A back electromotive force detection circuit for a brushless motor controller for an automotive cooling fan

Abstract

This invention discloses a back EMF detection circuit for a brushless motor controller used in automotive cooling fans, relating to the field of motor technology. Key technical features include a stator with a rotor rotatably connected to its center. A circuit board is mounted on the top of the stator, and a miniature coil is mounted on the circuit board. A lubrication device is rotatably connected to the center of the rotor. The circuit board also integrates a back EMF detection circuit, which includes a signal sampling unit, a filtering and shaping unit, and a comparison and judgment unit connected in sequence. The miniature coil is electrically connected to the output of the back EMF detection circuit. When the comparison and judgment unit detects a back EMF signal indicating that the rotor is in an inertial rotation or driven by airflow, it triggers the miniature coil to operate. This invention accurately identifies recoverable kinetic energy states through the back EMF detection circuit, converting the mechanical energy of wind-driven or inertial rotation into control signals to drive the lubrication, heat dissipation, and dust removal systems in synergy.

Description

Technical Field

[0001] This invention relates to the field of motor technology, specifically to a back EMF detection circuit for a brushless motor controller used in automotive cooling fans. Background Technology

[0002] In automotive engine cooling systems, brushless motor-driven cooling fans are widely used due to their advantages such as high efficiency, long lifespan, and maintenance-free operation.

[0003] However, in actual operation, especially under high temperature, high load or frequent start-stop conditions, the motor bearings are prone to wear due to the softening and loss of lubricating grease caused by heat, which can lead to motor jamming or even failure.

[0004] Traditional solutions often rely on regular maintenance or the addition of external lubrication devices, which not only increases costs but also consumes more energy.

[0005] The published patent CN214045348U discloses a compact structure for a brushless motor and drive controller, as well as a brushless electric drill. The compact structure includes a brushless motor, connecting wires, and a drive controller. The brushless motor is horizontally mounted above the rear end of the drive controller. The brushless motor has a cable tray, and the drive controller's circuit board has a through hole. The line connecting the centers of the cable tray and the through hole is perpendicular to the axis of the brushless motor, and the cable tray is located directly below the rotor shaft of the brushless motor. One end of the connecting wire passes through the cable tray and is electrically connected to the brushless motor, while the other end passes through the through hole and is electrically connected to the drive controller. This patent places the brushless motor above the rear end of the drive controller, and the connecting wire directly passes through the cable tray and through hole to connect to the drive controller, thereby reducing the length of the connecting wire and achieving a compact structure design for the brushless motor and drive controller, saving space and shortening the length of the electric drill. However, it is difficult to avoid the problem of grease loss at the bearings under high temperature, high load, or frequent start-stop conditions, leading to increased motor power loss and reduced service life.

[0006] Therefore, a new type of control circuit that automatically triggers lubrication and maintenance actions is needed to improve motor reliability and achieve energy saving and consumption reduction. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a back EMF detection circuit for a brushless motor controller for an automotive cooling fan, solving the problems mentioned in the background section.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution: a back EMF detection circuit for a brushless motor controller for an automotive cooling fan, comprising an upper housing, a lower housing, a stator, a bearing assembly one, and a bearing assembly two, wherein a rotor is rotatably connected to the middle of the stator, a circuit board is provided on the top of the stator, a miniature coil is provided on the circuit board, and a lubrication device is rotatably connected to the middle of the rotor; The circuit board also integrates a back EMF detection circuit, which includes a signal sampling unit, a filtering and shaping unit, and a comparison and judgment unit connected in sequence. The micro coil is electrically connected to the output terminal of the back EMF detection circuit. When the comparison and judgment unit detects a back EMF signal indicating that the rotor is in an inertial rotation or driven by airflow, it triggers the micro coil to be energized. The rotor includes a magnet mounting frame and a storage compartment for storing lubricating grease. The lubrication device includes a guide shaft and a synchronous transmission groove. A lubrication channel is provided in the middle of the guide shaft, and a lubrication conveying channel is provided on one side of the lubrication channel. The lubrication channel, the lubrication conveying channel, and the storage chamber are connected. The lubrication delivery channel and the connection point of the lubrication channel are provided with a blocking block. The blocking block is provided with a blocking ball. When the guide shaft rotates, the blocking ball is disengaged from the lubrication delivery channel and the lubrication channel by centrifugal force. A lubrication controller is provided on the outside of the rotor, and the lubrication controller is used to control the synchronous transmission of the rotor and the lubrication device; When the car's cooling fan rotates due to inertia after shutdown, the electricity generated by its kinetic energy recovery drives the micro coil to work and controls the lubrication controller, so that the rotor and lubrication device rotate synchronously. This causes the ball to break free from the blockage of the lubrication channel under centrifugal force, allowing the grease to flow into bearing assembly one and bearing assembly two.

