Linear electric cylinder

Abstract

An electric cylinder for a vehicle wheel suspension includes a housing including a housing wall; a motor configured to rotate the screw about its axis, thereby linearly moving the nut along the screw; a piston rod assembly slidably coupled to the housing, where the piston rod assembly includes a piston disposed at a predetermined distance from the housing wall such that a first cavity is formed between the piston and the housing wall, and where the piston rod assembly defines a second cavity, a second cavity configured to receive the screw assembly, where the nut is coupled to the piston rod assembly such that linear movement of the nut moves the piston rod assembly between a retracted position and an extended position; and a fluid exchange device configured to exchange at least a portion of the fluid between the first chamber and the second chamber based on movement of the piston.

Description

Technical Field

[0001] The invention relates to an electric cylinder for a vehicle wheel suspension, and in particular to an electric cylinder for a wheel suspension having at least a variable track width adjustable between a narrow track and a wide track. Background Art

[0002] WO2016058060A1 describes a wheel suspension comprising a frame adapted to be connected to a vehicle body and comprising a first wheel and a second wheel which together define a track width. The first wheel is connected to the frame via a first set of electric cylinders and the second wheel is connected to the frame via a second set of electric cylinders, so that the track width can be adjusted between narrow track widths by operating the electric cylinders, wherein the first set of electric cylinders overlaps the second set of electric cylinders in the lateral direction of the vehicle.

[0003] In practice, some electric cylinders will be subject to lateral forces because the electric cylinder can be fixed in various locations, such as a frame, a steering knuckle, a suspension arm, or another electric cylinder, so that the electric cylinder is oriented essentially horizontally. The lateral force is at an angle relative to the direction of motion of the electric cylinder, hence the name.

[0004] The electric cylinder comprises a housing having a housing wall, a motor mechanically coupled to a screw assembly having a screw and an associated nut; wherein the motor is configured to rotate the screw about its axis, thereby causing the nut to move linearly along the axis of the screw. The electric cylinder comprises a piston rod assembly slidably coupled to the housing, wherein the piston rod assembly comprises a piston rod arranged at a predetermined distance from the housing wall, such that a first chamber is formed between the piston rod and the housing wall, and wherein the piston rod assembly defines a second chamber configured to accommodate the screw assembly. The nut is coupled to the piston rod assembly such that linear movement of the nut causes the piston rod assembly to move between a retracted position and an extended position, wherein in the extended position the piston rod assembly protrudes substantially outwardly from the housing. In order to extend life and provide optimal performance, particularly because lateral forces can cause severe wear if the electric cylinder is not properly maintained, the first chamber and the second chamber are provided with a fluid containing at least a gas phase and a liquid phase.

[0005] Various methods have been evaluated, but none of them provide a robust and operationally reliable method of lubricating the electric cylinder. Lubricating the electric cylinder using a grease nipple is one method, but requires a lot of maintenance and has a low operational reliability, especially since this method requires regular maintenance. External lubrication systems are not robust enough and their failure can significantly shorten the life of the electric cylinder. Moreover, the implementation of external lubrication systems in wheel suspensions with variable track width is expensive and complex. CN111288135 and EP2491273 describe electric cylinders with lubrication devices. Summary of the invention

[0006] The object of the present invention is to propose an electric cylinder which has a robust and operationally reliable manner in which it lubricates itself in a self-contained manner.

[0007] To this end, the present invention provides an electric cylinder characterized by having a fluid exchange device configured to exchange at least part of the fluid between a first chamber and a second chamber based on movement of a piston.

