WO2020238405A1

WO2020238405A1 - Gear-type magnetic fluid-based rotational speed sensor and manufacturing method thereof

Info

Publication number: WO2020238405A1
Application number: PCT/CN2020/082862
Authority: WO
Inventors: 李翔; 余鹏; 牛小东
Original assignee: 南方科技大学
Priority date: 2019-05-28
Filing date: 2020-04-02
Publication date: 2020-12-03
Also published as: CN110244075B; CN110244075A

Abstract

A gear-type magnetic fluid-based rotational speed sensor comprises a housing (10), a gear (20), a plurality of sensing electrodes (30), and a plurality of magnetic sources (40). The housing (10) has a cavity. The gear (20) is provided in the cavity and can rotate inside the cavity. The sensing electrode (30) is provided at an inner wall of the housing (10). There is a gap between the sensing electrode (30) and a tooth tip of the gear (20). The magnetic source (40) is provided at the inner wall of the housing (10), and is used to generate a magnetic field in the gap. A magnetic fluid is filled in the cavity. Since the gear-type magnetic fluid-based rotational speed sensor has a simple and compact structure and components thereof are independent from one another, maintenance and repair can be performed conveniently. Moreover, the sensor utilizes inherent characteristics of a magnetic fluid to enable rotational speed measurement of high speed rotation. Also provided is a manufacturing method of a gear-type magnetic fluid-based rotational speed sensor.

Description

Gear type magnetic fluid speed sensor and manufacturing method thereof

Technical field

The invention relates to the technical field of sensors, in particular to a gear type magnetic fluid rotational speed sensor and a manufacturing method thereof.

Background technique

The speed sensor is a sensor that converts the speed of a rotating object into electrical output. Commonly used speed sensors include photoelectric, capacitive, variable reluctance, and tachogenerator. In the prior art, the rotational speed sensor performs rotational speed measurement by directly transmitting the rotational state, and requires precision micromachining to manufacture the core components of the sensor, which requires a complex microstructure in production, and the machining cost is usually very high.

Therefore, the existing technology needs to be improved and developed.

Summary of the invention

The technical problem to be solved by the present invention is to provide a gear type magnetic fluid rotational speed sensor and a manufacturing method thereof in view of the above-mentioned defects of the prior art, aiming to solve the problem of high cost caused by the complicated microstructure of the rotational speed sensor in the prior art .

The technical solutions adopted by the present invention to solve the technical problems are as follows:

A gear type magnetic fluid rotational speed sensor, which comprises: a housing, a gear, a number of sensing electrodes, and a number of magnetic sources; the housing has a cavity, and the gear is arranged in the cavity and can be located in the cavity. The cavity rotates; the induction electrode is arranged on the inner wall of the housing, there is a gap between the induction electrode and the tooth end of the gear, and the magnetic source is arranged on the inner wall of the housing and is used in the The gap is provided with a magnetic field; the cavity is filled with magnetic fluid.

The gear type magnetic fluid rotational speed sensor, wherein the magnetic fluid includes a plurality of non-magnetic conductive particles, and the plurality of non-magnetic conductive particles are used for self-assembly in the magnetic field to connect the sensing electrode and the At the tooth end of the gear, the width of the gap is 10-10000 μm.

The gear type magnetic fluid rotational speed sensor, wherein the non-magnetic conductive particles are nanometer copper powder, nanometer aluminum powder, nanometer silver powder, nanometer copper wire, nanometer aluminum wire, nanometer silver wire, fuller One or more of olefins.

In the gear type magnetic fluid rotational speed sensor, wherein the intensity of the magnetic field is greater than 0.1 Tesla.

In the gear type magnetic fluid rotational speed sensor, a magnetic fluid level probe for detecting the magnetic fluid level is provided on the housing.

In the gear type magnetic fluid speed sensor, the gear is a bevel gear.

In the gear type magnetic fluid rotational speed sensor, one end of the gear is rotatably connected to the inner wall of the housing through a bearing, the other end of the gear is provided with a gear column, the housing is provided with a column hole, and the The gear column passes through the column hole to the outside of the cavity.

In the gear type magnetic fluid speed sensor, a sealing magnet is arranged on the inner wall of the housing, and the sealing magnet surrounds the gear column.

In the gear type magnetic fluid rotational speed sensor, the gear and the gear column are non-magnetic and conductive.

