The air cushion shock absorber of can regulate rigidity and damping
Technical field
The present invention relates to a kind ofly can regulate the tandem double-chamber air-spring vibration isolator of rigidity, damping and natural frequency according to load and actual working environment.This pneumatic spring is realized the adjustable continuously of damping size by regulating the slit length between two chambers; Realize the adjusting of vibration isolator natural frequency and rigidity by the height of regulating the damping chamber.The vibration isolation that the present invention is primarily aimed at ultraprecise test stand, ultra-precision machine tool and optical table requires exploitation, belongs to ultraprecise processing and fields of measurement.
Background technique
In ultraprecise processing, IC manufacturing and optically detecting process, can influence equipment and reach its final performance, so the equipment in these fields extensively adopts various vibration isolators to reach the purpose that excludes vibration from outside and inner vibration.Wherein simple and reliable, with low cost and excellent performance has obtained using widely the tandem double-chamber air-spring with it.It can form the hybrid type vibration isolator with other active vibration isolation, also can use separately.
The tandem double-chamber air-spring is to produce damping by air through the aperture between last/lower chambers.The non-linear turbulent flow that mainly comes from air of this class pneumatic spring, so, can do following effort usually in order to make this pneumatic spring reduce non-linear factor as far as possible:
1) smooth and nothing in my way thing in the chamber;
2) small structure is level and smooth and thickness is little;
3) increase little hole number, allow air flows be similar to laminar flow, use porous material to make dividing plate, obtain the method for laminar-flow air as proposing;
4) the big displacement of restriction load, the magnitude that common commercial double-chamber air-spring piston stroke is 10 μ m.
Along with the development of nanotechnolgy, more and more equipment have proposed high request simultaneously to natural frequency, rigidity and the damping of vibrating isolation system.Vibration at the ground transmission, classical theory of vibration isolation is that the natural frequency with vibration isolator designs far below needing below 0.707 of the device for vibration insutation first rank natural frequency, the vibration of each order frequency of equipment all is inhibited, the first rank natural frequency of existing ultraprecise equipment is usually between 20~80Hz, this just requires the vibration isolator first rank natural frequency is set to low-down level, the vertical vibration isolation natural frequency of classic double-chamber air-spring has reached about 0.5Hz in the world at present, level has reached the level about 0.3Hz, and it is very soft to that is to say that vibration isolator can be designed.Then wish the hard more good more of design of vibration isolator at the vibration that load causes, just set 20Hz as the natural frequency of passive vibration isolation parts in the STATICS2000 vibration isolator of TMC Corp..For the demand of this contradiction, just need be according to different actual conditions, i.e. the vibration isolation demand of balance ground transmitting vibrations and load vibration and adjusting accordingly makes vibration isolator can take into account the vibration isolation needs to ground vibration and load vibration simultaneously preferably.Commercial general vibration isolator is normally classified physical device, at each kind equipment is that load (comprising shape and quality) and equalization vibration environment with equalization designs, during so actual the use, carry out the performance that the necessary parameter adjusting can be brought into play vibration isolator better.
The hole diameter of tandem double-chamber air-spring (be generally 0.2~0.6mm) and chamber height fix, at certain load and certain vibration environment, its rigidity that provides is certain, damping change characteristic and initial characteristic are exactly certain.If change load and place environment, relevant parameter W (load) and ω (forcing frequency) will change, though natural frequency can not change, but new system will have new stiffness K and damping C correlation properties, and the rigidity and the damping of new system might not be best to new system, cause rigidity to descend such as load W reduction, the anti-vibration performance that vibrates for load will descend, and this just need be according to the rigidity and the damping parameter of new load and environment adjusting vibration isolator.So be necessary to research and develop the pneumatic spring that to regulate parameter.
As shown in Figure 1, existing common tandem double-chamber air-spring is made up of two chambers: VS is spring chamber (upper chamber), and VD is damping chamber (lower chambers).Its damping comes from the orifice restriction effect between spring chamber and the damping chamber, and hole diameter is usually between 0.2~0.6mm.The theoretical model of this pneumatic spring design considerations is the ZENER model that was proposed in 1971 by people such as J.E.Ruzicka, and its rigidity is defined as:
Constant γ=Cp/Cv=1.4 (air), P=pressure, A=chamber net sectional area, V=volume;
W=PA and V=h get again
Wherein h is the effective total height of chamber;
Natural frequency is:
This natural frequency is the load quality M that does not rely on system at gas effective height h maintenance constant as can be seen.
As shown in Figure 2, be the simplification theoretical model of tandem double-chamber air-spring.When extremely low frequency, spring rate is NK/ (N+1), the C=of damping simultaneously ∞, and damping cavity locking during extremely high frequency, spring rate is increased to NK damping simultaneously C=0, and wherein N is a stiffness coefficient.Wherein the characteristic that changes between 0~∞ of damping C is decided by forcing frequency ω and hole diameter.This pneumatic spring can provide low-down natural frequency.To most process equipment, pneumatic spring provides the requirement of high rigidity low resistance when low rigidity high damping and high frequency are provided when having realized low frequency.
