Magnetic fluid based particle collision passive damper

Abstract

The invention discloses a particle collision passive damper based on magnetic liquid, belonging to the field of vibration control. The invention successfully solves the problem that the existing particle collision damper cannot be applied to low-frequency vibration and weightless environment. The damper comprises a ball (1), a magnetic liquid (2), a spherical permanent magnet (3), a shell (4) and an elastic rubber shell (5). When external vibration occurs, the ball (1) and the spherical magnetic field source composed of the spherical permanent magnet (3) and the elastic rubber shell (5) move and collide in the shell (4), thereby generating fluid viscous damping and collision damping to absorb energy and achieve the purpose of vibration reduction. The damper is suitable for low-frequency vibration below 10 Hz and also has very good effect on high-frequency vibration above 100 Hz.

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] Particle collision damper is a passive damper that relies on the collision between particles to consume vibration energy under external vibration excitation. It has the advantages of high application vibration frequency, simple structure and long service life. However, the existing particle collision damper cannot solve the problem of medium and low frequency vibration due to the large friction between solid particles. The vibration suppression effect of 1000Hz below is not good, and the existing particle collision damping is basically ineffective for vibration below 100Hz or even lower frequency. Moreover, the current particle damper relies on gravity to make particles accumulate in the shell to generate friction. Once in a weightless environment, the particles will be in a free state, and cannot produce effective collision, resulting in failure.

[0003] In order to improve the collision probability between particles and the vibration reduction efficiency of particle collision damper, the method of injecting an appropriate amount of viscous liquid into the container or combining multiple particle collision dampers is usually used. For example, document 1 (patent application number CN106930425B) designs particles as a nested ball structure connected by springs, and uses viscous liquid to increase the collision probability between particles, but the proportion of air and particles inside the nested ball needs to be reasonably adjusted to ensure the suspension of the nested ball, which increases the processing difficulty of the particle damper, and the use of springs limits the service life of the damper. In addition, this design causes the equivalent density of the entire nested ball to be the same as the density of the viscous liquid, which cannot produce effective relative motion between the nested ball and the viscous liquid. Finally, this design is greatly affected by gravity. In space, due to the constraint of zero gravity, the entire nested ball and the internal particles are in a free state, and cannot produce effective mutual collision in the vibration environment. On the ground, gravity causes the particles inside the nested ball to completely accumulate together, and vibration energy can only overcome the solid friction between particles to make them move, so the vibration suppression effect is not good for low and medium frequency vibration. For example, document 2 (patent application number CN114962514B) suspends the ball in a cavity filled with magnetic liquid and with an elastic soft pad under the action of an external magnetic field. This invention can solve the problem that traditional magnetic liquid dampers cannot be applied to vibration environments above 100Hz. However, there is only one ball in this damper, 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 relatively large, the damping force of this damper cannot meet the requirements. In addition, the ball in this damper is only constrained by the suspension force of the magnetic liquid, and the suspension height is fixed, so it is not possible to adjust according to the vibration situation.

[0004] Therefore, it is urgent to redesign and improve the structure of the particle collision damping so that it can not only be applied in high-frequency vibration occasions, but also has very good effect in low-frequency and medium-frequency vibration occasions, and does not fail in weightless environment. SUMMARY

[0005] The technical problem to be solved by the present application is that the existing particle collision damper has large friction between solid particles, and has poor effect on vibration below 1000 Hz, and cannot be applied to low-frequency and medium-frequency vibration below 100 Hz. Moreover, in weightless environment, the particles will be in a free floating state and cannot produce effective collision, facing failure. The present application provides a particle collision passive damper based on magnetic liquid, which forms a particle collision damping by placing a large spherical permanent magnet and a plurality of small non-magnetic balls in a non-magnetic container filled with magnetic liquid. The spherical permanent magnet is suspended in the non-magnetic shell by using the self-suspension principle of the permanent magnet in the magnetic liquid, and the non-magnetic balls are expelled to the wall surface in the inner cavity of the shell by using the suspension force of the magnetic liquid. When the external vibration frequency is low, the spherical permanent magnet in the suspended state is very sensitive to the inertial force, and relative motion is generated between the inertial mass and the shell, and the vibration energy is consumed through liquid viscous damping. When the external vibration frequency is high, the small non-magnetic balls start to move and collide in the magnetic liquid, thereby generating liquid viscous damping and particle collision damping to consume vibration energy. Therefore, the damper has excellent vibration reduction performance for low-frequency vibration of only a few hertz or high-frequency vibration of thousands of hertz. In addition, the balls are affected by the suspension force of the magnetic liquid, and even in a weightless environment, they will not be in a free floating state, thereby causing failure.

[0006] The technical solution adopted by the present application to solve the technical problem is:

[0007] The damper comprises balls, a magnetic liquid, a spherical permanent magnet, a shell and an elastic rubber shell.

[0008] The spherical permanent magnet is installed in the elastic rubber shell to form a spherical magnetic field source. The balls and the spherical magnetic field source are installed in the shell to form a particle collision damping, and the shell is filled with the magnetic liquid.

