Regenerative braking energy recovery system for electric tool

Abstract

The invention relates to the technical field of energy recovery of electric tools, in particular to a regenerative braking energy recovery system for an electric tool. The system comprises a clutch inner ring and a clutch outer ring which are coaxially assembled, a high-speed generator, a sealing protective shell and an energy recovery circuit. The inner ring is connected with the tool spindle and provided with a bidirectional slope raceway with an inclination angle larger than a friction angle; the shell is fixed by the outer ring through an anti-torsion bracket, and a pre-pressing ball assembly is arranged between raceways; the generator rotor is directly connected with the rear end of the inner ring; the shell integrates labyrinth sealing and forced air cooling; the circuit adopts super capacitor-lithium battery hybrid energy storage. Under the loosening working condition, the ball is wedged into the reverse slope to drive the generator to instantly generate electricity, the energy recovery efficiency of 85% or above is achieved, and meanwhile reliable operation in severe environments such as sand and dust, high and low temperature and the like is guaranteed through an IP67 protection and multi-stage fusing mechanism. The technical defects of large delay, low efficiency and poor environmental adaptability of a traditional scheme are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electric tool energy recovery, and in particular to a regenerative braking energy recovery system for electric tools. BACKGROUND

[0002] Electric tools are widely used in modern industrial production and household work, among which electric drill tools often face reverse load impact in the working conditions of loosening screws and disassembling fasteners. In such operations, the elastic potential energy stored by the connected part is suddenly released, causing the tool spindle (100) to produce violent reverse rotation. The traditional solution usually converts this part of mechanical energy into heat energy dissipation through friction braking, not only causing energy waste, but also accelerating the wear of the braking element. In addition, the traditional regenerative braking scheme has three major defects: large control delay (milliseconds), low power generation efficiency (<40%), and poor environmental adaptability.

[0003] In recent years, regenerative braking technology has emerged to recover energy through built-in motors in electric tools, but there are significant defects in actual application: first, there is a millisecond-level switching delay between the motor generation mode and the control circuit, making it difficult to capture transient reverse impact energy; second, conventional motor winding design focuses on driving performance, with an efficiency of less than 40% in power generation conditions; third, reverse current impact easily causes power device damage, reducing system reliability.

[0004] In addition, existing energy recovery systems perform poorly in harsh conditions such as dust and moisture. Insufficient sealing leads to dust intrusion into the precision transmission structure, and moisture corrosion causes circuit short circuits, severely restricting the application of electric tools in construction sites, field operations, and other scenarios. The design of the energy storage unit also has limitations, and there is a lack of intelligent coordination between supercapacitors and battery packs, with battery life rapidly declining under high-current impact.

[0005] The market urgently needs a technical solution that meets three core requirements: efficient capture of reverse impact energy, stable operation in high-dust and high-humidity environments, and safe storage of transient high-power electrical energy. Existing technologies have not made breakthroughs in this field. SUMMARY

[0006] To overcome the above-mentioned defects of the prior art, embodiments of the present application provide a regenerative braking energy recovery system for electric tools.

[0007] To achieve the above-mentioned purposes, the present application has the following innovations: its structure includes: A clutch for bidirectional torque transmission, including a coaxially assembled inner ring and an outer ring, the inner ring being rigidly connected to the spindle of the electric tool, and the outer ring being fixed to a sealed protective housing; A high-speed generator, the rotor of which is connected to the inner ring of the clutch through a flange plate; The sealed protective shell covers the clutch and the high-speed generator and meets the IP67 protection level; The energy recovery circuit rectifies, optimizes power and charges to the battery for the electrical energy output by the high-speed generator; The control module monitors the clutch speed, the high-speed generator temperature and the battery status in real time.

