Method for controlling a vehicle seat valve, control system for at least one vehicle seat valve and vehicle seat

Abstract

A method for controlling a vehicle seat valve, the piston of which is actively moved from a closed position to an open position or vice versa by applying an electrical voltage to a, in particular electromagnetic, drive element, characterized in that the power of the drive element is regulated via an effective voltage which can be varied by pulse width modulation of a pulse voltage having a constant frequency, wherein, in order to move the piston from its closed position towards its open position, a duty cycle (D) of the pulse width modulation is first increased from a rest duty cycle (D1), in particular 0%, to a start duty cycle (D2) of less than 100%, in particular of less than 50%, and is only increased to a final duty cycle (D4), in particular to 100%, after reaching the open position of the piston or / and upon detection of a blockage hindering the movement of the piston before reaching its open position.

Description

[0001] The invention relates to a method for controlling a vehicle seat valve according to the features in the preamble of claim 1. Furthermore, the invention relates to a control unit for at least one vehicle seat valve for carrying out this method according to the features of claim 9, and to a vehicle seat with at least one vehicle seat valve and such a control unit according to the features in claim 10.

[0002] Seats, particularly those installed in vehicles, sometimes feature at least one functional device operated by fluid pressure. These range from ergonomic adjustability to massage functions. In addition to electric actuators, hydraulically or pneumatically operated expansion elements are also used for this purpose. Such an expansion element, also known as a "bladder," comprises at least one fluid-tight hollow chamber, the volume change of which, based on filling and emptying, results in mechanical work.

[0003] The compressor used to generate the necessary fluid pressure can be positioned inside or outside the vehicle seat in such a way as to ensure extremely quiet operation of the expansion chambers. These chambers are typically supplied via hoses connected to the compressor. Each hose is assigned to at least one vehicle seat valve, which controls, for example, the targeted filling and emptying of the respective expansion chamber. As the number of expansion chambers increases, so does the number of vehicle seat valves required for control. These valves can be grouped together in a valve block. Typically, these vehicle seat valves are designed with a linearly movable piston.

[0004] DE 10 2013 225 690 A2 discloses a vehicle seat in which the backrest, articulated to a seat section, has a plurality of pneumatic expansion elements. These can be filled with compressed air by a compressor, the inflow and outflow of which is controlled by a vehicle seat valve arranged between the compressor and each expansion element. These vehicle seat valves, designed as solenoid valves, have a corresponding electromagnetic actuator, which can be controlled by a control unit connected to them.

[0005] The actuators of vehicle seat valves are usually energized with an electrical voltage, allowing the piston, which either blocks or enables the fluid flow, to move linearly from a closed to an open position and / or vice versa. In practical application, this can sometimes result in clearly audible switching noises, primarily from the piston, accelerated by its actuator, striking its structural travel limit.

[0006] From DE 10 2016 103 249 A1, a method for controlling the flow cross-section of a gas valve is known. In this method, a coil is controlled with a pulse-width modulated current, the duty cycle of which is initially increased to open the valve, decreased before reaching the open position, and then set to a holding value to reduce the noise generated during opening.

[0007] From DE 10 2017 215 997 A1, a device for controlling a solenoid valve is known, in which the control is designed, at least in part, as a ramp function and the level of the ramp start current is determined and / or adjusted depending on the pressure. Furthermore, a hydraulic brake system with a correspondingly controlled solenoid valve is disclosed therein.

[0008] Against this background, the invention is based on the objective of further developing a method for controlling a generic vehicle seat valve in such a way that its switching noises are reduced to a minimum, at least during normal operation.

[0009] According to the invention, the solution to this problem consists of a method comprising the measures of claim 1. Advantageous further developments are the subject of dependent claims 2 to 8. Furthermore, this problem is solved by a control system for carrying out the method according to the invention according to the features of claim 9 and by a vehicle seat comprising the features of claim 10.

[0010] With reference to the method according to the invention, it is now proposed to regulate the power of the drive element via an effective voltage that can be varied by pulse width modulation (PWM). Specifically, a pulse voltage with a constant frequency forms the basis, whereby the effective voltage ultimately applied to the drive element of the vehicle seat valve is changed to the desired value only by manipulating the duty cycle of the pulse width modulation of the pulse voltage.

