Target detection device with high protection performance

Abstract

The invention discloses a target detection device with high protection performance, which comprises a protection shell, a detection coil, an oscillation and signal processing circuit and a target, the detection coil and the oscillation and signal processing circuit are packaged in the protection shell, the target is positioned outside the protection shell, and the protection shell is an all-metal shell; the oscillation and signal processing circuit is configured to drive the detection coil to work at a target oscillation frequency and process a detection signal; if the target oscillation frequency meets the condition, the detection signal intensity of the oscillation and signal processing circuit on the target within the target distance is greater than a set threshold value. According to the scheme, the detection coil is completely sealed in the all-metal protective shell with high mechanical strength, the electromagnetic shielding problem of the metal shell is solved by utilizing the electromagnetic response difference of materials with different conductivity and the selection of the target working frequency, the improvement of the comprehensive performance including protection and detection is realized, and the detection accuracy is improved. The technical contradiction that the protection performance and the detection function are difficult to complete in the traditional scheme is solved.

Description

Technical Field

[0001] This invention belongs to the field of non-contact metrology and testing technology, and particularly relates to a target detection device with high protection performance. Background Technology

[0002] In scenarios such as fluid metering, industrial automated production lines, and equipment operating parameter monitoring, non-contact detection of parameters such as rotational speed, displacement, and position of moving parts is required. These detection scenarios often face harsh environments such as humidity, oil stains, dust corrosion, or mechanical collisions. If the sensing element, as the core of the detection, is directly exposed, it is easily contaminated, worn, or impacted, leading to a decrease in detection accuracy or even failure. Therefore, it is necessary to equip the sensing element with a protective structure.

[0003] Existing protection solutions for metrology and testing equipment are mainly divided into two categories: one category uses non-metallic materials such as plastic to make protective shells. These shells do not block the transmission of electromagnetic and other detection signals and can ensure the normal operation of the detection function. However, they have low mechanical strength, insufficient corrosion resistance and durability, and are prone to aging and damage when exposed to harsh industrial environments for a long time, thus failing to provide reliable physical protection for the sensing elements. The other category uses metallic materials to make protective shells. Metallic shells have excellent mechanical strength, sealing performance and environmental corrosion resistance, which can effectively resist the damage of harsh environments to the internal sensing elements. However, they will form electromagnetic shielding for the detection elements based on the principle of electromagnetic induction, hindering or even completely blocking the coil from sensing external targets, creating a technical contradiction between protection performance and detection function.

[0004] To resolve the aforementioned contradictions, a compromise has been proposed: using metal materials to make the outer shell and replacing the detection surface with non-metallic materials or making windows in the detection surface with shielding material. Although this method ensures the transmission of detection signals to a certain extent, the window structure or the replacement of the detection surface destroys the integrity of the outer shell, significantly weakening the protective performance. In some scenarios requiring high protection, it still cannot meet the long-term and reliable protection requirements, affecting the service life of the detection element. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the prior art by proposing a target detection device with a protective shell that has high protective performance, thereby improving the overall performance of protection and detection, and thus simultaneously meeting the requirements of strength and detection function in target detection scenarios.

[0006] To achieve the above objectives, the present invention adopts the following technical solutions: A target detection device with high protection performance includes a protective housing, a detection coil and oscillation and signal processing circuit encapsulated within the protective housing, and a target located outside the protective housing. The protective casing is an all-metal casing; The oscillation and signal processing circuit is configured to drive the detection coil to operate at the target oscillation frequency and process the detection signal; The target oscillation frequency satisfies a condition such that the intensity of the detection signal of the target within the target distance by the oscillation and signal processing circuit is greater than a set threshold.

[0007] In the aforementioned target detection device with high protection performance, the target is a metal target or an oscillation circuit that is sensitive to oscillation frequency.

[0008] In the aforementioned target detection device with high protective performance, the conductivity of the protective shell is lower than that of the target, so that the change in electromagnetic parameters of the detection coil caused by the target approaching is greater than the change in electromagnetic parameters of the detection coil caused by the protective shell itself.

