Method for adjusting a damping force and a damping system for a motor vehicle

Abstract

Damping system (10) for a motor vehicle comprising a working cylinder (14) that is at least partially filled with hydraulic fluid, a working piston (16) arranged within the working cylinder (14) and axially movable, with a piston rod (18), wherein the working piston (16) divides the working cylinder (14) into a first working chamber (20) and a second working chamber (22), and a pressure setting arrangement (24) for setting the pressure in the first and second working chambers (20, 22), wherein the pressure setting arrangement (24) comprises a pump (28) which is connected to the first and second working chambers (20,22) via hydraulic lines (32-39), wherein the pressure setting arrangement (24) has at least one compensation device (52, 54) for reducing pressure fluctuations in the damping system (10), which is connected to the pump (28) and the working cylinder (14) which is at least partially filled with hydraulic fluid, characterized in that the compensation device (52, 54) is designed and configured such that the natural frequency of the compensation device (52, 54) is adjustable during operation of the damping system, and wherein the damping system (10) has a control / regulating device (56) which is designed to determine the frequency of the pressure fluctuations within the damping system (10) and to adjust the natural frequency of the compensation device (52, 54) to correspond to the determined frequency of the pressure fluctuations.

Description

[0001] The invention relates to a method for adjusting a damping force of a damping system for a motor vehicle, and to a damping system for a motor vehicle.

[0002] Prior art discloses damping systems for motor vehicles that include a working cylinder filled with hydraulic fluid. To generate active damping, the working cylinder is connected, for example, to a hydraulic pump. Such an active damping system is known from DE102019115492B4. An active damping system is, for example, a damping system with a pump by means of which the pressure in the cylinder chambers can be actively controlled. Prior art active damping systems often have a large number of hydraulic components and sensors to enable targeted adjustment of the pressure and the desired damping effect. The hydraulic fluid flowing between these components is typically subject to pressure fluctuations, which can lead to reduced functionality of the damping system or cause acoustic noise during operation.Such pressure fluctuations can also damage the components of the damping system and, for example, cause increased wear.

[0003] From DE 10 2020 214 277 B3, a vibration damper with a pump arrangement is known whose pulsating delivery volumes lead to noise, and therefore, in addition to a compensating reservoir, it uses a pulsation reservoir to reduce these pressure fluctuations. This compact pulsation reservoir is divided into two chambers by a separating piston, which correspond to the working areas.

[0004] DE 10 2020 203 660 A1 describes a device for reducing vibrations in a fluid system, in which a separating agent, such as a piston or a diaphragm, limits a fluid-carrying cavity and its stiffness is mechanically adjustable in order to compensate for pressure fluctuations in a targeted manner.

[0005] From DE 10 2006 033 775 B3 a pulsation damper is known with several differently designed damping chambers which can be selectively connected to the fluid line via a rotatable control piston, so that the chamber suitable for the current frequency range is used to dampen pressure pulsations.

[0006] Based on this, the object of the present invention is to provide a damping system that enables active control, in particular damping, and reduces pressure fluctuations in a cost-effective and simple manner. A further object is to provide a compensation device for such a damping system.

[0007] This problem is solved according to the invention by a device having the features of independent device claim 1 and by a method having the features of independent method claim 11. Advantageous embodiments are described in the dependent claims.

[0008] According to a first aspect, the invention comprises a damping system for a motor vehicle comprising a working cylinder at least partially filled with hydraulic fluid, a working piston arranged within the working cylinder and axially movable with a piston rod, wherein the working piston divides the working cylinder into a first working chamber and a second working chamber, and a pressure adjustment arrangement for adjusting the pressure in the first and the second working chamber, wherein the pressure adjustment arrangement comprises a pump which is connected to the first and the second working chamber via hydraulic lines, wherein the pressure adjustment arrangement comprises at least one compensation device for reducing pressure fluctuations in the damping system which is connected to the pump and the working cylinder which is at least partially filled with hydraulic fluid.The compensation device is designed and configured such that the natural frequency of the compensation device is adjustable during operation of the damping system, and wherein the damping system has a control / regulating device designed such that it determines the frequency of the pressure fluctuations within the damping system and adjusts the natural frequency of the compensation device to correspond to the determined frequency of the pressure fluctuations.

[0009] The compensation device is preferably a resonator that can be excited at a natural frequency. The compensation device is preferably arranged in the damping system such that it reduces pressure fluctuations occurring in the damping system. In particular, the compensation device is directly connected to at least one hydraulic line of the damping system, especially the pressure adjustment assembly. According to the inventors, the pressure fluctuations of the damping system are largely or completely reduced by the compensation device when the frequency of the pressure fluctuations corresponds to the natural frequency of the compensation device. Preferably, the natural frequency depends on the geometry of the compensation device, such that a change in the geometry of the compensation device causes a change in the natural frequency of the compensation device.

[0010] The damping system preferably comprises a vibration damper with a working cylinder and a working piston. The vibration damper is, for example, a single-tube vibration damper or a multi-tube vibration damper. A vibration damper, in particular a multi-tube vibration damper, for a vehicle comprises, for example, an outer tube and an inner tube arranged coaxially to it, in particular the working cylinder, wherein a compensating chamber for receiving hydraulic fluid is formed between the outer tube and the inner tube, and a working piston connected to a piston rod, which is arranged to be movable back and forth within the inner tube, wherein the interior of the inner tube is divided by the working piston into a first working chamber and a second working chamber.