A manufacturing method of a gear type magnetic fluid rotational speed sensor based on any one of the above, wherein it comprises the steps:

Preparation of magnetic fluid based on non-magnetic conductive particles;

Set the position of the sensing electrode, the number of teeth of the gear, the width of the gap, and the strength of the magnetic field according to the speed of the gear.

Beneficial effects: The gear type magnetic fluid rotational speed sensor of the present invention has a simple and compact structure, and each part is relatively independent, which is convenient for maintenance and repair. And using the characteristics of the magnetic fluid itself, it can be adapted to the speed measurement under high-speed rotating conditions.

Description of the drawings

Figure 1 is a partial cross-sectional view of the gear-type magnetic fluid rotational speed sensor of the present invention.

Figure 2 is a cross-sectional view of the gear-type magnetic fluid rotational speed sensor of the present invention.

Fig. 3 is an enlarged view of A in Fig. 2.

Fig. 4 is a schematic diagram of the structure of the gear-type magnetic fluid rotational speed sensor of the present invention.

Figure 5 is a schematic diagram of the structure of the gear and the gear column of the present invention.

Figure 6 is a schematic diagram of the structure of the cover in the present invention.

FIG. 7 is a schematic diagram of the structure of the sensing electrode, the magnetic source and the output terminal in the present invention.

Fig. 8 is a schematic diagram of the structure of non-magnetic conductive particles in the present invention without an external magnetic field.

Fig. 9 is a schematic diagram of the structure of non-magnetic conductive particles in a vertical magnetic field in the present invention.

Figure 10 is a photograph of non-magnetic conductive particles in a vertical magnetic field in the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer and clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, but not to limit the present invention.

Please refer to FIGS. 1 to 9 at the same time. The present invention provides some preferred embodiments of a gear-type magnetic fluid rotational speed sensor.

As shown in Figures 1 and 2, the gear-type magnetic fluid rotational speed sensor of the present invention includes: a housing 10, a gear 20, a number of sensing electrodes 30 and a number of magnetic sources 40; the housing 10 has a cavity, the The gear 20 is arranged in the cavity and can rotate in the cavity; the sensing electrode 30 is arranged on the inner wall of the housing 10, and there is a gap between the sensing electrode 30 and the tooth end of the gear 20, The magnetic source 40 is arranged on the inner wall of the housing 10 and used to provide a magnetic field at the gap.

Specifically, the inner wall of the housing 10 is provided with a sensing electrode mounting hole, the sensing electrode 30 is installed in the sensing electrode mounting hole, and the sensing head of the sensing electrode 30 extends out of the sensing electrode mounting hole, that is, the sensing electrode 30 The sensor head extends into the cavity. The cavity is filled with magnetic fluid (not shown in the figure).

The magnetic fluid includes a plurality of non-magnetic conductive particles, and the plurality of non-magnetic conductive particles are used for self-assembly in the magnetic field to connect the sensing electrode 30 and the tooth end of the gear 20.

It is worth noting that the rotation speed of the gear 20 needs to be measured in the present invention. Because the non-magnetic conductive particles in the magnetic fluid are under the action of a certain magnetic field, they will self-assemble along the direction of the magnetic line of induction to form a chain structure, that is, the non-magnetic conductive particles are arranged in sequence and connected into chains. The gear 20 includes a wheel body 22 and a number of teeth 23 arranged on the wheel body 22. There are recesses between adjacent teeth 23. Here, the tooth end of the gear 20 specifically refers to the teeth 23 away from the center of the gear 20 (wheel body 22). One end.

When the gear 20 rotates and the teeth are opposite to the induction electrode 30, the gap between the tooth end and the induction electrode 30 is small, and the two ends of the chain structure formed by connecting non-magnetic conductive particles are connected to the induction motor and the tooth of the gear 20, respectively. Terminal to realize the conduction between the sensing electrode 30 and the tooth end of the gear 20. When the gear 20 rotates and the teeth 23 are not opposed to the sensing electrode 30 (that is, the recess is opposed to the sensing electrode 30), the sensing electrode 30 is far away from the gear 20, and the two ends of the chain structure formed by connecting non-magnetic conductive particles cannot Connected to the sensing electrode 30 and the gear 20, of course, the sensing electrode 30 and the gear 20 cannot be connected (that is, the sensing electrode 30 is disconnected from the gear 20). The rotation speed of the gear 20 can be calculated by the switching speed of the sensing electrode 30 and the gear 20.

Magnetic fluid is a stable solution composed of nano-scale magnetic particles (MPs, about 10nm in diameter), a base carrier liquid, and a dispersant. Compared with general fluids, magnetic fluids not only have the fluidity of liquids, but also have magnetization properties. Using the magnetization characteristics of magnetic fluids, the movement of magnetic fluids can be controlled by an external magnetic field.

