Our internally toothed gears
A typical application is the internally toothed ring gear in a planetary gearbox. Together with the sun gear and planetary gears, it forms a gear stage capable of transmitting high torques within a confined space. Such solutions are used, among other things, in industrial gearboxes, automotive transmissions, wind turbines, machine tools, robotic systems, and mobile machinery.
We manufacture internal gear teeth according to drawings and technical specifications. Depending on the component and quantity, we can produce custom-made parts as well as small production runs.
Internal-tooth gears for demanding transmission applications
Before placing an order, the following questions often arise:
Spare parts present an additional challenge. The new internal gear must not only meet the dimensions specified in the drawings but also fit the existing mating gears, bearing locations, and mounting dimensions.
Have internal-tooth gears manufactured according to drawings
The following data is particularly helpful for a thorough production inspection:
Module & Number of Teeth
Engagement Angle, Profile Offset, and Tooth Width
Base circle and top circle diameters
Fit and Tolerance Specifications
For many applications, gear shaping is a viable option. In this process, a shaping cutter creates the internal gear teeth through a coordinated rolling motion between the tool and the workpiece. For suitable production runs and geometries, broaching can also be used. The most appropriate method must be determined based on the specific component.
Advantages of Internal-Tooth Gears in Mechanical Engineering
In a planetary gearset, multiple planetary gears can mesh simultaneously with the internally toothed ring gear. This allows for compact gear stages with high gear ratios.
Coaxial Arrangement of Input and Output
The input andoutput shafts can be arranged on the same axis. This simplifies the design of gearboxes where lateral offset must be avoided.
High Torque Transmission
In planetary gearboxes, the load can be distributed across multiple planetary gears. This enables the transmission of high torques within a comparatively small assembly.
Smoother Tooth Engagement
With proper design, lower sliding speeds occur at the tooth flanks between internally and externally toothed gears than with some externally toothed gear pairs. This can affect operating noise and friction.
Compact integration into assemblies
The ring gear can enclose multiple gears while also serving as part of the gear housing or a load-bearing assembly.
Suitable for Various Gear Ratios
Depending on whether the sun gear, ring gear, or planet carrier is driven, held in place, or used as the output, different gear ratios can be achieved.
Use in Applications with High Power Densities
Internal-tooth ring gears are therefore frequently used in industrial gearboxes, vehicle drivetrains, wind turbines, and mobile machinery.
Internal-tooth Gears and How They Work
In an internally toothed gear, the teeth point inward. The meshing externally toothed gear runs inside the hollow gear.
The direction of rotation differs from that of a pair of external-tooth gears. Two external-tooth gears rotate in opposite directions. An internal-tooth ring gear and an external-tooth gear meshing with it rotate in the same direction when they are in direct mesh.
Internal gearing is used particularly often in planetary gearboxes. These consist of:
- A central sun wheel
- Several orbiting planetary gears
- An internally toothed hollow gear
- A planetary carrier
The planetary gears mesh with both the sun gear and the ring gear. Depending on which component is driven or held stationary, different motion patterns and gear ratios result.
By using multiple planetary gears that bear the load simultaneously, the load can be distributed across multiple tooth contacts. However, this requires that the gearing, bearings, and component geometry be designed in such a way that the load is actually transmitted evenly.
Internal-tooth gears for planetary gearboxes and industrial equipment
Internal-tooth gears are used in numerous industries. The most common application is in planetary gearboxes.
Typical applications include:
Internal-tooth gears with special manufacturing requirements
The production of internal threads is generally more complex than that of comparable external threads. The tool operates inside the component. As a result, tool access, the component contour, and chip removal are more severely restricted.
Several points should be taken into account early in the design process:
Rolling is suitable for many internal gears because the tool can operate inside the hollow gear even when the outer diameter is limited. Broaching can be an alternative for compatible components and higher production volumes, but it requires a component-specific broaching tool.
The economically viable solution therefore does not depend solely on the interlocking design. Batch size, repeat order frequency, part geometry, and subsequent machining steps also play a role.
Internal-tooth gears from Dittler GmbH
Our services are geared specifically toward companies that do not require standard gears. Often, the request involves a drawing, an existing assembly, a replacement part, or a small batch that must fit a specific machine.
Our manufacturing capabilities include, among other things:
Our quality management system is certified according to DIN EN ISO 9001. For inspections, we have standardized measurement procedures as well as a physically separate measurement room equipped with 3-coordinate measuring technology.