[0011] The vibration damper is, for example, a multi-tube vibration damper, wherein the compensation chamber is partially filled with a gas, particularly at its upper end. A central tube is preferably arranged coaxially to the inner and outer tubes within the compensation chamber, and particularly attached to the inner tube. The compensation chamber is preferably designed as an annular space and is bounded by the outer tube and the central tube or the inner tube. The outer tube preferably forms at least part of the housing of the vibration damper. The inner surface of the inner tube is preferably designed as a guide for the working piston. The working piston preferably has a valve assembly through which the first and second working chambers are connected. Optionally, the multi-tube vibration damper is designed without a central tube and with an external gas chamber, particularly a hydraulic accumulator.

[0012] The vibration damper features, in particular, a sealing assembly designed and arranged to fluidically seal the interior of the outer tube on the piston rod side. The piston rod end of the inner tube is preferably attached to the sealing assembly. Opposite the sealing assembly, at the end furthest from the piston rod, the interior of the outer tube is preferably fluidically sealed by means of a bottom piece. A bottom valve is optionally arranged on the bottom piece, preferably at the end of the inner tube furthest from the piston rod. The second working chamber is preferably fluidically connected to the compensation chamber via the bottom valve. The bottom valve is preferably a check valve that allows flow in both directions or only in one direction.For example, the bottom valve is designed as a check valve in the direction of pull, when the piston moves out of the inner tube, and as a characteristic-generating valve in the direction of pressure, when the piston moves into the inner tube.

[0013] The pressure adjustment arrangement is preferably designed to adjust the pressure within the working chambers, in particular the force acting on the working piston. Specifically, the pressure adjustment arrangement is designed to adjust the damping force of the damping system.

[0014] The pump is preferably a bidirectional hydraulic pump with at least two connections for connection to a hydraulic line, wherein the connections can each be operated as an inlet or outlet of the hydraulic pump.

[0015] Preferably, the pump's direction of rotation is reversible, allowing it to operate in either suction or pressure mode. The hydraulic accumulator is, for example, a pressurized accumulator filled with hydraulic fluid and gas. Preferably, the pump is a gear pump. The pump is preferably connected to a motor, particularly an electric motor, for driving the pump.

[0016] Optionally, the pressure adjustment arrangement comprises a hydraulic accumulator, a first valve, and a second valve, each connected to the first and second working chambers via hydraulic lines, and wherein the valves are designed such that the valve position is adjustable, in particular continuously. The valves are preferably continuously adjustable valves, especially solenoid valves. Preferably, the hydraulic resistance of the valves is adjustable. The valve position refers in particular to the position of a control spool of the valve, which opens or closes a flow channel, such that the hydraulic resistance changes with different valve positions. Preferably, each valve has a solenoid coil that can be energized and influences the position of the control spool and thus the valve position.

[0017] The pressure adjustment arrangement preferably comprises a plurality of hydraulic lines for connecting the pump and the hydraulic accumulator to the valves and the first and second working chambers of the vibration damper. The pressure adjustment arrangement preferably includes at least two check valves. The check valves are, for example, connected in series with each other and in parallel with the valves, the pump, and / or the hydraulic accumulator.

[0018] The pump is preferably connected to the first working chamber of the vibration damper via a hydraulic line and, in particular, to the second working chamber of the vibration damper via a further hydraulic line. The valves are preferably connected in series and to the pump via a hydraulic line, and preferably in parallel with the pump. For example, the valves are designed such that they are each only open to flow in one direction. Preferably, one valve is open to flow during the compression stage and the other during the rebound stage. In this case, the valves are preferably connected in series with one of the check valves each.

[0019] The optional hydraulic accumulator is preferably connected to the two check valves via a hydraulic line such that the connection point of the hydraulic lines is located between the two check valves. The hydraulic accumulator is preferably also connected to the two valves via the hydraulic line such that the connection point of the hydraulic lines is located between the two valves.

[0020] The pressure adjustment arrangement is preferably designed to influence the damping characteristic of the vibration damper and is connected to it. The pressure adjustment arrangement is preferably designed to allow either active or passive influence, in particular damping, of the vibration damper. In the case of passive influence, particularly damping, preferably no additional pressure is applied to the vibration damper via the pump and / or the hydraulic accumulator, whereas in the case of active influence, a pressure increase occurs in at least one working chamber via the pump and / or the hydraulic accumulator.

[0021] According to a first embodiment, the compensation device has a volume filled with hydraulic fluid, wherein the compensation device is designed and configured such that the size of the volume is adjustable. The volume filled with hydraulic fluid is preferably located within a container and fluidically connected to the damping system. The container is preferably a hollow cylinder, a hollow sphere, or a container with an angular, in particular rectangular, cross-section. Preferably, the container is designed such that its geometry is modifiable. Preferably, at least one container wall is movable relative to the other container walls. A change in volume causes a change in the natural frequency of the compensation device.

[0022] According to a further embodiment, the compensation device comprises a volume filled with hydraulic fluid and an inlet through which the volume can be connected to the pump and / or the working cylinder, and wherein the compensation device is designed such that the flow cross-section and / or the length of the inlet is adjustable. The volume formed in the container is preferably connected via the inlet to a hydraulic line of the damping system, in particular the pressure adjustment arrangement. The inlet is, for example, formed in a preferably tubular inlet housing. The inlet has, for example, a round, square, circular, or rectangular cross-section. In particular, the inlet has a direct fluid connection with the volume and another direct fluid connection with one of the hydraulic lines. Preferably, the inlet has a smaller cross-section than the volume, in particular the container.The inlet preferably creates a flow resistance between the hydraulic lines and the volume within the container. The natural frequency of the compensation device is preferably dependent on the magnitude of the flow resistance and / or the length of the inlet. A change in volume, the magnitude of the flow resistance, and / or the length of the inlet therefore preferably results in a change in the natural frequency of the compensation device.

