A lawnmower

Abstract

The application discloses a mower and belongs to the technical field of mowing equipment. The mower comprises a vehicle body, a cutter head rotatably arranged at the lower part of the vehicle body, and a driving structure arranged in the vehicle body. The driving structure comprises a rotating shaft, and the driving structure drives the cutter head to rotate through the rotating shaft. A plurality of blades are arranged on the cutter head, the blades are made of magnetizable material, and an electromagnet assembly, a sensor array and a demagnetization assembly are sequentially arranged around the rotating shaft in a first direction at the bottom of the vehicle body. The electromagnet assembly is used for applying a pulse magnetic field to the blades below the electromagnet assembly to instantaneously magnetize the blades. The sensor array is used for detecting the magnetic flux leakage signals of the blades below the sensor array. The demagnetization assembly is used for applying a directionally decaying magnetic field to the blades below the demagnetization assembly to demagnetize the magnetized blades. The electromagnet assembly can magnetize the blades, and the problem that the blades are demagnetized during collision with stones and the sensor array cannot detect the blades is avoided.

Description

Technical Field

[0001] This invention relates to the field of lawn mowing equipment technology, and more specifically, to a lawn mower. Background Technology

[0002] With the continuous growth in demand for urban greening and home gardening, lawnmowers, as core equipment for lawn maintenance, have seen their performance, efficiency, and reliability become key indicators for measuring product competitiveness. Traditional lawnmowers are mostly driven by internal combustion engines, which, while powerful, suffer from drawbacks such as high emissions, noise, and frequent maintenance. In recent years, electric lawnmowers powered by batteries have rapidly gained popularity due to their advantages such as zero emissions, low noise, and simple structure.

[0003] A search revealed that Chinese patent CN219938973U discloses a lawnmower robot and its cutting assembly. This device uses a first magnet installed on the blade disc of the cutting assembly to magnetize the first blade, and a corresponding first magnetic induction detection module on the protective cover to detect the magnetic field generated by the magnetized first blade and changes in the magnetic field. The first blade detection signal output by the module can monitor the abnormal state of the first blade. The first magnet does not affect the lawnmower function of the first blade itself, and the first magnetic induction detection module is not affected by natural light. Furthermore, its detection structure is not affected by dirt such as grass clippings and mud generated in the working environment of the lawnmower robot, which greatly improves the compatibility of the lawnmower robot with the working environment and the stability of the blade state detection data.

[0004] In the above-mentioned technical solution, the magnet is mounted on the blade. However, during the rotation of the blade, there is a risk of it hitting a rock, causing the magnet to be impacted, detach from the blade, and demagnetize. This affects the distribution of the magnetic field on the blade and hinders the detection of the blade's condition. In view of this, we propose a lawnmower. Summary of the Invention

[0005] 1. Technical problems to be solved

[0006] The purpose of this invention is to provide a lawnmower to solve the problems mentioned in the background art.

[0007] 2. Technical Solution

[0008] This invention is achieved through the following technical solution:

[0009] A lawnmower includes a vehicle body, a blade disc rotatably mounted on the lower part of the vehicle body, and a drive structure inside the vehicle body. The drive structure includes a rotating shaft, and the drive structure drives the blade disc to rotate via the rotating shaft.

[0010] The cutter head is provided with multiple blades, which are made of magnetizable material. The blades rotate around the pivot in a first direction. The bottom of the vehicle body is provided with an electromagnet assembly, a sensor array and a demagnetizing assembly in sequence around the pivot in the first direction. The electromagnet assembly is used to apply a pulsed magnetic field to the blade below it, so that the blade is instantly magnetized. The sensor array is used to detect the leakage magnetic signal of the blade below it. The demagnetizing assembly is used to apply a directional decaying magnetic field to the blade below it, so as to demagnetize the magnetized blade.