[0009] In the aforementioned target detection device with high protective performance, the target oscillation frequency is within the following range: f2+80 KHz≥f1≥f2-40 KHz, f1≥10KHz; f1 represents the target oscillation frequency, and f2 represents the specific oscillation frequency; At the specific oscillation frequency, the difference between the change in electromagnetic parameters of the detection coil caused by the target approaching and the change in electromagnetic parameters of the detection coil caused by the protective shell itself is the largest.

[0010] In the aforementioned target detection device with high protective performance, the target oscillation frequency is within the following range: f2+20 KHz≥f1≥f2-20 KHz.

[0011] In the aforementioned target detection device with high protective performance, the conductivity of the protective shell and the conductivity of the target satisfy the following condition: target conductivity ≥ protective shell conductivity × 5.

[0012] In the aforementioned target detection device with high protective performance, the conductivity of the protective shell and the conductivity of the target satisfy the following condition: target conductivity ≥ protective shell conductivity × 10.

[0013] In the aforementioned target detection device with high protective performance, the conductivity of the protective shell is less than 12 MS / m; The conductivity of the target is higher than 30 MS / m.

[0014] In the aforementioned target detection device with high protective performance, the conductivity of the protective shell is less than 2.5 MS / m; The conductivity of the target is higher than 50 MS / m.

[0015] In the aforementioned target detection device with high protective performance, the target distance is 1~10mm; The device is a cylindrical or square probe structure used to detect the target attached to a rotating or linearly moving part.

[0016] The advantages of this invention are as follows: the detection coil is completely sealed in a high-mechanical-strength all-metal protective shell with a protection level of IP68, which can effectively resist moisture, oil, dust corrosion and mechanical impact, and can adapt to extremely harsh industrial testing environments; at the same time, by utilizing the differences in electromagnetic response of materials with different conductivity and by selecting the target operating frequency, the electromagnetic shielding problem of the metal shell is effectively overcome, meeting the detection function requirements of external targets, and the shell detection can be completed without damaging the integrity of the shell, realizing a comprehensive improvement in performance including protection and detection, and solving the technical contradiction of the difficulty in achieving both protection performance and detection function in traditional solutions. Attached Figure Description

[0017] Figure 1 This is a graph showing the influence of two selected materials on the self-inductance of the detection coil within a defined frequency band when designing a target detection device with high protective performance according to the present invention. Figure 2 This is a comparison of the two influence curves of the present invention; Figure 3 This is a schematic diagram of the target detection device with high protection performance of the present invention used for rotation detection and measurement; Figure 4 This is a schematic diagram of the target detection device with high protection performance of the present invention used for linear motion detection and measurement.

[0018] Reference numerals: 1. Detection coil; 2. Oscillation and signal processing circuit; 3. Protective housing; 4. Target; 5. Motion platform. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Example 1

[0020] This solution provides a target detection device with high protection performance, including a protective housing 3, a detection circuit encapsulated within the protective housing 3, the detection circuit including a detection coil 1 and an oscillation and signal processing circuit 2, and a target 4 located outside the protective housing 3.

[0021] The detection coil 1 includes a main coil and 1 to 4 auxiliary coils.

[0022] The oscillation and signal processing circuit 2 is configured to drive the detection coil 1 to operate at the target oscillation frequency and process the detection signal, including: An oscillation circuit is used to generate the target oscillation frequency for driving detection coil 1. The detection circuit is used to detect the change in the oscillation signal of the detection coil 1 caused by the eddy current effect of the target 4. This change in the oscillation signal is caused by the change in the electromagnetic parameters of the detection coil due to the eddy current effect generated when the target approaches. A microcontroller is used to sample the output signal of a detection circuit and convert it into a metering signal output.

[0023] Preferably, the detection coil is custom-made from a PCB board to control the ratio of the coil's self-inductance and the mutual inductance between the main and auxiliary coils, thereby enhancing the magnetic field strength after penetrating the outer casing.

[0024] This solution is based on the principle of electromagnetic induction to achieve metrological detection. The working principle of the magnetic induction sensor is to detect the target by utilizing the eddy current effect and the resonance characteristics of the LC oscillation circuit: after the detection coil inside the detection device is energized with alternating current, it generates an alternating magnetic field. When the target approaches the magnetic field range, eddy currents will be induced on the target surface. The eddy currents will consume the magnetic field energy and change the inductance value of the coil, thereby disrupting the resonance state of the LC circuit, causing the oscillation to weaken or stop. After the oscillation and signal processing circuit 2 of the detection device captures this oscillation change, it converts it into a detection signal output, thereby realizing non-contact detection of metal objects.