[0023] According to a further embodiment, the compensation device has at least one movable wall element arranged within the inlet and / or within a housing that defines the volume. For example, the compensation device has exactly one movable wall element or a plurality of movable wall elements. For example, a movable wall element is arranged within the inlet. The movable wall element is preferably mounted so as to be movable relative to the inlet, in particular the inlet housing. Preferably, the wall element is movable from a first position, in which the inlet has a first flow cross-section and / or a first length, to a second position, in which the inlet has a second flow cross-section and / or a second length.The wall element is preferably arranged within the inlet housing in such a way that it is infinitely adjustable and preferably lockable in a desired position. The movable wall element is in particular designed as a pipe element that can be inserted into the inlet, thus changing, in particular reducing, the flow cross-section and / or the length of the inlet.

[0024] For example, a movable wall element is arranged inside the container. The movable wall element is preferably mounted so that it can be moved relative to the container. Preferably, the wall element is movable from a first position, in which the container has a first volume, to a second position, in which the container has a second volume. The wall element is preferably arranged inside the container such that it is infinitely movable and preferably lockable in a desired position. The movable wall element is particularly designed as a piston with a piston rod, which divides the interior of the container into a first volume furthest from the piston rod and a second volume closer to the piston rod. Preferably, the volume furthest from the piston rod is directly connected to the inlet.Preferably, the pump speed is known, and in particular adjustable, wherein the frequency of the pressure fluctuations within the damping system is a multiple of the speed and / or the number of teeth of the gear pump. In particular, the control device is designed such that it multiplies the pump speed and the number of teeth together to determine the frequency of the pressure fluctuations within the damping system. For example, the frequency of the pressure fluctuations within the damping system corresponds to the product of the pump speed and the pump's number of teeth.

[0025] A gap is preferably formed between the wall element and the container or inlet housing, through which hydraulic oil can flow. It is also conceivable that the wall element is at least partially or completely fluidly sealed against the container or inlet housing.

[0026] The damping system includes a control device configured to determine the frequency of pressure fluctuations within the damping system, in particular the pump frequency. Optionally, the control device includes a pump model that encompasses the pump pressure across the pump's operating range, and the control device is configured to derive the frequency of the damping system's pressure fluctuations from the pump model.

[0027] Preferably, the frequency of pressure fluctuations within the damping system is determined using a model based on a predefined pump model that encompasses the pump pressure across the pump's operating range. In particular, a mathematical pump model is predefined and stored in the damping device, preferably a control unit. The mathematical pump model is preferably a mathematical model obtained through test series conducted on a test bench and subsequent validation, designed to represent the pump's performance and operating range.For this purpose, parameters such as pump pressure, flow rate, rotational speed, voltage, pump current consumption, and / or the force applied to the piston rod are measured via appropriate sensors across the pump's operating range. A mathematical model is then created from these measurements, which assigns a frequency of pressure fluctuations within the damping system to known values ​​such as pump pressure, flow rate, rotational speed, voltage, pump current consumption, and / or the force applied to the piston rod. The pump model is preferably a dynamic pump model that can be adapted during the operation of the damping system.

[0028] Optionally, the pump model is continuously monitored and corrected. Preferably, a correction factor is determined during operation of the damping system. In particular, the correction factor is applied to the pump model during operation of the damping system to adapt the pump model to, for example, different environmental conditions and especially to compensate for deviations between the model and reality.

[0029] According to a further embodiment, the control device is connected to the compensation devices in such a way that it adjusts the natural frequency of the compensation devices depending on the determined frequency of the pressure fluctuations within the damping system. In particular, the control device is designed such that it adjusts the natural frequency of the compensation device so that it corresponds to the determined frequency of the pressure fluctuations within the damping system. Preferably, the control device is connected to the compensation device in such a way that it adjusts the movable wall so that the natural frequency of the compensation device corresponds to the frequency of the pressure fluctuations within the damping system.

[0030] According to another embodiment, the damping system has at least one sensor for determining the frequency of pressure fluctuations within the damping system, which is connected to the control device for transmitting the determined frequency. The sensor is, for example, a pressure sensor.

[0031] The invention also includes a motor vehicle with a chassis and a damping system attached thereto as described above.

[0032] The invention also includes a method for operating a damping system for a motor vehicle, wherein the damping system comprises: a working cylinder at least partially filled with hydraulic fluid, a working piston arranged within the working cylinder and axially movable with a piston rod, wherein the working piston divides the working cylinder into a first working chamber and a second working chamber, and a pressure adjustment arrangement for adjusting the pressure in the first and the second working chamber, wherein the pressure adjustment arrangement comprises a pump which is connected to the first and the second working chamber via hydraulic lines and wherein the pressure adjustment arrangement comprises at least one compensation device for reducing pressure fluctuations in the damping system.The frequency of the damping system is determined and the natural frequency of the compensation device is controlled / regulated during operation of the damping system so that it corresponds to the determined frequency of the pressure fluctuations.

[0033] The invention also includes a method for operating a compensation device to reduce pressure fluctuations in a damping system for a motor vehicle, wherein the compensation device can be connected to a pump and a working cylinder at least partially filled with hydraulic fluid, wherein the natural frequency of the compensation device is adjusted during operation of the damping system.

