A magnetic fluid viscous damping characteristic testing device

Abstract

A magnetic fluid viscous damping characteristic testing device comprises a thin-walled barrel-shaped non-magnetic rotor, a constant gap, inner and outer pole shoe rings, upper and lower magnetic conductive ring pieces, a permanent magnetic ring, a magnetite, a liquid storage ring, a torque and speed sensor and other components. The device is characterized in that a constant gap is formed between the inner and outer pole shoe rings and they are concentrically positioned by the liquid storage ring; one of the inner and outer pole shoe rings is tightly connected to the magnetite, and the other forms an adjustable gap with the upper magnetic conductive ring piece; the permanent magnet is sandwiched between the upper and lower magnetic conductive ring pieces and can move up and down; the lower magnetic conductive ring piece is in contact with the magnetite; the magnetic fluid is injected into the constant gap and the liquid storage ring; the thin-walled barrel-shaped non-magnetic rotor is concentrically inserted into the constant gap, forms a shearing effect on the magnetic fluid after rotation, and converts its viscous damping characteristic into a shear torque to be measured by the torque and speed sensor; the device has the advantages that the test data only contains the viscous damping characteristic of the magnetic fluid, the magnetic fluid will not flow away when the magnetic field is low, and the accuracy is high.

Description

Technical field:

[0001] The present invention relates to a method and device for testing the viscous damping characteristics of magnetorheological fluid and magnetic liquid (hereinafter collectively referred to as magnetic fluid), in particular to a device for testing the viscous damping characteristics of magnetic fluid materials under the magnetization action of a magnetic field. The present invention is also suitable for the design of magnetorheological fluid damping vibration reduction and braking devices, and is also suitable for testing the viscosity characteristics of magnetic liquid or magnetic fluid materials. Background technology:

[0002] Magnetic fluid is a solid-liquid two-phase functional material with magnetic properties generated by stably dispersing magnetic particles in a certain carrier liquid through a surfactant. Its overall morphology, microstructure, and viscous damping properties are constrained and controlled by an external magnetic field. It has very broad application prospects in sealing, damping vibration reduction, electromagnetic filtration, high-quality audio, sensing, braking, etc. The study of the viscous damping properties of magnetic fluid in a magnetic field and at different temperatures is particularly important and is the basis for its application research. When the external magnetic field is lower than a certain critical value, the Brownian thermal motion of the magnetic particles in the magnetic fluid dominates, and chain ordering is not easy to occur. The viscous damping properties of the overall material are the same as those of ordinary fluids; however, under the action of an external strong magnetic field, the magnetic fluid exhibits a very strong magnetization viscosity-increasing property, and this magnetization viscosity-increasing property is related to the magnetization time. The magnetization viscosity-increasing property is beneficial to functions such as damping vibration reduction and braking, but it is harmful to functions such as sealing and high-quality audio. Therefore, whether it is magnetorheological fluid or magnetic fluid, it is necessary to measure its viscous damping characteristics at different temperatures or the viscosity characteristics changing with the external magnetic field intensity and time, so as to determine the working magnetic field of different magnetic fluid materials and provide a basis for the optimal design of sealing and damping vibration reduction devices.

[0003] Ordinary fluid viscosity test methods are not suitable for testing the magnetized viscous damping performance of magnetic fluids. On the one hand, it is not convenient to apply a strong magnetic field to the existing viscosity test equipment. Even if an external magnetic field is applied, some viscometers that rely on gravity cannot be used because the magnetic force is greater than the gravity. On the other hand, the ordinary method requires a large number of liquid samples each time.

[0004] The test method for the apparent viscosity of magnetic liquid given in Chinese patents CN1737531A and CN2802498Y adopts a magnetic liquid seal-like magnetic concentrating structure, and controls the strength of the external constrained magnetic field by increasing or decreasing the number of permanent magnet blocks in the magnetic concentrating structure. On the one hand, it is inconvenient to replace the permanent magnet blocks each time, and on the other hand, the change of the constrained magnetic field is discontinuous, and the critical working magnetic field cannot be accurately measured. At the same time, the patent does not provide a method for measuring the working magnetic field strength. The measurement method given in Chinese patent CN2099316U is an improvement on the traditional kinematic viscosity test method. Although the electromagnetic coil is used to achieve the continuous change of the external magnetic field, it is difficult to reach and maintain a high magnetic field strength for a long time, and each test requires a large amount of magnetic liquid sample and consumes more electric energy. In particular, the electromagnetic coil will generate a lot of heat when working, making it difficult to control the temperature of the sample being tested, especially difficult to achieve the measurement of low-temperature magnetization viscosity characteristics.

