DE102019125061A1 - Bistable solenoid valve for an air suspension system of a vehicle and method for controlling this solenoid valve - Google Patents

Abstract

Bistable solenoid valve (2) for an air suspension system of a vehicle, by switching over an air spring (62) containing a main air volume (V0) at least one additional chamber (74) containing an additional air volume (V1) can be switched on or off, with two axially adjacent electromagnets (4, 6) and a permanent magnet (8) arranged axially between these electromagnets, within which an armature (30) is guided so as to be axially movable, the armature being brought into a first switching position with a contact on a first core (22) by energizing the first electromagnet (4) ) and by energizing the second electromagnet (6) into a second switching position with a contact with a second core (26), and in which the armature can be held in the first or second switching position without current by the permanent magnet (8) alternatively to one another is. The solenoid valve (2) is designed as a 2/2-way solenoid valve. The first core (22) is closed. The second core (26) has an axially continuous cylindrical central channel (38) for the connection of the additional chamber (74), a cylindrical ring channel (40) arranged axially on the inside coaxially around the central channel for connecting the air spring (62) and an axially end side between the Central channel (38) and the annular channel arranged valve seat (42). On the end wall (54) facing the valve seat, the armature is provided with a sealing element (56) cooperating with the valve seat.

Description

The invention relates to a bistable solenoid valve for an air suspension system of a vehicle, by switching over an air spring containing a main air volume, at least one additional chamber containing an additional air volume can be switched on or off, with two axially adjacent electromagnets and a permanent magnet arranged axially between these electromagnets, within which an armature is axially movable is guided, wherein the armature can be displaced by energizing the first electromagnet into a first switching position with a contact on a first core and by energizing the second electromagnet into a second switching position with contact on a second core, and in which the armature is displaced the permanent magnets can alternatively be held in the first or the second switching position without current. The invention also relates to a method for controlling this solenoid valve, with which the at least one additional chamber can be switched on and off in the most energy-saving and low-noise manner possible.

In air-sprung vehicles, air suspension systems with multi-chamber air springs are used, in which a softer spring characteristic of the air springs can be set by switching on additional chambers containing additional air volumes and a harder spring characteristic of the air springs can be set by switching off additional chambers containing additional volumes. The switchover of the spring detection can be triggered manually or automatically by an electronic control unit and take place simultaneously on all air springs or only on certain air springs on one side of the vehicle or on a vehicle axle. For example, the driver can switch the spring rate manually by operating a selector switch between the driving modes “Comfort” with soft spring rate, “Standard” with medium spring rate and “Sport” with hard spring rate. If the vehicle has a system for driver type recognition or for recognition of the road surface, the change between the driving modes “Comfort”, “Standard” and “Sport” can also be automated. With a dynamic adjustment of the spring characteristics, when driving through a curve, for example, the air springs of the wheels on the outside of the curve can be switched to a harder spring characteristic by switching off additional chambers containing additional air volume, thus preventing the vehicle body or body from tilting. Likewise, if the spring characteristics are dynamically adjusted when the vehicle is braked, the air springs on the front axle and when the vehicle starts up, the air springs on the rear axle can be switched to a harder spring characteristic by switching off additional chambers containing additional air volume, thus preventing vertical movement of the front of the vehicle or the rear of the vehicle become.

Such air suspension systems, in which the connection and disconnection of additional air volume contained additional chambers takes place via a 2/2-way switching valve, are for example in the DE 10 2007 050 187 B4 and the DE 10 2013 212 978 A1 described.

The switching valves are mostly designed as monostable 2/2-way solenoid valves, such as those from the DE 100 25 749 C1 and the DE 10 2011 078 102 B4 are known in the form of seat valves. Such solenoid valves are held in the de-energized state by a valve spring in a closed or open rest position and switched to an open or closed switching position by energizing an electromagnet. The solenoid valves must have relatively large flow cross-sections or nominal widths in order to enable or block the flow of correspondingly large amounts of air against different pressures, so that relatively large electromagnets and correspondingly high switching currents are required. Since the spring characteristic of the air springs set by switching over the solenoid valves is generally maintained over a longer period of time, the electromagnets must be fed with a relatively high holding current for a correspondingly long time. In a vehicle with four air springs, each of which is assigned two additional chambers containing additional air volumes, with a holding current of 1 ampere per solenoid valve, a maximum holding current of 8 amps may be required in order to maintain the set spring rate. This holding current must be controlled by the associated electronic control unit, which requires comparatively complex electronics. In addition, the heat generated in the magnet coils must be dissipated by special cooling devices. Since the holding currents are taken from an electric accumulator, they also have a negative effect on the fuel consumption of a vehicle driven by an internal combustion engine and on the range of a vehicle driven by an electric motor.

For use in air suspension systems, bistable 2/2-way solenoid valves have therefore already been developed in which an axially movable armature can be switched between two switching positions by an electromagnet that can be energized with alternating polarity and can be held in both switching positions by a permanent magnet. Such a bistable solenoid valve is, for example, from DE 10 2011 078 104 A1 known. In the DE 20 2016 103 773 U1 is a similar one Arrangement of an electromagnet and a permanent magnet for actuating a switching valve with a damping device described. The damping device consists in the armature being provided with a longitudinal bore and arranged in an oil-filled chamber. In the event of an axial displacement of the armature due to the circuit, it displaces the oil from one side of the chamber to the other side via the longitudinal bore, whereby the movement of the armature and its impact on the respective core are dampened. Disadvantageously, the last-mentioned solenoid valve and the solenoid arrangement also have a relatively large electromagnet with a correspondingly high power consumption.

