WO2007101696A1

WO2007101696A1 - Fluid accumulator

Info

Publication number: WO2007101696A1
Application number: PCT/EP2007/002032
Authority: WO
Inventors: Dirk Kesselgruber
Original assignee: Trw Automotive Gmbh
Priority date: 2006-03-08
Filing date: 2007-03-08
Publication date: 2007-09-13
Also published as: DE102006010738A1

Abstract

A fluid accumulator (8), in particular for hydraulic actuators (40) of chassis stabilization systems, has a housing, which surrounds a storage space, and a blocking element (14) which divides the storage space in a fluid-tight manner into two fluid chambers (16, 18) with variable volume, wherein each fluid chamber (16, 18) has a fluid connection, and the blocking element (14) can be moved in the storage space between two end positions.

Description

fluid reservoir

The invention relates to a fluid reservoir, in particular for hydraulic actuators of suspension stabilization systems.

Fluid accumulators are known from the prior art and are used in particular in hydraulic circuits for the rapid provision of missing hydraulic fluid or for rapid absorption of excess hydraulic fluid. In systems for chassis stabilization, so-called external activation of an actuator poses a risk of cavitation in a pressure chamber of the actuator. External control in this context means that the actuator does not perform a movement due to an increase or decrease of hydraulic fluid (pressure control), but that hydraulic fluid must be added or removed by an imposed movement. Forced movements for a hydraulic actuator arise when used in a chassis stabilization system, e.g. by road bumps such as potholes, etc., which are followed by the wheel associated with the actuator. In connection with a possible external control of a hydraulic actuator, it is particularly important to prevent rapid hissing due to cavitation. Due to the internal friction and inertia of the hydraulic fluid special precautions must be taken for this purpose.

DE 101 11 551 A describes a piston-cylinder unit for

Chassis stabilization, which acts as a damper and hydraulic actuator. to

In order to solve the cavitation problem, DE 101 11 551 A proposes, in general, to connect each actuator working chamber to a so-called minimum pressure supply source, from which hydraulic fluid can be sucked.

The object of the invention is therefore to solve the Kavitationsproblem concretely and with little technical effort.

For this purpose, a fluid accumulator is provided, in particular for hydraulic actuators of chassis stabilization systems, with a housing which encloses a storage space, and a shut-off element which encloses the storage space - -

fluid-tight divided into two fluid chambers with variable volume, each fluid chamber has a fluid port and the shut-off between two end positions in the reservoir is movable. This offers the advantage that the fluid reservoir can provide a fluid volume by means of its fluid chambers during an actuator movement. Furthermore, the fluid storage is a simple, passive component and without major problems to integrate in a hydraulic circuit.

The shut-off element can each close a fluid connection at its end positions. In order for the fluid reservoir after the provision of the fluid volume of its fluid chamber prevents further fluid flow and no longer exerts any influence on the hydraulic circuit.

In one embodiment, a positioning means is provided which acts on the shut-off element in a rest position centrally in the storage space. By this measure, it is ensured that the fluid reservoir holds approximately the same volume of fluid regardless of the direction of the actuator movement.

In a particular embodiment, the positioning means extends through at least one fluid chamber. For a particularly simple construction is possible because the position means is supported on the one hand to an axial end of the fluid chamber and the other on the shut-off.

In this embodiment, the positioning means may be at least one spring. This is particularly advantageous because springs are very inexpensive and durable positioning means.

In a further embodiment, the fluid reservoir is connected in parallel with a hydraulic actuator. With this arrangement, a reduction in the risk of cavitation in two actuator chambers is possible with a fluid reservoir.

Further features and advantages of the invention will be described in detail below with reference to a preferred embodiment. Reference is made to the accompanying drawings, in which:

- Figure 1 is a section through a fluid reservoir according to the invention;

FIG. 2 shows a shut-off element of the fluid reservoir from FIG. 1 in detail; - o ^■

- Figure 3 is a schematic representation of the fluid reservoir according to the invention, connected in parallel with a hydraulic actuator, in a rest position;

Figure 4 is a schematic representation of the fluid storage device according to the invention, connected in parallel with a hydraulic actuator, in a

Pressure control; and

- Figure 5 is a schematic representation of the fluid reservoir according to the invention, connected in parallel with a hydraulic actuator, in a third-party drive.

1 shows a fluid reservoir according to the invention, in particular for hydraulic actuators of suspension stabilization systems, with a housing 10 which encloses a reservoir 12, a shut-off element 14 which fluid-tightly divides the reservoir 12 into two fluid chambers 16, 18 with variable volume, each fluid chamber 16, 18 has a fluid connection 20, 22 and the shut-off element 14 is movable between two end positions in the storage space. The housing 10 includes a cylindrical side wall 24 and an upper cap 26 and a lower cap 28. The caps 26, 28 are fixed and fluid-tightly connected to the side wall 24. Furthermore, the cover caps 26, 28 each have a central fluid connection 20, 22. The shut-off element 14 is acted upon by a positioning means in a rest position centrally in the storage space 12. The positioning means comprises in Figure 1, two springs 30, each extending through a fluid chamber 16, 18 extend. In each case one end of the springs 30 bears against the shut-off element 14, the other end surrounds the fluid connection 20 or 22 and engages on a recess 32 or 34 of the cover caps 26, 28. The recesses 32, 34 of the caps 26, 28 are each facing the storage space 12 and formed so that they can each receive one of the springs 30 in their compressed state. Consequently, it is possible that in each case an axial end of the shut-off element 14 acts on the edge of the cover caps 26 and 28 and thus an upper and lower end position of the shut-off element 14 is defined.

