Patent Description:
Valve devices of the aforementioned type are used to regulate the air supply to pneumatic cushioning bellows of an air cushioning system for a truck. Increasing and decreasing the supply of pressurized air to the respective air cushioning bellows, or simply cushions, is controlled during driving automatically by a controller. Additionally, it is necessary to allow a manual activation and thus increase or decrease of the pressurized air in the air cushioning bellows, to adjust the vehicle level, e.g. during loading or unloading the truck. This is necessary, to e.g. adjust the level to a height of a loading ramp.

A valve device according to the aforementioned type, for example, is known from <CIT>. Therein, a valve device for an air suspension system in a vehicle is disclosed. The valve device comprises at least one cushion connection connectable to a pneumatic spring cushion of the air suspension system, a reserve connection connectable to a compressed air reserve, and a venting connection connectable to the atmosphere. The valve device moreover has an electrical actuation arrangement and a manual actuation element. A pneumatically actuable working valve arrangement is provided which, as a result of the actuation, can selectively connect the cushion connection with the reserve connection or the venting connection, or shutoff. The working valve arrangement can be actuated pneumatically both by the electrical actuation arrangement and by a pneumatic valve arrangement actuable via the manual actuation element. The working valve arrangement has at least one pneumatically actuable holding valve. According to the teaching of <CIT>, a pneumatic actuation connection of the at least one holding valve can, for the actuation thereof, be connected to the cushion connection.

Usually, such valve devices also comprise a return-to-ride valve (RTR) which on the one hand can block the position of the manual actuation element, and on the other hand is able to bring back the level of pressurized air in the cushions to the previous level, when the manual actuation element is switched to a driving position.

In one embodiment, <CIT> uses a pressure sensor for determining the pressure supplied by the valve unit to the main valve unit as a pilot pressure. By measuring this pressure, it should be determined whether the manual actuation element is in the driving position or the lifting position.

A drawback associated therewith is that even though a pressure is measured, it is not known in which position the manual actuation element is, and it is also not known whether the return-to-ride valve is operating correctly.

<CIT> discloses an air suspension system for a commercial vehicle, especially a trailer. The air suspension system enables automatic levelling control and manual lifting and lowering by the driver using an actuation organ such as a lever. A lifting-lowering valve unit may comprise a selector shaft which has cams to actuate a <NUM>/<NUM>-way valve, which can also be actuated via the actuation organ. An operating position of the actuation organ is detected by a sensor. Using an output signal of the sensor, a control unit can verify whether the actuation organ takes up a desired operating position. If this is not the case, an error message can be shown to a driver or operator, suitable control measures taken to induce the desired operating position of measures to ensure emergency operation can be taken.

A further valve device of the aforementioned type is known from <CIT>. The valve device for an air suspension in a vehicle disclosed therein comprises connectors for an air spring bellows of the air suspension system and for a compressed air supply, a ventilating connector which is connected to atmosphere, a manual operating element and a non-manual actuating element. It is possible that the valve device is adjusted both by means of the manual actuating element and by means of the non-manual actuating element in such a way that the connectors for an air spring bellows are connected to the connector for a compressed air supply or the ventilating connector. The valve device has a latching device by means of which the manual operating element can be latched in an at least one position. Moreover, the valve device has an unlocking device for unlocking the latching device which is configured in such a way that it is actuated upon actuation of the non-manual actuating element and unlocks the latching device as a result. A further similar device is disclosed in <CIT>.

It is an object of the invention to provide a valve device of the aforementioned type which makes it possible to determine whether the return-to-ride valve is operating correctly.

