Hydraulic section for hydraulic actuation in a motor vehicle and use of a hydraulic system

Abstract

A hydraulic system (22, 24, 26, 28) for hydraulic actuation in a motor vehicle is provided, comprising a pressure source (12) for generating hydraulic pressure, a pressure consumer (14) for applying hydraulic force, and a pressure line (16) for hydraulically connecting the pressure source (12) to the pressure consumer (14), wherein the pressure consumer (14) has components with a lower temperature stress limit than the pressure source (12) and the pressure line (16), and wherein a hydraulic consumer volume of the pressure consumer (14) is less than a line volume (V). L , V S1 , V S2 , V S3 , V S4 ) of the pressure line (16) between the pressure source (12) and the pressure consumer (14). Due to the thermal buffering effect of the large line volume (V) L , V S1 , V S2 , V S3 , V S4) the hydraulic medium heated by the pressure source (12) cannot reach the pressure consumer (14), thus ensuring good protection of hydraulic pressure consumers (14) in a motor vehicle against thermal damage.

Description

[0001] The invention relates to a hydraulic system with which hydraulic actuation can be carried out in a motor vehicle, and to the use of a hydraulic system with such a hydraulic system in a motor vehicle.

[0002] From EP 2 186 662 A1 a hydraulic system for a motor vehicle is known in which several wheel suspensions can be hydraulically actuated from a common pressure source, wherein in the event that a hydraulic medium in one of the wheel suspensions is too hot, the hydraulic medium is exchanged and mixed with the hydraulic medium in a less hot wheel suspension.

[0003] There is a constant need to prevent thermal damage to hydraulic pressure consumers in a motor vehicle.

[0004] The object of the invention is to demonstrate measures that enable good protection of hydraulic pressure consumers in a motor vehicle against thermal damage.

[0005] The problem is solved according to the invention by a hydraulic system with the features of claim 1, a hydraulic system with the features of claim 8, and a use with the features of claim 10. Preferred embodiments of the invention are specified in the dependent claims and the following description, each of which can individually or in combination represent an aspect of the invention.

[0006] One aspect of the invention relates to a hydraulic system for hydraulic actuation in a motor vehicle, comprising a pressure source for generating hydraulic pressure, a pressure consumer for applying hydraulic force, and a pressure line for hydraulically connecting the pressure source to the pressure consumer, wherein the pressure consumer has components with a lower temperature stress limit than the pressure source and the pressure line, and wherein a hydraulic consumer volume of the pressure consumer is less than a line volume of the pressure line between the pressure source and the pressure consumer.

[0007] It was recognized that the hydraulic fluid heated during pressure build-up in the pressure source can cause thermal stress on the pressure consumer. To thermally protect the pressure consumer, it is ensured that the hydraulic fluid heated in the pressure source cannot reach the pressure consumer at all. This is achieved by ensuring that the pressure line volume is large enough that only the hydraulic fluid present in the pressure line before the pressure source is activated can reach the pressure consumer. The hydraulic fluid in the pressure line before the pressure source is activated has a significantly lower temperature compared to the hydraulic fluid delivered by the pressure source, since the energy input generated by the pressure source during pressure build-up is transferred only to the hydraulic fluid passing through the pressure source.The cold fluid previously present in the pressure line can thus form a thermal buffer, which, due to its volume, prevents contact between the hot hydraulic fluid pumped from the pressure source and the components of the pressure consumer. Thanks to the thermal buffering effect of the large line volume, the hydraulic fluid heated by the pressure source cannot reach the pressure consumer, thus ensuring a high level of protection against thermal damage to hydraulic pressure consumers in a motor vehicle.

[0008] The pressure source can be designed as a hydraulic pump that pressurizes the hydraulic medium supplied from a reservoir and increases the hydraulic pressure at the pump's outlet. The pressure line can connect directly to the pressure source's outlet and receive the pressurized hydraulic medium. The pressure source is specifically designed for higher temperatures, for example, above 90°C or above 100°C.

[0009] The hydraulic medium is, in particular, a hydraulic oil, for example HLP according to DIN 51 524 Part 2. The hydraulic medium is, in particular, air- and water-separating and suitable, for example, for pressures up to 200 bar or up to 350 bar. Preferably, the hydraulic medium has a lower thermal conductivity than water and / or HLP.

