CN209946192U - Non-contact magnetic fluid rotating speed measuring device - Google Patents

Abstract

The utility model discloses a non-contact magnetofluid rotating speed measuring device; the device comprises a speed measuring shaft and a speed measuring sleeve which are coaxially arranged, wherein the speed measuring sleeve is sleeved on the speed measuring shaft, and a gap is formed between the speed measuring shafts; the speed measuring sleeve is provided with a speed measuring cavity, a conductive coating, an induction electrode and a magnetic fluid are arranged in the speed measuring cavity, and the conductive coating and the induction electrode are externally connected with a current detection circuit and are coaxially arranged with a speed measuring shaft; a speed measuring magnet is fixed on the speed measuring shaft, and the speed measuring magnet and the induction electrode are arranged in the same radial direction; the speed measuring shaft is used for connecting the rotating speed output end of the object to be measured and synchronously driving the speed measuring magnet to rotate. Therefore, the speed measuring load of the speed measuring shaft is effectively reduced, and the safety, the stability and the application range of the speed measuring shaft are improved.

Description

A non-contact magnetic fluid speed measuring device

technical field

The utility model relates to the field of rotational speed measuring devices, in particular to a non-contact magnetic fluid rotational speed measuring device.

Background technique

A rotational speed measuring device is a measuring device that converts the rotational speed of a rotating object into an electrical output. Most of the existing rotational speed measuring devices are indirect measuring devices, and common rotational speed measuring devices can be manufactured by methods such as mechanical machining, electromagnetic machining and hybrid machining. According to the different signal forms, speed measuring devices can be divided into analog and digital, which are of various types and are widely used. Commonly used speed measurement devices include photoelectric, capacitive, variable reluctance, and tachogenerators.

The existing technology mainly measures the rotational speed by directly transmitting the rotational state, but this form causes the speed measuring device to generate a certain amount of load and resistance to the speed measuring shaft, which is especially obvious in the electromechanical system. In addition, the bearing bush of the internal measurement device is constantly rubbed under the condition of electrification, and it is also very easy to heat up, and even after wear, it may generate electric sparks, which seriously affects the performance of the electrical connector and leads to the occurrence of dangerous accidents. And most of the current speed measurement devices need to use precision micromachining to manufacture the core components of the measurement device, so that the design of this measurement device requires a complex microstructure; this results in poor stability, poor safety and limited application range of the existing speed measurement devices. The problem.

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

Utility model content

The technical problem to be solved by the present invention is to provide a non-contact magnetic fluid rotational speed measuring device in view of the above-mentioned defects in the prior art, which aims to solve the problem of poor stability, poor safety and small application range of the prior art rotational speed measuring device.

The technical scheme adopted by the utility model to solve the technical problem is as follows: a non-contact magnetic fluid rotational speed measuring device, which measures the rotational speed of the object to be measured through an external current detection circuit, which comprises: a speed measuring shaft and a speed measuring sleeve arranged coaxially, The speed measuring sleeve is sleeved on the speed measuring shaft, and a gap is arranged between the speed measuring shafts; the speed measuring sleeve is provided with a speed measuring cavity, and the speed measuring cavity is provided with a conductive coating, an induction electrode and a Magnetic fluid, the conductive coating and the sensing electrode are externally connected to a current detection circuit, and are arranged coaxially with the speed measuring shaft; the speed measuring shaft is fixed with a speed measuring magnet, and the speed measuring magnet and the sensing electrode are arranged in the same radial direction; The speed measuring shaft is used to connect the rotational speed output end of the object to be measured, and drive the speed measuring magnet to rotate synchronously.

Further, the non-contact magnetic fluid rotational speed measuring device further includes a sensing electrode ring, the sensing electrode ring is fixed on the surface of the speed measuring cavity away from the speed measuring shaft, and the sensing electrode ring is provided with sensing electrodes at intervals. electrode.

