Abrading – Abrading process – Gear or worm abrading
Reexamination Certificate
2000-03-13
2001-04-24
Banks, Derris H. (Department: 3723)
Abrading
Abrading process
Gear or worm abrading
C451S056000
Reexamination Certificate
active
06220937
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
Gear honing is known as an extremely fine machining process which is nowadays employed frequently, and which favourably influences the noise characteristics of gears in gear drive units. Honing is performed with gear-shaped honing tools both with internal and external teeth which on engagement produce machining marks on the workpiece tooth flanks, that are beneficial for the generating action of the gears in mesh. The honing tools engage with the workpiece teeth at a certain crossed axes angle, producing between the honing tool and the workpiece surface a relative motion that is utilized as a cutting action.
With regard to the dynamic stabiliy, however, the honing process poses problems. Vibrations arise which are intrinsic to the process, and thus hardly avoidable. In general the vibrations are only slight. In the case of certain unsuitable constellations of tooth geometry, workpiece dimensions, E-modules of tool and workpiece etc., however, these vibrations can attain inacceptably high amplitudes, which has a negative influence on the surface quality of the workpieces. The honing tools are thereby heavily stressed, which leads to damage to, or even fracture of their teeth. In the event of a destruction of the honing tool, the vibrations also cause overloading of bearings etc., which is detrimental to the life of the machine. It has been shown that by an increase in the stiffness the vibration response of the machine with respect to the problematics described is only negligibly altered; on the contrary: the load peaks on the honing tool during the process lead to a rapid deterioration in the form of the tool tooth flanks, which in turn demands frequent profile re-dressing. From the U.S. Pat. No. 4,354,328, a worm-shaped honing tool is known which is attached to a spindle, firmly fixed against rotation, but axially and radially spring-loaded via O-rings. This honing tool produces more unfavourable machining marks on the gear, because these run largely in the lengthwise direction of the teeth. The device has the disadvantage that the angular position of the honing tool during honing is undefined. If the angular position of the honing tool changes, e.g. due to non-uniform elasticity of the two radially supporting O-rings, this leads to an irregular machining of the tooth flanks over their depth. Depending on the consistence of the O-rings, the pressure of contact varies with the angle of rotation. Moreover the high frequency alternating load on the O-rings leads to a rapid ageing and to elevated temperatures of the O-rings during honing, which alters their elastic properties and the pressure of contact as honing proceeds.
SUMMARY OF THE INVENTION
The present invention is rooted in the objective of introducing a honing device for gear honing, with which the stated disadvantages of known honing processes can be reduced. This task is solved by way of the combined features of the claims.
The basis of the invention is that, in contrast to the conventional processes, the mass components of the honing tool forcibly induced by the process are reduced and furthermore disconnected from the remaining subassembly of the machine, moreover such that an angular deflection of the honing tool relative to the workpiece axis is prevented. Hereby for one thing the forces exerted on the tool and the workpiece are reduced, while on the other hand, in contrast to the known devices, a geometrically correct reproduction of the tool profile without angular error is assured on the workpiece surface. This is achieved by a suitable selection of the type and arrangement of the spring-loading and damping elements and the guides. The disconnection thus attained is located accordingly as near as possible to the source point. Via the damping elements mechanical energy is extracted from the undesirably oscillating system, so that the system is steadied and stabilized.
Because the spring-loading and damping elements are located between non-rotating parts, a constant contact pressure for a given deflection is attained independent of the angle of rotation of the honing tool. The spring elements are only statically loaded, so that e.g. elastomere components with the necessary intrinsic damping characteristic can also be employed as spring-loading and damping elements.
If the device is also used for repeatably re-dressable honing tools, the geometry of the profiling tool must be transferred very accurately to the honing tool. This means that for the dressing operation (profiling) the degree of freedom must be restricted or eliminated at least in the radial direction. For this a switching mechanism is provided, by which the springloading and damping elements can be activated or de-activated selectively.
REFERENCES:
patent: 4354328 (1982-10-01), Ainoura
patent: 1127176 (1962-04-01), None
patent: 1202097 (1965-09-01), None
patent: 197 24 527 (1998-12-01), None
Banks Derris H.
Browdy and Neimark
Reishauer AG
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