[0034] The embodiments, features and advantages described above with reference to the device also apply, in accordance with the procedure, to the method for operating a damping system.

[0035] According to a further embodiment, the natural frequency of the compensation device is controlled / regulated depending on the determined frequency. Preferably, the natural frequency of the compensation device is set such that it corresponds to the determined frequency.

[0036] According to a further embodiment, the frequency of the damping system is determined using a model based on a predefined pump model that encompasses the frequency of the damping system across the pump's operating range. Preferably, the pump speed is known, and in particular, adjustable, with the frequency of the pressure fluctuations within the damping system being a multiple of the speed and / or the number of teeth of the gear pump. Specifically, to determine the frequency of the pressure fluctuations within the damping system, the pump speed and the number of teeth are multiplied together. For example, the frequency of the pressure fluctuations within the damping system corresponds to the product of the pump speed and the pump's number of teeth.

[0037] According to another embodiment, the compensation device has a volume filled with hydraulic fluid, wherein the size of the volume is adjusted to adjust the natural frequency of the compensation device.

[0038] According to another embodiment, the compensation device has a volume filled with hydraulic fluid and an inlet through which the volume is connected to the pump and / or the working cylinder, wherein the flow cross-section of the inlet is adjusted to set the natural frequency of the compensation device.

[0039] The invention also includes a computer program product for controlling the previously described method for operating a damping system for a motor vehicle. Description of the drawings

[0040] The invention is explained in more detail below with reference to several exemplary embodiments and the accompanying figures. Fig. Figure 1 shows a schematic representation of a damping system according to an exemplary embodiment. Fig. Figure 2 shows a schematic representation of a damping system according to an exemplary embodiment. Fig. Figures 3-5 each show a schematic representation of a compensation device according to several exemplary embodiments.

[0041] Fig. Figure 1 shows a damping system 10 for a motor vehicle. In particular, such a damping system is attached to the chassis of a motor vehicle (not shown here). The damping system 10 comprises, by way of example, a vibration damper 12, in particular a monotube vibration damper, with a working cylinder 12. A working piston 16 is arranged inside the working cylinder 12, which is preferably mounted to be movable in the axial direction of the working cylinder 14. A piston rod 18 is attached to the working piston 16, extending centrally through and out of the working cylinder 14 in the axial direction. The working piston 16 is preferably guided hydraulically within the working cylinder 14 and divides the working cylinder 14 into a first working chamber 20 on the piston rod side and a second working chamber 22 further away from the piston rod.The working piston 16 preferably comprises a valve arrangement, in particular for limiting a maximum pressure difference between the two working chambers 20, 22. The vibration damper can also be a multi-tube vibration damper. The damping system 10 of the... Fig. 1 includes, for example, a gas space not shown, in particular a hydraulic accumulator, to prevent foam formation within the damping system 10.

[0042] The damping system 10 further comprises a pressure adjustment arrangement 24 for adjusting the damping force acting on the piston rod, in particular for adjusting the pressure within the first working chamber 20 and the second working chamber 22. The pressure adjustment arrangement 24 includes, by way of example, a pump 28. The pump 28 is preferably connected to a motor 30, in particular an electric motor. The pump 28 is preferably a bidirectional hydraulic pump with at least two ports for connection to a respective hydraulic line, wherein the ports can each be operated as an inlet or outlet of the hydraulic pump. Preferably, the pump is designed as a gear pump. The pressure adjustment arrangement 24 comprises a plurality of hydraulic lines 32, 34 for connecting the pump 28 and the hydraulic accumulator 26 to the first working chamber 22 and the second working chamber 24 of the vibration damper 20.The pump 28 is connected, for example, via a first hydraulic line 32 to the first working chamber 20 of the vibration damper 12 and, in particular, via a second hydraulic line 34 to the second working chamber 22 of the vibration damper 12.

[0043] Passive influence is achieved with the damping system 10 of the Fig. 1 For example, during a retraction movement of the working piston (pressure stage), the second working chamber 22 is hydraulically connected to the first working chamber 20 via lines 32, 34. Preferably, the hydraulic fluid flows from the second working chamber 22 into the second hydraulic line 34, via the pump 28 (which may be deactivated) into the first hydraulic line 32 and into the first working chamber 20.

[0044] In the case of active control, for example, a pressure increase occurs in one of the working chambers 20, 22, particularly without movement of the working piston 16 within the working cylinder 14. Preferably, in the case of active control or activation of the damper, in addition to the pressure increase in the working chambers 20, 22 caused by the movement of the working piston 16, a further pressure increase occurs by means of the pump 28. The pump 28 is preferably designed such that it can be operated in the direction of the first hydraulic line 32 or the second hydraulic line 34. When operating in the direction of the first hydraulic line 32, this line is connected to the fluid outlet of the pump 28.In particular, if the direction of rotation of the pump is changed, it can be operated in the other direction, for example in the direction of the second hydraulic line 34, so that the first hydraulic line 32 is connected to the fluid inlet and the second hydraulic line 34 to the fluid outlet of the pump 28.

[0045] Active pressure increase within the first working chamber 20 preferably occurs when the pump 28 is operated in the direction of the first hydraulic line 32. The hydraulic fluid preferably flows from the second hydraulic line 34 into the fluid inlet of the pump 28 and then into the first hydraulic line 32. Active pressure increase within the second working chamber 22 preferably occurs when the pump 28 is operated in the direction of the second hydraulic line 34. The hydraulic fluid preferably flows from the first hydraulic line 32 into the fluid inlet of the pump 28 and then into the second hydraulic line 34.

