Magnetic liquid tilt angle sensor

Abstract

The application relates to a magnetic liquid horizontal inclination sensor, which belongs to the mechanical engineering field. The device comprises permanent magnets 1 (two pieces), magnetic liquid 2, coils 3 (two groups), side section inertial mass blocks 4 (two pieces), middle section inertial mass blocks 5, soft magnetic material plating 6, a cylindrical magnetic liquid container 7, a supporting rod 8, coil and permanent magnet supports 9 and their shell covers, and sealing devices 10. When the external inclination changes, the combined whole mass block will move and reach a balance at a new position, at which time the distribution of the magnetic liquid and the soft magnetic material on the whole mass block in the container changes, the inductance of the two groups of coils is no longer the same, an output is generated in the bridge circuit, and the output will increase along with the increase of the distance of the whole mass block deviating from the balance position, and the inclination change can be analyzed by monitoring the change of the voltage value. The application does not rely on liquid surface stability to output, has better anti-vibration capacity, and improves the stress condition and output magnitude of the configuration of the first-order buoyancy by means of the plating.

Description

Technical Field

[0001] This invention belongs to the field of mechanical engineering and relates to an inclination sensor, and more particularly to an inclination sensor using a magnetic fluid. Background Technology

[0002] In practical production and daily life, people often need to measure whether a plane is horizontal or vertical, or to measure the angle relative to the horizontal plane, requiring high precision and rapid digital response. Magnetic fluids, also known as magnetorheological fluids or ferrofluids, are relatively stable colloidal solutions composed of magnetic particles suspended in a matrix liquid and coated with surfactants. They possess the fluidity of liquids and can interact with external magnetic fields. Compared to traditional tilt sensors, magnetic fluid tilt sensors have many advantages, such as short response time and high sensitivity. This is because magnetic fluids are superparamagnetic, allowing them to quickly reflect changes in the magnetic field and thus sense changes in angle. They also offer superior vibration and shock resistance, as they can transmit position information without relying on mechanical force, making them superior to traditional tilt sensors based on mechanical pendulums in terms of shock resistance. The suspension characteristics of magnetic fluids also accelerate response, reduce wear, and extend lifespan. Furthermore, within a suitable measurement range, the output signal exhibits a good linear relationship with the change in horizontal tilt angle, and the inherent high and low temperature resistance of magnetic fluids allows the sensor to operate stably and accurately over a wide temperature range.

[0003] One existing magnetic liquid tilt sensor has a basic configuration consisting of a linear pipe, a primary coil wound around the outside of the pipe in the middle, and two secondary coils wound around the outside of the pipe on both sides. The pipe is half-filled with magnetic liquid. When the sensor is horizontal, the magnetic liquid is uniform in the pipe. However, when tilted along the axial direction, the amount of magnetic liquid inside the two coils differs, resulting in different output voltages from the two secondary coils. This type of sensor is affected by the liquid level and is difficult to adapt to interference such as vibration. Another type of magnetic liquid tilt sensor fills the pipe with magnetic liquid and uses the second-order buoyancy principle of the magnetic liquid to suspend a section of magnet. The movement of the magnet during tilting affects the output of the two coils. This type of sensor suffers from reduced fluidity due to particles in the magnetic liquid accumulating around the magnet, affecting the overall accuracy and sensitivity. Furthermore, since the magnet itself is a suspended mass, it is susceptible to interference from external ferromagnetic materials and magnetic fields. Summary of the Invention

[0004] To address the aforementioned problems, this invention presents a magnetic liquid tilt sensor. The technical solution is as follows:

[0005] A magnetic liquid horizontal tilt sensor is characterized in that the device can be divided into five parts, including a magnetic liquid measuring element, a differential coil group and measuring circuit, a coil and permanent magnet support, a horizontal base and a permanent magnet.

[0006] The magnetic fluid measuring element comprises a cylindrical container, an inertial mass, and a magnetic fluid. The cylindrical container has a high aspect ratio, such as an inner diameter of 4 mm and a length of 40 mm, and is housed within a coil and permanent magnet support. It contains the inertial mass and is filled with the magnetic fluid. A support rod, approximately 1 mm in diameter, is mounted on the axis of the cylindrical container. The inertial mass is made of a non-magnetic material and consists of three parts: a central section and two identical side sections. Both the central and side sections are cylindrical with radii slightly smaller than the cylindrical container, and have holes on their axes slightly larger than the support rod (1.05 to 1.1 times the rod's diameter). The length of the central section is approximately 1 / 3 of the length of the cylindrical container, and the total length of the mass is approximately 2 / 3 of the length of the cylindrical container; for example, with a radius of 3.3 mm, the central section is 13.2 mm long, and the side sections are 6.6 mm long. The surface of the central mass has a soft magnetic material coating of a certain thickness, such as a 0.03 mm thick iron-nickel alloy of grade 1J79. The coating may exclude the surface of the hole. The soft magnetic material has relatively low permeability, and its coating mitigates the nonlinearity of the overall magnetic field force to some extent, effectively improving the coil inductance.

