A regenerative braking energy recovery system for power tools

Abstract

This invention relates to the field of energy recovery technology for power tools, specifically a regenerative braking energy recovery system for power tools. The system includes coaxially mounted inner and outer clutch rings, a high-speed generator, a sealed protective housing, and an energy recovery circuit. The inner ring connects to the tool spindle and features a bidirectional inclined raceway with an angle greater than the friction angle. The outer ring is fixed to the housing by an anti-torsion bracket, and pre-loaded ball bearing assemblies are installed between the raceways. The generator rotor is directly connected to the rear end of the inner ring. The housing integrates a labyrinth seal and forced air cooling. The circuit uses a supercapacitor-lithium battery hybrid energy storage system. Under disengagement conditions, the ball bearings wedge into the reverse inclined ramp, driving the generator to generate electricity instantaneously, achieving an energy recovery efficiency of over 85%. Simultaneously, IP67 protection and a multi-stage fuse mechanism ensure reliable operation in harsh environments such as sandstorms and extreme temperatures. This system overcomes the technical shortcomings of traditional solutions, including large delays, low efficiency, and poor environmental adaptability.

Description

Technical Field

[0001] This invention relates to the field of power tool energy recovery technology, and more particularly to a regenerative braking energy recovery system for power tools. Background Technology

[0002] Power tools are widely used in modern industrial production and household chores. Among them, electric drills often face reverse load impacts when loosening screws or disassembling fasteners. In such operations, the elastic potential energy stored in the connected parts is suddenly released, causing the tool spindle (100) to rotate violently in the opposite direction. Traditional solutions usually use friction braking to convert this mechanical energy into heat energy for dissipation. This not only wastes energy but also accelerates the wear of braking components. Furthermore, traditional regenerative braking schemes have three major drawbacks: large control delay (millisecond level), low power generation efficiency (<40%), and poor environmental adaptability.

[0003] Regenerative braking technology, which has emerged in recent years, attempts to recover energy through the built-in motor of power tools, but its practical application has significant drawbacks: First, there is a millisecond-level switching delay between the motor's power generation mode and the control circuit, making it difficult to capture instantaneous reverse impact energy; second, conventional motor winding designs focus on driving performance, and their efficiency is less than 40% under power generation conditions; third, reverse current surges can easily damage power devices and reduce system reliability.

[0004] Furthermore, existing energy recovery systems perform poorly under harsh conditions such as dust and humidity. Insufficient sealing allows dust to penetrate the precision transmission structure, and moisture corrosion can cause short circuits, severely limiting the application of power tools in construction sites, field operations, and other similar scenarios. The design of the energy storage unit also has limitations; the lack of intelligent coordination between the supercapacitor and the battery pack leads to a sharp decline in battery life under high current surges.

[0005] The market urgently needs a technological solution that can simultaneously meet three core requirements: efficient capture of reverse impact energy, stable operation in high-dust and high-humidity environments, and safe storage of instantaneous high-power electrical energy. Existing technologies have not yet achieved a breakthrough in this area. Summary of the Invention

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

[0007] To achieve the above objectives, the innovative aspects of this invention are as follows: its structure includes:

[0008] 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.

[0009] A high-speed generator, whose rotor is connected to the inner ring of a clutch via a flange;

[0010] A sealed protective housing covers the clutch and high-speed generator and meets the IP67 protection rating.

[0011] The energy recovery circuit rectifies, optimizes, and recharges the electrical energy output from the high-speed generator back into the battery.

[0012] The control module monitors clutch speed, high-speed generator temperature, and battery status in real time.

[0013] Furthermore, the axial length of the outer ring is less than that of the inner ring, and a bidirectional inclined raceway is provided on the outer circumference of the inner ring, with a flange for connecting the high-speed generator at the rear end.

[0014] A mirror-symmetrical bidirectional inclined raceway is provided on the inner circumference of the outer ring, and it is fixed to the sealed protective shell by anti-torsion brackets;

[0015] A ball bearing assembly is installed between two sets of bidirectional inclined raceways;

[0016] 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°.

