Wheel valve for a tyre pressure control system

Abstract

The present invention relates to a wheel valve for a tyre pressure control system, comprising: a valve housing with a fluid inlet and an inflation opening, a deflation piston arranged in the valve housing, which defines an inflation passage between the fluid inlet and the inflation opening, a first pretension device configured to bias the deflation piston into a closed position, an inflation piston arranged in the inflation passage, a second pretension device configured to bias the inflation piston into a closed position against an inflation seat provided on the deflation piston, characterized in that the valve further comprises: a deflation opening, an exhaust port, and a deflation passage between the deflation opening and the exhaust port, wherein the deflation piston, in its closed position, closes the deflation passage between the deflation opening and the exhaust port.

Description

[0001] Title: Wheel valve for a tyre pressure control system

[0002] Field of the invention

[0003] The present invention relates to a wheel valve for a tyre pressure control system for mounting in a rim of a vehicle wheel and for inflating or deflating a tyre mounted on the rim by means of a pressurized fluid. The present invention further relates to a tyre pressure control system for controlling tyre pressure and to a method of inflating or deflating a tyre.

[0004] State of the art

[0005] Tyre pressure control systems are for example known for agricultural vehicles to inflate or deflate their tyres while driving, depending on the subsoil the vehicle is driving on. To realise this, there must be a minimum of one airline per wheel connecting a pressurised fluid from a source of pressurized fluid attached the body of the vehicle towards the tyres that are arranged on the vehicle’s wheels. At the wheels, valves are used to selectively inflate or deflate the tyre, by respectively increasing or decreasing the air pressure in the tyre.

[0006] Many of the known wheel valves rely on multiple feed lines from the vehicle. One feedline is then configured to supply the pressurized air for inflation, whereas another feedline may selectively control opening or closing of the wheel valve based on a control input of pressurized air. Optionally, a third line is utilized to discharge air out of the wheel valve during deflation of the tyres.

[0007] The known multi-line systems are relatively complicated, since multiple feedlines need to be supplied from a stationary part of the vehicle, e.g. a source of pressurized air, towards the rotary wheels. These systems thus require rotary transmission joints that are suitable for multiple feedlines.

[0008] As a solution, wheel valves are known that rely on a single feedline. The state of these wheel valves, e.g. inflating, deflating or maintaining pressure in the tyre, can be set by supplying the pressurized fluid at different pressure levels, more specifically different ranges of pressure levels. An example of such a valve is disclosed in US 2023 / 026449 A1. This known wheel valve comprises a singe fluid inlet and a wheel opening at an opposed end, projecting into the interior of the tyre. When no overpressure is supplied at the fluid inlet, the pressure in the tyre is maintained. When a relatively low overpressure is supplied, a small inflation piston will open against a small spring pretension to inflate the tyre. When a relatively large overpressure is supplied, a large deflation piston will open against a large spring pretension to deflate the tyre. This known valve does have the drawback that the valve inflates and deflates the tyre through the valve in a back and forth manner. During deflation, possible dirt, debris or other contaminations could thus pass back through the valve and could give rise to blocking of the pistons and thus to malfunctioning of the valve.

[0009] Object of the invention

[0010] It is therefore an object of the present invention to provide a wheel valve for a tyre pressure control system that is less prone to malfunctioning, thus offering an improved reliability, or at least to provide an alternative wheel valve.

[0011] Detailed description

[0012] According to a first aspect, the present invention provides a wheel valve for a tyre pressure control system to be associated with, in particular for mounting in, a rim of a vehicle wheel and for inflating or deflating a tyre mounted on the rim by means of a pressurized fluid, the valve comprising: a valve housing, for example configured to be mounted through the rim, the valve housing comprising: a fluid inlet that is connectable to a source of pressurized fluid, and an inflation opening, configured to be fluidly connected to an interior of the tyre mounted on the rim, in particular a wheel inflation opening that is configured to project into the interior of the tyre, a deflation piston arranged in the valve housing, which comprises a deflation piston surface and which defines an inflation passage extending between the fluid inlet and the wheel inflation opening, a first pretension device configured to exert a first pretension force onto the deflation piston relative to the valve housing, in order to bias the deflation piston towards the fluid inlet into a closed position, an inflation piston arranged in the inflation passage, which comprises an inflation piston surface,

[0013] - a second pretension device configured to exert a second pretension force onto the inflation piston relative to the deflation piston, in order to bias the inflation piston towards the fluid inlet into a closed position against an inflation seat provided on the deflation piston, wherein, optionally, a surface area of the inflation piston surface is smaller than a surface area of the deflation piston surface and / or wherein the second pretension force is smaller than the first pretension force, characterized in that, the valve further comprises: a deflation opening, which is configured to be fluidly connected to the interior of the tyre and which may be separate and located at a distance from the inflation opening, in particular a wheel deflation opening that is configured to project into the interior of the tyre, an exhaust port, which projects into the ambient for discharging fluid out of the tyre to deflate the tyre, and a deflation passage, which extends between the deflation opening and the exhaust port and which is separate from the inflation passage, and wherein the deflation piston, in its closed position, closes the deflation passage between the deflation opening and the exhaust port.

[0014] It is noted that the features of the inflation opening and deflation opening are also respectively referred to with wheel inflation opening and wheel deflation opening throughout the present patent application. These terms are interpreted as being equivalent to each other.

[0015] The present wheel valve comprises two passages through which the fluid can be guided. An inflation passage is used to guide pressurized fluid from the fluid inlet to the wheel inflation opening, thereby allowing inflation of the tyre by increasing the pressure level in the interior of the tyre. A separate deflation passage extends between the wheel deflation opening, which may be provided separate from the wheel inflation opening, and the exhaust port. The deflation passage is used to guide fluid out of the interior of the tyre during deflation thereof. This allows the tyre to be deflated through a separate passage and will prevent that possible contaminations can accumulate in the inflation passage during deflation, thus avoiding the risk of blockage of the inflation passage and the inflation piston arranged therein.

[0016] According to the present invention, the wheel valve is configured to be connected to a single feedline for receiving pressurized fluid from the source of pressurized fluid. The wheel valve may further be free of other fluid inlets.

[0017] The valve comprises the valve housing, which is configured to be mounted in an aperture provided in a rim of the vehicle, for example being fastened therein by means of a threaded connection. The valve housing may be a single one-piece housing, but may also be assembled of multiple pieces that together form the valve housing. Part of the valve housing may thereby project into the interior of the tyre that is mounted on the rim, whereas another part of the valve housing is accessible from outside the tyre. In particular, the wheel inflation opening in the valve housing is intended to project into the interior of the tyre, whereas the fluid inlet is intended to be accessible from outside the wheel. It is noted that the present wheel valve may comprise a single or multiple of the wheel inflation openings, for example depending on a desired flow rate of the pressurized fluid during inflation of the tyre.

[0018] The valve housing may comprise a hollow interior in between the fluid inlet and the wheel inflation opening, in which interior the deflation piston can be arranged. The deflation piston is thereby provided in between the fluid inlet and the wheel inflation opening, in order to close off a passage, e.g. the inflation passage, between the fluid inlet and the wheel inflation opening. According to the present invention, this passage is closed off irrespective of the position of the deflation piston, since the deflation piston is only configured to be operated for deflation of the tyre, which is carried out through the deflation passage and for which the inflation passage has no role.

[0019] The deflation piston comprises the deflation piston surface, which faces towards the fluid inlet. The pressurized fluid supplied into the valve at the fluid inlet thus acts against the piston surface of the deflation piston. The pressure level of the pressurized fluid at the piston surface of the deflation piston may thereby determine the position or state in which the deflation piston is arranged. The deflation piston is arranged in the valve housing and is thus configured to move in relation to the valve housing when moving between its closed position and an opened position.

[0020] The first pretension device is provided, for example embodied as a first compression spring, to move the deflation piston in its closed position. The first pretension device is aligned to act on the deflation piston in a direction towards the fluid inlet, so that the deflation piston is moved towards the fluid inlet under influence of the biasing first pretension force from the first pretension device. The net force acting on the deflation piston may thus be formed by the pressurized fluid acting on the piston surface of the deflation piston on the one hand and the first pretension force by the first pretension device on the other hand. Optionally, a further contribution may be provided by a pressure level of the fluid in the interior of the tyre acting on the deflation piston, i.e. on a counter surface opposite to the piston surface thereof, thus acting alongside the first pretension device towards the fluid inlet.

[0021] The deflation piston comprises the inflation passage through which the pressurized fluid is passed upon inflation of the tyre. The inflation passage extends through the deflation piston, for example along a centreline of the deflation piston. As such, the inflation passage does form a channel for the fluid between the fluid inlet and the wheel inflation opening, irrespective of the position of the deflation piston.

[0022] The inflation passage, in turn, can be selectively closed off by means of the inflation piston that is provided in the inflation passage. The inflation piston comprises, in a manner similar to the deflation piston, a piston surface that faces towards the fluid inlet. Any pressurized fluid at the fluid inlet, during use of the valve, thus acts against the piston surface of the inflation piston. This inflation piston is arranged in the deflation piston and is thus configured to move in relation to the deflation piston when moving between its closed position and an opened position.

[0023] The valve comprises a second pretension device, which acts against the inflation piston to bias the inflation piston towards the fluid inlet under influence of the second pretension force. The second pretension device may be a second compression spring, which is functionally arranged in between the inflation piston and the deflation piston, so that the second compression spring is configured to move the inflation piston in relation to the deflation piston. Any movement of the deflation piston relative to the housing may therefore not have any influence on the position of the inflation piston inside the deflation piston.

[0024] The deflation piston comprises the inflation seat inside the inflation passage, against which the inflation piston is pushed under influence of the second pretension device when the inflation piston is biased in the closed position. In this closed position, the inflation passage is closed off, thereby preventing passage of pressurized fluid from the fluid inlet towards the wheel inflation opening, and vice versa.

[0025] The second pretension device is aligned to act on the inflation piston in a direction towards the fluid inlet, so that the inflation piston is moved towards the fluid inlet under influence of the biasing second pretension force from the second pretension device. The net force acting on the inflation piston may thus be formed by the pressurized fluid acting on the piston surface of the inflation piston on the one hand and the second pretension force by the second pretension device on the other hand. Optionally, a further contribution may be provided by a pressure level of the fluid in the interior of the tyre acting on the inflation piston, i.e. on a counter surface opposite to the piston surface thereof, thus acting alongside the second pretension device towards the fluid inlet.

[0026] The working principle of the present valve is contributed by the mutual relationship between the piston surfaces of the deflation piston and of the inflation piston, as well as between the first pretension device and the second pretension device, in particular the pretension forces exerted therewith. These may be selected such that both the deflation piston and the inflation piston may be arranged in their closed positions when the pressure level at the fluid inlet is below an inflation pressure level. The inflation piston may be moved out of its closed position when the pressure level at the fluid inlet is above the inflation pressure level, but below a deflation pressure level, in order to allow fluid to pass from the fluid inlet towards the wheel inflation opening. Finally, the deflation piston may be moved out of its closed position when the pressure level at the fluid inlet is above the deflation pressure level, so that the tyre can be deflated through the deflation passage.