According to a first aspect of the invention, this problem is solved by a valve device with the features of claim <NUM>. Such a valve device for controlling a pneumatic trailer air suspension system comprises at least one cushion connection connectable to a pneumatic spring cushion of the air suspension system, a supply connection connectable to a compressed air reservoir, and a venting connection connectable to the atmosphere. The valve device has a pneumatically actuable main valve unit, an electrical pilot control unit, and a manual pilot control unit. The electrical pilot control and the manual pilot control unit are adapted for providing at least one first pilot pressure to said main valve unit, wherein said main valve unit is adapted to provide at least a cushion pressure at said cushion connection dependent on the first pilot pressure. The manual pilot control unit comprises a manually operable camshaft for controlling at least a first valve body, wherein said camshaft at least is rotatable into a driving position, a lowering position and a lifting position. According to the invention, the valve device comprises a shaft sensor for directly determining the rotational position of said camshaft.

The invention is based on the idea that it is not enough to just measure the pilot control, a pilot pressure or the pressure supplied to the cushions. Rather, the invention proposes to directly determine the rotational position of the camshaft. The camshaft is operated manually and it may happen that a driver of the truck forgets to turn the camshaft to the driving position after unloading the truck e.g. in the lowering position. In this case, by detecting the rotational position of the camshaft, a signal can be provided to the driver, and/or a control unit for informing the driver that the camshaft is not in the correct rotational position, and/or by providing at least a control signal by the control unit for e.g. braking the vehicle.

The camshaft comprises a sensor portion, said sensor portion comprising a sensible structure. The sensible structure comprises at least a first, a second, and a third surface, which are formed at different minimum distances to the shaft sensor, and the shaft sensor is adapted to measure a distance to said first, second and third surfaces. Due to the sensor portion, having the sensible structure, a direct measurement of the rotational position of the camshaft is possible. It is not necessary to indirectly measure the camshaft position by detecting a pressure. Rather, the direct mechanical rotational position is measured.

Additional assigning first, second and third surfaces to each of the three positions of the camshaft (lifting, lowering and driving position), a clear determination of the rotational position of the camshaft and the responsive mode of operation is achieved. In contrast thereto, a pressure supplied by the valve unit does not necessarily identify an exact rotational position of the camshaft.

Preferably, the sensible structure is formed in an axial end face of the camshaft. This allows the sensible structure to be distant to any cams provided at the camshaft and particularly does not affect the function of the camshaft as it is common.

In a further preferred embodiment, the shaft sensor is an optical sensor. Alternatively, the shaft sensor is a capacitive sensor, or a kinetic sensor. All three options performing the shaft sensor are suitable to detect a distance to the first, second and third surfaces and in particular do not require movable mechanical elements, as a contact sensor would require. In particular, a non-contact measurement of the distance is contemplated.

According to the invention, the valve device further comprises an electronic control unit connected to the shaft sensor and the electrical pilot control unit, wherein the electronic control unit comprises means for receiving a sensor signal from said shaft sensor indicative for one of the positions. The electronic control unit comprises means for providing at least a first corresponding switching signal to the electrical pilot control unit. In this instance, it is possible to e.g. cut off pressurized air supply to the manual pilot control unit and ultimately to the main valve unit, when the camshaft is in the lowering position or in the driving position. Thus, the actual control of the pressurized air supplied by the valve device is not only dependent on the mechanical position of the camshaft and the mechanical actuation of the valves actuable by means of a camshaft, but rather also on electrically controllable valves of the electrical pilot control unit which are switched dependent on the rotational position of the camshaft measured by the shaft sensor. Thus, in this instance, safety of the truck can be increased.

According to a further preferred embodiment, the main valve unit comprises a working valve and at least a first pneumatically actuable holding valve. The working valve is adapted to receive the first pilot pressure and dependent on the first pilot pressure provide a working pressure to the respective cushions. The holding valve preferably is adapted to cut off a pressure line for the working pressure, thus preventing pressurized air flowing out of the cushions. Thus, the holding valve actually locks the pressure within the cushions when desired.

Preferably, the main valve unit comprises at least a second pneumatically actuable holding valve. Thus, according to this embodiment, a second suspension pressure can be locked in the cushions, allowing that at least two sets of cushions can be controlled independently. One set of cushion may be assigned to a first axis and a second of cushions to a second axis, or to first and second sides of the vehicle.

