A reduction gear unit

Abstract

Described is a reduction gear unit (101, 102, 103) for the number of revolutions of a drive shaft for transmitting the motion between a motor and an actuator. The reduction gear unit (101, 102, 103) comprises, on a load-bearing frame (201, 202), an input shaft (301) mounted as one with the drive shaft of the motor and rotatable about an axis of rotation (X), as well as an output shaft (701), designed to be associated with an actuator. There is also a toothed gear (401) designed to be connected with the input shaft (301) by interposing at least one pair of eccentric gears (501, 502) engaging with the input shaft (301). These eccentric gears (501, 502) comprise a first (501) and a second (502) eccentric gear designed to act simultaneously, directly or indirectly, on the toothed gear (401) and positioned relative to each other in such a way that the respective centres of rotation (510, 520) are positioned symmetrically relative to the axis of rotation (X). The output shaft (701) is designed to receive the motion, directly or indirectly, from at least one between the first (501) and the second (502) eccentric gear.

Description

[0001] A REDUCTION GEAR UNIT

[0002] DESCRIPTION

[0003] Technical field

[0004] This invention relates to a reduction gear unit for the number of revolutions of a drive shaft, that is to say, the speed of rotation of the shaft of a motor, in order to be able to move and control the machining of corresponding apparatuses or tools to which the device is coupled.

[0005] Background art

[0006] The prior art is particularly rich in examples of various types of toothed gears, including gear wheels, toothed cylinders, toothed crowns and the like used for various functions. Toothed gears are important basic mechanical parts, widely used in almost all production machinery of all traditional industrial manufacturing sectors, in the aerospace sector, in rail transport, in building machines, in precision instruments and many others.

[0007] In this panorama, the use of reduction gear devices is very common for reducing the number of revolutions of a motor, for example electric, for various applications, such as the control of any movement apparatus or machining tool.

[0008] In particular, the reduction gear unit allows the torque and the speed of the electric motor to be transformed, in such a way as to satisfy certain drive requirements.

[0009] The reduction gear units generally comprise a series of gears, housed inside a casing, interposed between an input shaft (fast shaft), provided with a certain speed of rotation, and an output shaft (slow shaft) which will have a reduced speed of rotation.

[0010] The reduction gear units may be distinguished on the basis of the way in which they transmit the forces and, in general, comprise parallel shaft reduction gear units, angular reduction gear units, cycloidal reduction gear units and epicyclic reduction gear units.

[0011] In the reduction gear units with parallel and epicyclic axes, the input and output shaft are in the same direction and therefore the force is transmitted in a straight line. The parallel axes reduction gear units may have parallel or orthogonal shafts.

[0012] In the angular reduction gear units, on the other hand, the input and output shaft is perpendicular to each other and consequently the flow of force is imparted at right angles. The most common angular reduction gear units are conical torque reduction gear units and worm screw reduction gear units.

[0013] In the cycloidal reduction gear units two or more cycloid discs rotate in an eccentric movement with the cylindrical rollers inserted in the so-called inner lobe rings, at a distance defined by the division of the cycloid disc.

[0014] The epicyclic, or planetary, reduction gear units are usually mounted when a reduction ratio is required which is greater than that which can be obtained with a traditional reduction gear unit with parallel axes; the high power density guarantees compact and economical systems. They have the input shaft and the output shaft generally coaxial. Internally, there is a central gear corresponding to the input shaft (sun gear), an outer crown toothed internally and several gears (planet gears) positioned between the sun gear and the outer crown. The satellite gears are mounted on an element, the so-called planetary gear, which transmits the motion to the output shaft.

[0015] These reduction gear units adapt to specific requirements with good performance levels, but have limitations in the capacity of the reduction ratios, since the efficiency of the transmission is usually extremely low.

[0016] A reduction gear unit which is able to have a good efficiency is described in patent document JPH01158249 (A), wherein the drive force is transmitted from a motor to an eccentric shaft by means of a cycloidal planetary gear which rotates during the rolling corresponding to the rotation of the eccentric shaft. The output shaft is provided on the side of the planetary gear.

[0017] This reduction gear unit requires an Oldham coupling provided with an intermediate disc element through which the rotation of the planetary gear is transmitted to the output shaft.

[0018] The reduction gear unit allows the production of a quite compact gear, wherein the noise and the clearance are supressed with an increased reduction ratio.

