Hydraulic system of an active suspension of a motor vehicle and motor vehicle

Abstract

Hydraulic system (1) of an active suspension of a motor vehicle (100) with a number of hydraulic actuators (2a, 2b, 2c, 2d, 8a, 8b), wherein the hydraulic system (1) comprises a plurality of hydraulic lines, a hydraulic accumulator (10) and an electro-hydraulic motor pump unit (3), by means of which a hydraulic fluid, in particular a hydraulic oil, can be conveyed through the hydraulic lines during the operation of the hydraulic system (1), as well as valve means which are assigned to the hydraulic actuators (2a, 2b, 2c, 2d, 8a, 8b), wherein the hydraulic system (1) is configured to electronically control a selective filling of the hydraulic actuators (2a, 2b, 2c, 2d, 8a, 8b) with the hydraulic fluid, and wherein the hydraulic system (1) has a cooling device (12) with a cooling element (13) which is attached to the hydraulic accumulator (10) is attached, characterized in that the hydraulic accumulator (10) has a connection section (15),on which a cooler extension (14) of the cooling device (12) is attached.

Description

[0001] The present invention relates to a hydraulic system of an active suspension of a motor vehicle with a number of hydraulic actuators, wherein the hydraulic system comprises a plurality of hydraulic lines, a hydraulic accumulator and an electro-hydraulic motor pump unit, by means of which a hydraulic fluid, in particular a hydraulic oil, can be conveyed through the hydraulic lines during the operation of the hydraulic system, as well as valve means that are assigned to the hydraulic actuators, wherein the hydraulic system is configured to electronically control a selective filling of the hydraulic actuators with the hydraulic fluid, and wherein the hydraulic system has a cooling device with a cooling element that is attached to the hydraulic accumulator.Furthermore, the present invention relates to a motor vehicle with a body and an active chassis, comprising a number of hydraulic actuators and a hydraulic system for operating the hydraulic actuators.

[0002] Motor vehicles with an active suspension system are known in various embodiments from the prior art. With the aid of an active suspension system, it is possible to actively intervene in the suspension and damping of the motor vehicle in order to reduce, in particular, roll, pitch, and roll movements of the vehicle body.

[0003] An active chassis of a motor vehicle can, for example, have an active roll stabilization device, which serves the purpose of reducing, especially when cornering, corresponding roll movements of a vehicle body of the motor vehicle - i.e. rotational movements around a longitudinal axis of a vehicle-fixed coordinate system.

[0004] A known embodiment of an active roll stabilization system features a hydraulic actuator with an actively adjustable hydraulic cylinder at each of the vehicle's wheel suspensions. These hydraulic actuators replace the rigid connecting rods typically used to attach the stabilizers. The lower part of the hydraulic cylinders is connected to the outer mounting points of the stabilizers, and the upper part is connected to the respective wheel carrier. Electronically controlled filling of the hydraulic cylinders with a hydraulic fluid, particularly hydraulic oil, changes the stroke of the hydraulic cylinders, thus pre-tensioning the respective stabilizer to a greater or lesser degree. The hydraulic cylinders of the hydraulic actuators are individually controlled depending on the driving situation, thereby influencing the vehicle's self-steering behavior and consequently improving vehicle stabilization.

[0005] An active suspension system can, for example, also have a hydraulic level control device, in order to vary the ground clearance of the vehicle or to keep the vehicle level constant under different load conditions.

[0006] As an alternative to a hydraulic leveling system that acts on the front and rear wheel suspensions of the vehicle, an active suspension can also include a hydraulic front axle lift system. This system comprises two hydraulic actuators, each with a hydraulic lifting cylinder. The front axle lift system allows the front of the vehicle to be selectively raised, thereby increasing the vehicle's approach and departure angles. This raising of the front end is particularly advantageous when driving up steep underground parking garage entrances or over speed bumps, preventing the front of the vehicle from bottoming out.

[0007] The problem with the hydraulic system is that at least some components are exposed to relatively high thermal loads. In particular, the electro-hydraulic motor pump unit and a valve block of the rear axle, which includes a number of valve elements, are typically subjected to the highest thermal stresses. A further problem is that there is often insufficient installation space within the vehicle to actively cool the thermally stressed components of the hydraulic system using a conventional cooling system.

[0008] From EP 2 196 337 A1, a hydraulic accumulator is known which is arranged downstream of a damping valve of a vehicle damping system. The hydraulic accumulator comprises a storage chamber and a pressure chamber filled with a pressurized gas, arranged adjacent to it. A cooling element is arranged in the pressure chamber.

