Valve unit for a fuel tank

Abstract

Valve unit (2a, 2b, 2c, 2d) for a fuel tank, a) comprising a housing (4), a1) with a tank connection (6a) for connecting the valve unit (2) to the fuel tank and a2) with a filter connection (6b) for connecting the valve unit (2) to an activated carbon filter, b) comprising a venting channel (8), wherein the tank connection (6a) and the filter connection (6b) are fluidically connected or connectable via the venting channel (8), and wherein a main venting valve (10) with a valve element is arranged in the venting channel (8), which closes the venting channel (8) in a closed position and opens it in a release position, c) comprising a pilot valve (12) for opening the main venting valve (10), wherein the pilot valve (12) is connected on the one hand to a pressure chamber (14) of the main venting valve (10) and on the other hand to an overflow area (16) is fluidically connected or connectable,wherein the overflow area (16) fluidically connects or can fluidically connect the tank connection (6a) or a tank-side venting channel (8a) and the filter connection (6b) or a filter-side venting channel (8b),d) comprising exactly three check valves, whereind1) a tank pressure chamber check valve (18a) is fluidically connected or connectable on the one hand to the tank connection (6a) or the tank-side venting channel (8a) and on the other hand to the pressure chamber (14) of the main venting valve (10),d2) an overflow area tank check valve (18c) is fluidically connected or connectable on the one hand to the overflow area (16) and on the other hand to the tank connection (6a) or the tank-side venting channel (8a), andd3) an overflow area filter check valve (18d) is fluidically connected or connectable on the one hand to the overflow area (16) and on the other hand to the filter connection (6b) or is fluidically connected or connectable to the filter-side venting channel (8b).

Description

[0001] The invention relates to a valve unit for a fuel tank of a motor vehicle. In particular, the invention relates to a valve unit for the controlled and / or regulated discharge or introduction of a fluid, preferably gas or air or hydrocarbon-containing fuel vapors or hydrocarbon-enriched or saturated air, from or into a fuel tank. In other words: The valve unit can be used in connection with venting or venting the fuel tank. The following use of the term "venting" is intended to also encompass the possibility of ventilation; i.e., a venting channel can also be used as a ventilation channel, and a venting valve can also be used as a ventilation valve.

[0002] In today’s motor vehicle tank systems, such a valve unit has to fulfil different tasks: During refueling, fuel is added to the tank, causing excess pressure to build up. To relieve this excess pressure and restore normal pressure—a fuel tank is a low-pressure tank—the hydrocarbon-enriched air must be expelled from the tank. In conventional tank systems in Europe, these hydrocarbon emissions are exclusively recirculated during the refueling process via a line connecting the tank to the filler neck and extracted through the fuel nozzle. In conventional tank systems in the USA, the entire hydrocarbon-enriched gas volume must be passed through the activated carbon filter (hereinafter also "ACF") during the refueling process to prevent hydrocarbon emissions from being released into the atmosphere. Since fresh air from the environment is also drawn into the tank through the filler neck, which can become enriched with hydrocarbons there, this would lead to a greater loading of the ACF. For this reason, in tank systems in the USA, a small portion of the gases is also recirculated via a line connecting the tank to the filler neck ("recirculation").

[0003] Another key function of the valves or valve units in a tank system is to limit the amount of fuel in the fuel tank. The refueling process at a pump ends when the fuel level in the filler pipe rises, thereby shutting off the fuel pump nozzle. To allow the fuel level in the filler pipe to rise, the vent line in the tank is closed at a certain fill level by a float-controlled valve, a so-called fill-limit vent valve (FLVV). Subsequently, the pressure in the tank rises, preventing any further fuel from being added.

[0004] Even during normal vehicle operation, excess pressure can build up in the fuel tank, e.g., due to fuel heating. Negative pressure can also develop, e.g., due to fuel cooling.

[0005] However, most previously known valves or valve units used for the aforementioned functions can only operate when there is excess pressure in the fuel tank, which significantly limits the valve's application area. One such valve is known, for example, from US 2010 / 0051116 A1.

[0006] WO 2019 / 081709 A1 discloses a valve system for a fuel tank comprising a housing with a tank connection for connecting the valve unit to the fuel tank and with a filter connection for connecting the valve unit to an activated carbon filter and / or with a filler pipe connection for connecting the valve unit to a filler pipe of the fuel tank. Either the tank connection and the filter connection or the tank connection and the filler pipe connection are fluidically connected or connectable to one another via a main venting channel, wherein at least one main venting valve with a valve element is arranged in the main venting channel, which closes the main venting channel in a closed position and opens it in a released position. The main venting valve comprises a first pilot valve and a second pilot valve.The two pilot valves allow the main vent valve to be controlled in both overpressure and underpressure conditions in the fuel tank. While this known valve system can operate in both overpressure and underpressure conditions, two pilot valves are required to fulfill this function, one for overpressure and one for underpressure, resulting in increased complexity for controlling the valve system.

[0007] It is therefore an object of the invention to propose a valve unit which can be used both in the case of overpressure and underpressure in the fuel tank and which requires only one pilot valve.