[0005] Chinese patents ZL201010290643.6 and ZL201310463664.7 provide a magnetic fluid magnetization viscosity test method and device using permanent magnets as magnetic sources and continuously adjustable confining magnetic fields, which are mainly composed of a magnetic fixed ring, a magnetic moving ring (or a magnetic rotor), a permanent magnet ring and a pole shoe ring, as well as a constant gap and an adjustable gap. The magnetic fluid is confined in a constant cylindrical gap between the magnetic fixed ring and the magnetic moving ring. On the one hand, the constant gap provides a continuously adjustable magnetic field to exert a continuously adjustable magnetization effect on the magnetic fluid material, and on the other hand, it also exerts a continuously adjustable shearing effect on the magnetic fluid. The speed regulating motor drives the magnetic moving ring (or magnetic rotor) to rotate through a torque and speed test device and a rotating shaft, so that the material sample in the constant gap is subjected to shearing, and the viscosity characteristics of the material sample are converted into shear force and measured by the torque sensor in the form of torque. Although this solves the problem of adjustable magnetic field strength and low-temperature viscosity testing, the disadvantage of this is that there is a strong magnetic force between the magnetic conductive moving ring (or magnetic conductive rotor) and the magnetic conductive fixed ring. Therefore, in order to maintain the concentric positioning and relative rotation between them, a set of rotating bearings must be set between them. In this way, the measured torque does not come entirely from the shear viscosity of the magnetic fluid, but also partly from the bearing resistance that supports the rotation of the magnetic conductive moving ring (or magnetic conductive rotor). In addition, the magnetic conductive rotor and its supporting bearings still have a large rotational inertia force. Therefore, before testing the viscosity characteristics of the magnetic fluid, the size of the rotation torque of the system without magnetic fluid must first be measured to facilitate subtraction from the viscosity test data of the magnetic fluid, resulting in a significant reduction in measurement accuracy. In addition, when there is no magnetic field constraint, the magnetic fluid will flow away from the constant gap. Summary of the invention:

[0006] The purpose of the patent of this invention is to provide a testing method and device which uses a permanent magnet as a magnetic source, the confining magnetic field is continuously adjustable from weak to strong, the magnetic fluid will not flow away when the magnetic field is low, and the test data only includes the shear viscosity resistance of the magnetic fluid, which can greatly improve the test accuracy and convenience.

[0007] The invention is realized as follows: a magnetic fluid viscous damping characteristic test device, mainly composed of an adjustable variable speed motor, a torque and speed sensor, an electromagnetic induction coil, a permanent magnet, a thin-walled barrel rotor, an upper magnetic conductive sheet, a lower magnetic conductive sheet, an inner pole shoe ring, an outer pole shoe ring, a magnetic conductor and other components, characterized in that: a constant gap is formed between the outer diameter of the inner pole shoe ring and the inner diameter of the outer pole shoe ring, and they are concentrically fixed and positioned by a liquid storage ring; and the liquid storage ring is made of non-magnetic materials such as titanium, aluminum, copper, stainless steel, and plastic; one of the inner and outer pole shoe rings is connected to the magnetic conductor. One is connected to the upper magnetic sheet, and the other forms an adjustable gap with the upper magnetic sheet; the permanent magnet is sandwiched between the upper and lower magnetic sheets to form a movable magnetic source, which can move up and down; the lower magnetic sheet is in contact with the magnetic body and can move up and down relatively; the magnetic fluid is injected into the constant gap and the liquid storage ring; the thin-walled barrel rotor is made of non-magnetic materials (such as titanium, aluminum, copper, stainless steel, plastic and other non-magnetic materials); its upper end is concentrically connected to the torque and speed sensor, the lower end is inserted into the constant gap and positioned concentrically with the constant gap, and the adjustable speed motor is concentrically connected to the torque and speed sensor. The electromagnetic induction coil is set below the liquid storage ring and connected to the fluxmeter.