Preferably, the working valve is formed as a <NUM>/<NUM>-way valve comprising a first working valve port, connected to the supply connection, a second working valve port connected to the at least first pneumatically actuable holding valve, a third working valve port connected to the venting connection and a working control port for receiving the first pilot pressure from the electrical pilot control unit and/or said manual pilot control unit.

The electrical pilot control unit preferably comprises a first pilot valve for providing a second pilot pressure to the manual pilot control unit. The first pilot valve thus may be used to cut off or supply the manual pilot control unit with the second pilot pressure which may then be further processed by the manual pilot control unit.

Moreover, it is preferred that the electrical pilot control unit comprises a second pilot valve for receiving a third pilot pressure from said manual pilot control unit and providing said first pilot pressure to said main valve unit. The first pilot pressure thus can be locked or delivered using the second pilot valve which can be controlled by the control unit. It shall be understood that the first and second pilot valves can be controlled by the control unit in particular dependent on the sensor signal from said shaft sensor.

In a further preferred embodiment, the manual pilot control unit comprises a valve housing in which said first valve body, a second valve body and said camshaft are provided. Preferably, the first and second valve bodies are individually movable in a first and second valve chamber, respectively. The first valve chamber preferably comprises a first chamber port, a second chamber port, and a third chamber port, wherein the first valve body in an idle position sets the first and second chamber port into connection, and in a lifted position sets the second and third chamber ports into connection. The second valve chamber furthermore preferably comprises a fourth chamber port, a fifth chamber port, and a sixth chamber port, wherein the second valve body in an idle position sets the fourth and fifth chamber ports into connection, and in a lifted position sets the fifth and sixth chamber ports into connection. The first and second valve bodies are pushed from the idle to the lifted position preferably by respective cams on the camshaft. Thus, by manually rotating the camshaft, the first and second valve bodies may individually be positioned in desired positions to provide the desired flow of pressurized air.

Preferably, said first chamber port is connected to the first pilot valve and receives said second pilot pressure; said second chamber port is connected to said working control port; and said third chamber port is connected to said supply connection. Moreover, it is preferred that said fourth chamber port is connected to said second pilot valve for providing the third pilot pressure to the second pilot valve, said fifth chamber port is connected to said at least first pneumatically actuable holding valve for providing a holding pressure thereat; and said sixth chamber port is connected to the or a venting connection. By this arrangement, it is possible that by rotating the camshaft, a lowering, a lifting and a driving position can be achieved and the cushions of the air suspension system can be vented or de-vented accordingly.

In a further preferred embodiment, the valve device comprises an un-lockable latching device which can be unlocked by the electrical pilot control unit. The latching device preferably is used to latch a rotational position of the camshaft for prohibiting manual rotation of the camshaft out of the latched position in one of the other positions.

Preferably, said un-lockable latching device comprises an unlocking valve connected to said first pilot valve for receiving the second pilot pressure. Thus, as long as the second pilot pressure is received, the latching device is unlocked and the camshaft can be rotated manually.

In a further preferred embodiment, the valve device comprises an electronic control device with a microprocessor and with a program memory in which a control program is stored, the electronic control device being setup for controlling an air suspension system suitable for a vehicle by means of the valve device.

The above-mentioned problem is solved in a second aspect by a method for controlling an air suspension system in a vehicle by means of a valve device according to at least one of the previously described preferred embodiments of the valve device according to the first aspect of the invention, wherein the method comprises at least the steps: receiving a sensor signal at a control device, said sensor signal being indicative for one of the positions, and providing a corresponding signal to a driver. The positions in particular comprise a lifting, a lowering and a driving position and in particular are the positions of a rotatable camshaft of the manual actuable pilot control unit.