[0011] As an optional solution to the technical solution in this application, the blade is made of high-carbon steel or martensitic stainless steel with coercivity Hc≤2.0kA / m and saturation magnetization Bs≥1.6T.

[0012] As an optional solution to the technical solution in this application, the residual magnetism of the blade after demagnetization is ≤5mT.

[0013] As an optional solution to the technical solution in this application, the angle between the line where the electromagnet assembly and the rotating shaft are located and the forward direction of the vehicle body is between 90° and 270°.

[0014] As an optional solution to the technical solution in this application, the electromagnet assembly includes:

[0015] C-shaped silicon steel core, with a distance of 1–2 mm between the pole piece and the blade surface;

[0016] Copper enameled wire coil, inductance 1.5–2.5mH, peak current 3–5A, pulse width 50–100ms.

[0017] As an optional solution to the technical solution in this application, the sensor array consists of 3–4 tunnel magnetoresistive sensors arranged in a 5mm linear array, with a sampling frequency ≥1MHz and a sensitivity ≥5mV / V / Oe.

[0018] As an optional solution to the technical solution of this application, the demagnetizing component includes:

[0019] H-bridge driver, used to generate reverse exponentially decaying current;

[0020] , ;

[0021] In the formula, I0 is the initial current amplitude, e is the base of the natural logarithm, and τ is the time constant;

[0022] Current sampling resistor and operational amplifier are used for real-time closed-loop control of the attenuation curve endpoint;

[0023] A tunnel magnetoresistive sensor is used to verify that the residual magnetism of the blade is <5mT.

[0024] As an optional solution to the technical solution in this application, the angle between the electromagnet assembly and the sensor array relative to the rotating shaft is smaller than the angle between two adjacent blades relative to the rotating shaft.

[0025] As an optional solution to the technical solution in this application, the angle between the sensor array and the demagnetizing component relative to the rotating shaft is smaller than the angle between two adjacent blades relative to the rotating shaft.

[0026] 3. Beneficial effects

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] 1) This application can magnetize the blade by setting an electromagnet component, thus avoiding the problem that the blade will demagnetize during the collision with the stone, which would prevent the sensor array from detecting the blade.

[0029] 2) By setting up a demagnetizing component, this application can demagnetize the magnetized electromagnet, avoid the blade from adsorbing iron filings and forming a parasitic magnetic field; it can also avoid the magnetic fields of two adjacent blades from superimposing each other, which would have an adverse effect on the sensor array's detection of the blade's status. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the overall structure of a lawnmower.

[0031] Figure 2 This is a schematic diagram of the bottom structure of a lawnmower;

[0032] In the diagram: 1. Car body; 2. Cutter head; 201. Blade; 3. Rotary shaft; 4. Electromagnet assembly; 5. Sensor array; 6. Demagnetizing assembly. Detailed Implementation

[0033] The technical solution of the present invention will now be clearly and completely described in conjunction with the accompanying drawings.

[0034] Please see Figure 1 and Figure 2 The present invention provides a lawnmower, including a body 1, a blade disc 2 rotatably mounted on the lower part of the body 1, and a drive structure inside the body 1, the drive structure including a rotating shaft 3, the drive structure driving the blade disc 2 to rotate through the rotating shaft 3;

[0035] The cutter head 2 is provided with multiple blades 201, which are made of magnetizable material. The blades 201 rotate around the rotating shaft 3 in a first direction. The bottom of the vehicle body 1 is provided with an electromagnet assembly 4, a sensor array 5 and a demagnetizing assembly 6 in sequence around the rotating shaft 3 in the first direction. The electromagnet assembly 4 is used to apply a pulsed magnetic field to the blades 201 below it, so that the blades 201 are instantly magnetized. The sensor array 5 is used to detect the leakage magnetic signal of the blades 201 below it. The demagnetizing assembly 6 is used to apply a reverse decaying magnetic field to the blades 201 below it, so as to demagnetize the magnetized blades 201.

