Machine element or mechanism – Gearing – Rotary bodies
Patent
1989-12-20
1991-11-26
Herrmann, Allan D.
Machine element or mechanism
Gearing
Rotary bodies
74409, F16H 5518
Patent
active
050673645
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a device for eliminating mechanical rattle between a pair of inter-engaging gears, comprising a gear element cooperating with one gear, said gear element being rotatably mounted on a hub portion joined to said one gear, having the same tooth profile and number of teeth as the gear and being connected to the gear via rotationally resilient elements, which are pre-tensioned in the engagement position of the gears.
In most autombiles with a manual transmission there is a mechanical rattle when idling. The noise is produced when the teeth of the gears strike each other at a certain frequency since the gears in the gear box are imparted an acceleration due to the non-uniform running of the engine at low rpm. The oscillations which are produced are transmitted via the clutch and the input shaft and are caused not only by the engine but also the drag torque of the gear box. The engine flywheel has a greater angular acceleration and oscillation amplitude at low engine speeds, so that idle rattle increases in most cases with decreasing rpm. A low idling rpm is, however in general desirable since it improves fuel economy.
Several different methods of reducing or completely eliminating idling rattle in gear boxes are known. It is for example possible to use clutches with special stiffness and dampening, to increase the moment of intertia of the flywheel of to reduce the backlash between the gears. It is also possible to use friction brake in the gear box, to pre-tension the gears or alter their moments of inertia. In most cases these methods are either not sufficiently effective for reducing rattle or they are expensive since they require relatively extensive modifications of existing components. As regards the reduction of backlash, it is for example not practically possible to achieve a small enough play to provide effective reduction of rattle. The pre-tensioning devices hitherto brought into use have had a tendency to produce their own additional noises.
By means of a device of the tape described in the introduction, which is known by for example EP 0 199 265, it is possible to achive an effect which is nearly the same as when the backlash between the gears is practically completely eliminated. The known device has gear members interconnected with the aid of a pre-tensioned leaf spring fixed between pins, said spring being housed in a space formed by grooves in opposing sides of gear members. Such a device is relatively complicated to manufacture and assemble and there is a risk that it will produce its own rattle, especially when wear has caused play in the spring mounting.
The purpose of the present invention is to acheive a device of the type described in the introduction, which is sinple and inexpensive to manufacture and assemble and which eliminates the risk of producing its own noise.
This is achieved according to the invention by virtue of the fact that the resilient elements comprise elastic elements which are disposed in opposing, circumferentially spaced cavities in the hub portion and in the circumferential inner surface facing the hub of gear elements and are disposed to keep the gear elements and said one gear angularly displaced relative to each other before they are brought into engagement with the other gear.
The device according to the invention has a low production cost and is simple to assemble. The cavities in the gear hub and the gear element, respectively, can be produced by simple milling operations. By virtue of the fact that the cavities lie in the radially inner protion of the gear, they do not affect the tooth shape during the quenching process. Assembly is simplified by virtue of the fact that the elastic elements can in principle lie loosely in the cavities. The device produces no noise by itself if elastic elements of rubber are used, which elements not only provide a pre-tensioning torque but also attenuate oscillations.
The invention is described in more detail below with reference to an example shown in the accompanying drawings, where
FIG. 1 show
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patent: 2845809 (1958-08-01), Hetzel
patent: 3318193 (1967-05-01), Rogg
AB Volvo
Herrmann Allan D.
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