Active damping flywheel for single cylinder two-stroke engine
Patent Information
- Application Number
- CN202522265250.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-27
- Publication Date
- 2026-08-28
- Estimated Expiration
- 2035-10-27
AI Technical Summary
[0006]针对单缸二冲程发动机一阶往复惯性力无法被有效平衡、导致整机振动剧烈的问题，本实用新型提供一种具有不平衡结构的飞轮方案，在显著降低垂直方向振动的同时，避免侧向(横向)振动恶化，并以最小质量的增量来实现最优的手柄三向合成振动性能
[0026] 1) By adding an unbalanced counterweight to the flywheel to actively counteract and directly balance the first-order reciprocating inertial force, vibration can be suppressed from the source, rather than passively isolating vibration through damping components such as springs; with zero additional parts, only the mass distribution of the flywheel is changed, without adding any modifications to engine components such as balance shafts, bearings, and housings, meeting the requirements of lightweighting and avoiding vibration without increasing the complexity of parts;
Smart Images
Figure CN224693871U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of vibration reduction technology for small internal combustion engines, and in particular to an active vibration reduction flywheel for a single-cylinder two-stroke engine. Background Technology
[0002] Single-cylinder two-stroke engines are widely used in handheld garden machinery such as chainsaws, brush cutters, and blowers due to their simple structure, high power-to-weight ratio, and low cost. However, the crankcase ventilation and reciprocating piston-connecting rod assembly of these engines mean that the first-order reciprocating inertial force cannot be counteracted by the engine's own structure. Excessive vibration not only reduces operator comfort but also leads to fatigue failure of machine components, loose connections, and excessive noise.
[0003] Existing vibration reduction methods mainly include: adding rubber / spring vibration dampers or handle vibration damping sleeves, but these are passive vibration isolation methods with limited effectiveness in suppressing high-frequency vibrations; setting up balance shafts, but these require additional gear systems, bearings, and housing modifications, resulting in complex structures and increased weight, which contradicts the need for lightweight handheld devices; and adopting multi-cylinder or opposed piston layouts, but these significantly increase costs and weight, making them unsuitable for low-cost, small-displacement markets.
[0004] Therefore, without adding independent parts or changing the basic structure of the engine, there is an urgent need for an active vibration reduction solution that is compact, low-cost, and easy to industrialize, in order to solve the above problems.
[0005] The above content is only used to help understand the technical solution of this application and does not represent an admission that the above content is the closest prior art to this application. Summary of the Invention
[0006] To address the problem that the first-order reciprocating inertial force of a single-cylinder two-stroke engine cannot be effectively balanced, resulting in severe vibration of the entire engine, this invention provides a flywheel solution with an unbalanced structure. This solution significantly reduces vertical vibration while avoiding the deterioration of lateral (transverse) vibration, and achieves optimal three-dimensional composite vibration performance of the handle with minimal mass increment.
[0007] This application provides an active vibration damping flywheel for a single-cylinder two-stroke engine to solve one of the aforementioned technical problems.
[0008] The technical solution adopted by this application to solve its technical problem is:
[0009] An active vibration damping flywheel for a single-cylinder two-stroke engine includes: a crankshaft driven by a piston-connecting rod assembly, characterized in that the flywheel is mounted on the crankshaft, and the flywheel body is provided with at least one unbalanced counterweight in the circumferential direction, the flywheel and the unbalanced counterweight thereon being used to partially counteract the vertical inertial force on the crankshaft and suppress lateral vibration.
[0010] In some embodiments, the mass moment U = m × r of the unbalanced counterweight is set as follows:
[0011] U = k × (m p +m / 3)×R
[0012] in:
[0013] m p —Piston mass;
[0014] m — Mass of the connecting rod;
[0015] R—crank radius;
[0016] k — partial balance coefficient, and 0.08≤k≤0.15.
[0017] When k = 0.1, the centrifugal force amplitude of the flywheel is 10% of the first-order reciprocating inertial force of the engine. This ensures both a significant reduction in vertical vibration and suppression of the horizontal component of the centrifugal force.
[0018] To prevent the amplification of lateral vibration of the entire machine.