On the other hand, from the DE 10 2015 005 369 A1 a 3/2-way solenoid valve is known which is provided in an electronically controllable compressed air brake system for alternating ventilation and venting of the parking brake cylinders of a parking brake circuit. The solenoid valve has two axially adjacent electromagnets and a permanent magnet arranged axially between them, within which an armature is guided in an axially movable manner. The armature can be displaced by energizing the first electromagnet into a first switching position with contact with a first core and by energizing the second electromagnet into a second switching position with contact with a second core. In addition, the armature can be held alternately in both switching positions by the permanent magnet without energizing one of the two electromagnets. Due to their arrangement, the electromagnets are designed to be comparatively compact and still exert a high tensile force on the armature when the current is applied. Due to the central arrangement of the permanent magnet, it exerts a high holding force on the armature in both switching positions.

The invention was based on the object of providing a bistable solenoid valve of a similar design with low current consumption of the electromagnets and high holding force of the permanent magnet for an air suspension system of a vehicle, by switching an air spring containing a main air volume at least one additional chamber containing an additional air volume can be switched on or off from this. In addition, a method for controlling this solenoid valve is to be specified with which the at least one additional chamber can be switched on and off as energy-saving and as quietly as possible.

The device-related object was achieved by a solenoid valve which has the features of claim 1. The method-related object is achieved by a method having the features of claim 12. Associated dependent claims in each case define advantageous developments.

Accordingly, the invention relates to a solenoid valve for an air suspension system of a vehicle, by switching over an air spring containing a main air volume, at least one additional chamber containing an additional air volume can be switched on or off, with two axially adjacent electromagnets and a permanent magnet arranged axially between these electromagnets, within which an armature is axially movable is guided, wherein the armature can be displaced by energizing the first electromagnet into a first switching position with a contact on a first core and by energizing the second electromagnet into a second switching position with contact on a second core, and in which the armature is displaced the permanent magnets can alternatively be held in the first or the second switching position without current

To solve the device-related problem, this solenoid valve also provides that the solenoid valve is designed as a 2/2-way solenoid valve, that the first core is designed to be closed, that the second core has an axially continuous cylindrical central channel for the connection of the additional chamber, has a cylindrical ring channel arranged axially on the inside coaxially around the central channel for connecting the air spring as well as a valve seat arranged axially at the end between the central channel and the ring channel, and that the armature on the end wall facing the valve seat with a circular disk-shaped or ring-cylindrical sealing element composed of a Elastomer plastic is provided.

The invention is based in particular on the DE 10 2015 005 369 A1 known bistable solenoid valve, which has two axially adjacent electromagnets and a permanent magnet arranged axially between these, within which an armature is axially movably guided. The armature can be displaced by energizing the first electromagnet into a first switching position with a contact on a first core and by energizing the second electromagnet in a second switching position with contact on a second core, as well as being de-energized by the permanent magnet in both switching positions, i.e. without energizing one of the electromagnets, durable.

Due to the closed design of the first core, the arrangement of the channels for connecting the additional chamber and the air spring as well as the valve seat in the second core and the sealing element on the armature, a bistable 2/2-way solenoid valve designed as a seat valve is created, by switching over the air spring containing the main air volume, at least one additional chamber containing an additional air volume can be switched on or off in an energy-saving and low-noise manner.

For the simplest possible production of the channels mentioned, the second core preferably consists of an outer sleeve and a bushing inserted into it. The outer sleeve has an axial central bore with the outer diameter of the annular channel and a plurality of radial bores leading axially approximately centrally into the central bore. The bushing is inserted into the central bore of the outer sleeve and is stepped radially on the outside and has the diameter of the central channel radially on the inside. Radially on the outside, the bushing has the inner diameter of the ring channel on an axial inner section reaching up to the radial bores and the outer diameter of the ring channel on an outer section adjoining it axially outward. The socket can be pressed with the outer sleeve or welded to it. In the installed state, the solenoid valve with the second core is inserted into a bore fixed to the housing with an annular groove into which the radial bores open and to which the air spring with the main air volume is connected. The additional chamber with the additional air volume is connected to the central channel.

In order to reduce the switching noises of the solenoid valve according to the invention, which are caused by the circuit-related impact of the armature on the axially inner end walls of the cores, the armature on the end wall facing the first core is expediently provided with a circular disk-shaped or ring-cylindrical damping element made of an elastomer plastic, in particular rubber, Mistake. This only dampens the switching noise when the armature reaches the first switching position, but when the armature reaches the second switching position, this is done by the sealing element, which then hits the valve seat.

The currentless holding of the armature in the open first switching position by a first holding force F _{perm-1 of} the permanent magnet, which is generated by the first permanent magnetic field PM1 of the permanent magnet, is not critical because the armature through the open solenoid valve through the on the central surface section of the valve seat side Front wall of the armature effective compressive force F _{spring of} the main air volume V ₀ or the compressive force F _{vol of} the additional air volume V _{1 is} loaded in the opening sense (F _perm-1 > - F _spring ).

In order to be able to release the armature when switching from the open first switch position to the closed second switch position from the system on the first core and move it in the direction of the second core, such a design and arrangement of the second electromagnet is required that the armature through the Electromagnetic field EM2 of the energized second electromagnet from the open first switching position against the first holding force F _{perm-1 of} the permanent magnet and against the compressive force F _{spring of} the main air volume V ₀ and can be moved in the direction of the second switching position that closes the solenoid valve (F _mag-2 > F _perm-1 + Fspring).

In order to be able to keep the armature currentless on the valve seat of the second core, such a design and arrangement of the permanent magnet is necessary that the armature is counteracted by a second permanent magnetic field PM2 of the permanent magnet against the difference between the compressive force F _{vol of} the additional air volume V ₁ and the compressive force F. _{spring of} the main air volume V ₀ without current, that is to say without energizing one of the electromagnets, can be maintained in the closed second switching position (F _perm-2 > F _vol - Fspring).