Magnetic fluids containing non-magnetic particles are called inverse magnetic fluids. This is because the size of the non-magnetic particles is much larger than the nano-scale magnetic particles in the magnetic fluid. The interaction between the non-magnetic particles and the magnetic fluid can be regarded as the fluid-solid coupling between the solid particles and the Newtonian fluid. Please refer to Figure 8-10 at the same time. When there is an external magnetic field, the non-magnetic particles are reversely magnetized by the nearby magnetic fluid and exhibit anisotropy. When a large number of non-magnetic particles are placed in the magnetic fluid, the non-magnetic particles have a dipole force due to the magnetic moment. This anisotropy makes the non-magnetic particles assemble into a chain structure in the direction of the magnetic field. After being assembled into a chain structure, the non-magnetic particles have lower energy and are more stable.

In addition, the temperature-sensitive insulating magnetic fluid is used in the present invention. Commonly used temperature-sensitive insulating magnetic fluids include water-based, oil-based, ester-based and fluoroether oil and other magnetic fluids. Specifically, the base carrier fluid can be water, motor oil, or hydroxyl oil. , Fluoroether oil, etc., the dispersant can be styrene or phosphate buffer, used to maintain the uniform mixing state of non-magnetic conductive particles. Since the temperature-sensitive insulating magnetic fluid generally has good thermal conductivity, the gear-type magnetic fluid speed sensor has better heat dissipation performance.

For the convenience of calculation, let the number of teeth of the gear 20 be n, and the rotation speed of the gear 20 can be calculated in multiple ways: First, when a sensing electrode 30 is set, the time for detecting that the sensing electrode 30 and the gear 20 are connected and disconnected n times is t ₁ Second, the rotation speed of the gear 20 is n/t ₁ revolution/sec. Secondly, when a sensing electrode 30 is provided, the time for detecting that the sensing electrode 30 and the gear 20 are adjacent to each other is t ₂ seconds, and the rotation speed of the gear 20 is 1/t ₂ revolutions/sec. Third, when two sensing electrodes 30 are provided, the central angle of the two sensing electrodes 30 is α, and the time for detecting a certain tooth end to turn over the two sensing electrodes 30 in turn is t ₃ seconds, then the gear 20 The rotation speed is t ₃ ×360°/α rev/sec.

Please refer to FIGS. 1, 2 and 7 at the same time. In a preferred embodiment of the present invention, one sensing electrode 30 and one magnetic source 40 are used, and the magnetic source 40 is a permanent magnet or an electromagnet. In order to better provide a magnetic field at the gap, the tooth ends of the magnetic source 40 and the gear 20 are respectively located on both sides of the sensing electrode 30, that is to say, the magnetic source 40 is also located in the sensing electrode mounting hole. The connecting lines of the ends are parallel to the magnetic field lines, so that the non-magnetic conductive particles are distributed along the magnetic field lines to connect the sensing electrode 30 and the tooth end of the gear 20.

A number of output terminals 60 are provided on the housing 10, and the output terminals 60 are connected to the sensing electrode 30 for outputting current signals of the sensing electrode 30. In the preferred embodiment of the present invention, one output terminal 60 is used.

In a preferred embodiment of the present invention, the non-magnetic conductive particles are nanometer copper powder, nanometer aluminum powder, nanometer silver powder, nanometer copper wire, nanometer aluminum wire, nanometer silver wire, fullerene One or more of. Specifically, of course, the non-magnetic conductive particles are not limited to the above materials, and the non-magnetic of the non-magnetic conductive particles herein refers to the non-magnetic relative to substances containing iron, cobalt, nickel and the like.

In a preferred embodiment of the present invention, as shown in FIG. 3, the width δ of the gap is 10-10000 μm. Preferably, the width δ of the gap is 50-2000 μm. Specifically, the width δ of the gap needs to be set according to the requirements of rotational speed measurement. Since the length of the chain structure formed by the non-magnetic conductive particles is related to time, the length of the chain structure increases with the passage of time. Of course, the chain structure also It will break, the connection and breaking of the chain structure is a reversible process. After a certain period of time, the connection and breaking of the chain structure reach equilibrium. Therefore, during the time when the tooth end of the gear 20 is opposite to the sensing electrode 30, the chain structure needs to be connected to a certain length, which is enough to exceed the width δ of the gap to connect the sensing electrode 30 and the tooth end of the gear 20. Of course, the higher the speed to be measured, the smaller the width δ of the gap; when the lower the speed to be measured, the width δ of the gap can be increased. Of course, the width δ of the gap also needs to be determined according to the induction time. When the induction is fast, the width δ of the gap is smaller. When the induction is not required, the width δ of the gap can be increased.

