Theoretical research development of Gleason teeth spiral bevel gears
The concept of spiral bevel gears was proposed by the French geometer T. Olivier as early as the early 19th century. He suggested the envelope surface method to solve the conjugate tooth surface. He demonstrated the possibility of using the auxiliary surface to obtain the conjugate surface of line or point contact.
Later, the Russian scholar Φ. И. Гохман established the theoretical basis of the analytical principle of gear meshing. For a long time, the academic research of spiral bevel gears used analytical methods. Since the tooth surface of the spiral bevel gear is a complex helical surface, it requires the tool to produce complex helical cutting motion with the part during processing. Due to machine tools’ limited freedom and precision at that time, this hobbing movement could not be realized. Therefore, for nearly a century after that, the research on spiral bevel gears only stayed at the theoretical stage, and no natural body was processed.
Paul Bottcher, a German, obtained a patent for spiral bevel gears processing technology and published a series of patent reports on spiral bevel gears processing technology. In the report, he proposed using the milling cutter as the tool for machining the tooth surface of the spiral bevel gear, and based on this; he designed the prototype machine for machining the spiral bevel gear.
In 1913, James. Gleason, an engineer of Gleason Company in the United States, designed the first face-cutting machine tool for spiral bevel gears. In 1919, Gleason Company obtained Paul Bottcher’s invention patent and tried to improve the processing of spiral bevel gears along the method of single-tooth indexing processing. In the process of improvement, Gleason Company found that under the condition that the tooth heights of the large and small end faces are the same, the teeth on the small end face are relatively tapered and prone to breakage during service; therefore, the concept of sharp teeth was innovatively proposed. And applied to the processing of spiral bevel gears, developed a very representative machine tool — Gleason No. 16 machine tool, and began mass production of spiral bevel gears for the American automobile industry. The introduction of the concept of sharp teeth profoundly impacts the processing of subsequent spiral bevel gears. Today, the tapered spiral bevel gear is also the most widely used type of spiral bevel gear.
Early Gleason techniques were based on the principle of local conjugation. Specifically, it can be explained as follows: first process the wheel gear, then select a reference point on the tooth surface of the wheel gear, analyze the first-order or second-order contact parameters such as the curvature and average vector of the pinion gear that match it and finally carry out according to the requirements. Corrections and adjustments.
However, this early local conjugate processing method has obvious defects: first, the regional conjugate analysis is very cumbersome, and the processing efficiency is very low; The curvature is very difficult; therefore, the machining accuracy is also difficult to guarantee.
To solve this problem, Professor Litvin, a famous American scholar, put aside the Gleason technology and pioneered the local synthesis method in the 1960s, which overcomes the defect that the local conjugate principle cannot pre-control the second-order contact parameters. The basic idea is: to cut out the wheel gear first, select a reference point on it, then calculate the central curvature and main direction at the reference point, and preset three second-order contact parameters at the reference point (including transmission. The first-order derivative of the ratio function, the tangent direction of the contact trace on the wheel gear tooth surface and the length of the semi-major axis of the instantaneous contact ellipse) to find the central curvature and main direction of the pinion gear tooth surface at the reference point, and finally determine the pinion gear adjustment parameters. Later, Professor Litvin made the transmission of the spiral bevel gear more stable by presetting the parabolic transmission error function, and the vibration and noise were significantly reduced.
In recent years, Gleason has successfully developed a high-order motion error design theory, the so-called Universal Motion Principle (UMC) and Critical Motion Graph (UMG), which provides a theoretical basis for high-precision grinding. UMC means that in the process of spiral bevel gear machining, the variables from 0th order to 4th order are controlled by the 4 movements of vertical, radial, spiral and roll ratio correction of NC6 axis to realize the spiral bevel gear High precision machining and modification. And UMG refers to using UMC’s action to grind the teeth so that the UMC can be expressed in the grinding state. UMC technology can simultaneously eliminate transmission errors of 1st order to 5th order or even higher demand. While significantly improving machining accuracy and reducing vibration and noise, the production efficiency will also be considerably enhanced because it avoids post-adjustment processes such as grinding teeth.
Manufacturing development of Gleason teeth spiral bevel gears
The development of spiral bevel gear processing technology is inseparable from the development of spiral bevel gear processing machines. The result of its processing technology is the continuous progress of machine tools.
Spiral bevel gears were proposed in 1820. However, due to the difficulty of processing and the design and manufacture of machine tools, it has only stayed at the stage of theoretical models for nearly a century. It was not until 1910 that the first pair of fully conjugated equal-height spiral bevel gears appeared. The German Paul Bottcher processed this pair of gears with a milling cutter.
In the subsequent spiral bevel gear equipment, Gleason made a significant contribution. From the end of the 19th century to the beginning of the 20th century, Gleason developed the first bevel gear planing machine and the first spiral bevel gear face cutting machine. In 1919, Gleason Company obtained Paul Bottcher’s patented technology and began further research and innovation on the spiral bevel gear machine model. In this stage, Ernest Wildhaber, a researcher of Gleason Company, innovatively introduced the concept of sharp teeth, which avoided the problem that the teeth at the small end were too thin and easy to break and provided a new way for the processing of spiral bevel gears in the future. The idea greatly affected the future processing and manufacturing of spiral bevel gears. The Gleason No. 16 machine tool is representative of this period.
In the 1920s, Gleason Company creatively proposed the concept of axis-offset hypoid gears to improve the coincidence and bearing capacity of bevel gears, and in 1925 launched the No. 16H machine tool that could process hypoid bevel gears, realizing the industrialized production of hypoid gears. In the second year, it began to mass-produce hypoid automotive gears for Ford.
Later, Gleason proposed and realized the machining principle of the knife tilt method, which has epoch-making significance for the machining of spiral bevel gears. The spiral bevel gear machine tool adds a tool tilt mechanism, which adds more adjustable processing parameters when processing the spiral bevel gear. The obtained gear tooth surface is more accurate and easier to correct, significantly improving the coincidence degree. And processing efficiency. Afterwards, the proposal and realization of the point contact tooth surface theory greatly improved the tooth surface accuracy and contact performance of spiral bevel gears.
In 1954, Gleason introduced the No. 116 gear milling machine. This type of machine tool is the most widely used spiral bevel gear processing equipment in the world so far. It has been imported and imitated by many countries and profoundly impacts the development of spiral bevel gear processing equipment. This machine tool adopts the early complex mechanical transmission mode and has a knife tilting mechanism. Because its transmission mechanism mainly relies on complicated automatic means, the relevant parameters need to be calculated manually, and pre-processes such as trial cutting are also required, so The whole process is not only time-consuming and labour-intensive but also has significant manufacturing errors, but it is still the first machine tool that can process spiral bevel gear pairs that conform to advanced meshing theory. Due to the low manufacturing cost of this type of machine tool, most enterprises still use this type of machine tool in actual production.
In 1973, to avoid errors caused by complex mechanical transmission mechanisms, Oerlikon applied PLC control system to the S17 machine tool for the first time and developed the first spiral bevel gear processing equipment with simple numerical control. It also marks the end of the traditional mechanical machine tool stage and the beginning of the numerical control stage.
Afterwards, Gleason launched the Gleason Bevel Gear Manufacturing Expert System GEMS. GEMS is an advanced digital bevel gear manufacturing technology. Its purpose is mainly to match with Phoenix series CNC spiral bevel gear milling and grinding machines to realize the integration of processing equipment and network.