[0008] During operation, the movable permanent magnetic source applies an adjustable magnetic field to the magnetic fluid in the constant gap through the upper magnetic conductive ring, the adjustable gap, the inner and outer pole shoe rings, the magnetizer, and the lower magnetic conductive ring; the adjustable gap size is adjusted by moving the movable magnetic source up and down, thereby adjusting the size of the constant gap magnetic field, and the change in the magnetic field is measured by the electromagnetic induction coil and the fluxmeter. When the upper magnetic conductive sheet of the movable magnetic source contacts the inner or outer pole shoe ring, the adjustable gap size becomes 0, the constant gap magnetic field reaches the maximum value, and the magnetic fluid in the liquid storage ring is sucked into the constant gap; when the movable magnetic source moves downward and forms a closed magnetic circuit between the upper and lower magnetic conductive rings and the magnetizer, the constant gap magnetic field reaches the minimum value, and the magnetic fluid in the constant gap flows into the liquid storage ring below it. The adjustable speed motor drives the thin-walled barrel rotor to rotate through the torque and speed test device, so that the material sample in the constant gap is sheared, and the viscous damping characteristics of the material sample are converted into shear force and measured by the torque sensor in the form of torque.

[0009] The advantage is that the shearing effect on the magnetic fluid in the constant gap is achieved through the relative rotation between the non-magnetic barrel-shaped thin-walled rotor and the fixed inner and outer pole shoe rings, rather than the relative rotation between the inner and outer pole shoe rings. This avoids the interference of the bearing resistance set between the inner and outer pole shoe rings on the test results; it can also greatly reduce the inertia of the rotor and further improve the test accuracy; in addition, when the constrained magnetic field is 0, the magnetic fluid will not flow away. Description of the drawings:

[0010] FIG1 is a schematic diagram of the structure of the magnetic fluid viscosity characteristic testing device in the intermediate state of Example 1.

[0011] FIG2 is a schematic diagram of the structure of the magnetic fluid viscosity characteristics test device in the state where the constant gap magnetic field tends to 0 in Example 1. FIG3 is a schematic diagram of the structure of the magnetic fluid viscosity characteristics test device in Example 1 when the constant gap magnetic field is at the maximum value. FIG4 is a schematic diagram of the principle structure of Example 1.

[0012] FIG5 is a schematic diagram of the structure of the magnetic fluid viscosity characteristics testing device with a high and low temperature box in Example 2

[0013] FIG6 is a schematic diagram of the structure of Example 3 in an intermediate state

[0014] FIG. 7 is a schematic diagram of the structure of a magnetic fluid viscosity characteristic testing device for adjusting the adjustable gap using a hydraulic element in Example 4.

[0015] Among them: 1-thin-wall barrel rotor, 2-magnetic fluid, 3-constant gap, 4-outer pole shoe ring, 5-adjustable gap, 6-electromagnetic induction coil, 7-upper magnetic conductive sheet, 8-permanent magnetic ring, 9-lower magnetic conductive sheet, 10-magnetic conductor, 11-leakage magnetic circuit, 12-magnetization circuit, 13-liquid storage ring, 14-inner pole shoe ring, 15-torque and speed sensor, 16-adjustable speed motor, 17-rotating shaft, 18-high and low temperature box, 19-hydraulic element, 20-base. Specific implementation method:

