A reduction gear unit

Abstract

Described is a reduction gear unit (1) with circumferential gears which comprises a first flange (2) for engaging with a drive shaft (M), at the input to the reduction gear unit (1). The drive shaft (M) extends along an axis of symmetry (X) and is a rotatable support simultaneously for a first gear (11) and a second gear (12), respectively suitable for engaging a second flange (4) and an output shaft (U) connected to a container body (5) for the first gear (11) and the second gear (12).

Description

[0001] A REDUCTION GEAR UNIT

[0002] DESCRIPTION

[0003] Technical field

[0004] This invention relates to a reduction gear unit with circumferential gears.

[0005] Background Art

[0006] Cycloidal reduction gear units are known, that is to say, devices which reduce the speed of rotation of a drive shaft and increase the torque in a mechanical system. A cycloidal reduction gear unit uses a mechanism which involves a cycloidal wheel and an eccentric disc, providing a very high reduction ratio in a compact format.

[0007] It comprises an eccentric disc mounted on the drive shaft, a cycloidal wheel provided with teeth in the form of a cycloid, which interacts with the fixed rollers inside the housing of the reduction gear unit and an output shaft connected to the cycloidal wheel by rollers or pins, which transmits the increased torque to the output of the reduction gear unit.

[0008] The fixed rollers are situated inside the casing of the reduction gear unit, with which the teeth of the cycloidal wheel interact for transmitting the movement.

[0009] The drive shaft rotates the eccentric disc, which creates an orbital movement of the cycloidal wheel. This, interacting with the fixed rollers, generates a reduced rotary movement. This reduced movement, together with a high torque, is transferred to the output shaft by means of the rollers or pins connected to the cycloidal wheel.

[0010] The cycloidal reducers allow very high reduction ratios to be obtained in a compact format.

[0011] They are also known for their robustness and duration, with a high energy efficiency.

[0012] Moreover, the configuration of the reducer allows an excellent resistance to impacts and vibrations.

[0013] For this reason, these cycloidal reducers are used in a wide range of industrial applications, such as robotics, machine tools, transport and automation system, where high precision and reliability are required.

[0014] The cycloidal reducers, despite their numerous advantages, also have some drawbacks.

[0015] Firstly, the design and the construction of a cycloidal reduction gear unit are more complex than other types of reduction gear units, such as those with planetary gears or worm screws.

[0016] The complexity of the design and the high quality materials needed to ensure high performance often lead to higher production and maintenance costs.

[0017] The cycloidal reducers may be noisier than other types of reducers, especially at high speeds, due to the eccentric movement and the interaction of the cycloidal teeth with the fixed rollers.

[0018] The eccentric movement can generate vibrations, which may require further damping or insulation systems to prevent problems in sensitive applications.

[0019] Even if generally efficient, the efficiency of the cycloidal reducers can reduce under variable loads or under non-optimum conditions of use. For example, they may have greater internal friction than other types of reducers under certain loads.

[0020] In addition, adequate and regular lubrication is required in order to operate correctly. Insufficient lubrication can lead to premature wear and malfunctions.

[0021] For this reason, the maintenance can be more complex and costly due to the need for precision in making and assembling the parts.

[0022] Lastly, the cycloidal reduction gear unit is sensitive to assembly precision. Imprecise assembly may cause operating problems and reduce the working life of the reduction gear unit.

[0023] Epicyclic reducers are also widespread.

[0024] The epicyclic reduction gear units offer advantages in terms of efficiency, precision, fluidity of movement and maintenance compared with the cycloidal reduction gear units. However, the choice between a cycloidal gear unit and an epicyclic gear unit depends on the specific requirements of the application, including factors such as the reduction ratio required, the available space, the cost and the operating conditions.

[0025] In general, epicyclic reducers tend to have slightly greater efficiency than cycloidal reducers, especially at constant loads and high speeds, thanks to the uniform distribution of the forces between several gears.

[0026] In addition, they provide a smoother and less noisy movement than cycloidal reducers because the components are in continuous contact and well balanced.

[0027] They are also extremely precise, making them ideal for applications which require precise control of the movement, such as robotics and precision machine tools.

[0028] At the same time, they tend to have a reduced clearance (“backslash”) compared to cycloidal reducers, thereby further improving the precision.

[0029] The epicyclic reduction gear units can be configured in various ways to obtain different reduction combinations, which makes them extremely versatile for different applications. However, while they have a compact design, they can be designed to provide high torque, making them suitable for applications where space is limited.