[0008] The object is achieved by a valve unit for a fuel tank, in particular a valve unit for the controlled and / or regulated discharge or introduction of a fluid, preferably gas or air or hydrocarbon-enriched or saturated air, from or into the fuel tank, having the features according to claim 1. The valve unit comprises a housing with a tank connection for connecting the valve unit to the fuel tank and with a filter connection for connecting the valve unit to an activated carbon filter. Furthermore, the valve unit comprises at least one vent channel, wherein the tank connection and the filter connection are fluidically connected or connectable via the vent channel. A main vent valve with a valve element is arranged in the vent channel, which closes the vent channel in a closed position and opens it in a released position.

[0009] Furthermore, the valve unit comprises a pilot valve for opening the main vent valve, wherein the pilot valve is fluidically connected or connectable on the one hand to a pressure chamber of the main vent valve and on the other hand to an overflow area, wherein the overflow area fluidically connects or can fluidically connect the tank connection or a tank-side vent channel and the filter connection or a filter-side vent channel.

[0010] The valve unit further comprises exactly three check valves; therefore, no additional check valves are provided. A tank pressure chamber check valve is fluidically connected or connectable to the tank connection or the tank-side venting channel on the one hand, and to the pressure chamber of the main venting valve on the other. An overflow area tank check valve is fluidically connected or connectable to the overflow area on the one hand, and to the tank connection or the tank-side venting channel on the other. An overflow area filter check valve is fluidically connected or connectable to the overflow area on the one hand, and to the filter connection or the filter-side venting channel on the other.

[0011] The term "tank-side" vent duct refers to the section of the vent duct between the fuel tank or the tank connection and the main vent valve. Accordingly, the term "filter-side" vent duct refers to the section of the vent duct between the main vent valve and the filter connection or the activated carbon filter. The term "filler pipe side" vent duct used below describes the section of the vent duct between the tank connection or the tank-side vent duct and a filler pipe connection or the filler pipe.

[0012] The use of the term venting is intended to include the possibility of ventilation, i.e. a venting duct can also be used as a ventilation duct or a venting valve can also be used as a ventilation valve.

[0013] The inventive arrangement of the pilot valve and the three check valves, as well as the overflow area, makes it possible to provide a valve or valve unit that can implement all required functions under both overpressure and underpressure conditions with just one pilot valve and one main vent valve. By controlling the pilot valve, the main vent valve can be opened selectively under both overpressure and underpressure conditions, without the need for an additional pilot valve or additional control electronics. The valve unit according to the invention thus allows for targeted venting and venting of the fuel tank under both overpressure and underpressure conditions.

[0014] In further advantageous embodiments, the housing can have a filler pipe connection for connecting the valve unit to a filler pipe of the fuel tank. The tank connection and the filler pipe connection can also be connected to each other via a vent channel.

[0015] Preferably, the valve element of the main vent valve is designed as a valve diaphragm, wherein the valve diaphragm has a pressure side facing the pressure chamber of the main vent valve and a flow side facing the tank connection or the tank-side vent channel, the filter connection or the filter-side vent channel, and the filler pipe or the filler pipe-side vent channel. The flow side of the valve diaphragm closes the vent channel when the valve element is in the closed position and opens the vent channel when the valve element is in the open position. A preloading element arranged in the pressure chamber of the main vent valve exerts a force on the pressure side of the valve diaphragm.In particular, this preloads the valve element, specifically the valve diaphragm, in its closed position. To move it into the release position, at least the force exerted by the preload element must be overcome, for example, by appropriate pressure conditions on the pressure side and the flow side of the valve diaphragm. The preload element itself is guided, for example, by means of guide means arranged on the valve diaphragm or the housing.

[0016] In a preferred embodiment of the valve unit, it comprises at least one bypass valve, which is or can be fluidically connected to the tank connection or the tank-side venting channel on the one hand, and to the filter connection or the filter-side venting channel on the other. The at least one bypass valve can fluidically connect the tank connection or the tank-side venting channel and the filter connection or the filter-side venting channel directly or indirectly, e.g., via an intermediate space. Such bypass valves allow the pressure in the fuel tank to be more precisely regulated during operation of the motor vehicle.

[0017] In a further preferred embodiment, the valve unit comprises at least one recirculation valve, which is fluidically connected or connectable to the tank connection or the tank-side venting channel on the one hand, and to the filler pipe connection or the filler pipe-side venting channel on the other. Such a recirculation valve enables precise control of the recirculation flow during refueling.

[0018] A further development of the invention provides that the valve unit comprises at least one overpressure protection valve, in particular a mechanical overpressure protection valve, which is fluidically connected or connectable to the tank connection or the tank-side venting channel on the one hand, and to the filter connection or the filter-side venting channel on the other. This ensures that the pressure in the fuel tank does not exceed a certain overpressure limit, especially when the valve system is not in operation.

[0019] A further advantageous embodiment provides that the valve unit comprises at least one vacuum protection valve, which is fluidically connected or connectable to the tank connection or the tank-side venting channel on the one hand, and to the filter connection or the filter-side venting channel on the other. This ensures that the pressure in the fuel tank does not exceed a certain vacuum limit.