[0016] Embodiment 1 As shown in FIG1, the magnetic fluid viscous damping characteristic test device is mainly composed of: a thin-walled barrel rotor 1, a magnetic fluid 2, a constant gap 3, an outer pole shoe ring 4, an adjustable gap 5, an electromagnetic induction coil 6, an upper magnetic conductive ring sheet 7, a permanent magnetic ring 8, a lower magnetic conductive ring sheet 9, a magnetic conductor 10, a leakage magnetic circuit 11, a magnetizing circuit 12, a liquid storage ring 13, an inner pole shoe ring 14, a torque sensor 15, an adjustable speed motor 16 and other components. The special feature is that a constant gap 3 is formed between the outer diameter of the inner pole shoe ring 14 and the inner diameter of the outer pole shoe ring 4, and they are concentrically positioned by the liquid storage ring 13; and the liquid storage ring 13 is made of non-magnetic materials such as titanium, aluminum, copper, stainless steel, and plastic. The inner and outer pole shoe rings 14 and 4 are made of materials; one of them is connected to the magnetizer 10, and the other forms an adjustable gap 5 with the upper magnetic ring piece 7; the permanent magnet 8 is sandwiched between the upper and lower magnetic ring pieces 7 and 9 to form a movable magnetic source, and can move up and down; the lower magnetic ring piece 9 is in contact with the magnetizer 10 and is connected by threads, and can move up and down relatively; the magnetic fluid 2 is injected into the constant gap 3 and the liquid storage ring 13; the thin-walled barrel rotor 1 is made of non-magnetic titanium material, the upper end of which is concentrically connected to the torque and speed sensor 15, and the lower end is inserted into the middle of the constant gap 3, and is positioned concentrically with the constant gap 3, and the speed regulating motor 16 is concentrically connected to the torque and speed sensor 15. The electromagnetic induction coil 6 is arranged below the liquid storage ring 13 and is connected to the flux meter. When working, the permanent magnet 8 applies an adjustable magnetic field to the magnetic fluid in the constant gap 3 through the magnetizing circuit 12 composed of the upper magnetic conductive ring piece 7, the adjustable gap 5, the inner and outer pole shoe rings 14 and 4, the magnetizer 10, the lower magnetic conductive ring piece 9, etc.; the upper and lower magnetic conductive ring pieces 7 and the movable magnetic source composed of the pieces 9 and the permanent magnet 8 are driven to move up and down by the thread between the lower magnetic conductive ring piece 9 and the magnetizer 10 to adjust the size of the adjustable gap 5, thereby adjusting the size of the magnetic field in the constant gap 3, and measuring the change of the magnetic field through the electromagnetic induction coil 6 and the fluxmeter. When the upper magnetic conductive ring piece 7 of the movable magnetic source contacts the outer pole shoe ring 4, as shown in Figure 2, the size of the adjustable gap 5 becomes 0, and the magnetic field in the constant gap 3 reaches the maximum value; when the movable magnetic source moves downward and forms a closed magnetic circuit between the permanent magnet ring 8 and the upper and lower magnetic conductive ring pieces 7 and 9 and the magnetizer 10, as shown in Figure 3, the magnetic field in the constant gap 3 reaches the minimum value, and the magnetic fluid flows into the liquid storage ring 13 below it. The speed regulating motor 16 drives the non-magnetic thin-walled barrel rotor 1 to rotate through the torque and speed testing device 15, so that the magnetic fluid material sample 2 in the constant gap 3 is subjected to shearing action, and the viscous damping characteristics of the magnetic fluid material sample 2 are converted into shearing force and measured by the torque sensor 15 in the form of torque.

[0017] As shown in FIG. 4 , assuming that the wall thickness of the non-magnetic barrel type thin-walled rotor 1 can be neglected, the viscous damping characteristics of the final magnetic fluid 2 material sample are approximately given by the following formula:

[0018]

[0019] in

[0020] η is the magnetization viscous damping characteristic of the material sample (for magnetic liquid, it is the viscosity characteristic), δ=gl is the axial constant gap size, R is the radius of the non-magnetic barrel thin-walled rotor, h is the height of the axial constant gap cylindrical surface, ω is the angular velocity of the magnetic guide ring, M is the rotation torque of the magnetic guide ring, τ is the shear stress on the material sample, is the velocity gradient, F is the torsional force, and A is the constant gap cylindrical area.

[0021] The magnetic flux on the magnetic circuit 12 is measured by the induction coil and the flux meter connected thereto, and converted into the magnetic flux density passing through the material sample by a formula.

[0022]

[0023] B is the magnetic flux density of the constant axial gap 3, φ is the total magnetic flux on the magnetic circuit 12, N is the number of turns of the induction coil 6, φ t is the fluxmeter measurement value.