[0027] To this effect, the surface area of the inflation piston surface may be smaller than the surface area of the deflation piston surface. This may provide that a resulting force acting on the inflation piston, for a certain pressure level at the fluid inlet, may be smaller than a resulting force acting on the deflation piston.

[0028] In the closed position of the inflation piston and in the closed position of the deflation piston, the pressure level in the tyre, i.e. the tyre pressure, may also be present in the inflation passage, opposite to the piston surface that faces the fluid inlet. As such, the tyre pressure may contribute, together with the second pretension device, to bias the inflation piston in the closed position.

[0029] Likewise, the second pretension force may be selected smaller than the first pretension force, for example by embodying the first pretension device as a stronger compression spring compared to the second pretension device. This may enable that the second pretension force is overcome earlier than the first pretension force, so that the inflation piston is moved out of its closed position at a fluid inlet pressure level lower than the fluid inlet pressure level at which the deflation piston is moved out of its closed position.

[0030] The present valve further comprises the deflation passage, which is provided separate from the inflation passage. This allows the deflation of the tyre to be carried out through a passage different from the passage through which inflation takes place. The deflation passage extends between the wheel deflation opening and the exhaust port. With the deflation passage separate from the inflation passage, it may be provided that deflation will not influence the inflation passage, for example preventing that possible contaminations inside the tyre will end up in the inflation passage during deflation of the tyre

[0031] The wheel deflation opening may project into the interior of the tyre in a manner similar to the wheel inflation opening, albeit possibly at a different location. In this way, it may be prevented that possible contaminations inside the tyre will accumulate at the wheel inflation opening during deflation of the tyre. Instead, the contaminations may only reach the wheel deflation openings, where they are preferably filtered, to prevent them from reaching the deflation passage. For example, the wheel inflation opening may be provided as one or more openings at a head end of the valve housing that projects into the interior of the tyre. The wheel deflation opening may be formed by a plurality of wheel deflation openings that are located around the circumference of the portion of the valve housing projecting into the interior of the tyre.

[0032] The exhaust port is configured to discharge fluids out of the tyre into the ambient of the wheel during deflation. This allows the deflated fluid to bypass the inflation passage. As such, the exhaust port may be provided remote from the fluid inlet as well. For example, the fluid inlet may be provided as a single opening at a head end of the valve housing that projects outside the tyre. The exhaust port may be formed by a plurality of exhaust ports that are located around the circumference of the portion of the valve housing projecting outside the tyre.

[0033] The deflation passage may be defined in between the valve housing and the deflation piston, so that the fluid deflated from the tyre during deflation can be guided around the outside of the deflation piston. The deflation piston thereby forms the separation between the inflation passage and the deflation passage. The deflation passage may be formed by one or more passages around the outer surface of the deflation piston, for example a number of deflation passages corresponding to the number of wheel deflation openings and / or the number of exhaust ports. The multiple deflation passages may be spaced around an outer perimeter of the deflation piston.

[0034] In the closed position, the deflation piston closes the deflation passage between the wheel deflation opening and the exhaust port. As such, it can be prevented that the tyre is deflated, both when the inflation piston is closed, i.e. to maintain a pressure level in the tyre, and when the inflation piston is moved out of its closed position, i.e. during inflation of the tyre. The movement of the deflation piston will thus influence the deflation passage that surrounds the deflation piston, in order to allow or prevent pressurized fluid from passing through the deflation passage, i.e. in between the deflation piston and the valve housing.

[0035] In an embodiment, the deflation opening may be separate and located at a distance from the inflation opening. Alternatively, however, the inflation opening and the deflation opening may be combined as a common opening that is fluidly connectable to the inflation passage, the deflation passage and the interior of the tyre. In this situation, a single common opening or set of common openings may be provided in the valve housing. As such, the inflating and deflating will be performed through the common opening, whereby internally in the valve housing, the inflation passage and deflation passage are provided separate from each other.

[0036] During inflation, the deflation passage may remain closed according to this embodiment, so that pressurized fluid can only travel out of the inflation passage, through the common opening and towards the interior of the tyre. Similarly, during deflation, the inflation passage may remain closed according to this embodiment, so that pressurized fluid can only travel out of interior of the tyre, through the common opening and into the deflation passage.

[0037] In an embodiment, the valve housing comprises a deflation seat in the deflation passage, and the deflation piston, in its closed position, contacts the deflation seat to close the deflation passage. The deflation seat is thereby fixedly attached to the valve housing, inside the deflation passage. In its closed position, the deflation piston is forced against the deflation seat to close off the deflation passage. When moved out of the closed position, the deflation piston is moved relative to the valve housing, so that the deflation piston is moved away from the deflation seat in order to open the deflation passage.

[0038] The deflation seat may have an annular shape in the interior of the valve housing, so that it surrounds the deflation piston that is arranged in the valve housing. The deflation piston may have a corresponding annular surface at its outer perimeter, in order to seal against the deflation seat in its closed portion along its entire perimeter. In this way, the annular deflation seat may be able to seal multiple deflation passages that are spread around the perimeter of the deflation piston.

[0039] The deflation seat and / or the surface of the deflation piston configured to contact the deflation seat in the closed position of the deflation piston may be made of an elastomeric material, for example a polymeric or rubber material. The remainder of the valve housing and / or the deflation piston may be made of a metallic material. The contact between the elastomeric material and the metallic material may further improve the sealing between the deflation piston and the deflation seat.

[0040] In an embodiment, the deflation passage surrounds the deflation piston. The deflation passage may thereby have an annular shape, so that the deflation piston can be arranged centrally inside the deflation passage.

[0041] Additionally or alternatively, the deflation piston may surround the inflation passage. This surrounding may provide that the deflation piston delimits the inflation passage and the deflation passage and that the inflation passage and the deflation passage are separated from each other by the deflation piston.

[0042] In an embodiment, the valve comprises multiple of the wheel deflation openings and / or exhaust ports, which are spread over a perimeter of the valve housing. This embodiment may provide that multiple deflation passages are spread over the perimeter of the valve housing, by which it may be provided that an overall cross-sectional area of all deflation passages combined is relatively large. This may allow for desirable deflation of the tyre, for example allowing a desirably large deflation flow rate.

[0043] In an embodiment, the deflation piston and the inflation piston are arranged in their closed positions when a pressure level at the fluid inlet is below an inflation pressure level, in order to arrange the wheel valve in a pressure holding state for maintaining a pressure level in the tyre.

[0044] In the pressure holding state, both pistons are in their closed positions, so that no inflation or deflation of the tyre can take place. This implies that the pressure level inside the tyre in maintained.

[0045] The inflation pressure level may be a maximum pressure level, below which the valve is held in the pressure holding state. The inflation pressure level may be determined on the basis of the second pretension force by the second pretension device and the surface area of the inflation piston. Hence, the position of the inflation piston is determined by the balance between the pressure force resulting from the fluid pressure at the fluid inlet acting on the piston surface and the pretension force acting on the opposite side of the piston. Additionally, the inflation pressure level may be determined by the pressure level in the tyre, since that pressure may exert a counter force on the piston at a counter surface opposite to the surface facing the fluid inlet and acting alongside with the pretension device.

[0046] The inflation pressure level may be defined as the pressure level, e.g. pressure level difference over the inflation piston, at which the inflation piston is moved out of the closed position. If a pressure above the inflation pressure level is supplied at the fluid inlet, the inflation piston may be moved out of the closed position in order to inflate the tyre.

[0047] In an embodiment, the deflation piston is moved out of its closed position when a pressure level at the fluid inlet is above a deflation pressure level, in order to arrange the wheel valve in a deflation state for reducing the pressure level in the tyre, thereby allowing fluid to pass from the tyre to the ambient through the wheel valve, via the deflation opening, the deflation passage and the exhaust port.

[0048] In the deflation state, the deflation piston is moved out of its closed position. The inflation piston may be in the closed position or may be moved out of the closed position, but, preferably, the inflation passage is closed off to prevent deflation from taking place through the inflation passage and to prevent pressurized fluid at the fluid inlet from entering into the tyre. In this configuration, the deflation passage is opened by the deflation piston, which enables fluid to flow out of the interior of the tyre into the valve, through the wheel deflation openings. The wheel deflation openings may then further guide the fluid through the deflation passages and, finally, into the ambient of the valve, via the exhaust ports. With the fluid flowing out of the tyre, the pressure level in the tyre is lowered, therewith effecting deflation of the tyre.

[0049] The deflation pressure level may be a minimum pressure level, above which the valve is held in the deflation state. The deflation pressure level may be determined on the basis of the first pretension force by the first pretension device and the surface area of the deflation piston. Hence, the position of the deflation piston is determined by the balance between the pressure force resulting from the fluid pressure at the fluid inlet acting on the deflation piston surface and the first pretension force acting on the opposite side of the piston.

[0050] Additionally, the deflation pressure level may be determined by the pressure level in the tyre, since that pressure may exert a counter force on the deflation piston at a counter surface opposite to the surface facing the fluid inlet and acting alongside with the first pretension device.

[0051] The deflation pressure level may be defined as the pressure level, e.g. pressure level difference over the deflation piston, at which the deflation piston is moved out of the closed position. If a pressure above the deflation pressure level is supplied at the fluid inlet, the deflation piston may be moved out of the closed position in order to deflate the tyre. To this effect, the deflation pressure level may normally lie above the pressure level in the tyre, i.e. a momentaneous tyre pressure, to ensure that the deflation pressure level is large enough to move the deflation piston out of its closed position.

[0052] In an embodiment, the valve further comprises an exhaust closure element at the exhaust port, for preventing fluid and contaminants to flow into the deflation passage from outside the wheel valve. The exhaust closure element may also be embodied as a flexible closure element in front of the exhaust ports and may be opened in case the pressure level in the deflation passage is larger than the ambient pressure level, i.e. during deflation when a fluid flow is established out of the interior of the tyre through the deflation passage. The exhaust closure element may further be configured to close off the exhaust ports in the absence of such a pressure differential, to prevent a backflow of fluid and contaminants from the outside the wheel valve into the deflation passage.

[0053] In a further embodiment, the exhaust port may be provided concentrically around the inlet port. The exhaust closure element may thereby be provided as a flexible ring element to selectively close the exhaust port. The flexible ring element may be made from a polymeric material, such as a polyurethane material, to provide for a desirable balance between rigidity and flexibility.

[0054] In an embodiment, the valve further comprises an inflation passage closure, which is attached to the valve housing, e.g. forming part of the valve housing, and which is configured to close off the inflation passage when the deflation piston is moved out of its closed position. In the closed position of the deflation piston, the inflation passage closure may be spaced at a distance from the inflation passage, to enable a fluid flow through the inflation passage. This may be the case in the pressure holding state and the inflation state of the valve, in which states the deflation piston is in the closed position.

