Speed sensor for rail transit vehicle and preparation method

Abstract

The invention discloses a speed sensor for a rail transit vehicle and a preparation method, the speed sensor comprises a probe assembly, an outer shell, a joint, a cable and an electric connector, the outer shell is of a cylindrical structure and is fixedly assembled at one end of the probe assembly, and two ends of the cable are electrically connected with the probe assembly and the electric connector respectively; the joints are arranged on the peripheries of two ends of the cable; the probe assembly comprises a base and a positioning block, the positioning block is embedded in the base and matched with the base to clamp the Hall integrated chip, and sealant is poured into an area, where the positioning block is arranged, in the base; the Hall integrated chip is electrically connected with an acquisition board and a processing board, the acquisition board and the processing board are connected through a bonding pad, the outer shell is in threaded connection with one end of the probe assembly, and sealant is poured into the outer shell. The Hall integrated chip is clamped and limited by arranging the positioning block, the chip is fixed through glue injection, meanwhile, the acquisition board and the processing board are connected through the bonding pad, operation is easy, and reliability is high.

Description

Technical Field

[0001] The present invention relates to the technical field of rail transit equipment, and in particular to a speed sensor for rail transit vehicles and a preparation method thereof. Background Art

[0002] During the operation of rail transit vehicles, it is usually necessary to set up a speed sensor to measure the low speed of the wheelset and output the speed signal to the control system for vehicle control. At present, the speed sensor commonly used in rail transit vehicles is the Hall speed sensor, which provides a periodically changing magnetic field to the Hall probe through the rotating body to be measured. The Hall element converts the induced cyclically changing magnetic field signal into a Hall voltage signal. After the voltage signal is processed by the signal shaping circuit, it can output a square wave signal to the acquisition object. However, the commonly used Hall speed sensor currently has a complex structure, a small base space, and the metal anti-rotation ring installed inside requires the internal and external processing of the slot structure, which is relatively complicated to process and assemble; at the same time, the wire welding between the acquisition module and the processing module is prone to failure in a complex operating environment with variable humidity and heat, alternating hot and cold, strong vibration, and high impact.

[0003] Therefore, how to improve the assembly convenience and operational reliability of speed sensors for rail transit vehicles is a technical problem that needs to be urgently solved by those skilled in the art. Summary of the invention

[0004] In view of this, an object of the present invention is to provide a speed sensor for rail transit vehicles, which is easy to assemble and has high operational reliability.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned speed sensor.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A speed sensor for rail transit vehicles, comprising a probe assembly, an outer shell, a joint, a cable and an electrical connector, wherein the outer shell is a cylindrical structure and is fixedly assembled on one end of the probe assembly, the two ends of the cable are electrically connected to the probe assembly and the electrical connector respectively, and the joint is arranged on the outer periphery of the two ends of the cable for waterproof protection;

[0008] The probe assembly includes a base and a positioning block, the positioning block is embedded in the base and cooperates with the base to clamp the Hall integrated chip, and the area of ​​the base where the positioning block is set is filled with sealant; the Hall integrated chip is electrically connected to the acquisition board and the processing board, the acquisition board and the processing board are connected through a welding pad and extend from one end of the base into the enclosure area of ​​the outer shell, the outer shell is threadedly connected to one end of the probe assembly and the sealant is poured inside.

[0009] Preferably, in the above-mentioned speed sensor for rail transit vehicles, two mounting grooves for the Hall integrated chip to be clamped are provided on the positioning block, the depth of the mounting grooves is the same as the thickness of the Hall integrated chip, the two mounting grooves are located on both sides of the first diameter and are staggered along the direction of the first diameter, and the two mounting grooves are symmetrical about the center center of the circle of the plane on which they are set.

[0010] Preferably, in the above speed sensor for rail transit vehicles, at least two limiting protrusions are symmetrically arranged inside the base, and the outer wall of the positioning block is correspondingly provided with two recessed parts to engage with the base for limiting position.