In order to be able to release the armature when switching from the closed second switch position to the open first switch position from the system on the valve seat of the second core and to be able to move it in the direction of the first core, such a design and arrangement of the first electromagnet is required that the Armature by the electromagnetic field EM1 of the energized first electromagnet from the closed second switching position against the second holding force F _{perm-2 of} the permanent magnet and the difference between the compressive force F _{spring of} the main air volume V ₀ and the compressive force F _{vol of} the additional air volume V ₁ releasably and in the direction of the opened first switching position is displaceable (F _mag-1 > F _perm-2 - (F _vol - F _spring )).

In order to increase the damping effect of the damping element on the armature side when the armature reaches the open first switching position, the inner end wall of the first core is advantageously convexly curved in the contact area with the armature's damping element. Due to the curvature of the inner end wall, the damping element of the anchor first hits the end wall in the middle and is then elastically deformed over a certain axial path, increasing the contact surface with the end wall, whereby the kinetic energy of the anchor is reduced and the impact shock is more strongly damped.

Since the gap between the relevant end wall of the armature and the axially inner end wall of the second core in the second switching position can be kept relatively small at about 0.3 mm in order to generate a strong electric and permanent magnetic field EM2, PM2 To achieve the second electromagnet and the permanent magnet, the valve seat can press into the sealing body over time due to the circuit-related impact of the armature. As a result, the gap can be bridged and an undesired switching noise can be caused by a metallic contact of the armature with the inner end wall of the second core. To prevent this, according to an advantageous development of the invention, the armature is provided on the end wall facing the second core with several ring segment-shaped damping elements made of an elastomeric material, for example rubber, which are spaced radially from the sealing element of the armature and circumferentially from one another for the unimpeded flow of compressed air are arranged.

To compensate for a static pressure difference between the main air volume and the additional air volume that occurs when the vehicle is loaded or unloaded, the armature is preferably provided with a central through-hole into which a throttle element is inserted, which has an axial throttle bore.

The throttle element is preferably designed as a sheet metal disk which is integrated into the damping element of the core, in particular vulcanized into it, and in which the throttle bore was produced by laser drilling.

In order to avoid compensating for a dynamic pressure difference between the main air volume and the additional air volume caused by driving the vehicle, the diameter of the throttle bore is made relatively small and is in the range between 0.1 mm and 0.2 mm, including the stated range limits.

To solve the process-related problem, namely to control a bistable solenoid valve with the features of at least one of the device claims mentioned, it is provided that a ramp-shaped voltage pulse is fed into the solenoid of the switching solenoid to switch the solenoid valve. This advantageously limits the level of a counterforce generated by induction in the magnet coil of the non-switching electromagnet.

The duration T _{S of} the voltage pulse is preferably longer than half the period T _E / 2 of the natural frequency of the chassis of the vehicle, so that when the chassis vibrates, the zero crossing is within the voltage pulse and the solenoid valve can therefore be switched over safely.

In order to be able to make the electromagnets weaker and thus also more compact and power-saving, the control of the solenoid valve according to the invention preferably provides that at least at the beginning of a switchover of the solenoid valve, a counterforce compensating for the holding force of the permanent magnet is generated by a corresponding energization of the non-switching electromagnet. _{The current I K} fed into the compensating electromagnet is approximately a quarter of the current I _S fed into the switching electromagnet (I _K ≈ ¼ I _S ).

To further reduce the switching noise of the solenoid valve, a braking force F _{br, which dampens} the impact of the armature on the associated core, is generated by a corresponding energization of the non-switching electromagnet towards the end of a switchover of the solenoid valve before the relevant switching position is reached.

Since for this purpose the information about the setting position or about the setting travel of the armature must be available directly, i.e. in real time, it is preferably provided that the distance between the armature and the relevant core is not determined by an evaluation of a movement of the armature in the solenoid switching electromagnet induced voltage U _{ind is} determined, and that the braking force Fbr is switched on when a predetermined distance of the armature from the core is reached by a corresponding energization of the non-switching electromagnet.

According to a further development of the invention, the distance between the armature and the relevant core is determined by means of an integration circuit of an operational amplifier, at the input of which the induced voltage U _{ind is} applied and at the output of which an integrated voltage U _{cut is} tapped. _{The voltage U ind} induced in the magnet coil of the non-switching electromagnet is proportional to the actuating speed of the armature. Accordingly, the output voltage U _cut obtained by integrating the induced voltage U _{ind is} proportional to the travel of the armature and can thus be used to determine the position of the armature. The distance between the armature and the relevant core is then obtained by subtracting the determined travel from the possible total travel of the armature.

The switching of the solenoid valve from the closed second switch position to the open first switch position is preferably carried out when the difference between the pressure force F _{vol of} the additional air volume V ₁ and the pressure force F _{spring of} the main air volume V _{0 is} just positive (F _vol - F _spring > 0), since the switchover is then supported by this force difference F _vol - F _spring and only one lower actuating force F _mag-1 , F _{mag-2 of} the switching electromagnet is required.

For the same reason, the switchover of the solenoid valve from the open first switch position to the closed second switch position is preferably carried out when the difference between the compressive force F _{vol of} the additional air volume V ₁ and the compressive force F _{spring of} the main air volume V _{0 is} just negative (F _vol - F _jump <0).

In the event that the holding force F _perm-1 , F _{perm-2 of} the permanent magnets in the solenoid valves of at least some air springs of a vehicle is not sufficient to hold the armature in their switching position, it can be provided that the holding force F _perm-1 , F _perm-2 the permanent magnets in the solenoid valves of at least some air springs of a vehicle is supported, if necessary, by a corresponding energization of the electromagnets adjacent to the respective armature.