[0008] Further, the axial length of the outer ring is less than that of the inner ring, the outer circumference of the inner ring is provided with a bidirectional slope raceway, and the rear end is provided with a flange plate connected to the high-speed generator; The inner circumference of the outer ring is provided with a mirror-symmetrical bidirectional slope raceway, and is fixed to the sealed protective shell through a torsion-resistant support; A ball assembly is arranged between the two groups of bidirectional slope raceways; The inclination angle of the bidirectional slope raceway is 6°±0.5°, and the inclination angle is greater than the steel friction angle 5.7°.

[0009] Further, the ball assembly comprises: Silicon nitride ceramic balls with a diameter tolerance of ±0.005mm are accommodated between the bidirectional slope raceways (4) of the inner ring and the outer ring; A phosphor bronze retainer is provided with 12 ball pockets for accommodating the silicon nitride ceramic balls, and the central axis of the ball pockets coincides with the normal axis of the bidirectional slope raceway; A wave spring exerts a pre-pressure in the range of 50N to 80N; A radial elastic clip spring is arranged in an annular clamping groove on the outer circumference of the phosphor bronze retainer, the annular clamping groove is machined at the axial middle position of the outer circumference of the phosphor bronze retainer, and when the elastic clip spring is installed inside the annular clamping groove, the elastic clip spring and the inner circumference of the outer ring form a flexible radial interference or a micro-gap fit; The bidirectional slope raceway comprises a forward slope and a reverse slope which are alternately distributed in a circumferential direction and have a phase difference of 90 degrees.

[0010] Further, the wave spring is an annular spring installed in an annular limiting groove on the inner circumference of the outer ring, the axial symmetry plane of the annular limiting groove coincides with the axial center section of the outer ring, and the axial distance between the groove wall of the annular limiting groove close to the bidirectional slope raceway and the edge of the bidirectional slope raceway is 3mm; The phosphor bronze retainer is axially limited between the wave spring and the limiting boss on the outer circumference of the inner ring, and the ball pockets of the phosphor bronze retainer are provided with a heat expansion compensation gap with a compensation amount of 0.06mm; The limiting boss is located on the inner ring close to the high-speed generator, and the axial distance between the limiting boss and the bidirectional slope raceway is 2mm and the outer diameter of the limiting boss is less than the root diameter of the bidirectional slope raceway by 0.5mm; The axial gap between the limiting boss and the phosphor bronze retainer is 0.1mm.

[0011] Further, the anti-torsion support comprises three groups of 120°-distributed lugs; Each lug is connected to a connecting hole of the sealed protective shell by a shear pin made of 30CrMnSiA quenched steel with an ultimate shear strength of 800 MPa; The shear pin and the connecting hole are in interference fit, with an interference amount of 0.01 mm.

[0012] Further, the rotor of the high-speed generator is rigidly connected to the inner ring through a flange, and six 12.9-grade high-strength bolts and two interference-fitted precision positioning pins are arranged at the connection between the rotor and the flange, respectively. The high-speed generator rotor and the inner ring end face are filled with a heat-conducting silica gel sheet, which extends to the heat dissipation fins of the sealed protective shell. The stator winding adopts a coreless disc structure, and the rotor is axially hollow to form an air duct.

[0013] Further, the sealed protective shell comprises an AlSi7Mg aluminum alloy base with heat dissipation fins and a PA66 engineering plastic upper cover, the thickness of the heat dissipation fins is 0.5 mm, the distance between adjacent heat dissipation fins is 3 mm, and the surface of the heat dissipation fins is plated with nickel; An O-ring is arranged at the joint surface of the aluminum alloy base and the engineering plastic upper cover; A double-lip fluororubber oil seal and a labyrinth seal structure are arranged at the position where the main shaft penetrates the sealed protective shell; The labyrinth seal structure comprises three annular grooves arranged on the main shaft and two polytetrafluoroethylene oil flinger rings, the thickness of the oil flinger rings is 3 mm, and the interference fit with the main shaft is 0.02 mm.

[0014] Further, the sealed protective shell is provided with a centrifugal fan corresponding to the position of the rotor, and the gap between the blades of the centrifugal fan and the outer diameter of the rotor is less than or equal to 2 mm; A metal filter screen is arranged at the inlet and outlet of the air duct, and the mesh diameter of the metal filter screen is 0.3 mm.