[0009] According to the above technical solution, the signal sampling unit is electrically connected to any phase winding of the brushless motor and is used to collect the back EMF signal generated by the phase winding when the rotor rotates. The filtering and shaping unit is used to filter out high-frequency noise and shape the back EMF signal into a smooth waveform. The comparison and judgment unit is used to compare the shaped back EMF signal with a preset threshold and output a speed judgment signal.

[0010] According to the above technical solution, a hollow shaft is provided at the top of the magnet mounting frame, and a lubrication device is rotatably connected to the hollow shaft, the lubrication device passing through the magnet mounting frame; The storage compartment is set inside the magnet mounting frame, a push plate is slidably connected inside the storage compartment, a bearing frame is fixedly connected to the bottom of the storage compartment, and a spring is provided between the bearing frame and the push plate. The bearing bracket has a second bearing assembly fixedly connected to its inner side, and the inner side of the second bearing assembly is fixedly connected to the lower housing.

[0011] According to the above technical solution, a second spring is provided on the side of the ball block away from the lubrication channel, and the ball block blocks the connection between the lubrication delivery channel and the lubrication channel under the action of the second spring. A synchronous transmission groove is provided on the top outer side of the guide shaft; The guide shaft has an input hole on its outer side, which is connected to the lubrication delivery channel, and the lubrication delivery channel is connected to the storage compartment through the input hole; The lubrication controller includes a control bushing and a guide channel. The guide channel is opened on a hollow shaft, and a synchronizing ball is slidably connected inside the guide channel. A control sleeve is slidably connected to the outer side of the hollow shaft, and a V-shaped groove is provided on the control sleeve at the position corresponding to the synchronizing ball.

[0012] According to the above technical solution, a centrifugal fan is fixedly connected to the bottom of the rotor, and the centrifugal fan is coaxial with the lower housing.

[0013] According to the above technical solution, a filter ventilation device is provided at the bottom of the lower housing. The filter ventilation device is used to cool the stator and rotor and filter the air. The filtration and ventilation device includes a protective shell, a filter screen, and an air inlet. The filter screen is located at the bottom of the protective shell and is eccentrically positioned. An air inlet is provided at the bottom of the protective shell. The negative pressure space of the centrifugal fan during operation intersects with the filter screen and the air inlet.

[0014] According to the above technical solution, an air vent is provided on the top outer side of the protective shell, and the air force generated by the centrifugal fan is discharged from bottom to top through the air vent.

[0015] According to the above technical solution, the filter screen is rotatably connected to the bottom of the protective shell, and a gear is fixedly connected to the inner side of the filter screen; The filter screen is provided with a partition plate, which divides the filter screen into a filtration area and a cleaning area. The filtration area is connected to the filter screen, and the cleaning area is located at the axis of the protective shell. A wind-gathering shell is installed in the cleaning area to guide the wind force. The bottom of the protective shell is provided with a dust discharge channel, which is intersected with the cleaning area of ​​the filter screen.

[0016] According to the above technical solution, a dust removal device is provided at the bottom of the guide shaft, and a vent is provided on the guide shaft; The bottom of the dust removal device is rotatably connected to a second gear, and an annular groove is provided between the second gear and the guide shaft. The annular groove is connected to the vent hole. A support ring plate is fixed inside the annular groove. The support ring plate is fixedly connected to the guide shaft. A friction transmission plate is provided between the support ring plate and the second gear. The friction transmission plate is slidably connected to the guide shaft and is in contact with the guide shaft. A strip-shaped connecting part is fixedly connected between the support ring plate and the friction transmission plate. A counterweight is provided in the middle of the strip-shaped connecting part. A spring is provided between the support ring plate and the friction transmission plate; A fan is fixedly connected to the end of the friction transmission plate; The fan is located inside the air-collecting housing in the cleaning area.

[0017] According to the above technical solution, a high-temperature lubrication device is provided at the bottom of the bearing assembly 1. The high-temperature lubrication device is used for active lubrication. The high-temperature lubrication device includes a heat-conducting ring, which is fixedly connected to the bottom of the bearing assembly 1. The heat-conducting ring is used to conduct heat. A memory spring is sleeved between the heat-conducting ring and the control bushing.

[0018] This invention provides a back EMF detection circuit for a brushless motor controller used in automotive cooling fans. It offers the following advantages: This invention, by integrating a back EMF detection circuit on the circuit board, can accurately identify the effective kinetic energy state of the cooling fan when the car is traveling at high speed driven by airflow or when it rotates due to inertia after stopping. It only triggers the micro coil to work under such conditions, driving the lubrication controller to make the rotor and the lubrication device rotate synchronously, so that the grease is injected into the bearing assembly. This avoids the dry friction problem caused by the softening and loss of grease due to high temperature in traditional motors, significantly improving energy utilization efficiency and saving energy and reducing consumption.