Further, the speed measuring sleeve is set as a hollow cylinder, the speed measuring cavity has a first inner surface close to the speed measuring shaft and a second inner surface relatively far away from the speed measuring shaft, and the conductive coating is provided. On the first inner surface, the sensing electrode ring is disposed on the second inner surface.

Further, the non-contact magnetic fluid rotational speed measuring device further includes a base, and one end of the speed measuring sleeve is integrally connected with the base.

Further, a sealing end cover is provided at one end of the speed measuring sleeve away from the base, and the sealing end cover is arranged in a circular ring shape.

Further, between the speed measuring sleeve and the sealing end cover, a sealing permanent magnet is further arranged near the first inner surface.

Further, the above-mentioned non-contact magnetic fluid rotational speed measuring device further includes a rotor, the rotor is arranged between the speed measuring shaft and the speed measuring sleeve, the rotor is fixed on the speed measuring shaft, and is connected with the speed measuring shaft. A gap is set between the speed measuring sleeves, and the speed measuring magnet is arranged on the surface of the rotor facing the speed measuring sleeve.

Further, a rotor sink is provided on the surface of the rotor facing the speed measuring sleeve, and the speed measuring magnet is fixed on the rotor sink through a fixed slider, and the fixed slider is screwed with the rotor. fixed.

Further, the connecting end of the rotor and the speed measuring shaft is provided with a shaft end baffle.

Further, the rotor and the speed measuring shaft are detachably and fixedly connected by a fixed key; a first key slot is provided on the contact surface of the rotor and the speed measuring shaft, and a second key position is correspondingly opened on the speed measuring shaft. A key recess, the fixed key is accommodated in the first key recess and the second key recess.

Compared with the prior art, the utility model provides a non-contact magnetic fluid rotational speed measuring device; the non-contact magnetic fluid rotational speed measuring device measures the rotational speed of the object to be measured through an external current detection circuit, which comprises: a coaxial center; The speed measuring shaft and the speed measuring sleeve are provided, the speed measuring sleeve is sleeved on the speed measuring shaft, and a gap is set between the speed measuring shafts; the speed measuring sleeve is provided with a speed measuring cavity, and the speed measuring cavity is inside A conductive coating, an inductive electrode and a magnetic fluid are provided. The conductive coating and the inductive electrode are connected to a current detection circuit and are arranged coaxially with the speed measuring shaft; the speed measuring shaft is fixed with a speed measuring magnet, and the speed measuring magnet is The induction electrodes are arranged in the same radial direction; the speed measuring shaft is used for connecting the rotational speed output end of the object to be measured, and synchronously drives the speed measuring magnet to rotate. Furthermore, the speed measurement load of the speed measurement shaft is reduced, and its safety, stability and application range are improved.

Description of drawings

FIG. 1 is a first perspective schematic diagram of a non-contact magnetic fluid rotational speed measuring device of the present invention.

2 is a second perspective schematic diagram of a non-contact magnetic fluid rotational speed measuring device in the present invention.

3 is a schematic cross-sectional view of a non-contact magnetic fluid rotational speed measuring device in the present invention.

FIG. 4 is an enlarged schematic diagram of A in FIG. 3 .

FIG. 5 is an enlarged schematic diagram of B in FIG. 3 .

Detailed ways

In order to make the purpose, technical solutions and advantages of the present utility model more clear and definite, the present utility model is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not intended to limit the present invention.

Please refer to FIG. 1 , the present invention provides a non-contact magnetic fluid rotational speed measuring device 10 , the non-contact magnetic fluid rotational speed measuring device 10 realizes the The object to be measured rotates synchronously, and outputs a current pulse signal through an external current detection circuit (not shown), and then calculates the rotation speed of the rotation output terminal according to the current pulse signal. The non-contact magnetic fluid rotational speed measuring device 10 includes a speed measuring shaft 11 and a speed measuring sleeve 12, and the speed measuring sleeve 12 is sleeved on the speed measuring shaft 11; further, the speed measuring sleeve 12 and the speed measuring shaft 11 They are arranged concentrically, and a gap is set between the speed measuring sleeve 12 and the speed measuring shaft 11 ; that is, the speed measuring shaft 11 and the speed measuring sleeve 12 are not in contact with each other. Then, the speed measurement load and resistance of the speed measurement shaft 11 are effectively reduced, and the direct friction damage, heat generation and even generation of electric sparks of the speed measurement shaft 11 and the speed measurement sleeve 12 are also effectively avoided. The service life improves its stability and scope of use; at the same time, it also effectively avoids dangerous accidents and improves its safety and scope of application.