[0015] Further, the energy recovery circuit comprises: A three-phase rectifier bridge composed of silicon carbide MOSFET; A bidirectional DC-DC converter with MPPT algorithm; A hybrid energy storage unit of a 20F / 48V super capacitor group and an 18V-54V ternary lithium battery group; A BMS chip integrated with a temperature sensor, an equalization circuit, and an isolation diode.

[0016] Further, the control module performs: SOC estimation algorithm, supporting 20A continuous charging and discharging; When the temperature of the high-speed generator (3) is greater than 85℃, the recovery circuit is cut off; Super capacitor preferentially absorbs > 50A peak current; And according to the main shaft speed to perform hierarchical control: When the main shaft speed is in the range of -500 rpm to 2000 rpm, start energy recovery; When the absolute value of the main shaft speed is greater than 2000 rpm, the energy recovery circuit is cut off; When the main shaft speed is in the range of 0 to 500 rpm, the clutch remains free rotation state.

[0017] The beneficial effects of the present application are: 1. Realize efficient capture of high dynamic reverse energy: The mechanical self-locking structure of the bidirectional ball ramp clutch solves the timeliness and efficiency problem of energy recovery: the mechanical ball ramp design (inclination angle > 5.7° friction angle) automatically switches to power generation mode in 0 milliseconds at the moment of release, overcoming the control delay of traditional motor regenerative braking; the reverse impact energy is transmitted through a rigid direct connection path (main shaft → inner ring → generator rotor), avoiding electromagnetic conversion loss, and the actual energy recovery efficiency is more than 85%; 50-80N waveform spring pre-pressing ensures stable engagement of the ball assembly under high speed working condition, effectively resisting 10,000 rpm centrifugal force impact.

[0018] 2. Break through the reliability bottleneck under harsh working conditions: The sealing-heat dissipation-energy storage collaborative system of the present application solves the failure problem of electric tools in dusty, humid, high and low temperature environments: IP67 sealed protective shell integrates labyrinth seal + forced air cooling system, with dust barrier rate > 99.5% while realizing 85℃ high temperature continuous operation; super capacitor-lithium battery hybrid energy storage unit cooperates to buffer > 50A peak current, avoiding battery damage from large current impact, ensuring energy storage safety at -40℃~85℃ full temperature; 800MPa shear pin overload protection and multi-parameter fusing mechanism make the system's life in extreme conditions such as sand and water increase by 300%. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is the side structure diagram of the whole application.

[0020] Figure 2 is the cross-sectional view of the clutch connected inside the sealed protective shell.

[0021] Figure 3 is an enlarged view of the phosphor bronze retainer.

[0022] Figure 4 is a structure diagram between the phosphor bronze retainer and the inner circumference of the outer ring. DETAILED DESCRIPTION

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] like Figure 1 As shown, the regenerative braking energy recovery system of the present invention comprises: a clutch 1, a high-speed generator 3, and a sealed protective housing 2 enclosing them, all coaxially assembled. The inner ring 11 of the clutch 1 is connected to the spindle 100 of the power tool, and its outer ring 12 is fixed to the housing 2 by an anti-torsion bracket. The rotor 31 of the high-speed generator 3 is directly connected to the rear end of the inner ring 11 through a flange 32. The axial length of the inner ring 11 is significantly greater than that of the outer ring 12. The flange 32 at its rear end extends out of the outer ring 12 and is rigidly connected to the rotor 31 of the high-speed generator 3 by bolts.

[0025] Example 1: Implementation of the mechanical structure of clutch 1 The core mechanical structure of the clutch of this invention and its connection relationship with the housing are as follows: Figure 2 As shown. The clutch 1 consists of an inner ring 11, an outer ring 12, and a ball assembly 6 located therebetween. The outer ring 12 is fixed to the aluminum alloy base 21 of the sealed protective housing 2 by a shear pin 52 on the anti-torsion bracket.

