Method for designing tooth shape of involute chain wheel

Abstract

A method for designing an involute chain wheel tooth shape belongs to the technical field of chain wheel design methods, and comprises the following steps: opening AutoCAD software, and using an auxiliary plug-in special for chain wheel tooth shape design in AutoCAD to provide the following parameters: modulus, design tooth number, pressure angle, displacement coefficient, addendum circle diameter, dedendum circle diameter, addendum over-plating fillet radius and dedendum over-plating fillet radius; and the sprocket tooth shape is designed through the auxiliary plug-in. The tooth form of the involute chain wheel designed by the invention can further reduce noise between the tooth-shaped chain and the chain wheel.

Description

Technical Field

[0001] This invention belongs to the technical field of sprocket design methods, specifically relating to a method for designing involute sprocket tooth profiles. Background Technology

[0002] Toothed chains, also known as silent chains, are a type of transmission chain. The national standard in my country is GB / T 10855-2016, "Toothed Chains and Sprockets." A toothed chain consists of a series of alternating toothed plates and guide plates connected by hinged elements such as pins or combinations thereof, with hinged joints between adjacent pitches. Based on the guiding type, they can be divided into: externally guided toothed chains, internally guided toothed chains, and double-internally guided toothed chains.

[0003] Although toothed chains are also known as silent chains, in practical applications, toothed chains, as an important component of the timing system of automobile and motorcycle engines, generally suffer from significant noise and severe wear. Traditional design methods involve manually calculating and drawing tooth profiles from charts, which has drawbacks such as errors in manual calculations, insufficient dynamic analysis, low tooth profile accuracy, long design cycles, poor adaptability, strong reliance on experience, and poor consistency. Summary of the Invention

[0004] This invention discloses a method for designing involute sprocket tooth profiles, aiming to further reduce noise during the operation of toothed chains.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: A method for designing involute sprocket tooth profiles includes: opening AutoCAD software, using an auxiliary plugin in AutoCAD specifically designed for sprocket tooth profiles, providing the following parameters: module, number of designed teeth, pressure angle, displacement coefficient, tip circle diameter, root circle diameter, tip fillet radius, and root fillet radius, and designing the sprocket tooth profile through the auxiliary plugin.

[0006] Preferably, the method involves designing the involute sprocket tooth profile according to the following steps: Step 1: First, determine the module Mn. The module Mn = nominal pitch of the chain / π. The calculated value should be rounded to 3 decimal places. Step 2: Next, confirm the number of teeth Z in the design; Step 3, Selection of pressure angle: For external meshing and internal-external compound meshing round pin toothed chains, when Z≤25, the pressure angle α=31.5°, and when Z>25, the pressure angle α=30°; for internal meshing round pin toothed chains, when Z≤25, the pressure angle α=30°, and when Z>25, the pressure angle α=31.5°. Step 4: Confirm the diameters of the addendum circle and dedendum circle: First, calculate the pitch circle based on the module and number of teeth. Place the center of the meshing chain plate shape on the pitch circle, and arrange the chain plates along the center of the pitch circle. The number of arrays is the number of sprocket teeth. Simulate the chain-like situation, where the rear teeth of the front chain plate partially overlap with the front teeth of the rear chain plate. Connect the centers of the two chain plate holes in the overlapping part and draw extension lines to both sides, so that the ends of the extension lines intersect the circles containing the nearest chain plate holes. Measure the two intersection points. The length between them is the required pin diameter φ of the chain plate. When this diameter is within the error range of 0-0.005mm, it is the pin diameter of the finished chain. This state is the best meshing between the chain plate and the sprocket. After completing the above work, since the tooth tip and tooth root of the sprocket are not allowed to contact the waist height and tooth tip of the chain plate, draw circles tangent to the tooth tip and tooth root respectively. At the same time, shift the circles 0.3mm towards the center to obtain the corresponding circles. The diameters of these two circles are the tooth tip circle and the tooth root circle diameter, respectively. Step 5: Selection of displacement coefficient: The displacement coefficient is initially designed as -1. Observe whether the sprocket tooth profile and the chain plate tooth profile overlap. If they overlap, reduce the displacement coefficient and redraw the tooth profile until there is 0.002mm left at the meshing position of the sprocket and the chain plate. The sprocket tooth profile at this time is the final design tooth profile. Step 6: Select the root transition fillet radius and the tip transition fillet radius, keeping one decimal place: The root transition fillet radius and the tip transition fillet radius are the same. The maximum radius of the single arc is displayed in the auxiliary tool. Based on the maximum radius of the single arc, keeping one decimal place, the double arc transition radius is obtained.