[0019] This invention conducts heat to the memory spring through a heat-conducting ring at the bottom of the bearing assembly, causing the spring to stretch and push the control bushing downwards. This also triggers the lubrication controller to activate the lubrication process, achieving active protection under high-temperature conditions. This forms a dual protection system of kinetic energy-driven lubrication and temperature-triggered lubrication, effectively coping with harsh conditions such as high temperature and high load, and significantly extending the service life of the motor.

[0020] This invention utilizes a centrifugal fan at the bottom of the rotor that rotates synchronously with the rotor, creating a negative pressure zone inside the protective casing. This draws in external air through the filter and air inlet, flows through the gap between the stator and rotor, carries away heat, and is then discharged through the air outlet. This achieves active heat dissipation for the core components of the motor and the circuit board above. In addition, when the guide shaft rotates, the dust cleaning device at its bottom is also activated. At high speed, the fan draws airflow through the vent and blows it back onto the filter surface, expelling dust through the dust discharge channel. At low speed, insufficient centrifugal force causes the friction transmission plate to press against the gear under the action of spring three, engaging the gear and rotating the filter to switch cleaning areas, thus achieving self-cleaning.

[0021] This invention can complete the entire process of sensing, judging and executing without the need for additional power supply, external sensors or complex control logic, thereby improving reliability and achieving true energy saving and consumption reduction. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the overall unfolded structure of the present invention; Figure 3 This is a schematic diagram of the overall lower shell structure of the present invention; Figure 4 This invention as a whole Figure 2 A schematic diagram of the bottom structure; Figure 5 This invention as a whole Figure 3 A schematic diagram of the structure of area A; Figure 6 This invention as a whole Figure 2 A schematic diagram of the structure of region C; Figure 7 This invention as a whole Figure 1 A schematic diagram of a half-section of the structure; Figure 8 This is a schematic diagram of a half-section of the integral rotor of the present invention; Figure 9 This invention as a whole Figure 8 A structural diagram of area B; Figure 10 This is a half-sectional structural diagram of the overall lubrication device of the present invention.

[0023] In the diagram: 1. Upper shell; 2. Lower housing; 201. Protective shell; 202. Air outlet; 203. Dust exhaust channel; 204. Filter screen; 205. Air inlet; 206. Partition plate; 207. Gear 1; 208. Air concentrator shell; 3. Rotor; 301. Hollow shaft; 302. Magnet mounting bracket; 303. Push plate; 304. Storage compartment; 305. Bearing bracket; 306. Spring 1; 4. Lubrication device; 401. Guide shaft; 402. Lubrication channel; 403. Input hole; 404. Synchronous transmission groove; 405. Blocking block; 406. Ball stop; 407. Spring 2; 408. Lubrication conveying channel; 409. Vent hole; 5. Dust removal device; 501. Friction transmission plate; 502. Strip-shaped connecting part; 503. Spring three; 504. Gear two; 505. Fan; 506. Support ring plate; 6. High-temperature lubrication device; 601. Heat-conducting ring; 602. Memory spring; 7. Lubrication controller; 701. Control bushing; 702. Synchronizing ball; 703. V-groove; 704. Guide channel; 8. Bearing assembly 1; 9. Bearing assembly 2; 10. Stator; 11. Circuit board; 12. Centrifugal fan; 13. Miniature coil. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0025] Please see Figure 1-10 A back EMF detection circuit for a brushless motor controller for an automotive cooling fan includes an upper housing 1, a lower housing 2, a stator 10, a bearing assembly 8, a bearing assembly 9, a rotor 3 rotatably connected to the middle of the stator 10, a circuit board 11 on the top of the stator 10, a miniature coil 13 on the circuit board 11, and a lubrication device 4 rotatably connected to the middle of the rotor 3. The circuit board 11 also integrates a back EMF detection circuit, which includes a signal sampling unit, a filtering and shaping unit, and a comparison and judgment unit connected in sequence. The miniature coil 13 is electrically connected to the output terminal of the back EMF detection circuit. When the comparison and judgment unit detects a back EMF signal indicating that the rotor 3 is in an inertial rotation or driven by airflow, the miniature coil 13 is triggered to be energized. Rotor 3 includes a magnet mounting frame 302 and a storage chamber 304, the storage chamber 304 being used to store lubricating grease; The lubrication device 4 includes a guide shaft 401 and a synchronous transmission groove 404. A lubrication channel 402 is provided in the middle of the guide shaft 401, and a lubrication conveying channel 408 is provided on one side of the lubrication channel 402. The lubrication channel 402, the lubrication conveying channel 408, and the storage chamber 304 are connected. A blocking block 405 is provided at the connection between the lubrication conveying channel 408 and the lubrication channel 402. A blocking ball 406 is provided inside the blocking block 405. When the guide shaft 401 rotates, the blocking ball 406 is disengaged from the lubrication conveying channel 408 and the lubrication channel 402 by centrifugal force. A lubrication controller 7 is provided on the outside of the rotor 3. The lubrication controller 7 is used to control the synchronous transmission of the rotor 3 and the lubrication device 4. When the car's cooling fan rotates due to inertia after shutdown, the electric power generated by its kinetic energy recovery drives the micro coil 13 to work and controls the lubrication controller 7, so that the rotor 3 and the lubrication device 4 rotate synchronously. This causes the ball stop 406 to break free from the blockage of the lubrication channel 402 under centrifugal force, allowing the grease to flow into the bearing assembly 8 and the bearing assembly 9.

