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

Abstract

The invention relates to a 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 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.

Description

[0001] The present invention relates to a hydraulic system of an active chassis of a motor vehicle having 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 operation of the hydraulic system, as well as valve means associated with the hydraulic actuators, and wherein the hydraulic system is designed to electronically control a selective filling of the hydraulic actuators with the hydraulic fluid. Furthermore, the present invention relates to a motor vehicle having a body and an active chassis, which comprises a number of hydraulic actuators and a hydraulic system for operating the hydraulic actuators.

[0002] Motor vehicles with active chassis are known in various designs from the prior art. With the help of an active chassis, it is possible to actively intervene in the vehicle's suspension and damping, thereby reducing, in particular, rolling, heaving, and pitching 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 corresponding rolling movements of a vehicle body of the motor vehicle - i.e. rotational movements about a longitudinal axis of a vehicle-fixed coordinate system - particularly when cornering.

[0004] A prior art variant of an active roll stabilization system has a hydraulic actuator with an actively adjustable hydraulic cylinder on each of the vehicle's wheel suspensions. These hydraulic actuators replace the rigid coupling rods typically used to connect the stabilizers. The lower part of the hydraulic cylinder is connected to the outer screw points of the stabilizers, and the upper part is connected to the respective wheel carrier. By electronically filling the hydraulic cylinders with a hydraulic fluid, in particular hydraulic oil, the stroke of the hydraulic cylinders changes, and the respective stabilizer is preloaded to a greater or lesser extent. The hydraulic cylinders of the hydraulic actuators are controlled individually depending on the driving situation, which particularly influences the self-steering behavior and consequently improves vehicle stability.

[0005] An active chassis can, for example, also have a hydraulic level control device, in particular to vary the ground clearance of the motor vehicle or to keep the vehicle level constant under different loading conditions.

[0006] As an alternative to a hydraulic leveling system that acts on the wheel suspensions of the front and rear wheels of the vehicle, an active chassis can also feature a hydraulic front axle lift system, which has two hydraulic actuators, each containing a hydraulic lifting cylinder. Using the front axle lift system, it is possible to raise the front of the vehicle in a targeted manner, thus increasing the vehicle's approach and departure angle. This raising of the front of the vehicle is particularly advantageous on steep underground parking garage entrances or when driving over speed bumps on the road, preventing the front of the vehicle from accidentally touching the ground.

[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 on the rear axle, which includes several valve elements, are typically subject to the highest thermal loads. A further problem is that there is often insufficient space within the vehicle to actively cool components of the hydraulic system that are subject to particularly high thermal loads using a conventional cooling system.

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

[0009] The present invention has for its object to further develop a hydraulic system for an active chassis of a motor vehicle of the type mentioned at the outset and a generic motor vehicle with an active chassis in such a way that improved cooling of thermally stressed components of the hydraulic system can be achieved.

[0010] This object is achieved 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 object is achieved by a generic motor vehicle having the features of the characterizing part of claim 7. The subclaims relate to advantageous developments of the invention.

[0011] A hydraulic system according to the invention is characterized in that the hydraulic system comprises a cooling device with a heat sink attached to the hydraulic accumulator. This inventive measure advantageously makes it possible to cool the hydraulic fluid within the hydraulic accumulator, thus resulting in improved cooling of thermally stressed components of the hydraulic system.

[0012] In a preferred embodiment, it is proposed that the heat sink have a plurality of cooling fins on its exterior. These cooling fins advantageously increase the cooling surface of the heat sink, thereby further improving heat dissipation.

[0013] In a particularly preferred embodiment, it is possible for the heat sink to be directly connected, in particular screwed, to a body of the motor vehicle. This results in a further significant increase in the available cooling surface of the heat sink, so that even more efficient heat dissipation can be achieved in a simple manner.

[0014] In an advantageous embodiment, the hydraulic accumulator can be provided with a connecting 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.