[0046] The pressure adjustment arrangement 24 optionally comprises two compensation devices 52, 54, wherein a first compensation device 52 is preferably directly connected to the first hydraulic line 32 and is arranged between the pump 28 and the first working chamber 20. A second compensation device 54 is preferably directly connected to the second hydraulic line 34 and is arranged between the pump 28 and the second working chamber 22. The pressure adjustment arrangement 24 optionally includes a sensor 58, which is preferably configured to determine the pressure within the damping system 10. The sensor 58 is optionally arranged between the pump and the first compensation device 52. However, any arrangement within the damping system, in particular the pressure adjustment arrangement 24, for determining the pressure in the hydraulic lines 32, 34 or in the working chambers 20, 24 is possible.

[0047] The damping system 10 preferably comprises a control / regulation device 56. The control / regulation device 56 is connected, for example, to the pump 28, in particular the motor 30, the compensation devices 52, 54 and optionally to the sensor 58 for the purpose of controlling / regulating and transmitting data.

[0048] The compensation devices 52, 54 are, for example, identically designed. The compensation devices 52, 54 are preferably resonators, which can preferably be excited at a natural frequency. The configurations of the compensation devices 52, 54 are described with reference to the Fig. 3 to 6 described.

[0049] In the operation of the damping system of the Fig. 1. For example, the pump 28 generates pressure fluctuations that are largely within a specific frequency range or exhibit a specific frequency. If this frequency corresponds to the natural frequency of at least one of the compensation devices 52, 54, a reduction, in particular compensation, of the pressure fluctuations of the damping system 10 occurs, especially in the hydraulic line 32, 34 connected to the corresponding compensation device 52, 54.

[0050] The compensation devices 52, 54 are preferably designed such that the natural frequencies of the compensation devices 52, 54 are each adjustable. A first compensation device 52 is preferably directly connected to the first hydraulic line 32 and is arranged between the pump 28 and the first working chamber 20. Preferably, the natural frequency of the compensation devices 52, 54 is set, preferably controlled, by means of the control device 56 as a function of the frequency of the pressure fluctuations in the damping system 10, in particular in at least one of the hydraulic lines 32, 34 and / or the working chambers 20, 22.

[0051] Preferably, the control / regulation device 56 is configured to determine the frequency of pressure fluctuations in the damping system 10. For example, a mathematical pump model is stored in the control / regulation device 56 to determine the frequency of the pressure fluctuations in the damping system 10. The control / regulation device 56 is preferably connected to the pump and configured to determine an operating state of the pump 28, in particular the volume flow rate or the rotational speed. The pump model assigns a specific pump pressure frequency to the pump's operating state. The mathematical pump model is preferably a mathematical model obtained by means of test series carried out on a test bench and subsequent validation, for representing the performance and operating range of the pump 28.For this purpose, the volume flow rate, rotational speed, pump pressure, and / or the frequency of pressure fluctuations at the outlet of pump 28 are measured and correlated using a mathematical model. Preferably, the pump model is continuously validated during operation of the damping system 10 using a correction factor. The correction factor preferably takes into account deviations of the pump model from reality due to, for example, external influences such as environmental conditions, temperature, or wear.

[0052] Preferably, the control / regulating device 56 is configured such that it adjusts the natural frequency of at least one or both compensation devices 52, 54 to the determined value of the frequency of the pressure fluctuations in the damping system 10. The adjustment of the natural frequency of the compensation devices 52, 54 is carried out with reference to the Fig. 3 to 6 described.

[0053] Fig. Figure 2 shows another embodiment of a damping system 10, which largely corresponds to the Fig. 1 corresponds to, where identical elements are designated with the same reference numerals, and the pressure adjustment arrangement 24 additionally comprises, by way of example, a hydraulic accumulator 26. The pressure adjustment arrangement 24 further comprises a plurality of hydraulic lines 32 to 39 for connecting the pump 28 and the hydraulic accumulator 26 to the first working chamber 22 and the second working chamber 24 of the vibration damper 20. The pressure adjustment arrangement 24 preferably comprises at least two check valves 40, 42. Furthermore, the pressure adjustment arrangement 24 particularly comprises at least two valves, a first valve 44 and a second valve 46, wherein the hydraulic resistance of the valves 44, 46 is, in particular, continuously adjustable. Optionally, the valves 44, 46 are each designed to allow flow in only one direction. For example, the valves 44, 46 are solenoid valves that allow flow in one direction only.In particular, the first valve 44 can only be used in the rebound stage and the second valve 46 can only be used in the compression stage.

[0054] The pump 28 is connected, for example, via a first hydraulic line 32 to the first working chamber 20 of the vibration damper 12 and, in particular, via a second hydraulic line 34 to the second working chamber 22 of the vibration damper 12. The valves 44 and 46 are connected in series and via a third hydraulic line 36 to the first and second hydraulic lines 32 and 34, respectively, with the valves 44 and 46 being connected in parallel to the pump 28. The check valves 40 and 42 are connected in series and via a fourth hydraulic line 38 to the first and second hydraulic lines 32 and 34, respectively, with the check valves 40 and 42 being connected in parallel to the valves 44 and 46 and the pump 28.