[0036] In this scheme, the drive structure drives the cutter head 2 to rotate via the rotating shaft 3. When the leading edge of the blade 201 enters 1-2mm below the electromagnet assembly 4, it immediately outputs a 12V PWM pulse of 100ms to magnetize the blade 201. The magnetized blade 201 will move to the area below the sensor array 5. If the blade 201 has cracks or gaps, the magnetic flux will leak at the defect and be captured by the sensor array 5. After the detection is completed, the blade 201 will move to the area below the demagnetizing assembly 6 and be demagnetized by a reverse decaying magnetic field to prevent the blade 201 from adsorbing iron filings and forming a "parasitic magnetic field" that would cause pulse cycle disorder.

[0037] As a preferred embodiment of this application, the blade 201 is made of high carbon steel or martensitic stainless steel with coercivity Hc≤2.0kA / m and saturation magnetization Bs≥1.6T, and the residual magnetism of the blade 201 after demagnetization is ≤5mT.

[0038] As a preferred embodiment of this application, the electromagnet assembly 4 includes:

[0039] The C-shaped silicon steel core has a distance of 1–2 mm between its pole piece and the surface of the blade 201;

[0040] Copper enameled wire coil, inductance 1.5–2.5mH, peak current 3–5A, pulse width 50–100ms.

[0041] The C-shaped silicon steel core concentrates magnetic flux, which can generate an instantaneous field strength of 200kA / m (≈250mT) in the blade 201 region, causing the material to reach technical saturation (Bs≥1.6T) along the hysteresis loop.

[0042] Since the pulse width of electromagnet assembly 4 is 50-100ms, in order to ensure that only one blade 201 is magnetized at any given time, the rotational speed of blade 201 needs to be limited. For different numbers of blades 201, the rotational speed can be set with reference to the table below:

[0043] Table 1: Correspondence between Number of Blades and Rotation Speed

[0044]

[0045] In this application, the number of blades 201 is set to two. When performing magnetization detection on the blades 201, it is necessary to reduce the rotation speed of the blades 201 to 300 rpm. In order to avoid the detection process affecting the function of the lawnmower, this application can automatically execute the function of limiting the rotation speed of the blades 201 through the program during the lawnmower's turning or position adjustment, limiting the rotation speed of the blades 201 to 300 rpm, so that the blades 201 can be successfully magnetized.

[0046] As a preferred embodiment of this application, the sensor array 5 consists of 3–4 tunnel magnetoresistive sensors arranged in a 5mm linear array, with a sampling frequency ≥1MHz and a sensitivity ≥5mV / V / Oe.

[0047] If the blade has cracks or notches, magnetic flux leaks at the defect, creating a spatial magnetic field gradient ΔB ≥ 0.1mT. 3–4 TMR sensors continuously collect 50 data points at a sampling rate of 1MHz, covering a blade width of 5mm; the output voltage V_out ∝ ΔB. The MCU performs an FFT on the 50 points, extracting high-frequency components from 5–20kHz; if the amplitude exceeds the reference +3σ, it is determined to be a crack and the blade number is recorded.

[0048] As a preferred embodiment of this application, the demagnetizing component 6 includes:

[0049] H-bridge driver, used to generate reverse exponentially decaying current;

[0050] , ;

[0051] In the formula, I0 is the initial current amplitude, e is the base of the natural logarithm, and τ is the time constant;

[0052] A 0.1Ω current sampling resistor and an operational amplifier are used for real-time closed-loop control of the attenuation curve endpoint;

[0053] A tunnel magnetoresistive sensor is used to verify that the residual magnetism of the blade is <5mT.

[0054] Apply reverse current I0 to the H-bridge The magnetic flux density is 2A, and decays exponentially, so that the magnetic flux density of blade 201 smoothly returns to zero along the second quadrant of the hysteresis loop. When blade 201 leaves the demagnetization zone, the residual magnetism is <5mT, avoiding the superposition of magnetic fields between adjacent blades and the attraction of iron filings.