[0026] Furthermore, the lubrication channel 402 is connected to bearing assembly 8 and bearing assembly 9.

[0027] Furthermore, a stator 10 is fixedly connected inside the lower housing 2, and a rotor 3 is rotatably connected to the middle of the stator 10.

[0028] Furthermore, a bearing assembly 8 is provided on the top outer side of rotor 3, and a bearing assembly 9 is provided on the bottom inner side of rotor 3.

[0029] Furthermore, both bearing assembly 8 and bearing assembly 9 are double bearings, and there is a gap between the two bearings. A through hole is opened at the position of the rotor 3 in the gap and it is connected to the lubrication channel 402.

[0030] Furthermore, the back EMF detection circuit is integrated on the same circuit board 11 and shares a common ground with the motor drive control module to avoid signal interference.

[0031] Furthermore, the preset threshold is set according to the back EMF amplitude corresponding to 10%–30% of the motor's rated speed to ensure that lubrication action is triggered only during effective rotation.

[0032] During operation, when the car is traveling at high speed, the cooling fan rotates with the high-speed airflow, or continues to rotate due to inertia after the cooling fan stops. This generates a back EMF signal in the windings of the stator 10. This signal is sampled, filtered, and compared by the back EMF detection circuit on the circuit board 11. Once the circuit confirms that the rotor 3 is in an effective rotational state, a control signal is output to drive the micro coil 13. Under the action of the lubrication controller 7, the rotor 3 and the lubrication device 4 rotate synchronously. At this time, the ball bearing 406 inside the guide shaft 401 disengages from the lubrication device 4 under centrifugal force. When the connecting channels of the lubrication conveying channel 408 and the lubrication channel 402 are blocked, the grease in the storage chamber 304 enters the lubrication channel 402 through the lubrication conveying channel 408 and then enters the bearing assembly 8 and the bearing assembly 9. This avoids the problem of the grease easily softening and being lost due to high temperature when the motor is running at high speed, under high load and high temperature conditions, which would lead to bearing wear. This improves the service life of the motor. At the same time, the high-speed airflow during high-speed driving and the kinetic energy of the cooling fan after shutdown are recovered and used for bearing lubrication of the motor, thereby achieving the purpose of energy saving and consumption reduction.

[0033] The signal sampling unit is electrically connected to any phase winding of the brushless motor to collect the back EMF signal generated by that phase winding when the rotor 3 rotates. The filtering and shaping unit is used to filter out high-frequency noise and shape the back EMF signal into a smooth waveform. The comparison and judgment unit is used to compare the shaped back EMF signal with a preset threshold and output a speed judgment signal.

[0034] A hollow shaft 301 is provided on the top of the magnet mounting bracket 302. A lubrication device 4 is rotatably connected to the hollow shaft 301 and passes through the magnet mounting bracket 302. Storage compartment 304 is installed inside magnet mounting frame 302. Push plate 303 is slidably connected inside storage compartment 304. Bearing frame 305 is fixedly connected to the bottom of storage compartment 304. Spring 306 is installed between bearing frame 305 and push plate 303. Bearing assembly 9 is fixedly connected to the inner side of bearing bracket 305, and the inner side of bearing assembly 9 is fixedly connected to the lower housing 2.

[0035] Furthermore, a connecting hole is provided in the intersecting area between the magnet mounting rack 302 and the storage compartment 304.

[0036] In use, the push plate 303, supported by the spring 306, presses against the storage chamber 304, causing the grease to be forced into the lubrication delivery channel 408.