[0009] A generic hydraulic system for an active suspension of a motor vehicle with a number of hydraulic actuators is known from WO 2021 / 260 586 A1. Because this hydraulic system has a cooling device with a cooling element attached to the hydraulic accumulator, it is possible to cool the hydraulic fluid within the accumulator, thus achieving improved cooling of thermally stressed components of the hydraulic system.

[0010] Another hydraulic system is revealed in US 2020 / 0 347 905 A1.

[0011] The present invention aims to further develop a hydraulic system for an active chassis of a motor vehicle of the type mentioned above, as well as a generic motor vehicle with an active chassis, in such a way that further improved cooling of thermally stressed components of the hydraulic system can be achieved.

[0012] The solution to this problem is provided by a hydraulic system of the type mentioned above, having the features of the characterizing part of claim 1. With regard to the motor vehicle, this problem is solved by a motor vehicle of the generic type, having the features of the characterizing part of claim 6. The dependent claims relate to advantageous embodiments of the invention.

[0013] A hydraulic system according to the invention is characterized in that the hydraulic accumulator has a connection section to which a cooler extension of the cooling device is attached. This results in further improved cooling of the hydraulic fluid and thus also of the thermally stressed components of the hydraulic system.

[0014] In a preferred embodiment, it is proposed that the heat sink has a plurality of cooling fins on its outer surface. These cooling fins advantageously increase the cooling surface area of ​​the heat sink, thereby further improving heat dissipation.

[0015] In a particularly preferred embodiment, the heat sink can be directly connected to the vehicle body, in particular by bolting. This results in a further significant increase in the available cooling surface area of ​​the heat sink, thus enabling even more efficient heat dissipation in a simple manner.

[0016] In a particularly advantageous embodiment, it is proposed that the cooler extension be designed to be permeated and / or surrounded by the hydraulic fluid during operation of the hydraulic system. This further improves the cooling of the hydraulic fluid.

[0017] To avoid cooling the hydraulic fluid solely by diffusion, a further advantageous embodiment of the cooling device provides for additional cooling means. This results in faster cooling of the hydraulic fluid.

[0018] A motor vehicle according to the invention is characterized in that the hydraulic system is designed according to one of claims 1 to 5.

[0019] In one embodiment, it is proposed that the hydraulic system and at least some of the hydraulic actuators are parts of an active roll stabilization device of the motor vehicle.

[0020] In one embodiment, the hydraulic system and at least some of the hydraulic actuators are components of a front axle lift device for the vehicle. This front axle lift device allows the front of the vehicle to be raised as needed, thereby increasing the vehicle's approach angle. Raising the front of the vehicle is particularly advantageous when driving over steep underground parking garage entrances or speed bumps, preventing the front of the vehicle from bottoming out.

[0021] In another embodiment, it is possible that the hydraulic system and at least some of the hydraulic actuators are parts of a level control device of the motor vehicle.

[0022] If the motor vehicle is equipped with a hydraulically operated roll stabilization device and additionally with a hydraulic level control device or a hydraulic front axle lift device, it is advantageous, not least for packaging reasons, to use a common hydraulic system for their operation.

[0023] Further features and advantages of the present invention will become clear from the following description of a preferred embodiment with reference to the accompanying figures. Fig. 1 A perspective view showing the main components of an active chassis of a motor vehicle equipped with an active roll stabilization device and a front axle lift device, Fig. 2 A detailed view of a hydraulic accumulator of a hydraulic system of the active chassis.

[0024] With reference to Fig. Figure 1 shows a motor vehicle 100, which has an active suspension system equipped with a hydraulic roll stabilization device and a hydraulic front axle lift device. The motor vehicle has a hydraulic system 1 by means of which the hydraulic roll stabilization device and the hydraulic front axle lift device can be operated. The active suspension system of the motor vehicle has, in a known manner, a first (front) stabilizer 102 and a second (rear) stabilizer 103. Such stabilizers 102, 103 serve the purpose of reducing the roll angle that occurs when cornering.