[0007] The permanent magnets include two cylindrical permanent magnets, identical in size and shape, axially magnetized, with radii equal to the inner diameter of the magnetic liquid container of the magnetic liquid measuring element. The permanent magnets should be magnets with high remanence, such as N35 magnets. The permanent magnets generate a magnetic field along the axial direction of the cylindrical container, gradually increasing from the center to both sides. The combined magnetic force provides a restoring force when the inertial mass moves along the axial direction of the cylindrical container.

[0008] The differential coil assembly and measurement circuit include a first coil, a second coil, and a microcontroller. The first and second coils are wound around the outside of a cylindrical container and connected in series with the processor. The first and second coils have the same number of turns, and this number should not be lower than 400 turns for each. The measurement circuit is based on a bridge circuit, powered by AC input at a specific frequency, such as 1000Hz. The winding positions of the first and second coils are symmetrical about the center of the cylindrical container, and the corresponding number of turns has a certain spacing and distribution range. At the specified number of turns and power frequency, the spacing is approximately 5mm, and the winding range is 6.6mm for each coil. The measurement circuit based on the differential coil assembly can effectively detect the position of the overall mass block and provides good output under the specified coil distribution.

[0009] The coil and permanent magnet support serves as the external support for the cylindrical container in the magnetic liquid measuring element. It includes spaces for fixing the permanent magnets to both ends of the cylindrical container and spaces for winding coils one and two around the outside of the cylindrical container. At the location where the permanent magnets are fixed, the thickness of the support is much smaller than the size of the permanent magnets themselves, ensuring that the permanent magnets are as close as possible to the column of magnetic liquid. The support can be connected to a horizontal base for fixation on a plane.

[0010] Based on the first-order buoyancy property of magnetic fluids, a magnetically shielded outer shell, such as an iron shell, can be installed on the outside of the structure to reduce interference from external magnetic fields. If an outer shell is required, the length of the side mass block should be slightly reduced.

[0011] Compared with existing devices, this invention mainly utilizes the first-order buoyancy characteristics of magnetic fluids, and its beneficial effects are as follows:

[0012] 1. The measuring element in the sensor is filled with magnetic fluid, eliminating the need for measurement based on a stable liquid surface. This effectively avoids the impact of vibration and other interferences on the measurement, making it more adaptable to real-world environments. Even when subjected to severe shaking or impacts, the inertial mass, though leaving the working area, can return to the working area using the characteristic buoyancy of the magnetic fluid after the disturbance disappears. Compared to using second-order buoyancy, the first-order buoyancy principle employed in this invention allows the permanent magnet to be fixed externally, eliminating the need for magnetic materials in the inertial mass. This prevents breakage or magnetism loss due to collisions, resulting in better vibration resistance.

[0013] 2. At the same time, since the first-order buoyancy principle is adopted, the inertial mass block suspended in the magnetic fluid does not need to use magnetic materials, thus avoiding the effects of magnetic adhesion, such as increased friction, flow difficulties, and decreased sensitivity caused by the magnetic fluid accumulating around the inertial mass block.

[0014] 3. The soft magnetic material coating applied to the surface of the middle section of the inertial mass block, together with the outer permanent magnet, counteracts part of the first-order buoyancy of the magnetic fluid, resulting in better linearity of the overall magnetic force. Furthermore, it effectively enhances the coil inductance, significantly improving the circuit output signal compared to the case without the soft magnetic material coating, reaching an order of magnitude capable of effective reading and analysis. The soft magnetic material used here is iron-nickel alloy 1J79. Attached Figure Description

[0015] Figure 1 This is a cross-sectional view of the overall structure of the present invention;

[0016] Figure 2 This is a structural diagram of the coil and permanent magnet support of the present invention;

[0017] Figure 3 This is a schematic diagram illustrating the final stable output as a function of angle in the dynamic response of this invention;

[0018] Figure 4 This is a schematic diagram showing the displacement of the combined mass block as a function of angle in the dynamic response of the present invention. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings:

[0020] A cross-sectional view of a magnetic liquid tilt sensor is shown below. Figure 1 The device includes: two permanent magnets 1, a magnetic liquid 2, two sets of coils 3, two side inertial mass blocks 4, a middle inertial mass block 5 (including a soft magnetic material coating 6), a cylindrical magnetic liquid container 7, a support rod 8, a coil and permanent magnet bracket 9 with its shell cover and sealing device 10.

[0021] The relative permeability of the magnetic liquid 2 is about 1.2.