[0019] In some embodiments, for handheld single-cylinder two-stroke gasoline engines with a displacement of 20ml-80ml and a rated speed of 8000r / min-12000r / min, the recommended range for the moment of mass is 0.8×10⁻⁶. -4 kg·m≤U≤2.2×10 -4 kg·m (i.e., 80 g·mm - 220 g·mm), typical value 1.5 × 10 -4 kg·m (i.e., 150 g·mm) is sufficient to cause the handle to undergo triaxial composite vibration. hv The decrease is ≥40%, and the increase in lateral vibration is ≤5%.
[0020] In some embodiments, the piston-connecting rod assembly includes a piston and a connecting rod, the connecting rod being hinged to the crankshaft via a crank pin, and the position of the centroid angle θ of the unbalanced counterweight being 45°±5° ahead of the crank pin centerline toward the piston top dead center.
[0021] In some embodiments, a plurality of fan blades are provided at equal intervals on the outer edge of the flywheel, and the unbalanced counterweight is integrated with the fan blades on the flywheel.
[0022] In some embodiments, magnets are provided on the fan blades on the outer edge of the flywheel.
[0023] In some embodiments, the unbalanced counterweight is integrally forged with the flywheel, the center of mass of the unbalanced counterweight is located between the rotation center of the flywheel and the maximum outer edge, and the unbalanced counterweight uses high-density alloy inserts to achieve small volume and large mass moment.
[0024] In some embodiments, the flywheel and crankshaft are positioned by a semi-circular key and rigidly connected by locking with a nut to avoid additional torsional vibration.
[0025] The beneficial effects of this application are as follows:
[0026] 1) By adding an unbalanced counterweight to the flywheel to actively counteract and directly balance the first-order reciprocating inertial force, vibration can be suppressed from the source, rather than passively isolating vibration through damping components such as springs; with zero additional parts, only the mass distribution of the flywheel is changed, without adding any modifications to engine components such as balance shafts, bearings, and housings, meeting the requirements of lightweighting and avoiding vibration without increasing the complexity of parts;
[0027] 2) The structure is compact, and the axial and radial dimensions of the flywheel in this application are completely interchangeable with the original flywheel, and the assembly process remains unchanged; the functional integration is high, and under the action of the fan blades and magnets, the flywheel can simultaneously serve as the cooling fan blade and the magneto rotor; under the action of the flywheel in this application, the triaxial vibration acceleration of the whole machine is reduced by 25-40%, the risk of operator arm vibration syndrome (HAVS) is significantly reduced, and the vibration reduction effect is significant;
[0028] 3) Wide range of applications, covering all single-cylinder two-stroke gasoline engines with displacement of 20ml-80mL, air-cooled, and installed vertically or horizontally. Attached Figure Description
[0029] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0030] Figure 1 This is a schematic diagram of the assembly relationship between the active vibration damping flywheel, crankshaft, and piston-connecting rod in this application.
[0031] Figure 2 This is a diagram showing the phase relationship between the unbalanced counterweight mass moment vector and the reciprocating inertial force vector in this application.
[0032] Figure 3 This is a schematic diagram of the unbalanced counterweight arrangement in this application.
[0033] Figure 4 This is a schematic diagram of the AA section of this application.
[0034] Figure 5 This is a schematic diagram of the rigid connection between the flywheel and the crankshaft in this application.
[0035] The following are the symbols and their meanings: 1. Flywheel, 2. Unbalanced counterweight, 3. Crankshaft, 4. Piston, 5. Connecting rod, 6. Half-circle key, 7. Nut, 11. Fan blade, 12. Magnet, 31. Crank pin. Detailed Implementation
[0036] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application. In addition, the technical solutions of various embodiments can be combined with each other, but this must be based on the ability of those of ordinary skill in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection of this application.
[0037] In the embodiments of this application, please refer to Figure 1-5 As shown, this active vibration damping flywheel for a single-cylinder two-stroke engine mainly includes:
[0038] An active vibration damping flywheel for a single-cylinder two-stroke engine includes a crankshaft 3 driven by a piston-connecting rod assembly. The flywheel 1 is mounted on the crankshaft 3, and at least one unbalanced counterweight 2 is provided circumferentially on the flywheel 1. The flywheel 1 and the unbalanced counterweight 2 are used to partially offset the vertical inertial force on the crankshaft 3 and suppress lateral vibration. The centrifugal force amplitude generated by the flywheel 1 when rotating with the crankshaft 3 is 8%-15% of the engine's first-order reciprocating inertial force. This flywheel 1 is mainly used for active vibration damping of a single-cylinder two-stroke engine.