It can also be provided that the holding force F _{perm-2 of} the permanent magnets in the closed second switching position of the armature when cornering at the solenoid valves of the air springs on the inside of the curve is supported by a corresponding energization of the neighboring electromagnets, because the armature in question is supported by the difference in the pressure forces F _vol - F _{jump are} then loaded in the opening sense.

When driving on a bad route with changing loads on the armature due to the difference in pressure forces F _vol - F _{spring, it} can be provided that the holding force F _perm-1 , F _{perm-2 of} the permanent magnets is applied to the solenoid valves of all air springs regardless of the switching position of the armature a corresponding energization of the neighboring electromagnets is supported.

• 1 eine Basisausführung eines die Merkmale der Erfindung aufweisenden Magnetventils in einem Längsmittelschnitt,
• 1a die Kraftverhältnisse in dem Magnetventil gemäß 1 in einer ersten Schaltstellung,
• 1b die Kraftverhältnisse in dem Magnetventil gemäß 1 bei einer Umschaltung aus der ersten Schaltstellung in eine zweite Schaltstellung,
• 1c die Kraftverhältnisse in dem Magnetventil gemäß 1 in der zweiten Schaltstellung,
• 1d die Kraftverhältnisse in dem Magnetventil gemäß 1 bei einer Umschaltung aus der zweiten Schaltstellung in die erste Schaltstellung,
• 2 eine erste Weiterbildung des Magnetventils gemäß 1 in einem Längsmittelschnitt,
• 2a ein Magnetventil ähnlich dem gemäß 1 in einem Querschnitt,
• 3 eine zweite Weiterbildung des Magnetventils gemäß 1 in einem Längsmittelschnitt,
• 4 eine elektrisches Schaltschema des Magnetventils gemäß 1 bei einer Umschaltung aus der ersten Schaltstellung in die zweite Schaltstellung,
• 4a den zeitlichen Verlauf der in die Magnetspule des schaltenden Elektromagneten eingesteuerten Schaltspannung in einem Diagramm,
• 4b den zeitlichen Verlauf der in die Magnetspule des nicht schaltenden Elektromagneten induzierten Spannung in einem Diagramm,
• 4c den zeitlichen Verlauf der in die Magnetspule des nicht schaltenden Elektromagneten induzierten Spannung mit einer Ermittlung des Stellweges des Ankers, und
• 4d eine Schaltungsanordnung zur Ermittlung des Stellweges des Ankers.

The invention is explained in more detail below with reference to three exemplary embodiments shown in the accompanying drawing. In the drawing shows

• 1 a basic version of a solenoid valve having the features of the invention in a longitudinal center section,
• 1a the force relationships in the solenoid valve according to 1 in a first switch position,
• 1b the force relationships in the solenoid valve according to 1 when switching from the first switch position to a second switch position,
• 1c the force relationships in the solenoid valve according to 1 in the second switch position,
• 1d the force relationships in the solenoid valve according to 1 when switching from the second switch position to the first switch position,
• 2 a first development of the solenoid valve according to 1 in a longitudinal center section,
• 2a a solenoid valve similar to that according to 1 in a cross section,
• 3 a second development of the solenoid valve according to 1 in a longitudinal center section,
• 4th an electrical circuit diagram of the solenoid valve according to 1 when switching from the first switch position to the second switch position,
• 4a the timing of the switching voltage applied to the solenoid of the switching electromagnet in a diagram,
• 4b the time course of the voltage induced in the solenoid of the non-switching electromagnet in a diagram,
• 4c the time course of the voltage induced in the solenoid of the non-switching electromagnet with a determination of the travel of the armature, and
• 4d a circuit arrangement for determining the travel of the armature.

In the 1 Basic version of the solenoid valve according to the invention shown in a longitudinal center section 2 has two axially adjacent electromagnets 4th , 6th and a permanent magnet axially arranged between them 8th on. The solenoids 10 , 12th the electromagnet 4th , 6th are each on a spool carrier 14th , 16 arranged. Between the coil carriers 14th , 16 is the permanent magnet 8th with a radial arrangement of its magnetic poles N , S. arranged. With the permanent magnet 8th it can be a single magnet or a plurality of partial magnets distributed around the circumference with a corresponding pole arrangement.

The electromagnets 4th , 6th and the permanent magnet 8th are in a hollow cylindrical yoke 18th arranged that a yoke pot 18a and a yoke cover 18b includes. In a central hole 20th of the yoke cover 18b is a first core 22nd inserted and with the yoke cover 18b pressed. In one in the bottom of the yoke pot 18a located central hole 24 is a second core 26th inserted and with the yoke pot 18a pressed. Inside the electromagnet 4th , 6th and the permanent magnet 8th is an anchor guide sleeve 28 arranged in which an anchor 30th is guided axially movable.

The Indian 1 first core shown on the left 22nd is closed and has a level, axially inner end wall 32 on. The second core 26th has an axially continuous cylindrical central channel 38 , one axially inside coaxially over the central channel 38 arranged cylindrical ring channel 40 , and axially end inside one between the central channel 38 as well as the ring channel 40 trained valve seat 42 on.

For the simple production of the mentioned channels 38 , 40 is the second core 26th from an outer sleeve 34 and a socket inserted into it 36 . The outer sleeve 34 has an axial central bore 44 with the outer diameter of the ring channel 40 and several axially approximately in the middle of the central bore 44 leading radial bores 46 on. The socket 36 is in the central hole 44 the outer sleeve 34 used and designed stepped radially on the outside, and it has the diameter of the central channel radially on the inside 38 on. The socket faces radially on the outside 36 on one up to the radial holes 46 reaching axial inner section 48 the inner diameter of the ring channel 40 and at an adjoining axial outer section 50 the outer diameter of the ring channel 40 on. The socket 36 can with the outer sleeve 34 be pressed or welded to this.