[0008] The advantages are based on the recognition that the combination of rotational and linear motion of the electric cylinder, for example by moving from a retracted position to an extended position to turn a vehicle, changes the respective volumes of the first chamber and the second chamber. The volume of the first chamber is proportional to the position of the piston rod assembly in the housing. The volume of the first chamber is also proportional to the difference in the outer surface area of ​​the piston rod assembly relative to the inner surface area of ​​the housing wall, i.e. the piston rod assembly and the housing wall define the side of the first chamber. In particular, the volume of the first chamber is greater when the piston rod assembly is in the retracted position than when the piston rod assembly is in the extended position. The difference in volume of the first chamber in the retracted position and the extended position, in particular the reduction in volume when moving from the retracted position to the extended position, pressurizes the fluid in the first chamber. At the same time, the volume of the second chamber changes proportionally and inversely relative to the volume of the first chamber. Therefore, when the piston rod assembly moves from the retracted position to the extended position, the volume of the second chamber increases. The increase in the volume of the second chamber reduces the pressure of the fluid in the second chamber. In this way, when the piston rod assembly moves, a pressure difference is generated between the first chamber and the second chamber. The pressure differential causes fluid to move from the chamber with the higher pressure to the chamber with the lower pressure. Obviously, moving from the extended position to the retracted position increases the volume of the first chamber and decreases the volume of the second chamber respectively and the above pressure differential is reversed, causing fluid to flow from the second chamber to the first chamber. Therefore, the pressure differential caused by moving the piston rod assembly during operation provides a simple, robust and self-contained way to reliably lubricate the electric cylinder.

[0009] Preferably, the fluid exchange means comprises a first fluid channel and a second fluid channel formed in the piston, which fluidly connect the first chamber and the second chamber respectively. The first and second fluid channels allow the fluid to flow from the first chamber to the second chamber and vice versa in a relatively simple manner. More preferably, the first and second fluid channels comprise at least 0.5 mm 2 cross-sectional area, preferably at least 10 mm 2 The inventors have found that a thickness of at least 0.5 mm 2 The cross-sectional areas of the first and second fluid passages provide a balanced pressure differential and flow rate between the first and second chambers. More preferably, the first and second fluid passages are holes through the piston wall. Such holes are durable, easy to manufacture, and easy to clean in the event that maintenance of the electric cylinder is required.

[0010] Preferably, the fluid exchange device further comprises a first shut-off device and a second shut-off device, which are arranged accordingly so that the first shut-off device allows the fluid to flow from the first chamber to the second chamber through the first fluid channel and prevents the fluid from flowing from the second chamber to the first chamber, and the second shut-off device only allows the fluid to flow from the second chamber to the first chamber through the second channel. In this way, a circulating flow of the fluid is generated inside the electric cylinder. The circulating flow is advantageous because the fluid is forced to flow in a direction that reduces stagnation of the fluid at certain locations, which improves the lubrication of the electric cylinder.

[0011] Preferably, the first fluid channel and the corresponding first shut-off device are arranged in an upper section of the piston wall, preferably in the uppermost section, and wherein the second fluid channel and the corresponding first shut-off device are arranged in a lower section of the piston wall, preferably in the lowermost section. This has the advantage that the electric cylinder arranged in a wheel suspension with variable track width is usually oriented in a substantially horizontal manner. By providing the first fluid channel and the corresponding first shut-off device and the second fluid channel and the corresponding second shut-off device in the uppermost section and in the lower section, the circulating flow comprises an upward and a downward component, since the movement of the electric cylinder to the extended position forces the fluid upwards, through the first fluid channel into the second channel. Similarly, when moving from the extended position to the retracted position, the fluid is forced downwards from the second chamber, through the second fluid channel into the first chamber.

[0012] Preferably, the first shut-off device covers the first fluid channel and is arranged on one side of the piston wall defining the second chamber, wherein the second shut-off device covers the second fluid channel and is arranged on one side of the piston wall defining the first chamber. Preferably, the first shut-off device and the second shut-off device are made of elastic material. In this way, when pressure is applied from one side of the shut-off device, the fluid can open the fluid channel. The elasticity of the shut-off device allows the shut-off device to open the fluid channel by bending in a direction away from the applied pressure. In addition, when the pressure direction on the fluid is reversed, for example when the second chamber is pressurized relative to the first chamber, the elasticity of the shut-off device also allows the shut-off device to close the fluid channel. More preferably, the elastic material is an elastomer.