[0055] If the deflation piston is moved out of its closed position, i.e. when the valve is brought in the deflation state, the inflation passage closure will remain in place as it is attached to the valve housing. As a result of the movement of the deflation piston, the inflation passage closure will come to seal against the inflation passage, so that the inflation passage is closed off. This means that no fluids can pass through the inflation passage when the deflation piston is moved out of the closed position. As such, it can be prevented that fluid from the tyre, possibly containing contaminants, can flow into the inflation passage during deflation.

[0056] The inflation passage closure may provide that the inflation passage remains closed during deflation, even when the inflation piston is moved out of closed position as a result of the relatively high pressure level at the fluid inlet. Hence, the deflation pressure level is larger than the inflation pressure level, which implies that when the inflation piston is opened at the inflation pressure level, it will certainly be moved out of its closed position at the deflation pressure level as well. The inflation passage closure may form a safety, so that, even when the inflation piston is moved out of the closed position, no fluid at the deflation pressure level can enter the tyre through the inflation passage.

[0057] In a further embodiment, the inflation passage closure projects into the inflation passage when the deflation piston is moved out of its closed position, to seal off the inflation passage against the deflation piston. According to this embodiment, the inflation passage closure is arranged adjacent to the inflation passage, so that the inflation passage closure may be spaced at a distance from the inflation passage when the deflation piston is in the closed position, i.e. in the pressure holding state and the inflation state, and that the inflation passage moves against the inflation passage closure when the deflation piston is moved out of the closed position, i.e. in the deflation state of the valve.

[0058] In an embodiment, the valve housing further comprises a deflation piston guide, e.g. located adjacent the inflation passage closure, which is configured to guide movements of the deflation piston between its closed position and an opened position. The deflation piston guide may be located around at least a part of the perimeter of the deflation piston, in order to prevent the deflation piston from moving sideward, e.g. from moving in directions perpendicular to its direction of movement between its closed position and opened position. As such, the position of the deflation piston may be stabilized, which may increase reliability of the wheel valve.

[0059] In a further embodiment, the deflation piston guide comprises one or more apertures for guiding a fluid flow out of the inflation passage towards the inflation opening when the deflation piston is moved out of its closed position. These apertures may provide that the fluid is deflected sideways when departing from the inflation passage, which allows an end surface underneath the inflation passage to be closed, for example allowing the inflation passage closure to be located there.

[0060] When the deflation piston is not in its closed position, e.g. so that the inflation passage closure does not close off the inflation passage, the fluid from the inflation passage can flow through the apertures towards the inflation openings. The deflation piston guide may thereto for example be embodied as a number of guiding pins around the perimeter of the deflation piston between which the apertures are defined and which jointly guide the deflation piston. In an embodiment, the inflation piston is moved out of its closed position when a pressure level at the fluid inlet is above the inflation pressure level and below the deflation pressure level, in order to arrange the wheel valve in an inflation state for increasing the pressure level in the tyre, by allowing pressurized fluid to pass from the fluid inlet to the tyre through the wheel valve, via the inflation passage, the inflation piston and the inflation opening.

[0061] In the inflation state, the deflation piston is in its closed position and the inflation piston is moved out of its closed position, so that the fluid at the fluid inlet is allowed to flow into the tyre, through the inflation passage. As a result, the tyre is inflated and the pressure level inside the tyre will be increased. During inflation, the pressure level at the fluid inlet will lie in between the inflation pressure level and the deflation pressure level, which implies that the deflation piston will remain in the closed position. Accordingly, only the inflation piston will be opened, so that the fluid supplied at the fluid inlet can flow into the tyre.

[0062] The pressure level of the fluid supplied at the fluid inlet during inflation may lie at the desired pressure level for the tyre, i.e. an intended tyre pressure. This may provide that an equilibrium situation may be reached during inflation, namely when the pressure level in the tyre equals the pressure level at the fluid inlet. At that moment, no further fluid will flow into the tyre and the intended tyre pressure is reached. In such a configuration, the tyre pressure control system may operate in a feedforward manner, since it is no longer required to measure the tyre pressure to determine whether the tyre is sufficiently inflated.

[0063] However, the pressure level at the fluid inlet may also lie above the intended tyre pressure to increase the flow rate of the fluid entering the tyre. The tyre pressure control system may then further comprise a pressure sensor device in tyre, on the basis of which a feedback sensor signal can be provided to stop inflating as soon as the intended tyre pressure is reached.

[0064] In an embodiment, the inflation pressure level is equal to or larger than the second pretension force divided by the surface area of the inflation piston surface. The net resulting force on the inflation piston must thus be facing away from the fluid inlet to move the inflation piston out of the closed position. The inflation pressure level is thereby defined as the pressure level that is sufficient to overcome the second pretension force, when multiplied by the surface area of the inflation piston, and to move the inflation piston out of the closed position.

[0065] Additionally, the fluid pressure at the fluid inlet may also need to overcome a counter force of the fluid pressure in the tyre exerting a force on the inflation piston at a counter surface opposite to the inflation piston surface facing the fluid inlet, which acts alongside with the second pretension device and which thus influences the net force acting on the inflation piston. As such, the inflation pressure level may need to be equal to or larger than the sum of the second pretension force and the pressure level in the tyre multiplied by the area of the counter surface of the inflation piston, divided by the surface area of the inflation piston surface facing the fluid inlet.

[0066] In an embodiment, the deflation pressure level is equal to or larger than the first pretension force divided by the surface area of the deflation piston surface. The net resulting force on the deflation piston must thus be facing away from the fluid inlet to move the deflation piston out of the closed position. The deflation pressure level is thereby defined as the pressure level that is sufficient to overcome the first pretension force, when multiplied by the surface area of the deflation piston, and to move the deflation piston out of the closed position.

[0067] Additionally, the fluid pressure at the fluid inlet may also need to overcome a counter force of the fluid pressure in the tyre exerting a force on the deflation piston at a counter surface opposite to the deflation piston surface facing the fluid inlet, which acts alongside with the first pretension device and which thus influences the net force acting on the deflation piston. As such, the deflation pressure level may need to be equal to or larger than the sum of the first pretension force and the pressure level in the tyre multiplied by the area of the counter surface of the deflation piston, divided by the surface area of the deflation piston surface facing the fluid inlet.

[0068] In an embodiment, the valve further comprises a non-return valve at the inflation opening for preventing fluid to flow back from the interior of the tyre into the inflation passage. The non-return valve may further contribute in guiding the fluid through the deflation passage during deflation of the tyre, by which it may be prevented that possible contaminants in the tyre will flow into the inflation passage during deflation.

[0069] The non-return valve may be embodied as a flexible closure element in front of the wheel inflation openings, for example surrounding the inflation passage closure. The closure element may be opened in case the pressure level in the inflation passage is larger than the pressure level in the tyre, i.e. during inflation when a fluid flow is established into the interior of the tyre from the inflation passage. The closure element may further be configured to close off the wheel inflation openings in the absence of such a pressure differential, to prevent a backflow of fluid and contaminants from the tyre into the inflation passage.

[0070] However, the non-return valve not necessarily needs to be able to absorb a withstand a pressure difference over it, in case the pressure level in the tyre, i.e. the tyre pressure, is larger than the pressure level in the inflation passage. This may occur when the wheel valve is in the pressure holding state, with the inflation piston in its closed position. In the absence of a pressure difference over the non-return valve, the tyre pressure also acts on the inflation passage, opposite to the piston surface that faces the fluid inlet, wherein the tyre pressure contributes, together with the second pretension device, to bias the inflation piston in the closed position.

[0071] In an embodiment, the valve further comprises a filter element at the deflation opening for preventing contaminants from entering the deflation passage from the tyre. The filter element may be embodied as a sleeve element surrounding the portion of the valve housing that is located in the interior of the tyre, so that the filter element projects in front of all wheel deflation openings.

[0072] The filter element may be made of a sintered material, which may allow fluids, e.g. air, to pass from the interior of the tyre into the deflation passages, whereas possible dirt, debris or other contaminations can be captured by the filter element, in order to prevent those from entering the deflation passages.

[0073] The filter element may further serve to throttle the flow of fluid from the interior of the tyre towards the ambient, through the deflation passage, as it imposes another pressure drop on the fluid. In this ways, the deflation rate of the tyre can be tempered, in order to improve the controllability of deflation.

[0074] In a further embodiment, where the inflation opening and the deflation opening are combined as a common opening, the filter element may be provided at the common opening. As such, the placement of the filter element may beneficially serve a dual purpose, namely to filter contaminations when fluid flows out of the interior of the tyre towards the deflation passage, but also that the contaminations are blown out of the filter element when the tyre is inflated when pressurized fluid flows from the valve housing, through the filter element and towards the interior of the tyre.

[0075] In an embodiment, the valve housing is configured to be mounted through the rim and the inflation opening, e.g. a wheel inflation opening, and the deflation opening, e.g. wheel deflation opening, project into the interior of the tyre. According to this embodiment, the wheel valve actually projects into the interior of the tyre, so that the wheel inflation opening and the wheel deflation opening are in direct fluid communication with the interior of the tyre.

[0076] In an alternative embodiment, the valve housing is configured to be mounted remotely from the interior of the tyre and the wheel valve further comprises a wheel fluid line, extending from the inflation opening and the deflation opening towards the interior of the tyre. As such, the wheel valve may be located closer to the centre of the wheel, only requiring the wheel fluid line to extend towards the rim and the tyre. The fluid line may be conveniently connected to the rim in a manner similar to conventional tyre valves.

[0077] This embodiment may offer the benefit that the eccentricity of the wheel, and therefore its degree of imbalance, can be reduced. Furthermore, it may provide that the wheel valve is positioned at a location where it is less prone to damaging, i.e. away from the tyre.

[0078] In a further embodiment, the valve housing further comprises a cap member, which is connected to the wheel fluid line and which comprises a cap interior that faces the inflation opening and the deflation opening, in order to fluidly connect the inflation opening and the deflation opening with the wheel fluid line. The cap interior is therefore subjected to the same pressure level as the interior of the tyre, i.e. as a result of the fluid communication through the wheel fluid line, so that the valve, despite the valve housing being located away from the interior of the tyre, may still operate in a manner similar to when the inflation opening and the deflation opening directly project into the interior of the tyre. The cap member may thereby serve to surround all of the wheel deflation openings, e.g. around the perimeter of the valve housing, so that a large number of smaller deflation openings may be provided around a single inflation opening. As such, this embodiment of the wheel valve may also allow a number of exhaust ports spread around the perimeter of the valve housing.

[0079] In a further embodiment, for example in a wheel valve comprising multiple of the deflation openings and / or exhaust ports, spread over a perimeter of the valve housing, the cap member is an annular cap member, which surrounds all of the wheel deflation openings. The annular shape may allow the wheel fluid line to be located at one side of the annular cap member, wherein the annular cap member serves to assure a substantially constant pressure level at all of the wheel deflation openings.

