1. Introduction
Spur bevel gears are crucial mechanical components, playing a vital role in torque transmission across various machinery. Their unique characteristics, such as the ability to operate with shafts at angles from 0° – 90°, offer advantages over other types of gears. However, ensuring the proper meshing of these gears is a complex task. When gears are paired and meshed, specific parameters need to be measured, and any issues in meshing can lead to problems like uneven wear, reduced transmission efficiency, and shortened gear lifespan. This article focuses on the design, operation, and significance of a specialized fixture for detecting spur bevel gear meshing.
2. Product Background
2.1 Importance of Spur Bevel Gears in Machinery
Spur bevel gears are widely used in numerous mechanical devices, especially in power – transmission systems. Their function is to transfer rotational motion and torque between intersecting shafts. For example, in the rubber – plastic machinery produced by the author’s company, such as single – hung double – cone twin – screw extruders, the synchronous bevel gears are key components. These gears need to operate smoothly and efficiently to ensure the proper functioning of the entire machine.
| Machinery Type | Role of Spur Bevel Gears |
|---|---|
| Single – hung double – cone twin – screw extruder | Transmit power between different shafts, enabling the extrusion process |
| Automotive differential | Adjust the speed of wheels during turning, ensuring smooth driving |
| Industrial reducers | Reduce the speed and increase the torque for various industrial applications |
2.2 Problems in Gear Meshing during Assembly
During the assembly of spur bevel gears in the single – hung double – cone twin – screw extruder, practical issues frequently occur. The side clearance between the large and small ends of the meshed bevel gears often varies significantly. This disparity results in insufficient contact along the tooth width during gear meshing. As a consequence, the contact area is smaller than the design requirement, leading to uneven wear on the gear teeth. The areas with contact experience accelerated wear, while those without contact remain relatively unaffected. This not only affects the transmission performance but also shortens the service life of the gears.
3. Design of the Meshing Detection Fixture
3.1 Overall Structure
The designed spur bevel gear meshing detection fixture is illustrated in Figures 1 and 2. It consists of multiple components, each with a specific function. The base provides a stable foundation for the entire fixture. The (guides) and (sliders) enable the movement of the (support), facilitating the meshing of the gears. The (mounting plate) is used to fix the gears and related components.
| Component | Function |
|---|---|
| Base | Provide stability and support for the entire fixture |
| Guides | Guide the movement of the support along a specific path |
| Sliders | Move along the guides, allowing the adjustment of the gear position |
| Mounting plate | Fix the gears and other components in place |
| Pin | Ensure the correct relative position of components |
| Support | Hold the gears and enable height adjustment |
| Fixed block | Assist in adjusting the bevel angle |
| Spacer sleeve | Determine the axial position of the gears |
| Support bolt | Adjust the bevel angle by moving the fixed block |
| Round nut | Fix the installation shaft and prevent component loosening |
| Spacer ring | Maintain a certain distance between components |
| Cylindrical self – aligning roller bearing | Support the rotation of the installation shaft and adapt to misalignment |
| Cylindrical thrust roller bearing | Bear the axial force during gear meshing |
| Installation shaft | Mount the gears and enable their rotation |
| Key | Prevent the relative rotation between the gear and the installation shaft |
| Bevel gear | The component to be tested for meshing |
3.2 Component Design Details
- Installation Shaft: The outer diameter of the installation shaft is designed to have a clearance fit with the inner hole of the bevel gear. This modification from the original interference or transition fit in the design drawing is to facilitate the easy installation and removal of the gears during testing. Before installation, the inner hole of the bevel gear is lubricated to further ease the installation process.
- Adjustment Mechanism for Bevel Angle: The bevel angle can be adjusted by turning the support bolt. This bolt drives the fixed block to rotate around the pin, allowing for a bevel angle adjustment range of 0 – 20°. When the bevel angle is set to 0°, the fixture can also be used to test the meshing of spur cylindrical gears.
4. Operation Steps of the Fixture
4.1 Preparation before Installation
Before installing the bevel gears, the fixed block is adjusted to the horizontal position. This ensures a proper starting position for the gear installation process.
4.2 Gear Installation
- First, apply lubricant to the inner – hole mating surface of the bevel gear. This reduces friction and makes it easier to slide the gear onto the installation shaft.
- Then, install the bevel gear onto the installation shaft. As mentioned earlier, the modified clearance fit between the installation – shaft outer diameter and the gear inner – hole simplifies this step.
- Next, insert the key into the keyway to prevent the single bevel gear from freely rotating around the installation shaft. This ensures that the gear remains in a fixed position relative to the shaft during testing.
4.3 Assembly Check and Adjustment
- Check the round nut at the tail of the installation shaft to ensure that the inner and outer rings of the self – aligning roller bearing at the bottom of the fixture are not loose. A loose bearing can affect the accuracy of the meshing test.