Please further refer to FIG. 2, FIG. 3 and FIG. 4. Further, the speed-measuring sleeve 12 is provided with a speed-measuring cavity 121, and the speed-measuring cavity 121 is provided with a conductive coating 122, a sensing electrode 123 and a magnetic fluid ( (not shown), the conductive coating 122 is provided with a gap between the sensing electrodes 123, that is, the sensing electrodes 123 and the conductive coating 122 are not in contact, and the magnetic fluid is filled in the sensing electrodes 123. In the speed measurement cavity 121; at the same time, the conductive coating 122 and the sensing electrode 123 are externally connected to a current detection circuit, and are arranged coaxially with the speed measurement shaft 11; specifically, the conductive coating 122 is externally connected to the current of the current detection circuit. The input end, the sensing electrode 123 is connected to the current output end of the current detection circuit; that is, the conductive coating is an electrode connected to the current detection circuit in the speed measuring cavity 121, and the sensing electrode 123 is the speed measuring cavity 121 When the conductive coating 122 and the sensing electrode 123 are electrically connected, the external circuit detection circuit will generate a current signal; further, by controlling the conductive coating 122 and the sensing electrode 123 The closing and opening of the sensing electrode 123 controls the non-contact magnetic fluid rotational speed measuring device 10 to output a current pulse signal.

Please further refer to FIG. 5 , further, the speed measuring shaft 11 is fixed with a speed measuring magnet 111 , and the speed measuring magnet 111 and the sensing electrode 123 are arranged in the same radial direction; the speed measuring magnet 111 can generate a magnetic field and It can be understood that the speed-measuring shaft 11 supports the rotation of the speed-measuring magnet 111, so that the direction of the magnetic-line of the speed-measuring magnet 111 changes continuously; when the speed-measuring magnet 111 and the sensing electrode 123 have the same diameter When distributed, the tachometer magnet 111 will generate a magnetic field line connecting the sensing electrode 123 and the conductive coating 122 . At the same time, it should be noted that the magnetic fluid includes ferrofluid, non-magnetic conductive particles and a base liquid, and the ferrofluid and non-magnetic conductive particles are uniformly distributed in the base liquid; it can be seen that the ferrofluid and base fluid are insulators. Further, under the action of the magnetic field of the tachometer magnet, the non-magnetic conductive particles will self-assemble in the direction of the magnetic field line to form a chain structure. The non-magnetic conductive particles of the chain structure can realize the induction electrode 123 and the conductive particles. Because of the electrical conduction between the coatings 122, the state of the magnetic fluid can be changed by controlling the magnetic field to realize the closing and opening of the circuit, so that the non-contact magnetic fluid rotational speed measuring device 10 outputs a current pulse signal.