[0080] The annular cap member may be attached to the other parts of the valve housing by means of a threaded connection. The annular cap member may include the flexible closure element, embodied as an annular elastic ring, located in a fluid path between the inflation opening and the wheel fluid line, in order to allow pressurized fluid to flow from the inflation opening towards the wheel fluid line and to inhibit a return flow of fluid from the wheel fluid line back into the inflation opening.

[0081] In an embodiment, e.g. in a wheel valve comprising the inflation passage closure, the cap member comprises the inflation passage closure. This may allow cap member and the inflation passage closure to be mounted to the rest of the valve housing as a unitary component, thereby improving the manufacturability of the wheel valve. In an alternative or additional embodiment, the cap member forms a seat for the first pretension device, so that the deflation is pretensioned by the first pretension device against the cap member. The first pretension device may thereby be provided around the inflation passage closure to secure a sideward position of the first pretension device vis-a-vis the cap member.

[0082] In an embodiment, the valve housing is configured to be mounted at a hub of the wheel, for example adjacent to a rotary transmission joint of the wheel. This may allow the wheel valve to be mounted adjacent to, or even integrated in a rotary fluid joint for the wheel. Such a rotary transmission joint, which is for example disclosed in NL 2036176, can be provided to transfer pressurized fluid from a stationary axle towards the rotary wheel. As such, existing vehicle wheels can be easily retrofitted with a tyre pressure control system, e.g. by simply replacing a conventional tyre valve with the current fluid line, therefore not requiring complicated modifications to the wheels.

[0083] According to a second aspect, the present invention provides a tyre pressure control system for controlling the tyre pressure in one or more vehicle wheels by inflating or deflating a tyre of the wheels, the system comprising: a source of pressurized fluid, configured to supply pressurized fluid, one or more wheel valves as disclosed herein, each wheel valve associated with, in particular mounted on a rim of a respective vehicle wheel, wherein each of the wheel valves is, with its respective fluid inlet, fluidly connected to the source of pressurized fluid via a respective line valve, and a control unit, functionally connected to the source and the line valves and configured to control the source and the line valves in dependence of a desired pressure level in the tyres to: increase the pressure level in the tyre by subjecting the fluid inlet to a pressurized fluid at a pressure level above an inflation pressure level and below a deflation pressure level, reduce the pressure level in the tyre by subjecting the fluid inlet to a pressurized fluid at a pressure level above the deflation pressure level, and / or maintain the pressure level in the tyre by subjecting the fluid inlet to a pressurized fluid at a pressure level below the inflation pressure level.

[0084] The tyre pressure control system according to the second aspect of the present invention may comprise one or more of the features and / or benefits disclosed herein in relation to the wheel valve according to the first aspect of the present invention, in particular as recited in the appended claims. The present tyre pressure control system relies on the wheel valves disclosed herein, which are mounted in a rim of the vehicle wheel. As such, at least the wheel inflation opening and the wheel deflation opening of the wheel valve project into the interior of the tyre, whereas the fluid inlet and the exhaust port are located outside the interior of the tyre. Furthermore, the fluid inlet of the wheel valve is connected to the source of pressurized fluid, in order to receive pressurized fluid from the source and to selectively open and close its inflation piston and deflation piston, in dependence of the pressure level at which the pressurized fluid is supplied at the fluid inlet.

[0085] The tyre pressure control system may comprise multiple wheel valves, which are each connected to the source of pressurized fluid. For example, each of the vehicle wheels may comprise its own wheel valve, so that the tyre pressure can be controlled for each of the vehicle’s wheels individually.

[0086] The wheel valves are connected to the source of pressurized fluid via line valves, in particular a single line valve for each wheel valve, so that the pressurized fluid can be supplied to each wheel valve individually, via its respective line valve. All line valves of the tyre pressure control system may be arranged in a single valve block and may each be of the 3 / 2 NC type or 3 / 2 NO type, allowing feedlines towards the wheel valves to be closed from the source of pressurized fluid, to be opened towards the source, or to be deflated to remove residual fluid pressure after closure of the line valve.

[0087] The tyre pressure control system further comprises the control unit, which serves to control the line valves, so that the supply of pressurized fluid towards the wheel valves is controlled. The control unit of the tyre pressure control system further controls the source of pressurized fluid, in order to adjust the pressure level of the pressurized fluid that is supplied to the wheel valves. The control unit is thereby configured to control the state in which the wheel valves are arranged, in particular for each of the wheel valves individually.

[0088] In case it is desired to increase the tyre pressure, the control unit may control the tyre pressure control system to inflate to the tyres. To this effect, the control unit may control the source of pressurized fluid to supply pressurized fluid at a pressure lever higher than the inflation pressure level and lower than the deflation pressure level. The control unit may then further open the line valves, so that the pressurized fluid is supplied at the fluid inlet of the respective wheel valve, after which the wheel valve is brought in the inflation state. In the inflation state, the inflation piston is moved out of the closed position and the pressurized fluid is forced into the tyre, thereby increasing the tyre pressure to inflate the tyre.

[0089] However, in case it is desired to decrease the tyre pressure, the control unit may control the tyre pressure control system to deflate to the tyres. To this effect, the control unit may control the source of pressurized fluid to supply pressurized fluid at a pressure lever higher than the deflation pressure level. The control unit may then further open the line valves, so that the pressurized fluid is supplied at the fluid inlet of the respective wheel valve, after which the wheel valve is brought in the deflation state. In the deflation state, the deflation piston is moved out of the closed position, so that entry of pressurized fluid into the tyre is prohibited and that fluid inside the tyre is allowed to escape from the tyre through the deflation passage and through the exhaust port, thereby decreasing the tyre pressure to deflate the tyre.

[0090] Furthermore, when it is desired to maintain the pressure level in the tyre, the fluid inlet may be subjected to the pressurized fluid at a pressure level below the inflation pressure level, in order to bring the wheel valve in its pressure holding state. Typically, this pressure level may be the ambient pressure level, so that the fluid inlet is not pressurized relative to the ambient. Furthermore, the line valve may be closed, so that no pressurized fluid can reach the wheel valve from the source of pressurized air. In the pressure holding state, the inflation piston and the deflation piston of the wheel valve are held in their closed positions, so that no fluid is forced in the tyre and that no fluid can escape from the tyre, so that the tyre is neither inflated nor deflated and that the tyre pressure is maintained.

[0091] In an embodiment, the control unit is configured to control the line valves sequentially, in order to inflate or deflate the tyres in sequence. This may allow the different tyres to be inflated or deflated after one another, by opening or closing the line valves after each other. For example, a first tyre may be inflated or deflated by operating a first line valve, whereas a second line valve for a second tyre is only operated after the first tyre has been inflated or deflated at least partially. As such, it may be provided that the source of pressurized air can remain pressurized at a desired pressure level and that sufficient pressurized fluid can be supplied to the wheel valves.

[0092] Alternatively, it is to be understood that the line may be controlled simultaneously, in order to inflate or deflate the tyres simultaneously.

[0093] In an embodiment, the control unit is further configured, after controlling an increase or decrease in pressure level, to control the line valves to subject the fluid inlet to a pressure level below the inflation pressure level. This embodiment may enable that the inflation piston and / or the deflation piston are brought back into their closed positions when the inflation or deflation of the respective tyre has been completed. Hence, when the fluid inlet is subjected to a pressure level below the inflation pressure level, the first pretension device will move the deflation piston to the closed position and the second pretension device will move the inflation piston to the closed position. The wheel valve may thereby be brought into its pressure holding state, so that the pressure level in the tyre is maintained. In an embodiment, the tyre pressure control system further comprises a pressure- regulated valve, such as a proportional valve or a multi-pressure valve at the source, which is functionally connected to the control unit and the control unit is further configured to adjust the pressure level at which pressurized fluid is supplied by the source via the pressure-regulated valve. According to this embodiment, the pressure level of the pressurized fluid supplied from the source of pressurized fluid can be adjusted under influence of the pressure-regulated valve, which may be switchable between states depending on an input signal.

[0094] The pressure-regulated valve may be a proportional valve, for example controlled at a pressure level in between the inflation pressure level and the deflation pressure level in case it is desired to inflate the tyres and at a pressure level above the deflation pressure level in case it is desired to deflate the tyres. A multi-pressure valve may similarly be switchable between multiple different pressure levels, for example a system pressure level equal to an input pressure level and a lower, smothered pressure level. The provision of a pressure- regulated, e.g. a proportional valve may provide that the source itself can remain at a constant, preferably a relatively high, pressure level continuously and that the proportional valve can be used to lower the pressure level of the fluid that is eventually supplied to the wheel valves.

[0095] In an embodiment, the tyre pressure control system further comprises a pressure sensor in each of the vehicle wheels, which are functionally connected to the control unit and the control unit is configured to control the source, pressure-regulated, e.g. proportional valve and / or line valves in dependence of a tyre pressure level measured with the pressure sensors. The pressure sensors may each be configured to emit a pressure sensor signal representative of a momentaneous tyre pressure. The control unit is able to obtain this pressure sensor signal in order to retrieve the momentaneous tyre pressure. The control unit is then able to control increasing, decreasing and maintaining of the pressure level in the tyres on the basis of a comparison between the momentaneous tyre pressure retrieved from the pressure sensor and a desired set value for the tyre pressure.

[0096] In an embodiment, the wheel valves are mounted through the respective rims and the inflation opening, e.g. a wheel inflation opening, and the deflation opening, e.g. wheel deflation opening, of the wheel valve project into the interior of the respective tyre. According to this embodiment, the wheel valves actually project into the interior of the respective tyres, so that the wheel inflation openings and the wheel deflation openings are in direct fluid communication with the interior of the tyres. In an alternative embodiment, the wheel valves are mounted remotely from the interior of the respective tyre and the wheel valves further each comprise a wheel fluid line, extending from the inflation opening and the deflation opening towards the interior of the respective tyre. As such, the wheel valves may be located closer to the centre of the wheels, only requiring the wheel fluid lines to extend towards the respective rims and tyres. The fluid lines may be conveniently connected to the rims in a manner similar to conventional tyre valves.

[0097] This embodiment may offer the benefit that the eccentricity of the wheels, and therefore their degree of imbalance, can be reduced. Furthermore, it may provide that the wheel valves are positioned at locations where they are less prone to damaging, i.e. away from the tyres.

[0098] In a further embodiment, the wheel valve is mounted at a hub of the respective wheel, for example adjacent to a rotary transmission joint of the wheel. This may allow the wheel valve to be mounted adjacent to, or even integrated in a rotary fluid joint for the wheel. Such a rotary transmission joint, which is for example disclosed in NL 2036176, can be provided to transfer pressurized fluid from a stationary axle towards the rotary wheel. As such, existing vehicle wheels can be easily retrofitted with a tyre pressure control system, e.g. by simply replacing a conventional tyre valve with the current fluid line, therefore not requiring complicated modifications to the wheels.