[0037] A second spring 407 is provided on the side of the ball block 406 away from the lubrication channel 402. Under the action of the second spring 407, the ball block 406 blocks the connection between the lubrication delivery channel 408 and the lubrication channel 402. A synchronous transmission groove 404 is provided on the top outer side of the guide shaft 401; An input hole 403 is provided on the outer side of the guide shaft 401. The input hole 403 is connected to the lubrication delivery channel 408, and the lubrication delivery channel 408 is connected to the storage chamber 304 through the input hole 403. Furthermore, the lubrication delivery channels 408 are eccentrically arranged, and the number is not less than 2.

[0038] In use, when the guide shaft 401 rotates synchronously with the rotor 3, the stop ball 406 in the blocking block 405 is subjected to centrifugal force and moves away from the axis of the guide shaft 401, compressing the second spring 407. At this time, the stop ball 406 disengages from blocking the connection between the lubrication delivery channel 408 and the lubrication channel 402. When the rotation speed of the guide shaft 401 is insufficient to counteract the elastic force of the second spring 407, the stop ball 406 re-blocks the channel under the support of the second spring 407.

[0039] Lubrication controller 7 includes control bushing 701 and guide channel 704. The guide channel 704 is opened on hollow shaft 301, and a synchronizing ball 702 is slidably connected inside the guide channel 704. A control sleeve 701 is slidably connected to the outer side of the hollow shaft 301, and a V-shaped groove 703 is provided on the control sleeve 701 at the position corresponding to the synchronizing ball 702.

[0040] Furthermore, a magnetic ring is provided at the bottom of the control sleeve 701. When the micro coil 13 is working, the magnetic ring is repulsed and pushes the control sleeve 701 to slide upward as a whole.

[0041] In use, by controlling the bushing 701 to slide under external force, the synchronizing ball 702 is pushed by the V-shaped groove 703 and slides towards the lubrication device 4, and finally gets stuck in the synchronizing transmission groove 404, thereby driving the guide shaft 401 to rotate synchronously with the rotor 3. When the control sleeve 701 is not under force, the hollow shaft 301 will rotate, causing the synchronizing ball 702 to slide radially outward under the action of centrifugal force and disengage from the synchronizing transmission groove 404.

[0042] A centrifugal fan 12 is fixedly connected to the bottom of the rotor 3, and the centrifugal fan 12 is coaxial with the lower housing 2.

[0043] A filter ventilation device is provided at the bottom of the lower housing 2. The filter ventilation device is used to cool the stator 10 and rotor 3 and filter the air. The filtration and ventilation device includes a protective shell 201, a filter screen 204, and an air inlet 205. The filter screen 204 is located at the bottom of the protective shell 201 and is eccentrically positioned. An air inlet 205 is provided at the bottom of the protective shell 201. The negative pressure space of the centrifugal fan 12 during operation intersects with the filter screen 204 and the air inlet 205.

[0044] An air vent 202 is provided on the top outer side of the protective shell 201. The air force generated by the centrifugal fan 12 is discharged from bottom to top through the air vent 202.

[0045] The filter screen 204 is rotatably connected to the bottom of the protective shell 201, and a gear 207 is fixedly connected to the inner side of the filter screen 204. A partition plate 206 is provided inside the filter screen 204, which divides the filter screen 204 into a filtration area and a cleaning area. The filtration area is connected to the filter screen 204, and the cleaning area is located at the axis of the protective shell 201. A wind-gathering shell 208 is installed in the cleanup area to guide the wind force; The bottom of the protective shell 201 is provided with a dust discharge channel 203, which is interspersed with the cleaning area of ​​the filter screen 204.

[0046] Furthermore, since the circuit board 11 is positioned higher than the air outlet 202, the airflow generated by the centrifugal fan 12, as it flows from bottom to top and exits through the air outlet 202, simultaneously cools the circuit board 11.

[0047] In use, the rotation of rotor 3 drives centrifugal fan 12 to rotate, and a negative pressure area is generated in the middle of centrifugal fan 12, so that the air outside the protective shell 201 flows into the protective shell 201 through filter screen 204 and gear 207, and flows upward through the gap between stator 10 and rotor 3 inside the protective shell 201, thereby cooling stator 10 and rotor 3, and is discharged through air outlet 202 at the top of the protective shell 201.

[0048] Meanwhile, the incoming air is filtered by filter 204, which prevents dust from accumulating inside the protective shell 201 and thus affecting the overall service life of the motor.