For a more complete understanding of the invention, the invention will now be described in detail with reference to the accompanying drawings. The detailed description will illustrate and describe what is considered as a preferred embodiment of the invention. It should of course be understood that various modifications and changes in form or detail could readily be made. It is therefore intended that the invention may not be limited to the exact form and detail shown and described herein, nor to anything less than the whole of the invention as claimed herein after. Further, the features described in the description, the drawings and the claims disclosing the invention may be essential for the invention considered alone or in combination. In particular, any reference signs in the claims shall not be construed as limiting the scope of the invention. The wording "comprising" does not exclude other elements or steps. The word "a" or "an" does not exclude the plurality. The wording "a number of" items comprising also the number <NUM>, i.e. a single item, and further numbers like <NUM>, <NUM>, <NUM> and so forth. In the accompanying drawings:.

<FIG> shows a simplified version of the valve device <NUM> for controlling a pneumatic trailer air suspension system <NUM>. The trailer air suspension system <NUM> according to this embodiment comprises a first side <NUM> comprising three cushions 102a, 102b, 102c for e.g. the driver's side of the trailer, and a second side <NUM> with cushions 104a, 104b, 104c for e.g. a co-driver's side of the trailer.

The first side <NUM> comprises a first pressure distribution line <NUM> connectable to a first cushion connection <NUM> of the valve device <NUM> and the second side <NUM> comprises a second pressure distribution line <NUM> connectable to a second cushion connection of the valve device <NUM>.

The valve device <NUM> moreover comprises a supply connection <NUM> connectable to a compressed air reservoir <NUM> which usually is dedicated for the trailer air supply system <NUM> of the trailer.

The reservoir <NUM> provides a reservoir pressure pV at the supply connection. At the first and the second cushion connections <NUM>, <NUM> respective first and second cushions pC1, pC2 are provided.

For processing the reservoir pressure pV from the reservoir <NUM> to the first and second cushion pressures pC1, pC2, the valve device <NUM> comprises a main valve unit <NUM>, an electrical pilot control unit <NUM> and a manual pilot control unit <NUM> (see also <FIG>). In <FIG>, mainly the manual pilot control unit <NUM> is shown and will be described in detail.

The manual pilot control unit is switchable into three positions and comprises four connections. Thus, the manual pilot control unit can be seen as a <NUM>/<NUM>-way valve in this embodiment. It comprises a first <NUM>/<NUM>-way valve port <NUM>, a second <NUM>/<NUM>-way valve port <NUM>, a third <NUM>/<NUM>-way valve port <NUM> and a fourth <NUM>/<NUM>-way valve port <NUM>. The first <NUM>/<NUM>-way valve port <NUM> is connected to the supply connection <NUM>, the second <NUM>/<NUM>-way valve port <NUM> is connected to the first cushion connection <NUM>, the third <NUM>/<NUM>-way valve port <NUM> is connected to the second cushion connection <NUM>, and the fourth <NUM>/<NUM>-way valve port <NUM> is connected to an exhaust <NUM>.

When the manual pilot control unit <NUM> is in the idle position, as shown in <FIG>, all ports <NUM> to <NUM> are blocked and neither reservoir pressure pV from the first <NUM>/<NUM>-way valve port <NUM> is delivered, nor first or second cushion pressures pC1, pC2 may flow from the first and second cushion connections <NUM>, <NUM> in the direction of the manual pilot control unit <NUM>.

A camshaft <NUM> is provided with a handle <NUM> for rotating the camshaft <NUM>. When the camshaft <NUM> is rotated, the <NUM>/<NUM>-way valve can be brought in one of the second or third positions, which are not shown in <FIG>. In the second position, which is the lowering position, the second and third <NUM>/<NUM>-way valve ports are connected with the exhaust <NUM> via the fourth <NUM>/<NUM>-way valve port. In turn, in the third position, which is the lifting position, the second and third <NUM>/<NUM>-way valve ports <NUM>, <NUM> are connected with the first <NUM>/<NUM>-way valve port <NUM>, so that supply pressure pV is supplied to the first and second cushion connections <NUM>, <NUM> for filling the cushions 102a - 102c, 104a - 104c.

