Magnetic fluid passive dynamic vibration absorber utilizing particle collision damping

Abstract

Magnetic liquid passive dynamic vibration absorber using particle collision damping belongs to the field of vibration control. It successfully solves the problem that existing particle collision dampers cannot be applied to low-frequency vibration and semi-active control effect is poor. The damper includes a shell (1), a left ball (2), a left flow baffle (3), a permanent magnet (4), a magnetic liquid (5), a right flow baffle (6) and a right ball (7). When the outside is subjected to low-frequency vibration, liquid viscous damping is generated between the permanent magnet (4) and the magnetic liquid (5), and the vibration energy is reduced. When the outside is subjected to high-frequency vibration, particle collision damping is generated in the chamber where all the left balls (2) and right balls (7) are located, and the vibration energy is reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of vibration control of machines, mechanisms and various parts in gravity and weightless environments. BACKGROUND

[0002] The magnetic liquid dynamic vibration absorber is a passive vibration absorber, which is composed of three elements of inertia mass, damping unit and elastic unit. The elastic force is usually provided by the suspension force of the magnetic liquid, and the damping force is provided by the viscous friction of the magnetic liquid. The sensitivity to inertia force is very high. However, due to the very limited damping force and elastic force provided by the magnetic liquid, the working frequency band of the magnetic liquid dynamic vibration absorber is very narrow, and usually only within 10Hz has good effect.

[0003] To overcome this problem, some documents use the method of increasing surface roughness and porous medium to improve damping force, such as: document 1 (patent application number CN 112727972 B) increases the friction damping by texturing the contact surface of the magnetic liquid, but the damping of this method cannot be automatically adjusted according to the vibration frequency, and the damping force provided by the viscous friction of the magnetic liquid is still very limited and cannot meet the high-frequency vibration demand. Document 2 (patent application number CN 112392888 B) increases the porous medium on the surface of the permanent magnet to improve the friction damping and protect the permanent magnet, but the elastic force provided by the spring is a linear force, and the stiffness does not change with the vibration frequency. Moreover, when the frequency of vibration is large, the spring is easy to fail, thereby shortening the service life of the dynamic vibration absorber. Document 3 (patent application number CN 112392887 B) also increases the porous medium on the surface of the permanent magnet, and uses the protruding structure machined on one side of the end cover to extrude the magnetic liquid, so as to realize the reset of the permanent magnet through the change of the suspension force of the magnetic liquid. However, the suspension force of the magnetic liquid is very limited, and it is invalid for high frequency. Moreover, when the external vibration frequency is large, the permanent magnet is easy to collide with the protruding structure on the end cover, and even cause the fragmentation of the permanent magnet. Document 4 (patent application number CN 112392885 B), document 5 (patent application number CN 112392886 B) and document 6 (patent application number CN 112392890 B) all use the protruding parts at both ends of the inertial mass block to extrude the magnetic liquid in the pipeline through the porous medium to realize energy dissipation. However, this damping force still belongs to liquid viscous damping, and the damping force is limited, which is not good in high-frequency vibration occasions. In addition, document 6 uses compressed air to improve the restoring force, which is unreliable. Document 7 (patent application number CN 114962514 B) uses collision damping, suspends the ball in a cavity filled with magnetic liquid and having an elastic soft pad under the action of an external magnetic field, and improves the application frequency band through collision damping. However, there is only one ball in the invention, and the collision damping only occurs between the copper ball and the soft pad inside the cavity, so the damping force is very limited. When the vibration frequency is large, the damping force of the damper cannot meet the requirements. Therefore, at present, there is still lack of a magnetic liquid dynamic vibration absorber whose damping and stiffness can be nonlinear and can be automatically adjusted according to the vibration frequency. SUMMARY

[0004] The technical problem to be solved by the present application is that the existing magnetic liquid dynamic vibration absorber has very limited damping force and elastic force, resulting in a very narrow working frequency band, and the vibration suppression effect is not good for vibration greater than 10 Hz, and completely ineffective for vibration of 100 Hz or even above 1000 Hz. The present application provides a magnetic liquid passive dynamic vibration absorber using particle collision damping, which solves the problem of low frequency vibration by using the viscous damping force of the magnetic liquid; and by filling non-magnetic balls in the two chambers of the shell, a particle collision damping with strong non-linear characteristics is formed, thereby solving the problem of insufficient damping force under high frequency vibration. Therefore, the dynamic vibration absorber has excellent vibration reduction performance for low frequency vibration of only a few hertz or high frequency vibration of thousands of hertz.