[0049] A dust removal device 5 is provided at the bottom of the guide shaft 401, and a vent hole 409 is provided on the guide shaft 401; The bottom of the dust removal device 5 is rotatably connected to a gear 504. An annular groove is provided between the gear 504 and the guide shaft 401. The annular groove is connected to the vent 409. A support ring plate 506 is fixed inside the annular groove. The support ring plate 506 is fixedly connected to the guide shaft 401. A friction transmission plate 501 is provided between the support ring plate 506 and the gear 504. The friction transmission plate 501 is slidably connected to the guide shaft 401 and contacts the guide shaft 401. A strip-shaped connecting part 502 is fixedly connected between the support ring plate 506 and the friction transmission plate 501. A counterweight is provided in the middle of the strip-shaped connecting part 502. A spring 503 is provided between the support ring plate 506 and the friction transmission plate 501; A fan 505 is fixedly connected to the end of the friction transmission plate 501; Fan 505 is located inside the air collection housing 208 in the cleaning area.

[0050] Furthermore, the arrangement of the strip-shaped connecting part 502, the support ring plate 506, and the friction transmission plate 501 ensures that the second gear 504 rotates synchronously only when the synchronous transmission groove 404 rotates at low speed. This prevents the second gear 504 from rotating at high speed with the guide shaft 401, which would cause the first gear 207 meshing with it to wear faster and thus affect the overall service life.

[0051] When in use, when the car is traveling at high speed, the high speed of the car drives the cooling fan to rotate, and the rotor 3, lubrication controller 7, circuit board 11 and micro coil 13 drive the guide shaft 401 to rotate. At this time, the guide shaft 401 drives the fan 505 to rotate, drawing the air at the top of the hollow shaft 301 downward through the vent 409 and blowing it in the opposite direction to clean the obstructions on the surface of the filter screen 204. At this time, the backflowing airflow is discharged through the dust exhaust channel 203 and is carried away by the high-speed airflow when the car is traveling at high speed, so as to avoid being captured by the filter area of ​​the filter screen 204. When the cooling fan speed decreases to a certain value, the centrifugal force generated by the rotation of the strip connection 502 cannot counteract the elastic squeezing force applied by the spring 3 503 to the friction transmission plate 501. The guide shaft 401 synchronously drives the gear 2 504 to rotate, and synchronously drives the gear 1 207 to rotate, so as to clean the filter surface of different areas of the filter screen 204.

[0052] A high-temperature lubrication device 6 is provided at the bottom of the bearing assembly 8. The high-temperature lubrication device 6 is used for active lubrication. The high-temperature lubrication device 6 includes a heat-conducting ring 601, which is fixedly connected to the bottom of the bearing assembly 8. The heat-conducting ring 601 is used to conduct heat. A memory spring 602 is sleeved between the heat-conducting ring 601 and the control shaft sleeve 701.

[0053] When in use, when the cooling fan operates at high speed for a long time, the operating temperature of bearing assembly 8 increases with the operating time. When the temperature reaches a certain value, the heat is conducted to the memory spring 602 through the heat conduction ring 601, causing the memory spring 602 to push the control sleeve 701 to move down. Under the operation of the lubrication controller 7, the rotor 3 and the lubrication device 4 work synchronously, allowing the grease to flow into bearing assembly 8 and bearing assembly 9, actively preventing bearing assembly 8 and bearing assembly 9 from operating at high temperatures for a long time.

[0054] Working principle: When the car is traveling at high speed, the external airflow drives the cooling fan to rotate, or after the motor is powered off and stopped, the cooling fan continues to rotate due to inertia. Under these two conditions, the rotor 3 of the brushless motor continues to rotate, which causes the back EMF signal to be generated in the winding of the stator 10. This signal is processed by the back EMF detection circuit integrated on the circuit board 11. First, the original back EMF signal is collected from any phase winding through the signal sampling unit. Then, the high-frequency noise is filtered out and shaped into a smooth waveform by the filtering and shaping unit. Finally, the comparison and judgment unit compares the signal with a preset threshold. When a valid rotation state is detected, the comparison and judgment unit outputs a trigger signal to drive the micro coil 13 to work. When the miniature coil 13 is energized, it generates a magnetic field, which exerts a repulsive force on the magnetic ring above it, pushing the control sleeve 701 in the lubrication controller 7 to slide upward. The V-shaped groove 703 on the inner side of the control sleeve 701 then squeezes the synchronous ball 702, causing it to slide inward along the guide channel 704 and get stuck in the synchronous transmission groove 404 of the lubrication device 4, thereby realizing the synchronous rotation of the rotor 3 and the guide shaft 401. As the guide shaft 401 rotates, the retaining ball 406 inside it overcomes the elastic force of the second spring 407 under the action of centrifugal force and moves radially outward, releasing the blockage at the connection between the lubrication delivery channel 408 and the lubrication channel 402. At the same time, under the continuous pressure of the push plate 303 and the first spring 306, the grease in the storage chamber 304 flows into the lubrication channel 402 through the input hole 403 and the lubrication delivery channel 408, and enters the double bearing gap through the through hole between the bearing group 8 and the second bearing group 9, completing automatic lubrication.