[0025] Under this sensing principle, the target has a sensitivity peak to the LC oscillation circuit, which is typically in the megahertz range. Therefore, megahertz-level oscillation frequencies are commonly used. However, in harsh industrial environments, it is desirable to use metal materials to create protective housings to provide high-strength protection for the sensor. Under this sensing principle, if the protective housing is also made of metal, eddy currents will be induced. Furthermore, within a certain range, the higher the oscillation frequency, the more pronounced the eddy current effect of the metal housing. At high frequencies, even metal housings with low conductivity cannot overcome the negative impact of the eddy current effect, and may even fail to transmit the electromagnetic field to the outside, rendering the sensor unusable. To address this, as mentioned in the background section, non-metallic materials are currently used for the detection surface to avoid this effect. However, this significantly reduces the protective performance of the housing, failing to meet the requirements of high-protection scenarios.

[0026] To address this, this solution attempts to use an all-metal casing and abandons the megahertz-level high-frequency band selection for 1-8mm detection scenarios. Simultaneously, through a series of innovative design ideas, it creates a detection device for 1-8mm detection scenarios that overcomes the conflict between protection strength and detection functionality. First, we cleverly utilize the difference in electromagnetic response between materials with different electrical conductivity. We select a material with extremely low electrical conductivity for the outer shell, which is stainless steel in this embodiment, while we select a material with extremely high electrical conductivity for the target, which is copper in this embodiment, thus creating a difference in electromagnetic response between the two.

[0027] Then, a frequency band interval was determined in the following way: We conducted several tests on the attenuation effect of the detection coil at different oscillation frequencies using a full-metal protective shell made of the aforementioned extremely low conductivity material. Since the attenuation is more severe at higher frequencies, we started testing directly from 1 MHz, continuously decreasing the oscillation frequency. After several tests, we selected the upper limit of the frequency band that roughly meets the magnetic permeability requirements. When the detection coil operates at this upper limit frequency, the influence of the full-metal protective shell will not cause the magnetic field strength transmitted to the target detection distance to be less than a certain value. The target at the detection distance can generate an effective eddy current effect under this magnetic field strength. Based on this method, we determined the upper limit of the frequency band to be 500 kHz.

[0028] A detection device based on a target and a non-metallic protective shell is used. The rest of this device is identical to the detection device in this solution, but the shell is replaced with a non-metallic protective shell. Functional testing is performed on this non-metallic protective shell detection device. Since lower frequencies generally result in poorer functionality and make it less likely to meet the detection requirements of the target scenario, this embodiment starts testing at 1kHz and continuously increases the oscillation frequency. After several tests, a lower frequency limit that meets the detection requirements of the target usage scenario is determined. When the detection coil operates at this lower frequency limit, the target can sense the electromagnetic field generated by the detection coil and generate eddy currents, which in turn affect the electromagnetic parameters of the detection coil, thus meeting the detection requirements of the target usage scenario. Based on this method, the lower frequency limit determined is 10kHz.

[0029] Within the frequency band defined by the lower and upper limits, different frequencies were sequentially selected to test the effects of the chosen target and the all-metal protective casing on the self-inductance of the detection coil, and influence curves were generated. Figure 1 and Figure 2 As shown. By comparing the influence curves, the frequency of the maximum difference is determined to be around 50kHz. Significant differences are observed in the range of 20kHz to 130kHz, with the most pronounced differences between 40kHz and 60kHz. Any frequency within this range is preferred, with 60kHz being the preferred target oscillation frequency for the detection device. Thus, a detection device is obtained, comprising a full metal protective shell made of stainless steel, a target made of copper, and a detection circuit with an oscillation frequency of 60kHz.

