling the fuel tank1.

Venting valves3, which serve for regulating the pressure inside the fuel tank1, are arranged at what is, in the installed position, the upper end of the fuel tank1.

The vapor bubble extraction vessel4serves for separating fuel from fuel vapors and is generally connected to the surroundings via an activated charcoal filter. The fuel accumulating in the vapor bubble extraction vessel4is usually extracted actively, for example by means of a suction jet pump11. It must be ensured here, however, that when the suction jet pump11is switched off no fuel from the fuel tank1gets into the vapor bubble extraction vessel4.

For this purpose, according to the invention a device6for pressure-dependent opening of the suction intake10is arranged inside the fuel tank1.

The device6for pressure-dependent opening of the suction intake10comprises a feed line12, which is connected to a fuel supply pump5via a first fuel line7, an outlet line13, which is connected to the interior of the fuel tank via a second fuel line8, and the suction intake10, which is connected to the vapor bubble extraction vessel4via a third fuel line9. The second fuel line8is also referred to as a combined line and is connected to the interior of the fuel tank1, in order to return the fuel extracted from the vapor bubble extraction vessel4into the fuel tank1.

The first fuel line7is suitably not just connected to the fuel pump5but is embodied as a branch of a main supply line (not shown), in order to divert a proportion of the fuel delivered by the fuel pump5and to carry it through the device6according to the invention for pressure-dependent opening of a suction intake10.

FIG. 2shows a detailed view of the device6according to the invention for pressure-dependent opening of a suction intake10, comprising a suction jet pump11, comprising the feed line12, the outlet line13and the suction intake10; a valve body15, displaceably arranged inside the feed line12in the delivery direction14of the suction jet pump11and having an effective area16exposed to the feed pressure of the suction jet pump11; and a spring element17, arranged between the feed line12and the valve body15, for applying a force in opposition to the feed pressure inside the feed line12. The effective area16of the valve body15, and the spring element17are designed so that the valve body15closes the suction intake10so that it is fluid-tight below a predefined pressure inside the feed line12and opens said intake when the predefined pressure inside the feed line12is exceeded. The movement of the valve body15inside the feed line12is therefore controlled by the feed pressure inside the feed line12, the feed pressure inside the feed line12being applied by the fuel supply pump5.

According toFIG. 2two first sealing elements18, which are embodied in the form of an O-ring, are arranged between the feed line12and the valve body15. The first sealing elements18seal off the connection between the feed line12and the valve body15displaceably arranged therein.

In the area of the suction intake10of the suction jet pump11the valve body15comprises a second sealing element19, which improves the leak-tightness between the valve body15and the suction intake10when the device6according to the invention for pressure-dependent opening of a suction intake10is in the closed state.

The valve body15additionally comprises a fluid-transmitting passage20, which is arranged in the delivery direction14of the suction jet pump11and which serves as part of the feed line12of the suction jet pump11. This affords the most rectilinear flow of fuel possible from the fuel supply pump5via the feed line12and the passage20in the valve body15to the outlet line13.

The suction jet pump11further comprises a constriction21of the cross section in the area between the feed line12and the outlet line13, which is formed, for example, by two opposing cones, which are united at the point of the smallest diameter. Such a configuration is also referred to as a Venturi nozzle and is one possible way of obtaining the suction effect of a suction jet pump11.

The suction jet pump11according toFIG. 2further comprises a nozzle22, which is arranged at the end of the feed line12in the delivery direction14of the suction jet pump11and which is continued through the passage20. Since the nozzle22converts the pressure inside the feed line12into kinetic energy, the suction effect of the suction jet pump11is further improved by means of the nozzle22.

As can be seen fromFIG. 2, the valve body15and the nozzle22are integrally formed.

The effective area16of the valve body15, and the spring element17are designed so that under the displacement of the valve body15usually occurring the nozzle22is arranged in the optimum position relative to the outlet line13of the suction jet pump11, in order to obtain the greatest possible suction effect. The displacement of the valve body15usually occurring can be determined from the pressure prevailing in the feed line12, together with the effective area16of the valve body15and the spring force of the spring element17. The pressure inside the feed line12is applied by the fuel supply pump5and is usually stable.

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