[0026] 1.1 Inner Ring 11 Processing 20CrMnTi alloy steel billet is selected and formed by CNC lathe. 4. External circumferential machining of bidirectional inclined raceway: Forward slope 41 and reverse slope 42 are alternately distributed circumferentially, with a phase difference of 90 degrees. Inclination angle 6.0° ± 0.1° (greater than the friction angle of steel, 5.7°) Surface carburizing and quenching treatment, hardness up to HRC62 Near the generator end, a limiting boss 111 is machined. The height of the limiting boss 111 is 0.5mm, and its axial distance from the inclined raceway is 2.0mm. The outer diameter of the limiting boss 111 is 0.5mm smaller than the root diameter of the ramp raceway. 1.2 Outer Ring 12 Assembly The inner circumference is machined with a mirror-symmetric inclined raceway, with a distance of 3.0 mm from the annular limiting groove 121. Implementation of anti-torsion bracing: Three sets of earpieces 51 are welded to the outer ring 12 at 120° evenly distributed. 30CrMnSiA quenched steel shear pin 52 interference fit (tolerance 0.01mm) Limiting shear strength 800 MPa 1.3 Assembly of ball assembly 6 Step 1: Install wave spring 63 into outer ring 12 annular limiting groove 121; Step 2: Place phosphor bronze retainer 62 (12 ball pockets 621, hole diameter tolerance ±0.003 mm), as shown, the phosphor bronze retainer 62 is an annular member, which is precisely machined with 12 ball pockets 621 for accommodating silicon nitride ceramic balls 61. The central axis of each ball pocket 621 coincides with the normal axis of the bidirectional slope raceway 4 to ensure uniform stress on the balls 61; Figure 3 Step 3: Place 12 silicon nitride ceramic balls 61 (diameter tolerance ±0.005 mm) one by one into the 12 ball pockets 621 of the retainer (diameter tolerance ±0.005 mm) Step 4: Pre-press test (no displacement of balls under 50-80 N pressure) Step 5: Press 65Mn spring steel radial elastic clip spring 64 into retainer annular clamping groove 622 (elastic clip spring 64 wire diameter 0.8 mm, initial pre-tightening force 15 N). Limiting boss 111 and phosphor bronze retainer 62 axial gap 0.1 mm, as shown, the outer circumferential surface of the phosphor bronze retainer 62 is machined with an annular clamping groove 622. After the radial elastic clip spring 64 is pressed into the annular clamping groove 622, the outer diameter of the elastic clip spring 64 in the natural state is slightly larger than the outer diameter of the phosphor bronze retainer 62, so that it forms a slight interference or slight gap fit with the inner wall of the outer ring 12, thereby achieving radial limiting.

[0027] Figure 4

[0028] Wave spring 63 pre-pressing force optimization is 80 N (in the range of 50 N-80 N, ANSYHertz contact stress simulation verification, maximum contact stress of balls ≤750 MPa under 50-80 N pre-pressing force, wave spring 63 pre-pressing force optimization is 80 N (in the range of 50 N-80 N)).

[0029] Comparison test:

[0030] Example 2: Implementation of thermal management and sealing system 2.1 Direct connection structure of high-speed generator 3 High-speed generator 3 rotor 31 is connected to inner ring 11 through flange plate 32: 6 high-strength bolts of grade 12.9 (torque 8 Nm) 2 interference fit precision positioning pins 7 (Φ2H7) Thermal conduction path construction: 0.5 mm thermal conductive silicone sheet 71 fills the interface between rotor 31 and inner ring 11​​ Thermal conductive silica gel sheet 71 extends to aluminum alloy base 21 heat dissipation fins 72 (AlSi7Mg aluminum alloy).