[0013] Preferably, the piston rod has a proximal end and a distal end, wherein the fluid exchange device is arranged near the proximal end of the piston rod. In this way, the fluid exchange device is allowed to have a maximum stroke in the electric cylinder, thereby also circulating a maximum amount of fluid with respect to the electric cylinder.

[0014] Preferably, the electric cylinder further comprises a set of bearings arranged between the housing and the piston, wherein the set of bearings comprises a first bearing and a second bearing, wherein the first bearing is arranged at a proximal end of the piston, and wherein the second bearing is located at a distal end of the piston, wherein the set of bearings is configured to slidably support the piston rod assembly in the housing.

[0015] Preferably, the electric cylinder further comprises a seal arranged between the piston and the housing. Even if the first and second chambers are fluidically connected, the seal prevents fluid from flowing through other openings, such as the opening between the piston and the housing. This further improves the lubrication of the electric cylinder.

[0016] Preferably, the electric cylinder further comprises another seal disposed between the motor and the second chamber, the other seal being configured to substantially prevent fluid from flowing from the second chamber to the motor.Although the fluid may be used to cool the motor, it is preferred that the fluid remains in the first and second chambers.

[0017] Preferably, the electric cylinder further comprises a first connecting device and a second connecting device respectively arranged at the proximal end and the distal end of the electric cylinder, so that the electric cylinder can be pivotally connected to any one of the vehicle frame, the suspension strut and the steering knuckle.

[0018] Preferably, the electric cylinder further comprises a suspension strut support disposed at a distal end of the housing, the suspension strut support being configured to rigidly support the suspension support. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are used to illustrate currently preferred non-limiting exemplary embodiments of the device of the present invention. The above and other advantages of the features and objects of the present invention will become more apparent and the present invention will be better understood through the following detailed description when explained in conjunction with the accompanying drawings, in which:

[0020] Figure 1 shows a perspective view of an electric cylinder according to a preferred embodiment;

[0021] Figure 2 Shows Figure 1 A cross-sectional view of the electric cylinder shown;

[0022] Figure 3 Shows Figure 2 An enlarged view of a portion of the electric cylinder shown in FIG. DETAILED DESCRIPTION

[0023] Figure 1A perspective view of an electric cylinder 100 for a vehicle wheel suspension according to a preferred embodiment is shown. Preferably, the electric cylinder 100 is used for a wheel suspension with at least a variable wheelbase, which can be adjusted between a narrow wheelbase and a wide wheelbase. A vehicle with a variable wheelbase can have three or more wheels. In a configuration with three wheels, a single wheel will be placed at the front or rear, while two wheels are arranged at the rear or front, respectively, at a certain distance from each other (the distance is in the transverse direction of the vehicle). The two wheels define the wheelbase. The larger the wheelbase, the wider the vehicle and the more stable the grip. However, the larger the wheelbase, the more space the vehicle takes up. The narrower the wheelbase, the narrower the vehicle and the less stable the grip. However, the narrower the wheelbase, the less space the vehicle takes up. Obviously, other factors also affect the stability of the vehicle. The electric cylinder 100 can also be applied to vehicles with four wheels, such as transport trucks or buses. Most commercial vehicles have four wheels. The first two of the four wheels are usually steerable here, so that the direction of travel can be determined and the vehicle can be steered. Although the electric cylinder is specifically designed for commercial vehicles with three or four wheels, it is obvious that the electric cylinder can also be applied to special vehicles designed for specific reasons and therefore may have a specific number of wheels other than three or four wheels. However, based on this description, a person skilled in the art will be able to apply the electric cylinder to vehicles of other configurations.