The anchor 30th is on at its the second core 26th facing front wall 54 with one with the valve seat 42 cooperating circular disk-shaped sealing element 56 made of an elastomeric material, for example rubber. This sealing element 56 serves to close the central channel 38 on the valve seat 42 as well as when switching from the open first switch position to the closed second switch position for damping the impact of the armature 30th onto the axially inner end wall of the second core 26th . On the first core 22nd facing front wall 52 of the anchor 30th is a circular disk-shaped damping element 58 made of an elastomeric material, for example made of rubber, which, when switched from the closed second switch position to the open first switch position, is used to dampen the impact of the armature 30th on the inner front wall 32 of the first core 22nd serves.

The solenoid valve 2 is inserted in the assembled state in a bore provided with an annular groove in a housing (not shown). The radial bores open into the annular groove of the housing bore 46 of the second core 26th and a connection hole for connecting a connection line 60 one a main volume of air V ₀ containing air spring 62 . For sealing the radial bores 46 and the annular groove is axially on both sides in an annular groove 64 , 66 the outer sleeve 34 inserted O-ring 68 , 70 intended. An axial connection hole in the housing that goes into the central channel 38 of the second core 26th is used to connect a connection cable 72 one an additional air volume V ₁ containing additional chamber 74 intended.

By energizing the first electromagnet 4th becomes a magnetic pull F _mag-1 on the anchor 30th effective through which the anchor 30th from the in 1 shown second switching position in which the armature 30th with the sealing element 56 on the valve seat 42 and the solenoid valve 2 is thus closed, shifted axially to the left into a first switching position in which the armature 30th with the damping element 58 on the inner front wall 32 of the first core 22nd and the solenoid valve 2 is thus open. By energizing the second electromagnet 6th becomes an opposing magnetic pull F _mag-2 on the anchor 30th effective by which the anchor 30th from the first switch position back to the in 1 shown second switching position is shifted axially. In both switching positions, the permanent magnet 8th a magnetic holding force F _perm-1 , F _perm-2 on the anchor 30th effective by which the anchor 30th in each case currentless, that is, without a current supply to one of the two electromagnets 4th , 6th , is held in the first or the second switching position.

In the following, the 1a to 1d the force relationships in the two switching positions of the solenoid valve 2 explained.

In 1a is the anchor 30th in the first switching position, in which the armature 30th with the sealing element 56 from the valve seat 42 is lifted and with the damping element 58 on the axially inner end wall 32 of the first core 22nd is applied. The solenoid valve 2 is thus open, and the additional air volume V ₁ containing additional chamber 74 is the main volume of air V ₀ containing air spring 62 switched on. It is true that it stands between the first core 22nd and the anchor 30th located pressure chamber due to the connection via the annular gap between the armature guide sleeve 28 and the anchor 30th also under the pressure of the two air volumes V ₀ , V ₁ . Since the air pressure due to the application of the damping element 58 on the inner front wall 32 first core 22nd but there only on a radially outer annular surface of the armature 30th is effective, there is a resulting compressive force F _spring = F _{vol of} the air volume V ₀ , V ₁ who have favourited the anchor 30th burdened in the opening sense. Around the anchor 30th de-energized in the first switching position according to 1a being able to hold is therefore a relatively small holding force F _perm-1 required, which by the first permanent magnetic field shown with a dash-dot line PM1 of the permanent magnet 8th is produced.

In the 1b is the anchor 30th still in the first switch position, but it should close the solenoid valve 2 from the first switch position according to the one shown Direction arrow 76 moved from left to right into the second switching position. The second electromagnet is used for this purpose 6th accordingly energized and generated by means of the electromagnetic field shown with a dashed line EM2 that force F _mag-2 through which the anchor 30th is pulled into the second switch position. The second electromagnet 6th is designed and arranged such that the anchor 30th by the electromagnetic field EM2 of the energized second electromagnet 6th from the first switch position against the holding force F _perm-1 of the permanent magnet n and against the pressure force of the main air volume F _jump released and shifted to the right in the direction of the second switching position (F _mag-2 > F _perm-1 + F _spring ).

In 1c is the anchor 30th in the second switching position, in which the armature 30th with the sealing element 56 on the valve seat 42 of the second core 26th is applied. The solenoid valve 2 is thus closed, and the additional air volume V ₁ containing additional chamber 74 is the main volume of air V ₀ containing air spring 62 Cut. Around the anchor 30th de-energized on the valve seat 42 of the second core 26th to be able to hold is the permanent magnet 8th designed and arranged such that the anchor 30th by the second holding force F _perm-2 of the permanent magnet 8th , which by the drawn in second permanent magnetic field PM2 of the permanent magnet 8th is generated against the difference from the compressive force F _vol the additional air volume V ₁ and the pressure force F _jump of the main air volume V ₀ can be maintained in the second switching position (F _perm-2 > F _vol - F _spring ).

In 1d is the anchor 30th still in the second switch position, but it should open the solenoid valve 2 from the second switch position according to the direction arrow 78 be moved to the first switch position to the left. The first electromagnet is used for this purpose 4th accordingly energized and generated by the drawn electromagnetic field EM1 the actuating force F _mag-1 through which the anchor 30th is pulled to the first switch position. The first electromagnet 4th is designed and arranged such that the anchor 30th by the electromagnetic field EM1 of the energized first electromagnet 4th from the second switching position against the second holding force F _perm-2 of the permanent magnet 8th and the difference between the compressive force F _jump of the main air volume V ₀ and the pressure force F _vol the additional air volume V ₁ is releasable and displaceable in the direction of the first switching position (F _mag-1 > F _perm-2 - (F _vol - F _spring )).