[0019] However, its construction is not simple (and therefore not economic) and, above all, a reduction gear unit of this type, which operates thanks to the Oldham coupling, does not have a great versatility of use for different purposes.

[0020] Aims and summary of the invention

[0021] The aim of the invention is to overcome the above-mentioned drawbacks in known types of reduction gear units of the number of revolutions of a drive shaft which allows a high reduction ratio to be achieved.

[0022] In the context of the above-mentioned purpose, an aim of the invention is to provide a reduction gear unit for the number of revolutions of a drive shaft which is versatile and can easily be adapted to any machine.

[0023] Another aim of the invention is to allow a compact gear to be made, in such a way as to make a reduction gear unit which is small in size but with a high efficiency, in such a way that it can be applied in many technical sectors, for example in the field of bicycles or mopeds.

[0024] Yet another aim of the invention is to provide a reduction gear unit for the number of revolutions of a drive shaft which is simple to make and economically competitive.

[0025] Brief description of the invention

[0026] This purpose, as well as these and other aims, which are described in more detail below, are achieved by a reduction gear unit for the number of revolutions of a drive shaft, according to the invention, comprising the technical features described in one or more of the appended claims. The dependent claims correspond to possible different embodiments of the invention.

[0027] In particular, according to a first aspect, this invention relates to a reduction gear unit for the number of revolutions of a drive shaft which comprises, on a load-bearing frame which preferably has a first and a second half-shell, an input shaft, supported by the first half-shell, and an output shaft supported by the second half-shell.

[0028] The input shaft is designed to be mounted as one with a motor rotatable about an axis of rotation whilst the output shaft is designed to be associated with an actuator.

[0029] The toothed gear is connected to the input shaft by interposing at least one pair of eccentric gears for engaging with the input shaft which allow the transmission of the motion between the two shafts.

[0030] The connection is simultaneous, in the sense that both the eccentric gears act, directly or indirectly, on the toothed gear during operation of the reduction gear unit.

[0031] In practice, the reduction gear unit according to this invention comprises at least one pair of eccentric gears being mounted on the input shaft for transmitting the motion to the output shaft and designed to act simultaneously, directly or indirectly, on a toothed gear.

[0032] According to some variants, there may also be several pairs of eccentric gears alternatively or simultaneously designed to transmit the motion between the two shafts.

[0033] Another feature of the reduction gear unit is due to the fact that the output shaft is designed to receive the motion, directly or indirectly, from at least one between the first and the second eccentric gears.

[0034] More specifically, the eccentric gears include a first and a second eccentric gear positioned relative to each other in such a way that the respective centres of rotation are positioned symmetrically relative to the axis of rotation.

[0035] The Applicant has understood that in order to eliminate vibrations, which for reduction gear units with a high number of revolutions are considerable, the two eccentric gears must advantageously be mounted at 180° relative to each other, opposite the axis of rotation of the shaft, that is to say, they must be positioned in such a way that the straight line joining between the centre of rotation of the first eccentric gear and the centre of rotation of the second eccentric gear is substantially perpendicular to the axis of rotation.

[0036] Advantageously, this pair of eccentric gears simultaneously engages with the toothed gear.

[0037] In this case, on the toothed gear, there is preferably a shared track for the two eccentric gears. Alternatively, the eccentric gears rest on a common tubular element.

[0038] Moreover, this embodiment allows the designer to modify the function of the components for applying the reduction gear unit to the needs which arise each time, depending on the machine or the device on which it is installed.

[0039] With such a configuration, the Applicant is able to transmit very high speeds of rotation using reduced spaces. These compact reduction gear units are applied in a wide range of products and in a multitude of industrial sectors.

[0040] Preferably, the input shaft and the output shaft of the reduction gear unit are coaxial, with the output gear either male or female.

[0041] The eccentric gears are mounted by means of a pair of planes eccentric relative to the extension of the input shaft (and therefore also relative to the axis of rotation) which support the eccentric gears. These eccentric planes are integral with the input shaft and rotate with it eccentrically: a first and a second eccentric supporting plane, respectively, for the first and the second eccentric gear.

[0042] The two supporting planes preferably have a eccentricity which is symmetrical and opposite relative to the direction of extension of the shaft, that is, relative to the axis of rotation of the shaft, so as to form that configuration just described which allows the reduction gear unit to greatly limit, if not eliminate, the annoying vibrations.

