Description
Worm Shaft Endless Screw Thread Roller
Classification Of Worm Drives
According To The Shape Of Worm Indexing Surface, Worm Drive Can Be Divided Into Three Categories: Cylindrical Worm Drive, Toroidal Worm Drive And Conical Worm Drive.
The Worm Indexing Surface Is a Part Of The Inner Surface Of The Ring. The Worm Drive With Straight Theoretical Tooth Profile In The Plane Of The Worm Axis Is Called Straight-Profile Toroidal Worm Drive, Commonly Known As “Spherical Worm Drive”. It Began In 1921 In The United States Shipbuilding Industry, Its Representative Product Is The United States Cone Drive, Since The 1950s In China Has Been Promoted And Applied.
Compared With The Conventional Cylindrical Worm Drive, This Kind Of Worm Has More Teeth At The Same Time. The Condition Of Oil Film Formation Of Double-Line Contact Line Is Good, And The Normal Curvature Radius Induced By The Contact Line Of Two Teeth Surface Is Large. Therefore, The Bearing Capacity Is 1.5-3 Times That Of The Common Worm With The Same Central Moment (Small Value Is Suitable For Small Central Moment, Large Value Is Suitable For Large Central Moment). When The Same Power Is Transmitted, The Center Moment Can Be Reduced By 20%-40%. Because Of Its Excellent Performance, The United States, Japan, Russia And Other Countries Have Widely Used This Kind Of Transmission As One Of The Main Forms Of Power Transmission.
The Center Moment Of The American Product Series Is 15-1320, The Speed Ratio Is 5-343000, And The Maximum Transmission Efficiency Can Reach 97%. After 40 Years Of Research And Development In China, The Current Production Varieties Of This Kind Of Worm Are Also Considerable, The Maximum Central Moment Can Reach 1200_, The Minimum Tooth Number Ratio Is 5, The Number Of Worm Heads Is 6, And The Maximum Transmission Efficiency Can Reach 94%. The Worm Drive Can Be Divided Into Two Types: Original Type And Trimming Type.
The Helical Tooth Surface Of The “Primitive” Straight-Profile Toroidal Worm Is Formed As a Straight Line Tangent To The Forming Circle And Located In The Plane Of The Worm Axis. While Rotating At Equal Angular Speed Around The Center Of The Forming Circle, It Rotates At Equal Angular Speed Around The Worm Axis With The Forming Circle. This Straight Line Forms a Track In Space. Trace Surface Is The Tooth Surface Of Straight Toroidal Worm. Because The Generating Line Of Worm Tooth Surface Is Straight Blade, The Spiral Surface Of Worm Is a Non-Expandable Straight Surface Formed By Straight Blade Rather Than By Envelope, Which Is Difficult To Grind. The Manufacturing Process Of Steel Bar For This Kind Of Worm Is Complex, And It Is Difficult To Obtain High-Precision Transmission. This Is The Main Disadvantage Of Straight Toroidal Worm Transmission.
The Formation Of The Spiral Surface Of The Straight Profile Hourglass Worm Is Basically The Same As That Of The Original Type. The Difference Lies In That The Processing Parameters Are Changed According To The Modification Curve Required By The Design. Generally, There Are Two Kinds Of Process Methods: Modification At Different Speed And Modification At Different Speed Ratio. The Method Of Modification With Different Speed Is That The Position Of Tool And The Fixed Transmission Ratio Are Different From The Position And Speed Ratio Of Worm Pair When Machining Worm. The Modification Method Of Speed Change Ratio Is That The Instantaneous Transmission Ratio Changes According To a Certain Rule During Machining.
The Straight Profile Toroidal Worm Drive Composed Of The Worm Machined By The Modification Processing Method And The Worm Gear Machined By The Modification Hob Eliminates The Contact Between The Central Edge Line Of The Worm Gear Tooth Surface. It Not Only Improves The Assembly Conditions, Reduces The Error Sensitivity, But Also, More Importantly, Enlarges The Contact Area And Shapes Compared With The Original Worm Drive. Because Of The Good Oil Film Forming Conditions And The Average Load Between The Teeth, The Load Carrying Capacity, Meshing Performance And Transmission Efficiency Are Higher Than Those Of The Original Type.