[0020] In a structurally advantageous embodiment, the housing of the valve unit forms one or more inner walls that separate the pressure chamber, the overflow area, the tank-side venting channel, the filter-side venting channel, and / or the filler-pipe-side venting channel from one another. The pilot valve, the tank pressure chamber check valve, the overflow area tank check valve, the overflow area filter check valve, the at least one bypass valve, the at least one recirculation valve, the overpressure protection valve, and / or the underpressure protection valve are each arranged in an opening formed in the inner wall or walls.The pilot valve, which is fluidically connected or connectable to a pressure chamber of the main vent valve on the one hand and to an overflow area on the other, is thus arranged in an opening in an inner wall separating the pressure chamber of the main vent valve and the overflow area. This above explanation applies analogously to the other valves mentioned above.

[0021] The pilot valve is a valve controlled by an actuator, preferably an SMA valve or an EAP valve or a solenoid valve or a pneumatic valve.

[0022] The basic principle of SMA (shape memory alloy) valves is well known. Essentially, the SMA element, a wire or ribbon formed from a shape memory alloy, is subjected to current above a transformation temperature at which the structure transforms from a martensitic to an austenitic structure, causing it to heat up and shorten. The SMA element is in contact with the valve element in such a way that, as the valve element shortens, the SMA element exerts a force on the valve element and actuates it, thereby opening or closing a valve opening.

[0023] The basic functionality of EAP valves (ElectroActive Polymers) is also well known. EAPs are polymers that change their shape when an electrical voltage is applied. One example is dielectric elastomers (DEA valves - valves with a dielectric elastomer actuator). DEAs, for example, consist of several polyurethane layers with graphite layers arranged between them as electrodes. If an electrical voltage is applied to the electrodes so that neighboring electrodes have different polarity, the electrodes attract each other and move towards each other due to the flexibility of the polyurethane layer (elastomer), which reduces their wall thickness and increases the surface area of the polyurethane layers. By appropriately arranging the actuator within the valve, the valve can be opened.

[0024] It is further preferred that the at least one bypass valve is an SMA valve or an EAP valve or a solenoid valve or a pneumatic valve.

[0025] Likewise, the at least one recirculation valve may preferably be an SMA valve or an EAP valve or a solenoid valve or a pneumatic valve.

[0026] The invention will be explained in more detail below with regard to further features and advantages based on the description of an embodiment according to the invention and further non-inventive embodiments and with reference to the accompanying drawings. Each of these drawings shows a schematic diagram: Fig. 1A is a schematic representation of a valve unit according to a first embodiment of the invention with three check valves, Fig. 1B is a schematic representation of a valve unit according to a second embodiment not according to the invention with four check valves, Fig. 2 a schematic representation of a valve unit according to a third embodiment not according to the invention, Fig. 3 a schematic representation of a valve unit according to a fourth embodiment not according to the invention, Fig. 4 a schematic representation of a valve unit according to a fifth embodiment not according to the invention, Fig. 5 the valve unit not according to the invention according to Fig. 2 in a perspective view, Fig. 6 the valve unit not according to the invention according to Fig. 2 in a bottom view without case bottom, Fig. 7 the valve unit not according to the invention according to Fig. 2 in a top view without housing cover, Fig. 8 the valve unit not according to the invention according to Fig. 2 in a perspective view without housing cover, Fig. 9 the valve unit not according to the invention according to Fig. 2 in a sectional view along line AA from Fig. 5.

[0027] Based on the Fig. 1A to Fig. 4, each of which shows a schematic representation of a valve unit, will first explain the basic structure and basic functionality. Corresponding components are provided with the same reference numerals. Fig. 5 to Fig. 9 show the valve unit not according to the invention according to Fig. 2 in different representations.

[0028] Fig. 1A and Fig. 1B each show a valve unit 2a for the controlled and / or controlled and / or regulated discharge or introduction of a fluid, preferably gas or air or air enriched or saturated with hydrocarbons, from or into the fuel tank according to a first embodiment of the invention ( Fig. 1A) and a second embodiment not according to the invention ( Fig. 1B) in a schematic representation. The valve unit 2a comprises a housing 4. The housing 4 has a tank connection 6a for connecting the valve unit 2a to the fuel tank (not shown). Furthermore, the valve system 2 comprises a filter connection 6b for connecting the valve unit 2a to an activated carbon filter (not shown). Furthermore, the valve system 2 can comprise a filler pipe connection 6c for connecting the valve unit 2a to a filler pipe (not shown), as is exemplary here for the non-inventive embodiment according to Fig. 1B. The valve unit 2a can be connected directly to the fuel tank, the activated carbon filter, and the filler pipe via vent lines (not shown) or without vent lines. The housing 4 can comprise an intermediate housing 4a, which forms the tank connection 6a, the filter connection 6b, and optionally the filler pipe connection 6c. In the assembled state, the intermediate housing 4a can be closed on the top side by a housing cover 4b and on the bottom side by a housing base 4c, so that it is pneumatically sealed from the environment ( Fig. 5).