Specifically, when the speed measuring magnet 111 and the sensing electrode 123 are distributed in the same radial direction, the speed measuring magnet 111 will generate a magnetic field line connecting the sensing electrode 123 and the conductive coating 122, thereby making the non- The magnetic conductive particles connect the sensing electrode 123 and the conductive coating 122 in a chain, and then electrically conduct the sensing electrode 123 and the conductive coating 122, so that the measurement finally makes the non-contact magnetic fluid rotational speed measuring device 10 output a current pulse At the same time, since the speed measuring shaft 11 is connected to the rotation output end of the object to be measured, and the speed measuring magnet 111 is constantly rotating, that is, the direction of the magnetic field line of the speed measuring magnet 111 is also constantly changing; further, whenever the speed measuring magnet 111 is continuously rotated When the tachometer magnet 111 and the sensing electrode 123 are distributed in the same radial direction, a magnetic field line connecting the conductive coating 122 and the sensing electrode 123 will be generated, that is, the non-magnetic conductive particles are linked to the sensing electrode. 123 and the conductive coating 122, the sensing electrode 123 and the conductive coating 122 are electrically conducted once, the non-contact magnetic fluid rotational speed measuring device 10 outputs a current pulse signal, and then the number of current pulse information can be detected , to measure the number of turns of the rotation output end of the object to be measured. It should be noted that the current detection circuit is in the prior art, and it only needs to detect the presence of current, and the present invention is only for application, and does not specifically limit the current detection circuit.

Please continue to refer to FIG. 4 , further, the speed measuring sleeve 12 is set in a hollow cylindrical shape, and the speed measuring cavity 121 has a first inner surface 125 close to the speed measuring shaft 11 and a first inner surface 125 relatively far away from the speed measuring shaft 11 . The second inner surface 126, the conductive coating 122 is provided on the first inner surface 125, the second inner surface 126 is provided with a sensing electrode ring (not shown), and the sensing electrode ring is provided with sensors at intervals For the electrode 123 , the conductive coating 122 is coated on the entire first inner surface 125 , and the magnetic fluid is filled between the sensing electrode 123 and the conductive coating 122 . It can be understood that the sensing electrodes 123 include one or more. When there are multiple sensing electrodes 123, the sensing electrodes 123 are evenly distributed on the sensing electrode ring, and the speed measuring shaft 11 carries the speed measuring shaft 11. One rotation of the magnet 111 will cause the magnetic fluid to electrically conduct the plurality of sensing electrodes 123 and the conductive coating 122 in turn, thereby enabling the non-contact magnetic fluid rotational speed measuring device 10 to output a current pulse signal equivalent to the number of sensing electrodes 123 , so that the non-contact magnetic fluid rotational speed measuring device 10 can complete the accurate measurement of the rotational speed of the object to be measured under the condition of no load, which effectively improves the stability and safety of rotational speed measurement.

In one embodiment, the sensing electrode ring is made of polymer material and insulating hard plastic; specifically, the sensing electrode 123 and the circuit are first plated on the surface of the polymer material, and then sealed and bent to fit. On the inner surface of the annular fixing member made of insulating hard plastic, the circuit is connected to the output end of the test current, and then outputs the current on the sensing electrode 123 in time, thereby generating a current pulse signal.

It should be noted that the test sensing electrode ring can also be used to adjust the gap size of the speed measuring cavity 121 , that is, the sensing electrode ring can also be used to adjust the sensing electrode 123 and the conductive coating 122 It can be understood that the gap between the speed measuring cavity 121 is filled with magnetic fluid, and the size of the gap between the sensing electrode 123 and the conductive coating 122 is 50-100 μm; it can be seen that the sensing electrode 123 The size of the gap with the conductive coating 122 is negatively correlated with the rotational speed of the object to be measured; that is, the greater the rotational speed of the object to be measured, the greater the gap between the sensing electrode 123 and the conductive coating 122. At the same time, the smaller the rotational speed of the object to be measured, the larger the gap between the sensing electrode 123 and the conductive coating 122; of course, when the rotational speed of the object to be measured is small, the sensing electrode 123 and the The gap between the conductive coatings 122 can also be set smaller. Further, the size of the gap between the sensing electrode 123 and the conductive coating 122 can be adjusted through the sensing electrode ring, so that the non-contact magnetic fluid rotational speed measuring device 10 can accurately measure the rotational speed of objects with different rotational speeds, thereby improving the rotational speed of the non-contact magnetic fluid. The measuring device 10 measures stability.