[0025] The hydraulic roll stabilization system is designed to reduce roll movements of the vehicle body of the motor vehicle 100, particularly during cornering – i.e., rotational movements about a longitudinal axis of a vehicle-fixed coordinate system. The hydraulic roll stabilization system has a hydraulic actuator 2a, 2b, 2c, 2d with an actively adjustable hydraulic cylinder at each of the four wheel suspensions of the motor vehicle 100. These hydraulic actuators 2a, 2b, 2c, 2d form a first actuator group and replace the rigid connecting rods typically used to attach the stabilizers 102, 103. The lower part of the hydraulic cylinders of the hydraulic actuators 2a, 2b, 2c, 2d is connected to the outer mounting points of the stabilizers 102, 103, and the upper part is connected to the respective wheel carrier.By electronically controlling the filling of the hydraulic cylinders with a hydraulic fluid, in particular hydraulic oil, the stroke of the hydraulic cylinders changes and the respective stabilizer 102, 103 is pre-tensioned to a greater or lesser degree. The hydraulic cylinders of the hydraulic actuators 2a, 2b, 2c, 2d are individually controlled depending on the driving situation, thereby influencing the self-steering behavior and consequently improving vehicle stabilization.

[0026] For the operation of the hydraulic roll stabilization device, the motor vehicle 100 has the hydraulic system 1, which comprises a plurality of hydraulic lines (not provided with reference numerals) and an electro-hydraulic motor pump unit 3, by means of which a hydraulic fluid, in particular a hydraulic oil, can be conveyed through the hydraulic lines and made available to the hydraulic actuators 2a, 2b, 2c, 2d during the operation of the hydraulic system 1.

[0027] The hydraulic system 1 comprises a first hydraulic circuit 4 with hydraulic lines and a first valve block 5 with switchable valve elements, which are assigned to the two hydraulic actuators 2a, 2b of the front axle of the motor vehicle 100. Furthermore, the hydraulic system 1 comprises a second hydraulic circuit 6 with hydraulic lines and a second valve block 7 with switchable valve elements, which are assigned to the hydraulic actuators 2c, 2d of the rear axle of the motor vehicle 100. The active roll stabilization of the front and rear axles of the motor vehicle 100 can advantageously be controlled independently of each other due to the two separate hydraulic circuits 4, 6 and the associated valve blocks 5, 7. The selective filling of the hydraulic actuators 2a, 2b, 2c, 2d of the first actuator group with hydraulic fluid is electronically controlled during the operation of the hydraulic system 1.

[0028] Furthermore, the active suspension of the motor vehicle 100 in this embodiment includes a hydraulic front axle lift device with a second actuator group comprising two hydraulic actuators 8a, 8b. The hydraulic front axle lift device allows the front section of the motor vehicle 100 to be raised as needed, particularly to increase the approach angle. Each of the two hydraulic actuators 8a, 8b has a hydraulic lifting cylinder integrated into one of the two struts of the front axle of the motor vehicle 100. The two actuators 8a, 8b of the hydraulic front axle lift device are connected to the electro-hydraulic motor pump unit 3 by means of a lift hydraulic line 9.Thus, the hydraulic roll stabilization device and the hydraulic front axle lift device share the hydraulic system 1 of the active suspension, so that it is advantageously not necessary to provide a separate hydraulic system for each of these two devices. The supply of hydraulic fluid to the two hydraulic actuators 8a, 8b of the hydraulic front axle lift device, in order to supply their hydraulic cylinders with hydraulic fluid via the lift hydraulic line 9 and thus raise the front of the vehicle 100, is also electronically controlled.

[0029] The hydraulic system 1 further includes a switchable valve means by which it is possible to switch between the roll stabilization function of the hydraulic roll stabilization device on the one hand and the lift function of the hydraulic front axle lift device on the other hand, so that at the same time only one of the two functions of the active chassis is activated.

[0030] The hydraulic system 1 further comprises a hydraulic accumulator 10, which is preferably designed as a piston accumulator and which, in this embodiment, is connected to the second valve block 7 by means of a hydraulic line 11. The hydraulic accumulator 10 is designed to generate a preload within the hydraulic system 1, in particular a preload on the order of approximately 10 bar. The hydraulic accumulator 10 serves primarily to supply the front axle lift actuators 8a, 8b in order to create a volume balance.

[0031] The hydraulic system 1 described above, intended for operating the active roll stabilization device and the hydraulic front axle lift device, presents thermal challenges. In particular, the electro-hydraulic motor pump unit 3 and the second valve block 7, which is assigned to the rear axle of the vehicle 100, are subjected to very high thermal loads during operation of the hydraulic system 1. This problem is further exacerbated by the lack of space for conventional cooling systems, which would, for example, enable active cooling of the thermally stressed components of the hydraulic system 1.