One in the longitudinal center section according to 2 and in cross section AA according to 2a depicted first development of a solenoid valve having the features of the invention 2 ' differs from the basic version of the solenoid valve 2 according to 1 first by the fact that the inner end wall 32 ' of the first core 22nd in the contact area with the assigned damping element 58 of the anchor 30th is convex. It is also provided that the anchor 30th on that of the second core 26th facing front wall 54 with several ring segment-shaped damping elements 80 is made of an elastomeric plastic, in particular rubber, which is provided radially from the sealing element 56 of the anchor 30th and are arranged circumferentially spaced from one another. Due to the curvature of the inner front wall 32 ' of the first core 22nd hits the damping element 58 of the anchor 30th first in the middle of the front wall 32 ' and is then over a certain axial path while increasing the contact area with the end wall 32 ' elastically deformed, reducing the kinetic energy of the anchor 30th reduced and the impact shock is more strongly cushioned. Through the damping elements 80 becomes a metallic contact of the anchor 30th with the inner end wall of the second core 26th avoided, which by pressing in the valve seat 42 into the seal body 56 of the anchor 30th and a resulting bridging between the end walls 54 of the anchor 30th and the second core 26th provided air gap of very small width (for example 0.3 mm) can be caused. Through the distances between the respective damping elements 80 from the centrally located sealing element 56 as well as among each other, an unhindered flow of compressed air is guaranteed.

This in 3 pictured solenoid valve 2 " differs from the basic version of the solenoid valve 2 according to 1 in that the anchor 30 ' with a central through hole 82 is provided which is close to the first core 22nd on a throttle element 84 with an axial throttle bore 86 flows out. The through hole 82 and the throttle element 84 with the throttle bore 86 serve to compensate for a static pressure difference between the main air volume V ₀ and the additional air volume V ₁ which occurs when the vehicle is loaded or unloaded. The throttle element 84 is designed as a sheet metal disc which is inserted into the damping element 58 ' of the core 30th is vulcanized, and in which the throttle bore 86 with a diameter in the range between 0.1 mm and 0.2 mm including the stated range limits is incorporated by laser drilling. With this version of the solenoid valve 2 " are the sealing element 56 ' and the damping element 58 ' due to the through hole 82 ring-cylindrical.

Additionally or alternatively to the use of damping elements 58 , 58 ' , 80 can be caused by the armature impact caused by the circuit 30th on the two cores 22nd , 26th also by a corresponding energization of the non-switching electromagnet 4th , 6th are attenuated, by which one on the armature towards the end of the switching process 30th effective braking force Fbr is produced. This procedure is described below using the 4th as well as 4a to 4d exemplarily for a circuit of the solenoid valve 2 explained from the open first switch position to the closed second switch position.

Around the anchor 30th from the first switch position in the direction of the in 4th direction arrow 76 To move to the second switch position is in the solenoid 12th of the second electromagnet 6th in the timing diagram U _S (t) of 4a shown ramp-shaped voltage pulse U _S fed in. By moving the anchor 30th gets into the solenoid 10 of the first electromagnet 4th a voltage Uind is induced which is proportional to the speed of the armature 30th increases, and its course in the time diagram U _ind (t) the 4b is shown. The course of the induced voltage U _ind in 4b it can be seen at the point of the voltage peak in the diagram that the anchor 30th at this point the second core 26th or the valve seat 42 reached.

By evaluating the course of the induced voltage U _ind now becomes the distance of the anchor 30th from the second core 26th intended to be timely before the anchor hit 30th on the second core 26th by a corresponding energization of the first electromagnet 4th one on the anchor 30th effective braking force F _br to turn on. For this purpose, the travel of the armature 30th or its distance from the second core 26th by integrating the into the solenoid 10 of the first electromagnet 4th induced voltage U _ind determined as it is in the timing diagram U _ind (t) in the 4c is shown. When the switching process starts, the induced voltage is also integrated U _ind started. By integrating the induced voltage U _ind results according to 4d an output voltage U _cut , the amount of which is proportional to the travel of the armature 30th is. At the time t ₁ is the position of the armature 30th reached along its travel from which the voltage Ubr to generate the braking force Fbr into the solenoid 10 of the first electromagnet is fed. The peak of the voltage curve U _ind (t) at the point in time t ₂ marks the impact of the anchor 30th on the second core 26th and thus reaching the second switch position.

beschrieben, wobei mit R der Widerstandswert der ohmschen Widerstände und mit C die Kapazität des Kondensators bezeichnet sind. Um den Abstand des Ankers 30 von dem zweiten Kern 26 zu bestimmen, muss der durch die Integration ermittelte Stellweg nur von dem maximal möglichen Gesamtstellweg des Ankers 30 subtrahiert werden.The integration of the induced voltage U _ind is preferably done with an in 4d shown integration circuit 88 of an operational amplifier 90 at which the induced voltage U _ind on the ones with ohmic resistors R. provided input of the operational amplifier 90 is applied between the input and the output of the operational amplifier 90 a capacitor C. is connected in parallel, and at the output of the operational amplifier 90 the integrated voltage U _cut is tapped. The corresponding integration process is then given by the formula $${\text{U}}_{\text{cut}}=1/\left(\text{R.}\ast \text{C.}\right){\displaystyle \underset{0}{\overset{\text{t}}{\int }}{\text{U}}_{\text{ind}}\ast \text{German}}$$

described, with R the resistance of the ohmic resistors and C the capacitance of the capacitor are designated. To the distance of the anchor 30th from the second core 26th to determine, the travel determined by the integration only needs to be based on the maximum possible total travel of the armature 30th be subtracted.