For determining in which position the camshaft <NUM> is, on the one hand two pressure sensors <NUM>, <NUM> may be used provided. A first pressure sensor <NUM> measures the pressure at the first cushion port <NUM>, and a second pressure sensor <NUM> measures the pressure at the second cushion port <NUM>. Both sensors <NUM>, <NUM> are connected to an electrical control unit <NUM> which can control the electrical pilot control unit <NUM> and which vice versa may control the manual pilot control unit <NUM> or otherwise to adjust the first and second cushion pressures pC1, pC2. When both pressure sensors <NUM>, <NUM> determine that ambient pressure is present at the first and second cushion ports <NUM>, <NUM>, this is an indicator for the <NUM>/<NUM>-way valve <NUM> being in the second position, i.e. the lowering position. However, this might not be sufficient for any pressure measured by the sensors <NUM>, <NUM>.

Therefore, according to the present disclosure, a shaft sensor <NUM> is provided for directly determining the rotational position of the camshaft <NUM>. The camshaft <NUM> comprises a sensor portion <NUM> with a sensible structure <NUM>. This will be described in more detail below with respect to <FIG> in detail.

The shaft sensor <NUM> uses a contactless sensing principle for sensing the sensible structure <NUM> for determining the rotational position of the camshaft <NUM>. The shaft sensor <NUM> provides respective first, second and third sensor signals SR1, SR2, SR3 via a first signal line <NUM> to the electrical control unit <NUM>. Moreover, via an electrical interface <NUM>, the first, second and third sensor signals SR1, SR2, SR3 can be provided for e.g. providing the driver of the respective vehicle with signals representing the rotational position of the camshaft <NUM>.

<FIG> shows a more detailed version of the layout of the valve device <NUM>. In particular, the manual pilot control unit is formed as a <NUM>/<NUM>-way valve with a first <NUM>/<NUM>-way valve port <NUM>, a second <NUM>/<NUM>-way valve port <NUM>, a third <NUM>/<NUM>-way valve port <NUM>, a fourth <NUM>/<NUM>-way valve port <NUM>, a fifth <NUM>/<NUM>-way valve port <NUM> and a sixth <NUM>/<NUM>-way valve port <NUM>. All these ports lead to respective chamber ports of valve chambers which will be described in more detail with regard to <FIG> below.

In contrast to the first embodiment of <FIG>, the embodiment shown in <FIG> also comprises a main valve unit <NUM> which will be described in detail below. In addition, also the electrical pilot control unit <NUM> is shown in greater detail than in <FIG>. In particular, the electrical pilot control unit <NUM> comprises a first pilot valve <NUM> and a second pilot valve <NUM>. Both, the first and the second pilot valves <NUM>, <NUM> are formed as <NUM>/<NUM>-way valves which are electrically controllable and receive respective first and second switching signals S1, S2 from the electrical control unit <NUM>. The first pilot valve comprises a first pilot valve port <NUM>, a second pilot valve port <NUM>, and a third pilot valve port <NUM>. In the idle, not energized state, which is shown in <FIG>, the second pilot valve port <NUM> is connected with the third pilot valve port <NUM>. When the first switching signal S1 is provided, the first pilot valve <NUM> is switched into the second state, which is not shown in <FIG>, and in which the first pilot valve port <NUM> is connected to the second pilot valve port <NUM>.

In a similar manner, the second pilot valve <NUM> comprises a fourth pilot valve port <NUM>, a fifth pilot valve port <NUM>, and a sixth pilot valve port <NUM>. Again, in the idle state, which is shown in <FIG>, the fifth pilot valve port <NUM> is connected with the sixth pilot valve port <NUM>. When the second switching signal S2 is provided, the second pilot valve <NUM> switches into the second position, which is not shown in <FIG>, and in which the fourth pilot valve port <NUM> is connected to the fifth pilot valve port <NUM>.