[0055] The hydraulic accumulator 26 is connected to the third and fourth hydraulic lines 36, 38 via a fifth hydraulic line 39, with the first hydraulic connection node 48 for connecting the fifth hydraulic line 39 to the fourth hydraulic line 38 being arranged between the two check valves 40, 42. The second connection node 50 for connecting the fifth hydraulic line 39 to the third hydraulic line 36 is, by way of example, arranged between the two valves 44, 46, so that the hydraulic accumulator 26 is connected to the valves 44, 46, in particular via the first and second connection nodes 48, 50. The valves 44, 46 are, for example, continuously variable valves, such as solenoid valves.

[0056] The pressure adjustment arrangement 24 is preferably connected to the vibration damper 12 to influence its damping characteristic. The pressure adjustment arrangement 24 is preferably designed to allow active, semi-active, or passive control of the vibration damper 12. In passive control, preferably no additional pressure is applied to the vibration damper 12 via the pump 28 and / or the hydraulic accumulator 26. Furthermore, in passive control, the valves 44 and 46 preferably have a constant, unchangeable valve position. In semi-active control, preferably no additional pressure is applied to the vibration damper 12 via the pump 28 and / or the hydraulic accumulator 26, but the valve positions of the valves 44 and 46 are variable.In the case of active control, a pressure increase in at least one working chamber 20, 22 is achieved via the pump 28 and / or the hydraulic accumulator 26, whereby the valve positions of the valves 44, 46 are adjustable.

[0057] Passive or semi-active influence is achieved with the damping system 10 of the Fig. 2 For example, during a retraction movement of the working piston (pressure stage), the second working chamber 22 is hydraulically connected to the first working chamber 20 via the valves 44, 46 and the check valve 40. Preferably, the hydraulic fluid flows from the second working chamber 22 into the second hydraulic line 34 and then into the third hydraulic line 36 via the valves 44, 46. Downstream of the valves, the hydraulic fluid flows into the first hydraulic line 32 and into the first working chamber 20. A partial flow is diverted via the second connection node 50 between the two valves 44, 46 and flows via the fifth hydraulic line 39 and the first connection node 48 and the check valve 40 into the first hydraulic line 32. The damping characteristic is preferably adjusted by adjusting the flow resistance of the valves 44, 46 in the case of passive or semi-active control.

[0058] In the case of passive actuation and extension of the working piston (retraction stage), the first working chamber 20 is hydraulically connected to the second working chamber 22 via valves 44, 46 and the check valve 42. Preferably, the hydraulic fluid flows from the first working chamber 20 into the first hydraulic line 32 and then into the third hydraulic line 36 via valves 44, 46. Downstream of the valves, the hydraulic fluid flows into the second hydraulic line 34 and into the second working chamber 22. A partial flow is diverted via the second connecting node 50 between the two valves 44, 46 and flows via the fifth hydraulic line 39 and the first connecting node 48 and the check valve 42 into the second hydraulic line 34.

[0059] In the case of active control, for example, a pressure increase occurs in one of the working chambers 20, 22, particularly without movement of the working piston 16 within the working cylinder 14. Preferably, in the case of active control or activation of the damper, in addition to the pressure increase in the working chambers 20, 22 caused by the movement of the working piston 16, a further pressure increase occurs by means of the pump 28 and the hydraulic accumulator 26. The pump 28 is preferably designed such that it can be operated in the direction of the first hydraulic line 32 or the second hydraulic line 34. When operating in the direction of the first hydraulic line 32, this line is connected to the fluid outlet of the pump 28.In particular, if the direction of rotation of the pump is changed, it can be operated in the other direction, for example in the direction of the second hydraulic line 34, so that the first hydraulic line 32 is connected to the fluid inlet and the second hydraulic line 34 to the fluid outlet of the pump 28.

[0060] Active pressure increase within the first working chamber 20 preferably occurs when the pump 28 is operated in the direction of the first hydraulic line 32. Additionally, the hydraulic accumulator 26 is preferably connected to the pump 28, with the hydraulic fluid flowing from the hydraulic accumulator 26 into the fourth hydraulic line 38 via the check valve 42 into the second hydraulic line 34. From the second hydraulic line 34, the hydraulic fluid preferably flows into the fluid inlet of the pump 28 and then into the first hydraulic line 32. The hydraulic fluid introduced into the first hydraulic line 32 via the hydraulic accumulator 26 and the pump 28 ensures a pressure increase within the first hydraulic line 32.A partial flow is returned from the first hydraulic line 32 via the third hydraulic line 36 and the first valve 44 to the hydraulic accumulator 26, while the remaining partial flow is supplied via the first hydraulic line 32 to the first working chamber 20 and generates a pressure increase.

[0061] Active pressure increase within the second working chamber 22 preferably occurs when the pump 28 is operating in the direction of the second hydraulic line 34. Additionally, the hydraulic accumulator 26 is preferably connected to the pump 28, with the hydraulic fluid flowing from the accumulator 26 into the fourth hydraulic line 38 via the check valve 40 into the first hydraulic line 32. From the first hydraulic line 32, the hydraulic fluid preferably flows into the fluid inlet of the pump 28 and then into the second hydraulic line 34. The hydraulic fluid introduced into the second hydraulic line 34 via the pump 28 through the accumulator 26 ensures a pressure increase within the second hydraulic line 34.A partial flow is returned from the second hydraulic line 34 via the third hydraulic line 36 and the second valve 46 to the hydraulic accumulator 26, while the remaining partial flow is supplied via the second hydraulic line 34 to the second working chamber 22 and generates a pressure increase.