[0055] In a preferred embodiment of this application, the angle between the straight line containing the electromagnet assembly 4 and the rotating shaft 3 and the forward direction of the vehicle body 1 is between 90° and 270°. This reduces the risk of demagnetization caused by the magnetized blade 201 colliding with a stone.

[0056] In a preferred embodiment of this application, the angle between the electromagnet assembly 4 and the sensor array 5 relative to the rotating shaft 3 is smaller than the angle between two adjacent blades 201 relative to the rotating shaft 3, and the angle between the sensor array 5 and the demagnetizing assembly 6 relative to the rotating shaft 3 is smaller than the angle between two adjacent blades 201 relative to the rotating shaft 3. In this embodiment, two adjacent blades 201 will not be magnetized simultaneously, thus avoiding the superposition of magnetic fields of adjacent blades 201 and the occurrence of spurious pulses.

Claims

1. A lawnmower, characterized in that: Includes a car body (1), the lower part of which is rotatably provided with a cutter head (2), and the inside of the car body (1) is provided with a drive structure, the drive structure including a rotating shaft (3), the drive structure drives the cutter head (2) to rotate through the rotating shaft (3); The cutter head (2) is provided with multiple blades (201), which are made of magnetizable material. The blades (201) rotate around the rotating shaft (3) in a first direction. The bottom of the vehicle body (1) is provided with an electromagnet assembly (4), a sensor array (5) and a demagnetizing assembly (6) in sequence around the rotating shaft (3) in the first direction. The electromagnet assembly (4) is used to apply a pulsed magnetic field to the blades (201) below it to magnetize the blades (201) instantaneously. The sensor array (5) is used to detect the leakage magnetic signal of the blades (201) below it. The demagnetizing assembly (6) is used to apply a direction-attenuating magnetic field to the blades (201) below it to demagnetize the magnetized blades (201). The residual magnetism of the blade (201) after demagnetization is ≤5mT; The demagnetizing component (6) includes: H-bridge driver, used to generate reverse exponentially decaying current; ， ； In the formula, I0 is the initial current amplitude, e is the base of the natural logarithm, and τ is the time constant; A current sampling resistor (0.1Ω) and an operational amplifier are used to control the endpoint of the decay curve in real time closed loop control. A tunnel magnetoresistive sensor is used to verify that the residual magnetism of the blade is <5mT.

2. A lawnmower according to claim 1, characterized in that: The blade (201) is made of high carbon steel or martensitic stainless steel with coercivity Hc≤2.0kA / m and saturation magnetization Bs≥1.6T.

3. A lawnmower according to claim 1, characterized in that: The angle between the straight line where the electromagnet assembly (4) and the rotating shaft (3) are located and the forward direction of the vehicle body (1) is between 90° and 270°.

4. A lawnmower according to claim 1, characterized in that: The electromagnet assembly (4) includes: C-shaped silicon steel core, with a distance of 1–2 mm between the pole piece and the surface of the blade (201); Copper enameled wire coil, inductance 1.5–2.5mH, peak current 3–5A, pulse width 50–100ms.

5. A lawnmower according to claim 1, characterized in that: The sensor array (5) consists of 3–4 tunnel magnetoresistive sensors arranged in a 5mm linear array, with a sampling frequency ≥1MHz and a sensitivity ≥5mV / V / Oe.

6. A lawnmower according to claim 1, characterized in that: The angle between the electromagnet assembly (4) and the sensor array (5) relative to the rotating shaft (3) is smaller than the angle between the two adjacent blades (201) relative to the rotating shaft (3).

7. A lawnmower according to claim 1, characterized in that: The angle between the sensor array (5) and the demagnetizing component (6) relative to the rotating shaft (3) is smaller than the angle between the two adjacent blades (201) relative to the rotating shaft (3).

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