[0011] Preferably, in the above speed sensor for rail transit vehicles, the outer periphery of the base is further provided with an annular groove for sleeve-mounting a rubber sealing ring.

[0012] Preferably, in the above-mentioned speed sensor for rail transit vehicles, the processing board and the acquisition board are vertically arranged, the acquisition board is a blank circuit board, and the processing board is integrated with resistors and capacitors required for signal acquisition and processing.

[0013] Preferably, in the above speed sensor for rail transit vehicles, two slots are arranged on the acquisition board at intervals, and the processing board is inserted into the two slots at the same time and is welded and fixed to the acquisition board in the slot area.

[0014] Preferably, in the above-mentioned speed sensor for rail transit vehicles, the Hall integrated chip is electrically connected to the processing board through the acquisition board, or the Hall integrated chip is directly electrically connected to the processing board.

[0015] Preferably, in the above-mentioned speed sensor for rail transit vehicles, the sealant is epoxy resin glue, and the positioning block is made of nylon and is produced by 3D printing.

[0016] Preferably, in the above-mentioned speed sensor for rail transit vehicles, the cable is a special customized cable of 6×0.6mm² and a double-layer rubber sheath with an outer diameter of 13mm, the shielding layer conductor of the cable is tinned copper braided, the cable conductor is a silver-plated copper conductor, and the bending radius of the cable is not greater than 6D.

[0017] A method for preparing a speed sensor, used for preparing the speed sensor described in any one of the above embodiments, the preparation method at least comprising the following steps:

[0018] Install the Hall integrated chip: install the Hall integrated chip into the installation slot on the positioning block and weld it to the acquisition board. The processing board and the acquisition board are welded and fixed in a vertical state through the pads;

[0019] Install the positioning block: embed the positioning block into the base and snap it into place, pour epoxy resin glue into the base, and the pouring depth of the epoxy resin glue covers the positioning block;

[0020] Install the outer shell: After the epoxy resin glue outside the positioning block is cured, screw the outer shell into one end of the base. The outer shell encloses the processing board extending out of the base. Pour the epoxy resin glue between the outer shell and the base for the second time to fill the concave area of ​​the base.

[0021] Install the sensor: After the epoxy resin glue in the base is cured, a connector is installed on one end of the cable and screwed to the outer shell to lock the cable. A structure is installed on the other end of the cable and an electrical connector is installed.

[0022] It can be seen from the above technical scheme that the speed sensor for rail transit vehicles provided by the present invention has a positioning block arranged inside the base of the probe assembly to realize the pre-installation and limiting of the Hall integrated chip through the positioning block, and a first layer of sealant is poured into the groove of the base to encapsulate and protect the positioning block and the Hall integrated chip after the positioning block is installed; the acquisition board and the processing board electrically connected to the Hall integrated chip first remove the lead welding, and realize the conductive connection between the two through the pad structure, and at the same time, the connection area of ​​the acquisition board and the processing board is encapsulated by the second layer of sealant in the groove of the base, and the second layer of sealant is poured after the base is threadedly connected to the outer shell, so as to perform stacking packaging on the first layer of sealant, and the two layers of sealant can encapsulate different areas, and at the same time can improve the filling density of the deeper base groove, and improve the structural stability of the speed sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 A schematic diagram of the structure of a speed sensor provided by an embodiment of the present invention;

[0025] Figure 2 is a structural schematic diagram of the probe assembly;

[0026] Figure 3 for Figure 2 AA cross-sectional structural diagram;

[0027] Figure 4 for Figure 2 BB cross-sectional structure diagram;

[0028] Figure 5 is a schematic diagram of the structure of the base;

[0029] Figure 6 for Figure 5 Schematic diagram of CC cross-section structure;

[0030] Figure 7 for Figure 5 lateral view of;

[0031] Figure 8 It is a structural diagram of the positioning block;

[0032] Fig. 9 for Figure 8 lateral view of;

[0033] Fig.10 It is a structural diagram of the acquisition board and the processing board.