Existing tandem double-chamber air-spring is regulated the method for damping for regulating by valve (as needle-valve).This mode has adopted ripe valve technology, is a kind of regulative mode easily.But still there is certain problem, at first little hole number is many on the dividing plate, valve of an aperture is obviously uneconomical, Ji Zai mode is generally a valve and controls several passages (aperture) in the literature, do the structure that has increased on the one hand in the chamber like this, the assembling difficulty has increased turbulent flow has simultaneously promptly increased nonlinear factor, and the cost of valve is higher relatively on the other hand.
The air pressure P that changes in two chambers can reach the purpose of regulating rigidity, this mode is simple and be widely used, but the adjusting of pressure is compressed the restriction of equipment such as machine, provide the highest 8 left and right sides atmospheric pressure as the big physical efficiency of common compressor is stable, common steam hose can bear the highest 6~8 atmospheric pressure, so just regulates the rigidity inconvenience on a large scale.
Summary of the invention
In order satisfy to adapt to the needs of vibration isolation under different loads and the varying environment, the present invention proposes a kind ofly can regulate the air cushion shock absorber of damping and rigidity on a large scale continuously, further to improve the functional structure of double-chamber air-spring.
Vibration isolator of the present invention has the shell of hollow, inside is cylindrical, described shell internal fixation has dividing plate, described enclosure is divided into upper chamber and lower chambers, described dividing plate is provided with a plurality of axial holes, the upper chamber top is provided with the piston that is connected with described body seal, shut with base plate the lower chambers bottom, it is characterized in that: the axial hole on the described dividing plate has two rows, two row's axial holes are uniformly distributed along the circumference accordingly, with described axial hole corresponding position, have radially deep hole along described dividing plate radial direction, each radially assembles a damping adjustable lever in the deep hole, respectively has a slit with two axial hole corresponding positions on each damping adjustable lever.
As a kind of improvement of the present invention, described lower chambers bottom also is provided with the Height Adjustment mechanism that can regulate the lower chambers height.
The present invention has adopted the slit throttling to produce the mode of damping, different existing aperture modes in order to realize regulating continuously the purpose of damping.Hole diameter is fix constant, has only the purpose that just can reach adjusting by supplementary equipment such as valve, and the variation of slit by its length reaches the purpose of regulating damping, seems more convenient and economical than aperture.
The present invention compares existing technology and has following advantage:
The first, the present invention also can realize the adjusting of vibration isolator rigidity in conjunction with the adjusting of air pressure by the change of damping cavity volume (highly).
The second, the present invention has realized the adjusting of vibration isolator natural frequency by the change of damping cavity volume (highly).
The 3rd, the present invention has realized the adjustment of vibration isolator damping by the feed movement of adjustable lever.
The 4th, the double-chamber air-spring isolation mounting of variable natural frequency of the present invention and damping is simple to operate, and environmental suitability is strong, applicable to other such as fields such as ultra-precision machine tool, optical tables.
Description of drawings
Fig. 1 is the principle schematic of existing double-chamber air-spring vibration isolator.
Fig. 2 is the theoretical model schematic representation of existing double-chamber air-spring vibration isolator.
Fig. 3 is the schematic representation of embodiments of the invention.
Fig. 4 is the generalized section of embodiments of the invention.
Fig. 5 a has shown the adjusting direction of damping adjustable lever of the present invention.
Fig. 5 b has shown that damping adjustable lever of the present invention is at first limit position.
Fig. 5 c has shown that damping adjustable lever of the present invention is at second limit position.
Fig. 5 d is the schematic representation of the groove processed on the damping regulating lever of the present invention.
Fig. 5 e is the schematic representation of installing on the damping regulating lever of the present invention after O shape is enclosed.
Fig. 6 is the schematic representation of Height Adjustment of the present invention mechanism.
Embodiment
Specify the present invention below in conjunction with accompanying drawing.
Fig. 3 and Fig. 4 have shown an embodiment of the air cushion shock absorber of can regulate rigidity of the present invention and damping.Described vibration isolator has the shell 2 of hollow, and the inside of shell is cylindrical, and the outside of shell can be cylindrical or rectangle.Shell 2 internal fixation have dividing plate 11, and shell 2 inside are divided into upper chamber 18 and lower chambers 19, and described dividing plate 11 is provided with a plurality of axial holes 13, and (it typically has a diameter from 0.2~0.6mm).Upper chamber 18 tops are connected with piston 7 by rubber turn 5, rubber turn 5 outer ends are placed on shell 2 top stage, press upper sealing panel 6 above, by bolt that upper sealing panel 6 and shell 2 is fastening, rubber turn 5 inboards are fastening by retaining ring and piston 7 outer surfaces, thus the sealing of upper chamber 18 when guaranteeing that piston moves up and down.Shut with base plate 1 lower chambers 19 bottoms.The middle and upper part of shell 2 connected provide for inner upper chamber 18 pressure air on tracheae 8, the middle and lower part has connected the following tracheae 9 that pressure air is provided for inner lower chambers 19.