[0010] The pressure line is designed for the pressures and temperatures occurring at the outlet of the pressure source. In particular, the pressure line has a temperature limit of over 90°C, especially over 100°C. Furthermore, the pressure line can be designed for a hydraulic pressure of up to 200 bar or up to 350 bar. The pressure line can be constructed as a reinforced hydraulic hose or a metal pipe.

[0011] The pressure consumer can be designed for hydraulic actuation, for example, by having the hydraulic pressure arriving at the pressure consumer press against a pressure plate of an actuator that is relatively movable within the pressure consumer. A valve leg of the actuator can be connected to a hydraulically movable vehicle component. In particular, the pressure consumer is intended for adjusting the height of a wheel of the vehicle relative to the vehicle body.

[0012] The components of the pressure consumer may, at least in part, have a relatively low temperature tolerance. In particular, seals within the pressure consumer, which are intended to seal moving parts relative to each other, have a low temperature tolerance and could be permanently damaged at temperatures above this limit. This can occur, for example, at temperatures below 100°C or even below 90°C.

[0013] The temperature stress limit represents a maximum possible temperature at which permanent thermal damage to the component is not to be expected.

[0014] In particular, the pressure line is made of a rigid pipe material, while the pressure consumer has a hose made of an elastic and / or flexible hose material and connected to the pressure line. The hose material has a lower temperature stress limit than the pipe material. The pipe material, for example, steel, can withstand high pressures and high temperatures and is therefore well suited as a pressure line. The pressure consumer may need to move relative to the hydraulically actuated vehicle component and can therefore be connected to the pressure line via the hose, allowing relative movement between the two ends of the hose due to its flexible and / or elastic nature.For sufficient flexibility and / or elasticity, the hose material typically contains plasticizers, which can lose their plasticizing effect at higher temperatures. This can cause the hose material to become brittle and damaged during movement. However, since the large hose volume prevents excessively high temperatures, thermal damage is not a concern. In fact, the large hose volume makes it possible to use a hose within the pressure consumer and / or to mount the pressure consumer in conjunction with the vehicle component being adjusted. This increases the degree of design freedom in hydraulically actuated vehicle components.

[0015] Preferably, the pressure consumer has a relatively movable actuator, which is sealed within the pressure consumer by means of a seal. This seal has a lower temperature limit than the pressure line and the pressure source. In particular, the seal sealing the relatively movable actuator is generally designed to be comparatively soft and not very temperature-resistant. However, since the large volume of the line prevents excessively high temperatures at the seal, the seal can be selected and dimensioned based on its sealing properties rather than its temperature resistance. This allows for improved sealing performance in the pressure consumer at lower manufacturing costs. Simultaneously, a long service life for the pressure consumer can be achieved.

[0016] Particularly preferred is a pressure source configured to actuate a pressure consumer and heat a hydraulic medium to a temperature above 90°C, especially above 100°C, wherein the pressure consumer comprises components with a maximum temperature load limit of below 90°C, especially below 85°C, preferably below 80°C. The pressure source can be designed for a comparatively high temperature and high pressures, while, due to the thermal buffering effect of the large pipe volume, the pressure consumer only needs to be designed for significantly lower temperatures. This can reduce manufacturing costs.

[0017] In particular, the pressure line has a longer extension compared to a direct linear connection between the pressure consumer and the pressure source. The large volume of the pressure line intended for thermal buffering can be achieved through an extended route, for example, an angular, zigzag, and / or looped path. This avoids an increase in the flow cross-section within the pressure line. In fact, it is even advantageous, rather than disadvantageous, if the pressure line has a more complex route that bypasses various internal components, as this actually improves the buffering effect of the line volume.

[0018] Preferably, the pressure line has a longer length compared to a straight line between the pressure consumer and the pressure source. The large volume of the pressure line intended for thermal buffering can be achieved by an extended route, for example, a zigzag and / or loop-shaped one. This avoids an increase in the flow cross-section in the pressure line. In fact, it is even advantageous, rather than disadvantageous, if the pressure line has a more complex route that bypasses various internal components, as this actually improves the buffering effect of the line volume.