[0009] The volume of the spherical permanent magnet is greater than 50% of the volume of the inner cavity of the shell, so as to prevent the size of the spherical permanent magnet from being too small and the suspension force of the magnetic liquid from being unable to drive the movement and collision of the balls. The inner diameter of the elastic rubber shell is the same as the outer diameter of the spherical permanent magnet, and the thickness of the elastic rubber shell is 0.5-10 mm, which is used to protect the spherical permanent magnet from being broken in the collision process. The elastic rubber shell is fixedly connected with the spherical permanent magnet, and the connection can be achieved by gluing.

[0010] The ball adopts non-permeable metal, and the equivalent density is greater than the density of the magnetic liquid. If the ball is solid, the metal density is greater than the density of the magnetic liquid; if the ball is hollow, the equivalent density of the ball is greater than the density of the magnetic liquid. The number of balls is greater than 1, that is, at least 2, to ensure that the balls collide with each other after vibration, and particle collision damping is generated. The sizes of all the balls can be the same or in the form of large and small combination. However, the minimum diameter must be greater than 1 mm, and the maximum radius cannot exceed 1 / 4 of the radius of the spherical permanent magnet. Preventing the size of the ball from being too small and the accumulation from being too dense can prevent the size of the ball from being too large, causing the movement space of the spherical permanent magnet in the shell to be too limited, affecting the particle collision damping force between the balls. The filling rate of the balls in the shell is 10% to 40%. The magnetic liquid in the shell must be full, and there is no cavity. If the volume of the spherical permanent magnet accounts for 50% of the volume of the cavity in the shell, and the filling rate of the balls is 40%, then the volume of the magnetic liquid is 10% of the volume of the cavity in the shell.

[0011] The shell is made of non-permeable metal, and the inner cavity is spherical. In order to facilitate installation, split type or end cap can be added on one side of the shell. The shell must be completely sealed to prevent the magnetic liquid from flowing out of the shell.

[0012] Compared with the prior art, the present application has the following advantages: (1) the self-suspension effect of the permanent magnet in the magnetic liquid makes the spherical permanent magnet suspended in the magnetic liquid, making the spherical permanent magnet very sensitive to inertial force, and can be applied to vibration with a frequency of 100 Hz or even 10 Hz; (2) the balls are made of non-permeable metal, forming particle collision damping, which can be applied to vibration with a frequency of several hundred or even several thousand hertz; (3) under the action of the external magnetic field formed by the spherical permanent magnet, the balls are subjected to the magnetic suspension force of the magnetic liquid, and will not drift due to weightlessness; (4) by placing the spherical permanent magnet and non-permeable balls in the shell filled with magnetic liquid, the device has both the low-frequency vibration suppression characteristics of the magnetic liquid damper and the high-frequency vibration suppression characteristics of the particle collision damping, expanding the application frequency band. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 Schematic diagram of the particle collision passive damper based on magnetic liquid;

[0014] In the figure: ball 1, magnetic liquid 2, spherical permanent magnet 3, shell 4, elastic rubber shell 5. DETAILED DESCRIPTION

[0015] The present application is further described with reference to the drawings as a specific embodiment:

[0016] The particle collision passive damper based on magnetic liquid, as shown in Figure 1The damper comprises a ball 1, a magnetic liquid 2, a spherical permanent magnet 3, a shell 4, and an elastic rubber shell 5.

[0017] The spherical permanent magnet 3 is installed in the elastic rubber shell 5 to form a spherical magnetic field source. The ball 1 and the spherical magnetic field source are both installed in the shell 4 to form a particle collision damping, and the shell is filled with the magnetic liquid 2.

[0018] The volume of the spherical permanent magnet 3 is greater than 50% of the volume of the inner cavity of the entire shell 4, so as to prevent the size of the spherical permanent magnet 3 from being too small and the suspension force of the magnetic liquid from being unable to drive the movement and collision of the ball 1. The inner diameter of the elastic rubber shell 5 is the same as the outer diameter of the spherical permanent magnet 3, and the thickness of the elastic rubber shell 5 is 0.5-10 mm, which is used to protect the spherical permanent magnet 3 from being broken in the process of collision. If the thickness is too large, the equivalent density of the spherical magnetic field source will be too small to generate large relative movement, and the magnetic field strength in the magnetic liquid will be too weak to be suspended. The elastic rubber shell 5 is fixedly connected with the spherical permanent magnet 3, and the connection can be achieved by gluing.