Preferably, the non-contact magnetic fluid rotational speed measuring device 10 further includes a base 13 , one end of the speed measuring sleeve 12 is integrally connected with the base 13 , and one end of the speed measuring sleeve 12 away from the base 13 is provided with a base 13 . Opening (not shown), the end of the speed measuring sleeve 12 away from the base 13 is provided with a sealing end cover 14, and the sealing end cover 14 is arranged in a ring shape; that is, one end of the speed measuring cavity 121 is closed The base is sealed, and the other end is sealed by the sealing end cover 14; and by setting the sealing end cover 14, the replacement and filling of the magnetic fluid solution in the speed measuring cavity 121 can be realized, and it is also convenient to maintain the Speed sleeve 12. It should be noted that the base 13 is made of a non-magnetic material, so as to effectively avoid interfering with the magnetic field distribution of the speed measuring magnet 111 in the speed measuring cavity 121 , thereby effectively increasing the non-contact magnetic fluid speed measuring device 10 speed measurement stability and accuracy.

Preferably, a sealing permanent magnet 15 is further provided between the speed measuring sleeve 12 and the sealing end cover 14 near the first inner surface 125 . The sealing permanent magnet 15 is used to assist the sealing end cover 14 to enhance the sealing effect of the magnetic fluid in the speed measuring cavity 121 and prevent the magnetic fluid from leaking.

Preferably, the non-contact magnetic fluid rotational speed measuring device 10 further includes a rotor 16 , the rotor 16 is arranged between the speed measuring shaft 11 and the speed measuring sleeve 12 , and the rotor 16 is fixed on the speed measuring shaft 11 The speed measuring magnet 111 is disposed on the surface of the rotor 16 facing the speed measuring sleeve 12 . Further, the rotor 16 is arranged in an annular shape, and the inner diameter of the rotor 16 is adapted to the outer diameter of the speed measuring shaft 11 ; one end of the rotor 16 is fixed to the speed measuring shaft 11 through a fixing key 19 on one end.

Specifically, the surface of the rotor 16 in contact with the speed measuring shaft 11 is provided with a first key recess (not marked in the figure), and the speed measuring shaft 11 is correspondingly provided with a second key recess (not marked in the figure), so The fixed key 19 is accommodated in the first key recess and the second key recess; it can be understood that the fixing of the rotor 16 and the speed measuring shaft 11 can be achieved by setting the fixed key 19; at the same time, it can also be realized Replacement and maintenance of the rotor 16 or the speed measuring shaft 11 .

Furthermore, the rotor 16 is provided with a rotor sink (not shown in the figure) on the surface of the rotor 16 facing the speed measuring sleeve 12 , and the speed measuring magnet 111 is fixed on the rotor sink through a fixed slider 18 . The fixed slider 18 and the rotor 16 are screwed and fixed. It should be noted that the rotor 16 is fixed in contact with the speed measuring shaft 11, while the rotor 16 is not in contact with the speed measuring sleeve 12; thereby effectively reducing the speed measuring load of the speed measuring shaft 11 and improving the Safety of non-contact magnetofluidic tachometers when measuring rotational speed.

Preferably, a shaft end baffle 17 is provided at the connecting end of the rotor 16 and the speed measuring shaft 11 . That is, the end of the rotor 16 and the speed measuring shaft 11 away from the object to be measured is sealed by the shaft end baffle 17; the shaft end baffle 17 is set as a circular plate, which is fixed on the rotor 16 by bolts By setting the shaft end baffle 17 , the interference of dust on the rotor 16 and the speed measuring shaft 11 can be effectively avoided, and the use range of the non-contact magnetic fluid rotational speed measuring device 10 can be improved.

Further, based on the rotational speed measurement method of the above-mentioned non-contact magnetic fluid rotational speed measuring device, for measuring the rotational speed of the object to be measured, it includes:

connecting the rotational speed output end of the object to be measured with the speed measuring shaft of the above-mentioned non-contact magnetic fluid rotational speed measuring device of the present invention;

After the object to be tested is turned on, the rotational speed of the object to be tested is R=N/(m×T), where N is the number of current pulse signals received by the current detection circuit in the time period T; m is the number of current pulse signals received by the current detection circuit; The number of sensing electrodes.