In a preferred embodiment of the present invention, the intensity of the magnetic field is greater than 0.1 Tesla. Specifically, for the water-based magnetic fluid, the magnetic field strength of the permanent magnet should be greater than 0.2T (Tesla), and for the oil-based magnetic fluid, the magnetic field strength of the permanent magnet should be greater than 0.1T (Tesla). The strength of the magnetic field can control the length of the chain structure, the stronger the magnetic field, the longer the chain structure; the weaker the magnetic field, the shorter the length of the chain structure. The intensity of the magnetic field can be set according to the speed measurement requirements.

In a preferred embodiment of the present invention, please refer to Figures 1 to 4 at the same time. In order to ensure that the amount of magnetic fluid is sufficient for testing, a magnetic fluid level probe for detecting the level of the magnetic fluid is provided on the housing 10 Needle 50. Specifically, a probe mounting hole 14 may be provided on the housing 10, and the magnetic fluid level probe 50 is provided in the probe mounting hole 14. One end of the magnetic fluid level probe 50 extends into the cavity, and the other end protrudes out of the housing 10. When the magnetic fluid is insufficient, the magnetic fluid level probe 50 is removed, and the magnetic fluid is supplemented through the probe mounting hole 14.

The setting position of the probe mounting hole 14 can be adjusted as required. In the preferred embodiment of the present invention, the gear 20 rotates in a vertical plane, the sensing electrode 30 is arranged on the top of the inner wall of the housing 10, and the probe mounting hole 14 is arranged at On the upper surface of the housing 10, as long as the magnetic fluid is insufficient, air will appear at the top of the cavity. When the magnetic fluid is lower than a certain height, the magnetic fluid level probe 50 will detect it.

In a preferred embodiment of the present invention, please refer to FIGS. 2 and 5 at the same time. The gear 20 is a bevel gear. Specifically, the gear 20 may adopt a cylindrical gear or a bevel gear. The radial force component of the cylindrical gear is too large. Preferably, a bevel gear is used, which is suitable for the measurement of the gear 20 with a higher speed.

In a preferred embodiment of the present invention, please refer to Figures 2, 5 and 6 at the same time. One end of the gear 20 is rotatably connected to the inner wall of the housing 10 through a bearing 70, and the other end of the gear 20 is provided There is a gear column 21, a column hole 16 is provided on the housing 10, and the gear column 21 passes through the column hole 16 to the outside of the cavity. Specifically, when a bevel gear is used, the small end of the bevel gear is rotatably connected to the inner wall of the housing 10 through the bearing 70, and the large end is connected to the gear column 21. The bearing 70 can prevent the gear 20 from sliding in the axial direction, and avoid friction between the gear 20 and the housing 10 due to contact.

In a preferred embodiment of the present invention, of course, the gear 20 can also be sleeved on the gear column 21. One end of the gear column 21 is rotatably connected to the inner wall of the housing 10 through a bearing 70, and the other end passes through From the column hole 16 to the outside of the cavity, adjusting the position of the gear 20 on the gear column 21 can change the width δ of the gap.

The housing 10 includes a base 11 and a cover 12 connected to the base 11; a flange 13 is provided on the base 11, and the flange 13 is provided with a screw hole through which screws can pass and fix the sensor. The column hole 16 is provided on the cover 12.

In a preferred embodiment of the present invention, neither the gear 20 nor the gear column 21 is magnetic and conductive. Specifically, the gear 20 or the gear column 21 is made of a non-magnetic conductive material, or a conductive coating is plated on a non-magnetic non-conductive material. Gear teeth can be manufactured by casting, gear shaping and welding. The gear column 21 is used as the input end. When the gear column 21 drives the gear 20 to rotate, the gear 20 and the sensing electrode 30 are on and off, and the rotation speed of the gear 20 is calculated by the number of on and off. The tooth end of the gear 20 is flat, which facilitates the connection with the sensing electrode 30 through non-magnetic conductive particles.