[0034] Among them, 10-probe assembly; 110-base; 1110-limiting protrusion; 1120-annular groove; 120-positioning block; 1210-installation groove; 1220-recess; 130-Hall integrated chip; 140-acquisition board; 1410-card slot; 150-processing board; 20-outer shell; 30-connector; 40-cable; 50-electrical connector. DETAILED DESCRIPTION

[0035] The core of the present invention is to disclose a speed sensor for rail transit vehicles which is easy to assemble and has high operating reliability.

[0036] Another object of the present invention is to provide a method for preparing the above-mentioned speed sensor.

[0037] In order to make the technical personnel in this field better understand the scheme of the present invention, the embodiments of the present invention are described below with reference to the accompanying drawings. In addition, the embodiments shown below do not limit the content of the invention recorded in the claims. In addition, the entire contents of the structures represented by the following embodiments are not limited to those necessary for the solutions of the invention recorded in the claims.

[0038] like Figure 1-10As shown, the speed sensor for rail transit vehicles provided in the embodiment of the present invention mainly includes a probe assembly 10, an outer shell 20, a connector 30, a cable 40 and an electrical connector 50, wherein the probe assembly 10 is built with a Hall element and a circuit board assembly for speed detection of rail transit vehicles. The outer shell 20 is a cylindrical structure and is fixedly assembled at one end of the probe assembly 10 to surround and protect the part of the circuit board assembly extending out of the probe assembly 10, and is used to extend the probe assembly 10 to connect with other structural components. The two ends of the cable 40 are electrically connected to the probe assembly 10 and the electrical connector 50 respectively. It should be noted that the electrical connection here specifically refers to the through connection, so that the electrical connector 50 can supply power to the probe assembly 10 through the cable 40 when plugging in an external power supply to maintain the normal operation of the probe assembly 10. It should be noted that the electrical connector 50 is an imported accessory, which is a designated signal transmission accessory on the vehicle, and the electrical connection is a general requirement of the sensor, which will not be repeated here. On this basis, the connector 30 is arranged on the periphery of the connecting area at both ends of the cable 40 to achieve locking and sealing of the cable 40, and ensure that the cable 40 inside the outer shell 20 will not be pulled by external force, and has good sealing and waterproof performance, and can operate stably under complex operating conditions.

[0039] As for the probe assembly 10 for speed detection, it specifically includes a base 110 and a positioning block 120. The base 110 is the main bearing structure, and a groove structure for accommodating other components is arranged inside the base 110, and the positioning block 120 is embedded and installed inside the base 110. One end of the positioning block 120 contacts the bottom of the groove on the base 110 and clamps the Hall integrated chip 130 in the contact area, so that the Hall integrated chip 130 can be limited and pre-installed by the positioning block 120. At the same time, the area where the positioning block 120 is embedded in the base 110 is also filled with sealant, so that the Hall integrated chip 130 is fixedly assembled and well protected. On this basis, the Hall integrated chip 130 is also electrically connected to the acquisition board 140 and the processing board 150. It should be noted that the electrical connection here specifically refers to the signal connection between the Hall integrated chip 130 and the acquisition board 140 and the processing board 150 so as to receive the voltage signal emitted by the Hall integrated chip 130. The acquisition board 140 and the processing board 150 are conductively connected through the solder pad and extend from one end of the base 110.

[0040] It should be noted that the Hall integrated chip 130 converts the cyclically changing magnetic field signal into a Hall voltage signal, and after being processed by the signal shaping circuit, outputs a square wave signal to the acquisition object. The frequency of this signal is proportional to the frequency of the magnetic field change, that is, the rotation speed of the object being measured. The rotation speed of the object being measured can be known by detecting the signal frequency.

[0041] The collection board 140 and the processing board 150 are connected through the pads to improve the overall reliability of the circuit board. In the current existing technology, some components on the surface of the collection board 140 need to be welded to the processing board 150 through leads, which requires manual operation and is extremely difficult to operate in a limited space. It is very easy to burn the external insulation layer of the lead, and the lead is in a stress state for a long time. Connecting the collection board 140 and the processing board 150 through the pads can reduce the risk of connection failure.