[0015] In a particularly advantageous embodiment, it is proposed that the cooler extension be designed to allow the hydraulic fluid to flow through and / or around it during operation of the hydraulic system. This allows the cooling of the hydraulic fluid to be further improved.

[0016] To ensure that the hydraulic fluid is not cooled solely by diffusion, an advantageous refinement provides the possibility for the cooling device to have additional means for cooling the hydraulic fluid. This results in faster cooling of the hydraulic fluid.

[0017] A motor vehicle according to the invention is characterized in that the hydraulic system is designed according to one of claims 1 to 6.

[0018] 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.

[0019] In one embodiment, it is possible for the hydraulic system and at least some of the hydraulic actuators to be part of a front axle lift device of the motor vehicle. Using the front axle lift device, it is possible to raise the front end of the vehicle as needed, thus increasing the vehicle's approach and departure angle. This raising of the front end is particularly advantageous on steep underground parking garage entrances or when driving over speed bumps on the roadway, preventing the front end of the vehicle from accidentally touching the ground.

[0020] In a further 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.

[0021] 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.

[0022] Further features and advantages of the present invention will become clear from the following description of a preferred embodiment with reference to the accompanying drawings. Fig. 1 is 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 lifting device, Fig. 2 a detailed view of a hydraulic accumulator of a hydraulic system of the active chassis.

[0023] With reference to Fig. 1 shows a motor vehicle 100 having an active chassis, which in this case is 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 chassis 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.

[0024] The hydraulic roll stabilization device is intended to reduce corresponding roll movements of a vehicle body of the motor vehicle 100—i.e., rotational movements about a longitudinal axis of a vehicle-fixed coordinate system—particularly during cornering. The hydraulic roll stabilization device has a hydraulic actuator 2a, 2b, 2c, 2d with an actively adjustable hydraulic cylinder on 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 coupling rods typically used to connect the stabilizers 102, 103. The lower part of the hydraulic cylinders of the hydraulic actuators 2a, 2b, 2c, 2d is connected to the outer screwing points of the stabilizers 102, 103, and the upper part is connected to the respective wheel carrier.By electronically filling 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 preloaded to a greater or lesser extent. The hydraulic cylinders of the hydraulic actuators 2a, 2b, 2c, 2d are controlled individually depending on the driving situation, thereby influencing the self-steering behavior and consequently improving vehicle stability.

[0025] 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 operation of the hydraulic system 1.

[0026] The hydraulic system 1 has a first hydraulic circuit 4 with hydraulic lines and a first valve block 5 with switchable valve means, which are assigned to the two hydraulic actuators 2a, 2b of the front axle of the motor vehicle 100. Furthermore, the hydraulic system 1 has a second hydraulic circuit 6 with hydraulic lines and a second valve block 7 with switchable valve means, 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 axle and the rear axle of the motor vehicle 100 can advantageously be controlled separately from one another 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 the hydraulic fluid is electronically controlled during operation of the hydraulic system 1.

[0027] Furthermore, the active chassis of the motor vehicle 100 in this exemplary embodiment comprises a hydraulic front axle lift device with a second actuator group comprising two hydraulic actuators 8a, 8b. Using the hydraulic front axle lift device, a front end of the motor vehicle 100 can be raised as needed, in particular to increase the approach angle. Each of the two hydraulic actuators 8a, 8b has a hydraulic lifting cylinder integrated into one of the two spring 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 electrohydraulic motor pump unit 3 via a lift hydraulic line 9.Thus, the hydraulic roll stabilization device and the hydraulic front axle lift device share the active chassis' hydraulic system 1, advantageously eliminating the need 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, which is used to supply hydraulic fluid to their hydraulic cylinders via the lift hydraulic line 9 and thus raise the front end of the motor vehicle 100, is also electronically controlled.

[0028] The hydraulic system 1 further comprises a switchable valve means by means of which switching can be made 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 only one of the two functions of the active chassis is activated at the same time.