[0031] Rotor 31 is axially hollow to form air duct 8 2.2 Forced air cooling system Centrifugal fan 101 implementation: Number of blades: 12 titanium alloy fan blades Installation position: sealed protective shell 2 corresponding to rotor 31 section Blade-rotor 31 gap 1.8±0.2mm Air duct 8 protection: Inlet and outlet set 304 metal (stainless steel) filter screen 102 (mesh Φ0.3mm) Dustproof efficiency 99.5% (ISO12103-A3 test) The air flow path of the forced air cooling system is as follows: the cooling air flow is sucked in by the metal filter screen 102 at the inlet under the drive of the centrifugal fan 101, flows through the air duct 8 formed by the hollow of the rotor 31, carries heat to the heat dissipation fins 72 of the aluminum alloy base 21, and is finally discharged from the gap between the heat dissipation fins 72, forming an effective directional cooling cycle.

[0032] 2.3 Sealed protection implementation Labyrinth seal structure 9: Main shaft 100 is provided with 3 annular grooves 91 (depth 1.5mm, width 2mm) Two polytetrafluoroethylene oil throwing rings 92 (thickness 3mm, interference 0.02mm) are assembled Sealed protective shell 2 sealing: Aluminum alloy base 21 and engineering plastic upper cover 22 are provided with fluororubber O-shaped sealing ring 81 Double-lip fluororubber 82 oil seal (temperature resistance -40~150℃) is used at the penetration of main shaft 100 Labyrinth seal structure 9 and double-lip fluororubber 82 oil seal are sequentially arranged from the outside to the inside at the aperture of main shaft 100 penetrating the sealed protective shell 2, labyrinth seal structure 9 as the first level of protection, double-lip fluororubber 82 oil seal as the second level of protection, together constituting an IP67 level shaft end sealing system.

[0033] Example 3: Energy recovery control implementation 3.1 Circuit topology implementation Energy recovery path: High-speed generator 3→ silicon carbide MOSFET rectifier bridge→ MPPT bidirectional DC-DC converter→ hybrid energy storage unit Hybrid energy storage unit composition: Super capacitor bank: 20F / 48V (absorbing >50A peak current) Ternary lithium battery bank: 18V-54V adaptive (supporting 20A continuous discharge) Isolation diode prevents current backflow 3.2 Control strategy execution The rotational speed staging control strategy enables the system to achieve 85% energy recovery efficiency within the 2000 rpm threshold, while eliminating the timing conflict between the 8000 rpm over-speed protection and reverse power generation in traditional solutions.

[0034] The control module performs rotational speed staging management: 1. Reverse power generation mode: -2000rpm ≤ n ≤ -500rpm.

[0035] 2. Positive torque transmission: 500rpm ≤ n ≤ 2000rpm.

[0036] 3. Over-speed protection: |n| > 2000rpm, |n| > 2000rpm cutoff test: continuous trigger 50 times over-speed protection, system response time ≤ 2ms.

[0037] 4. Free rotation: -500rpm < n < 500rpm.

[0038] Safety protection mechanism:

[0039] Experimental data: Test results on 12V lithium electric drill:

[0040] Note: Sand and dust environment continuous operation: traditional tools average 2 hours after being stuck due to dust invasion (n=5); the invention works continuously for 8 hours without failure (n=5).

[0041] Electric tool test table:

[0042] System working principle Stage 1: Drilling operation (energy consumption) The user pulls the trigger, and the main shaft 100 rotates forward The ball wedges into the forward slope 41, and the inner and outer rings 12 are locked Torque through inner ring 11 → main shaft 100 → drill output Stage 2: Release braking (energy recovery) 1. The screw is disconnected and the connected part rebounds elastically 2. The main shaft 100 is impacted by reverse torque (> 50Nm) 3. Ball wedge into reverse slope 42, push the inner ring 11 reverse rotation 4. Inner ring 11 drive high-speed generator 3 rotor 31 power generation Stage 3: Energy storage Generator output three-phase alternating current Rectifier bridge conversion to direct current MPPT algorithm tracking maximum power point Super capacitor absorbs peak current after conversion to lithium battery Stage 4: System protection Temperature sensor real-time monitoring generator temperature rise Speed sensor detects clutch 1 overspeed Abnormal state trigger circuit fuse mechanism Implementation risk prompt 1. Thermal expansion control: silicon nitride ball (α=3.2×10⁻ 6 / ℃) and phosphor bronze retainer 62 (α=18×10⁻ 6 / ℃) need to reserve 0.06mm thermal compensation gap;

[0043] 2. Machining precision requirement: spindle 100 journal needs to meet IT4 level precision (GB / T1800.2), double-lip oil seal interference amount 0.02mm.