[0042] On the basis of the above structure, one end of the probe assembly 10 is preferably threadedly connected to the outer shell 20 to facilitate assembly and maintain the stability of the connection. The outer shell 20 protects the area where the acquisition board 140 and the processing board 150 extend out of the probe assembly 10, and after the outer shell 20 is connected to the base 110, the groove area of ​​the base 110 is injected with glue for the second time. It should be noted that the base 110 needs to be provided with a positioning block 120 and a connection circuit of the Hall integrated chip 130, and its groove area is relatively deep. The currently commonly used one-time potting operation is prone to insufficient potting and causes local cavities; and during the potting operation, the signal cable 40 is prone to pulling the circuit board and the welding point. The second potting of the base 110 can divide the area to be sealed into two parts for operation, and the single potting operation is simpler and more accurate to improve the structural stability of the base 110 after potting.

[0043] In the speed sensor for rail transit vehicles provided by the embodiment of the present invention, a positioning block 120 is arranged inside the base 110 of the probe assembly 10, so that the Hall integrated chip 130 can be pre-installed and limited by the positioning block 120, and a first layer of sealant is poured into the groove of the base 110, so that the positioning block 120 and the Hall integrated chip 130 are packaged and protected after the positioning block 120 is installed; the acquisition board 140 and the processing board 150 electrically connected to the Hall integrated chip 130 first remove the lead welding, and realize the conductive connection between the two through the pad structure, and at the same time, the connection area of ​​the acquisition board 140 and the processing board 150 is packaged by the second layer of sealant in the groove of the base 110, and the second layer of sealant is poured after the base 110 is threadedly connected to the outer shell 20, so as to perform stacking packaging on the first layer of sealant, and the two layers of sealant can encapsulate different areas, and at the same time can improve the filling density of the deeper groove of the base 110, and improve the structural stability of the speed sensor.

[0044] Furthermore, in some embodiments of the present invention, two mounting grooves 1210 are provided on the positioning block 120. The mounting grooves 1210 are preferably of a waist-shaped hole structure and match the shape of the Hall integrated chip 130. The Hall integrated chip 130 is embedded and installed in the two mounting grooves 1210. In order to improve the pre-installation stability of the Hall integrated chip 130, the setting depth of the mounting grooves 1210 on the positioning block 120 is the same as the thickness of the Hall integrated chip 130. After the Hall integrated chip 130 is set on the mounting grooves 1210, the plane on which the mounting grooves 1210 are set on the positioning block 120 is filled with a complete plane structure, and the positioning block 120 is completely fitted with the bottom of the groove of the base 110 within the groove area of ​​the base 110.

[0045] On the basis of the above structure, the two mounting grooves 1210 are located on both sides of the first diameter and are staggered along the direction of the first diameter, that is, the plane on which the mounting grooves 1210 are set on the positioning block 120 is a circular structure, and on the diameter passing through the area between the two mounting grooves 1210, the two mounting grooves 1210 are not symmetrical but staggered, which can avoid manual adjustment of the Hall integrated chip 130. At the same time, the two mounting grooves 1210 meet the technical requirements of a 90°±30° phase difference of a dual-channel square wave signal after the Hall integrated chip 130 is set, and the problem of the same square wave signal being unable to accurately measure the speed will not occur due to the symmetrical setting of the mounting grooves 1210 about the same diameter. It should be noted that the two mounting grooves 1210 are preferably symmetrical about the center of the circle of the plane on which they are set, which can not only make the structure of the positioning block 120 more regular, but also reduce the difficulty of assembly without distinguishing whether the Hall integrated chip 130 is installed in the right or wrong direction.