[0017] Furthermore, the aforementioned ball assembly includes:

[0018] Silicon nitride ceramic balls, with a diameter tolerance of ±0.005mm, are housed between the bidirectional inclined raceways of the inner and outer rings.

[0019] The phosphor bronze cage has 12 ball pockets to hold silicon nitride ceramic balls. The central axis of the ball pockets coincides with the normal axis of the bidirectional ramp raceway.

[0020] Wave springs, with a preload range of 50N to 80N;

[0021] A radial elastic retaining ring is set 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-clear gap fit.

[0022] The bidirectional ramp consists of forward and reverse ramps that are circumferentially alternating and have a 90-degree phase difference.

[0023] Furthermore, the aforementioned wave spring is a ring spring, 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.

[0024] The phosphor bronze cage 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 cage is reserved for thermal expansion compensation gap, with a compensation amount of 0.06mm.

[0025] The limiting boss is located on the inner ring near the high-speed generator end, 2mm away from the bidirectional ramp raceway and its outer diameter is 0.5mm smaller than the root diameter of the bidirectional ramp raceway.

[0026] The axial clearance between the limiting boss and the phosphor bronze cage is 0.1 mm.

[0027] Furthermore, the aforementioned anti-torsion bracket includes three sets of 120° evenly distributed ear seats;

[0028] 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.

[0029] The shear pin and the connecting hole are fitted with an interference fit of 0.01 mm.

[0030] Furthermore, the rotor of the aforementioned high-speed generator is rigidly connected to the inner ring via a flange, and 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.

[0031] A thermally conductive silicone pad is filled between the high-speed generator rotor and the inner ring end face, and the thermally conductive silicone pad extends to the heat dissipation fins of the sealed protective housing.

[0032] The stator winding adopts a coreless disc structure, and the axial hollow of the rotor forms an air duct.

[0033] Furthermore, the aforementioned 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.

[0034] An O-ring is provided at the mating surface of the aluminum alloy base and the engineering plastic top cover;

[0035] The spindle is fitted with a double-lip fluororubber oil seal and a labyrinth seal structure at the point through which it passes the sealed protective housing.

[0036] The labyrinth seal structure includes three annular grooves and two 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.

[0037] Furthermore, a centrifugal fan is installed at the rotor position corresponding to the aforementioned 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;

[0038] Metal filters are installed at the inlet and outlet of the air duct, with a mesh diameter of 0.3 mm.

[0039] Furthermore, the aforementioned energy recovery circuit includes:

[0040] A three-phase rectifier bridge composed of silicon carbide MOSFETs;

[0041] Bidirectional DC-DC converter with MPPT algorithm;

[0042] Hybrid energy storage unit consisting of a 20F / 48V supercapacitor pack and an 18V-54V ternary lithium battery pack;

[0043] The BMS chip integrates a temperature sensor, equalization circuit, and isolation diode.

[0044] Furthermore, the aforementioned control module executes:

[0045] SOC estimation algorithm, supporting 20A continuous charge and discharge;

[0046] The recovery circuit is disconnected when the high-speed generator temperature exceeds 85℃.

[0047] Supercapacitors preferentially absorb peak currents greater than 50A;

[0048] Furthermore, it performs graded control based on the spindle speed:

[0049] Energy recovery is activated when the spindle speed is in the range of -500rpm to -2000rpm.

[0050] When the spindle speed is in the range of 500 rpm to 2000 rpm, the clutch engages to transmit torque;

[0051] When the absolute value of the spindle speed exceeds 2000 rpm, the energy recovery circuit is cut off.

[0052] When the spindle speed is in the range of -500 to 500 rpm, the clutch remains in a free-rotating state.