Internal-tooth gears for compact and heavy-duty drives
The internal teeth mesh with one or more external-tooth gears. In planetary gear systems, this arrangement enables compact power distribution across multiple planetary gears.
Manufacturing requires appropriate production processes and early coordination of component geometry. Tool access, gear tooth data, tooth count differences, and mating gears must be taken into account during the planning phase.
We manufacture internally toothed gears according to drawings, either as single pieces or in small batches. In doing so, we tailor the machining process to the specific component and its intended function.
Request Information on Internal-Tooth Gears Now
Send us your drawing and the available technical data via the contact form. Information regarding the module, number of teeth, pitch width, material, heat treatment, tolerances, and quantity is particularly helpful.
For replacement parts, please also provide information—if possible—about the meshing gears and the existing assembly. Based on this information, we can assess the manufacturing process and the feasibility of producing the component.
Frequently Asked Questions About Internal-Tooth Gears
What is an internally toothed gear?
An internally toothed gear has its teeth on the inner surface of a ring-shaped component. It is therefore often referred to as a ring gear. An externally toothed mating gear runs inside this ring gear and meshes with the teeth from the inside. This design is used particularly frequently in planetary gear sets.
What are the advantages of an internally toothed ring gear?
An internally toothed ring gear enables compact gear design and a coaxial arrangement of the input and output shafts. In planetary gearboxes, multiple planetary gears can transmit load simultaneously. This makes it possible to achieve high torques and large gear ratios within a small installation space.
How does internal gearing differ from external gearing?
In an external gear, the teeth are located on the outer circumference of the gear. In an internal gear, they are located inside a ring-shaped component. Furthermore, an internal gear and a directly meshing external gear rotate in the same direction. Two external gears, on the other hand, rotate in opposite directions.
Which manufacturing processes are suitable for internal gear teeth?
Internal gears are often manufactured by gear hobbing or broaching. Gear hobbing is suitable for components of various sizes and smaller production runs. Broaching can be cost-effective for suitable geometries and larger production runs, but requires a tool specifically designed for the gear. The choice depends on the component, material, and batch size.
Why is the manufacturing of internally toothed gears more complex?
The tool must operate within the internal gear. This results in less space for movement and limits the options for tool withdrawal and chip removal. Shoulders, blind holes, and small diameters can further complicate the machining process. Inspecting the internal tooth flanks also requires appropriate measurement methods.
What does "tooth interference" mean in the context of internal gear teeth?
Tooth interference refers to a geometric conflict between the teeth of the internal gear and the meshing external gear. It can occur if the difference in the number of teeth is too small or if the profile and pitch circles have not been properly designed. In this case, the gears may not be able to be assembled, or the tooth tips may collide during operation.
What information is needed to manufacture an internally toothed gear?
We require as complete information as possible regarding the module, number of teeth, mesh angle, profile offset, tooth width, and tolerances. In addition, please provide the material, heat treatment, component dimensions, and quantity. Information about the meshing partner gears helps identify potential geometric conflicts early on.
What is the function of the ring gear in a planetary gearset?
The ring gear surrounds the planetary gears and meshes with their outer teeth via its inner teeth. Depending on the gearbox design, it may be stationary, driven, or serve as an output gear. Together with the sun gear, planetary gears, and planet carrier, it determines the gear ratio of the gear stage.
Can internally toothed gears be manufactured as single pieces?
Yes. Internally toothed gears are often required as one-off parts for special-purpose machinery, repairs, or test setups. Whether custom manufacturing is technically and economically feasible depends on the gear size, the manufacturing process, and the tools required. When standard tools are available, small production runs can often be produced efficiently.
Can internal threads be cut in blind holes?
Blind-hole gear teeth are generally possible, but they place higher demands on the tool and the part geometry. There must be sufficient space at the end of the gear tooth for the tool to retract. If this space is lacking, it may not be possible to cut the gear tooth to the desired depth. The design should therefore be coordinated with the manufacturing process at an early stage.
What materials are suitable for internally toothed gears?
The choice of material depends on torque, rotational speed, wear requirements, size, and the intended heat treatment. Quenched and tempered steels or case-hardened steels are frequently used. Depending on the application and load, other steels, cast materials, or engineering plastics may also be suitable.
Why do internally toothed gear pairs often run more smoothly?
Due to the geometry of the internal tooth engagement, the sliding speeds between the tooth flanks can be lower than in comparable externally geared pairings. In addition, planetary gears can utilize multiple tooth engagements simultaneously. However, actual operation also depends on gear quality, bearings, lubrication, load distribution, and assembly.