[0099] According to a third aspect, the present invention provides a method of inflating or deflating a tyre mounted on a rim of a vehicle wheel by means of a wheel valve under influence of a pressurized fluid, for example by means of a tyre pressure control system as disclosed herein, the method comprising the steps of: providing a wheel valve, preferably a wheel valve as disclosed herein, associating the wheel valve with the rim, so that the inflation opening and deflation opening of the wheel valve are fluidly connected with an interior of the tyre, in particular mounting to the wheel valve to the rim, so that the wheel inflation opening and wheel deflation opening of the wheel valve project into the interior of the tyre, connecting the fluid inlet to a source of pressurized fluid, and one or more of the steps of: inflating the tyre by subjecting the fluid inlet to a pressurized fluid at a pressure level above an inflation pressure level and below a deflation pressure level, deflating the tyre by subjecting the fluid inlet to a pressurized fluid at a pressure level above the deflation pressure level, and / or maintaining a pressure level in the tyre by subjecting the fluid inlet to a pressurized fluid at a pressure level below the inflation pressure level. The method according to the third aspect of the present invention may comprise one or more of the features and / or benefits disclosed herein in relation to the wheel valve according to the first aspect of the present invention and / or the tyre pressure control system according to the second aspect of the present invention, in particular as recited in the appended claims

[0100] According to the present method, the pressure level in tyres of a vehicle can be controlled, preferably in an automated manner. Each of the wheels of the vehicle comprises a wheel valve, of which the inflation piston and deflation piston can be held in, or moved out of a closed position in dependence of a pressure level at which pressurized fluid is supplied to a fluid inlet of the wheel valve. The wheel valves are mounted to the rim of their respective wheel, so that the wheel inflation opening and wheel deflation opening of the wheel valve project into an interior of the tyre. The wheel valves are connected to the source of pressurized fluid with their fluid inlets. As such, the wheel valves can selectively allow fluid to flow through the wheel valve or to be blocked therewith in dependence of the pressure level.

[0101] The present method comprises one or more of the steps inflating the tyre, deflating the tyre and of maintaining the pressure level in the tyre. These steps are selected in dependence of the pressure level supplied at the fluid inlet of the wheel valve.

[0102] In case it is desired to inflate to the tyres, the wheel valves may be set to increase the tyre pressure. To this effect, the source of pressurized fluid may supply pressurized fluid at a pressure lever higher than the inflation pressure level and lower than the deflation pressure level. As a result, the wheel valve may be brought in the inflation state, whereby the inflation piston is moved out of the closed position and the pressurized fluid is forced into the tyre, thereby increasing the tyre pressure to inflate the tyre.

[0103] However, in case it is desired to deflate to the tyres, the wheel valve may be set to decrease the tyre pressure. To this effect, source of pressurized fluid may supply pressurized fluid at a pressure lever higher than the deflation pressure level. As a result, the wheel valve may be brought in the deflation state, whereby the deflation piston is moved out of the closed position, so that entry of pressurized fluid into the tyre is prohibited and that fluid inside the tyre escapes from the tyre through the deflation passage and through the exhaust port, thereby decreasing the tyre pressure to deflate the tyre.

[0104] Furthermore, to maintain the pressure level in the tyre, the fluid inlet is subjected to the pressurized fluid at a pressure level below the inflation pressure level, which may to bring the wheel valve in its pressure holding state. Typically, this pressure level may be the ambient pressure level, so that the fluid inlet is not pressurized relative to the ambient. In the pressure holding state, the inflation piston and the deflation piston of the wheel valve are held in their closed positions, so that no air is forced in the tyre and that no air can escape from the tyre, so that the tyre is neither inflated nor deflated and that the tyre pressure is maintained. In an embodiment, the inflation pressure level is equal to or larger than the second pretension force divided by the surface area of the inflation piston surface. The net resulting force on the inflation piston must thus be facing away from the fluid inlet to move the inflation piston out of the closed position. The inflation pressure level is thereby defined as the pressure level that is sufficient to overcome the second pretension force, when multiplied by the surface area of the inflation piston, and to move the inflation piston out of the closed position.

[0105] Additionally, the fluid pressure at the fluid inlet may also need to overcome a counter force of the fluid pressure in the tyre exerting a force on the inflation piston at a counter surface opposite to the inflation piston surface facing the fluid inlet, which acts alongside with the second pretension device and which thus influences the net force acting on the inflation piston. As such, the inflation pressure level may need to be equal to or larger than the sum of the second pretension force and the pressure level in the tyre multiplied by the area of the counter surface of the inflation piston, divided by the surface area of the inflation piston surface facing the fluid inlet.

[0106] In an embodiment, the inflation pressure level is defined in the range between 0.3 bar and 5 bar. It was found by the present inventors that an inflation pressure level in this range may be sufficient to control tyre pressures in many different applications, for example for agricultural vehicles that drive on roads at a relatively high tyre pressure and in the fields at a relatively low tyre pressure. Furthermore, this inflation pressure level may be favourable to allow accurate controlling of the tyre pressure during inflation and that a sufficiently large pressure differential may be obtained to offer a desirable flow rate of pressurized fluid through the wheel valve during inflation of the tyre.

[0107] In an embodiment, the deflation pressure level is equal to or larger than the first pretension force divided by the surface area of the deflation piston surface. The net resulting force on the deflation piston must thus be facing away from the fluid inlet to move the deflation piston out of the closed position. The deflation pressure level is thereby defined as the pressure level that is sufficient to overcome the first pretension force, when multiplied by the surface area of the deflation piston, and to move the deflation piston out of the closed position.

[0108] Additionally, the fluid pressure at the fluid inlet may also need to overcome a counter force of the fluid pressure in the tyre exerting a force on the deflation piston at a counter surface opposite to the deflation piston surface facing the fluid inlet, which acts alongside with the first pretension device and which thus influences the net force acting on the deflation piston. As such, the deflation pressure level may need to be equal to or larger than the sum of the first pretension force and the pressure level in the tyre multiplied by the area of the counter surface of the deflation piston, divided by the surface area of the deflation piston surface facing the fluid inlet.

[0109] In an embodiment, the deflation pressure level is at least 6 bar. It was found by the present inventors that a deflation pressure level above this pressure level is sufficient to deflate tyres in many different applications, for example for agricultural vehicles, as it lies above the pressure levels are typically present in the tyres of such vehicles.

[0110] In an embodiment, the method further comprises, after the steps of inflating and / or deflating, the step of releasing pressure at the fluid inlet below the inflation pressure level. The releasing of pressure may be done by opening the respective line valves in between the source of pressurized fluid and the wheel valves. In general, the release of pressure at the fluid inlet implies that the inflation piston and / or the deflation piston are brought back into their closed positions when the inflation or deflation of the respective tyre has been completed. Hence, when the fluid inlet is subjected to a pressure level below the inflation pressure level, the first pretension device will move the deflation piston to the closed position and the second pretension device will move the inflation piston to the closed position. The wheel valve may thereby be brought into its pressure holding state, so that the pressure level in the tyre is maintained.

[0111] Brief description of drawings

[0112] Further characteristics of the invention will be explained below, with reference to embodiments, which are displayed in the appended drawings, in which:

[0113] Figure 1 schematically depicts an embodiment of the wheel valve according to the present invention, displayed in its holding state,

[0114] Figure 2 shows the wheel valve of figure 1 in its inflation state,

[0115] Figure 3 shows the wheel valve of figure 1 in its deflation state,

[0116] Figure 4 shows a schematic embodiment of a tyre pressure control system according to the present invention,

[0117] Figure 5 schematically depicts an alternative embodiment of the wheel valve according to the present invention, displayed in its holding state,

[0118] Figure 6 schematically depicts a further embodiment of the wheel valve according to the present invention, displayed in its holding state, and Figures 7A and 7B show a further alternative embodiment of the wheel valve in a schematic representation, in which the flows of pressurized fluid are shown during inflation and deflation of a tyre.

[0119] Throughout the figures, the same reference numerals are used to refer to corresponding components or to components that have a corresponding function.

[0120] Detailed description of embodiments

[0121] Figure 1 schematically depicts an embodiment of the wheel valve according to the present invention, to which is referred with reference numeral 1. The wheel valve 1 is intended for use in a tyre pressure control system 50 for mounting in a rim 100 of a vehicle wheel and for inflating or deflating a tyre 101 mounted on the rim 100 by means of a pressurized fluid.

[0122] The valve 1 comprises a valve housing 10, which is mounted through the rim 100 by means of a threaded connection. In the present embodiment, the valve housing 10 is assembled of multiple pieces that together form the valve housing 10. In other embodiments, the valve housing may as well be a single one-piece housing.

[0123] Part of the valve housing 10 projects into the interior of the tyre 101 that is mounted on the rim 100, whereas another part of the valve housing 10 is accessible from outside the tyre 101. In particular, the valve housing 10 comprises a fluid inlet 11 that is accessible from outside the wheel and comprises a plurality of wheel inflation openings 12 that project into the interior of the tyre 101.

[0124] The fluid inlet 11 is connectable to a source of pressurized fluid 51 via a feedline 52 for receiving pressurized fluid from the source. The wheel valve 1 is free of other fluid inlets for receiving pressurized fluids. In the current embodiment, the wheel inflation openings 12 are spaced around a centreline of the valve 1. The valve housing 10 further comprises a hollow interior in between the fluid inlet 11 and the wheel inflation openings 12.

[0125] The valve 1 further comprises a deflation piston 20, which is arranged in the valve housing 10 and which comprises a deflation piston surface 21 and which defines an inflation passage 22 extending between the fluid inlet 11 and the wheel inflation opening 12. The deflation piston surface 21 faces towards the fluid inlet 11 , so that pressurized fluid supplied into the valve 1 at the fluid inlet 11 acts against the piston surface 21 of the deflation piston 20. The pressure level of the pressurized fluid at the piston surface 21 of the deflation piston 20 thereby determines the position or state in which the deflation piston 20 is arranged. The deflation piston 20 is arranged in the valve housing 10 and is thus configured to move in relation to the valve housing 10 when moving between its closed position, as it is shown in figures 1 and 2, and an opened position, as it is shown in figure 3. The valve 1 comprises a first pretension device, embodied as a first compression spring 23, which is configured to exert a first pretension force onto the deflation piston 20 relative to the valve housing 10. In the orientation of the valve 1 shown in the figures, the first pretension force is aligned in a vertically upward direction, so that the first compression spring 23 will bias the deflation piston 20 towards the fluid inlet 11 into its closed position. The net force acting on the deflation piston 20 is thus formed by the pressurized fluid acting on the piston surface 21 of the deflation piston 20 on the one hand and the first pretension force by the first compression spring 23 on the other hand, wherein a further contribution is provided by a pressure level of the fluid in the interior of the tyre 101 acting on the deflation piston 20. In particular, the tyre pressure acts on a counter surface, i.e. a lower surface in the orientation of the figures, opposite to the piston surface 21 thereof, thus acting alongside the first compression spring 23 towards the fluid inlet 11.

