Neodymium iron boron magnet rapid field weakening detection device and detection method

Abstract

The application discloses a kind of neodymium iron boron magnet quick weak magnetic detection device and detection method, the detection device includes the non-magnetic container for bearing according to N pole and S pole alternate mode continuous arrangement magnet, and the side of non-magnetic container is provided with socket;PCB board can be inserted into socket;Hall sensor is arranged on the side of PCB board, and the sensitive direction of Hall sensor is parallel with the radial direction of magnet;When PCB board is inserted into socket, Hall sensor is used to detect the leakage magnetic intensity of the side of magnet;Signal processing and alarm unit are used to collect the leakage magnetic intensity detected by Hall sensor and compare with preset threshold value, and trigger alarm when leakage magnetic intensity exceeds preset threshold value.The application utilizes the characteristics that magnetic induction lines form closed loop when qualified magnet is continuously arranged, and when weak magnet is mixed, closed loop is destroyed, resulting in that Hall sensor reading appears large fluctuation, and then unqualified product can be accurately identified, and detection speed reaches 100~150 per second, which is suitable for automation demand.

Description

Technical Field

[0001] This invention relates to the field of neodymium iron boron magnet testing technology, and in particular to a rapid weak magnetic field detection device and method for neodymium iron boron magnets. Background Technology

[0002] Neodymium iron boron (NdFeB) magnets are widely used in various fields such as 3C electronics, new energy, and medical devices due to their excellent magnetic properties. After electroplating, the industry commonly uses inkjet printing or laser marking to identify the N or S poles. Currently, inkjet printing and laser marking are automated processes with huge daily output. Equipment malfunctions or human negligence can easily lead to weakly magnetic products being mixed in with qualified products. Currently, the industry's common testing method for weakly magnetic products is to align a Hall sensor vertically with the magnetization direction end face, i.e., the main surface where the N or S pole is located, and directly measure the surface magnetic intensity at the center of that surface to determine whether the magnet is qualified.

[0003] However, in actual mass production, neodymium iron boron magnets are often arranged with N poles and S poles connected alternately, which will cause mutual excitation. If the surface of a magnet at the edge is measured directly, the actual value is not the true surface magnetic intensity. Therefore, traditional methods cannot quickly detect clumps of magnets. Each magnet must be separated and measured individually, which is extremely inefficient and costly, and cannot meet the batch testing needs of enterprises. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art by providing a rapid magnetic field weakening detection device and method for neodymium iron boron magnets, which has a fast detection speed, low cost, and can accurately detect weak magnetic products.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a rapid magnetic field weakening detection device for neodymium iron boron magnets, comprising:

[0006] A non-magnetic container for holding magnets arranged in a continuous pattern of alternating N and S poles, wherein the side of the non-magnetic container has an opening for the magnets to be exposed.

[0007] A PCB board that can be inserted into the socket;

[0008] A Hall sensor is disposed on the side of the PCB board, and the sensitive direction of the Hall sensor is parallel to the radial direction of the magnet; wherein, when the PCB board is inserted into the socket, the Hall sensor extends through the socket to the outside of the side of the magnet to detect the leakage magnetic intensity on the side of the magnet.

[0009] The signal processing and alarm unit is electrically connected to the Hall sensor and is used to collect the leakage magnetic field strength detected by the Hall sensor and compare it with the preset threshold. When the leakage magnetic field strength exceeds the preset threshold, an alarm is triggered.

[0010] Optionally, the Hall sensor is a linear Hall sensor.

[0011] Optionally, the non-magnetic container is a mounting base with a 90-degree right-angled inner wall, used to limit the two adjacent sides of the magnet.

[0012] Optionally, the non-magnetic container is made of PP plastic.

[0013] Optionally, the Hall sensor is provided with a protective housing, and the sensing surface of the Hall sensor is flush with the outer surface of the protective housing; during detection, the outer surface of the protective housing is in close contact with the side of the magnet, and the gap between the Hall sensor and the side of the magnet is 0~0.3mm.