[0007] The beneficial effects of the method for designing involute sprocket tooth profiles according to the present invention are as follows: This invention innovates based on the usage methods of commonly used CAD tools, and its specific advantages are reflected in the following aspects: 1. Improve transmission efficiency and stability; the involute tooth profile, through the evenly distributed contact line length and pressure angle, ensures a smooth meshing process between the chain and the sprocket.

[0008] 2. Extended service life and reduced wear: The involute tooth profile has a uniform contact line length and pressure angle distribution, which can disperse the load and reduce local stress concentration, thereby reducing the wear rate of the tooth surface and extending the service life of the sprocket.

[0009] 3. Reduce noise and vibration: The continuous contact characteristics of involute teeth can reduce meshing impact, reduce transmission system noise and vibration, and improve the equipment operating environment. Attached Figure Description

[0010] Figure 1 : Schematic diagram of the parameters required for the auxiliary tool.

[0011] Figure 2 : Schematic diagram of the chain in step 4.

[0012] Figure 3 : Schematic diagram for measuring the diameter of the pin.

[0013] Figure 4 A schematic diagram showing the extension lines drawn to both sides after connecting the centers of two overlapping circles.

[0014] Figure 5 : Figure 4 A magnified view of a portion of the image.

[0015] Markings in the diagram: 1. Circle 1 (red circle) corresponding to the chain plate hole on the back side of the front chain plate; 2. Circle 2 (black circle) corresponding to the chain plate hole on the front side of the adjacent rear chain plate; 3. The rear teeth of the front chain plate; 4. The front teeth of the rear chain plate; 5. Extend the line connecting the centers of the two overlapping circles to both sides. Detailed Implementation

[0016] The following description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0017] The following embodiments can be understood as illustrating a part of the structure or method of the present invention individually, or as combining the embodiments to explain the broader structure or method of the present invention.

[0018] Example 1: A method for designing involute sprocket tooth profiles includes: opening AutoCAD software and using an auxiliary plugin specifically designed for sprocket tooth profile design. This plugin is an essential toolbox for sprocket drafters, offering multiple functions to assist in better drawing and designing sprockets. It provides the following parameters: module, number of designed teeth, pressure angle, displacement coefficient, addendum circle diameter, dedendum circle diameter, addendum fillet radius, and dedendum fillet radius. The sprocket tooth profile is then designed using the auxiliary plugin.

[0019] The advantages of this invention are: it avoids the defects of traditional design, such as manual calculation errors, insufficient dynamic analysis, low tooth profile accuracy, long design cycle and poor adaptability, strong dependence on experience and poor consistency.

[0020] Example 2: Based on Example 1, this example discloses: The method described above designs the involute sprocket tooth profile according to the following steps: Step 1: First, determine the module Mn. The size of the module Mn is related to the nominal pitch of the chain. Module Mn = nominal pitch of the chain / π. The calculated value is rounded to 3 decimal places. Step 2: Next, confirm the number of teeth Z. The number of teeth Z is selected according to the transmission requirements. For small and medium-sized toothed chains and Hy-Vo toothed chains for high-speed transmission, Z is usually 15~60. For internal-external compound meshing toothed chains and Hy-Vo toothed chains, Zmax should be determined by the necessary conditions for internal-external compound meshing. The necessary conditions include: consistency between module and pressure angle, tooth ratio relationship, center distance calculation, avoidance of undercut and interference, and practical application suggestions; or the number of teeth Z can be selected according to customer requirements. Step 3, Selection of pressure angle: For external meshing and internal-external compound meshing round pin toothed chains, when Z≤25, the pressure angle α=31.5°, and when Z>25, the pressure angle α=30°; for internal meshing round pin toothed chains, when Z≤25, the pressure angle α=30°, and when Z>25, the pressure angle α=31.5°. Step 4: Confirm the diameters of the addendum circle and dedendum circle: (e.g.) Figure 2 As shown, first, calculate the pitch circle based on the module and number of teeth. Place the center of the meshing chain plate shape on the pitch circle, and then array the chain plates along the center of the pitch circle. The number of arrayed plates is the number of sprocket teeth (e.g., 31 sprocket teeth correspond to 31 chain plates). Simulate the chain-like situation, as shown... Figure 4 As shown, the rear teeth 3 of the front chain plate overlap with the front teeth 4 of the rear chain plate (as mentioned earlier, each chain plate has 2 teeth, and 31 chain plates have 62 teeth. To align with the 31 tooth grooves of the sprocket, the teeth of adjacent chain plates need to overlap, i.e., the two overlapping teeth of two chain plates correspond to one sprocket tooth groove). Figure 3 , 4 As shown in Figure 5, connect the centers of the two overlapping chain plate holes and draw extension lines to both sides, so that the ends of the extension lines intersect the circle containing the nearest chain plate hole. Measure the length between the two intersection points, which is the required pin diameter φ of the chain plate. When this diameter is within the error range of 0-0.005mm, it is the pin diameter of the finished chain. Through simulation verification and experience accumulation, this state is the optimal meshing of the chain plate and the sprocket. After completing the above work, based on the fact that the tooth tip and tooth root of the sprocket are not allowed to contact the waist height (i.e., the top of the tooth groove of the chain plate) and tooth tip, draw circles tangent to the tooth tip and tooth root respectively, and offset the circles 0.3mm towards the center to obtain the corresponding circles. The diameters of these two circles are the tooth tip circle and the tooth root circle diameter, respectively. Step 5, Selection of displacement coefficient: Since the displacement coefficient cannot be accurately obtained, it is generally designed with a displacement coefficient of -1 during the tooth profile drawing process. The overlap between the sprocket tooth profile and the chain plate tooth profile is observed. If they overlap, the displacement coefficient is reduced and the tooth profile is redrawn until 0.002mm is left at the meshing position of the sprocket and the chain plate. The sprocket tooth profile at this time is the final designed tooth profile. Step 6: Select the root transition fillet radius and the tip transition fillet radius, retaining one decimal place: e.g. Figure 1 As shown, the root transition fillet radius and the tip transition fillet radius are the same. The maximum radius of the single arc is displayed in the auxiliary tools. The double arc transition radius is obtained by rounding the maximum radius of the single arc to one decimal place. For example, if the single arc radius is displayed as 1.2133mm, then the radius of the double arc transition is set to 1.2mm, and the tip transition fillet radius is also set to 1.2mm.