[0030] This detection device, utilizing a full-metal protective shell made of stainless steel, achieves an IP68 protection rating, enabling it to withstand extremely harsh industrial testing environments and significantly improving its protective performance. It cleverly utilizes the differences in electromagnetic response between materials with varying conductivity. The stainless steel shell, with its relatively low conductivity, controls attenuation and eddy current losses in alternating magnetic fields to a low level, exhibiting a certain degree of transparency to magnetic fields in this frequency band. Simultaneously, the external high-conductivity target generates a relatively strong eddy current effect at this frequency. The difference in eddy current effects is most significant at the target oscillation frequency, improving the signal-to-noise ratio and thus ensuring detection performance. When the target approaches or moves away from the detection coil protected by the shell, the strong eddy current field induced by the target significantly modulates the coil's equivalent impedance parameter, causing changes in the coil parameters. By monitoring these changes in electrical parameters, theoretically, high detection performance can be maintained without compromising the integrity of the shell. This solution applies the aforementioned detection device to the following two example scenarios.

[0031] Scene 1 In this embodiment, the detection device determined above is used for measuring the rotational speed of a rotating shaft.

[0032] like Figure 3 As shown, the detection device in this embodiment is a cylindrical stainless steel probe. The internal detection coil 1 is a specially made PCB coil, consisting of one external main coil and three internal auxiliary coils. The oscillation and signal processing circuit is electrically connected to the detection coil, and both are vacuum-encapsulated in a stainless steel housing with epoxy resin to form a robust integrated structure. A semi-circular copper plate is embedded as a target on the metal rotating shaft to be measured. The detection probe is fixed by a bracket, making its central axis concentric with the target rotation axis, and maintaining a constant 8mm gap between its end face and the target's motion trajectory plane on the rotating shaft.

[0033] Working Process: After the detection probe is connected to the power supply, the oscillation circuit of the circuit operates, and the internal detection coil 1 oscillates intermittently at a frequency of 60kHz. When the central shaft rotates, whenever the copper target passes directly below a secondary coil inside the detection probe, the strong eddy current effect generated by the high conductivity copper target instantly absorbs a large amount of magnetic field energy, causing the oscillation amplitude of that secondary coil to drop sharply. The detection circuit converts the amplitude change of each secondary coil into a specific voltage value. The microcontroller performs AD sampling on each voltage value, and after processing, the number of target rotations can be obtained. By calculating the number of measurements per unit time, the rotational speed of the shaft can also be calculated. Throughout the entire process, the sensitive coil inside the detection device probe is completely protected by the stainless steel shell and is not affected by on-site oil, coolant, or mechanical impact.

[0034] To achieve an oscillation frequency of 60kHz, this solution adjusts the coil and circuit resonance parameters. Table 1 below compares the coil parameters of the conventional device (oscillation frequency 33MHz) with those of this device. Table 1

[0035] This device uses the above coil parameters to achieve the desired 60kHz oscillation frequency. When put into use, the coil parameters and circuit resonance can be further adjusted. It is preferable that the mutual inductance coefficient and self-inductance of the coil are within 20% of the above parameters, and the circuit resonance parameters are adjusted accordingly, as long as the oscillation frequency meets the required target oscillation frequency.

[0036] To avoid random errors, two copies of each device were prepared, and their signal strengths were compared with and without a casing, and with or without a stainless steel casing. The comparison results are shown in Table 2 below. The data in the table represent the detected signal strength, i.e., the signal strength when the target is closer to the corresponding coil than when it is farther away from the coil. Theoretically, the signal of the coil should have a significant difference, generally greater than 20, to be detected by the device. To ensure a margin, a difference of 25 or higher is considered to be able to detect a proximity signal.

[0037] As can be seen from the table below, traditional devices are completely unable to detect proximity signals after using a stainless steel casing, while this device, after using a stainless steel casing, still has a signal strength of more than 30 at a measurement distance of 8.5mm, which fully meets the detection function requirements in the 8mm detection distance scenario.

[0038] Table 2

[0039] Scene 2 In this embodiment, the detection device determined above is used for linear displacement measurement.

[0040] like Figure 4 As shown, in this embodiment, the target 4 consists of multiple copper foils attached to the side of the linear motion platform 5. The detection device is fixed above the platform, parallel to the platform surface, at a distance of 8mm. The internal detection coil is a specially made PCB coil, consisting of one external main coil and one internal secondary coil. The oscillation and signal processing circuit 2 is electrically connected to the detection coil 1. Both are vacuum-encapsulated in a stainless steel housing with epoxy resin, forming a robust integrated structure. When the motion platform 5 moves, each copper foil passes through the probe in sequence, and the probe can detect the arrival and departure of the target. The motion state of the target is detected by counting or measuring the displacement using the amplitude change of the internal secondary coil of the probe. Testing showed that the accuracy of the counting result of this detection device is as high as 100%, and the displacement error is less than 0.1%.