The first pilot valve port <NUM> is connected via a first pressure line <NUM> with the supply connection <NUM> and receives the supply pressure pV. The second pilot valve port <NUM> is connected via a second pressure line <NUM> to the second <NUM>/<NUM>-way valve port <NUM>. The third pilot valve port <NUM> is connected to an exhaust <NUM>, in this embodiment (<FIG>) a common exhaust <NUM> of the valve device <NUM>. Thus, when the first pilot valve <NUM> is in the idle position, the second <NUM>/<NUM>-way valve port <NUM> is connected to the exhaust.

In turn, the fifth pilot valve port <NUM> is connected via a third pressure line <NUM> to the sixth <NUM>/<NUM>-way valve port <NUM>. The sixth pilot valve port <NUM> is connected via a branching off line <NUM> to both, the first and second cushion connections <NUM>, <NUM> for receiving the supplied first and second cushion pressures pC1, pC2. The fourth pilot valve port <NUM> is connected via a fifth pressure line <NUM> with a working control port <NUM> of a working valve <NUM>. Thus, the working valve <NUM> in turn is again formed as a <NUM>/<NUM>-way valve. It comprises in addition to the working control port <NUM> a first working valve port <NUM>, a second working valve port <NUM> and a third working valve port <NUM>. The first working valve port <NUM> is connected via a sixth pressure line <NUM> with the supply connection <NUM> and receives the supply pressure pV. The second working valve port <NUM> is connected to the main valve unit <NUM>, and the third working valve port <NUM> is connected to an exhaust <NUM>. Thus, the working valve <NUM> in general is used to control the pressure supplied to the main valve unit <NUM>.

The main valve unit <NUM> is used to receive the supply pressure pV from the working valve <NUM> and supply the first and second cushion pressures pC1, pC2 dependent on a fourth pilot pressure p4. The fourth pilot pressure p4 is received at the main valve unit <NUM> from the third <NUM>/<NUM>-way valve port <NUM>.

In particular, the main valve unit <NUM> comprises a first pneumatically actuable holding valve <NUM>, and a second pneumatically actuable holding valve <NUM>. Both receive the fourth pilot pressure p4 and are used to regulate the first and second cushion pressures pC1, pC2, respectively, dependent on the fourth pilot pressure p4 and the pressure supplied by the working valve <NUM>.

In the idle position of the manual pilot control unit <NUM>, which is shown in <FIG>, the first and fourth <NUM>/<NUM>-way valve ports are blocked. The second <NUM>/<NUM>-way valve port is connected to the fifth <NUM>/<NUM>-way valve port, such that the second pilot pressure p2 is supplied to the fifth pressure line <NUM> and is identical to the first pilot pressure p1. Moreover, the third <NUM>/<NUM>-way valve port <NUM> is connected to the sixth <NUM>/<NUM>-way valve port <NUM>, such that the third and fourth pilot pressures p3, p4 are identical, too. This position of the manual pilot control unit <NUM> is the driving position, and the first and second cushion pressures pC1, pC2 may be controlled using the electrical pilot control unit <NUM> and the main valve <NUM> only.

The driver may also actuate the handle <NUM> for e.g. pushing the camshaft <NUM> into the lifting position which is the upper position of the manual pilot control unit <NUM> with respect to <FIG>. In this position, the first <NUM>/<NUM>-way valve port <NUM> is connected to the fifth <NUM>/<NUM>-way valve port <NUM>, so that the first pilot pressure p1 equals the supply pressure pV which is the maximum pressure. While the first pilot pressure p1 has the maximum value, also the first and second cushion pressures pC1, pC2 will become the maximum value, and in result lifting the trailer.