[0019] It is particularly advantageous for the pipe volume to be chosen to be so large relative to the consumer volume that, in the fully actuated end position of the pressure consumer, a buffer volume remains between the pressure consumer and the volume of medium in the pressure line that has previously passed through the pressure source. This buffer volume compensates for heat conduction effects with medium that has not previously passed through the pressure source. Even in the fully actuated end position of the pressure consumer, the pipe volume is not completely filled with the hot hydraulic medium from the pressure source. Instead, the cold hydraulic medium that has not passed through the pressure source remains in a section of the pipe ending at the pressure consumer. The buffer volume is, for example, 1% to 15%, and more specifically, 2% to 10% of the total pipe volume.The hot hydraulic medium can heat the cold hydraulic medium in the buffer volume through heat conduction. However, the buffer volume can be chosen to be large enough that, even taking into account heat conduction effects along the length of the pressure line, the temperature in the pressure consumer cannot exceed the temperature load limit. As a result, the hydraulic medium in the pressure consumer has a temperature that can safely remain below the temperature load limit.

[0020] A further aspect of the invention relates to a hydraulic system for several parallel hydraulic actuators in a motor vehicle, comprising a first hydraulic circuit, which can be designed and further developed as described above, and a second hydraulic circuit, which can be designed and further developed, in particular, as described above, wherein preferably the first hydraulic circuit and the second hydraulic circuit share the same pressure source, and in particular, the first hydraulic circuit and the second hydraulic circuit share at least a portion of the identical pressure line. Sharing common components reduces the number of components and manufacturing costs. Due to the thermal buffering effect of the large line volume, hydraulic fluid heated by the pressure source cannot reach the pressure consumers, thus ensuring good protection of hydraulic pressure consumers in a motor vehicle against thermal damage.

[0021] In particular, a third hydraulic line, which may be configured and further developed as described above, and a fourth hydraulic line, which may be configured and further developed as described above, are provided, wherein either the first and second hydraulic lines or the third and fourth hydraulic lines share at least a portion of the identical pressure line. The pressure source can act on two hydraulic lines leading, for example, to rear wheels or front wheels, particularly in the area of ​​the associated wheel axle, wherein the hydraulic lines spaced apart from the pressure source are connected to the pressure source via a common portion of the pressure line. The common portion of the pressure line can, in particular, bridge an offset between a front wheel axle and a rear wheel axle.

[0022] Another aspect of the invention relates to the use of a hydraulic system, which can be designed and further developed as described above, for roll stabilization of the motor vehicle and / or for height adjustment of the motor vehicle. Due to the thermal buffering effect of the large line volume, hydraulic medium heated by the pressure source cannot reach the pressure consumer, thus ensuring good protection of hydraulic pressure consumers in a motor vehicle against thermal damage during roll stabilization and / or height adjustment of the motor vehicle.

[0023] The invention is now explained by way of example with reference to the accompanying drawing, using a preferred embodiment as an illustration, wherein the features shown below can represent an aspect of the invention, either individually or in combination. It shows: Fig. 1: A schematic diagram of a hydraulic system for roll stabilization and height adjustment of a motor vehicle.

[0024] The in Fig. 1. A hydraulic system 10, designed for roll stabilization and height adjustment of a motor vehicle, has a pressure source 12 designed as a hydraulic pump, which can pressurize a hydraulic medium and thereby significantly heat the hydraulic medium. The hydraulic pressure can be applied to the respective pressure consumers 14 via a pressure line 16 connected to the pressure source 12 and leading to up to four pressure consumers 14 acting on the wheels of the motor vehicle. Each pressure consumer 14 has an actuator 18 acting on the associated wheel of the motor vehicle and a hose 20 connecting the actuator 18 to the pressure line 16.