Further based on the design method of the non-contact magnetic fluid rotational speed measuring device provided by the present utility model, it includes:

Select the type of ferrofluid.

Specifically, the magnetic fluid mainly includes non-magnetic conductive particles, ferrofluid and base liquid; wherein the particle size of the non-magnetic conductive particles is set to micron-scale or nano-scale; according to the physical and chemical properties of the non-magnetic conductive particles A ferrofluid is selected as the base fluid; wherein, the ferrofluid is an insulator, and the non-magnetic conductive particles are uniformly dispersed, suspended and dissolved in the ferrofluid. Further, the ferrofluid is selected as a temperature-sensitive insulating ferrofluid with good heat dissipation; the base fluid can be prepared with solvents such as water, engine oil, and hydroxyl oil; and the non-magnetic conductive particles are used in the design of the magnetic field. The self-assembly efficiency of the chain length L can reach 70% under the strength.

The components of the non-contact magnetic fluid rotational speed measuring device are designed according to the rotational speed output end of the object to be measured and the rotational speed measurement environment.

Specifically, whether the speed output end of the object to be measured has magnetism, shaft diameter size, speed range and measurement environment, etc., design the speed measuring sleeve, speed measuring shaft, key and shaft end stop of the non-contact magnetic fluid speed measuring device Components such as plate tacho magnets and magnet stops with threaded holes.

According to the width and rotational speed measurement requirements of the tachometer magnet, the number m of induction electrodes is designed.

Design the base according to the installation environment and position size, spray the conductive coating on the bottom of the speed measuring cavity, install the sensing electrode ring, and check the coaxiality between the base and the sensing electrode ring, and adjust the speed measuring cavity through the thickness of the sensing electrode ring fixing part the actual effective clearance.

Specifically, the actual effective gap of the speed measuring cavity, that is, the gap between the sensing electrode and the conductive coating, and the gap between the sensing electrode and the conductive coating should be smaller than all The length of the non-magnetic conductive particles assembled into chains under the magnetic field strength. Further, define the gap between the sensing electrode and the conductive coating as L ₁ , and define the length of the non-magnetic conductive particles assembled into chains under the magnetic field strength as L ₂ , then the L ₂ /4<L ₁ < L ₂ .

Design the sealing end cap according to the size of the base, design the end cap to seal the permanent magnet installation slot on the sealing end cap, install the sealing permanent magnet, and fill the prepared ferrofluid mixed with non-magnetic conductive particles into the speed measuring cavity and Test its leak-proof properties.

Further, a gap of 0.02-0.20mm needs to be left between the sealed permanent magnet and the speed measuring sleeve.

Install the rotor equipped with the speed measuring magnet and the magnet block with threaded holes on the speed measuring shaft through the key connection and the shaft end baffle, and place the speed measuring shaft in the test position corresponding to the induction electrode ring.

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

Compared with the prior art, the utility model provides a non-contact magnetic fluid rotational speed measuring device; the non-contact magnetic fluid rotational speed measuring device measures the rotational speed of the object to be measured through an external current detection circuit, which comprises: a coaxial center; The speed measuring shaft and the speed measuring sleeve are provided, the speed measuring sleeve is sleeved on the speed measuring shaft, and a gap is set between the speed measuring shafts; the speed measuring sleeve is provided with a speed measuring cavity, and the speed measuring cavity is inside A conductive coating, an inductive electrode and a magnetic fluid are provided. The conductive coating and the inductive electrode are connected to a current detection circuit and are arranged coaxially with the speed measuring shaft; the speed measuring shaft is fixed with a speed measuring magnet, and the speed measuring magnet is The induction electrodes are arranged in the same radial direction; the speed measuring shaft is used for connecting the rotational speed output end of the object to be measured, and synchronously drives the speed measuring magnet to rotate. Thus, the speed measurement load of the speed measurement shaft is effectively reduced, and its safety, stability and application range are improved.