Claims

1. A method for designing involute sprocket tooth profiles, characterized by comprising: Open AutoCAD software and use the auxiliary plugin in AutoCAD specifically for sprocket tooth design. Provide the following parameters: module, number of teeth, pressure angle, displacement coefficient, addendum circle diameter, dedendum circle diameter, addendum fillet radius, and dedendum fillet radius. Design the sprocket tooth profile using the auxiliary plugin.

2. The method for designing involute sprocket tooth profiles as described in claim 1, characterized in that: The method described above designs the involute sprocket tooth profile according to the following steps: Step 1: First, determine the module Mn. The module Mn = nominal pitch of the chain / π. The calculated value should be rounded to 3 decimal places. Step 2: Next, confirm the number of teeth Z in the design; Step 3, Selection of pressure angle: For external meshing and internal-external compound meshing round pin toothed chains, when Z≤25, the pressure angle α=31.5°, and when Z>25, the pressure angle α=30°; for internal meshing round pin toothed chains, when Z≤25, the pressure angle α=30°, and when Z>25, the pressure angle α=31.5°. Step 4: Confirm the diameters of the addendum circle and dedendum circle: First, calculate the pitch circle based on the module and number of teeth. Place the center of the meshing chain plate shape on the pitch circle, and arrange the chain plates along the center of the pitch circle. The number of arrays is the number of sprocket teeth. Simulate the chain-like situation, where the rear teeth of the front chain plate partially overlap with the front teeth of the rear chain plate. Connect the centers of the two chain plate holes in the overlapping part and draw extension lines to both sides, so that the ends of the extension lines intersect the circles containing the nearest chain plate holes. Measure the two intersection points. The length between them is the required pin diameter φ of the chain plate. When this diameter is within the error range of 0-0.005mm, it is the pin diameter of the finished chain. This state is the best meshing between the chain plate and the sprocket. After completing the above work, since the tooth tip and tooth root of the sprocket are not allowed to contact the waist height and tooth tip of the chain plate, draw circles tangent to the tooth tip and tooth root respectively. At the same time, shift the circles 0.3mm towards the center to obtain the corresponding circles. The diameters of these two circles are the tooth tip circle and the tooth root circle diameter, respectively. Step 5: Selection of displacement coefficient: The displacement coefficient is initially designed as -1. Observe whether the sprocket tooth profile and the chain plate tooth profile overlap. If they overlap, reduce the displacement coefficient and redraw the tooth profile until there is 0.002mm left at the meshing position of the sprocket and the chain plate. The sprocket tooth profile at this time is the final design tooth profile. Step 6: Select the root transition fillet radius and the tip transition fillet radius, keeping one decimal place: The root transition fillet radius and the tip transition fillet radius are the same. The maximum radius of the single arc is displayed in the auxiliary tool. Based on the maximum radius of the single arc, keeping one decimal place, the double arc transition radius is obtained.

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