Figure 2 shows the shut-off element 14 in detail, with an upper axial seal 36, a lower axial seal 37 and a radial seal 38. The radial seal 38 is formed so as to engage the side wall 24 of the Housing 10 slidably abuts. This creates a largely fluid-tight connection with the usual lubrication and leakage losses. When occurring pressure differences between the fluid ports 20, 22, the shut-off 14 moves depending on a spring hardness and a possible bias of the springs 30 between the upper and lower end position. In particular, in these end positions, the pressure differences at the fluid connections can be very large. Therefore, the radial seal 38 is supported in the end positions by the axial seal 36 and 37, respectively. The axial seal 36, 37 of the shutoff 14 is pressed by the pressure difference on the edge region of the caps 26, 28 and prevents fluid flow through the fluid reservoir 8 (see in particular Figures 4 and 5). The shut-off element 14 thus closes at its end positions in each case a fluid connection 20, 22nd

FIG. 3 shows an actuator 40 in piston-cylinder construction. A piston 42 divides a cylinder 44 into two pressure chambers 46, 48. The fluid reservoir 8 is connected in parallel with the hydraulic actuator. This means that in each case a fluid chamber 16, 18 communicates with a pressure chamber 46, 48 via an upper fluid line 50 and a lower fluid line 52, respectively. Figure 3 shows this parallel circuit in the event that either no pressure, or equal pressure applied to the pressure chambers. The piston 42 and the shut-off element 14 are located in a central rest position in the cylinder 44 or in the storage space 12.

For a clearer illustration, the fluid reservoir 8 in FIGS. 3-5 is markedly enlarged in relation to the actuator 40. For the prevention of cavitation only one, in relation to the volume of the pressure chambers 46, 48, small volume is needed.

FIG. 4 shows the parallel connection of the actuator 40 with the fluid reservoir 8 from FIG. 3 during a pressure control. Compared to FIG. 3, the pressure in the upper fluid line 50 has been increased. This happens, for example, when a coupled to the piston 42 vehicle wheel is to be moved relative to the coupled with the cylinder 44 vehicle body down. The fluid lines are for this purpose coupled to a pressure source, for example a pump (not shown). The high pressure is not only on the Pressure chamber 46 of the actuator 40, but also to the upper fluid chamber 16 of the fluid reservoir 8 at. Thus, the shut-off element 14 moves to the lower end position, wherein the fluid of the lower fluid chamber 18 is pushed out of the chamber until the lower axial seal 37 abuts the edge of the lower cap 28 and shuts off a further fluid flow. Due to the small volume of fluid in the fluid chambers 16, 18 in relation to the pressure chambers 46, 48, the response and reaction time of the actuator is at most negligibly increased by the parallel connection of the fluid reservoir.

FIG. 5 shows the parallel circuit from FIGS. 3 and 4 in the case of external activation. Thereby, e.g. the piston 42 from a forced movement relative to the cylinder down. This increases the pressure in the lower pressure chamber 48 and reduces the pressure in the upper pressure chamber 46 of the actuator 40 abruptly. The pressure drop in the upper pressure chamber is likely to cause cavitation. Since the fluid reservoir 8 is connected in parallel with the actuator 40, a higher pressure is present at the lower fluid port 22 than at the upper fluid port 20. The result is a suction at the upper fluid port 20 and at the same time an overpressure at the lower fluid port 22. Thus, the shut-off element 14 moves upward and the upper pressure chamber 46 of the actuator 40 to the fluid located in the upper fluid chamber 16 to. Due to the spatial proximity of the fluid chambers 16, 18 and the pressure chambers 46, 48, this happens very quickly, whereby an occurrence of cavitation in the actuator 40 is prevented.

Claims

- D patent claims

1. Fluid reservoir (8), in particular for hydraulic actuators (40) of chassis stabilization systems, comprising a housing (10) which encloses a reservoir (12) and a shut-off element (14) which seals the reservoir (12) fluid-tightly in two fluid chambers ( 16, 18) with variable volume, wherein each fluid chamber (16, 18) has a fluid connection (20, 22) and the shut-off element (14) between two end positions in the reservoir (12) is movable.

Second fluid reservoir (8) according to claim 1, characterized in that the shut-off element (14) at its end positions in each case a fluid connection (20,

22) closes.

3. fluid reservoir (8) according to any one of the preceding claims, characterized in that a position means is provided which acts on the shut-off element (14) in a rest position in the middle of the storage space (12).

4. fluid reservoir (8) according to claim 3, characterized in that the positioning means extends through at least one fluid chamber (16, 18).

5. fluid reservoir (8) according to claim 3 or 4, characterized in that the positioning means is at least one spring (30).

6. fluid reservoir (8) according to any one of the preceding claims, characterized in that the fluid reservoir (8) with a hydraulic actuator (40) is connected in parallel.