[0055] Meanwhile, the centrifugal fan 12 at the bottom of rotor 3 rotates synchronously with the rotor, creating a negative pressure zone inside the protective shell 201. This causes external air to be drawn in through the filter 204 and air inlet 205, flowing through the gap between stator 10 and rotor 3, carrying away heat, and then being discharged through air outlet 202. This achieves active heat dissipation for the core components of the motor and the circuit board 11 above. In addition, when the guide shaft 401 rotates, its bottom dust cleaning device 5 is also activated. At high speed, the fan 505 draws airflow through the vent 409 and blows it in the opposite direction onto the surface of the filter 204. Dust is discharged through the dust discharge channel 203. At low speed, insufficient centrifugal force causes the friction transmission plate 501 to press against the gear 2 504 under the action of spring 3 503, causing it to mesh with gear 1 207, rotating the filter 204, switching cleaning areas, and achieving self-cleaning. Meanwhile, when the bearing temperature rises abnormally due to prolonged high-load operation, the heat-conducting ring 601 at the bottom of bearing assembly 8 conducts heat to the memory spring 602, causing it to stretch due to heat and push the control sleeve 701 to move down, which also triggers the lubrication controller 7 to activate the lubrication process and achieve active protection under high-temperature conditions.

[0056] In summary, this invention accurately identifies recoverable kinetic energy states through a back EMF detection circuit, converting the mechanical energy of wind-driven or inertial rotation into control signals to drive the lubrication, heat dissipation, and dust removal systems to work in tandem. It achieves self-lubrication of bearings, self-cooling of motors, and self-cleaning of filters without the need for an external power source, effectively solving the problems of grease loss and bearing wear under high temperature and high load conditions. This significantly improves the reliability and service life of brushless motors, while also achieving energy recovery and energy saving.

[0057] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A back EMF detection circuit for a brushless motor controller for an automotive cooling fan, comprising an upper housing (1), a lower housing (2), a stator (10), a bearing assembly one (8), and a bearing assembly two (9), characterized in that: The stator (10) is rotatably connected to the middle of the rotor (3), the top of the stator (10) is provided with a circuit board (11), the circuit board (11) is provided with a miniature coil (13), and the middle of the rotor (3) is rotatably connected with a lubrication device (4). The circuit board (11) also integrates a back EMF detection circuit, which includes a signal sampling unit, a filtering and shaping unit and a comparison and judgment unit connected in sequence. The micro coil (13) is electrically connected to the output terminal of the back EMF detection circuit. When the comparison and judgment unit detects a back EMF signal indicating that the rotor (3) is in an inertial rotation or driven by airflow, it triggers the micro coil (13) to be energized. The rotor (3) includes a magnet mounting frame (302) and a storage chamber (304) for storing grease; The lubrication device (4) includes a guide shaft (401) and a synchronous transmission groove (404). A lubrication channel (402) is provided in the middle of the guide shaft (401), and a lubrication conveying channel (408) is provided on one side of the lubrication channel (402). The lubrication channel (402), the lubrication conveying channel (408), and the storage bin (304) are connected. A blocking block (405) is provided at the connection between the lubrication conveying channel (408) and the lubrication channel (402). A blocking ball (406) is provided inside the blocking block (405). When the guide shaft (401) rotates, the blocking ball (406) is disengaged from the lubrication conveying channel (408) and the lubrication channel (402) by centrifugal force. A lubrication controller (7) is provided on the outside of the rotor (3), and the lubrication controller (7) is used to control the synchronous transmission of the rotor (3) and the lubrication device (4).

2. The back EMF detection circuit for a brushless motor controller for an automotive cooling fan according to claim 1, characterized in that: The signal sampling unit is electrically connected to any phase winding of the brushless motor and is used to collect the back EMF signal generated by the phase winding when the rotor (3) rotates. The filtering and shaping unit is used to filter out high-frequency noise and shape the back EMF signal into a smooth waveform. The comparison and judgment unit is used to compare the shaped back EMF signal with a preset threshold and output a speed judgment signal.

3. The back EMF detection circuit for a brushless motor controller for an automotive cooling fan according to claim 1, characterized in that: The top of the magnet mounting bracket (302) is provided with a hollow shaft (301), and a lubrication device (4) is rotatably connected to the hollow shaft (301). The lubrication device (4) passes through the magnet mounting bracket (302). The storage compartment (304) is installed inside the magnet mounting frame (302). A push plate (303) is slidably connected inside the storage compartment (304). A bearing frame (305) is fixedly connected to the bottom of the storage compartment (304). A spring (306) is provided between the bearing frame (305) and the push plate (303). The bearing bracket (305) has a bearing assembly two (9) fixedly connected to its inner side, and the inner side of the bearing assembly two (9) is fixedly connected to the lower housing (2).