[0022] Both the side inertial mass block 4 and the middle inertial mass block 5 are cylindrical with a radius of 3.3 mm, a side section length of 6.6 mm, and a middle section length of 13.2 mm. They are both made of non-magnetic material, and the specific material selection is related to the range of the tilt sensor. The sensitivity between angle A and angle B is defined as... (mV / °), where U A U B These represent the voltage outputs of the sensor when angles A and B are stable. As the density of the selected material increases, the sensor's sensitivity gradually increases; however, at higher densities, the sensor's maximum range decreases slightly. The inner wall of the hole in the middle section inertial mass block 5 may not be coated with a soft magnetic material layer 6.

[0023] Two side mass blocks 4 are axially joined to both sides of the middle mass block 5 to form a combined integral mass block assembly. Magnetic liquid 2 and the integral mass block are placed along the support rod 8 into the cylindrical magnetic liquid container 7 and sealed. The sealed container is then placed inside the coil and permanent magnet support and secured.

[0024] The two permanent magnets 1 are placed and fixed at both ends of the coil and the permanent magnet support 9, respectively. The two sets of coils 3 are wound around the sides of the coil and the permanent magnet support, with a winding spacing of 3.3 mm and a winding range of 8 mm for each coil, and are connected to the microcontroller. The power supply of the bridge circuit of the processor is 3V, 1000Hz AC input.

[0025] By fixing the coil and permanent magnet support 9 to the plane to be measured, the horizontal tilt angle of the plane to be measured along the sensor axis can be measured. When there is no change in external tilt angle, i.e., when it is in a horizontal state, the overall inertial mass block moves to and balances in the middle of the container under the action of the first-order buoyancy of the magnetic fluid. At this time, the distribution of the magnetic fluid and the soft magnetic material on the combined overall mass block in the container is symmetrical, that is, the magnetic field distribution in the two sets of coils is consistent, so that the output of the bridge circuit read by the microcontroller is 0.

[0026] When there is a change in the tilt angle, the combined mass block will move under the action of gravity and reach equilibrium at a new position under the action of the first-order buoyancy of the magnetic fluid. At this time, the distribution of the magnetic fluid and the soft magnetic material on the mass block in the container is no longer symmetrical, that is, the two sets of coils are no longer the same, which causes the bridge circuit to generate an output, which will increase as the distance of the mass block from the equilibrium position increases. Therefore, the change in tilt angle can be analyzed by monitoring the change of this voltage value.

[0027] The output voltage value is related to the position of the overall mass block, and the correlation is basically linear; the position of the overall mass block when in equilibrium is related to its mass, i.e., the density of the material selected for the mass block. At the specified dimensions, when copper is chosen as the material for the mass block, such as... Figure 3 The magnetic liquid tilt sensor shown has a range of approximately ±50° and is effective within the range of 3° to 30° / -3° to -30°. Faced with sudden tilt angle changes, the circuit output can stabilize within 0.1 to 0.2 seconds. Figure 4 As shown. In Figure 4 In the image, from top to bottom, the responses are shown when the temperature suddenly changes from 0° to 3°, 4°, 5°, 6°, 7°, 8°, 9°, 10°, 12°, 15°, 18°, 20°, 23°, 30°, 40°, and 53°. Within the range of 3° to 30° / -3° to -30°, the sensor of this size has an average sensitivity of approximately 5.2 mV / °.

Claims

1. A magnetic liquid horizontal tilt sensor, characterized in that, The system includes a magnetic liquid measuring element, a differential coil assembly and measuring circuit, a coil and permanent magnet support, a horizontal base, and a permanent magnet. The magnetic liquid measuring element comprises a magnetic liquid container, a magnetic liquid, and a combined mass block. The magnetic liquid container is cylindrical with a support rod mounted on its axis inside. The combined mass block consists of side mass blocks and a middle mass block, both cylindrical with the same radius and a hole on its axis to accommodate the support rod. The outer surface of the middle mass block is coated with a soft magnetic material. The two side mass blocks are joined axially on both sides of the middle mass block to form a combined mass block. The combined mass block is placed into the magnetic liquid container along the support rod, the magnetic liquid is injected into the container, and it is sealed. The sealed magnetic liquid container is then placed inside the coil and permanent magnet support and fixed. The differential coil assembly includes two sets of coils, both located on the outer side of the middle of the cylindrical container, with the same material and number of turns, and symmetrically positioned.

2. A magnetic liquid horizontal tilt sensor as described in claim 1, characterized in that, The permanent magnet is a magnet of grade N35; two permanent magnets are respectively placed into the two ends of the coil and the permanent magnet support and fixed; two sets of coils are wound around the sides of the coil and the permanent magnet support and connected to the microcontroller. The coil and permanent magnet support are fixed on the plane to be measured.

3. A magnetic liquid horizontal tilt sensor as described in claim 1, characterized in that: The side mass block and the middle mass block are made of non-magnetic materials; the length of the middle mass block is twice the length of the side mass block, the length of the middle mass block is 1 / 3 of the length of the cylindrical container, and the total length of the overall mass block is 2 / 3 of the length of the cylindrical container.

Images