[0005] The technical solution adopted by the present application to solve its technical problem is that the damper comprises a shell, left balls, a left flow barrier, a permanent magnet, a magnetic liquid, a right flow barrier and right balls.

[0006] The left flow barrier and the right flow barrier are installed in the shell to divide the shell into three chambers, and the magnetic liquid is filled in all the chambers.

[0007] All the left balls are installed in the left chamber between the shell and the left flow barrier to form a left particle collision damping assembly; all the right balls are installed in the right chamber between the shell and the right flow barrier to form a right particle collision damping assembly. The left balls and the right balls are made of non-magnetic metal, and the density is greater than the density of the magnetic liquid. If the left balls or the right balls are solid, the metal density is greater than the density of the magnetic liquid; if the left balls or the right balls are hollow, the equivalent density is greater than the density of the magnetic liquid. The number of left balls and right balls is greater than 1, i.e. at least 2, to ensure that all left balls and all right balls will collide with each other after vibration, generating particle collision damping. The size of all left balls or right balls can be the same or in the form of large and small combination, but the minimum diameter must be greater than 1 mm, and the maximum radius cannot exceed 1 / 2 of the minimum size of the chamber. To prevent the size of the left balls or the right balls from being too small and too densely packed, and to prevent the size of the left balls or the right balls from being too large and causing too limited movement space in the shell, affecting the particle collision damping force between the left balls or the right balls. The filling rate of the left balls and the right balls in the chamber is 10% to 90%. The magnetic liquid must be filled in the shell without any cavity.

[0008] The permanent magnet is installed in the chamber between the left flow barrier and the right flow barrier to form a magnetic liquid damping element. The permanent magnet can be rectangular or cylindrical, but its shape must be the same as the shape of the inner cavity of the shell, and the size is smaller than the size of the inner cavity of the shell.

[0009] The left and right baffle plates are made of non-permeable material and have small holes, the number of which is 2-100, and the maximum diameter of the holes is smaller than the minimum diameter of the left and right spheres. The small holes are used for the flow of the magnetic liquid between the chambers and prevent the left and right spheres from flowing out of the chambers.

[0010] The shell is made of non-permeable metal, and the inner cavity can be rectangular or cylindrical. The shell must be completely sealed to prevent the magnetic liquid from flowing out of the shell.

[0011] The present application has the following advantages over the prior art: (1) the permanent magnet is suspended in the magnetic liquid by the self-suspension effect of the permanent magnet in the magnetic liquid, thus being very sensitive to inertial force and being applicable to vibrations with a frequency of 100 Hz or even 10 Hz; (2) the left and right spheres are made of non-permeable metal, forming particle collision damping, which can be applied to vibrations with a frequency of several hundred or even several thousand Hz; (3) the left and right spheres are affected by the magnetic suspension force of the magnetic liquid under the action of the external magnetic field formed by the permanent magnet, and will not drift due to the weightlessness environment or have the problem of excessive solid friction; (4) the permanent magnet, the left sphere and the right sphere are separated in three independent chambers by the left and right baffle plates with holes, so that the movement of the permanent magnet will not be disturbed by the left and right spheres in low-frequency vibrations, and the permanent magnet will not participate in direct collision in high-frequency vibrations, while the left and right spheres can be affected by the magnetic field of the permanent magnet, increasing the collision probability between the left and right spheres; (5) the magnetic liquid damping and particle collision damping composed of the suspended permanent magnet, left sphere and right sphere in the three chambers of the shell have both the low-frequency vibration suppression characteristics of the magnetic liquid damper and the high-frequency vibration suppression characteristics of the particle collision damping, thus expanding the application frequency band. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 Schematic diagram of a magnetic liquid passive dynamic vibration absorber using particle collision damping;

[0013] In the figure: shell 1, left sphere 2, left baffle plate 3, permanent magnet 4, magnetic liquid 5, right baffle plate 6 and right sphere 7. DETAILED DESCRIPTION

[0014] The present application is further described in detail with reference to the drawings: a magnetic liquid passive dynamic vibration absorber using particle collision damping, as shown in Figure 1 , which includes: a shell 1, a left sphere 2, a left baffle plate 3, a permanent magnet 4, a magnetic liquid 5, a right baffle plate 6 and a right sphere 7.