[0030] The distribution of the load between several gears reduces wear and extends the working life of the reduction gear unit. Moreover, they require less maintenance than cycloidal reduction gear units, thanks to their robust construction and lower sensitivity to assembly precision.

[0031] However, the epicyclic reduction gears cannot obtain extremely high reduction ratios like the cycloidal reduction gears in the same space.

[0032] Among other things, they can be more expensive to produce, especially if very tight tolerances and high-quality materials are required.

[0033] Summary of the Invention

[0034] The aim of the invention is to overcome the above-mentioned drawbacks of prior art types of reduction gear units with circumferential gears which allows a high reduction in the speed of rotation together with a very high torque transmission.

[0035] In the context of the above-mentioned purpose, an aim of the invention is to provide a reduction gear unit with circumferential gears, which is compact and highly efficient, reducing problems of size and transport.

[0036] Another aim of the invention is to allow the production of reducers with circumferential gears which are easier to make, and therefore economically competitive.

[0037] This purpose, as well as these and other aims, which are described in more detail below, are achieved by a reduction gear unit with circumferential gears, 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.

[0038] More specifically, according to a first aspect, this invention relates to a reduction gear unit with circumferential gears which comprises only four gears which are able to produce extremely high reductions in speed with ratios of even 1 :9000 between the drive shaft and the output shaft.

[0039] The reduction gear unit according to this invention comprises the use of: a first flange for engaging with a drive shaft, at the input to the reduction gear unit, which extends along an axis of symmetry, a first gear supported by the drive shaft; a second gear, again supported by the drive shaft, which has the same speed of rotation as the first gear and acts on the output shaft; a second flange which is engaged by the first gear, preferably by an inner toothing made on said second flange;

[0040] A container body connected to the output shaft which houses the first and the second gear closes the reduction gear unit.

[0041] According to this embodiment, the term “inner” means that element, or part of it, which, on a cross-section normal relative to the axis of symmetry of the shaft, has from this a smaller distance than an “outer” element or part of it.

[0042] The Applicant has therefore made a reduction gear unit which is extremely simple (only four gears) and compact (half the size and half the weight relative to those on the market), but with very high potential in terms of performance and production flexibility.

[0043] Advantageously, therefore, the drive shaft is a simultaneous rotatable support for the first gear and the second gear, which are, respectively, suitable for engaging the second flange and the output shaft.

[0044] In order to make the reduction gear unit compact, the second flange is interposed between the first flange and the container body.

[0045] Preferably, the first and the second gear are made as one piece.

[0046] According to a first configuration, the container body is fixed relative to the output shaft and the second flange is fixed; in practice, the output shaft is in rotation about its own axis.

[0047] Conversely, if the output shaft is fixed, the container body and the second flange are in rotation about the axis of symmetry.

[0048] The Applicant has therefore perceived that, advantageously, the speed transmitted at the output by means of the above-mentioned gears makes the reduction gear unit compact and extremely efficient, as well as extremely versatile since the output shaft can rotate or remain fixed, rotating the container body.

[0049] Advantageously, in order to reduce the radial force, preventing this from distributing in a torsional fashion around the drive shaft, use is made of opposite contact discs. In practice, a hub, mounted on the drive shaft, supports the first and the second gear. The hub has a first and a second eccentric wheel which have the respective central axes anti-symmetrical and equidistant relative to the axis of symmetry.

[0050] The first eccentric wheel engages with a first contact disc which, in turn, engages with the second flange. The first contact disc is idle about the axis of symmetry of the drive shaft between the second flange and the first eccentric wheel.

[0051] The second eccentric wheel engages with the first gear and the second gear. A second contact disc engages with a third eccentric wheel associated with the hub; it is idle about the axis of symmetry of the drive shaft between a portion of the output shaft and the third eccentric wheel.

[0052] The second flange is suitable for being engaged by the first contact disc and is fixed, on one side, to the first flange and, on the other side, to the container body, rotatably associated with the output shaft.

[0053] The latter is suitable for being engaged simultaneously by the second gear and by a second contact disc, which is also free to rotate idly about the axis of symmetry of the drive shaft between a portion of the output shaft and a third eccentric wheel, mounted on the hub, on which the second contact disc engages.

[0054] Therefore, the two contact discs do not have a resistive load and rotate at the same axial speed, opposite each other relative to the gears.