[0046] In order to improve the stability of the positioning block 120 when it is installed in the base 110 and avoid the positioning block 120 from being offset during the injection process, in some embodiments of the present invention, at least two limiting protrusions 1110 are provided inside the base 110, and two recessed parts 1220 are provided on the outer wall of the positioning block 120 correspondingly. It should be noted that the limiting protrusion 1110 can be provided on the inner wall surface or bottom of the groove area on the base 110, and it is only necessary to make the recessed part 1220 of the positioning block 120 be able to engage with it. At the same time, it is preferred that the two limiting protrusions 1110 are symmetrically arranged inside the base 110, and the symmetry here specifically refers to the symmetry of the two limiting protrusions 1110 about a diameter of the cylindrical structure of the base 110. The symmetrically arranged limiting protrusions 1110 enable the positioning block 120 to be automatically aligned inside the base 110 without distinguishing between the front and the back, and the two limiting protrusions 1110 can be used as a backup for each other, reducing the risk of rotation of the positioning block 120 during the injection process.

[0047] Furthermore, in order to improve the sealing and operational safety of the probe assembly 10, an annular groove 1120 is also provided on the outer periphery of the base 110. The annular groove 1120 is a groove structure based on the outer wall surface of the base 110. The annular groove 1120 is used to cover a rubber sealing ring to seal the corresponding area and provide flexible contact during the movement process.

[0048] Regarding the processing board 150 and the acquisition board 140 provided in the embodiments of the present invention, in some embodiments of the present invention, the processing board 150 and the acquisition board 140 are vertically arranged to improve the connection stability between the two. The vertically connected structure is easy to butt-weld during installation, and the acquisition board 140 is an empty circuit board, and the C3, C5 capacitors, R3, R5 resistors, etc. that need to be set thereon are all integrated on the surface of the processing board 150, which is equivalent to the original two circuit board components being set as an empty board and a circuit board component. On this basis, the acquisition board 140 only needs to realize electrical connection with the Hall integrated chip 130 and provide a transfer structure to realize electrical connection with the processing board 150. During the design process, only the structural adaptability needs to be considered, without considering the relationship between the structural setting and the welding stability of the electronic components on it, thereby improving the structural stability. In a preferred embodiment of the present invention, two slots 1410 are arranged at intervals on the acquisition board 140, and the two slots 1410 extend from the side wall of the acquisition board 140 to the central area thereof, and the processing board 150 is inserted into the two slots 1410 at the same time, and is fixed to the acquisition board 140 by welding with pads in the slot 1410 area. The two slots 1410 can prevent the shaking of the processing board 150, and improve the connection stability between the acquisition board 140 and the processing board 150 by two-point welding, so that they can maintain a more stable relative position during the glue injection process.

[0049] It should be noted that the processing circuit on the processing board 150 is usually composed of a transient voltage suppression tube, an anti-reverse connection diode, a filter capacitor, etc. In order to ensure that the speed sensor can operate reliably in the complex and harsh environment of the locomotive and prevent damage caused by surges (interference), a 3000W high-power TVS tube is used at the input end of the Hall integrated chip 130. When a surge high voltage appears in the power supply voltage, the transient voltage suppression tube is quickly turned on, causing the power supply to short-circuit so that it cannot be applied to the subsequent circuit components, forming an overvoltage protection to ensure that the sensor is not damaged. At the same time, the circuit is connected in series with a high reverse voltage resistant diode to ensure that the core components of the circuit are not damaged when the external power supply is reversed. The filter capacitor can smooth the power supply fluctuations to obtain a stable voltage output. After being processed by the amplification and shaping circuit, a square wave signal is finally output.

[0050] Furthermore, in the speed sensor provided in the embodiment of the present invention, on the basis that the acquisition board 140 is an empty board structure, the Hall integrated chip 130 can be electrically connected to the processing board 150 through the acquisition board 140, and the acquisition board 140 provides a structural basis for the connection; and the Hall integrated chip 130 can also be directly electrically connected to the processing board 150, and the processing board 150 needs to be designed as a relatively complex structure. It should be noted that the Hall integrated chip 130 can also be directly electrically connected to the processing board 150 while being electrically connected to the processing board 150 through the acquisition board 140. The two communication paths are backup for each other, thereby reducing the risk of connection failure between the Hall integrated chip 130 and the processing board 150 under complex motion conditions.