[0043] The first eccentric plane is therefore interposed between the input shaft and the first eccentric gear and therefore allows the assembly, by means of suitable bearings, of the first eccentric gear on the input shaft. The second eccentric plane is, on the other hand, positioned downstream of the first plane relative to the direction of exchange of the forces, which coincides with the direction of transmission of the motion (with direction from the input shaft to the output shaft); in practice, the second plane, which is also integral with the input shaft like the first eccentric plane, allows in turn the assembly of the second eccentric gear, obviously by means of suitable bearings, on the input shaft.

[0044] According to some solutions, there is a supporting plate for the output shaft, preferably mounted on it or connected to the output shaft by appropriate rotational mechanisms and designed to be connected to the toothed gear, directly or indirectly by means of other auxiliary gears.

[0045] According to other variant embodiments, the plate is associated with at least one other toothed gear and the latter is engaged, directly or indirectly (that is, by means of intermediate gears), with the toothed gear.

[0046] According to yet other embodiments, the plate is designed to be connected to the first or to the second eccentric gear, normally the one further downstream relative to the direction of transfer of the motion, that is to say, the second eccentric gear which may be simultaneously engaged, on one side, with the toothed gear and, on the opposite side, with the plate or with at least one of the intermediate toothed gears, or, according to another embodiment, it may simultaneously engage, on one side, with at least one of the intermediate toothed gears and, on the opposite side, with the plate or with a further toothed gear.

[0047] Detailed description of the actuation of invention

[0048] Further features and advantages of the invention are more apparent in the detailed description below, with reference to a preferred, non-limiting embodiment of the reduction gear unit for the number of revolutions of a drive shaft, illustrated by way of example and without limiting the scope of the invention, with the aid of the accompanying drawings, in which:

[0049] Figure 1 is a perspective view of a first example of the reduction gear unit 101 ;

[0050] Figure 2 is an exploded view of a second example embodiment of the reduction gear unit 102;

[0051] Figure 3 is a cross section substantially normal relative to the axis of rotation of the drive shaft of the reduction gear unit 102;

[0052] Figure 4 is a perspective view of a further variant of the reduction gear unit 103.

[0053] The above-mentioned drawings show a preferred embodiment of a reduction gear unit of the number of revolutions of a drive shaft for transmitting the motion between a motor and an actuator, according to the invention, which is denoted in its entirety with the numerals 101 , 102 and 103 and which comprises, on a load-bearing frame which has a first 201 and a second 202 half-shell, an input shaft 301 connected with a toothed gear 401 by means of a first 501 and a second 502 eccentric gear and an output shaft 701 .

[0054] The input shaft 301 is supported by the first half-shell 201 , and is mounted as one with the drive shaft of the motor, so as to be in rotation about an axis of rotation X which coincides with the direction of extension of the drive shaft.

[0055] The output shaft 701 is associated with an actuator, supported by the second half-shell 202, and may be connected to one of the eccentric gears 501 and 502, or to the toothed gear 401 in some cases directly and in other cases indirectly.

[0056] The toothed gear 401 engages simultaneously with the eccentric gears 501 and 502 which, in turn have the purpose of transmitting the motion, directly or indirectly, to the output shaft 701 , thus forming numerous variants all falling within the inventive concept expressed in the set of claims attached.

[0057] The first 501 and the second eccentric gear 502 are positioned relative to each other in such a way that the respective centres of rotation 510 and 520 are positioned symmetrically relative to the axis of rotation X. In other words, the two eccentric gears 501 and 502 are mounted at 180° to each other, opposite relative to the axis of rotation X, that is, positioned in such a way that the straight line R joining between the centre of rotation 510 of the first eccentric gear 501 and the centre of rotation 520 of the second eccentric gear 502 is substantially perpendicular to the axis of rotation X (Figure 4).

[0058] For this reason, the centre of rotation 510 of the first eccentric gear 501 and the centre of rotation 520 of the second eccentric gear 502 define a straight line R substantially perpendicular to the axis of rotation X.

[0059] According to a first embodiment, illustrated in Figure 1 , during the transmission of the motion, the eccentric gears 501 and 502, which are gear wheels, simultaneously engage the toothed gear 401 .

[0060] More specifically, the reduction gear unit 101 in this case comprises a first eccentric wheel 501 , with external toothing, and an eccentric wheel 502 which has a portion with external toothing 502e and a portion with double toothing 502c, external and internal. These wheels 501 and 502 are mounted, thanks to bearings 801 and 802, respectively on a first 351 and a second 352 eccentric supporting plane on the input shaft 301 and act on the inner toothing of the gear wheel 401 .

