In recent years, the main direction of automobile gear manufacturing is shifted from commercial vehicle gears to passenger vehicle gears. The manufacturing process of gears is also traditional hobbing (or gear shaving) + gear shaving. More and more gear hobbing (or Gear teeth) + grinding teeth (or strong honing), gear manufacturing precision increased 1-2. This is the result of keen competition in the automotive market and a manifestation of the continuous improvement of manufacturing technology. In recent years, the rise of HEVs and electric vehicles has also led to the improvement of the manufacturing precision of automobile gears. Therefore, the manufacturing process of mass production of automobile gears must also be consistent with it.

 

1. Cylindrical gear grinding:

Gear grinding as a gear finishing process for many years, from the forming grinding wheel, double cone grinding wheel grinding to the worm gear, gear grinding is now a large number of basic use of worm gear grinding, its benefits are: High production efficiency (some manufacturers gear grinding speed up to 100 m / s, beat up to 13 --- 40 seconds / piece), high precision (up to DIN 4 - 7), the cost is relatively low, And can solve the problem of larger heat distortion;

 

1.1 grinding process difficult:

The dynamic precision of the machine tool is stable (especially in mass production, long-term 2,3 shift work, gear accuracy stable at DIN 6-7 level), the reliability is better;

 

High precision fixtures, and easy to load and unload the workpiece automatically;

 

Wheel dresser high precision and durability, grinding wheel dressing can quickly achieve the requirements of gear grinding, wheel dressing time is shorter;

 

Self-sharpening requirements of the grinding wheel and long service life (each dressing a large number of grinding wheel), line speed is high (up to 100 m / s), grinding wheel to meet the high-speed manufacturing fewer suppliers;

 

1.2. The new hard grinding process:

Due to the competition in the automobile market and the increasing noise requirements of hybrid vehicles and electric vehicles, the German Volkswagen proposed the requirements of one tooth and three sections for the gear grinding process in 2007 (that is, the three directions of the tooth direction measurement, the tooth direction Direction measured three cross-section, a single gear on one side of the tooth surface measured a total of 9 points of the error value); the past only requires a tooth-section (that is, the direction of the tooth-shaped middle section measured tooth direction measured in the middle Section, a single gear on one side of the tooth surface measurement of a total of 5 points of the coordinate error value); Now equal to the required gear on the side of the surface to be measured nine points in the spatial position must be qualified, and a tooth on both sides of the surface The space of 18 points must be qualified, which is really hard to achieve. There are very few grinding machine manufacturers that can meet this requirement internationally.

 

In order to achieve this requirement, Volkswagen first made a request with Leissehörre AG of Switzerland. After the company repeatedly redesigned and tested the control software for grinding machine tools and wheel dresser, and finally met the general public's requirements, the public introduced the mill Teeth one tooth three cross-section requirements, and widely used in the new product design. At present, in order to achieve a more stable new user requirements, the company has been upgrading the version of the grinding machine control software several times.

 

With the development of electric vehicles, the manufacturing precision of automobile gears may be put forward further requirements, so we must have some ideas to deal with. At the same time as a transmission designer must consider: your newly designed products can be processed out? Your new request requires the support of the appropriate technical documentation.

 

2. Strong honing helical gear:

 

In the past, the honing process was only the external honing wheel active rotation, and the gear workpiece followed the honing wheel rotation and was processed, similar to the shaving process, this process just to improve the gear surface roughness, the basic can not improve the gear accuracy. Now the powerful honing processing honing wheel and the workpiece is forced to rotate at a fixed speed ratio, and the use of honing cylindrical wheel outer hone, which increases the meshing gear coincidence coefficient, increased grinding force, increased Processing efficiency (some manufacturers honing wheel speed up to 2000 rev / min, up to 30 seconds / piece), and in a certain range to improve the gear accuracy of DIN 4-7 level.

 

2.1. Strong honing process difficult:

The dynamic precision of the machine tool is stable (especially in mass production, long-term 2,3 shift work, gear accuracy stable at DIN 6-7 level), the reliability is better;

High precision fixtures, and easy to load and unload the workpiece automatically;

 

Honing wheel dresser is a gear-shaped, high precision and durability requirements, honing wheel trim quickly achieve honing precision requirements, repair time should be short;

 

Honing wheel requires self-sharpening, and long service life (that is, the number of parts machined per honing wheel more);

 

The precision of hobbing and chamfering of the machined parts is good. The deformation of gear steel material is small, and the requirements of the supplier are single. The deformation of gear parts must be controlled well and the deformation is regular, the honing margin can not be large, otherwise the honing wheels damaged;

 

2.2 new honing gear difficult points: the basic and grinding the same, if the accuracy of parts to be machined, honing wheel dresser will be difficult to manufacture, the price is more expensive;

 

3. Inner cylinder bevel gear ring powerful car tooth processing:

 

This is called according to the old Soviet teaching materials, the domestic also called "inserted roll", "scratch teeth" and so on, the foreign said "Power Skiving", "Schaelen", "Scudding". Due to the extensive use of automotive automatic transmissions in recent years, the processing volume of thin-walled, high-precision ring gear parts in planetary rows has gradually increased. In the past, the plug-in gear processing alone could no longer meet the demand for production SD25 full CNC gear shaping machine beat 25 points / piece), so the car is also being introduced tooth machining, which is the radial feed gear, there are circumferential feed. Tooth ring gear tooth processing beating machining faster than many, the fastest 2.5 points / piece, the accuracy of up to DIN 6-8 level, surface roughness Rz 3. Its tool is similar to the gear shaper, which also can be machined cylindrical gear, and the changeover time only 30 minutes. Now able to batch stability of high-precision thin-walled tooth toothed ring gear manufacturers are not many, so the order should be based on the specific circumstances to make a choice.

 

In addition, I think this thin-walled inner ring for processing must also pay attention to the choice of machine tool fixture: you must use multi-valve hydraulic fixture, 4, 6, 8 petals are too little fixture, at least 10 or more, . Require more petal is to tighten the force to even thin-walled inner ring, does not produce clamping deformation, the workpiece is not elastic recovery after deformation, to ensure the processing quality is not damaged.

 

4. Thin-walled cylindrical helical bevel gear spiral teeth:

 

Spiral Saw Blazer cylinder ring

Now the planetary row of thin-walled inner ring gear parts greater demand, the previous processing technology has been unable to meet the needs of mass production, so helical broaching machine bevel gear ring was gradually adopted by some of the major automatic transmission factory, And its high productivity (up to 60 seconds / piece), easy to adjust the characteristics of more and more show superiority. However, the machining precision of this machining method is mainly determined by the manufacturing precision of the gear helical broach. Now few manufacturers are able to manufacture the helical broach of the thin-walled inner ring helical gear with high accuracy (DIN class 8). Therefore, Widely used are subject to extreme restrictions.