[0011] In other words, the DC pulse voltage is periodically switched on and off within its frequency range. The corresponding period of each on-off cycle is calculated as the quotient of one second divided by the preset frequency in Hertz (Hz) (period = 1 / frequency [Hz]). The duty cycle is the ratio of the pulse duration (on) to the period. For example, a duty cycle of 50% changes the pulse voltage's period into an RMS voltage with an equal pulse duration (on) and pause (off). Assuming a purely illustrative period of 3.0 milliseconds (ms), the pulse duration and pause would each be 1.5 ms. Again, purely as an example, a pulse voltage of 12 volts (V) could be reduced to 6 V using pulse-width modulation with a 50% duty cycle.A duty cycle of, for example, 75% would change the pulse voltage from 12 V to 9 V, while a duty cycle of, for example, 25% would change the pulse voltage from 12 V to 3 V. In this way, the power of the drive can be regulated down to 0 V RMS solely through pulse width modulation of the pulse voltage and the resulting RMS voltage applied to the drive, by setting a duty cycle of 0%.

[0012] To move the piston from its closed position towards its open position, the duty cycle of the pulse width modulation is initially increased from a resting duty cycle to a starting duty cycle of less than 100%, preferably less than 50%. In this way, the actuator of the vehicle seat valve is initially supplied with an effective voltage below the pulse voltage, thus reducing its power accordingly. Only after the piston reaches its open position is the resting duty cycle increased to a final duty cycle, which can preferably be 100%. This ensures that the actuator only delivers its full power after the piston has reached its open position. Alternatively or additionally, the resting duty cycle can be increased to the final duty cycle if a blockage is detected that would impede the piston's movement before it reaches its open position.

[0013] The resulting advantages lie in a significantly quieter operation of the vehicle seat valve. This is mainly due to the reduced power of its drive mechanism at the beginning of the piston's movement towards its open position, so that it does not strike its structural movement limit with maximum force.

[0014] Here, the increase in the duty cycle to the end duty cycle can, for example, only occur after a defined period of time from the start of the increase in the rest duty cycle, after which the piston is usually expected to reach its open position. At this point, the piston is already in contact with a portion of its travel limit, so that the increase to the end duty cycle only results in a correspondingly increasing contact pressure of the piston against the travel limit, resulting in no mechanical noise whatsoever. At the same time, this ensures that any unnoticed but potentially unintentional piston movement blockage, caused by temperature or other factors, is overcome in every case, as the initial duty cycle could not generate a sufficiently high breakaway force from the drive mechanism.Although this would result in a corresponding noise generation from the piston being moved with correspondingly higher power or acceleration when it hits its structural movement limit, the function of the vehicle seat valve would still be ensured even outside of normal operation without such blockages.

[0015] Provided that at least one means of detecting a piston movement blockage is available, the starting duty cycle can be increased to, or at least towards, the end duty cycle at the moment this blockage is detected. In fact, the means of detecting a movement blockage during the increase of the starting duty cycle can be used to monitor the success of this measure. For example, if the blockage is detected to be resolved, further increases in the starting duty cycle towards the end duty cycle can be stopped to minimize the noise generated by the piston, which is already moving at increased power and thus impacting its travel limit.

[0016] According to a particularly preferred embodiment of the fundamental inventive concept described above, the initial duty cycle can be linearly increased to an intermediate duty cycle. The intermediate duty cycle lies between the initial and final duty cycles and is therefore lower than the final duty cycle. This linear increase of the initial duty cycle to the intermediate duty cycle occurs within a first time interval, which can end either after or before the piston, while in motion, reaches its open position. Thus, this increase can be carried out while the piston is still moving or after it has reached its open position.Of course, the time of arrival of the piston at its open position can also lie within the time period for raising the start value to the intermediate value, so that the raising begins before the piston arrives at its open position and ends after it arrives at the open position.

[0017] Based on this, the intermediate duty cycle can then be linearly increased to the final duty cycle before or after the piston reaches its open position. This increase occurs within a second time interval following the first. The second time interval can be shorter than the first. Increasing the intermediate duty cycle to the final duty cycle ensures that the piston is moved to its open position even in the event of blockages, provided that the intermediate duty cycle was insufficient to generate the necessary breakaway force to overcome the blockage.