[0061] The outer teeth of the first eccentric wheel 501 and of the portion 502e of the second eccentric wheel 502 engage during the rotation of the shaft 301 the inner teeth of the gear 401 , whilst the inner teeth of the portion 502c of the eccentric wheel 502 acts on an additional toothed gear 440, that is, an additional gear wheel 440, connected to the output shaft.

[0062] A reduction gear unit 101 of this type is of the reversible type, extremely compact and easy to make, by means of which it is possible to obtain reduction or multiplication ratios of from 1 :5 to 1 :800.

[0063] Figures 2 and 3 illustrate an alternative embodiment, wherein in the reduction gear unit 102 the motion is transmitted from the input shaft 301 to the output shaft 701 by a series of intermediate gears acting between the eccentric gears 501 and 502 (external toothed gear wheels mounted on the planes 351 and 352 by means of bearings 801 and 802) and the toothed gear 401 (internal toothed gear wheel).

[0064] More in detail, the input shaft 301 is mounted on a first half-shell 201 thanks to a pair of first bearings 803 and has the eccentric planes 351 and 352 on which, by means of bearings 801 and 802, the eccentric wheels 501 and 502 are mounted.

[0065] These engage, respectively, for a first upstream intermediate gear wheel 41 1 and a second upstream intermediate gear wheel 412, with double track, as well as for a first downstream intermediate gear wheel 421 and a second downstream intermediate gear wheel 421 .

[0066] The term “upstream” and “downstream” means relative to the direction of transmission of the motion of the reduction gear unit 102, that is to say, according to the flow of forces which is transmitted from the input shaft 301 to the output shaft 701 .

[0067] In this case, the intermediate gears 41 1 , 412, 421 and 422 are gear wheels which allow the action at distance between the gears 501 and 502 and the gear wheel 401 .

[0068] The latter is fixed to a plate 601 , which consequently rotates about the axis X together with the wheel 401 , associated with the output shaft 701 which, therefore, rotates coaxially relative to the input shaft 301 .

[0069] Moreover, the shaft 701 is supported on a second half-shell 201 by a second pair of bearings 807.

[0070] The two half-shells 201 and 202 rest on a base 220 and a cover 210, which covers the gear 401 , closes the structure of the reduction gear unit 102.

[0071] This reduction gear unit 102 also comprises a balancing gear 430 which allows balancing of the rolling forces during operation.

[0072] Again with reference to Figures 2 and 3, the gear 430 is a gear wheel with inner teeth which meshes with an additional outer gear 421 a of the second intermediate gear 421 . The latter, therefore, is a crown which has a double outer toothing, parallel, where both the gear 401 and the gear 430 act and an inner toothing for engaging with the first intermediate gear 411 .

[0073] Such a reduction gear unit 102 is of the reversible and radial multi-stage type, therefore, the ratios indicated in 101 multiply by the number of stages.

[0074] In addition, the output can be a double shaft.

[0075] Another embodiment of the reduction gear unit 103 according to the invention is illustrated in Figure 4.

[0076] In this case, the eccentric gears 501 and 502, both for engaging on the toothed gear 401 , are mounted on the eccentric planes 351 and 352, using bearings 801 and 802.

[0077] More specifically, the eccentric gears are gear wheels with external toothing, keyed on the planes 351 and 352, which engage together on the internal toothing of the gear wheel 401 , that is to say, on the toothed gear 401.

[0078] In this configuration, the output shaft 701 is associated with a plate 601 which, in turn, has a toothed protrusion 601 a. A further toothed track 502a acts on the protrusion 601 a defined on a tooth 502b protruding from the body of the second eccentric gear 502.

[0079] The reduction gear unit 103, like reduction gar unit 101 , is also of the reversible type, and is extremely compact and easy to make. In this case, it is possible to transmit similar speeds to the reduction gear unit 101 , with a reduction (or multiplication) ratio substantially equal to 1 :25.

[0080] Obviously, thanks to the intuition of the Applicant, other (and numerous) variant embodiments are possible, using, for example, epicyclic and cycloidal planetary gears which are also very complex.

[0081] From the above description it may be seen how the invention achieves the preset purpose and aims and in particular the fact that a reduction gear unit is made for the number of revolutions of a drive shaft, which makes it possible to have a very high reduction ratio.