[0024] Figure 2 Shows Figure 1 The electric cylinder 100 has a proximal end P and a distal end D. Figure 2 The electric cylinder 100 is particularly shown to include a housing 110. The housing 110 includes a housing wall 111. Near the proximal end P, the electric cylinder 100 may include a first connection device 112. Near the distal end D, the electric cylinder may include a second connection device 113. In this way, the electric cylinder 100 can be pivotally connected to any one of the vehicle frame, suspension strut and steering knuckle. In addition, in order to rigidly support the suspension support, a suspension strut support 114 can be arranged near any one of the proximal end and the distal end.

[0025] The electric cylinder 100 further comprises an electric motor 120. Preferably, the electric motor 120 is arranged near the proximal end P of the electric cylinder 100. The electric motor 120 is mechanically coupled to a screw assembly. The screw assembly comprises a screw 130 and an associated nut 140. Preferably, the screw 130 is a cylindrical shaft having threads on its outer wall. The associated nut 140 comprises a through hole through which the screw passes. A thread or other guide corresponding to the thread of the screw 130 is provided on the inner side of the through hole. When the electric motor 120 rotates, the mechanical coupling causes the screw 130 to rotate about its axis, thereby causing the nut 140 to move linearly along the axis of the screw. In other words, the screw converts the rotational motion of the electric motor 120 into a linear motion of the nut 140.

[0026] The electric cylinder 100 further includes a piston rod assembly 150 slidably coupled to the housing 110. The piston rod assembly 150 includes a piston rod tube 151 disposed at a predetermined distance from the housing wall 111. The predetermined distance I is measured radially from the center of the electric cylinder 100. Because the piston rod tube 151 is disposed at a certain distance from the housing wall 111, a first cavity A is formed between the piston rod tube and the housing wall. Figure 1 It can be seen that the electric cylinder wall 110 is at least partially cylindrical. Preferably, the piston rod assembly is also at least partially cylindrical. In this case, the outer area of ​​the piston wall is smaller than the inner area of ​​the electric cylinder wall 111, thereby forming a first chamber A. In addition, the piston rod assembly 150 is hollow and defines a second chamber B that accommodates the screw assembly. The nut 140 is coupled to the piston rod assembly 150 so that the linear movement of the nut causes the piston rod assembly 140 to move between the retracted position and the extended position. In other words, the piston rod assembly 150 slides relative to the housing 110. In the extended position, the piston rod assembly 150 substantially protrudes outward from the housing. Figure 1 and Figure 2 The piston rod assembly 150 is shown in a retracted position, in which the electric cylinder housing wall 111 and the piston rod assembly 150 substantially completely overlap each other as viewed in the longitudinal direction of the electric cylinder 100 .

[0027] In addition, the first chamber A and the second chamber B are provided with a fluid including at least a gas phase and a liquid phase. The liquid phase of the fluid may be lubricating oil, and the gas phase may be dry air or an inert gas such as nitrogen. The electric cylinder 100 further includes a fluid exchange device 160, 165, which is configured to exchange at least part of the fluid between the first chamber A and the second chamber B based on the movement of the piston rod assembly 150. By moving the piston rod assembly 150 from the retracted position to the extended position, such as turning the vehicle, the volumes of the first chamber A and the second chamber B relative to each other can be changed because the volume of the first chamber A is proportional to the position of the piston rod assembly 150 in the housing 110. In particular, the volume of the first chamber A when the piston rod assembly is in the retracted position is greater than the volume of the first chamber A when the piston rod assembly is in the extended position. The difference in volume of the first chamber between the retracted position and the extended position, in particular the reduction in volume when moving from the retracted position to the extended position, pressurizes the fluid in the first chamber A. At the same time, the volume of the second chamber B changes proportionally and inversely with respect to the volume of the first chamber A because the volume of the second chamber B increases after the piston rod assembly 150 moves from the retracted position to the extended position. The increase in the volume of the second chamber B reduces the pressure of the fluid in the second chamber. Thus, when the piston rod assembly 150 moves, a pressure differential is created between the first chamber A and the second chamber B. The pressure differential causes the fluid to move from the chamber with the higher pressure to the chamber with the lower pressure. Obviously, moving from the extended position to the retracted position expands the volume of the first chamber A, correspondingly reduces the volume of the second chamber B, and the above-mentioned pressure differential is reversed, causing the fluid to flow from the second chamber B to the first chamber A. Therefore, the pressure differential caused by moving the piston rod assembly 150 during operation provides a simple, robust and self-sufficient way to reliably lubricate the electric cylinder 100.