[0029] The hydraulic system 1 further comprises a hydraulic accumulator 10, which is preferably designed as a piston accumulator and, in this exemplary embodiment, is connected to the second valve block 7 via a hydraulic line 11. The hydraulic accumulator 10 is designed to generate a preload within the hydraulic system 1, in particular a preload of approximately 10 bar. The hydraulic accumulator 10 primarily serves to supply the front axle lift actuators 8a, 8b to create volume compensation.

[0030] The hydraulic system 1 described above, intended for the operation of the active roll stabilization system and the hydraulic front axle lift system, is problematic from a thermal perspective. In particular, the electro-hydraulic motor pump unit 3 and the second valve block 7, which is assigned to the rear axle of the motor vehicle 100, are exposed to very high thermal loads during operation of the hydraulic system 1. This problem is further exacerbated by the fact that no installation space is available for conventional cooling systems, for example, to enable active cooling of the thermally stressed components of the hydraulic system 1.

[0031] To remedy the problem outlined above, it is now proposed that the hydraulic system 1 comprise a cooling device 12 with a heat sink 13, wherein the heat sink 13 is attached to the hydraulic accumulator 10. This advantageously makes it possible to cool the hydraulic fluid within the hydraulic accumulator 10, so that improved cooling of thermally stressed components of the hydraulic system 1 can also be achieved in a simple manner.

[0032] This hydraulic accumulator 10 with the attached cooling body 13 is shown in detail in Fig. 2. In Fig. This heat sink 13 is not shown in Figure 1. 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, thereby improving heat dissipation.

[0033] The heat sink 13 is preferably directly connected to the body 101 of the motor vehicle 100, in particular screwed thereto. This results in a further, significant increase in the cooling surface of the heat sink 13, so that further improved heat dissipation can be achieved.

[0034] In this exemplary embodiment, 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 development not explicitly shown here, it is possible for the cooler extension 14 to be designed so that the hydraulic fluid flows through and / or around it during operation. This makes it possible to make the cooling of the hydraulic fluid even more effective and efficient.

[0035] To ensure that cooling is not achieved solely by diffusion (heat conduction), the cooling device 12 can be expanded with additional means for cooling the hydraulic fluid. This results in faster cooling of the hydraulic fluid. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 2 196 337 A1

[0008]

Claims

[1] Hydraulic system (1) of an active chassis 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 operation of the hydraulic system (1), as well as valve means associated with the hydraulic actuators (2a, 2b, 2c, 2d, 8a, 8b), and wherein the hydraulic system (1) is designed to electronically control a selective filling of the hydraulic actuators (2a, 2b, 2c, 2d, 8a, 8b) with the hydraulic fluid, characterized by that the hydraulic system (1) has a cooling device (12) with a heat sink (13) which is attached to the hydraulic accumulator (10). [2] Hydraulic system (1) according to claim 1, characterized bythat the heat sink (13) has a plurality of cooling fins (130) on its outer side. [3] Hydraulic system (1) according to one of claims 1 or 2, characterized by that the heat sink (13) is directly connected, in particular screwed, to a body (101) of the motor vehicle (100). [4] Hydraulic system (1) according to one of claims 1 to 3, 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. [5] Hydraulic system (1) according to claim 4, characterized by that the cooler extension (14) is designed to be flowed through and / or around by the hydraulic fluid during operation of the hydraulic system (1). [6] Hydraulic system (1) according to one of claims 1 to 5, characterized by that the cooling device (12) has further means for cooling the hydraulic fluid. [7] Motor vehicle (100) with a body (101) and an active chassis 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 6. [8] Motor vehicle (100) according to claim 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 an active roll stabilization device of the motor vehicle (100). [9] Motor vehicle (100) according to one of claims 7 or 8, 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). [10] Motor vehicle (100) according to one of claims 7 or 8, characterized bythat 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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