WO1992001867A1

WO1992001867A1 - Pressure pulsation absorber

Info

Publication number: WO1992001867A1
Application number: PCT/EP1991/001040
Authority: WO
Inventors: Franz Fleck
Original assignee: Alfred Teves Gmbh
Priority date: 1990-07-26
Filing date: 1991-06-06
Publication date: 1992-02-06
Also published as: DE4023709A1; EP0494275A1; JPH05501142A

Abstract

In systems using a pressure medium, in particular hydraulic systems, system-inherent pressure variations occur in the consumer feed flow, i.e. noise which interferes with the use of the system. To damp out such pulsations or noise, the invention calls for a hollow spherical to egg-shaped cavity with a multi-layer sound-absorbing surround, and with staggered input and outlet bores, as a pulsation-absorption chamber. The pulsation-absorption chamber can be used in any application, can be retrofitted if necessary, and ensures efficient, cost-effective noise and pulsation reduction. Other embodiments of the invention concern particular designs of the pulsation-absorption chamber and its surround.

Description

Device for absorbing pressure pulsations

The invention relates to an arrangement for absorbing pressure pulsations and other vibrations in pressurized, in particular hydraulic, systems, with at least one damping chamber arranged in the pressurized consumer inflow with inlet and outlet bores.

Such an arrangement is known from DE 38 08 901 AI and DE 39 15 781 AI in hydraulic radial piston pump systems for motor vehicles. It is used to measure the pump-related pressure fluctuations in the output circuit of the pump, i.e. to reduce the degree of non-uniformity of the feed current to the consumer. These pressure fluctuations are ultimately transferred to the actuator, e.g. on the brake pedal of a motor vehicle when used in a power steering system. The damping chambers of the known arrangements essentially have a cylindrical interior, which, due to its relatively large volume, serves as a collecting space for the hydraulic fluid and dampens the pressure fluctuations.

In addition to the pulsations generated by the pressure generator (usually a pump), generally speaking, switching, control and regulating processes also cause pressure pulsations in pneumatic or hydraulic systems. Furthermore, external forces act on the components of the pressure medium circuit via the consumers, for example on hydraulic motors, cylinders, valves, which, converted as pulsations, become effective in the pressure medium circuit. Therefore, pulsations, vibrations, airborne and structure-borne noise with unpleasant frequencies and considerable amplitudes, generated by pumps or, occur generally in pneumatic and hydraulic systems from other pulsation or vibration generators. They can cause destruction, defects, loss of function and reduced usage as a result of disturbing noises and vibrations on measuring equipment and function monitoring elements and a shortened service life of the units, as well as noise and vibration disturbance in machine shops, workshops, offices and vehicles.

The problems have so far been solved specifically for the individual products, for example for radial piston pump systems in motor vehicle systems according to the above-mentioned writings. These mostly primary and individual measures are technically and cost-unsatisfactory and generally only lead to a partial solution.

The invention is based on the object, starting from the arrangement described at the outset, of creating a damping chamber which can be used universally, possibly also be retrofitted and which ensures good and inexpensive noise and pulsation reduction.

The object is achieved according to the invention in that the damping chamber has a substantially spherical or egg-shaped interior and a sound-absorbing multi-layer casing, and that the inlet and outlet bores are arranged opposite one another offset.

The cavity with a spherical to ovoid shape and offset inlet and outlet bores causes penetrating pulsations to be constantly reflected and broken and wipe each other out.

A multi-layer coating of the damping chamber is provided so that airborne and structure-borne noise cannot propagate freely from the pressure inlet side to the consumer side.

With the arrangement according to the invention, an effective and inexpensive reduction in pulsation is thus possible, an arrangement which can be used universally and can also be retrofitted in existing systems.

A particularly effective reduction in pulsation can be achieved according to a design feature of the invention in that three damping chambers are axially aligned in series and the inlet and outlet bores are each axially offset.

In order to reduce the pressure pulsations of the pressure generator by feedback in the damping chamber, the arrangement is expediently such that the inlet bore of the damping chamber associated with the pressure generator has a relatively large cross section.