[0032] To remedy the problem outlined above, it is now proposed that the hydraulic system 1 have a cooling device 12 with a cooling element 13, the cooling element 13 being attached to the hydraulic accumulator 10. This advantageously makes it possible to cool the hydraulic fluid within the hydraulic accumulator 10, thus easily achieving improved cooling of thermally stressed components of the hydraulic system 1.

[0033] This hydraulic accumulator 10 with the attached cooling element 13 is described in detail in Fig. 2 shown. Fig. Figure 1 does not show this heat sink 13. The heat sink 13 has a plurality of cooling fins 130 on its outer surface, which increase the cooling surface area of ​​the heat sink 13 in order to improve heat dissipation.

[0034] The heat sink 13 is preferably directly connected to the body 101 of the motor vehicle 100, in particular by being screwed to it. This results in a further, significant increase in the cooling surface area of ​​the heat sink 13, so that further improved heat dissipation can be achieved.

[0035] The cooling device 12 further comprises a cooler extension 14, which is attached to a connection section 15 of the hydraulic accumulator 10 and enables further improved heat dissipation. In a further embodiment not explicitly shown here, the cooler extension 14 is designed to be flowed through and / or around by the hydraulic fluid during operation. This makes it possible to make the cooling of the hydraulic fluid even more effective and efficient.

[0036] To ensure that cooling is not solely achieved through diffusion (heat conduction), the cooling device 12 can be augmented with additional means for cooling the hydraulic fluid. This results in faster cooling of the hydraulic fluid.

Claims

[1] Hydraulic system (1) of an active suspension of a motor vehicle (100) with a number of hydraulic actuators (2a, 2b, 2c, 2d, 8a, 8b), wherein the hydraulic system (1) comprises a plurality of hydraulic lines, a hydraulic accumulator (10) and an electro-hydraulic motor pump unit (3), by means of which a hydraulic fluid, in particular a hydraulic oil, can be conveyed through the hydraulic lines during the operation of the hydraulic system (1), as well as valve means which are assigned to the hydraulic actuators (2a, 2b, 2c, 2d, 8a, 8b), wherein the hydraulic system (1) is configured to electronically control a selective filling of the hydraulic actuators (2a, 2b, 2c, 2d, 8a, 8b) with the hydraulic fluid, and wherein the hydraulic system (1) has a cooling device (12) with a cooling element (13) which is attached to the hydraulic accumulator (10) is attached, characterized by, that the hydraulic accumulator (10) has a connection section (15) to which a cooler extension (14) of the cooling device (12) is attached. [2] Hydraulic system (1) according to claim 1, characterized by , that the heat sink (13) has a plurality of cooling fins (130) on its outside. [3] Hydraulic system (1) according to one of claims 1 or 2, characterized by , that the cooling element (13) is directly connected to a body (101) of the motor vehicle (100), in particular by screwing it on. [4] Hydraulic system (1) according to any one of claims 1 to 3, characterized by , that the cooler extension (14) is designed to be flowed through and / or around by the hydraulic fluid during the operation of the hydraulic system (1). [5] Hydraulic system (1) according to any one of claims 1 to 4, characterized by , that the cooling device (12) has further means for cooling the hydraulic fluid. [6] Motor vehicle (100) with a body (101) and an active suspension comprising a number of hydraulic actuators (2a, 2b, 2c, 2d, 8a, 8b) and a hydraulic system (1) for operating the hydraulic actuators (2a, 2b, 2c, 2d, 8a, 8b), characterized by , that the hydraulic system (1) is designed according to one of claims 1 to 5. [7] Motor vehicle (100) according to claim 6, characterized by , that the hydraulic system (1) and at least some of the hydraulic actuators (2a, 2b, 2c, 2d, 8a, 8b) are parts of an active roll stabilization device of the motor vehicle (100). [8] Motor vehicle (100) according to one of claims 6 or 7, characterized by , that the hydraulic system (1) and at least some of the hydraulic actuators (2a, 2b, 2c, 2d, 8a, 8b) are parts of a front axle lifting device of the motor vehicle (100). [9] Motor vehicle (100) according to one of claims 6 or 7, characterized by, that the hydraulic system (1) and at least some of the hydraulic actuators (2a, 2b, 2c, 2d, 8a, 8b) are parts of a level control device of the motor vehicle (100).

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