[0126] The deflation piston 20 comprises the inflation passage 22, which extends along the centreline of the deflation piston 20. The inflation passage 22 forms a channel for the fluid between the fluid inlet 11 and the wheel inflation opening 12, irrespective of the position of the deflation piston 20, so that the tyre 101 can be inflated through the inflation passage 22

[0127] The valve 1 further comprises an inflation piston 30 arranged in the inflation passage 22, which serves to selectively close off the inflation passage 22. The inflation piston 30 comprises, in a manner similar to the deflation piston 20, a piston surface 31 that faces towards the fluid inlet 11. Any pressurized fluid at the fluid inlet 11, during use of the valve 1, thus acts against the piston surface 31 of the inflation piston 30. This inflation piston 30 is arranged in the deflation piston 20 and is thus configured to move in relation to the deflation piston 20 when moving between its closed position and an opened position. In figure 1 , the inflation piston 30 is shown in its closed position and the inflation piston 30 is shown in the opened position in figures 2 and 3.

[0128] The valve 1 comprises a second pretension device, embodied as a second compression spring 32, which configured to exert a second pretension force onto the inflation piston 30 relative to the deflation piston 20. In the orientation of the valve 1 shown in the figures, the second pretension force is aligned in a vertically upward direction, so that the second compression spring 32 will bias the inflation piston 30 towards the fluid inlet 11 into the closed position. As such, any movement of the deflation piston 20 relative to the housing 10 will therefore not have any influence on the position of the inflation piston 30 inside the deflation piston 20.

[0129] The deflation piston 20 comprises an inflation seat 24, which is located inside the inflation passage 22. The inflation piston 30 is pushed against the inflation seat 24 under influence of the second compression spring 32 when the inflation piston 30 is biased in the closed position, so that the inflation passage 22 will be closed off, thereby preventing passage of pressurized fluid from the fluid inlet 11 towards the wheel inflation openings 12, and vice versa. The net force acting on the inflation piston 30 is thus formed by the pressurized fluid acting on the piston surface 31 of the inflation piston 30 on the one hand and the second pretension force by the second compression spring 32 on the other hand, wherein a further contribution is provided by a pressure level of the fluid in the interior of the tyre 101 acting on the inflation piston 30. In particular, the tyre pressure acts on a counter surface, i.e. a lower surface in the orientation of the figures, opposite to the piston surface 31 thereof, thus acting alongside the second compression spring 32 towards the fluid inlet 11.

[0130] The working principle of the present valve 1 is contributed by the mutual relationship between the piston surfaces 21, 31 of the deflation piston 20 and of the inflation piston 30, as well as between the first compression spring 23 and the second compression spring 32. These are selected such that both the deflation piston 20 and the inflation piston 30 are arranged in their closed positions, i.e. as shown in figure 1, when the pressure level at the fluid inlet 11 is below an inflation pressure level. The inflation piston 30 is moved out of its closed position, as shown in figure 2, when the pressure level at the fluid inlet 11 is above the inflation pressure level, but below a deflation pressure level, in order to allow fluid to pass from the fluid inlet 11 towards the wheel inflation openings 12. Finally, the deflation piston 20 is moved out of its closed position, as shown in figure 3, when the pressure level at the fluid inlet 11 is above the deflation pressure level, so that the tyre 101 can be deflated through the valve 1. To this effect, the surface area of the inflation piston surface 31 is smaller than the surface area of the deflation piston surface 32. Likewise, the first compression spring 23 is shown to be relatively strong and rigid relative to the second compression spring 32.

[0131] The valve 1 further comprises an inflation passage closure 13, which is attached to the valve housing 10 and which is configured to close off the inflation passage 22 when the deflation piston 20 is moved out of its closed position. In the closed position of the deflation piston 20, as shown in figures 1 and 2, the inflation passage closure 13 is spaced at a distance from the inflation passage 22, to enable a fluid flow through the inflation passage 22.

[0132] If the deflation piston 20 is moved out of its closed position, i.e. when the valve 1 is brought in the deflation state 20 shown in figure 3, the inflation passage closure 13 remains in place as it is attached to the valve housing 10. As a result of the movement of the deflation piston 20, the inflation passage closure 13 will project into and will come to seal against the inflation passage 22, so that the inflation passage 22 is closed off. This means that no fluids can pass through the inflation passage 22 when the deflation piston 20 is moved out of the closed position. The inflation passage closure 13 thereby provides that the inflation passage 22 remains closed during deflation, even when the inflation piston 30 is moved out of closed position as a result of a relatively high pressure level at the fluid inlet 11. The valve 1 further comprises a non-return valve in front of the wheel inflation openings 12, embodied as a flexible closure element 14, for preventing fluid to flow back from the interior of the tyre 101 into the inflation passage 22. The flexible closure element 14 is a disc made of an elastic material, which surrounds the inflation passage closure 13. The closure element 14 will be opened in case the pressure level in the inflation passage 22 is larger than the pressure level in the tyre 101, i.e. during inflation, as it is shown in figure 2. The closure element 14 is further configured to close off the wheel inflation openings 12 in the absence of a pressure differential, to prevent a backflow of fluid and contaminants from the tyre 101 into the inflation passage 22.

[0133] The valve 1 further comprises multiple wheel deflation openings 15, which are provided in the valve housing 10 and which project into the interior of the tyre 101 and which are separate and located at a distance from the wheel inflation openings 12. The multiple deflation openings 15 are spaced around an outer perimeter of the housing 10 and the deflation piston 20. The wheel deflation openings 15 project into the interior of the tyre 101 in a manner similar to the wheel inflation openings 12, albeit at a different location. Hence, the wheel inflation openings 12 are provided as multiple openings at a head end of the valve housing 10 that project into the interior of the tyre 101. The wheel deflation openings 15 are located around the circumference of the portion of the valve housing 10 projecting into the interior of the tyre 101.

[0134] The valve 1 also comprises a plurality of exhaust ports 16, which are provided in the valve housing 10 and which project into the ambient for discharging fluid out of the tyre 101 to deflate the tyre 101. The exhaust ports 16 are configured to discharge fluids out of the tyre 101 into the ambient of the wheel during deflation. This allows the deflated fluid to bypass the inflation passage 22.

[0135] The valve 1 further comprises a number of deflation passages 17, which extend between the wheel deflation openings 15 and the exhaust ports 16 and which are separate from the inflation passage 22, which allows that deflation will not influence the inflation passage 22, for example preventing that possible contaminations inside the tyre 101 will end up in the inflation passage 22 during deflation of the tyre 101.

[0136] The deflation passages 17 are defined in between the valve housing 10 and the deflation piston 20, so that the fluid deflated from the tyre 101 can be guided around the outside of the deflation piston 20. The deflation piston 20 thereby forms the separation between the inflation passage 22 and the deflation passages 17, which are spaced around the outer perimeter of the deflation piston 20.

[0137] In the closed position, shown in figures 1 and 2, the deflation piston 20 closes the deflation passages 17. As such, it can be prevented that the tyre 101 is deflated, both when the inflation piston 30 is closed as shown in figure 1, i.e. to maintain a pressure level in the tyre 101, and when the inflation piston 30 is moved out of its closed position as shown in figure 2, i.e. during inflation of the tyre 101. To this effect, the valve housing 10 comprises an annular deflation seat 18 in the deflation passages 17, so that it surrounds the deflation piston 20 that is arranged in the valve housing 10. The deflation piston 20 has a corresponding annular surface 25 at its outer perimeter, made of an elastomeric material, in order to seal against the deflation seat 18 in its closed portion and to seal the multiple deflation passages 17 that are spread around the perimeter of the deflation piston 20.

[0138] The valve 1 further comprises a number of exhaust closure elements at the exhaust ports 16, which are embodied as flexible closure elements 19 located in front of the exhaust ports 16. The closure elements 19 serve to prevent fluid and contaminants to flow into the deflation passages 17 from outside the wheel valve 1. The closure element 19 is configured to open in case the pressure level in the deflation passages 17 is larger than the ambient pressure level, i.e. during the deflation shown in figure 3, whereas the exhaust closure element 19 is configured to close off the exhaust ports 16 in the absence of such a pressure differential.

[0139] The valve 1 further comprises a filter element 26 arranged in front of the wheel deflation openings 15, for preventing contaminants from entering the deflation passages 17 from the tyre 101. The filter element 26 is made of a sintered material and embodied as a sleeve element surrounding the portion of the valve housing 10 that is located in the interior of the tyre 101 , so that the filter element 26 projects in front of all wheel deflation openings 15.

[0140] The operation of the valve 1 is shown by reference to three different states of the valve 1 , which are shown in figures 1 - 3. These figures also represent an embodiment of the method according to the present invention.

[0141] Figure 1 shows the valve 1 in its holding state, in which the deflation piston 20 and the inflation piston 30 are arranged in their closed positions. This is caused by the pressure level at the fluid inlet 11 to be below the inflation pressure level, so that the valve 1 is configured to maintain the pressure level in the tyre 101.

[0142] The inflation pressure level is a maximum pressure level, below which the valve 1 is held in the pressure holding state. In the present embodiment, the inflation pressure level is defined in the range between 0.3 bar and 5 bar, e.g. about 2.8 bar. During inflation, the fluid pressure at the fluid inlet 11 may need to overcome a counter force of the fluid pressure in the tyre 101 exerting a force on the inflation piston 30 at a counter surface, i.e. lower surface, opposite to the inflation piston surface 31 facing the fluid inlet 11. The tyre pressure acts alongside with the second compression spring 32 and thus influences the net force acting on the inflation piston 30. As such, the inflation pressure level may need to be equal to or larger than the sum of the second pretension force and the pressure level in the tyre 101 multiplied by the area of the counter surface of the inflation piston 30, divided by the surface area of the inflation piston surface 31 facing the fluid inlet 11.

[0143] Figure 2 shows the valve 1 in its inflation state, in which the deflation piston 20 is arranged in its closed position and in which the inflation piston 30 is moved out of its closed position. This is caused by the pressure level at the fluid inlet 11 to be above the inflation pressure level and below a deflation pressure level. In the inflation state, the wheel valve 1 allows pressurized fluid to pass from the fluid inlet 11 to the tyre 101, via the inflation passage 22, the inflation piston 20 and the wheel inflation openings 12. As a result, the tyre 101 is inflated and the pressure level inside the tyre 101 will be increased.

[0144] Figure 3 shows the valve 1 in the deflation state, in which the deflation piston 20 is moved out of its closed position as a result of the pressure level at the fluid inlet 11 being above the deflation pressure level. In the deflation state, the wheel valve 1 allows for reducing the pressure level in the tyre 101, thereby allowing fluid to pass from the tyre 101 to the ambient through the wheel valve 1, via the wheel deflation openings 15, the deflation passages 17 and the exhaust ports 16.