[0018] Once the piston reaches its open position, the end duty cycle can be abruptly reduced to a holding duty cycle, either immediately or after a defined period. Since the piston is presumed to be in its open position after reaching the end duty cycle, the excessive power consumption of the drive system at this point can be reduced accordingly by lowering the end duty cycle. The holding duty cycle achieved by this reduction must be selected so that the piston remains in its open position under all circumstances. Typically, the piston is moved into its open position against a restoring force, which can, for example, result at least partially from a mechanical spring. This restoring force is used, for instance, to return the piston to its closed position when necessary.Against this background, the holding function is selected such that the piston remains in its previously assumed open position even when subjected to a restoring force. In other words, ideally, a kind of equilibrium is established between the opposing influences of the driving force of the actuator acting on the piston and the restoring force acting in the opposite direction, resulting in the piston remaining in its open position. Naturally, the driving force of the actuator can be somewhat greater than the restoring force, for example by 2% to 10%, so that in any case – even in the event of temporary influences or events affecting the piston's position – the piston's position in its open position is ensured.

[0019] The vehicle seat valve serves to switch a fluid flow, preferably compressed air. This means that the fluid flow can occur when the vehicle seat valve is open (piston in the open position), while it is prevented when the valve is closed (piston in the closed position). Therefore, the vehicle seat valve, as a switching unit, has only two states. The invention provides that the fluid pressure of the fluid flow switchable by the vehicle seat valve can be detected. In particular, by detecting the fluid pressure downstream of the piston, conclusions can be drawn about the piston's state with respect to its open and / or closed position. For example, a detected increase in fluid pressure can indicate that the piston is moving towards its open position or has already reached it.Within the framework of the inventive method, for example, a blockage hindering the displacement of the piston towards its open position can be detected based on the absence of an expected change in fluid pressure during the manipulation of the drive means.

[0020] With regard to the repositioning of the piston from its open position to its closed position, the invention proposes further measures to make this possible with as little noise as possible: The piston can thus preferably be moved from its closed position towards its open position against a restoring force. This restoring force can result, at least in part, from a mechanical spring. To move the piston back from its open position towards its closed position, the holding threshold can be reduced at the beginning of its return movement until the driving force of the actuator acting on the piston is less than the restoring force acting on the piston in the opposite direction. By reducing the holding threshold and the associated reduction in the driving force of the actuator, the restoring force acting on the piston becomes sufficient, above a certain value, to move the piston from its open position back towards its closed position.Since the piston is not accelerated with the full power of the drive mechanism, the contact of the piston with an area of ​​its movement limit when reaching the closed position is accompanied by correspondingly little energy, so that noise generation is significantly reduced.

[0021] It is conceivable that fluid pressure acting on the piston when it is lifted from its open position increases the restoring force that is already exerted on it. Therefore, the invention provides that the fluid pressure increasing the restoring force can be detected during the piston's movement back towards its closed position. The holding duty cycle is then reduced until the driving force of the drive mechanism acting on the piston is less than the restoring force exerted on the piston in the opposite direction and increased by the fluid pressure. In other words, this measure, which further refines the method according to the invention, also takes into account any influence of the fluid pressure on the piston in order to reduce the holding duty cycle to the most realistic and therefore ideal value possible with regard to a quiet movement of the piston back to its closed position.

[0022] Preferably, the reduction of the holding degree back to the resting position can be linear. This means that the holding degree is reduced constantly over a predetermined time period. The reduction occurs in such a way that the resting position is only reached once the piston is in its closed position. Alternatively, the reduction can be such that the resting position is only reached after the piston is in its closed position. This ensures that the piston is never moved back into its closed position with the full force of the return stroke, which could otherwise cause noise when its structural limit of movement is reached.

[0023] The method according to the invention offers an extremely simple way to influence the displacement movements of the piston in a vehicle seat valve in such a way that otherwise perceptible noises can be largely reduced or even completely avoided. By adjusting the duty cycle of the pulse width modulation of the impulse voltage, the forces acting on and displacing the piston can be kept within a constantly adapted range. This range guarantees the displacement of the piston but, if possible, never displaces it with an excessively high driving force. In addition to the resulting noise reduction, this also leads to a significantly reduced wear of the piston and / or its structural movement limiter.

[0024] Furthermore, the invention is directed to a control system for at least one vehicle seat valve for carrying out the method according to the invention.

[0025] The invention also relates to a vehicle seat with at least one vehicle seat valve and a control system according to the invention.

[0026] The advantages arising from the control system and / or the vehicle seat according to the invention have already been explained in more detail in connection with the method according to the invention, so that, to avoid repetition, reference is made here to the corresponding explanations.

[0027] The present invention will now be explained in more detail with reference to a schematically illustrated embodiment. The figures shown are: Fig. 1 a schematic sequence of the inventive method for relocating the piston of a vehicle seat valve into its open position and Fig. 2 a schematic sequence of the inventive method for moving the piston of a vehicle seat valve into its closed position.