Axial hole on the described dividing plate 11 has two rows, and two row's axial holes 13 are uniformly distributed along the circumference accordingly.In this example, and the axial hole of eight rectangles of every row's circumference uniform distribution (10 * 6mm), 45 ° at interval.Also adjustable axle is to the quantity of through hole or the shape of conversion axial hole, as the above manhole of diameter 10mm but as required.
With axial hole 13 corresponding positions, have radially deep hole 21 along dividing plate 11 radial direction, in this example, the quantity of corresponding axial hole and arrangement, radially the quantity of deep hole is eight also, is shaped as circle.But the shape of also convertible radially deep hole as required.
Each radially assembles a damping adjustable lever 3 in the deep hole 21, respectively has a slit 14 with two axial hole 13 corresponding positions on each damping adjustable lever 3, and is wide as 0.15mm.The length of slit 14 and axial hole 13 equal in length on damping adjustable lever 3 length directions.Termination, the outside assembling locking device 4 of damping adjustable lever 3.Can reach the purpose of regulating the vibration isolator damping by the degree of depth of regulating damping adjustable lever 3 insertion shells 2, locking device 4 lockings are passed through in each back that finishes of adjusting.
Fig. 5 a has shown the adjusting direction of damping adjustable lever of the present invention.When regulating damping, move forward and backward damping adjustable lever 3, the length that slit 14 exposes to the open air in axial hole 13 on the damping adjustable lever 3 changes, thereby the vibration isolator damping characteristic also can be changed.Damping adjustable lever 3 regulation ranges are that promptly slit 14 grows out of nothing in axial hole 13 between two limit positions shown in Fig. 5 b and Fig. 5 c.Only need move forward and backward damping adjustable lever 3 (manually or control servo all right) when regulating damping, slit length on the axial hole internal damping adjustable lever 3 is changed, thereby reach the purpose of regulating damping linearly continuously, simultaneously simple in structurely be convenient to make assembling.
Fig. 5 d and Fig. 5 e have shown the sealing configuration on the damping adjustable lever.In order to guarantee that slit is unique passage between the chamber up and down, prevent gas by damping adjustable lever 3 and radially the space between the deep hole 21 flow, and two place's slits on the isolated fully damping adjustable lever 3 just must be considered corresponding sealing configuration.Processed radial groove 25 at the front and back position of damping adjustable lever two place's slits and formed sealing configurations, the air flows between isolated two place's slits with deep hole 21 radially so that O shape rubber seal to be installed; Simultaneously slit 14 positions process axial shallow slot 22 so that rubber weather strip to be installed on damping adjustable lever 3 axial directions, prevent gas by damping adjustable lever 3 and radially the space between the deep hole 21 flow.In this example, for easy for installation and reliable, what install in radial groove 25 and the axial shallow slot 22 is a rubber seal assembly 23 of processing/linking together.
Described lower chambers 19 bottoms also are provided with the Height Adjustment mechanism that can regulate the lower chambers height, as shown in Figure 6.The part that Fig. 6 irises out for ellipse among Fig. 4, the i.e. enlarged diagram of Height Adjustment mechanism.Described Height Adjustment mechanism comprises airtight lower chambers lower shoe 12 moving up and down, be installed in the screw-nut body of lower chambers lower shoe 12 downsides, and is fixed on the leading screw end, and is located at the adjusting cap 10 in the shell bottom plate 1 middle part through hole.Described screw-nut body comprises the nut 16 of the unsettled setting that is fixed on lower chambers lower shoe 12 bottoms, and with the leading screw 15 of nut 16 component movement pairs.Regulate cap 10 is installed in shell bottom plate 1 middle part by bearing 22 manhole place, like this after the vibration isolator assembling, just can regulate cap 10 from the outside by the direct turn of the manhole at shell bottom plate 1 middle part, realize moving up and down of lower chambers lower shoe 12, thereby make the height of lower chambers 19 that corresponding the variation be taken place.Rubber seal O shape circle 17 has also been installed in lower chambers lower shoe 12 sides, guarantees the sealing of lower chambers.
Because the rigidity of vibration isolator is:
Constant γ=Cp/Cv=1.4 (air) wherein, W load weight, h are the chamber effective height;
At certain load, vibration isolator height h change can make stiffness K numerical value change like this.The vibration isolator natural frequency is simultaneously:
Wherein g is a gravity accleration;
As long as its numerical value change changes less than rigidity numerical value ground significantly, so by suitable adjusting, with regard to the support stiffness of energy acquisition system satisfaction and suitable vibration isolator natural frequency.
The embodiment of the invention described above only is illustrative, but not determinate, and any improvement that does not break away from essence of the present invention and spirit all is subjected to the protection of claim of the present invention.