In a preferred embodiment of the present invention, please refer to FIGS. 1, 2 and 6 at the same time. In order to avoid the leakage of magnetic fluid, a sealing magnet 80 is provided on the inner wall of the housing 10, and the sealing magnet 80 surrounds the The gear column 21, that is, the sealing magnet 80 is arranged on the edge of the column hole 16. Furthermore, a groove 15 is provided on the inner wall of the housing 10, specifically, the groove 15 is provided on the cover 12; the sealing magnet 80 is located in the groove 15, and the distance between the sealing magnet 80 and the opening of the groove 15 is 0.02 To 0.2mm. The sealed magnet 80 utilizes the rheology of the magnetic fluid, so that the magnetic fluid forms a solid-phase sealing film at the seal to isolate the external environment and prevent internal leakage of the sensor. The sealed magnet adopts permanent magnets, and the commonly used permanent magnets include neodymium iron boron permanent magnets and ferrite permanent magnets.

The present invention has the following advantages: (1) The gear type magnetic fluid rotational speed sensor of the present invention has a simple and compact structure, and each part is relatively independent, which is convenient for maintenance and repair; (2) The gear type magnetic fluid rotational speed sensor of the present invention has good interchangeability. , It can realize modularization, serialization and rapid production; (3) The gear type magnetic fluid speed sensor of the present invention has no special requirements on the working environment and can adapt to various special environments; (4) The present invention uses the characteristics of magnetic fluid itself to Adapt to speed measurement under high-speed rotation conditions. (5) This sensor has no special requirements on the length of the sensing area, and it can be made very small. Under the conditions allowed by technology, the gap of the sensor cavity can be less than 50μm.

The present invention also provides a manufacturing method of a gear type magnetic fluid rotational speed sensor based on any one of the above, including the following steps:

Step S100, preparing a magnetic fluid according to the non-magnetic conductive particles.

Specifically, according to the physical and chemical properties of non-magnetic micro-conductive particles, magnetic fluids with different base carrier fluids are selected for suspension and dissolution. Because temperature-sensitive insulating magnetic fluids have good heat dissipation properties, temperature-sensitive insulating magnetic fluids are generally used, and temperature-sensitive insulating magnetic fluids are commonly used. Magnetic fluids include water-based, oil-based, ester-based, and fluoroether oil. The base carrier fluid can be prepared with water, motor oil, hydroxy oil and other solvents. After preparation, experimental measurement is required, and self-assembly is required under the designed magnetic field strength The self-assembly efficiency of chain length L reaches 80%.

When selecting, consider the experimental fluid viscosity, pressure and economy to choose magnetic fluids with different magnetization strengths. The higher the magnetization, the more obvious the solid characteristics of the magnetic fluid, and the efficiency of self-assembly will be greatly improved. At the same time, the resistance caused by the magnetic viscosity will also increase. It will greatly increase, and it is necessary to comprehensively consider the factors of resistance caused by magnetic viscosity and self-assembly efficiency during production.

Step S200, setting the position of the sensing electrode 30, the number of teeth of the gear 20, the width δ of the gap, and the intensity of the magnetic field according to the rotation speed of the gear 20.

Specifically, S200 includes the following steps:

In step S210, the number of teeth of the sensing electrode 30 and the gear 20 is made according to the conditions of the speed measurement input terminal (for example, whether it is magnetic, what is the shaft diameter condition) and the speed measurement requirements.

Specifically, the teeth of the gear 20 should adopt a symmetrical design, and the shape can be an involute tooth profile, a rectangular tooth profile, a trapezoidal tooth profile, etc. In special cases, an asymmetric design or an incomplete tooth design can also be used.

Step S220: Make the size of the cavity according to the self-assembly experiment in S100, and make the modulus of the gear 20, the width δ of the gap, and the strength of the magnetic field according to the installation position of the sensing electrode 30 and the rotation speed measurement requirements, and further determine the gear 20 The diameter and the model of the bearing 70 are selected to determine the size of the housing 10 according to the width δ of the gap.

The width δ of the gap should be determined by the self-assembly experiment in step S100, and the factor of rotation should also be considered, so the width δ of the gap should be slightly smaller than the length L of the self-assembled chain structure measured by the experiment. The commonly used value range is L /4<δ<L.

In step S230, the magnetic fluid level probe 50 is manufactured according to the installation position of the sensing electrode 30 and the width δ of the gap.

The magnetic fluid level probe 50 needs to be made of non-magnetic and non-conductive materials, its bottom should be lower than the sensing electrode 30, and its allowable scale should be higher than the tooth end of the gear 20, and the sensor should be static when detecting the position of the magnetic fluid level A period of time to prevent the magnetic fluid splashing caused by rotation from affecting the liquid level position detection.