[0028] According to another preferred embodiment, the electric cylinder 100 further includes a set of bearings 181, 182 arranged between the housing 110 and the piston rod assembly 150. The set includes a first bearing 181 and a second bearing 182, wherein the first bearing 181 is arranged near the proximal end 151p of the piston wall 151, and the second bearing 182 is arranged near the distal end 151d of the piston rod. This allows the piston rod assembly 150 to be slidably supported in the housing 110.

[0029] Figure 2 Further shown are fluid exchange devices 160, 165, which include a first fluid channel 160 and a second fluid channel 165 formed in the piston rod tube 151. In the illustrated embodiment, the fluid exchange devices 160, 165 are arranged near the proximal end 151p of the piston. In this way, the piston rod assembly 150 is allowed maximum travel within the electric cylinder 100, and therefore the maximum amount of fluid is circulated with respect to the electric cylinder.

[0030] The first fluid channel 160 and the second fluid channel 165 fluidly connect the first chamber A and the second chamber B, respectively. The first fluid channels 160, 165 allow the fluid to flow from the first chamber A to the second chamber B and back in a relatively simple manner. Preferably, the first fluid channel 160 and the second fluid channel 165 are holes through the piston, such as Figure 2 As shown. Such a hole is durable, easy to manufacture, and easy to clean in the event that maintenance of the electric cylinder is required. The hole, or in other words, the through hole extends completely through the piston rod tube 151. In order to provide a balanced pressure difference and flow rate between the first chamber and the second chamber, the first and second fluid passages include at least 0.5 mm 2 cross-sectional area, preferably at least 10 mm 2 .

[0031] Figure 3 It shows that Figure 2 An enlarged view of a portion of electric cylinder 100 is shown.

[0032] Figure 3 It is shown that the circumferential area of ​​the piston rod assembly 150 may vary. For example, the portion of the piston rod assembly 150 that houses the coupling device 121, which is indicated by the reference numeral 151 in the figure, and which is configured to mechanically couple the motor 120 to the screw assembly (particularly to the screw 130 of the screw assembly), can have a larger circumferential area relative to the portion of the barrel that slidably extends outside the electric cylinder 100. It should be noted that any suitable coupling device 121 can be used.

[0033] Figure 3 The enlarged view of shows that the fluid exchange device includes a first fluid channel 160 and a second fluid channel 165 formed in the piston rod tube 151, which fluidly connect the first chamber A and the second chamber B, respectively.

[0034] The fluid exchange device further comprises a first shut-off device 170 and a second shut-off device 175, which are arranged respectively such that the first shut-off device 170 substantially exclusively allows fluid to flow from the first chamber A to the second chamber B through the first fluid channel, and such that the second shut-off device 175 substantially exclusively allows fluid to flow from the second chamber B to the first chamber A through the second channel. In other words, the first shut-off device 170 blocks fluid from flowing from the second chamber B to the first chamber through the first fluid channel 160. The second shut-off device 175 blocks fluid from flowing from the first chamber A to the second chamber B through the second fluid channel 165.