[0062] The damping system 10 preferably comprises a control / regulation device 52. The control / regulation device 56 is, by way of example, connected to the pump 28, in particular the motor 30, and the first and second valves 44, 46 for control / regulation and for transmitting data. The damping system 10 of the Fig. 2 also features a control / regulating device 56 according to Fig. 1, which for the sake of clarity is only shown in Fig. 1 is shown.

[0063] The control / regulating device 56 is designed and configured to control the valve position of valves 44, 46 and / or the volume flow rate of pump 28 as a function of a predefinable force setpoint acting on the piston rod 18. Preferably, the control / regulating device 56 is designed to determine the frequency of pressure fluctuations within the damping system. In particular, the control / regulating device 56 is connected to the compensation devices 52, 54 in such a way that it adjusts the natural frequency of the compensation devices as a function of the determined frequency of the pressure fluctuations within the damping system. In particular, the control / regulating device 56 is designed to adjust the natural frequency of the compensation devices 52, 54 so that it corresponds to the determined frequency of the pressure fluctuations within the damping system.

[0064] Fig. Figure 3 shows a schematic representation of a compensation device 52, 54. The compensation device 52, 54 has, by way of example, a volume 60 filled with hydraulic fluid, which is formed, for example, in a container 64. The container 64 is preferably a hollow cylinder, a hollow sphere, or a container with a square, in particular rectangular, cross-section. The volume 60 formed in the container 64 is preferably supplied via an inlet 62 to the hydraulic fluid. Fig. The inlet 62 is connected to the hydraulic lines 32 and 34 (not shown). The inlet 62 is, for example, formed in a preferably tubular inlet housing 66. The inlet 62 has, for example, a round, square, circular, or rectangular cross-section. In particular, the inlet 62 has a direct fluid connection with the volume 60 and another direct fluid connection with one of the hydraulic lines 32 and 34. A movable wall element 70 is arranged within the inlet 62. The movable wall element 70 is preferably mounted so as to be movable relative to the inlet 62, in particular to the inlet housing 66. Preferably, the wall element 70 is movable from a first position, in which the inlet 62 has a first length, to a second position, in which the inlet 62 has a second length.The length of the inlet 62 preferably refers to the flow path within the hydraulic fluid within the inlet 62, which preferably extends from the inlet 68 of the inlet 62 to the outlet into the container 64. The wall element 70 is preferably arranged within the inlet housing 66 such that it is infinitely movable and preferably lockable in a desired position. In the exemplary embodiment of the... Fig. 3 The movable wall element 70 is exemplified as a pipe element that can be inserted into the inlet 62, so that the length of the inlet 62 is changed, in particular increased or decreased. The compensation device 52, 54 is preferably connectable to one of the hydraulic lines 32, 34 via a connection area 68 designed as an inlet. The connection area 68 is in particular arranged at an end region of the inlet 62. The inlet 62 has, for example, a flow deflection, which in particular comprises at least a right angle.

[0065] The wall element 70 is preferably movable within the inlet 62 such that the flow cross-section is changed, in particular increased or decreased. Preferably, the wall element 70 is arranged and designed such that it can be moved into a locking position in which the entire flow cross-section of the inlet 62 is blocked, so that no hydraulic fluid can flow between the volume 66 and the hydraulic lines.

[0066] Fig. Figure 4 shows a further embodiment of a compensation device 52, 54, which is essentially the same as the Fig. 3 corresponds, where identical elements are provided with the same reference numerals. In contrast to the embodiment of the Fig. 3 indicates the compensation facility 52, 54 of the Fig. 4. A wall element 70, designed as a slide, is arranged within the inlet 62. The wall element 70 is preferably arranged completely within the inlet 62 and is movable via an actuating element 74, in particular a rod. The actuating element 74 preferably extends outwards through an opening in the inlet housing 66. The wall element 70 is preferably arranged within the inlet housing 66 such that it is infinitely movable and preferably lockable in a desired position. In the exemplary embodiment of the Fig. 4. The movable wall element 70 is, by way of example, movable within the inlet 62 such that the flow cross-section of the inlet 62 is changed, in particular increased or decreased. Preferably, the wall element 70 seals fluid-tight against the housing 66 of the inlet 62 on the inlet side of the inlet.

[0067] Fig. Figure 5 shows a further embodiment of a compensation device 52, 54, which is essentially the same as the Fig. 3 corresponds, where identical elements are provided with the same reference numerals. In contrast to the embodiment of the Fig. 3 indicates the compensation facility 52, 54 of the Fig. 5. A wall element 70 is arranged within the volume 60. By way of example, the movable wall element 70 forms a section or the entire bottom wall of the container 64 in which the volume 60 is located. Preferably, the wall element 70 is designed as a piston and connected to a piston rod 74 that projects outwards through an opening in the container. Via the piston rod 74, the wall element 70 is movable in the axial direction within the container 64 and defines a first volume 60a, located away from the piston rod, and a second volume 60b, located on the side of the piston rod. Movement of the wall element 70 causes a change in the size of the volumes 60a and 60b. The volume 60a, located away from the piston rod, is preferably directly connected to and adjacent to the inlet 62.

