The noise generated by the gearbox of a manual forklift (DiNiu) mainly comes from multiple aspects such as design, manufacturing, installation, and maintenance. The following is a detailed summary of these reasons:

1、 Design reasons

Gear accuracy level: When designing a reducer, if the gear accuracy level is not selected properly, it may increase noise. High precision gears produce much less noise than low precision gears.

Gear width: When the transmission space allows, increasing the gear width can reduce the unit load under constant torque, reduce tooth deflection, and thus reduce noise excitation.

Pitch and pressure angle: A small pitch can ensure that more teeth are in contact at the same time, reducing the deflection of individual gears and lowering transmission noise. The smaller pressure angle results in lower operating noise and higher accuracy due to the larger gear contact angle and lateral overlap ratio.

Selection of displacement coefficient: Correctly and reasonably selecting the displacement coefficient can not only avoid gear root cutting, ensure the satisfaction of concentric conditions, improve the transmission performance of gears and enhance their load-bearing capacity and service life, but also effectively control backlash, temperature rise, and noise.

Tooth profile trimming and tooth tip chamfering: Cutting the tooth profile of the tooth tip into a slightly convex shape compared to the correct involute curve can avoid interference with the gears that mesh with it, reduce noise, and extend gear life. However, it should be noted not to make excessive adjustments to avoid increasing tooth profile errors.

Power source operating speed: As the input speed of the gearbox increases, the noise will also increase.

Box structure form: Using a cylindrical box is beneficial for shock absorption. Under the same conditions, the average noise level of a cylindrical box is 5dB lower than other types of boxes. Conducting resonance tests on the gearbox body to identify the resonance position and adding appropriate ribs (plates) can improve the stiffness of the box, reduce vibration, and achieve noise reduction.

2、 Manufacturing reasons

Gear error: Gear profile error, pitch deviation, tooth orientation error, and radial runout error in the gear manufacturing process are the main errors that cause transmission noise. Gears with small tooth profile errors and small tooth surface roughness have a noise level that is 10dB lower than ordinary gears. Gears with small tooth pitch errors have a noise level that is 6-12dB lower than ordinary gears. Tooth orientation errors will cause transmission power not to be transmitted across the entire tooth width, and the contact area will turn to this or that end face of the teeth, causing local stress to increase and resulting in tooth deflection, leading to an increase in noise level.

Assembly concentricity and dynamic balance: Assembly with different concentricity will cause imbalance in the operation of the shaft system, and due to the loose and tight half of the gear meshing, it will jointly lead to increased noise.

Tooth surface hardness: In order to obtain a hard tooth surface, carburizing and quenching are used to deform the gear, resulting in increased gear transmission noise and shortened service life. To reduce noise, it is necessary to perform precision machining on the tooth surface.

3、 Installation reason

Vibration reduction and blocking measures: When installing the gearbox, efforts should be made to avoid resonance between the machine body, foundation support, and connecting components, which can generate noise. Some reducers that require low transmission noise and vibration should use high toughness and high damping base materials to reduce the occurrence of noise and vibration.

Geometric accuracy adjustment of components: During installation, the geometric accuracy did not meet the standard requirements, resulting in resonance of the gearbox components and the generation of noise.

Loose components: During installation, due to the looseness of individual components (such as bearing pre tensioning mechanism, shaft positioning mechanism, etc.), the system positioning is inaccurate, abnormal position engagement occurs, shaft movement occurs, resulting in vibration and noise.

Damage to transmission components: Improper operation during installation can damage transmission components, resulting in inaccurate or unstable system movement; High speed moving parts experience oil film vibration due to damage; Artificially causing dynamic imbalance of moving parts; Both generate vibration and noise.

4、 Reason for use and maintenance

Internal cleaning: The cleanliness of the internal components of the gearbox is a basic condition for its normal operation. Any impurities or dirt entering will affect and damage the transmission system, leading to the generation of noise.

Working temperature: Ensure the normal working temperature of the reducer, avoid deformation of components due to excessive temperature rise, ensure normal gear meshing, and thus prevent the increase of noise.

Timely lubrication and correct use of oil: Unreasonable lubrication and incorrect use of lubricating grease will cause immeasurable damage to the gearbox. At high speeds, the friction between gear teeth generates a large amount of heat energy. Improper lubrication can cause damage to gear teeth, affect accuracy, and increase noise. During design, it is required that the gear pair has appropriate clearance (clearance between non working surfaces of meshing teeth to compensate for thermal deformation and storage of lubricating grease). The correct use and selection of lubricating grease can ensure the safe and effective operation of the system, delay the deterioration trend, and stabilize the noise level.

Proper use of the gearbox: Proper use of the gearbox can minimize damage to components and ensure a stable noise level. The noise of the gearbox will increase with the increase of load, so it should be used within the normal load range.

The main equipment produced by Hebei Makita: stage electric hoist, electric chian hoist, wire rope electric hoist，Hand chain hoist, lever hoist, pneumatic hoist and other lifting equipment