[0051] Furthermore, in some embodiments of the present invention, the sealant is epoxy resin glue, which has excellent dielectric properties, good high and low temperature resistance, excellent chemical stability and low internal stress, and has low damage to components. Epoxy resin glue is used at high temperatures and solidifies at room temperature, and is suitable for potting and pouring of circuit boards. At the same time, the material of the positioning block 120 is nylon PA6 to have good insulation properties, and accurate structural production is achieved through 3D printing.

[0052] In addition, in some embodiments of the present invention, the cable 40 is a special customized cable of 6×0.6mm² and a double-layer rubber sheath with an outer diameter of 13mm. The shielding layer conductor of the cable 40 is tinned copper braided, the cable conductor is a silver-plated copper conductor, and the bending radius of the cable 40 is not greater than 6D, which meets the use requirements in the temperature range of -50℃ to +150℃, and the fire protection level meets the HL3 level of EN45545-2R15 / R16.

[0053] Furthermore, an embodiment of the present invention further provides a method for preparing a speed sensor, which is used to prepare the speed sensor provided by any of the above embodiments, and the preparation method at least comprises the following steps:

[0054] S01: Installing the Hall integrated chip: Install the Hall integrated chip 130 into the installation groove 1210 on the positioning block 120 and weld it to the acquisition board 140. The processing board 150 and the acquisition board 140 are welded and fixed in a vertical state through the pads.

[0055] S02: Installing the positioning block: embedding the positioning block 120 in the base 110 and snapping it into place, pouring epoxy resin glue in the base 110 , and the pouring depth of the epoxy resin glue covers the positioning block 120 .

[0056] It should be noted that in the above steps, the setting of the positioning block 120 enables the Hall integrated chip 130 to be manually positioned without the need for calibration with the aid of other equipment, and the positioning block 120 realizes the installation of the Hall integrated chip 130 by snapping it into place with the base 110. The positioning process has a simple structure, and the positioning block 120 will not produce a risk of rotation inside the base 110, and there is no need to set up structures such as anti-rotation rings. In step S02, the pouring of the epoxy resin glue only needs to cover the positioning block 120, and its pouring thickness is lower than the thickness of the groove area on the base 110, which reduces the problem of poor density of the glue layer due to excessive pouring thickness.

[0057] S03: Install the outer shell: After the epoxy resin glue outside the positioning block 120 is cured, the outer shell 20 is screwed into one end of the base 110. The outer shell 20 encloses the processing board 150 extending out of the base 110, and epoxy resin glue is poured between the outer shell 20 and the base 110 for a second time to fill the recessed area of ​​the base 110.

[0058] It should be noted that, in combination with step S02 and step S03, the base 110 is filled by injecting glue twice, which can effectively avoid the occurrence of cavities or faults inside, and the potting process is simple and the glue is fully injected.

[0059] S04: Install the sensor: After the epoxy resin glue in the base 110 is cured, a connector 30 is sleeved on one end of the cable 40 and screwed to the outer shell 20 to lock the cable 40, and a structure is sleeved on the other end of the cable 40 and an electrical connector 50 is installed.

[0060] It should be noted that, for the convenience of description, only the parts related to the invention are shown in the drawings. In the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0061] As shown in the present invention and claims, unless the context clearly indicates an exception, the words "a", "an", "a kind" and / or "the" do not specifically refer to the singular, but may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of clearly identified steps and elements, and these steps and elements do not constitute an exclusive list, and the method or device may also include other steps or elements. The elements defined by the sentence "includes a..." do not exclude the existence of other identical elements in the process, method, commodity or device that includes the elements.

[0062] In the following, the terms "first", "second", "third", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features.

[0063] The above description is only a preferred embodiment of the present invention and an explanation of the technical principles used, and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. The scope of the invention involved in the present invention is not limited to the technical solution formed by a specific combination of the above-mentioned technical features, but also should cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the above-mentioned inventive concept. For example, the above-mentioned features are replaced with the technical features with similar functions disclosed in the present invention (but not limited to) to form a technical solution.