[0055] Advantageously, the first flange, the second flange and the container body have an inner containment compartment for the hub, on which are made the first and the second eccentric wheel, the first and the second gear, the first and the second contact disc, the third eccentric wheel and a portion of the output shaft, thus reducing the dimensions and the weight to a considerable manner.

[0056] In order to allow the positioning of the hub on the drive shaft during the assembly step, the third eccentric wheel is preferably suitable for being removably associated with the hub.

[0057] Advantageously, the first, the second and the third eccentric wheels all have the same radial speed as the drive shaft, since they are on the same axis.

[0058] In order to compensate for the radial forces, avoiding radial deviations, both the first and the second contact disc are advantageously mounted in an opposite manner, that is to say, at 180°, relative to the first and the third eccentric wheels, in a corresponding manner.

[0059] In this regard, in fact, the force is supported above all by the gearing which supports the first and the second gear.

[0060] Advantageously, the drive shaft and the hub are mounted eccentrically, at a distance equal to half the difference between the primitive diameters of the inner toothing of the second flange and of the first eccentric wheel.

[0061] In practice, in order to find the value of the eccentric distance, that is to say, the distance between the axis of symmetry of the drive shaft and the axis on which the eccentric wheels rest, it will be necessary to make the difference between the primitive diameter of the inner toothing of the second flange and the primitive diameter of the first gear, and then divide in half.

[0062] Advantageously, the transmission ratio between the drive shaft and the output shaft is equal to the product of the primitive diameters of the first gear and of the inner toothed portion of the output shaft, divided by twice the product between the eccentric distance between the drive shaft and the hub (just found), and the difference between the primitive diameters relative to the inner toothing of the second flange and the third eccentric wheel.

[0063] In other words, the transmission ratio will be the ratio between the product of the primitive diameters between the first gear and the second gear (numerator) relative to twice the product between the above-mentioned eccentric distance and the difference between the primitive diameter of the inner toothing of the second flange and the primitive diameter of the internally toothed portion of the output shaft (denominator).

[0064] In this way, the Applicant does not need to determine the module a priori, but, conversely, having determined the transmission ratio, the suitable module can consequently be calculated.

[0065] Description of the drawings

[0066] 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 with circumferential gears, illustrated by way of example and without limiting the scope of the invention, with the aid of the accompanying drawings, in which:

[0067] Figure 1 shows a plan view of an example embodiment of the reduction gear unit 1 according to the invention, assembled;

[0068] Figure 2 shows the cross-section ll-ll of the reduction gear unit 1 of Figure 1 ;

[0069] Figure 3 shows the cross-section Ill-Ill of the reduction gear unit 1 of Figure 1 ;

[0070] Figure 4 shows the cross-section IV-IV of the reduction gear unit 1 of Figure 1 ;

[0071] Figure 5 shows the cross-section V-V of the reduction gear unit 1 of Figure 1 ;

[0072] Figure 6 shows the cross-section VI-VI of the reduction gear unit 1 of Figure 1 ;

[0073] Figure 7 shows an exploded perspective view of the reduction gear unit 1 ;

[0074] Figure 8 shows a perspective view of the output shaft U which mounts, as a first variant, a cycloidal disc C;

[0075] Figure 9 shows a perspective view of the output shaft U which mounts, as a second variant, a Holden H joint;

[0076] Figures 10A and 10B schematically illustrate the reduction gear unit 1 in a perspective view and in an elevation view, respectively, highlighting the fixed point O of rotation of the output shaft U and its eccentricity E relative to the axis of rotation of the gears 11 and 12.

[0077] Detailed description of the invention

[0078] The above-mentioned drawings show a preferred embodiment of a reduction gear unit with circumferential gears, according to the invention, which is denoted in its entirety with the reference numeral 1 and which comprises a first flange 2, which engages with a drive shaft M at the input to the reduction gear unit 1 , and a first flange, a container body 5, rotatably associated with an output shaft U, and a second flange 4 interposed between the first flange 2 and the container body 5.

[0079] The drive shaft M extends along a relative axis of symmetry X and rotatably supports a hub 3 thanks to bearings 30, the latter being mounted eccentrically relative to the drive shaft M for a distance E. The hub 3 is shaped in such a way as to form a first eccentric wheel 31 and a second eccentric wheel 32, in practice made by means of projections and recesses formed on the hub 3. The two eccentric wheels 31 and 32 have the respective central axes equidistant from each other and anti-symmetrical relative to the axis of symmetry X.