[0014] A detection method for a rapid magnetic weakening detection device for neodymium iron boron magnets includes the following steps:

[0015] The magnets to be tested are arranged continuously on a non-magnetic container with alternating N and S poles.

[0016] The continuously arranged magnets are moved at a constant speed relative to the Hall sensor;

[0017] The leakage magnetic field strength on the side of the magnet detected by the Hall sensor is acquired in real time.

[0018] The leakage magnetic field strength is compared with a preset threshold. When the leakage magnetic field strength exceeds the preset threshold, an alarm is triggered to indicate that there is a defective product at the current detection location.

[0019] Optionally, the preset threshold can be set using the following method:

[0020] A batch of qualified magnets are arranged continuously with alternating N and S poles;

[0021] Record the fluctuation range of the Hall sensor's output reading;

[0022] The maximum value of the fluctuation range is multiplied by a reliability coefficient and set as a preset threshold, wherein the reliability coefficient is 1.1 to 1.3.

[0023] Optionally, when an alarm is triggered, feeding is stopped, and 2 to 6 magnets adjacent to the alarm time are removed and manually retested using standard testing equipment to locate the unqualified magnets.

[0024] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0025] The present invention relates to a rapid magnetic weakening detection device and method for neodymium iron boron magnets. A Hall sensor is installed at the insertion port of a non-magnetic container on the side of a PCB board. When qualified magnets are arranged in a continuous alternating pattern of N and S poles, the magnetic field lines form a closed loop, and the Hall sensor reading approaches zero. When a weak magnetic product is mixed in, the closed loop is broken, and the magnetic field lines leak asymmetrically to one side. The Hall sensor captures the leakage magnetic field strength, causing a significant fluctuation in the magnetic field strength value. The fluctuation value is then compared with a preset threshold to determine the unqualified product. This eliminates the excitation interference of adjacent magnets and achieves accurate identification of weak magnetic products.

[0026] Secondly, the magnets in this testing device can pass through the testing area on the PCB board at a uniform speed after being arranged, without the need to pick up or put down each magnet individually or stop. The testing speed can reach 100~150 magnets / second, which can better meet the needs of automated testing. Attached Figure Description

[0027] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0028] Figure 1 This is a schematic diagram of the structure of a neodymium iron boron magnet rapid weak magnetic field detection device in one embodiment of the present invention;

[0029] Figure 2 This is a top view of the PCB board and the Hall sensor connected in one embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of magnetic field lines when a weakly magnetic product is mixed in with a series of continuously arranged magnets in one embodiment of the present invention.

[0031] Figure 4 This is a schematic flowchart of the detection method of the neodymium iron boron magnet rapid weak magnetic field detection device in one embodiment of the present invention;

[0032] Figure 5 This is a graph showing the distribution of leakage magnetic field strength as a function of position, as collected by the Hall sensor during actual testing.

[0033] The components include: 1. Non-magnetic container; 2. Magnet; 10. Socket; 3. PCB board; 4. Hall sensor; 5. Signal processing and alarm unit. Detailed Implementation

[0034] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0035] For ease of understanding, the embodiments of this application are described in detail below. Please refer to [link / reference]. Figures 1 to 2 A rapid magnetic field weakening detection device for neodymium iron boron magnets according to an embodiment of this application includes a non-magnetic container 1, a PCB board 3, and a Hall sensor 4; the non-magnetic container 1 is used to hold the magnet 2; the Hall sensor 4 is disposed on one side plate of the PCB board 3.

[0036] See Figure 1 The non-magnetic container 1 is made of PP plastic, a non-magnetic material, which avoids interfering with the magnetic field lines distribution between the magnets 2. In this embodiment, the non-magnetic container 1 is L-shaped, serving as a mounting base with a 90° right-angled inner wall. It supports cuboid neodymium iron boron magnets 2 arranged continuously with alternating N and S poles. The 90° right-angled inner wall ensures that the magnets 2 can only move along the arrangement direction, thus guaranteeing the consistency of position for each magnet 2 as it passes through the detection area.