[0029] In the illustrated embodiment, the tank connection 6a and the filter connection 6b are fluidically connected or connectable to one another via a venting channel 8, which comprises a tank-side venting channel 8a and a filter-side venting channel 8b. A main venting valve 10 is arranged in the venting channel 8, which closes the venting channel 8 in a closed position and opens it in a released position.

[0030] The valve unit 2a further comprises a pilot valve 12 for opening the main vent valve 10, wherein the pilot valve 12 is fluidically connected or connectable on the one hand to a pressure chamber 14 of the main vent valve 10 and on the other hand to an overflow region 16. For this purpose, an inner wall 20 is formed in the housing 4, which has an opening 22 in which the pilot valve (12) is arranged. In the exemplary embodiment shown, the overflow region 16 fluidically connects the tank connection 6a or a tank-side vent channel 8a and the filter connection 6b or a filter-side vent channel 8b. In the present case, the pilot valve 12 is an on / off valve with an actuator, for example an SMA valve.

[0031] In the embodiment according to Fig. 1A, the valve unit 2a comprises three check valves which are arranged according to the invention as described below.

[0032] An inner wall 20a is formed in the housing 4, which has an opening 22a, via which the tank connection 6a or the tank-side venting channel 8a is fluidically connected to the pressure chamber 14 of the main venting valve 10. A tank-pressure chamber check valve 18a is arranged in this opening 22a and is thus fluidically connected, on the one hand, to the tank connection 6a or the tank-side venting channel 8a and, on the other hand, to the pressure chamber 14 of the main venting valve 10. In this case, the opening 22a initially opens into a tank-side fluid channel or fluid region 30a, which in turn opens into the tank-side venting channel 8a.

[0033] Furthermore, an inner wall 20c is formed in the housing 4, which has an opening 22c, via which the overflow area 16 is fluidically connected to the tank connection 6a or the tank-side venting channel 8a. An overflow area tank check valve 18c is arranged in this opening 22c and is thus fluidically connected, on the one hand, to the overflow area 16 and, on the other hand, to the tank connection 6a or the tank-side venting channel 8a. In this case, the opening 22c initially opens into the tank-side fluid channel or fluid area 30a, which in turn opens into the tank-side venting channel 8a.

[0034] Furthermore, an inner wall 20d is formed in the housing 4, which has an opening 22d, via which, in the present case, the overflow area 16 is fluidically connected to the filter connection 6b or the filter-side venting channel 8b. An overflow area filter check valve 18d is arranged in this opening 22d and is thus fluidically connected, on the one hand, to the overflow area 16 and, on the other hand, to the filter connection 6b or the filter-side venting channel 8b. In the present case, the opening 22d initially opens into the filter-side fluid channel or fluid area 30b, which in turn opens into the filter-side venting channel 8b.

[0035] In the non-inventive embodiment according to Fig. 1B, the valve unit 2a comprises a further check valve, thus comprising a total of four. For this purpose, an inner wall 20b is further formed in the housing 4, which has an opening 22b, via which, in the present case, the pressure chamber 14 of the main venting valve 10 is fluidically connected to the filter connection 6b or the filter-side venting channel 8b. A filter-pressure chamber check valve 18b is arranged in this opening 22b and is thus fluidically connected, on the one hand, to the pressure chamber 14 of the main venting valve 10 and, on the other hand, to the filter connection 6b or the filter-side venting channel 8b. In the present case, the opening 22b initially opens into a filter-side fluid channel or fluid region 30b, which in turn opens into the filter-side venting channel 8b.

[0036] To open and close the vent channel 8, the main vent valve 10 comprises a valve element, which is designed as a valve diaphragm 24 and, in this case, is circular. The valve diaphragm 24 has a pressure side 24a facing the pressure chamber 14 of the main vent valve 10 and a flow side 24b facing the filter connection 6b or the filter-side vent channel 8b. The flow side 24b of the valve diaphragm 24 closes the vent channel 8 in the closed position and opens it in the release position. A prestressing element 26 arranged in the pressure chamber 14 of the main vent valve 10 exerts a force on the pressure side 24a of the valve diaphragm 24. The main vent valve 10 comprises a valve diaphragm 24 as a valve element, which is designed in this case circular.In an edge region, the valve membrane 24 has a circumferential U-shaped section that engages a U-shaped sealing seat, also circular, formed by the housing 4 of the valve unit 2a. An annular outer portion of the flow side 24b borders the tank-side vent channel 8a, and an inner portion of the flow side 24b borders the filter-side vent channel 8b.