[0044] Industrial applicability The system has been applied to: Dongcheng DCJZ1200 electric drill (mass production model).

[0045] Bosch GBH18V impact drill (OEM customization).

[0046] Field rescue tool set (military grade).

[0047] Finally, it should be pointed out that in the description of the present application, it should be pointed out that unless otherwise specified and limited, the terms "installation", "connection", "connection" should be understood broadly, which can be mechanical connection or electrical connection, or the communication between two elements, or direct connection, "up", "down", "left", "right" and the like are only used to indicate the relative positional relationship, when the absolute position of the described object changes, the relative positional relationship may change; Secondly: the drawings of the disclosed embodiments of the present application only involve the structures involved in the disclosed embodiments, other structures can refer to the usual design, and in the case of no conflict, the same embodiment and different embodiments of the present application can be combined with each other; Finally: the above only describes the preferred embodiments of the present application and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A regenerative braking energy recovery system for power tools, characterized in that, Its structure includes: The clutch for bidirectional torque transmission includes an inner ring and an outer ring coaxially mounted. The inner ring is rigidly connected to the spindle of the power tool, and the outer ring is fixed to a sealed protective housing. A high-speed generator, the rotor of which is connected to the inner ring of the clutch via a flange; The sealed protective housing covers the clutch and high-speed generator and meets the IP67 protection rating. The energy recovery circuit rectifies, optimizes, and recharges the electrical energy output from the high-speed generator back into the battery. The control module monitors clutch speed, high-speed generator temperature, and battery status in real time.

2. The regenerative braking energy recovery system for power tools according to claim 1, characterized in that, The axial length of the outer ring is less than the axial length of the inner ring. The outer circumference of the inner ring is provided with a bidirectional inclined raceway, and the rear end is provided with a flange for connecting a high-speed generator. The outer ring has a mirror-symmetrical bidirectional inclined raceway on its inner circumference, and is fixed to the sealed protective shell by an anti-torsion bracket; A ball bearing assembly is provided between the two sets of bidirectional inclined raceways; The inclination angle of the bidirectional inclined roller track is 6°±0.5°, and this inclination angle is greater than the steel friction angle of 5.7°.

3. A regenerative braking energy recovery system for power tools according to claim 2, characterized in that, The ball assembly includes: Silicon nitride ceramic balls with a diameter tolerance of ±0.005mm are housed between the bidirectional inclined raceway (4) of the inner and outer rings; The phosphor bronze cage has 12 ball pockets for holding the silicon nitride ceramic balls. The central axis of the ball pockets coincides with the normal axis of the bidirectional ramp raceway. A wave spring, wherein the preload applied by the wave spring is in the range of 50N to 80N; A radial elastic retaining ring is disposed in an annular groove on the outer circumference of the phosphor bronze cage. The annular groove is machined at the axial middle position of the outer circumference of the phosphor bronze cage. When the elastic retaining ring is installed inside the annular groove, the elastic retaining ring and the inner circumference of the outer ring form a flexible radial contact or micro-gap fit. The bidirectional ramp includes forward and reverse ramps that are circumferentially alternating and have a 90-degree phase difference.