[0082] In particular, the making of the double eccentric gear on the one hand offers compactness to the device and, on the other hand, gives stability. Another advantage of the invention is due to the fact that such a reduction gear unit is extremely versatile and can be easily modified to make it suitable for use on any machine.

[0083] Moreover, another advantage of the invention is due to the possibility of making extremely compact gears, that is to say, with small dimensions and low weights, but with high reduction coefficients, in such a way as to have an inexpensive but high efficiency reduction gear unit.

[0084] Lastly, the use of means which are easily available on the market and the use of common materials makes the device economically competitive. The invention can be modified and adapted in several ways without thereby departing from the scope of the inventive concept.

[0085] Moreover, all the details of the invention may be substituted by other technically equivalent elements.

[0086] In practice, the materials used, as well as the dimensions, may be of any type, depending on requirements, provided that they are consistent with their production purposes.

Claims

CLAIMS1) A reduction gear unit (101 , 102, 103) for the number of revolutions of a drive shaft for transmitting the motion between a motor and an actuator, comprising, on a load-bearing frame (201 , 202): an input shaft (301 ) designed to be mounted as one with the drive shaft of the motor, rotatable about an axis of rotation (X); an output shaft (701 ), designed to be associated with an actuator; at least one pair of eccentric gears (501 , 502) for engaging with the input shaft (301 ) for transmitting the motion to the output shaft (701 ), simultaneously designed to act, directly or indirectly, on a toothed gear (401 ): a first eccentric gear (501 ) and a second eccentric gear (502) positioned relative to each other in such a way that the respective centres of rotation (510, 520) are positioned symmetrically relative to the axis of rotation (X); the output shaft (701 ) being designed to receive the motion, directly or indirectly, from at least one between the first (501) and the second (502) eccentric gear.2) The reduction gear unit (101 , 102, 103) according to claim 1 , wherein the centre of rotation (510) of the first eccentric gear (501 ) and the centre of rotation (520) of the second eccentric gear (502) define a straight line (R) substantially perpendicular to the axis of rotation (X).3) The reduction gear unit (102) according to claim 1 or 2, wherein the pair of eccentric gears (501 , 502) engages the toothed gear (401 ) by means of mechanisms comprising at least one intermediate toothed gear (411 , 412, 421 , 422).4) The reduction gear unit (102) according to claim 3, wherein the first eccentric gear (501 ) is engaged simultaneously, on one side, with the toothed gear (401 ) and, on the opposite side, with at least one of theintermediate toothed gears (411 , 412, 421 , 422).5) The reduction gear unit (101 , 102, 103) according to any one of claims 1 to 4, wherein the input shaft (301 ) and the output shaft (302) are coaxial.6) The reduction gear unit (101 , 102, 103) according to any one of claims 1 to 5, comprising a first (351 ) and a second (352) eccentric plane respectively for supporting the first (501 ) and the second (502) eccentric gear; the first eccentric plane (351 ) being interposed between the input shaft (301 ) and the first eccentric gear (501 ) and the second eccentric plane (352) being positioned downstream of the first eccentric plane (351 ) relative to the direction of exchange of the forces.7) The reduction gear unit (101 , 102, 103) according to any one of claims 1 to 6, comprising a supporting plate (601 ) for the output shaft (701 ) designed to be connected, directly or indirectly, to the toothed gear (401 ).8) The reduction gear unit (101 , 102) according to claim 7, wherein the plate (601 ) is associated with at least one between the first (501 ) and the second (502) eccentric gear or with at least one other toothed gear; the other toothed gear engaging, directly or indirectly, with the toothed gear.9) The reduction gear unit (103) according to claim 7, wherein the plate (601 ) comprises a toothed track (601 a) for engaging with at least one between the first (501 ) and the second (502) eccentric gear.10) The reduction gear unit (102) according to claim 3 or 4 in combination with claim 7, wherein the second eccentric gear (502) is engaged simultaneously, on one side, with the toothed gear (401 ) and, on theopposite side, with the plate (601 ) or with at least one of the intermediate toothed gears (411 , 421 ).11 ) The reduction gear unit (102) according to claim 3 or 4 in combination with claim 7, wherein the second eccentric gear (502) is engaged simultaneously, on one side, with at least one of the intermediate toothed gears (412, 422), and, on the opposite side, with the plate (601 ) or with a further toothed gear (440).

Images