[0080] The first eccentric wheel 31 engages with a first contact disc 21 , mounted in an idle fashion about the axis of symmetry X of the drive shaft M between a fixed gear, which is defined on an internal toothing 41 of the second flange 4, and the first eccentric wheel 31 .

[0081] The second eccentric wheel 32 meshes with a first gear 11 and a second gear 12, made as one piece, which respectively engage the inner toothing 41 and the output shaft U.

[0082] There is a third eccentric wheel 33, associated with the hub 3, which engages a second contact disc 22 which is idle about the axis of symmetry X of the drive shaft M between a portion of the output shaft U and the third eccentric wheel 33.

[0083] If the first and second eccentric wheels 31 and 32 are shaped on the hub 33, the third eccentric wheel 33 is associated in a removable fashion with the hub 3 to allow, during assembly, the positioning of the hub 3 on the drive shaft M, which is impossible otherwise.

[0084] However, the three eccentric wheels 31 , 32 and 33 are kinematically integral with the drive shaft M and therefore have its same radial speed.

[0085] The first contact disc 21 is mounted in opposite manner, that is to say, at 180°, relative to the first eccentric wheel 31 ; similarly, the second contact disc 22 is also opposite the third eccentric wheel 33.

[0086] The output shaft U may have an internally toothed portion 51 for engaging with the second gear 12 (Figures 1 - 7).

[0087] As shown in Figure 4, the toothed portion 51 engages the toothing of the third eccentric wheel 33 simultaneously in at least two points R1 and P2, where there is the maximum pressure. For this reason, the head of the male tooth of the third eccentric wheel 33 is in contact with the bottom of the corresponding tooth of the internally toothed portion 51 (P1) and, simultaneously, the bottom of the foot of the male tooth of the third opposite eccentric wheel 33 works on the head of the female tooth of the internally toothed portion 51 (P2).

[0088] Similarly, as shown in Figure 5, it occurs due to the contact between the inner toothing 41 of the second flange 4 and the toothing of the first gear 11 , which occurs simultaneously in at least two points P1 ’ and P2’ of maximum pressure, that is to say, at the contact between the head of the male tooth of the first gear 11 and the bottom of the corresponding toothing 41 (P1 ’) and, simultaneously, at the point of contact between the bottom of the foot of the male tooth of the first opposite gear 11 , with the head of the female tooth of the inner toothing 41 (P2’).

[0089] According to this embodiment, the output shaft U has a chamfer 53 without teeth in its outer surface, intended to come into contact with the inner face of the container body 5, which does not transmit torque.

[0090] Alternatively, the output shaft U engages with the second gear by means of fixed cams 151 of a cycloidal disc C (Figure 8), or by means of pins 251 of a Holden H joint (Figure 9).

[0091] As mentioned, the drive shaft M and the hub 3 are mounted eccentrically, at a distance E which is equal to half the difference between the primitive diameters DP41 and DP11 respectively referred to the inner toothing 41 of the second flange 4 and to the toothing of the first gear (Figure 10A).

[0092] The following formula is therefore applied to find the value of E:

[0093] E = (DP41-DP11) / 2

[0094] With reference to Figure 10B, the transmission ratio I between the drive shaft M and the output shaft U is, on the other hand, equal to the product of the primitive diameters DP11 (of the first gear 11 ) and DP51 (of the internally toothed portion 51 of the output shaft 5) on twice the product between the above-mentioned distance E with the difference between the primitive diameters DP41 (of the inner toothing 41 of the second flange 4) and DP51 (of the internally toothed portion 51 ): I = (DP11xDP51) / 2-E-(DP41-DP51)

[0095] For example, given:

[0096] DP11 = 124mm, Z11 = 31

[0097] DP41 = 140mm, Z41 = 35

[0098] DP12 = 184mm, Z12 = 46

[0099] DP51 = 200mm, Z51 = 50 with Z the relative number of teeth of each gear in question, then:

[0100] E = 8mm

[0101] I = 25.83

[0102] From the above description it may be seen how the invention achieves the preset purpose and aims and in particular it should be noted that a reduction gear unit is made with circumferential gears, which allows a significant reduction in the speed of rotation and a much higher transmission than the common gears.

[0103] Thanks to this reduction gear unit, in effect, multiple reduction gear units can be executed in a single container body.

[0104] Moreover, the reduction gear unit is extremely compact and considerably lighter than similar reduction gear units which have comparable performance levels.