In turn, when the user pulls the handle <NUM> and moves the camshaft <NUM> to the lowering position, which is the lower position of the manual pilot control unit <NUM> with respect to <FIG>, the third <NUM>/<NUM>-way valve port <NUM> is set into connection with the fourth <NUM>/<NUM>-way valve port <NUM> and therefore the third <NUM>/<NUM>-way valve port <NUM> is connected to the exhaust <NUM> and the fourth pilot pressure p4 becomes the atmospheric pressure. At the same time, the second <NUM>/<NUM>-way valve port <NUM> is connected to the fifth <NUM>/<NUM>-way valve port <NUM> so that the first pilot pressure p1 equals the second pilot pressure p2. When the first pilot control valve <NUM> is in the idle state, the first pilot pressure p1 will also become the atmospheric value. Thus, in turn, the first and second pneumatically actuable holding valves <NUM>, <NUM> are opened and the working valve <NUM> is switched to the position shown in <FIG>, so that the second working valve port <NUM> is connected to atmosphere. The first and the second cushion pressures pC1, pC2 will become the atmospheric value and the trailer will lower to the maximum value.

<FIG> now shows the embodiment of <FIG>, wherein the manual pilot control unit <NUM> is shown in more detail, in particular to show how the camshaft <NUM> may operate. Identical and similar elements are shown with reference signs used in <FIG>. In so far, reference is made to the above description. In the following, in particular the differences and details of <FIG> are explained.

The manual pilot control unit <NUM> comprises a valve housing <NUM> in which the camshaft <NUM> is rotatably seated. The manual pilot control unit <NUM> moreover comprises a first valve body <NUM> and a second valve body <NUM> which are movable within respective first and second valve chambers <NUM>, <NUM>. The camshaft <NUM> comprises a first cam <NUM> and a second cam <NUM>, wherein the first cam <NUM> may push the first valve body <NUM> with respect to <FIG> upwards, and the second cam <NUM> may push the second valve body <NUM> upwards with respect to <FIG>. The first and second cams <NUM>, <NUM> are displaced with regard to their rotational position, such that it is possible to selectively push the first and the second valve bodies <NUM>, <NUM> upwards.

The first valve chamber <NUM> comprises a first chamber port <NUM>, a second chamber port <NUM>, and a third chamber port <NUM>. The second valve chamber <NUM> comprises a fourth chamber port <NUM>, a fifth chamber port <NUM>, and a sixth chamber port <NUM>. When the first valve body <NUM> is in the idle position, which is shown in <FIG>, the first valve body <NUM> sets the first and second chamber ports <NUM>, <NUM> into connection. In the lifted position, the first valve body <NUM> sets the second and third chamber ports <NUM>, <NUM> into connection. Thus, the first chamber port <NUM> equals the third <NUM>/<NUM>-way valve port <NUM>, the second chamber port <NUM> equals the fifth <NUM>/<NUM>-way valve port <NUM>, and the third chamber port <NUM> equals the first <NUM>/<NUM>-way valve port <NUM>.

In the same manner, the second valve body <NUM> in an idle position sets the fourth and fifth chamber ports <NUM>, <NUM> into connection, and in the lifted position sets the fifth and sixth chamber ports <NUM>, <NUM> into connection. Thus, the fourth chamber port <NUM> equals the sixth <NUM>/<NUM>-way valve port <NUM>, the fifth chamber port <NUM> equals the fifth <NUM>/<NUM>-way valve port <NUM>, and the sixth chamber port <NUM> equals the fourth <NUM>/<NUM>-way valve port <NUM>.

One further aspect, which can be seen in <FIG> and <FIG>, is a latching device <NUM>, comprising an unlocking valve <NUM> connected to the first pilot valve <NUM> for receiving the second pilot pressure p2. When the unlocking valve <NUM> receives the second pilot pressure p2, the latching device <NUM> unlocks the camshaft <NUM> and allows the camshaft <NUM> to be manually rotated. Thus, as long as the second pilot pressure p2 is supplied by the first pilot valve <NUM>, manually rotating the camshaft <NUM> is prohibited.