[0053] The beneficial effects of this invention are:

[0054] 1. Achieving High-Efficiency Capture of High-Dynamic Reverse Energy: This invention completely solves the timeliness and efficiency problems of energy recovery through the mechanical self-locking structure of the bidirectional ball ramp clutch: The mechanical ball ramp design (inclination angle > 5.7° friction angle) automatically switches the power generation mode at the moment of release in 0 milliseconds, 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 measured energy recovery efficiency reaches over 85%; the 50-80N wave spring preload ensures stable meshing of the ball assembly under high-speed conditions, effectively resisting the centrifugal force impact of 10,000rpm;

[0055] 2. Overcoming reliability bottlenecks under harsh working conditions: The sealing-heat dissipation-energy storage synergistic system of this invention overcomes the failure problem of power tools in dusty, humid, and high and low temperature environments: The IP67 sealed protective shell integrates a labyrinth seal + forced air cooling system, achieving a dust rejection rate of >99.5% while enabling continuous operation at 85℃; the supercapacitor-lithium battery hybrid energy storage unit synergistically buffers a peak current of >50A, avoiding damage from large current impacts on the battery and ensuring energy storage safety across the entire temperature range of -40℃ to 85℃; 800MPa shear pin overload protection and a multi-parameter fuse mechanism increase the system's lifespan by 300% under extreme working conditions such as sandstorms and water immersion. Attached Figure Description

[0056] Figure 1 This is a side view of the overall structure of the present invention.

[0057] Figure 2 This is a cross-sectional view of the clutch of the present invention connected inside the sealed protective housing.

[0058] Figure 3 This is an enlarged view of the phosphor bronze cage of the present invention.

[0059] Figure 4 This is a structural diagram of the phosphor bronze cage and the inner circumference of the outer ring of the present invention. Detailed Implementation

[0060] 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.

[0061] 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.

[0062] Example 1: Implementation of the mechanical structure of clutch 1

[0063] The core mechanical structure of the clutch of this invention and its connection relationship with the housing are as follows: Figure 2As 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.

[0064] 1.1 Inner Ring 11 Processing

[0065] 20CrMnTi alloy steel billet is selected and formed by CNC lathe.

[0066] 4. External circumferential machining of bidirectional inclined raceway:

[0067] Forward slope 41 and reverse slope 42 are alternately distributed circumferentially, with a phase difference of 90 degrees.

[0068] Inclination angle 6.0° ± 0.1° (greater than the friction angle of steel, 5.7°)

[0069] Surface carburizing and quenching treatment, hardness up to HRC62

[0070] Near the generator end, a limiting boss 111 is machined.

[0071] The height of the limiting boss 111 is 0.5mm, and its axial distance from the inclined raceway is 2.0mm.

[0072] The outer diameter of the limiting boss 111 is 0.5mm smaller than the root diameter of the ramp raceway.

[0073] 1.2 Outer Ring 12 Assembly

[0074] The inner circumference is machined with a mirror-symmetric inclined raceway, with a distance of 3.0 mm from the annular limiting groove 121.

[0075] Implementation of anti-torsion bracing:

[0076] Three sets of earpieces 51 are welded to the outer ring 12 at 120° evenly distributed.

[0077] 30CrMnSiA quenched steel shear pin 52 interference fit (tolerance 0.01mm)

[0078] Ultimate shear strength 800 MPa

[0079] 1.3 Ball bearing assembly 6

[0080] Step 1: Insert the wave spring 63 into the annular limiting groove 121 of the outer ring 12;

[0081] Step 2: Place the phosphor bronze retainer 62 (12-ball holder 621, aperture tolerance ±0.003mm), as follows. Figure 3As shown, the phosphor bronze cage 62 is a ring-shaped component with 12 ball pockets 621 precisely machined on it to hold silicon nitride ceramic balls 61. The central axis of each ball pocket 621 coincides with the normal axis of the bidirectional inclined raceway 4 to ensure that the balls 61 are subjected to uniform force.

[0082] Step 3: Place 12 silicon nitride ceramic balls 61 (diameter tolerance ±0.005mm) one by one into the 12 ball pockets 621 of the cage (diameter tolerance ±0.005mm).

[0083] Step 4: Pre-compression test (no displacement of the ball bearings under 50-80N pressure)

[0084] Step 5: Press the 65Mn spring steel radial elastic retaining ring 64 into the cage annular retaining groove 622 (elastic retaining ring 64 wire diameter 0.8mm, initial preload 15N).