Step S240. The housing 10 is manufactured according to the installation environment and location dimensions. The housing 10 includes a base 11 and a cover 12 connected to the base 11. The sensor base 11 is sequentially installed with sensing electrodes 30, magnetic sources 40, and bearings. 70. Gear 20, magnetic fluid level probe 50, and check whether there is mutual interference.

Step S250: Fabricate the cover 12 according to the size of the sensor base 11, and make a groove 15 on the cover 12 for installing permanent magnets, and pass the prepared magnetic fluid mixed with non-magnetic conductive particles through the magnetic fluid level probe The mounting hole of 50 is filled into the speed measuring cavity and tested its anti-leakage characteristics.

There needs to be a gap of 0.02 to 0.2 mm between the permanent magnet and the opening of the groove 15.

Step S260, after the initial assembly, a power-on test experiment is required to ensure the effectiveness of the assembly.

In summary, the present invention provides a gear type magnetic fluid rotational speed sensor and a manufacturing method thereof. The gear type magnetic fluid rotational speed sensor includes: a housing, a gear, a plurality of sensing electrodes, and a plurality of magnetic sources; the housing The body has a cavity, and the gear is arranged in the cavity and can rotate in the cavity; the sensing electrode is arranged on the inner wall of the housing, and there is between the sensing electrode and the tooth end of the gear The magnetic source is arranged on the inner wall of the housing and used to provide a magnetic field at the gap; the cavity is filled with a magnetic fluid, and the magnetic fluid includes a plurality of non-magnetic conductive particles, and the plurality of non-magnetic conductive particles The magnetic conductive particles are used for self-assembly in the magnetic field to connect the sensing electrode and the tooth end of the gear. Because the gear-type magnetic fluid rotational speed sensor of the present invention has a simple and compact structure, and each part is relatively independent, it is convenient for maintenance and repair. And using the characteristics of the magnetic fluid itself, it can be adapted to the speed measurement under high-speed rotating conditions.

It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or changes can be made based on the above description, and all these improvements and changes should fall within the protection scope of the appended claims of the present invention.

Claims

A gear type magnetic fluid rotational speed sensor, characterized in that it comprises: a housing, a gear, a number of sensing electrodes, and a number of magnetic sources; the housing has a cavity, and the gear is arranged in the cavity and can be Rotate in the cavity; the induction electrode is arranged on the inner wall of the housing, there is a gap between the induction electrode and the tooth end of the gear, and the magnetic source is arranged on the inner wall of the housing and is used for A magnetic field is provided at the gap; the cavity is filled with magnetic fluid.
The gear type magnetic fluid speed sensor according to claim 1, wherein the magnetic fluid includes a plurality of non-magnetic conductive particles, and the plurality of non-magnetic conductive particles are used for self-assembly in the magnetic field to connect the The width of the gap between the induction electrode and the tooth end of the gear is 10-10000 μm.
The gear type magnetic fluid rotational speed sensor according to claim 2, wherein the non-magnetic conductive particles are nanometer copper powder, nanometer aluminum powder, nanometer silver powder, nanometer copper wire, nanometer aluminum wire, nanometer One or more of grade silver wire and fullerene.
The gear type magnetic fluid rotational speed sensor according to claim 1, wherein the intensity of the magnetic field is greater than 0.1 Tesla.
The gear-type magnetic fluid rotational speed sensor according to claim 1, wherein a magnetic fluid level probe for detecting the level of the magnetic fluid is provided on the housing.
The gear-type magnetic fluid rotational speed sensor of claim 1, wherein the gear is a bevel gear.
The gear type magnetic fluid speed sensor according to claim 1, wherein one end of the gear is rotatably connected to the inner wall of the housing through a bearing, and the other end of the gear is provided with a gear column, and the housing is A column hole is provided, and the gear column passes through the column hole to the outside of the cavity.
The gear type magnetic fluid rotational speed sensor according to claim 7, wherein a sealing magnet is provided on the inner wall of the housing, and the sealing magnet surrounds the gear column.
The gear-type magnetic fluid rotational speed sensor of claim 7, wherein the gear and the gear column are non-magnetic and conductive.
A manufacturing method of a gear type magnetic fluid rotational speed sensor according to any one of claims 1-9, characterized in that it comprises the steps:

Preparation of magnetic fluid based on non-magnetic conductive particles;

Set the position of the sensing electrode, the number of teeth of the gear, the width of the gap, and the strength of the magnetic field according to the speed of the gear.