[0028] Fig. Figure 1 shows a purely schematic sequence of the inventive method for displacing a piston of a vehicle seat valve (not shown in detail). Here, only the control of the vehicle seat valve is illustrated by means of a first function graph 1a, from which an effective voltage applied to a drive element manipulating the piston results. The drive element is preferably an electromagnetic drive element.

[0029] The method according to the invention is based on a pulse voltage with a constant frequency, the pulse width modulation (PWM) of which allows a correspondingly variable effective voltage to be applied to the drive element. By changing the effective voltage, the power of the drive element, which actively moves the piston into its closed position, can be regulated accordingly. For this purpose, a duty cycle D of the pulse width modulation is changed in the manner described below: At the start of the piston's movement, it is in its closed position. In this position, the piston is held in place by, for example, a mechanical spring. In the closed position, the duty cycle D1 is 0%, resulting in an effective voltage of 0.0 volts (V) applied to the drive mechanism. To move the piston from its closed position towards its open position, the duty cycle D1 is abruptly increased to a start duty cycle D2 after a time t of 20 milliseconds (ms). In this example, the start duty cycle D2 is 30%, meaning that approximately 30% of the pulse voltage is now applied as the effective voltage to the drive mechanism.

[0030] The initial duty cycle D2 is generally selected so that, during normal operation, the piston moves from its closed position towards its open position against the restoring force acting upon it. Even the initial duty cycle D1 can be sufficient to move the piston to its open position, which it reaches with only low speed and force due to the reduced power of the drive mechanism. As a result, the contact with its physical travel limit is particularly smooth, minimizing any resulting noise.

[0031] To overcome any potential piston movement blockages, the initial duty cycle D2 is increased to an intermediate duty cycle D3 over an initial period T1 of – in this example – 60 ms. In this example, the intermediate duty cycle D3 is 60%, meaning that approximately 60% of the pulse voltage is now applied to the drive element as effective voltage. The linear increase to the intermediate duty cycle D3 is advantageous because, in the event of a piston movement blockage, the parallel increase in the drive element's force will eventually reach a level sufficient to overcome the blockage and thus move the piston into its open position. Simultaneously, only a portion of the maximum possible pulse voltage remains applied to the drive element as effective voltage, resulting in a potentially higher, but still very low, noise level.

[0032] Provided there is no movement obstruction, this measure merely presses the piston, which is already in its open position due to the initial duty cycle D2, further against its structural movement limit, resulting in no noise whatsoever. Therefore, increasing the initial duty cycle D2 to the intermediate duty cycle D3 should be understood as a protective measure to ensure that the piston does not remain in its closed position due to a movement obstruction.

[0033] To overcome a significant movement blockage of the piston, which is either still in its closed position or stuck on its way to the open position, the intermediate duty cycle D3 is increased to a final duty cycle D4 over a second time interval T2 of – here purely as an example – 20 ms. As can be seen, the second time interval T2 is considerably shorter than the first time interval T1, so that, in combination with the further 40% increase in duty cycle D, the function graph 1a becomes significantly steeper during the second time interval T2.

[0034] As a purely illustrative example, the duty cycle D4 is set to 100%, meaning that virtually 100% of the pulse voltage is now applied to the drive element as effective voltage. The linear increase to the duty cycle D4 is advantageous because, in the event of a possible piston movement blockage, the parallel increase in the drive element will eventually reach a level sufficient to overcome the blockage and ultimately move the piston into its open position. This also allows any movement blockage that may be present in the piston's open position to be overcome, ultimately moving the piston into its open position.The speed and force of the piston resulting from the now significantly higher drive power of the drive element can be accompanied by a correspondingly greater noise level in such a scenario outside of normal operation; however, this ensures that the piston is definitely moved into its open position.

[0035] Based on the measures taken previously, it can be assumed that the piston is now definitely in its open position. In the next step, the duty cycle D4 is abruptly reduced to a holding duty cycle D5. In this example, this is 40%, meaning that 40% of the pulse voltage remains as effective voltage at the drive mechanism.

[0036] The holding pressure level D5 is chosen so that the piston is always held securely in its open position and the vehicle seat valve fulfills its intended function.

[0037] In principle, the fluid pressure acting on the piston from a fluid flow switchable by the vehicle seat valve can also be detected. If the duty cycle D is manipulated to initiate the piston's movement from its closed position, but no expected change in fluid pressure is detected, the initial time interval T1 can be shortened, and / or the intermediate duty cycle D3 can be set above the value shown here, for example, to overcome the apparent piston movement blockage as quickly as possible.