4. A regenerative braking energy recovery system for power tools according to claim 3, characterized in that, The wave spring is a ring spring, which is installed in a ring-shaped limiting groove on the inner circumference of the outer ring. The axial symmetry plane of the ring-shaped limiting groove coincides with the axial center section of the outer ring, and the axial distance between the groove wall of the ring-shaped limiting groove on the side near the bidirectional inclined raceway and the edge of the bidirectional inclined raceway is 3mm. The phosphor bronze retainer is axially limited between the wave spring and the limiting boss on the outer circumference of the inner ring. The diameter of the ball pocket of the phosphor bronze retainer is reserved for thermal expansion compensation gap, with a compensation amount of 0.06mm. The limiting boss is located on the inner ring near the high-speed generator end, 2mm away from the bidirectional inclined raceway and its outer diameter is 0.5mm smaller than the root diameter of the bidirectional inclined raceway. The axial clearance between the limiting boss and the phosphor bronze cage is 0.1 mm.

5. A regenerative braking energy recovery system for power tools according to claim 2, characterized in that, The anti-torsion bracket includes three sets of 120° evenly distributed ear seats; Each lug is connected to the connection hole of the sealing protective shell by a shear pin made of 30CrMnSiA quenched steel with an ultimate shear strength of 800MPa. The shear pin and the connecting hole are fitted with an interference fit of 0.01 mm.

6. A regenerative braking energy recovery system for power tools according to claim 1, characterized in that, The rotor of the high-speed generator is rigidly connected to the inner ring via a flange. The connection between the rotor and the flange is provided with six 12.9 grade high-strength bolts and two interference fit precision locating pins. The high-speed generator rotor is filled with a thermally conductive silicone sheet between itself and the inner ring end face, and the thermally conductive silicone sheet extends to the heat dissipation fins (72) of the sealed protective shell. The stator winding adopts a coreless disc structure, and the rotor is axially hollow to form an air duct.

7. A regenerative braking energy recovery system for power tools according to claim 6, characterized in that, The sealed protective housing includes an AlSi7Mg aluminum alloy base with heat dissipation fins and a PA66 engineering plastic top cover. The thickness of the heat dissipation fins is 0.5 mm, the spacing between adjacent heat dissipation fins is 3 mm, and the surface of the heat dissipation fins is nickel plated. The mating surfaces of the aluminum alloy base and the engineering plastic cover are provided with O-ring seals. The main shaft is provided with a double-lip fluororubber oil seal and a labyrinth seal structure at the point where it passes through the sealed protective housing. The labyrinth seal structure includes three annular grooves and two polytetrafluoroethylene (PTFE) oil slingers on the spindle. The oil slingers are 3 mm thick and are interference-fitted with the spindle with an interference tolerance of 0.02 mm.

8. A regenerative braking energy recovery system for power tools according to claim 6, characterized in that, A centrifugal fan is installed at the rotor position corresponding to the sealed protective housing, and the gap between the blades of the centrifugal fan and the outer diameter of the rotor is less than or equal to 2 mm. The air duct is equipped with metal filters at its inlet and outlet, and the mesh diameter of the metal filters is 0.3 mm.

9. A regenerative braking energy recovery system for power tools according to claim 1, characterized in that, The energy recovery circuit includes: A three-phase rectifier bridge composed of silicon carbide MOSFETs; Bidirectional DC-DC converter with MPPT algorithm; Hybrid energy storage unit consisting of a 20F / 48V supercapacitor pack and an 18V-54V ternary lithium battery pack; The BMS chip integrates a temperature sensor, equalization circuit, and isolation diode.

10. A regenerative braking energy recovery system for power tools according to claim 9, characterized in that, The control module executes: SOC estimation algorithm, supporting 20A continuous charge and discharge; The recovery circuit is disconnected when the high-speed generator temperature exceeds 85℃. Supercapacitors preferentially absorb peak currents greater than 50A; Furthermore, it performs graded control based on the spindle speed: Energy recovery is activated when the spindle speed is in the range of -500rpm to 2000rpm. When the absolute value of the spindle speed exceeds 2000 rpm, the energy recovery circuit is cut off. When the spindle speed is in the range of 0 to 500 rpm, the clutch remains in a free-rotating state.

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