[0037] The basic function of the main vent valve 10 will be explained in more detail below. When refueling the fuel tank, volume flows of greater than 40 l / min are expected, whereby the pressure in the fuel tank must be kept low so that the incoming fuel in the filler pipe does not rise prematurely and cause the fuel nozzle to shut off. In this case, this is achieved by the main vent valve 10, which is designed as a pilot-operated diaphragm valve. If the pressure in the fuel tank increases, i.e. if an excess pressure develops there compared to atmospheric pressure, the fluid (gas) flows from the fuel tank, possibly via a vent line, via the tank connection 6a into the vent channel 8, more precisely the tank-side vent channel 8a. The valve diaphragm 24 is closed, i.e. the fluid cannot flow further to the filter connection 6b or to the activated carbon filter.The fluid flows into the pressure chamber 14 of the main vent valve 10 via the opening 22a and the open tank pressure chamber check valve 18a. If - not according to the invention - a filter pressure chamber check valve 18b is provided (. Fig. 1B), this valve is closed during this time, as is the pilot valve 12. Therefore, an excess pressure compared to atmospheric pressure also builds up in the pressure chamber 14. The valve membrane 24 is therefore pressed against an opening 28 of the filter-side main vent channel 8b; the valve element is thus in its closed position, and thus the main vent valve 10 is closed. No fluid can flow from the fuel tank through the vent channel 8 to the filter connection 6b and into the activated carbon filter.

[0038] Overpressure in the fuel tank can also occur when the fuel tank is closed, for example due to heating.

[0039] In order for fluid to flow from the fuel tank through the vent channel 8 into the activated carbon filter and for the excess pressure in the fuel tank to be reduced, the main vent valve 10 must be opened. To do this, the pressure in the pressure chamber 14 and thus on the pressure side 24a of the valve diaphragm 24 must be reduced to such an extent that the valve diaphragm 24 lifts off the opening 28 of the filter-side vent channel 8b due to the fluid pressure acting on its flow side 24b in the area of the tank-side vent channel 8a, the valve element thus moves into its release position and thereby opens the main vent valve 10 and releases the vent channel 8. This pressure reduction in the pressure chamber 14 occurs by opening the pilot valve 12. This allows fluid to flow from the pressure chamber 14 to the activated carbon filter.Since the tank pressure chamber check valve 18a is still open, fluid continues to flow from the fuel tank into the pressure chamber 14, but this inflowing volume flow of the fluid is significantly smaller than the outflowing volume flow through the pilot valve 12, the overflow area 16, the overflow area filter check valve 18d, the filter-side fluid channel 30b and the filter-side venting channel 8b to the activated carbon filter, since the flow diameter of the first opening 22a with the tank pressure chamber check valve 18a is significantly smaller than the flow diameter of the open pilot valve 12, the fluid can initially collect in the overflow area 16 and from there flows via the overflow area filter check valve 18d into the filter-side venting channel 8b.To avoid limiting the pilot valve 12 by the overflow area filter check valve 18d, via which the fluid is discharged from the overflow area 16, the flow diameter of the fourth opening 22d is larger than the flow diameter of the first opening 22a. Thus, the pressure in the pressure chamber 14 is reduced by opening the pilot valve 12, the main vent valve 10 opens, and the vent channel 8 is released for the fluid flow from the fuel tank to the activated carbon filter and thus for the pressure reduction in the fuel tank. The fluid can thus flow from the tank-side vent channel 8a through the main vent valve 10 into the filter-side vent channel 8b, which is shown in FIG. Fig. 1A, Fig. 1B is indicated by arrows with a solid line.

[0040] In the event of negative pressure in the fuel tank, which can arise, for example, due to cooling, pressure equalization can also be controlled via the main vent valve 10. If the pressure in the fuel tank drops, i.e., a negative pressure develops there compared to atmospheric pressure, fluid (gas or air) flows via the activated carbon filter, possibly a vent line, the filter connection 6b into the vent channel 8, more precisely the filter-side vent channel 8b. The valve membrane 24 is closed, i.e., the fluid cannot flow further to the fuel tank. If - not according to the invention - a filter pressure chamber check valve 18b is present ( Fig. 1B), the fluid flows via the filter-side fluid channel 30b, the second opening 22b, and the open filter pressure chamber check valve 18b into the pressure chamber 14 of the main venting valve 10. The tank pressure chamber check valve 18a is closed, as is the pilot valve 12. Therefore, the pressure in the pressure chamber 14 is essentially atmospheric pressure and thus a higher pressure than in the tank-side venting channel 8a and thus in the area of the flow side 24b of the valve diaphragm 24 that borders the tank-side venting channel 8a. The valve diaphragm 24 is therefore pressed against the opening 28 of the filter-side main venting channel 8b; the valve element is thus in its closed position, and thus the main venting valve 10 is closed. No fluid can flow from the activated carbon filter through the venting channel 10 into the fuel tank. The overflow area filter check valve 18d prevents pressure equalization with the environment.

[0041] If there is no filter pressure chamber check valve 18b ( Fig. 1A), no fluid flows into the pressure chamber 14, so that a previously enclosed fluid volume and existing pressure conditions are maintained within the pressure chamber 14.