- Adjust the bevel angle according to the design requirements of the bevel gear. Rotate the support bolt to achieve the desired bevel angle.
- Move the support along the guide to make the two bevel gears mesh smoothly. After meshing, lock the slider to prevent any lateral displacement of the support, ensuring a stable meshing state for testing.
4.4 Meshing Test
Through the hexagonal – wrench inner hole at the end face of the installation shaft, manually rotate the two meshed gears. This rotation allows for the inspection of the meshing condition, such as the presence of abnormal noises, uneven meshing, or excessive resistance.
5. Main Parameters and Application Range of the Fixture
5.1 Main Parameters
| Parameter | Value |
|---|---|
| Overall dimensions | 2000 mm × 1020 mm × 1300 mm |
| Adjustable bevel – angle range | 0 – 20° |
| Applicable gear diameter range | Ф800 – Ф1200 |
| Maximum gear weight it can bear | 5 t/ piece |
5.2 Application Range
The fixture is versatile and can be used for the meshing detection of both spur bevel gears and spur cylindrical gears. This wide application range makes it a valuable tool in the gear – manufacturing and mechanical – assembly industries.
6. Meshing Detection Analysis of Spur Bevel Gears
6.1 Influential Factors on Meshing
The meshing of spur bevel gears is mainly affected by two parameters: the cone distance and the bevel angle, apart from the tooth profile. The cone distance determines the position of the meshing gears on the rotating shaft, similar to the center – distance parameter in cylindrical gears, but with an angle between the axes of bevel gears. The bevel angle reflects the angle between the gear center and the dividing – circle straight line, directly influencing the contact – spot area of the gear teeth and thus the power – transmission performance.
6.2 Meshing States and Their Analysis
- Ideal Meshing State: In the ideal meshing state (Figure 3), the dividing – circle straight lines of the two bevel gears coincide, and the tooth – side clearance is completely eliminated. However, in practical applications, due to machining errors and the risk of gear jamming in zero – clearance meshing, this state is rarely adopted.
Parallel Meshing State: In the parallel meshing state (Figure 4), the side clearance on the meshing surface of the gears is zero, while there is a certain side clearance on the non – meshing surface. The side – clearance value is determined by the designer based on the gear’s machining accuracy and operating conditions. If the measured side – clearance value is larger than the design requirement, the two gears need to be moved axially inward; if it is smaller, they need to be moved axially outward. This adjustment is usually achieved by changing the width of the two spacer sleeves installed at the front and rear of the bevel gear.
Meshing State with a Larger Bevel Angle: When the bevel angle is larger (Figure 5), the side – clearance value measured at the small end of the bevel gear is smaller than that at the large end. In this case, only a part of the tooth surface at the small end of the bevel gear can effectively transmit power. This leads to accelerated wear of the contact area, reduced gear lifespan, and abnormal meshing noises during operation. Gears in this state are usually either scrapped or, if the side – clearance deviation is not too large, repaired and used as sub – standard products.
Meshing State with a Smaller Bevel Angle: When the bevel angle is smaller (Figure 6), the side – clearance value measured at the small end of the bevel gear is larger than that at the large end. Only a part of the tooth surface at the large end of the bevel gear has normal contact. This also causes problems similar to the state with a larger bevel angle, and the treatment method is similar.
7. Significance of the Meshing Detection Fixture
7.1 Quality Control in Gear Assembly
The meshing detection fixture is of great significance in ensuring the quality of gear assembly. By detecting the meshing conditions of bevel gears before formal assembly, potential problems can be identified and resolved in a timely manner. This reduces the likelihood of problems occurring after assembly, such as gear wear, abnormal noises, and reduced transmission efficiency.
7.2 Cost – Saving and Efficiency – Improvement
Without proper pre – assembly meshing detection, if gears with meshing problems are installed on the equipment, disassembly and replacement will be time – consuming and labor – intensive. This not only increases the cost of labor and equipment downtime but also may cause damage to other components, such as adjusting roller bearings or drive shafts. The use of the fixture can effectively avoid these issues, saving costs and improving production efficiency.
8. Conclusion
The design of the spur bevel gear meshing detection fixture provides a practical and effective solution for detecting gear meshing problems before assembly. By understanding the structure, operation steps, and meshing – analysis methods related to the fixture, manufacturers can better control the quality of gear assemblies. The fixture’s ability to measure side clearance, adjust bevel angles, and analyze meshing states is crucial for ensuring the smooth operation and long – term reliability of mechanical equipment. Future research can focus on further improving the accuracy and automation level of the fixture to meet the increasingly high – precision requirements of the gear – manufacturing industry.