[0145] It is shown in figure 3 that the inflation piston 30 may, but not necessarily needs to, be moved out of the closed position in the deflation state. However, the inflation passage 22 is still closed off to prevent deflation from taking place through the inflation passage 22 and to prevent pressurized fluid at the fluid inlet 11 from entering into the tyre 101. In this configuration, the deflation passages 17 are opened by the deflation piston 20, which enables fluid to flow out of the interior of the tyre 101 into the valve 1, through the wheel deflation openings 15. The wheel deflation openings 15 may then further guide the fluid through the deflation passages 17 and, finally, into the ambient of the valve 1 , via the exhaust ports 16. With the fluid flowing out of the tyre 101, the pressure level in the tyre 101 is lowered, therewith effecting deflation of the tyre 101.

[0146] The deflation pressure level is a minimum pressure level, above which the valve 1 is held in the deflation state. In the present embodiment, the deflation pressure level is at least 6 bar, for example about 7 bar. During deflation, the fluid pressure at the fluid inlet 11 may need to overcome a counter force of the fluid pressure in the tyre 101 exerting a force on the deflation piston 20 at a counter surface, i.e. lower surface, opposite to the deflation piston surface 21 facing the fluid inlet 11. The tyre pressure acts alongside with the first compression spring 23 and thus influences the net force acting on the deflation piston 20. As such, the deflation pressure level may need to be equal to or larger than the sum of the first pretension force and the pressure level in the tyre 101 multiplied by the area of the counter surface of the deflation piston 20, divided by the surface area of the deflation piston surface 21 facing the fluid inlet 11. Figure 4 shows a schematic embodiment of the tyre pressure control system 50 according to the present invention. The tyre pressure control system 50 is configured to control the tyre pressure in multiple vehicle wheels, e.g. four wheels in the present embodiment shown in the figures, by inflating or deflating tyres 101 of the wheels. The system 50 comprises the source of pressurized fluid 51 , which is configured to supply pressurized fluid, and comprises a respective wheel valve 1 projecting in each of the vehicles tyres 101 , which are fluidly connected to the source 51 by means of the feedlines 52.

[0147] The wheel valves 1 are connected to the source of pressurized fluid 51 via line valves

[0148] 53, i.e. a single line valve 53 for each wheel valve 1, so that the pressurized fluid can be supplied to each wheel valve 1 individually, via its respective line valve 53. All line valves 53 of the tyre pressure control system 50 are arranged in a single valve block and are each of the 3 / 2 NC type, allowing the feedlines 52 towards the wheel valves 1 to be closed from the source 51, to be opened towards the source 51 , or to be deflated to remove residual fluid pressure after closure of the line valve 53.

[0149] The tyre pressure control system 50 further comprises the control unit 54, which serves to control the line valves 53, so that the supply of pressurized fluid towards the wheel valves 1 is controlled. The control unit 54 further controls the source of pressurized fluid 51 , in particular a pressure-regulated valve, currently embodied as a proportional valve 56 thereof, in order to adjust the pressure level of the pressurized fluid that is supplied to the wheel valves 1. The control unit 54 is thereby configured to control the state in which the wheel valves 1 are arranged, in particular for each of the wheel valves 1 individually.

[0150] It is noted that the solid lines in figure 4 represent fluid lines for guiding a flow of pressurized fluid. Dashed lines represent electronic connections to and from the control unit 54 for obtaining and / or transmitting control signals and / or sensor signals.

[0151] The tyre pressure control system 50 further comprises a pressure sensor 55 projecting in the interior of each of the tyres 101. The pressure sensors 55 are functionally connected to the control unit 54 and the control unit 54 is configured to control the source 51 , the proportional valve 56 and the line valves 53 in dependence of a tyre pressure level measured with the pressure sensors 55. The pressure sensors 55 are each configured to emit a pressure sensor signal representative of a momentaneous tyre pressure in their respective tyre 101. The control unit 54 is able to obtain this pressure sensor signal in order to retrieve the momentaneous tyre pressure and then able to control increasing, decreasing and maintaining of the pressure level in the tyres 101 on the basis of a comparison between the momentaneous tyre pressure retrieved from the pressure sensor 55 and a desired set value for the tyre pressure.

[0152] The proportional valve 56 at the source 51 is functionally connected to the control unit

[0153] 54, so that the control unit 54 is further configured to adjust the pressure level at which pressurized fluid is supplied by the source 51. As such, the pressure level of the pressurized fluid supplied from the source 51 can be adjusted, for example controlled at a pressure level in between the inflation pressure level and the deflation pressure level in case it is desired to inflate the tyres 101 and at a pressure level above the deflation pressure level in case it is desired to deflate the tyres 101.

[0154] In case it is desired to increase the tyre pressure, the control unit 54 may control the tyre pressure control system 50 to inflate to the tyres. To this effect, the control unit 54 may control the source 51 with the proportional valve 56 to supply pressurized fluid at a pressure lever higher than the inflation pressure level and lower than the deflation pressure level. The control unit 54 may then further open the line valves 53, so that the pressurized fluid is supplied at the fluid inlet of the respective wheel valve 1, after which the wheel valve 1 is brought in the inflation state. In the inflation state, the inflation piston is moved out of the closed position and the pressurized fluid is forced into the tyre 101, thereby increasing the tyre pressure to inflate the tyre 101.

[0155] However, in case it is desired to decrease the tyre pressure, the control unit 54 may control the tyre pressure control system 50 to deflate to the tyres 101. To this effect, the control unit 54 may control the source 51 with the proportional valve 56 to supply pressurized fluid at a pressure lever higher than the deflation pressure level. The control unit 54 may then further open the line valves 53, so that the pressurized fluid is supplied at the fluid inlet of the respective wheel valve 1, after which the wheel valve 1 is brought in the deflation state. In the deflation state, the deflation piston is moved out of the closed position, so that entry of pressurized fluid into the tyre 101 is prohibited and that fluid inside the tyre 101 is allowed to escape from the tyre 101 through the deflation passage and through the exhaust port, thereby decreasing the tyre pressure to deflate the tyre 101.

[0156] Furthermore, when it is desired to maintain the pressure level in the tyre 101, the fluid inlet may be subjected to the pressurized fluid at a pressure level below the inflation pressure level, in order to bring the wheel valve 1 in its pressure holding state. Typically, this pressure level may be the ambient pressure level, so that the fluid inlet is not pressurized relative to the ambient. Furthermore, the line valve 53 may be closed, so that no pressurized fluid can reach the wheel valve 1 from the source 51. In the pressure holding state, the inflation piston and the deflation piston of the wheel valve 1 are held in their closed positions, so that no fluid is forced in the tyre 101 and that no fluid can escape from the tyre 101, so that the tyre 101 is neither inflated nor deflated and that the tyre pressure is maintained.

[0157] The control unit 54 may be configured to control the line valves 53 in the valve block sequentially, in order to inflate or deflate the tyres 101 in sequence. This may allow the different tyres 101 to be inflated or deflated after one another, by opening or closing the line valves 53 after each other. The control unit 54 is further configured, after controlling an increase or decrease in pressure level, to control the line valves 53 to subject the fluid inlet of the wheels valves 1 to a pressure level below the inflation pressure level. This enables that the inflation piston and the deflation piston of the wheel valve 1 are brought back into their closed positions when the inflation or deflation of the respective tyre 101 has been completed. The wheel valve 1 may thereby be brought into its pressure holding state, so that the pressure level in the tyre 101 is maintained.

[0158] This may be effected by controlling the release of pressure at the fluid inlet of the wheel valves 1 by opening the respective line valves 53 between the source 51 and the wheel valves 1 , so that the pressure level in the feedlines 52 is lowered to the ambient pressure level, so that the wheel valves 1 are brought into their pressure holding states.

[0159] Figure 5 shows an alternative embodiment of the wheel valve 1 according to the present invention. This wheel valve 1 is mounted to remotely from the tyres, being provided at a hub 200 to which the rim is attached. In the current example, the wheel valve 1 is provided adjacent to a rotary transmission joint inside the hub 200.

[0160] The working principle of the wheel valve 1 in figure 5 is similar to that of the wheel valve 1 in figures 1 - 3, wherein the valve is displayed in its holding state, similar as the wheel valve 1 in figure 1. The wheel valve 1 in figure 5 similarly also comprises a valve housing 10 with a fluid inlet 11 and wheel inflation opening 12. The valve 1 also comprises the deflation piston 20 and inflation piston 30 inside it. The wheel valve 1 comprises a number of exhaust ports 16 around the perimeter of the valve housing 10, which are closed-off from the surroundings by flexible closure elements 19, as well as a filter element 26 covering the wheel deflation openings 15.

[0161] The valve housing 10 comprises an annular cap member 40, which surrounds the filter element 26 and all of the wheel deflation openings 15, which are spread around the perimeter of the valve housing 10. The cap member 40 defines a cap member interior 41, inside which the inflation passage closure, e.g. the flexible closure element 14 is provided. The valve 1 further comprises a wheel fluid line 42, of which a fitment 43 it attached to the cap member 40. The wheel fluid line 42 thereby serves to connect the camp member interior 41, and therefore the wheel inflation openings 12 and wheel deflation openings 15 with the tyre.

[0162] The cap member 40 comprises the inflation passage closure 13, embodied as a unitary component. The cap member 40 thereby forms a seat for the first pretension device, e.g. the first compression spring 23, so that the deflation is pretensioned by the first compression spring 23 against the cap member 40, whereby the first compression spring 23 is provided around the inflation passage closure 13 to secure a sideward position of the first compression spring 23 vis-a-vis the cap member 40. The embodiment of the wheel valve 1 shown in figure 6 is similar to the wheel valve in figure 5. However, both embodiments differ in that the wheel valve in figure 6 comprises the combined inflation opening and deflation opening, embodied as a common opening 12A that is fluidly connectable to the inflation passage 22, the deflation passage 17 and the interior of the tyre via the wheel fluid line 42. In this situation, a set of common openings 12A is provided in the valve housing 10, which are surrounded by the filter element 26. As such, the inflating and deflating will be performed through the common opening 12A, whereby internally in the valve housing 10, the inflation passage 22 and deflation passage 17 are provided separate from each other.

[0163] During deflation, as shown in the configuration of figure 6, the inflation passage 22 remains closed, so that pressurized fluid can only travel out of interior of the tyre and from the wheel fluid line 42, through the common opening 12A and into the deflation channel 17.