[0015] The left and right baffle plates 3 and 6 are installed in the shell to divide the shell into three chambers, and the chambers are filled with the magnetic liquid 5.

[0016] All left spheres 2 are installed in the left chamber between the shell 1 and the left baffle 3, forming a left particle collision damping assembly; all right spheres 7 are installed in the right chamber between the shell 1 and the right baffle 6, forming a right particle collision damping assembly. The left spheres 2 and the right spheres 7 are made of non-magnetic metal, and the density is greater than the density of the magnetic liquid 5. If the left spheres 2 or the right spheres 7 are solid, the metal density is greater than the density of the magnetic liquid 5; if the left spheres 2 or the right spheres 7 are hollow, the equivalent density is greater than the density of the magnetic liquid 5. The number of left spheres 2 and right spheres 7 is greater than 1, that is, at least 2, to ensure that all left spheres 2 and all right spheres 7 will collide with each other after vibration, generating particle collision damping. The size of all left spheres 2 or right spheres 7 can be the same, or can be in the form of large and small combinations, but the smallest diameter must be greater than 1 mm, and the largest radius cannot exceed 1 / 2 of the smallest size of the chamber. To prevent the size of the left spheres 2 or the right spheres 7 from being too small and too densely packed, and to prevent the size of the left spheres 2 or the right spheres 7 from being too large, causing the movement space in the shell 1 to be too limited, affecting the particle collision damping force between the left spheres 2 or the right spheres 7. The filling rate of the left spheres 2 and the right spheres 7 in the chamber is 10% to 90%.

[0017] Large-sized spheres are more sensitive to low-frequency vibration, and small-sized spheres have greater damping force for high-frequency vibration. The selection is made according to the specific vibration situation. If the vibration frequency is relatively single, when the vibration frequency of the object to be damped is only a few tens of hertz, the number of left spheres 2 and right spheres 7 should be reduced, preferably controlled within 10, and the size of the left spheres 2 and right spheres 7 should be increased; if the vibration frequency is relatively single and the frequency is greater than 100 Hz, the number of left spheres 2 and right spheres 7 should be increased with the increase of the vibration frequency, and the size of the left spheres 2 and right spheres 7 should be reduced; if the vibration frequency range of the object to be damped is large, large-sized spheres and small-sized spheres can be mixed in a certain proportion according to the volume fraction.

[0018] The magnetic liquid 5 must be filled in the shell 1, and there is no cavity. The permanent magnet 4 is installed in the chamber between the left baffle 3 and the right baffle 6, forming a magnetic liquid damping element. The permanent magnet 4 can be rectangular or cylindrical, but its shape is the same as the shape of the inner cavity of the shell 1, and the size is smaller than the size of the inner cavity of the shell 1.

[0019] The left baffle 3 and the right baffle 7 are made of non-magnetic material and have small holes, the number of small holes is 2 to 100, and the maximum diameter of the small holes is smaller than the minimum diameter of the left spheres 2 and the right spheres 7. The small holes are used for the flow of the magnetic liquid 5 between the chambers, and prevent the left spheres 2 and the right spheres 7 from flowing out of the chamber.

[0020] The shell 1 is made of non-magnetic metal, and the inner cavity can be rectangular or cylindrical. The shell 1 must be completely sealed to prevent the magnetic liquid 5 from flowing out of the shell 1.