[0068] The wall element 70 of the Fig. 3 to 5 is, for example, plate-shaped, bowl-shaped, or tubular. For example, wall element 70 has a membrane. Wall element 70 preferably forms an inner wall region of the inlet 62 or the container 64. The inlet 62 of the Fig. 3 to 6 preferably has a smaller cross-section than container 64. Reference symbol list 10 Damping system 12 vibration dampers 14 working cylinders 16 working pistons 18 Piston rod 20 first workroom 22 second workroom 24 Pressure setting arrangement 26 hydraulic accumulators 28 Pump 30 engine 32 first hydraulic line 34 second hydraulic line 36 third hydraulic line 38 fourth hydraulic line 39 fifth hydraulic line 40 Check valve 42 Check valve 44 first valve 46 second valve 48 first connecting node 50 second connection node 52 Compensation facility 54 Compensation facility 56 Control / regulating device 58 Pressure sensor 60 volume 62 Inflow 64 containers 66 Inlet housings 68 Connection area 70 movable wall element 72 Opening 74 Actuator

Claims

[1] Damping system (10) for a motor vehicle comprising a working cylinder (14) that is at least partially filled with hydraulic fluid, a working piston (16) arranged within the working cylinder (14) and axially movable, with a piston rod (18), wherein the working piston (16) divides the working cylinder (14) into a first working chamber (20) and a second working chamber (22), and a pressure setting arrangement (24) for setting the pressure in the first and second working chambers (20, 22), wherein the pressure setting arrangement (24) comprises a pump (28) which is connected to the first and second working chambers (20,22) via hydraulic lines (32-39), wherein the pressure setting arrangement (24) has at least one compensation device (52, 54) for reducing pressure fluctuations in the damping system (10), which is connected to the pump (28) and the working cylinder (14) which is at least partially filled with hydraulic fluid, characterized by , that the compensation device (52, 54) is designed and configured such that the natural frequency of the compensation device (52, 54) is adjustable during operation of the damping system, and wherein the damping system (10) has a control / regulating device (56) which is designed to determine the frequency of the pressure fluctuations within the damping system (10) and to adjust the natural frequency of the compensation device (52, 54) to correspond to the determined frequency of the pressure fluctuations. [2] Damping system (10) according to claim 1, wherein the compensation device (52, 54) has a volume (60) filled with hydraulic fluid and wherein the compensation device (52, 54) is designed and configured such that the size of the volume (60) is adjustable. [3] Damping system (10) according to one of the preceding claims, wherein the compensation device (52, 54) has a volume (60) filled with hydraulic fluid and an inlet (62) via which the volume can be connected to the pump (28) and / or the working cylinder (14) and wherein the compensation device (52, 54) is designed and configured such that the flow cross-section and / or the length of the inlet (62) is adjustable. [4] Damping system (10) according to one of the preceding claims, wherein the compensation device (52, 54) has at least one movable wall element (70) which is arranged inside the inlet (62) and / or inside a housing (64) forming the volume (66). [5] Damping system (10) according to one of the preceding claims, wherein the control / regulating device (56) is connected to the compensation device (52, 54) in such a way that it controls / regulates the natural frequency of the compensation device (52, 54) depending on the determined frequency of the pressure fluctuations within the damping system (10). [6] Damping system (10) according to one of the preceding claims, wherein the damping system (10) has at least one sensor (58) for determining the frequency of the pressure fluctuations of the damping system (10), which is connected to the control / regulation device (56) for transmitting the determined frequency. [7] Damping system (10) according to one of the preceding claims, wherein the pressure setting arrangement (24) comprises a hydraulic accumulator (26), a first valve (44) and a second valve (46), each of which is connected to the first and second working chambers (20, 22) via hydraulic lines (32-29), and wherein the valves (44, 46) are designed such that the valve position is adjustable, in particular continuously. [8] Motor vehicle comprising a chassis and a damping system (10) attached thereto according to one of the preceding claims. [9] Method for operating a damping system (10) for a motor vehicle, wherein the damping system (10) comprises: a working cylinder (14) that is at least partially filled with hydraulic fluid, a working piston (16) arranged within the working cylinder (14) and axially movable, with a piston rod (18), wherein the working piston (16) divides the working cylinder (14) into a first working chamber (20) and a second working chamber (22), and a pressure setting arrangement (24) for setting the pressure in the first and second working chambers (20, 22), wherein the pressure setting arrangement comprises a pump (28) which is connected to the first and second working chambers (20, 22) via hydraulic lines (32-39) and wherein the pressure setting arrangement (24) comprises at least one compensation device (52, 54) for reducing pressure fluctuations in the damping system, characterized by , that the frequency of the damping system (10) is determined and the natural frequency of the compensation device (52, 54) is controlled / regulated in the operation of the damping system (10) such that it corresponds to the determined frequency of the pressure fluctuations. [10] Method according to claim 9, wherein the natural frequency of the compensation device (52, 54) is controlled / regulated depending on the determined frequency. [11] Method according to one of claims 9 or 10, wherein the determination of the frequency of the damping system (10) is model-based using a pre-defined pump model that includes the frequency of the pressure fluctuations of the damping system over the operating range of the pump (28). [12] Method according to any one of claims 9 to 11, wherein the compensation device (52, 54) has a volume (60) filled with hydraulic fluid and wherein the size of the volume (60) is adjusted to adjust the natural frequency of the compensation device (52, 54). [13] Method according to any one of claims 9 to 12, wherein the compensation device (52, 54) has a volume (60) filled with hydraulic fluid and an inlet (62) through which the volume is connected to the pump (28) and / or the working cylinder (14) and wherein the flow cross-section of the inlet (62) is adjusted to adjust the natural frequency of the compensation device (52, 54). [14] Computer program product for controlling the method according to any one of claims 9 to 13.

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