[0085] The axial clearance between the limiting boss 111 and the phosphor bronze cage 62 is 0.1mm, such as... Figure 4 As shown, an annular groove 622 is machined on the outer circumferential surface of the phosphor bronze retainer 62. After the radial elastic spring 64 is pressed into the annular groove 622, the outer diameter of the elastic spring 64 in its natural state is slightly larger than the outer diameter of the phosphor bronze retainer 62, so that it forms a slight interference or slight clearance fit with the inner wall of the outer ring 12, thereby achieving radial limiting.

[0086] The preload of wave spring 63 is optimized to 80N (within the range of 50N-80N, verified by ANSYS Hertz contact stress simulation, the maximum contact stress of the ball under a preload of 50-80N is ≤750MPa, and the preload of wave spring 63 is optimized to 80N (within the range of 50N-80N)).

[0087] Comparative Test:

[0088]

[0089] Example 2: Implementation of Thermal Management and Sealing System

[0090] 2.1 High-speed generator 3-direct-drive structure

[0091] The rotor 31 of the high-speed generator 3 is connected to the inner ring 11 via flange 32.

[0092] Six grade 12.9 high-strength bolts (torque 8 Nm)

[0093] Two interference fit precision locating pins 7 (Φ2H7)

[0094] Heat conduction path construction:

[0095] 0.5mm thermally conductive silicone sheet 71 fills rotor 31-inner ring 11 interface

[0096] The thermally conductive silicone pad 71 extends to the aluminum alloy base 21 and the heat dissipation fins 72 (AlSi7Mg aluminum alloy).

[0097] Rotor 31 is axially hollow to form an air duct 8

[0098] 2.2 Forced Air Cooling System

[0099] Centrifugal fan 101 implementation:

[0100] Number of blades: 12 titanium alloy fan blades

[0101] Installation location: Section 31 of rotor corresponding to sealed protective housing 2.

[0102] Blade-rotor clearance 31: 1.8 ± 0.2 mm

[0103] 8-way protection:

[0104] The inlet and outlet are equipped with 304 stainless steel filter screens (102 mesh size, 0.3mm).

[0105] Dustproof efficiency 99.5% (ISO12103-A3 test)

[0106] The airflow path of the forced air cooling system is as follows: Driven by the centrifugal fan 101, the cooling airflow is drawn in by the inlet metal filter 102, flows through the air duct 8 formed in the hollow rotor 31, carries heat and blows it toward the heat dissipation fins 72 of the aluminum alloy base 21, and finally is discharged from the gaps between the heat dissipation fins 72, forming an effective directional cooling cycle.

[0107] 2.3 Implementation of Sealing and Protection

[0108] Labyrinth-style sealing structure 9:

[0109] The spindle 100 is equipped with three annular grooves 91 (1.5mm deep and 2mm wide).

[0110] Equip with two PTFE oil slinger rings 92 (3mm thick, 0.02mm interference fit).

[0111] Sealed protective housing 2 seal:

[0112] A fluororubber O-ring 81 is provided between the aluminum alloy base 21 and the engineering plastic cover 22.

[0113] The spindle 100 through section uses a double-lip fluororubber 82 oil seal (temperature resistance -40~150℃).

[0114] At the opening through which the main shaft 100 penetrates the sealing and protective housing 2, a labyrinth seal structure 9 and a double-lip fluororubber 82 oil seal are arranged sequentially from the outside to the inside. The labyrinth seal structure 9 serves as the first level of protection, and the double-lip fluororubber 82 oil seal serves as the second level of protection, together forming an IP67-rated shaft end sealing system.

[0115] Example 3: Implementation of Energy Recovery Control

[0116] 3.1 Circuit Topology Implementation

[0117] Energy recovery pathway:

[0118] High-speed generator 3 → Silicon carbide MOSFET rectifier bridge →

[0119] MPPT bidirectional DC-DC converter → Hybrid energy storage unit

[0120] Hybrid energy storage unit composition:

[0121] Supercapacitor bank: 20F / 48V (absorbs >50A peak current)

[0122] Ternary lithium battery pack: 18V-54V adaptive (supports 20A continuous discharge)

[0123] Isolation diodes prevent reverse current flow

[0124] 3.2 Control Strategy Execution

[0125] The speed graded control strategy enables the system to achieve 85% energy recovery efficiency within the 2000rpm threshold, while eliminating the timing conflict between 8000rpm overspeed protection and reverse power generation in the traditional scheme.