[0042] In order for fluid to flow from the activated carbon filter through the venting channel 10 into the fuel tank and for the negative pressure in the fuel tank to be reduced, the main venting valve 10 must be opened. To do this, the pressure in the pressure chamber 14 and thus on the pressure side 24a of the valve diaphragm 24 must be reduced to such an extent that the valve diaphragm 24 lifts off the opening 28 of the filter-side venting channel 8b due to the fluid pressure (essentially atmospheric pressure) acting on its flow side 24b in the area of the filter-side venting channel 8b. The valve element thus moves into its release position, thereby opening the main venting valve 10 and releasing the venting channel 8. The pressure reduction in the pressure chamber 14 is in turn achieved by opening the pilot valve 12.This allows fluid to flow from the pressure chamber via the pilot valve 12, the overflow area 16, and the overflow area tank check valve 18c into the fuel tank (where negative pressure prevails). Since the filter pressure chamber check valve 18b—if present (not according to the invention)—remains open, fluid continues to flow from the activated carbon filter into the pressure chamber 14. However, this inflowing volume flow of fluid is significantly smaller than the outflowing volume flow toward the fuel tank, since the flow diameter of the opening 22b with the filter pressure chamber check valve 18b (not according to the invention) is significantly smaller than the flow diameter of the open pilot valve 12.To avoid limiting the pilot valve 12 by the overflow area tank check valve 18c, via which the fluid is discharged from the overflow area 16, the flow diameter of the third opening 22c is larger than the flow diameter of the second opening 22b. Thus, the pressure in the pressure chamber 14 is reduced by opening the pilot valve 12, the main vent valve 10 opens, and the vent channel 8 is released for the fluid flow from the activated carbon filter to the fuel tank and thus for the pressure buildup in the fuel tank. The fluid can thus flow from the filter-side vent channel 8b through the main vent valve 10 into the tank-side vent channel 8a, which is shown in FIG. Fig. 1A, Fig. 1B is indicated by dashed arrows.

[0043] In the embodiments shown below, which are not according to the invention, valve units are shown, each with four check valves 18a to 18d and a housing comprising a filler pipe connection 6c and a filler pipe-side vent channel 8c. It is understood that each of the embodiments shown below can also be designed with only three check valves and / or without a filler pipe connection 6c or a filler pipe-side vent channel 8c.

[0044] Fig. 2 shows a valve unit 2b according to a third embodiment not according to the invention in a schematic representation. Fig. 5 to 9, the valve unit 2b is shown in a concrete embodiment merely by way of example. The components described above for the valve unit 2a (as well as the valve units 2c, 2d described below) and which correspond to the valve unit 2b thus correspond to the components shown in the Fig. 5 to 9. Therefore, only differences compared to valve unit 2a are described below, otherwise both with regard to structure and function, reference should be made to the above Fig. 1A, Fig. 1B. The valve unit 2b comprises a bypass valve 32, which is fluidically connected on the one hand to the tank connection 6a or the tank-side venting channel 8a, and on the other hand to the filter connection 6b or the filter-side venting channel 8b. The bypass valve 32 is designed here as a control valve with an actuator, for example, as an SMA valve, and allows more precise control of the pressure in the fuel tank during vehicle operation. The bypass valve 32 is arranged in an opening 34a of an inner wall 36a of the housing 4, which separates the tank-side venting channel 8a from the filter-side venting channel 8b.

[0045] The valve unit 2b further comprises a recirculation valve 38, which is fluidically connected on the one hand to the tank connection 6a or the tank-side venting channel 8a, and on the other hand to the filler pipe connection 6c or the filler pipe-side venting channel 8c. The recirculation valve 38 is designed here as a control valve with an actuator, for example, as an EAP valve, and allows precise control of the recirculation flow during refueling. The recirculation valve 38 is arranged in an opening 34b of an inner wall 36b of the housing 4, which separates the tank-side venting channel 8a from the filler pipe-side venting channel 8c.

[0046] Further openings 34c, 34d are formed in the inner wall 36a, in which an overpressure protection valve 40 and a vacuum protection valve 42 are arranged, each fluidically connecting the tank connection 6a and the tank-side venting channel 8a, respectively, with the filter connection 6b and the filter-side venting channel 8b, respectively. The overpressure protection valve 40 and the vacuum protection valve 42 are each designed as a mechanical valve.

[0047] Fig. 3 shows a valve unit 2c according to a fourth embodiment, not according to the invention, in a schematic representation. The valve unit 2c comprises a bypass valve 44, which is fluidically connected on the one hand to the tank connection 6a or the tank-side venting channel 8a and on the other hand to the filter connection 6b or the filter-side venting channel 8b as well as the filler pipe connection 6c or the filler pipe-side venting channel 8c. For this purpose, the bypass valve 44 initially opens into a collecting chamber 46. A switching valve 48 is arranged in the collecting chamber 46, which, depending on the control, allows a fluid flow into the filter-side venting channel 8b or the filler pipe-side venting channel 8c. The bypass valve 44 is designed here as a control valve with an actuator, for example as an SMA valve.The bypass valve 44 is arranged in an opening 50 of an inner wall 52 of the housing 4, which separates the tank-side venting channel 8a from the collecting chamber 46, and the switching valve 48 is arranged both in an opening 34a of the inner wall 36a and in an opening 34b of the inner wall 36b. The collecting chamber 46 offers the advantage that only the upstream bypass valve 44 has a control characteristic and the switching valve 48 functions purely as a 3 / 2-way valve. Thus, only the bypass valve 44 needs to be able to implement intermediate positions of the actuator. Furthermore, with regard to both design and function, reference should be made to the above. Fig. 1 and Fig. 2.