[0037] In a preferred embodiment of the present invention, a rectangular slot 10 is provided on the side of the non-magnetic container 1. The slot 10 is arranged along the direction of the magnet 2. The length and width of the slot 10 are greater than or equal to the corresponding size of the PCB board 3 so that the PCB board 3 can be inserted. Thus, when the PCB board 3 is inserted into the slot 10, the Hall sensor 4 on it is located exactly on the side of the exposed magnet 2.

[0038] In a preferred embodiment of the present invention, the Hall sensor 4 is a linear Hall sensor, whose output is an analog voltage signal that is linearly related to the magnetic field strength, enabling accurate measurement of the leakage magnetic field strength outside the side of the magnet. The leakage magnetic field strength mentioned in this invention refers to the magnetic induction intensity leaked from the external space outside the side of the neodymium iron boron magnet in a continuous N / S arrangement.

[0039] Furthermore, the sensing direction of a linear Hall sensor is defined as the axis in which it is most sensitive to magnetic fields. During installation, the sensing direction of the Hall sensor is adjusted to be parallel to the radial direction of the magnet, that is, perpendicular to the magnetization axis of the magnet and pointing towards the side of the magnet. This orientation allows the Hall sensor to effectively capture the radial leakage magnetic field intensity emitted from the outside of the contact surface of adjacent magnets due to the disruption of the magnetic field line loop, thereby enabling rapid identification of weak magnetic products.

[0040] The PCB board 3 is inserted into the socket 10, allowing the Hall sensor 4 on the PCB board 3 to detect the side leakage magnetic field strength of the magnet 2. The PCB board 3 can be held by hand or fixed in place using a fixing device. Specifically, the Hall sensor 4 is soldered onto the PCB board 3, and is mounted on any side of the PCB board 3, close to the side of the magnet. When the PCB board 3 is inserted into the socket 10, the Hall sensor 4 is positioned precisely on the path of the magnet 2 and remains in a straight line along the direction of the magnet 2.

[0041] Specifically, the Hall sensor 4 is placed parallel to the radial direction of the magnet 2 and directly faces the exposed side of the magnet 2 through the socket 10. The Hall sensor 4 is also provided with a protective shell, and the sensing surface of the Hall sensor is flush with the outer surface of the protective shell. During detection, the outer surface of the protective shell is in close contact with the side of the magnet, and the gap between the Hall sensor and the side of the magnet is 0~0.3mm, preferably 0.1mm, to maximize the capture of leakage magnetic signals caused by weak magnetic fields, while the protective shell prevents the Hall sensor chip from directly scratching the magnet surface.

[0042] See Figure 1 The signal processing and alarm unit 5 is electrically connected to the Hall sensor 4, and internally includes a signal conditioning circuit and an audible and visual alarm. This signal processing and alarm unit 5 is used to acquire the leakage magnetic field strength detected by the Hall sensor 4 in real time, and compare this leakage magnetic field strength with a preset threshold. When the difference exceeds the threshold, an alarm is triggered.

[0043] See Figure 3 In this detection device, when qualified magnets are continuously and closely arranged with alternating N and S poles, a closed magnetic circuit is formed between adjacent magnets. That is, the magnetic field lines emitted from the N pole of one magnet directly enter the S pole of the next magnet. The magnetic field lines on the entire magnetic chain are confined inside the magnet and between adjacent mating surfaces, with little or no leakage magnetic field radiating to the sides. At this time, the leakage magnetic field intensity detected by Hall sensor 4 approaches 0 Gs.

[0044] When a weak magnetic field is introduced into a continuously arranged chain of magnets, the insufficient magnetomotive force prevents the magnetic flux from passing through adjacent magnets, resulting in magnetic saturation blocking. The leaked magnetic field lines deflect to one side of the Hall sensor. These leaked magnetic field lines emerge from the side of the magnet, oriented radially with magnet 2, and are detected by Hall sensor 4. This causes a rapid increase in the magnetic field strength read by Hall sensor 4. The signal processing and alarm unit 5 then compares this magnetic field strength with a preset threshold. When the magnetic field strength exceeds the preset threshold, an audible and visual alarm is triggered, indicating the presence of a defective product at the current detection location.