[0035] Preferably, Figure 3The first shut-off device 170 is shown to cover the first fluid channel 160 and is arranged on one side of the piston rod tube 151 defining the second chamber B, i.e., the inner side of the piston rod assembly 150. Preferably, the second shut-off device 175 covers the second fluid channel 165 and is arranged on one side of the piston defining the first chamber A, i.e., the outer side of the piston rod assembly 150. The first shut-off device 170 and the second shut-off device 175 are preferably made of an elastic material. In this way, when pressure is applied from one side of the shut-off devices 170, 175, the fluid can open the fluid channels 160, 165. For example, when the piston rod assembly moves to the extended position, the pressure in the first chamber A increases. The increased pressure allows the elastic first shut-off device 170 to be biased to the open position, in which the first shut-off device 70 no longer covers the first fluid channel 160 and allows the fluid to flow from the first chamber to the second chamber B. The elasticity of the shut-off device 165 allows the shut-off device to open the first fluid channel 160 by bending in a direction away from the applied pressure. In addition, the elasticity of the shut-off devices 170, 175 also allows the shut-off devices to close the fluid passage when the pressure direction on the fluid is reversed, for example when the piston rod assembly 150 is moved to the retracted position and the second chamber B is pressurized relative to the first chamber. Preferably, the elastic material is an elastomer. Obviously, the first and second shut-off devices can also be arranged in the first and second fluid passages, respectively.

[0036] Preferably, the first fluid channel 160 and the corresponding first shut-off device 170 are arranged in the upper section of the piston, preferably in the uppermost section. The second fluid channel 165 and the corresponding first shut-off device 175 are preferably arranged in the lower section of the piston, preferably in the lowermost section. This has the advantage that the electric cylinder 100 arranged in a wheel suspension with a variable wheelbase is usually oriented in a substantially horizontal manner. By arranging the first fluid channel 160 and the corresponding first shut-off device 170 and the second fluid channel 165 and the corresponding second shut-off device 175 in the uppermost section and the lower section, the circulating flow includes an upward and a downward component, because the movement of the electric cylinder 100 to the extended position forces the fluid upward, through the first fluid channel into the second channel. Similarly, when moving from the extended position to the retracted position, the fluid is forced downward from the second chamber B, through the second fluid channel 165 into the first chamber A.

[0037] Figure 3 It is further shown that the electric cylinder 100 may also include a seal 190 disposed between the piston rod tube 151 and the housing 110, so that even if the first chamber A and the second chamber B are fluidly connected, the seal 190 will prevent fluid from flowing through other openings, such as the opening between the piston rod tube 152 and the housing 110 near the proximal end of the piston rod assembly and the housing. In addition, the electric cylinder may also include another seal 195 disposed between the motor 120 and the second chamber B, which is configured to substantially prevent fluid from flowing from the second chamber B to the motor.

[0038] The description and drawings illustrate only the principles of the invention. Therefore, it should be understood that those skilled in the art will be able to design various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within the scope thereof. In addition, all examples described herein are primarily and explicitly intended to be used for teaching purposes only to help the reader understand the principles of the invention and the concepts contributed by the inventors to further develop the art, and should be interpreted as not being limited to these specifically enumerated examples and conditions. In addition, all statements describing the principles, aspects, and embodiments of the invention herein, as well as specific examples thereof, are intended to cover their equivalents.

[0039] It should be noted that the above embodiments illustrate rather than limit the present invention, and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference symbol between brackets shall not be interpreted as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "one" or "an" in front of an element does not exclude the presence of multiple such elements. The present invention can be implemented by hardware including several different elements and a suitably programmed computer. In the claims that list several means, several of these means can be implemented by the same hardware. The use of words such as "first", "second" and "third" does not indicate any order or priority. For convenience, these words should be interpreted as names.

[0040] In the present invention, expressions such as “including”, “comprising”, “having”, “may include”, “may include” or “may have” indicate the existence of corresponding features, but do not exclude the existence of additional features.

[0041] Although the principles of the present invention have been described above in conjunction with specific embodiments, it should be understood that this description is only intended as an example rather than a limitation on the scope of protection determined by the appended claims.