[0021] After the vibration is generated, since the equivalent densities of the permanent magnet 4 and the left and right spheres 2 and 7 are all greater than the density of the magnetic liquid 5, the permanent magnet 4 and all the left and right spheres 2 and 7 will move inside the magnetic liquid 5 under the influence of the viscosity and inertia force of the magnetic liquid 5, and will gather in the opposite direction of the vibration in the cavity. In this process, the permanent magnet 4 mainly generates liquid viscous damping force inside the magnetic liquid, while all the left and right spheres 2 and 7 not only generate liquid viscous damping force between the spheres and the magnetic liquid 5, but also generate particle collision damping due to the collision between the spheres and even the wall of the shell 1. The effect of the viscous damping force of the magnetic liquid 5 will weaken with the increase of the vibration frequency, while the effect of the particle collision damping will increase with the increase of the vibration frequency. Therefore, at low frequency, such as below 10 Hz, the energy consumption is mainly in the form of liquid damping between the magnetic liquid 5 and the permanent magnet 4. At the vibration frequency of 100 Hz, the left and right spheres 2 and 7 will collide with each other to generate particle collision damping. At this time, the energy consumption of the damper is mainly in the form of liquid damping between the magnetic liquid 5 and the permanent magnet 4, and part of the particle collision damping between the left and right spheres 2 and 7. If the frequency is several hundred or even thousands of hertz, the liquid damping between the magnetic liquid 5 and the permanent magnet 4 is very small, but the collision between the left and right spheres 2 and 7 will be very frequent, and the energy consumption is mainly in the form of particle collision damping.

[0022] The permanent magnet 4 can be made of neodymium iron boron or samarium cobalt permanent magnet material according to the temperature environment.

[0023] The magnetic liquid 5 is selected from kerosene-based, oil-based and ester-based magnetic liquids, and the viscosity should not be higher than 500 mPa.s. Similar magnetic fluids, such as magnetorheological fluid, cannot be used instead.

[0024] The above is only one embodiment of the present application and is not used to limit the present application. For those skilled in the art, the particle collision damper based on the suspension characteristics of the magnetic liquid can be modified according to the engineering conditions, including but not limited to the size of the damper, the volume ratio of each part of the sphere, the shape of the shell, the selection of materials, the installation position, etc. to adapt to the corresponding engineering.

Claims

1. A magnetic fluid passive dynamic vibration absorber utilizing particle collision damping, characterized in that: The damper includes: a housing (1), a left sphere (2), a left baffle (3), a permanent magnet (4), a magnetic fluid (5), a right baffle (6), and a right sphere (7); The left baffle (3) and the right baffle (6) are installed in the housing (1) to divide the housing (1) into three chambers and fill all the chambers with magnetic liquid (5). All left spheres (2) are installed into the left chamber between the housing (1) and the left baffle (3) to form a left particle collision damping assembly; all right spheres (7) are installed into the right chamber between the housing (1) and the right baffle (6) to form a right particle collision damping assembly. The permanent magnet (4) is installed in the cavity between the left baffle (3) and the right baffle (6). The permanent magnet (4) is suspended in the magnetic liquid (5) by utilizing the self-suspending effect of the permanent magnet (4) in the magnetic liquid (5) to form a magnetic liquid damping element.

2. The magnetic fluid passive dynamic vibration absorber utilizing particle collision damping according to claim 1, characterized in that: The left sphere (2) and the right sphere (7) are both made of non-magnetic metal with a density greater than that of the magnetic liquid (5); the number of the left sphere (2) and the right sphere (7) must be greater than 1, the diameter must be greater than 1 mm, and the maximum radius must not exceed 1 / 2 of the minimum size of the chamber in which they are located; the filling rate of the left sphere (2) in the left chamber between the shell (1) and the left baffle (3) is the same as the filling rate of the right sphere (7) in the right chamber between the shell (1) and the right baffle (6).

3. The magnetic fluid passive dynamic vibration absorber utilizing particle collision damping according to claim 1, characterized in that: The left baffle (3) and the right baffle (6) are both made of non-magnetic material and have small holes, the number of which is 2 to 100. The maximum diameter of the small holes is smaller than the minimum diameter of the left sphere (2) and the right sphere (7).

4. The magnetic fluid passive dynamic vibration absorber utilizing particle collision damping according to claim 1, characterized in that: The permanent magnet (4) has the same shape as the inner cavity of the shell (1), but its size is smaller than that of the inner cavity of the shell (1); the shell (1) is made of a non-magnetic material.

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