[0045] This neodymium iron boron magnet rapid magnetic field weakening detection device, by setting a Hall sensor on one side of the PCB board, can directly capture the magnetic field strength of asymmetric leakage generated after the magnetic field line closed loop is broken, eliminating the excitation interference of adjacent magnets, thereby accurately identifying weak magnetic products and achieving high detection efficiency. This detection method can offset interference from other environments, reduce the false alarm rate, has strong anti-interference ability, and its detection efficiency is suitable for large-scale automated production lines.

[0046] See Figure 4 Based on the aforementioned detection device, this invention also discloses a detection method for a rapid weak magnetic field detection device for neodymium iron boron magnets. This method can quickly detect weak magnetic products. Before using the detection method, a preset threshold needs to be determined, and the determination method is as follows:

[0047] First, select a batch of neodymium iron boron magnets that have been confirmed as qualified by standard testing equipment, and arrange them continuously on a non-magnetic container 1 in an alternating N and S pole manner; then, make the neodymium iron boron magnets 2 pass through the Hall sensor at a constant speed, and record the magnetic reading of the Hall sensor for at least 15 minutes; then, multiply the maximum value of the magnetic reading by a reliability coefficient, and set it as a preset threshold A, where the reliability coefficient is 1.1~1.3.

[0048] In actual production, the specific steps for testing neodymium iron boron magnets using the testing device of this invention are as follows:

[0049] Step 1: Arrange the neodymium iron boron magnets 2 to be tested one after another in an alternating N and S pole manner to form a long continuous magnet chain, and place it in a non-magnetic container 1.

[0050] Step 2: Move the magnets relative to the Hall sensor at a constant speed by means of a conveyor belt or manual pushing; the moving speed can be adjusted according to production efficiency, and in this embodiment, it is preferably 100-150 magnets / second.

[0051] Step 3: The signal processing and alarm unit collects the leakage magnetic field intensity B collected by the Hall sensor in real time.

[0052] Step 4: Compare the leakage magnetic field strength B with the preset threshold A. If B ≤ A, it is considered qualified and the magnet passes normally; if B > A, it is considered unqualified and an audible and visual alarm is triggered immediately.

[0053] Step S5: After receiving the alarm signal, the operator stops feeding, removes 2 to 6 magnets adjacent to each other before and after the alarm time, and manually retests each magnet using standard testing equipment to accurately locate and remove the weak magnets.

[0054] This detection method pre-calibrates a preset threshold for qualified magnets and calculates the leakage magnetic field strength collected by the Hall sensor in real time during actual testing. The leakage magnetic field strength is compared with the preset threshold to determine whether there are unqualified products. This achieves online full inspection in a continuous arrangement state. At the same time, by removing adjacent magnets after an alarm and performing manual retesting, it achieves rapid and accurate positioning of weak magnetic products. The method is convenient to operate and has high detection efficiency.

[0055] In actual testing, a batch of 10,000 N52 neodymium iron boron magnets (5mm×5mm×2mm) were fully inspected, with 30 weakly magnetic magnets pre-mixed in. The testing method used a magnet movement speed of 100 magnets / second and an alarm threshold difference of 30 Gs. The results showed that all 30 weakly magnetic magnets triggered the alarm, with a maximum difference of 400 Gs and a minimum of 34 Gs. The entire testing process took approximately 100 seconds, with a 100% accuracy rate.