[0048] Fig. 4 shows a valve unit 2d according to a fifth embodiment, not according to the invention, in a schematic representation. The valve unit 2d comprises a first bypass valve 54a, which is fluidically connected on the one hand to the tank connection 6a or the tank-side venting channel 8a, and on the other hand to the collecting chamber 46. A second bypass valve 54b opens from the collecting chamber 46 into the filter-side venting channel 8b. Furthermore, a recirculation valve 56 opens from the collecting chamber 46 into the filler-pipe-side venting channel 8c. The bypass valve 54a is designed as a control valve with an actuator, for example, as an SMA valve. The bypass valve 54b and the recirculation valve 56 are on / off valves, which can also have SMA actuators, for example.The first bypass valve 54a is arranged in an opening 50 of an inner wall 52 of the housing 4 separating the tank-side venting channel 8a from the collecting space 46, the second bypass valve 54b is arranged in an opening 34a of an inner wall 36a of the housing 4 separating the collecting space 46 from the filter-side venting channel 8b, and the recirculation valve 56 is arranged in an opening 34b of an inner wall 36b of the housing 4 separating the collecting space 46 from the filler pipe-side venting channel 8c. Furthermore, with regard to both structure and function, reference is made to the above. Fig. 1A, Fig. 1B, Fig. 2 and Fig. 3. List of reference symbols 2a, 2b, 2c, 2d valve unit 4 housings 4a Intermediate housing 4b Housing cover 4c Case back 6a tank connection 6b Filter connection 6c Filler pipe connection 8 Ventilation duct 8a tank-side vent duct 8b filter-side ventilation duct 8c Filler pipe side vent channel 10 Main vent valve 12 pilot valve 14 Printing room 16 Overflow area 18a Tank pressure chamber check valve 18b Filter pressure chamber check valve (not according to the invention) 18c Overflow tank check valve 18d Overflow area filter check valve 20, 20a, 20b, 20c, 20d inner wall 22, 22a, 22b, 22c, 22d opening 24 valve membrane 24a Print page 24b Flow side 26 Preload element 28 Opening of the ventilation duct 30a first fluid channel 30b second fluid channel 32 Bypass valve 34a, 34b, 34c, 34d opening 36a, 36b inner wall 38 Recirculation valve 40 Overpressure protection valve 42 Vacuum protection valve 44 Bypass valve 46 Assembly room 48 changeover valve 50 opening 52 interior wall 54a, 54b bypass valve 56 Recirculation valve