[0039] The following will continue to describe some preferred / improved embodiments based on the above embodiments. Any one of the following embodiments can be selected, or multiple embodiments can be combined.
[0040] Specifically, the mass moment U = m × r of the unbalanced counterweight 2 is set as follows:
[0041] U = k × (m p +m / 3)×R
[0042] in:
[0043] m p —Piston mass;
[0044] m — Mass of the connecting rod;
[0045] R—crank radius;
[0046] k — partial balance coefficient, and 0.08≤k≤0.15.
[0047] When k = 0.1, the centrifugal force amplitude of flywheel 1 is 10% of the first-order reciprocating inertial force of the engine. This ensures that the vertical vibration is significantly attenuated and the horizontal component of the centrifugal force is suppressed, preventing the amplification of the lateral vibration of the whole machine.
[0048] Furthermore, for handheld single-cylinder two-stroke gasoline engines with a displacement of 20ml-80ml and a rated speed of 8000r / min-12000r / min, the recommended range for the moment of mass is: 0.8×10 -4 kg·m≤U≤2.2×10 -4 kg·m (i.e., 80 g·mm - 220 g·mm), typical value 1.5 × 10 -4 kg·m (150 g·mm) can make the handle undergo triaxial composite vibration a hv The decrease is ≥40%, and the increase in lateral vibration is ≤5%.
[0049] like Figure 1 As shown, the piston-connecting rod assembly includes a piston 4 and a connecting rod 5. The connecting rod 5 is hinged to the crankshaft 3 via a crank pin 31. The position of the centroid angle θ of the unbalanced counterweight 2 is 45°±5° ahead of the center line of the crank pin 31 towards the top dead center of the piston 4.
[0050] Furthermore, a plurality of fan blades 11 are evenly spaced on the outer edge of the flywheel 1, and the unbalanced counterweight 2 is integrated with the fan blades 11 on the flywheel 1.
[0051] Furthermore, a magnet 12 is provided on the fan blades 11 on the outer edge of the flywheel 1.
[0052] Specifically, the unbalanced counterweight 2 and the flywheel 1 are forged as a single piece. The center of mass of the unbalanced counterweight 2 is located between the rotation center of the flywheel 1 and the maximum outer edge. The unbalanced counterweight 2 uses high-density alloy inserts to achieve a small volume and a large mass moment.
[0053] Furthermore, the flywheel 1 and crankshaft 3 are positioned by a semi-circular key 6 and are rigidly connected by a nut 7 to prevent additional torsional vibration.
[0054] Furthermore, based on the vibration reduction principle proposed in this invention, the target mass moment (imbalance) U of the unbalanced counterweight 2 is first determined. The relevant known engine parameters and calculation process are as follows:
[0055] 1. Known parameters
[0056] Piston mass m p =65g
[0057] Connecting rod mass m = 52g
[0058] Crank radius R = 17.5 mm
[0059] Rated speed n = 8500 r / min
[0060] Partial balance coefficient k = 0.1
[0061] Objective: To make the flywheel imbalance m·r satisfy:
[0062] U=m·r=k·(m_p+m / 3)·R=0.1×(65+52 / 3)×17.5
[0063] ≈1.44×10 -4 kg·m
[0064] Actual test handle a hv From 12.5m / s 2 Reduced to 8.7 m / s 2 The decrease was 30%, while the lateral a_x increased by only 0.3 m / s. 2 There was no obvious feeling of shaking off the arm.
[0065] 2. Flywheel structure
[0066] Wheel body material: cast aluminum alloy ADC12, density 2.75 g / cm³ 3
[0067] Outer diameter D = 90 mm, thickness H = 35 mm
[0068] A magnet 12 is installed in the rim sector, and a counterweight is installed on the magnet 12 to form an integrated unbalanced counterweight.
[0069] 3. Phase positioning
[0070] like Figure 2 and Figure 5 As shown, the center line of the crankshaft 3 keyway is in the same direction as the crank pin 31; the center line of the flywheel 1 hub keyway is at an angle of 45°±5° with the center of mass of the counterweight; a grade 10 M8×1 nut 7 is used to tighten with a torque of 20 N·m to ensure no relative slippage at high speed.