[0126] The control module performs graded speed management:

[0127] The control module performs graded speed management:

[0128] 1. Reverse power generation mode: -2000rpm≤n≤-500rpm.

[0129] 2. Forward torque transmission: 500rpm≤n≤2000rpm.

[0130] 3. Overspeed protection: |n|>2000rpm, cut-off test: 50 consecutive overspeed protection triggers, system response time ≤2ms.

[0131] 4. Free rotation: -500rpm <n<500rpm。

[0132] Security protection mechanism:

[0133]

[0134] Experimental data:

[0135] Test results for a 12V lithium-ion drill:

[0136]

[0137] Note: Continuous operation in dusty environments: Traditional tools jam after an average of 2 hours due to dust intrusion (n=5); This invention can work continuously for 8 hours without failure (n=5).

[0138] Power tool test form:

[0139]

[0140] System working principle

[0141] Phase 1: Drilling Operations (Energy Consumption)

[0142] The user pulls the trigger, and the spindle rotates 100 degrees clockwise.

[0143] The ball bearings are wedged into the positive ramp 41, and the inner and outer rings 12 are locked.

[0144] Torque is transmitted via inner ring 11 → spindle 100 → drill bit output.

[0145] Phase 2: Disengagement Braking (Energy Recovery)

[0146] 1. At the moment the screw comes out, the connected component springs back elastically.

[0147] 2. The spindle 100 is subjected to a reverse impact torque (>50Nm).

[0148] 3. The ball bearings wedge into the reverse ramp 42, causing the inner ring 11 to rotate in the opposite direction.

[0149] 4. Inner ring 11 drives high-speed generator 3, rotor 31 generates electricity.

[0150] Phase 3: Energy Storage

[0151] The generator outputs three-phase alternating current.

[0152] The rectifier bridge converts to direct current.

[0153] MPPT algorithm tracks the maximum power point

[0154] The supercapacitor absorbs peak current and then transfers it to the lithium battery.

[0155] Phase 4: System Protection

[0156] Temperature sensors monitor generator temperature rise in real time

[0157] Speed ​​sensor detects clutch 1 overspeed

[0158] Abnormal state trigger circuit fuse mechanism

[0159] Implement risk warnings

[0160] 1. Thermal expansion control: Silicon nitride ball bearings (α=3.2×10⁻) 6 / ℃) and phosphor bronze cage 62 (α=18×10⁻ 6 A 0.06mm thermal compensation gap needs to be reserved (at / ℃);

[0161] 2. Machining accuracy requirements: The 100mm spindle journal must meet IT4 grade accuracy (GB / T1800.2), and the double-lip oil seal interference is 0.02mm.

[0162] Industrial applicability

[0163] This system has been applied to:

[0164] Dongcheng DCJZ1200 electric drill (mass production model).

[0165] Bosch GBH18V impact drill (OEM customization).

[0166] Field rescue tool kit (military grade).

[0167] Finally, the following points should be noted: First, in the description of this application, it should be noted that, unless otherwise specified and limited, the terms "installation", "connection", and "linkage" should be interpreted broadly, and can be mechanical or electrical connections, or internal connections between two components, or direct connections. "Up", "down", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may change.

[0168] Secondly: The accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments disclosed in this invention. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

[0169] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

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. 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°. The ball assembly includes: Silicon nitride ceramic balls, with a diameter tolerance of ±0.005mm, are housed between the bidirectional inclined raceways 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. 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.

2. The regenerative braking energy recovery system for power tools according to claim 1, 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.

3. 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 of the sealed protective housing. The stator winding adopts a coreless disc structure, and the axial hollow of the rotor forms an air duct.

4. A regenerative braking energy recovery system for power tools according to claim 3, 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.

5. A regenerative braking energy recovery system for power tools according to claim 3, 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.

6. 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.

7. A regenerative braking energy recovery system for power tools according to claim 6, 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 spindle speed is in the range of 500 rpm to 2000 rpm, the clutch engages to transmit torque; 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 -500 to 500 rpm, the clutch remains in a free-rotating state.

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