[0105] Another advantage of this reduction gear unit is due to its high efficiency combined with the simplicity and flexibility of use.

[0106] Lastly, the use of means which are easily available on the market and the use of common materials makes the device economically competitive.

[0107] The invention can be modified and adapted in several ways without thereby departing from the scope of the inventive concept.

[0108] Moreover, all the details of the invention may be substituted by other technically equivalent elements.

[0109] 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 (1 ) with circumferential gears comprising: a first flange (2) for engaging with a drive shaft (M), at the input to the reduction gear unit (1 ) and extending along an axis of symmetry (X); the drive shaft (M) being a rotatable support simultaneously for a first gear (11 ) and a second gear (12), respectively suitable for engaging a second flange (4) and an output shaft (U) connected to a container body (5) for the first gear (11 ) and the second gear (12).2) The reduction gear unit (1 ) according to claim 1 , wherein the second flange (4) is interposed between the first flange (2) and the container body (5).3) The reduction gear unit (1 ) according to claim 2, wherein the first gear (11 ) and the second gear (12) are made as one piece.4) The reduction gear unit (1 ) according to any one of claims 1 to 3, wherein the container body (5) and the second flange (4) are fixed relative to the output shaft (U); the output shaft (U) being in rotation about its own axis.5) The reduction gear unit (1 ) according to any one of claims 1 to 3, wherein the container body (5) is rotatably supported by the fixed output shaft (U), with the second flange (4) rotatable about the axis of symmetry (X).6) The reduction gear unit (1 ) according to claim 4 or 5, comprising a hub (3) mounted on the drive shaft (M) and having a first eccentric wheel (31 ) and a second eccentric wheel (32) with respective central axes antisymmetrical and equidistant relative to said axis of symmetry (X); the first eccentric wheel (31 ) engaging with a first contact disc (21 ),engaging with the second flange (4), idle about the axis of symmetry (X) of the drive shaft (M) between an inner toothing (41 ) of the second flange (4) and the first eccentric wheel (31 ); the second eccentric wheel (32) engaging with the first gear (11 ) and the second gear (12); the output shaft (U) being suitable for being engaged also by a second contact disc (22), in turn for engaging with a third eccentric wheel (33) associated with the hub (3) and idle about the axis of symmetry (X) of the drive shaft (M) between a portion of the output shaft (U) and said third eccentric wheel (33).7) The reduction gear unit (1 ) according to claim 5 or 6, wherein the first eccentric wheel (31 ) and the second eccentric wheel (32) are defined by projections and recesses of the hub (3).8) The reduction gear unit (1 ) according to any one of claims 1 to 7, wherein the first flange (2), the second flange (4) and the container body (5) have an inner containment compartment for the hub (3), the first gear (11 ), the second gear (12), the first contact disc (21 ), the second contact disc (22), the third eccentric wheel (33) and a portion of the output shaft (U).9) The reduction gear unit (1 ) according to claim 8, wherein the third eccentric wheel (33) is removably associated with the hub (3) to allow, during assembly, the positioning of the hub (3) on the drive shaft (M).10) The reduction gear unit (1 ) according to claim 8 or 9, wherein the first eccentric wheel (31 ), the second eccentric wheel (32) and the third eccentric wheel (33) have the same radial speed as the drive shaft (M).11 ) The reduction gear unit (1 ) according to any one of claims 6 to 10,wherein the first contact disc (21 ) and the second contact disc (22) are mounted in opposite directions relative to the first eccentric wheel (31 ) and to the third eccentric wheel (33).12) The reduction gear unit (1 ) according to any one of claims 6 to 11 , wherein the drive shaft (M) and the hub (3) are mounted eccentrically, at a distance (E).13) The reduction gear unit (1 ) according to claim 12, wherein said distance (E) is equal to half the difference between the primitive diameters (DP41 , DP51 ) of the inner toothing (41 ) of the second flange (4) and the toothed portion of the container body (5).14) The reduction gear unit (1 ) according to claim 9, wherein the transmission ratio (I) between the drive shaft (M) and the output shaft (U) is equal to the product of the primitive diameters (DP11 , DP51 ) of the first gear (11 ) and the toothed portion of the container body (5) on twice the product between the distance (E) and the difference between the primitive diameters (DP41 , DP51 ) relative to the inner toothing (41 ) of the second flange (4) and the toothed portion of the container body (5).

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