[0024] Embodiment 2 As shown in FIG5, the magnetic fluid viscous damping characteristic testing device described is different from Embodiments 1, 2 or 3 in that the testing device is entirely placed in a high and low temperature box 18 from the thin-walled barrel rotor 1 down, and the thin-walled barrel rotor 1 passes through the hole at the top of the high and low temperature box 18 through the rotating shaft 17, and is concentrically connected to the external torque and speed sensor 15. The device is mainly used to test its high and low temperature viscosity-temperature characteristics.

[0025] Example 3 is shown in Figure 6, and the magnetic fluid viscous damping characteristics testing device is shown in Figure 4. Compared with Example 1, the difference is that the outer pole shoe ring 4 is connected to the magnetic conductor 10, and an adjustable gap 5 is formed between the inner pole shoe ring 14 and the magnetic conductor 7.

[0026] Embodiment 4, as shown in FIG. 7 , the magnetic fluid viscous damping characteristic testing device is different from Embodiment 3 in that a hydraulic component 19 and a base 20 are provided under the lower magnetic ring piece, and the up and down relative movement between the lower magnetic ring piece 9 and the magnet 10 is driven by a hydraulic element 19 .

[0027] Keywords: magnetic fluid, viscous damping, characteristic viscosity test.

Claims

1. A magnetic fluid viscous damping characteristic testing device, mainly comprising: a thin-walled barrel rotor (1), an outer pole shoe ring (4), an electromagnetic induction coil (6), an upper magnetic conductive ring sheet (7), a permanent magnet ring (8), a lower magnetic conductive ring sheet (9), a magnetic conductor (10), a liquid storage ring (13), an inner pole shoe ring (14), a torque sensor (15), and an adjustable speed motor (16), wherein: A constant gap (3) is formed between the outer diameter of the inner pole shoe ring (14) and the inner diameter of the outer pole shoe ring (4), and they are coaxially fixed and positioned by a liquid storage ring (13); one of the inner pole shoe ring (14) and the outer pole shoe ring (4) is tightly connected to a magnetizer (10), and the other forms an adjustable gap (5) with an upper magnetic ring sheet (7); a permanent magnet ring (8) is sandwiched between the upper magnetic ring sheet (7) and the lower magnetic ring sheet (9) to form a movable magnetic source, which can be moved up and down; the lower magnetic ring sheet (9) is in contact with the magnetizer (10) and can be relatively moved up and down; a magnetic fluid (2) is injected into the constant gap (3) and the liquid storage ring (13); the upper end of the thin-walled barrel rotor (1) is coaxially connected to a torque sensor (15), and the lower end is inserted into the constant gap (3), and after rotation, a shearing effect is formed on the magnetic fluid (2); The shearing effect on the magnetic fluid (2) in the constant gap (3) is achieved through the relative rotation between the thin-walled barrel rotor (1) and the fixed inner pole shoe ring (14) and the outer pole shoe ring (4).

2. A magnetic fluid viscous damping characteristic testing device according to claim 1, characterized in that: The thin-walled barrel-shaped rotor (1) is made of non-magnetic material.

3. A magnetic fluid viscous damping characteristic testing device according to claim 1, characterized in that: The liquid storage ring (13) is made of non-magnetic material.

4. A magnetic fluid viscous damping characteristic testing device according to any one of claims 1, 2 or 3, characterized in that: The up-and-down relative movement between the lower magnetic conductive ring piece (9) and the magnetic conductive body (10) is driven by a thread.

5. A magnetic fluid viscous damping characteristic testing device according to any one of claims 1, 2 or 3, characterized in that: The up-and-down relative movement between the lower magnetic conductive ring piece (9) and the magnetic conductive body (10) is driven by a hydraulic element (19).

6. A magnetic fluid viscous damping characteristic testing device according to any one of claims 1, 2 or 3, characterized in that: An electromagnetic induction coil for testing magnetic flux density is closely attached to the bottom of the liquid storage ring (13).

7. The magnetic fluid viscous damping characteristic testing device according to any one of claims 1, 2 or 3, characterized in that: The entire portion below the thin-walled barrel-shaped rotor (1) is placed in a high-temperature box (18). The thin-walled barrel-shaped rotor (1) passes through a hole at the top of the high-temperature box (18) through a rotating shaft (17) and is concentrically connected to an external torque sensor (15) for testing the viscosity-temperature characteristics of the magnetic fluid.

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