It should be understood that the application of the present invention is not limited to the above-mentioned examples. For those of ordinary skill in the art, improvements or transformations can be made according to the above descriptions. All these improvements and transformations should belong to the protection of the appended claims of the present invention. scope.

Claims (10)

1. a non-contact magnetic fluid rotational speed measuring device, measures the rotational speed of the object to be measured by an external current detection circuit, is characterized in that, comprises: a speed measuring shaft and a speed measuring sleeve arranged concentrically, the speed measuring sleeve is sleeved on the speed measuring shaft, and a gap is arranged between the speed measuring shafts; The speed measuring sleeve is provided with a speed measuring cavity, and the speed measuring cavity is provided with a conductive coating, an inductive electrode and a magnetic fluid, and the conductive coating and the inductive electrode are connected to a current detection circuit, and are coaxial with the speed measuring shaft set up; The speed measuring shaft is fixed with a speed measuring magnet, and the speed measuring magnet and the induction electrode are arranged in the same radial direction; The speed measuring shaft is used to connect the rotational speed output end of the object to be measured, and drive the speed measuring magnet to rotate synchronously. 2 . The non-contact magnetic fluid rotational speed measuring device according to claim 1 , wherein the non-contact magnetic fluid rotational speed measuring device further comprises an inductive electrode ring, and the inductive electrode ring is fixed in the speed measuring cavity. 3 . On the surface of the body away from the speed measuring shaft, the sensing electrodes are arranged at intervals on the sensing electrode ring. 3 . The non-contact magnetic fluid rotational speed measuring device according to claim 2 , wherein the speed measuring sleeve is configured as a hollow cylinder, and the speed measuring cavity has a first inner surface close to the speed measuring shaft. 4 . and a second inner surface relatively far away from the speed measuring shaft, the conductive coating is arranged on the first inner surface, and the induction electrode ring is arranged on the second inner surface. 4 . The non-contact magnetic fluid rotational speed measuring device according to claim 3 , wherein the non-contact magnetic fluid rotational speed measuring device further comprises a base, and one end of the speed measuring sleeve is integrally connected with the base. 5 . 5 . The non-contact magnetic fluid rotational speed measuring device according to claim 4 , wherein the end of the speed measuring sleeve away from the base is provided with a sealing end cover, and the sealing end cover is arranged in a ring shape. 6 . 6 . The non-contact magnetic fluid rotational speed measuring device according to claim 5 , wherein a sealing permanent magnet is also provided near the first inner surface between the speed measuring sleeve and the sealing end cover. 7 . . 7. The non-contact magnetic fluid rotational speed measuring device according to any one of claims 1-6, wherein the non-contact magnetic fluid rotational speed measuring device further comprises a rotor, and the rotor is arranged on the speed measuring device Between the shaft and the speed measuring sleeve, the rotor is fixed on the speed measuring shaft, and a gap is provided between the rotor and the speed measuring sleeve, and the speed measuring magnet is arranged on the surface of the rotor facing the speed measuring sleeve. 8 . The non-contact magnetic fluid rotational speed measuring device according to claim 7 , wherein a rotor sink is provided on the surface of the rotor facing the tachometer sleeve, and the tachometer magnet is fixed by a fixed slider. 9 . On the rotor sink, the fixed slider and the rotor are screwed and fixed. 9 . The non-contact magnetic fluid rotational speed measuring device according to claim 8 , wherein a shaft end baffle is provided at the connecting end of the rotor and the speed measuring shaft. 10 . 10. The non-contact magnetic fluid rotational speed measuring device according to any one of claims 8-9, wherein the rotor and the speed measuring shaft are detachably and fixedly connected by a fixed key; the rotor and the A first key recess is provided on the contact surface of the speed measuring shaft, a second key recess is correspondingly provided on the speed measuring shaft, and the fixed key is accommodated in the first key recess and the second key recess. in the slot.

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