Claims

[1] Valve unit (2a, 2b, 2c, 2d) for a fuel tank, a) comprising a housing (4), a1) with a tank connection (6a) for connecting the valve unit (2) to the fuel tank and a2) with a filter connection (6b) for connecting the valve unit (2) to an activated carbon filter, b) comprising a venting channel (8), wherein the tank connection (6a) and the filter connection (6b) are fluidically connected or connectable via the venting channel (8), and wherein a main venting valve (10) with a valve element is arranged in the venting channel (8), which closes the venting channel (8) in a closed position and releases it in a release position, c) comprising a pilot valve (12) for opening the main venting valve (10), wherein the pilot valve (12) is or can be fluidically connected to a pressure chamber (14) of the main venting valve (10) on the one hand and to an overflow area (16) on the other hand, wherein the overflow area (16) fluidically connects or can be fluidically connected to the tank connection (6a) or a tank-side venting channel (8a) and the filter connection (6b) or a filter-side venting channel (8b), d) comprising exactly three check valves, where d1) a tank pressure chamber check valve (18a) is fluidically connected or connectable on the one hand to the tank connection (6a) or the tank-side venting channel (8a) and on the other hand to the pressure chamber (14) of the main venting valve (10), d2) an overflow area tank check valve (18c) is fluidically connected or connectable on the one hand to the overflow area (16) and on the other hand to the tank connection (6a) or the tank-side venting channel (8a), and d3) an overflow area filter check valve (18d) is or can be fluidically connected on the one hand to the overflow area (16) and on the other hand to the filter connection (6b) or the filter-side venting channel (8b). [2] Valve unit (2a, 2b, 2c, 2d) according to claim 1, wherein the housing (4) comprises a filler pipe connection (6c) for connecting the valve unit (2) to a filler pipe of the fuel tank. [3] Valve unit (2a, 2b, 2c, 2d) according to claim 1 or 2, wherein the valve element of the main vent valve (10) is designed as a valve membrane (24), wherein - the valve membrane (24) has a pressure side (24a) facing the pressure chamber (14) of the main venting valve (10) and a flow side (24b) facing the tank connection (6a) or the tank-side venting channel (8a), the filter connection (6b) or the filter-side venting channel (8b), and wherein - the flow side (24b) of the valve membrane (24) closes the venting channel (8) in the closed position of the valve element and opens the venting channel (8) in the release position of the valve element, and wherein - a prestressing element (26) arranged in the pressure chamber (14) of the main vent valve (12) exerts a force on the pressure side (24a) of the valve membrane (24). [4] Valve unit (2a, 2b, 2c, 2d) according to one of the preceding claims, comprising at least one bypass valve (32, 44, 54a, 54b) which is or can be fluidically connected to the tank connection (6a) or the tank-side venting channel (8a) on the one hand and to the filter connection (6b) or the filter-side venting channel (8b) on the other hand. [5] Valve unit (2a, 2b, 2c, 2d) according to claim 2 and according to one of claims 3 or 4, comprising at least one recirculation valve (38, 56) which is or can be fluidically connected on the one hand to the tank connection (6a) or the tank-side venting channel (8a) and on the other hand to the filler pipe connection (6c) or a filler pipe-side venting channel (8c). [6] Valve unit (2a, 2b, 2c, 2d) according to one of the preceding claims, comprising at least one overpressure protection valve (40) which is or can be fluidically connected on the one hand to the tank connection (6a) or the tank-side venting channel (8a) and on the other hand to the filter connection (6b) or the filter-side venting channel (8b). [7] Valve unit (2a, 2b, 2c, 2d) according to one of the preceding claims, comprising at least one vacuum protection valve (42) which is or can be fluidically connected on the one hand to the tank connection (6a) or the tank-side venting channel (8a) and on the other hand to the filter connection (6b) or the filter-side venting channel (8b). [8] Valve unit (2a, 2b, 2c, 2d) according to one of the preceding claims, wherein the housing (4) forms one or more inner walls (20, 20a, 20b, 20c, 20d, 36a, 36b, 52) which delimit the pressure chamber (14), the overflow area (16), the tank-side venting channel (8a) and / or the filter-side venting channel (8b) from one another, and wherein the pilot valve (12), the tank pressure chamber check valve (18a), the overflow area tank check valve (18c) and / or the overflow area filter check valve (18d) are each arranged in an opening (22, 22a, 22c, 22d) formed in the inner wall or the inner walls (20, 20a, 20c). [9] Valve unit (2a, 2b, 2c, 2d) according to claim 4 and according to claim 5 and according to one of claims 6 to 8, wherein the housing (4) forms one or more inner walls (20, 20a, 20b, 20c, 20d, 36a, 36b, 52) which delimit the pressure chamber (14), the overflow area (16), the tank-side venting channel (8a), the filter-side venting channel (8b) and / or the filler pipe-side venting channel (8c) from one another, and wherein the at least one bypass valve (32, 44, 54a, 54b) is arranged in an opening (34a, 34b, 50) formed in the inner wall or the inner walls (36a, 36b, 52). [10] Valve unit (2a, 2b, 2c, 2d) according to claim 5 and according to one of claims 6 to 9, wherein the housing (4) forms one or more inner walls (20, 20a, 20b, 20c, 20d, 36a, 36b, 52) which delimit the pressure chamber (14), the overflow area (16), the tank-side venting channel (8a), the filter-side venting channel (8b) and / or the filler pipe-side venting channel (8c) from one another, and wherein the at least one recirculation valve (38, 56) is arranged in an opening (34b) formed in the inner wall or the inner walls (36b). [11] Valve unit (2a, 2b, 2c, 2d) according to claim 5 and according to claim 6 and according to one of claims 7 to 10, wherein the housing (4) forms one or more inner walls (20, 20a, 20b, 20c, 20d, 36a, 36b, 52) which delimit the pressure chamber (14), the overflow area (16), the tank-side venting channel (8a), the filter-side venting channel (8b) and / or the filler pipe-side venting channel (8c) from one another, and wherein the overpressure protection valve (40) is arranged in an opening (34c) formed in the inner wall or the inner walls (36a). [12] Valve unit (2a, 2b, 2c, 2d) according to claim 5 and according to claim 7 and according to one of claims 8 to 11, wherein the housing (4) forms one or more inner walls (20, 20a, 20b, 20c, 20d, 36a, 36b, 52) which delimit the pressure chamber (14), the overflow area (16), the tank-side venting channel (8a), the filter-side venting channel (8b) and / or the filler pipe-side venting channel (8c) from one another, and wherein the vacuum protection valve (42) is arranged in an opening (34d) formed in the inner wall or the inner walls (36a). [13] Valve unit (2a, 2b, 2c, 2d) according to one of the preceding claims, wherein the pilot valve (12) is an SMA valve or an EAP valve or a solenoid valve or a pneumatic valve. [14] Valve unit (2a, 2b, 2c, 2d) according to claim 4 and according to one of claims 5 to 13, wherein the at least one bypass valve (32, 44, 54a, 54b) is an SMA valve or an EAP valve or a solenoid valve or a pneumatic valve. [15] Valve unit (2a, 2b, 2c, 2d) according to claim 5 and according to one of claims 6 to 14, wherein the at least one recirculation valve (38, 56) is an SMA valve or an EAP valve or a solenoid valve or a pneumatic valve. [16] Valve unit (2a, 2b, 2c, 2d) according to one of the preceding claims for the controlled and / or regulated discharge or introduction of a fluid from or into the fuel tank. [17] Valve unit (2a, 2b, 2c, 2d) according to claim 16 for the controlled and / or regulated discharge or introduction of gas or air or air enriched or saturated with hydrocarbons from or into the fuel tank.

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