[0038] Fig.Figure 2, also in a purely schematic manner, illustrates the process of the inventive method for moving the piston back to its closed position using a second function graph 1b. As can be seen, the hold duty cycle D5 in the open position initially remains at an exemplary 40%. Starting from this point, the hold duty cycle D5 is reduced, purely by example, after 20 ms over a third time interval T3 to the initial rest duty cycle D1 of 0%. Purely by example, this third time interval T3 is 60 ms.

[0039] By applying the restoring force to the piston, a point is eventually reached during the lowering of the holding duty cycle D5 where the restoring force is greater than the current duty cycle D. This allows the piston to be gently moved back into its closed position by the restoring force. The third time interval, T3, is chosen such that the rest duty cycle D1 is only reached under normal circumstances once or after the piston has reached its closed position. In this way, the speed and force of the moving piston are further reduced to a minimum, resulting in a significant reduction in noise.

[0040] Naturally, fluid pressure increasing the restoring force on the piston during its return to its closed position can also be detected and thus taken into account when reducing the holding duty cycle D5. This can be reflected, for example, in a corresponding adjustment of the third time interval T3. Reference symbol list: 1a first function graph 1b second function graph D Duty cycle of pulse width modulation in percent [%] D1 idle duty cycle D2 Starting duty cycle D3 intermediate duty cycle D4 End duty cycle D5 Hold Rate t Time in milliseconds [ms] T1 first time period between D2 and D3 T2 second time period between D3 and D5 T3 third time period between D5 and D1

Claims

[1] Method for controlling a vehicle seat valve, the piston of which is actively moved from a closed position to an open position or vice versa by applying an electrical voltage to a, in particular electromagnetic, drive means, characterized by , that the power of the drive means is regulated via an effective voltage which can be varied by pulse width modulation of a pulse voltage having a constant frequency, wherein, in order to move the piston from its closed position towards its open position, a duty cycle (D) of the pulse width modulation is first increased from a rest duty cycle (D1), in particular 0%, to a start duty cycle (D2) of less than 100%, in particular of less than 50%, and is only increased to a final duty cycle (D4), in particular to 100%, after reaching the open position of the piston or / and upon detection of a blockage hindering the movement of the piston before reaching its open position. [2] Method according to claim 1, characterized by , that the initial duty cycle (D2), in particular before or after reaching the open position of the piston, is first increased linearly within a first time interval (T1) to an intermediate duty cycle (D3) which is smaller than the final duty cycle (D4). [3] Method according to claim 2, characterized by , that the intermediate duty cycle (D3) is linearly increased to the final duty cycle (D4) before or after reaching the open position of the piston within a second time period (T2) that is shorter than the first time period (T1). [4] Method according to any one of the preceding claims, characterized bya, in particular abrupt, lowering of the final duty cycle (D4) after reaching the open position of the piston to a holding duty cycle (D5) such that the piston, which is subjected to a restoring force, in particular resulting from a mechanical spring means, is still held in its open position by a driving force of the driving means that counteracts this force. [5] Method according to any one of the preceding claims, characterized by , that a fluid pressure of a fluid flow switchable by the vehicle seat valve is detected, whereby a blockage hindering the displacement of the piston towards its open position is detected based on the absence of an expected change in fluid pressure during manipulation of the drive means. [6] Method according to claim 4 or 5, characterized by, that the piston is displaced from its closed position towards its open position against a restoring force, in particular resulting from a mechanical spring means, wherein at the beginning of the displacement of the piston from its open position back towards its closed position the holding key degree (D5) is lowered until a driving force of the driving means acting on the piston is less than the restoring force acting on the piston in the opposite direction. [7] Method according to any one of claims 4 to 6, characterized by , that a fluid pressure increasing the restoring force acting on the piston is detected during the displacement of the piston back towards its closed position, whereby the holding duty factor (D5) is reduced until a driving force of the drive means acting on the piston is less than the restoring force acting on the piston in the opposite direction and increased by the fluid pressure. [8] Method according to any one of claims 4 to 7, characterized by a linear reduction of the holding key level (D5) to the rest key level (D1), particularly during the movement of the piston back towards its closing position or after reaching the closing position of the piston, such that the rest key level (D1) is only reached once or after the piston is in its closing position. [9] Control for at least one vehicle seat valve for carrying out the method according to any of the preceding claims. [10] Vehicle seat with at least one vehicle seat valve and a control unit according to claim 9.

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