[0019] The ball 1 is made of a non-magnetic metal, and the equivalent density is greater than the density of the magnetic liquid 2. If the ball 1 is solid, the metal density is greater than the density of the magnetic liquid 2; if the ball 1 is hollow, the equivalent density of the ball 1 is greater than the density of the magnetic liquid 2. The number of the balls 1 is greater than 1, that is, at least two, so as to ensure that the balls 1 will collide with each other after vibration to generate particle collision damping. The sizes of all the balls 1 can be the same or can be arranged in large and small sizes. However, the minimum diameter must be greater than 1 mm, and the maximum radius cannot exceed 1 / 4 of the radius of the spherical permanent magnet 3. The size of the ball 1 is prevented from being too small to be too densely packed, and the size of the ball 1 is prevented from being too large to limit the movement space of the spherical permanent magnet 3 in the shell 4, thereby affecting the particle collision damping force between the balls 1. The filling rate of the balls 1 in the shell 4 is 10%-40%. The large-sized ball 1 is more sensitive to low-frequency vibration, and the small-sized ball 1 has greater damping force for high-frequency vibration. The balls 1 are selected according to the specific vibration condition. If the vibration frequency is single, when the vibration frequency of the object to be damped is only several tens of hertz, the number of the balls 1 should be reduced, and preferably controlled to be less than 10, and the size of the ball 1 should be increased. If the vibration frequency is single and greater than 100 Hz, the number of the balls 1 should be increased with the increase of the vibration frequency, and the size of the ball 1 should be reduced. If the vibration frequency range of the object to be damped is large, the large-sized ball 1 and the small-sized ball 1 can be mixed in a certain proportion according to the volume fraction.

[0020] The magnetic liquid 2 must fill the shell 4 without any cavity. If the volume of the spherical permanent magnet 3 is 50% of the volume of the inner cavity of the shell 4, and the filling rate of the ball 1 is 40%, then the volume of the magnetic liquid 2 is 10% of the volume of the inner cavity of the shell 4.

[0021] The shell 4 is made of non-magnetic metal, and the inner cavity is spherical. In order to facilitate installation, the shell can be split or an end cover can be added to one side of the shell. The shell 4 must be completely sealed to prevent the magnetic liquid from flowing out of the shell 4. The shell 4 can be cylindrical, cuboid or square.

[0022] After the vibration is generated, the equivalent density of the spherical permanent magnet 3 and the elastic rubber shell 5 forming the spherical magnetic field source and the ball 1 is greater than the density of the magnetic liquid 2. All the balls 1 and the spherical magnetic field source will move inside the magnetic liquid 2 and generate a displacement difference with the shell 4 under the influence of the viscosity and inertia force of the magnetic liquid 2, and will gather in the opposite direction of the vibration. In this process, not only will the liquid viscous damping force be generated between the balls 1 and the magnetic liquid 2, but also the balls 1 and the spherical magnetic field source will collide with each other and even with the wall of the shell 4, generating particle collision damping. The effect of the viscous damping force of the magnetic liquid 2 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 the liquid damping between the magnetic liquid 2 and the spherical magnetic field source and the ball 1. At 100 Hz, the balls 1 and the spherical magnetic field source will collide to some extent, generating particle collision damping. At this time, the energy consumption of the damper is mainly the liquid damping between the magnetic liquid 2 and the spherical magnetic field source and the ball 1, and part of the particle collision damping between the balls 1 and the spherical magnetic field source. If the frequency is several hundred or even thousands of hertz, the liquid damping between the magnetic liquid 2 and the spherical magnetic field source and the ball 1 is very small, but the collision between the spherical magnetic field source and the ball 1 will be very frequent, and the energy consumption is mainly the particle collision damping between the spherical magnetic field source and the ball 1.

[0023] The elastic rubber shell 5 can be made of rubber, silicone rubber, PE, ABS and other engineering plastics.

[0024] The spherical permanent magnet 3 can be made of neodymium iron boron or samarium cobalt permanent magnet material according to the temperature environment.

[0025] The magnetic liquid 2 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.

[0026] The above is only one embodiment of the present application and is not intended to limit the present application. Those skilled in the art can modify the particle collision damper based on the magnetic liquid suspension characteristics according to engineering conditions, including but not limited to the size of the damper, the volume ratio of each part of the ball, the shape of the shell, the material selection, the installation position, etc.

Claims

1. A magnetic fluid based particle impact passive damper, characterized by: The damper comprises a ball (1), a magnetic liquid (2), a spherical permanent magnet (3), a shell (4), and an elastic rubber shell (5); The spherical permanent magnet (3) is installed in the elastic rubber shell (5) to form a spherical magnetic field source. The ball (1) and the spherical magnetic field source are both installed in the shell (4) to form a particle collision damping; the magnetic liquid (2) is filled in the shell (4), and the spherical permanent magnet (3) is suspended in the magnetic liquid (2) by using the self-suspension effect of the spherical permanent magnet (3) in the magnetic liquid (2).

2. A magnetic fluid based particle impingement passive damper according to claim 1, characterized in that: The volume of the spherical permanent magnet (3) is greater than 50% of the volume of the inner cavity of the whole shell (4); the inner diameter of the elastic rubber shell (5) is the same as the outer diameter of the spherical permanent magnet (3), and the thickness of the elastic rubber shell (5) is 0.5-10 mm.

3. A magnetic fluid based particle impingement passive damper according to claim 1, characterized in that: The ball (1) is made of a non-magnetic metal and has a density greater than that of the magnetic liquid (2); the number of the balls (1) is greater than 1, the diameter of the balls (1) is greater than 1 mm, and the maximum radius cannot exceed 1 / 4 of the radius of the spherical permanent magnet (3).

4. A magnetic fluid based particle impingement passive damper according to claim 1, characterized in that: The shell (4) is made of a non-magnetic metal, and the inner cavity is spherical.

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