List of reference symbols

2, 2 ', 2' '

magnetic valve

4th

First electromagnet

6th

Second electromagnet

8th

Permanent magnet

10

First solenoid

12th

Second solenoid

14th

First bobbin

16

Second bobbin

18th

yoke

18a

Yoke pot

18b

Yoke cover

20th

Central bore

22nd

First core

24

Central bore

26th

Second core

28

Anchor guide sleeve

30, 30 '

anchor

32, 32 '

Inner front wall

34

Outer sleeve

36

Rifle

38

Central channel

40

Ring channel

42

Valve seat

44

Central bore

46

Radial bore

48

Interior section

50

Outer section

52

First end wall of the anchor

54

Second end wall of the anchor

56, 56 '

Sealing elements

58, 58 '

Damping elements

60

Connecting cable

62

Air spring

64

First ring groove

66

Second ring groove

68

First O-ring

70

Second O-ring

72

Connecting cable

74

Additional chamber

76

Direction arrow

78

Direction arrow

80

Damping element

82

Through hole

84

Throttle element, sheet metal disc

86

Throttle bore

88

Integration circuit

90

Operational amplifier

C.

Capacitor, capacitance

EM1

Electromagnetic field from electromagnet 4th

EM2

Electromagnetic field from electromagnet 6th

Fbr

Braking force of an electromagnet 4th , 6th

F _comp

Counterforce of an electromagnet 4th , 6th

F _mag-1

Actuating force, tensile force of the electromagnet 4th

F _mag-2

Actuating force, tensile force of the electromagnet 6th

F _perm-1

First holding power of permanent magnet 8th

F _perm-2

Second holding force from permanent magnet 8th

F _jump

Compression force of main air volume V ₀

F _vol

Pressure force of additional air volume V ₁

I _K

Current, compensation current

I _S

Current, switching current

N

Magnetic pole, magnetic north pole

PM1

First permanent magnetic field from permanent magnet 8th

PM2

Second permanent magnetic field from permanent magnet 8th

R.

Ohmic resistance

S.

Magnetic pole, magnetic south pole

t

time

t ₁

First point in time

t ₂

Second point in time

T _E

Period of the natural frequency

T _S

Duration of the voltage pulse

Ubr

Voltage, brake voltage

U _cut

Integrated voltage, output voltage

U _ind

Induced voltage, input voltage

U _S

Voltage, switching voltage

V ₀

Main air volume

V ₁

Additional air volume

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102007050187 B4 [0003]
• DE 102013212978 A1 [0003]
• DE 10025749 C1 [0004]
• DE 102011078102 B4 [0004]
• DE 102011078104 A1 [0005]
• DE 202016103773 U1 [0005]
• DE 102015005369 A1 [0006, 0011]

Claims (23)