<FIG> now show different views of the camshaft <NUM>, in particular for viewing the shaft sensor <NUM> and the sensor portion <NUM>. The camshaft <NUM> comprises a rotational axis A (see <FIG>). The shaft sensor <NUM> in this embodiment is formed as an optical sensor and emits a sensor beam <NUM>. The sensor beam <NUM> is emitted substantially parallel to the rotational axis A, but with a distance E to the rotational axis A. The distance E could also be seen as an eccentric E. The eccentric E should have a value, which is high enough so that the sensor beam <NUM> may be emitted onto different surfaces 26a, 26b, 26c, as will be described with reference to <FIG>, respectively. The shaft sensor <NUM> is used to measure the distance between the shaft sensor <NUM> and the respective surface 26a, 26b, 26c of the sensible structure <NUM>.

The sensible structure <NUM> (see <FIG>) comprises a stepped surface having first, second and third surfaces 26a, 26b, 26c, which each have a different distance from the shaft sensor <NUM>, so that the distance D is different for each of the three surfaces 26a, 26b, 26c. The first surface 26a is associated with the driving position R1 (see also <FIG>), the second surface 26b is associated with the lowering position R2, and the third surface 26c is associated with the lifting position R3. It should however be understood that also a different association of the three surfaces 26a, 26b, 26c to the different positions R1, R2, R3 could be contemplated.

Claim 1:
A valve device (<NUM>) for controlling a pneumatic trailer air suspension system (<NUM>), the valve device (<NUM>) comprising:
at least one cushion connection (<NUM>, <NUM>) connectable to a pneumatic spring cushion (102a, 102b, 102c, 104a, 104b, 104c) of the air suspension system (<NUM>),
a supply connection (<NUM>) connectable to a compressed air reservoir (<NUM>), and
a venting connection (<NUM>) connectable to the atmosphere,
wherein the valve device (<NUM>) has a pneumatically actuable main valve unit (<NUM>), an electrical pilot control unit (<NUM>), and a manual pilot control unit (<NUM>), the electrical pilot control unit (<NUM>) and manual pilot control unit (<NUM>) are adapted for providing at least one first pilot pressure (p1) to said main valve unit (<NUM>), wherein said main valve unit (<NUM>) is adapted to provide at least a cushion pressure (pC) at said cushion connection (<NUM>, <NUM>) dependent on the first pilot pressure (P1),
wherein the manual pilot control unit (<NUM>) comprises a manually operatable camshaft (<NUM>) for controlling at least a first valve body (<NUM>), wherein said camshaft (<NUM>) at least is rotatable into a driving position (R1), a lowering position (R2) and a lifting position (R3),
wherein the valve device (<NUM>) has a shaft sensor (<NUM>) for directly determining the rotational position of said camshaft (<NUM>),
wherein the valve device (<NUM>) comprises an electronic control unit (<NUM>) connected to said shaft sensor (<NUM>) and said electrical pilot control unit (<NUM>), wherein the electronic control unit (<NUM>) comprises means for receiving a sensor signal (SR1, SR2, SR3) from said shaft sensor (<NUM>) indicative for one of the positions (R1, R2, R3),
wherein the electronic control unit (<NUM>) comprises means for providing at least a first switching signal (S1) corresponding to the sensor signal (SR1, SR2, SR3) to said electrical pilot control unit (<NUM>),
characterized in that said camshaft (<NUM>) comprises a sensor portion (<NUM>), said sensor portion (<NUM>) comprising a sensible structure (<NUM>), and
wherein said sensible structure (<NUM>) comprises at least a first, a second, and a third surface (26a, 26b, 26c), which are formed at different minimum distances to the shaft sensor (<NUM>) and the shaft sensor (<NUM>) is adapted to measure a distance to said first, second, and third surfaces (26a, 26b, 26c).