4. The back EMF detection circuit for a brushless motor controller for an automotive cooling fan according to claim 1, characterized in that: A second spring (407) is provided on the side of the ball block (406) away from the lubrication channel (402). Under the action of the second spring (407), the ball block (406) blocks the connection between the lubrication delivery channel (408) and the lubrication channel (402). A synchronous transmission groove (404) is provided on the top outer side of the guide shaft (401). The guide shaft (401) has an input hole (403) on its outer side. The input hole (403) is connected to the lubrication delivery channel (408). The lubrication delivery channel (408) is connected to the storage chamber (304) through the input hole (403).

5. The back EMF detection circuit for a brushless motor controller for an automotive cooling fan according to claim 1, characterized in that: The lubrication controller (7) includes a control bushing (701) and a guide channel (704). The guide channel (704) is opened on the hollow shaft (301), and a synchronizing ball (702) is slidably connected inside the guide channel (704). The hollow shaft (301) is slidably connected to a control bushing (701), and a V-shaped groove (703) is provided on the control bushing (701) at the position corresponding to the synchronizing ball (702).

6. The back EMF detection circuit for a brushless motor controller for an automotive cooling fan according to claim 1, characterized in that: A centrifugal fan (12) is fixedly connected to the bottom of the rotor (3), and the centrifugal fan (12) is coaxial with the lower housing (2); The bottom of the lower housing (2) is provided with a filter ventilation device, which is used to cool the stator (10) and rotor (3) and filter the air. The filtration and ventilation device includes a protective shell (201), a filter screen (204), and an air inlet (205). The filter screen (204) is located at the bottom of the protective shell (201) and is eccentrically positioned. An air inlet (205) is provided at the bottom of the protective shell (201). The negative pressure space of the centrifugal fan (12) during operation intersects with the filter screen (204) and the air inlet (205). The protective shell (201) has an air outlet (202) on its top outer side. The wind generated by the centrifugal fan (12) is discharged from bottom to top through the air outlet (202).

7. The back EMF detection circuit for a brushless motor controller for an automotive cooling fan according to claim 6, characterized in that: The filter screen (204) is rotatably connected to the bottom of the protective shell (201), and a gear (207) is fixedly connected to the inner side of the filter screen (204). The filter screen (204) is provided with a partition plate (206), which divides the filter screen (204) into a filtration area and a cleaning area. The filtration area is connected to the filter screen (204), and the cleaning area is located at the axis of the protective shell (201). A wind-gathering shell (208) is provided in the cleaning area, which is used to guide the wind force; The bottom of the protective shell (201) is provided with a dust discharge channel (203), which is intersected with the cleaning area of ​​the filter screen (204).

8. The back EMF detection circuit for a brushless motor controller for an automotive cooling fan according to claim 7, characterized in that: A dust removal device (5) is provided at the bottom of the guide shaft (401), and a vent hole (409) is provided on the guide shaft (401). The bottom of the dust removal device (5) is rotatably connected to a gear two (504), and an annular groove is provided between the gear two (504) and the guide shaft (401), and the annular groove is connected to the vent hole (409); A support ring plate (506) is fixed inside the annular groove. The support ring plate (506) is fixedly connected to the guide shaft (401). A friction transmission plate (501) is provided between the support ring plate (506) and the second gear (504). The friction transmission plate (501) is slidably connected to the guide shaft (401). The friction transmission plate (501) is in contact with the guide shaft (401). A strip-shaped connecting part (502) is fixedly connected between the support ring plate (506) and the friction transmission plate (501). A counterweight is provided in the middle of the strip-shaped connecting part (502). A spring (503) is provided between the support ring plate (506) and the friction transmission plate (501); A fan (505) is fixedly connected to the end of the friction transmission plate (501); The fan (505) is located inside the air-collecting shell (208) of the cleaning area.

9. The back EMF detection circuit for a brushless motor controller for an automotive cooling fan according to claim 5, characterized in that: The bearing assembly (8) is provided with a high-temperature lubrication device (6) at its bottom. The high-temperature lubrication device (6) is used for active lubrication. The high-temperature lubrication device (6) includes a heat-conducting ring (601). The heat-conducting ring (601) is fixedly connected to the bottom of the bearing assembly (8). The heat-conducting ring (601) is used to conduct heat. A memory spring (602) is sleeved between the heat-conducting ring (601) and the control bushing (701).

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