[0071] 4. Test Results
[0072] The entire machine underwent a three-dimensional acceleration test according to the requirements of GB / T5392-2017 "Forestry Machinery - Portable Handheld Chainsaw".
[0073] Original machine (with traditional static balance flywheel) handle a hv =12.5m / s 2
[0074] After replacing the flywheel 1 of this utility model, a hv =8.7m / s 2The exposure rate decreased by 30%; the operator's measured 4-hour arm exposure value was lower than the EU EAV 2.5 m / s. 2 Limit.
[0075] Summary of Experimental Verifications
[0076] A 200-hour load endurance test was conducted on 10 prototype units from the above embodiments. Results:
[0077] The vibration attenuation rate is 25-40%, and no unit has experienced problems such as counterweight falling off or flywheel cracking.
[0078] Power, fuel consumption, and emissions differ from the original engine by less than 1%, meeting EPA Phase III and EU Stage V regulations; operator arm vibration exposure values are all below EU EAV 2.5m / s. 2 The standard.
[0079] In summary, this utility model achieves a significant reduction in overall machine vibration by precisely setting an unbalanced counterweight 2 on the flywheel 1, which allows the centrifugal force of rotation to actively counteract the first-order reciprocating inertial force of the piston 4-connecting rod 5 without adding any additional shaft system or changing the engine housing. It is also simple to manufacture, low in cost, and highly reliable, and can be quickly industrialized for application in various handheld single-cylinder two-stroke gasoline-powered tools.
[0080] The various embodiments of this application have now been described in detail. To avoid obscuring the concept of this application, some details known in the art have not been described. Those skilled in the art can fully understand how to implement the technical solutions disclosed herein based on the above description.
[0081] Finally, it should be noted that the above description is only a preferred embodiment of this application. The foregoing embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.
Claims
1. An active vibration damping flywheel for a single-cylinder two-stroke engine, comprising a crankshaft (3) driven by a piston (4) and connecting rod (5) assembly, characterized in that, The flywheel (1) is mounted on the crankshaft (3). The flywheel (1) has at least one unbalanced counterweight (2) on its circumference. The flywheel (1) and the unbalanced counterweight (2) on it are used to partially offset the vertical inertial force on the crankshaft (3) and suppress lateral vibration.
2. The active vibration damping flywheel for a single-cylinder two-stroke engine according to claim 1, characterized in that, The mass moment U = m × r of the unbalanced counterweight (2) is set as: U=k×(m p +m / 3)×R in: m p —Piston mass; m — Mass of the connecting rod; R—crank radius; k — partial balance coefficient, and 0.08≤k≤0.
15.
3. The active vibration damping flywheel for a single-cylinder two-stroke engine according to claim 2, characterized in that, 0.8×10 -4 kg·m≤U≤2.2×10 -4 kg·m (i.e., 80g·mm-220g·mm).
4. An active vibration damping flywheel for a single-cylinder two-stroke engine according to any one of claims 1-3, characterized in that, The piston (4) and connecting rod (5) assembly includes a piston (4) and a connecting rod (5). The connecting rod (5) is hinged to the crankshaft (3) by a crank pin (31). The centroid angle position of the unbalanced counterweight (2) is 45°±5° ahead of the center line of the crank pin (31) towards the top dead center of the piston (4).
5. An active vibration damping flywheel for a single-cylinder two-stroke engine according to claim 1, characterized in that, The flywheel (1) has a plurality of fan blades (11) evenly spaced on its outer edge, and the unbalanced counterweight (2) is integrated with the fan blades (11) on the flywheel (1).
6. An active vibration damping flywheel for a single-cylinder two-stroke engine according to claim 5, characterized in that, Magnets (12) are provided on the fan blades (11) on the outer edge of the flywheel (1).
7. An active vibration damping flywheel for a single-cylinder two-stroke engine according to claim 1, characterized in that, The unbalanced counterweight (2) and the flywheel (1) are forged as a single piece, and the center of mass of the unbalanced counterweight (2) is located between the rotation center of the flywheel (1) and the maximum outer edge.