A particularly effective sheathing of the damping chambers results from the fact that the damping chambers are formed in axially successive blocks which are connected to one another via sealing arrangements, of which the two outer ones each have a pot-like extension running coaxially to one another. To reinforce the radial Sound reduction is expediently provided between the pot-like extensions at least one axially extending annular space in which a negative pressure can be produced.

Further refinements of the arrangement according to the invention and advantages result from an exemplary embodiment shown in the drawing in the form of a multi-stage damping chamber in a hydraulic system.

The only figure in the patent drawing shows three spherical cavities connected in series, the spherical chambers 1, 2, 3 of a damping body in a hydraulic system, which are surrounded by a multi-layer casing. The ball chamber 1 is connected via a relatively large inlet bore 4 to a pressurized line via which the pressure pulsations or vibrations are transmitted. Due to the large inlet hole, the pressure connection from the pressure generator (e.g. pump) to the ball chamber 1 can be seen as a one-piece pressure supply chamber.

The pulsating pressure medium therefore enters the damping body via the inlet bore 4, as indicated by the arrow. The ball chamber 1 is connected via the output bore 5 to the input bore 6 of the ball chamber 2. Correspondingly, the ball chamber 2 is connected via the output bore 7 to the input bore 8 of the ball chamber 3. There is a cross-sectional constriction in the transition area of the holes, which contributes to damping the vibration fronts. The low-pulsation pressure medium emerges from the outlet 9 of the ball chamber 3 Damping body out and in the consumer inlet.

The inlet and outlet bores of each ball chamber are - as can also be seen in the drawing - arranged axially offset from one another.

Pressure pulsations, which are caused by a pressure generator (not shown), are introduced into the ball chamber 1 provided with the large inlet bore 4. A partial reduction of the incoming pressure pulsations takes place in this spherical chamber. The effect of the spherical cavity consists in the fact that pressure pulsations that occur propagate on all sides. When they hit the cavity shell, they are reflected and reflected back according to their angle of incidence. This process is repeated continuously. It can be assumed that the majority of pulsation peaks meet pulsation troughs and thus cancel each other out. Because of the large inlet bore 4, which creates the one-piece pressure supply space to the pressure generator, the pressure pulsation from the pressure generator into the ball chamber 1 is already greatly reduced as a result of feedback, ie ^' . also due to the reduced pressure pulsation in the pressure supply system itself, the breathing work is reduced backwards into the pressure generator. The airborne noise generated in this way is also reduced. The ball chamber 1 therefore already results in a reduction in noise due to reduced breathing work inside and on the surface of the pressure generator.

To avoid the direct passage of pressure pulsations, the inlet and outlet bores 4 and 5 of the ball chamber 1 are staggered. This should also increase the absorption behavior.

The already damped, but still pulsating pressure medium enters the ball chamber 2 via the inlet bore 6. In accordance with the principle explained, there is a further reduction in pulsation as a result of the pressure waves running dead in the center of the ball. The inlet and outlet bores 6 and 7 of this ball chamber 2 are also arranged offset for the reasons mentioned above.

A remaining pulsation reduction of the vibrations still passing through the ball chamber 2 takes place in the ball chamber 3, into which the pressure medium enters via the inlet bore 8. However, this spherical chamber 3 primarily serves to largely eliminate direct pulsations (eg from hydraulic motors, cylinders, valves, etc.) coming from the consumer or indirectly caused pulsations (such as external forces acting on the aforementioned hydraulic components) . The mode of operation is corresponding to that of the spherical chambers 1 and 2.

The multi-stage ball chamber arrangement according to the figure of the patent drawing therefore causes a very strong damping of the pressure pulsations in the pressure medium.

Nevertheless, the embodiment shown in the patent drawing is to be understood as an exemplary embodiment. The embodiment of the pulsation damping body according to the invention can also consist of a single ball in its simplest form. This ball can, if necessary, be designed somewhat modified in accordance with the specific requirements. Likewise, the spherical chambers do not necessarily have to be arranged axially one behind the other if, for example, specific requirements (installation conditions) only allow a different body contour.