[0025] A first hydraulic section 22 and a second hydraulic section 24 are formed using pressure line 16, sharing the same pressure source 12 and a common section of pressure line 16. The flow volume Vs of the first hydraulic section 22 comprises half the volume of the common section of pressure line V. L / 2 and the non-shared part of the pressure line V S1 together, the sum of which is less than the consumer volume of the pressure consumer 14 of the first hydraulic line 22 formed by the actuator 18 and the hose 20. A line volume Vs of the second hydraulic line 24 consists of half the common part of the pressure line V L / 2 and the non-shared part of the pressure line V S2together, the sum of which is less than the consumer volume of the pressure consumer 14 of the second hydraulic line 24 formed by the actuator 18 and the hose 20. A third hydraulic line 26 and a fourth hydraulic line 28 are connected to the pressure source 12 via separate pressure lines 16. A line volume V S3 The volume of the third hydraulic line 26 is smaller than the volume of the pressure consumer 14 of the third hydraulic line 26, which is formed by the actuator 18 and the hose 20. A line volume V S4The volume of the fourth hydraulic line 28 is smaller than the volume of the pressure consumer 14 of the fourth hydraulic line 28, which is formed by the actuator 18 and the hose 20. The respective line volume of the respective hydraulic lines 22, 24, 26, 28 is so large compared to the associated consumer volume that no hydraulic fluid heated by the pressure source 12 can reach the respective pressure consumer 14. Thermal damage to the pressure consumer 14, which is designed for a significantly lower temperature load limit, can be avoided. QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] EP 2 186 662 A1

[0002]

Claims

[1] Hydraulic system (22, 24, 26, 28) for hydraulic actuation in a motor vehicle, with a pressure source (12) for generating a hydraulic pressure, a pressure consumer (14) for hydraulically applying force and a pressure line (16) for hydraulically connecting the pressure source (12) to the pressure consumer (14), wherein the pressure consumer (14) has components with a lower temperature load limit than the pressure source (12) and the pressure line (16), wherein a hydraulic consumer volume of the pressure consumer (14) is less than a line volume (V L , V S1 , V S2 , V S3 , V S4 ) of the pressure line (16) between the pressure source (12) and the pressure consumer (14). [2] Hydraulic line (22, 24, 26, 28) according to claim 1, wherein the pressure line (16) is made of a rigid pipe material, wherein the pressure consumer (14) has a hose (20) made of an elastic and / or flexible hose material and connected to the pressure line (16), wherein the hose material has a lower temperature load limit than the pipe material. [3] Hydraulic line (22, 24, 26, 28) according to claim 1 or 2, wherein the pressure consumer (14) has a relatively movable actuator (18), wherein the actuator (18) is sealed by means of a seal in the pressure consumer (14), wherein the seal has a lower temperature load limit than the pressure line (16) and the pressure source (12). [4] Hydraulic line (22, 24, 26, 28) according to one of claims 1 to 3, wherein the pressure source (14) is arranged to heat a hydraulic medium to a temperature of above 90°C, in particular above 100°C, for actuating the pressure consumer (14), wherein the pressure consumer (14) has components with a maximum temperature load limit of below 90°C, in particular below 85°C, preferably below 80°C. [5] Hydraulic line (22, 24, 26, 28) according to one of claims 1 to 4, wherein the pressure line (16) has a longer extension compared to a direct linear distance of the pressure consumer (14) to the pressure source (12). [6] Hydraulic line (22, 24, 26, 28) according to one of claims 1 to 5, wherein the pressure line (16) has a longer extension compared to a right-angled course between the pressure consumer (14) and the pressure source (12). [7] Hydraulic line (22, 24, 26, 28) according to one of claims 1 to 6, wherein the line volume (V L , V S1 , V S2 , V S3 , V S4 ) relative to the consumer volume is selected to be so large that, in a maximum actuated end position of the pressure consumer (14), a buffer volume remains between the pressure consumer (14) and a medium volume located in the pressure line (16) and previously passing the pressure source (12) to compensate for heat conduction effects with medium that has not previously passed the pressure source (12). [8] Hydraulic system (10) for a plurality of parallel hydraulic actuations in a motor vehicle, with a first hydraulic section (22) according to one of claims 1 to 7 and a second hydraulic section (24), in particular according to one of claims 1 to 7, wherein the first hydraulic section (22) and the second hydraulic section (24) share the identical pressure source (12), wherein in particular the first hydraulic section (22) and the second hydraulic section (24) share at least part of the identical pressure line (16). [9] Hydraulic system (10) according to claim 8, wherein a third hydraulic section (26), in particular according to one of claims 1 to 7, and a fourth hydraulic section (28), in particular according to one of claims 1 to 7, are provided, wherein either the first hydraulic section (22) and the second hydraulic section (24) or the third hydraulic section (26) and the fourth hydraulic section (28) share at least a part of the identical pressure line (16). [10] Use of a hydraulic system (10) according to claim 8 or 9 for roll stabilization of the motor vehicle and / or for height adjustment of the motor vehicle.

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