[0056] In actual production, the lateral leakage magnetic field strength of the arrayed magnets is tested, such as... Figure 5 As shown. Segment V1 is the initial segment before the array of magnets enters the detection area. At this time, the first magnet has not yet formed a complete closed loop with the subsequent magnets, and its end face magnetic field leaks to the side, causing the Hall sensor to detect a high leakage magnetic field intensity. As the magnets enter a continuous arrangement, the magnetic field lines gradually form a closed loop inside, and the curve intensity drops rapidly and tends to stabilize. Segment V2 is the weak magnetic defect area. The curve shows a significant sharp peak, which indicates the presence of a weak magnet in the magnet array, causing the magnetic field line closed loop to be broken. The leakage magnetic signal is captured by the Hall sensor and forms an abnormal peak, which is significantly different from the normal baseline, thus enabling rapid identification. Segment V3 is the normal magnet area. The curve is generally stable at an extremely low noise level, indicating that the magnetic field lines of qualified magnets form a complete closed loop inside, with almost no leakage magnetic field and no abnormal peaks. Segment V4 is the end segment of the magnets. The curve intensity rises sharply again. This is the normal signal generated when the magnet array leaves the detection area, the end magnet loses the excitation effect of the subsequent adjacent magnets, and its end face magnetic field is exposed to the outside.

[0057] In summary, this invention can quickly achieve full inspection of neodymium iron boron magnets, has high identification sensitivity for weak magnetic products, and is suitable for large-scale automated production lines.

[0058] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A rapid magnetic field weakening detection device for neodymium iron boron magnets, characterized in that, include: A non-magnetic container for holding magnets arranged in a continuous pattern of alternating N and S poles, wherein the side of the non-magnetic container has an opening for the magnets to be exposed. A PCB board that can be inserted into the socket; A Hall sensor is disposed on the side of the PCB board, and the sensitive direction of the Hall sensor is parallel to the radial direction of the magnet; wherein, when the PCB board is inserted into the socket, the Hall sensor extends through the socket to the outside of the side of the magnet to detect the leakage magnetic intensity on the side of the magnet. The signal processing and alarm unit is electrically connected to the Hall sensor and is used to collect the leakage magnetic field strength detected by the Hall sensor and compare it with the preset threshold. When the leakage magnetic field strength exceeds the preset threshold, an alarm is triggered.

2. The neodymium iron boron magnet rapid magnetic weakening detection device as described in claim 1, characterized in that: The Hall sensor is a linear Hall sensor.

3. The rapid magnetic field weakening detection device for neodymium iron boron magnets as described in claim 1, characterized in that: The non-magnetic container is a mounting base with a 90-degree right-angled inner wall, used to limit the two adjacent sides of the magnet.

4. The rapid magnetic field weakening detection device for neodymium iron boron magnets as described in claim 1, characterized in that: The non-magnetic container is made of PP plastic.

5. The rapid magnetic weakening detection device for neodymium iron boron magnets as described in claim 1, characterized in that: The Hall sensor is provided with a protective shell, and the sensing surface of the Hall sensor is flush with the outer surface of the protective shell; during detection, the outer surface of the protective shell is in close contact with the side of the magnet, and the gap between the Hall sensor and the side of the magnet is 0~0.3mm.

6. A detection method for a rapid magnetic weakening detection device for neodymium iron boron magnets as described in any one of claims 1 to 5, characterized in that, The steps include the following: The magnets to be tested are arranged continuously on a non-magnetic container with alternating N and S poles. The continuously arranged magnets are moved at a constant speed relative to the Hall sensor; The leakage magnetic field strength on the side of the magnet detected by the Hall sensor is acquired in real time. The leakage magnetic field strength is compared with a preset threshold. When the leakage magnetic field strength exceeds the preset threshold, an alarm is triggered to indicate that there is a defective product at the current detection location.

7. A detection method for a rapid magnetic weakening detection device for neodymium iron boron magnets as described in claim 6, characterized in that, The method for setting the preset threshold is as follows: A batch of qualified magnets are arranged continuously with alternating N and S poles; Record the fluctuation range of the Hall sensor's output reading; The maximum value of the fluctuation range is multiplied by a reliability coefficient and set as a preset threshold, wherein the reliability coefficient is 1.1 to 1.

3.

8. A detection method for a rapid magnetic weakening detection device for neodymium iron boron magnets as described in claim 6, characterized in that: When an alarm is triggered, stop feeding, remove 2 to 6 magnets adjacent to the alarm time, and manually retest them using standard testing equipment to locate the defective magnets.

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