The spherical chambers 1 to 3 are formed in four blocks of the damping body, which are connected to one another via sealing rings 13. The ball chamber 1 is contained in the head part 10, which preferably consists of light metal, and the inner block 11, which is preferably formed by a multilayer plastic material. The ball chamber 2 is formed in a corresponding manner in the blocks 11 and 12, the latter also preferably being constructed from a multilayer plastic. The spherical chamber 3 is finally located in the blocks 12 and 15, the latter being pot-shaped and preferably also consisting of a multilayer plastic. The blocks are held in a pot-shaped receptacle 16 made of light metal, which is connected to the block 15 via an adhesive 17. Between the head-side block 10 and the inner blocks 11 and 12 on the one hand and the pot-like block 15 on the other hand there are ring channels 18 which can be connected to a vacuum generator via a connection 14. The vacuum generator can be, for example, the intake manifold or the carburetor of a motor vehicle or the intake constriction of a pump, etc. The described sheathing of the ball chamber serves to ensure that it comes from the pulsation generator Structure-borne noise is not passed on via the damping body. For this reason, the housing of the damping body has a multilayer structure both in the direction of flow and radially outward. In the case of an axial pass, for example, the structure-borne noise must first pass through a metal layer. It is then passed through a plastic part, the rate of propagation of the pulsations being greatly reduced or changed. The structure-borne noise that still penetrates into the spherical chambers or the structure-borne noise that is still indirectly caused here by pulsation / breathing work is also reduced in the radial direction. In this case, the airborne noise occurring is primarily absorbed by the vacuum chamber 18, which surrounds the spherical chambers in a ring. This vacuum chamber also has a dampening effect on structure-borne noise. In the exemplary embodiment shown, the structure-borne sound pressure waves must penetrate a total of five different layers (including the spherical chamber shells). The number and sequence of the layers is to be determined and determined specifically by the person skilled in the art in a corresponding investigation for the respective application.

The basic principle of the multi-layer cladding therefore consists in the fact that structure-borne and airborne noise that occurs has to change its speed of sound propagation as the different layers pass through; it is also broken at the interfaces. He therefore loses energy. This effect is supported by the substantial absence of air in the vacuum chamber 18. In addition, the stratification can influence the frequency of the sound, which nevertheless penetrates outwards, in such a way that it is more bearable for the user.

Claims

1. Arrangement for absorbing pressure pulsations and other vibrations in pressurized medium, in particular hydraulic systems, with at least one damping chamber switched on in the pressurized consumer flow with inlet and outlet bores, characterized in that the damping chamber (1,2, 3) has an essentially spherical or egg-shaped interior and a sound-absorbing multilayer casing (10, 11, 12, 15), and that the inlet and outlet bores (4 to 9) are arranged opposite one another, offset.

2. Arrangement according to claim 1, characterized g e k e n n ¬ z e i c h n e t that three damping chambers (1 to 3) connected axially in line and the

Inlet and outlet bores (4 to 9) are each arranged axially offset.

3. Arrangement according to claim 1 or 2, characterized in that the inlet bore (4) of the damping chamber (1) assigned to the pressure generator has a relatively large cross section.

4. Arrangement according to claim 1 or 3, characterized in that the damping chambers (1 to 3) in axially successive blocks (10, 11, 15) are formed, which are connected to one another via sealing arrangements (13), of which the two outer (10, 15) each have a pot-like extension that extends coaxially to one another.

5. Arrangement according to claim 4, characterized in that the blocks have a multilayer structure made of plastic material and the outer block (10) penetrated by the input bore (4) of the damping chamber has a metallic cap-shaped closure.

6. Arrangement according to claim 4 or 5, characterized in that the blocks are accommodated in a metallic pot arrangement (16) which is penetrated by the output bore (9) of the damping chamber.

7. Arrangement according to one of claims 4 to 6, characterized in that at least one axially extending annular space (18) is provided between the pot-like extensions, in which an oppression can be produced.

8. Arrangement according to claim 5 or one of the following, so that the damping chambers (1 to 3) are made of plastic or metallic or have a metallic inner lining.