Claims

1. An electric cylinder (100) for a vehicle wheel suspension, comprising: - a housing (110) comprising a housing wall (111); - an electric motor (120) mechanically coupled to a screw assembly having a screw (130) and an associated nut (140), wherein the electric motor is configured to rotate the screw about its axis, thereby causing the nut (140) to move linearly along the axis of the screw; - a piston rod assembly (150) slidably coupled to the housing, wherein the piston rod assembly comprises a piston (151) arranged at a predetermined distance from the housing wall (111) such that a first chamber (A) is formed between the piston and the housing wall, and wherein the piston rod assembly defines a second chamber (B) configured to accommodate the screw assembly, wherein the nut (140) is coupled to the piston rod assembly such that linear movement of the nut causes the piston rod assembly to move between a retracted position and an extended position, wherein in the extended position the piston rod assembly substantially protrudes outwardly from the housing; wherein the first chamber and the second chamber are provided with a fluid comprising at least a gas phase and a liquid phase; - A fluid exchange device (160, 165) configured to exchange at least part of the fluid between the first chamber and the second chamber based on the movement of the piston, wherein the fluid exchange device includes a first fluid channel (160) and a second fluid channel (165) formed in the piston, which fluidly connect the first chamber (A) and the second chamber (B), respectively.

2. The electric cylinder (100) according to the preceding claim, wherein: The cross-sectional area of ​​the first fluid channel and the second fluid channel is at least 0.5 mm 2 , preferably at least 10 mm 2 .

3. An electric cylinder according to any one of the preceding claims, wherein: The first fluid passage (160) and the second fluid passage (165) are holes through the piston.

4. The electric cylinder (100) according to any one of the preceding claims, wherein: The fluid exchange device further comprises a first shut-off device (170) and a second shut-off device (175), wherein the first shut-off device and the second shut-off device are arranged accordingly so that the first shut-off device (170) exclusively allows fluid to flow from the first chamber (A) to the second chamber (B) through the first fluid channel, and the second shut-off device (175) exclusively allows fluid to flow from the second chamber (B) to the first chamber (A) through the second channel.

5. The electric cylinder (100) according to the preceding claim, wherein: The first shut-off device (170) covers the first fluid channel and is arranged on one side of the piston defining the second chamber (B), and wherein the second shut-off device (175) covers the second fluid channel and is arranged on one side of the piston defining the first chamber (A).

6. The electric cylinder (100) according to any one of the preceding claims 4-5, wherein: The first shut-off device (170) and the second shut-off device (175) are made of elastic material.

7. The electric cylinder (100) according to the preceding claim, wherein: The elastic material is an elastomer.

8. The electric cylinder (100) according to any one of the preceding claims, wherein: The piston (151) has a proximal end (151p) and a distal end (151d), wherein the fluid exchange device (160, 165) is arranged near the proximal end (151p) of the piston.

9. The electric cylinder (100) according to any one of the preceding claims, further comprising a set of bearings (180) arranged between the housing and the piston, wherein the set of bearings comprises a first bearing and a second bearing, wherein the first bearing is arranged at a proximal end of the piston, and wherein the second bearing is located at a distal end of the piston, wherein the set of bearings is configured to slidably support the piston rod assembly in the housing.

10. The electric cylinder (100) according to any one of the preceding claims, further comprising a seal (190) arranged between the piston (151) and the housing (110).

11. The electric cylinder (100) according to any one of the preceding claims, comprising a further seal (195) arranged between the motor (120) and the second chamber (B), the further seal being configured to substantially prevent fluid from flowing from the second chamber to the motor.

12. The electric cylinder (100) according to any one of the preceding claims, further comprising a first connecting device (111) and a second connecting device (112) respectively arranged at the proximal end and the distal end of the electric cylinder, so that the electric cylinder can be pivotally connected to any one of a vehicle frame, a suspension strut and a steering knuckle.

13. The electric cylinder (100) according to any one of the preceding claims, further comprising a suspension strut support (114) arranged at a distal end of the housing, the suspension strut support being configured to support a suspension strut.

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