Bistable solenoid valve (2, 2 ', 2 ") for an air suspension system of a vehicle, by switching over an air _{spring (62) containing a main air volume (V 0} ) at least one additional chamber (74) containing an additional air volume (V ₁ ) can be switched on or off, with two axially adjacent electromagnets (4, 6) and a permanent magnet (8) arranged axially between these electromagnets (4, 6), within which an armature (30, 30 ') is guided in an axially movable manner, the armature (30, 30') can be displaced by energizing the first electromagnet (4) into a first switching position with contact with a first core (22) and by energizing the second electromagnet (6) into a second switching position with contact with a second core (26), and in which the armature (30, 30 ') can alternatively be held in the first or second switching position without current by the permanent magnet (8), characterized in that the solenoid valve (2, 2', 2 ") is designed as a 2/2-way solenoid valve, that the first core (22) is designed to be closed, that the second core (26) has an axially continuous cylindrical central channel (38) for connecting the additional chamber (74), one axially inside has a cylindrical ring channel (40) arranged coaxially around the central channel (38) for connecting the air spring (62) and a valve seat (42) arranged axially at the end between the central channel (38) and the ring channel (40), and that the armature (30) is provided on the end wall (54) facing the valve seat (42) with a circular disk-shaped or ring-cylindrical sealing element (56, 56 ') made of an elastomeric plastic which interacts with the valve seat (42). Solenoid valve after Claim 1 , characterized in that the second core (26) consists of an outer sleeve (34) and a bushing (36) inserted into it, that the outer sleeve (34) has an axial central bore (44) with the outer diameter of the annular channel (40) and has a plurality of radial bores (46) connected axially centrally to the central bore (44), that the bush (36) is inserted into the central bore (44) of the outer sleeve (34), that the bush (36) is stepped radially on the outside and radially on the inside has the diameter of the central channel (38), and the bushing (36) has the inner diameter of the annular channel (40) radially on the outside on an axial inner section (48) reaching up to the radial bores (46) and on an outer section adjoining it axially outward (50) has the outer diameter of the annular channel (40). Solenoid valve after Claim 1 or 2 , characterized in that the armature (30, 30 ') is provided on the end wall (52) facing the first core (22) with a circular disk-shaped or ring-cylindrical damping element (58, 58') made of an elastomeric plastic. Solenoid valve according to one of the Claims 1 to 3 , characterized in that the second electromagnet (6) is designed and arranged such that the armature (30, 30 ') by the electromagnetic field (EM2) of the energized second electromagnet (6) from the first switching position against the holding force (F _{perm- 1} ) of the permanent magnet (8) and the pressure force (F _spring ) of the main air volume (V ₀ ) is releasable and displaceable in the direction of the second switching position (F _mag-2 > F _perm-1 + F _spring ). Solenoid valve according to one of the Claims 1 to 4th , characterized in that the permanent magnet (8) is designed and arranged in such a way that the armature (30, 30 ') is counteracted by the second permanent magnetic field (PM2) of the permanent magnet (8) against the difference from the pressure force (F _vol ) of the additional air volume ( V ₁ ) and the pressure force (F _spring ) of the main air volume (V ₀ ) can be maintained in the second switching position without current (F _perm-2 > F _vol - F _spring ). Solenoid valve according to one of the Claims 1 to 5 , characterized in that the first electromagnet (4) is designed and arranged in such a way that the armature (30, 30 ') by the electromagnetic field (EM1) of the energized first electromagnet (4) from the second switching position against the second holding force (F _{perm -2} ) of the permanent magnet (8) and the difference between the compressive force (F _spring ) of the main air volume (V ₀ ) and the compressive force (F _vol ) of the additional air volume (V ₁ ) can be released and moved in the direction of the first switching position (F _{mag -1} > F _perm-2 - (F _vol - F _spring )). Solenoid valve according to one of the Claims 3 to 6th , characterized in that the inner end wall (32 ') of the first core (22) is convexly curved in the contact area with the damping element (58) of the armature (30). Solenoid valve according to one of the Claims 1 to 7th , characterized in that the armature (30) is provided on the end wall (54) facing the second core (26) with several ring segment-shaped damping elements (80) made of an elastomeric plastic, which are radially separated from the sealing element (56) of the armature (30) and are arranged circumferentially spaced from one another. Solenoid valve according to one of the Claims 1 to 8th , characterized in that the armature (30 ') is provided with a central through bore (82) into which a throttle element (84) is inserted, which has a throttle bore (86). Solenoid valve after Claim 9 , characterized in that the throttle element (84) is designed as a sheet metal disc which is integrated into the damping element (58 ') of the armature (30'), the throttle bore (86) being produced by laser drilling. Solenoid valve after Claim 9 or 10 , characterized in that the diameter of the throttle bore (86) has a diameter between 0.1 mm and 0.2 mm, including the range limits. Method for controlling a bistable solenoid valve according to one of the Claims 1 to 11 , characterized in that to switch over the solenoid valve (2, 2 ', 2 "), a ramp-shaped voltage pulse is fed into the solenoid coil (10, 12) of the switching electromagnet (4, 6). Procedure according to Claim 12 , characterized in that the duration (T _S ) of the voltage pulse is longer than half the period (T _E / 2) of the natural frequency of the chassis of the vehicle. Method according to one of the Claims 1 to 12th , characterized in that at least at the beginning of a switchover of the solenoid valve (2, 2 ', 2 "), a _{counterforce (F comp ) compensating for the holding force (F perm-1} , F _perm-2 ) of the permanent magnet (8) by a corresponding current supply of the non-switching electromagnet (4, 6) is generated. Procedure according to Claim 14 , characterized _{in that the current I K} fed into the compensating electromagnet (4, 6) is _{a quarter of the current I S} fed into the switching electromagnet (6, 4) (I _K ≈ ¼ I _S ). Method according to one of the Claims 12 to 15th , characterized in that towards the end of a switchover of the solenoid valve (2) before the relevant switching position is reached, a braking force (F _br ) which dampens the impact of the armature (30) on the associated core (26) by a corresponding energization of the non-switching electromagnet ( 4) is generated. Procedure according to Claim 16 , characterized in that the distance between the armature (30) and the relevant core (26) is determined by evaluating a voltage (U _ind ) induced by the movement of the armature (30) in the magnet coil (10) of the non-switching electromagnet (4) is determined, and that the braking force (F _br ) is switched on when a predetermined distance between the armature (30) and the relevant core (26) is reached by a corresponding energization of the non-switching electromagnet (4). Procedure according to Claim 17 , characterized in that the distance of the armature (30) from the relevant core (26) is determined by means of an integration circuit (88) of an operational amplifier (90), to whose input the induced voltage (U _ind ) is applied and to whose output a travel proportional Voltage (U _cut ) is tapped. Method according to one of the Claims 1 to 18th , characterized in that the solenoid valve (2, 2 ', 2 ") is switched from the second switching position to the first switching position when the difference between the pressure force (F _vol ) of the additional air volume (V ₁ ) and the pressure force ( F _spring ) of the main air volume (V ₀ ) is just positive (F _vol - F _spring > 0). Method according to one of the Claims 1 to 19th , characterized in that the switching of the solenoid valve (2, 2 ', 2 ") from the first switching position to the second switching position is carried out when the difference between the pressure force (F _vol ) of the additional air volume (V ₁ ) and the pressure force ( F _spring ) of the main air volume (V ₀ ) has just become negative (F _vol - F _spring <0). Method according to one of the Claims 1 to 20th , characterized in that the holding force (F _perm-1 , F _perm-2 ) of the permanent magnets (8) in the solenoid valves (2, 2 ', 2 ") of at least some air springs (62) of a vehicle, if necessary, by a corresponding energization of the respective armature (30, 30 ') adjacent electromagnets (4, 6) is supported. Procedure according to Claim 21 , characterized in that the holding force (F _perm-2 ) of the permanent magnets (8) in the second switching position of the armature (30, 30 ') when the vehicle is cornering at the solenoid valves (2, 2', 2 ") of the air springs on the inside of the curve ( 62) is supported by a corresponding energization of the neighboring electromagnets (4, 6). Procedure according to Claim 21 and 22nd , characterized in that the holding force (F _perm-1 , F _perm-2 ) of the permanent magnets (8) regardless of the switching position of the armature (30, 30 ') when traveling a poor distance at the solenoid valves (2, 2', 2 ") of all air springs (62) is supported by a corresponding energization of the adjacent electromagnets (4, 6).

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