[0164] The wheel valve 1 further comprises a deflation piston guide, e.g. located adjacent the inflation passage closure, which is embodied as a number of deflation piston guiding pins 29 around the perimeter of the deflation piston 20 between which apertures are defined and which jointly guide the deflation piston 20. The deflation piston guiding pins 29 are located around the perimeter of the deflation piston 20, in order to prevent the deflation piston 20 from moving sideward, in order to stabilize the position of the deflation piston 20. The apertures in between the deflation piston guiding pins 29 serve to guide a fluid flow out of the inflation passage 22 towards the inflation openings, e.g. common openings 12A when the deflation piston 20 is moved out of its closed position in which it is shown in figure 6.

[0165] Figures 7A and 7B show a further alternative embodiment of the wheel valve 1 in a schematic representation, in which the flows of pressurized fluid are shown during inflation and deflation of a tyre.

[0166] In figure 7A, the wheel valve 1 is shown with the inflation piston 30 in the opened position and the deflation piston 20 in the opened position. As such, pressurized fluid can flow from the fluid inlet 11, along the inflation piston 30, through the inflation passage 22 in the deflation piston 20 towards the common openings 12A and the filter element 26. From there, the fluid will flow through the cap member 40 towards the wheel fluid line 42 and the interior of the tyre.

[0167] In figure 7B, the wheel valve 1 is shown during deflation, where fluid arrives from the wheel fluid line 42 into the cap member 40. The deflation piston 20 is in its closed position and the fluid enters the valve housing 10 through the filter element 26 and the common openings 12A, therewith blocking contaminant. From there, the fluid flows through the deflation passage 17 and out of the valve housing 10 via the exhaust port 16, that is concentric with the fluid inlet 11 , and the ring-shaped flexible closure element 19.

Claims

CLAIMS1. Wheel valve for a tyre pressure control system to be associated with a rim of a vehicle wheel and for inflating or deflating a tyre mounted on the rim by means of a pressurized fluid, the valve comprising: a valve housing, comprising: a fluid inlet that is connectable to a source of pressurized fluid, and an inflation opening, which is configured to be fluidly connected to an interior of the tyre mounted on the rim, a deflation piston arranged in the valve housing, which comprises a deflation piston surface and which defines an inflation passage extending between the fluid inlet and the inflation opening, a first pretension device configured to exert a first pretension force onto the deflation piston relative to the valve housing, in order to bias the deflation piston towards the fluid inlet into a closed position, an inflation piston arranged in the inflation passage, which comprises an inflation piston surface, a second pretension device configured to exert a second pretension force onto the inflation piston relative to the deflation piston, in order to bias the inflation piston towards the fluid inlet into a closed position against an inflation seat provided on the deflation piston, characterized in that, the valve further comprises: a deflation opening, which is configured to be fluidly connected to the interior of the tyre, an exhaust port, which projects into the ambient for discharging fluid out of the tyre to deflate the tyre, and a deflation passage, which extends between the deflation opening and the exhaust port and which is separate from the inflation passage, and wherein the deflation piston, in its closed position, closes the deflation passage between the deflation opening and the exhaust port.

2. Wheel valve according to claim 1 , wherein the deflation opening is separate and located at a distance from the inflation opening.

3. Wheel valve according to claim 1 , wherein the inflation opening and the deflation opening are combined as a common opening that is fluidly connectable to the inflation passage, the deflation passage and the interior of the tyre.

4. Wheel valve according to any of the preceding claims, wherein the valve housing comprises a deflation seat in the deflation passage, and wherein the deflation piston, in its closed position, contacts the deflation seat to close the deflation passage.

5. Wheel valve according to any of the preceding claims, wherein the deflation passage surrounds the deflation piston, and / or wherein the deflation piston surrounds the inflation passage.

6. Wheel valve according to any of the preceding claims, comprising multiple of the deflation openings and / or exhaust ports, which are spread over a perimeter of the valve housing.

7. Wheel valve according to any of the preceding claims, wherein the deflation piston and the inflation piston are arranged in their closed positions when a pressure level at the fluid inlet is below an inflation pressure level, in order to arrange the wheel valve in a pressure holding state for maintaining a pressure level in the tyre.

8. Wheel valve according to any of the preceding claims, wherein the deflation piston is moved out of its closed position when a pressure level at the fluid inlet is above a deflation pressure level, in order to arrange the wheel valve in a deflation state for reducing the pressure level in the tyre, thereby allowing fluid to pass from the tyre to the ambient through the wheel valve, via the deflation opening, the deflation passage and the exhaust port.

9. Wheel valve according to any of the preceding claims, further comprising a inflation passage closure, which is attached to the valve housing, e.g. forming part of the valve housing, and which is configured to close off the inflation passage when the deflation piston is moved out of its closed position.

10. Wheel valve according to claim 9, wherein the inflation passage closure projects into the inflation passage when the deflation piston is moved out of its closed position, to seal off the inflation passage against the deflation piston.

11. Wheel valve according to any of the preceding claims, wherein the valve housing further comprises a deflation piston guide, e.g. located adjacent the inflation passage closure, which is configured to guide movements of the deflation piston between its closed position and an opened position.

12. Wheel valve according to claim 11 , wherein the deflation piston guide comprises one or more apertures for guiding a fluid flow out of the inflation passage towards the inflation opening when the deflation piston is moved out of its closed position.

13. Wheel valve according to any of the preceding claims, wherein the inflation piston is moved out of its closed position when a pressure level at the fluid inlet is above the inflation pressure level and below the deflation pressure level, in order to arrange the wheel valve in an inflation state for increasing the pressure level in the tyre, by allowing pressurized fluid to pass from the fluid inlet to the tyre through the wheel valve, via the inflation passage, the inflation piston and the inflation opening.

14. Wheel valve according to any of the preceding claims, further comprising a non-return valve at the inflation opening for preventing fluid to flow back from the interior of the tyre into the inflation passage.

15. Wheel valve according to any of the preceding claims, further comprising a filter element at the deflation opening for preventing contaminants from entering the deflation passage from the tyre.

16. Wheel valve according to any of the preceding claims, wherein the valve housing is configured to be mounted through the rim and wherein the inflation opening, e.g. a wheel inflation opening, and the deflation opening, e.g. wheel deflation opening, project into the interior of the tyre.

17. Wheel valve according to any of the claims 1 - 15, wherein the valve housing is configured to be mounted remotely from the interior of the tyre and wherein the wheel valve further comprises a wheel fluid line, extending from the inflation opening and the deflation opening towards the interior of the tyre.

18. Wheel valve according to claim 17, wherein the valve housing further comprises a cap member, which is connected to the wheel fluid line and which comprises a cap interior that faces the inflation opening and the deflation opening, in order to fluidly connect the inflation opening and the deflation opening with the wheel fluid line.

19. Wheel valve according to claim 18, wherein the cap member is an annular cap member, which surrounds all of the wheel deflation openings.

20. Wheel valve according to claim 18 or 119, wherein the cap member comprises the inflation passage closure.

21. Wheel valve according to any of the claims 17 - 20, wherein the valve housing is configured to be mounted at a hub of the wheel, for example adjacent to a rotary transmission joint of the wheel.

22. Tyre pressure control system for controlling the tyre pressure in one or more vehicle wheels by inflating or deflating a tyre of the wheels, the system comprising: a source of pressurized fluid, configured to supply pressurized fluid, one or more wheel valves according to any of the preceding claims, each wheel valve associated with a rim of a respective vehicle wheel, wherein each of the wheel valves is, with its respective fluid inlet, fluidly connected to the source of pressurized fluid via a respective line valve, and a control unit, functionally connected to the source and the line valves and configured to control the source and the line valves in dependence of a desired pressure level in the tyres to: increase the pressure level in the tyre by subjecting the fluid inlet to a pressurized fluid at a pressure level above an inflation pressure level and below a deflation pressure level, reduce the pressure level in the tyre by subjecting the fluid inlet to a pressurized fluid at a pressure level above the deflation pressure level, and / or maintain the pressure level in the tyre by subjecting the fluid inlet to a pressurized fluid at a pressure level below the inflation pressure level.

23. Tyre pressure control system according to claim 22, wherein the control unit is configured to control the line valves sequentially, in order to inflate or deflate the tyres in sequence.

24. Tyre pressure control system according to claim 22 or 23, wherein the control unit is further configured, after controlling an increase or decrease in pressure level, to control the line valves to subject the fluid inlet to a pressure level below the inflation pressure level.

25. Tyre pressure control system according to any of the claims 22 - 24, further comprising a pressure-regulated valve at the source, which is functionally connected to the control unit and wherein the control unit is further configured to adjust the pressure level at which pressurized fluid is supplied by the source via the pressure-regulated valve.

26. Tyre pressure control system according to any of the claims 22 - 25, further comprising a pressure sensor in each of the vehicle wheels, which are functionally connected to the control unit and wherein the control unit is configured to control the source, pressure- regulated valve and / or line valves in dependence of a tyre pressure level measured with the pressure sensors.

27. Tyre pressure control system according to any of the claims 22 - 26, wherein the wheel valves are mounted through the respective rims and wherein the inflation opening, e.g. a wheel inflation opening, and the deflation opening, e.g. wheel deflation opening, of the wheel valve project into the interior of the respective tyre.

28. Tyre pressure control system according to any of the claims 22 - 26, wherein the wheel valves are mounted remotely from the interior of the respective tyre and wherein the wheel valves further each comprise a wheel fluid line, extending from the inflation opening and the deflation opening towards the interior of the respective tyre.

29. Tyre pressure control system according to claim 28, wherein the wheel valve is mounted at a hub of the respective wheel, for example adjacent to a rotary transmission joint of the wheel.

30. Method of inflating or deflating a tyre mounted on a rim of a vehicle wheel by means of a wheel valve under influence of a pressurized fluid, for example by means of a tyre pressure control system according to any of the claims 22 - 29, the method comprising the steps of: providing a wheel valve, preferably a wheel valve according to any of the claims 1 - 21 , associating the wheel valve with the rim, so that the inflation opening and deflation opening of the wheel valve are fluidly connected with an interior of the tyre, connecting the fluid inlet to a source of pressurized fluid, and one or more of the steps of: inflating the tyre by subjecting the fluid inlet to a pressurized fluid at a pressure level above an inflation pressure level and below a deflation pressure level,deflating the tyre by subjecting the fluid inlet to a pressurized fluid at a pressure level above the deflation pressure level, and / or maintaining a pressure level in the tyre by subjecting the fluid inlet to a pressurized fluid at a pressure level below the inflation pressure level.

31. Method according to claim 30, wherein the inflation pressure level is equal to or larger than the second pretension force divided by the surface area of the inflation piston surface.

32. Method according to claim 31, wherein the inflation pressure level is defined in the range between 0,3 bar and 5 bar.

33. Method according to any of the claims 30 - 32, wherein the deflation pressure level is equal to or larger than the first pretension force divided by the surface area of the deflation piston surface.

34. Method according to claim 33, wherein the deflation pressure level is at least 6 bar.

35. Method according to any of the claims 30 - 34, further comprising, after the steps of inflating and / or deflating, the step of releasing pressure at the fluid inlet below the inflation pressure level.

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