Claims

1. A speed sensor for a rail transit vehicle, characterized in that: It includes a probe assembly, an outer shell, a connector, a cable and an electrical connector. The outer shell is a cylindrical structure and is fixedly assembled on one end of the probe assembly. The two ends of the cable are electrically connected to the probe assembly and the electrical connector respectively. The connector is arranged on the outer periphery of the two ends of the cable for waterproof protection. The probe assembly includes a base and a positioning block, the positioning block is embedded in the base and cooperates with the base to clamp the Hall integrated chip, and the area of ​​the base where the positioning block is set is filled with sealant; the Hall integrated chip is electrically connected to the acquisition board and the processing board, the acquisition board and the processing board are connected through a welding pad and extend from one end of the base into the enclosure area of ​​the outer shell, the outer shell is threadedly connected to one end of the probe assembly and the sealant is poured inside.

2. The speed sensor for rail transit vehicles according to claim 1, characterized in that: The positioning block is provided with two mounting grooves for the Hall integrated chip to be clamped, the depth of the mounting grooves is the same as the thickness of the Hall integrated chip, the two mounting grooves are located on both sides of the first diameter and are staggered along the direction of the first diameter, and the two mounting grooves are symmetrical about the center center of the circle of the plane on which they are set.

3. The speed sensor for rail transit vehicles according to claim 2, characterized in that: At least two limiting protrusions are symmetrically arranged inside the base, and two recessed parts are correspondingly arranged on the outer wall of the positioning block to be engaged with the base for limiting position.

4. The speed sensor for rail transit vehicles according to claim 3, characterized in that: The outer periphery of the base is also provided with an annular groove for sleeve-mounting a rubber sealing ring.

5. The speed sensor for rail transit vehicles according to claim 1, characterized in that: The processing board is vertically arranged with the acquisition board, the acquisition board is a vacant circuit board, and the processing board is integrated with resistors and capacitors required for signal acquisition and processing.

6. The speed sensor for rail transit vehicles according to claim 5, characterized in that: The acquisition board is provided with two slots at intervals, and the processing board is inserted into the two slots at the same time and is welded and fixed to the acquisition board in the slot area.

7. The speed sensor for rail transit vehicles according to claim 5, characterized in that: The Hall integrated chip is electrically connected to the processing board through the acquisition board, or the Hall integrated chip is directly electrically connected to the processing board.

8. The speed sensor for rail transit vehicles according to claim 1, characterized in that: The sealant is epoxy resin glue, and the positioning block is made of nylon and is produced by 3D printing.

9. The speed sensor for rail transit vehicles according to claim 1, characterized in that: The cable is a special customized cable of 6×0.6mm² and a double-layer rubber sheath with an outer diameter of 13mm. The shielding conductor of the cable is tinned copper braided, the cable conductor is a silver-plated copper conductor, and the bending radius of the cable is not greater than 6D.

10. A method for preparing a speed sensor, characterized in that: Used to prepare the speed sensor according to any one of claims 1 to 9, the preparation method at least comprises the following steps: Install the Hall integrated chip: install the Hall integrated chip into the installation slot on the positioning block and weld it to the acquisition board. The processing board and the acquisition board are welded and fixed in a vertical state through the pads; Install the positioning block: embed the positioning block into the base and snap it into place, pour epoxy resin glue into the base, and the pouring depth of the epoxy resin glue covers the positioning block; Install the outer shell: After the epoxy resin glue outside the positioning block is cured, screw the outer shell into one end of the base. The outer shell encloses the processing board extending out of the base. Pour the epoxy resin glue between the outer shell and the base for the second time to fill the concave area of ​​the base. Install the sensor: After the epoxy resin glue in the base is cured, a connector is installed on one end of the cable and screwed to the outer shell to lock the cable. A structure is installed on the other end of the cable and an electrical connector is installed.

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