[0041] This linear displacement measuring device is particularly suitable for applications requiring counting or absolute position verification, and all sensing elements are fully protected.

[0042] The target detection device provided in this solution not only has extremely high protection capabilities, but also, due to the specific response of the high conductivity target and the appropriate frequency selection, the detection signal has a high signal-to-noise ratio, thereby achieving strong anti-environmental interference capabilities and reliable metrological detection functions. It can be widely used in occasions that require protected, non-contact counting, such as water meters, packaging machinery, textile machinery, flow meter calibration, etc. Example 2

[0043] This embodiment is similar to Embodiment 1, except that the target in this embodiment uses an oscillation circuit that is sensitive to the oscillation frequency. That is, in this embodiment, the device has two oscillation circuits: one is the oscillation circuit in the detection circuit, and the other is the oscillation circuit used as the target. Example 3

[0044] This embodiment is similar to Embodiment 1, except that this embodiment does not require the conductivity of the protective shell to be less than that of the metal target. It only requires that, at the selected target oscillation frequency, the selection of both satisfies the requirement that the detection signal strength of the oscillation and signal processing circuit 2 for the target within the target distance is greater than a set threshold, such as 25.

[0045] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A target detection device with high protective performance, comprising a protective housing (3), a detection coil (1) and an oscillation and signal processing circuit (2) encapsulated within the protective housing (3), and a target (4) located outside the protective housing (3), characterized in that, The protective outer shell (3) is an all-metal shell; The oscillation and signal processing circuit (2) is configured to drive the detection coil (1) to operate at the target oscillation frequency and process the detection signal; The target oscillation frequency satisfies the condition that the intensity of the detection signal of the oscillation and signal processing circuit (2) to the target (4) within the target distance is greater than the set threshold.

2. The target detection device with high protective performance according to claim 1, characterized in that, The target (4) is a metal target or an oscillation circuit that is sensitive to the oscillation frequency.

3. The target detection device with high protective performance according to claim 2, characterized in that, The conductivity of the protective shell (3) is lower than that of the target (4), so that the change in electromagnetic parameters of the detection coil (1) caused by the target (4) approaching is greater than the change in electromagnetic parameters of the detection coil (1) caused by the protective shell (3) itself.

4. The target detection device with high protective performance according to claim 3, characterized in that, The target oscillation frequency is within the following range: f2+80KHz≥f1≥f2-40KHz, f1≥10KHz; f1 represents the target oscillation frequency, and f2 represents the specific oscillation frequency; At the specific oscillation frequency, the difference between the change in electromagnetic parameters of the detection coil (1) caused by the target (4) approaching and the change in electromagnetic parameters of the detection coil (1) caused by the protective shell (3) itself is the largest.

5. The target detection device with high protective performance according to claim 4, characterized in that, The target oscillation frequency is within the following range: f2+20KHz≥f1≥f2-20KHz.

6. The target detection device with high protective performance according to claim 3, characterized in that, The conductivity of the protective shell (3) and the conductivity of the target (4) satisfy the following condition: the conductivity of the target (4) ≥ the conductivity of the protective shell (3) × 5.

7. The target detection device with high protective performance according to claim 6, characterized in that, The conductivity of the protective shell (3) and the conductivity of the target (4) satisfy the following: the conductivity of the target (4) ≥ the conductivity of the protective shell (3) × 10.

8. The target detection device with high protective performance according to claim 6 or 7, characterized in that, The electrical conductivity of the protective outer shell (3) is less than 12 MS / m; The conductivity of the target (4) is higher than 30 MS / m.

9. The target detection device with high protective performance according to claim 8, characterized in that, The protective outer shell (3) has an electrical conductivity of less than 2.5 MS / m; The conductivity of the target (4) is higher than 50 MS / m.

10. The target detection device with high protective performance according to claim 1, characterized in that, The target distance is 1~10mm; The device is a cylindrical or square probe structure used to detect the target (4) attached to a rotating or linearly moving part.

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