Gear having at least two rows of teeth offset axially and in the direction of rotation

Abstract

The invention relates to a gear (1) having at least two rows of circumferential teeth offset axially and in the direction of rotation. For the purpose of a precise and cost-effective production, according to the invention, the gear (1) has gear wheels (5, 6) which are structurally identical to one another. Adjusting elements (7, 8) for setting the offset of the gear wheels (5, 6) in the direction of rotation, and asymmetric teeth for transmitting particularly high loads are described in embodiments.

Description

[0001] Gear with at least two rows of teeth offset axially and in the direction of rotation

[0002] The invention relates to a gear with at least two axially and rotationally offset rows of circumferential teeth, wherein the gear is provided with toothed discs of identical construction to one another, according to the preamble of claim 1.

[0003] Gears with multiple rows of teeth offset in the direction of rotation (along the circumference) have the advantage over single-row gears that more pairs of teeth can be engaged simultaneously, thus improving both the transmissible power and the smooth running. For example, a "molded staggered tooth gear" from the Mesta Machine Company dating from 1913, with a diameter of well over 10 meters, can be found online at: https: / / www.google.com / search?q=Molded+staggered+tooth+gear&rlz=lClCHBD_de AT853AT853&tbm=isch&source=iu&ictx=l&fir=150DW3gNXBzxlM%253A%252C 0bi4EEA0twyfkM%252C_&vet= 1 &usg=AI4_- kTZ3AhqhozE_v2ZNCHbG6ZWMih2pw&sa=X&ved=2ahUKEwjIxpygpIXnAhU9xM

[0004] QBHWGlBvwQ9QEwAHoECAkQBQ#imgdii=MsJTrGQf2XvdCM:&imgrc=cQY7-

[0005] 0BGKTQijM:&vet=l

[0006] Such gears are also used in various gear pumps or gear motors to make the flow rate or drive power as uniform as possible, as specified in EP 0004 119 A2.

[0007] In general, it should be noted that the most important type of gear in mechanical engineering is the involute gear. It is considered a robust, optimal compromise when it comes to minimizing sliding friction between the meshing teeth, ensuring tooth root and flank load-carrying capacity, transmitting torque evenly, and withstanding the load changes that occur particularly in vehicle manufacturing. Crucial to its diverse applications is also the cost-effective and precise manufacturing method using roll milling. To increase the transmissible torque without compromising smooth running, the aim is to involve as many tooth pairs as possible in torque transmission simultaneously. However, with the typical pressure angles (17.5° to 20°), a profile overlap of 2 or more is practically impossible to achieve with the involute gear, which is advantageous in many respects.Under high torque loads, the impact tooth engagement point above the pitch point in spur involute gearing becomes noticeable through increased noise and abrasion. Therefore, helical gearing is generally used for high loads. However, this often necessitates more complex shaft bearings due to the resulting axial thrust, causes more friction, and is significantly more expensive to manufacture overall.

[0008] Therefore, there is a need for gears or a generic gear that can be manufactured with simple, identical parts, enables a high profile overlap even without helical gearing, ensures low-friction and low-noise tooth engagement under high loads, and can maintain optimal backlash better than is the case with previous gearing, including helical gearing.

[0009] The purpose and objective of the invention is to provide such a gear.

[0010] The objective is achieved with the features specified in the characterizing part of claim 1; in other words: Several toothed discs, which are mounted precisely on a shaft so as to be axially and rotationally movable and which preferably have positioning elements on their facing side surfaces that can lead to positive locking, are attached to a sleeve by means of a tensile element(s) which is positively connected to this shaft, wherein the toothed discs, when the tensile force is applied, position themselves axially and rotationally relative to each other, as well as on the sleeve, in such a way that the desired offset in the direction of rotation is achieved, and the backlash can be finely adjusted with respect to a toothed complementary part.

[0011] The use of individual toothed discs significantly simplifies and reduces manufacturing costs. Because the gear module is distributed across multiple toothed discs in multi-row gears, larger tooth thicknesses and gaps can be used, and the engagement point of the teeth for both directions of rotation of the respective loaded tooth flank pairs can thus be positioned near the ideal pitch point. This results in a smooth and quiet engagement start that surpasses the smoothness of conventional gearing. Furthermore, with adjacent toothed discs, an adjustable gap can be provided between the tooth flanks of the Hirth gears involved, allowing for fine-tuning of the backlash of the gear's circumferential teeth.

[0012] Straight-cut gears offer less friction and wear, and also allow for higher load-bearing capacities, compared to gears based on helical gears. Furthermore, due to their construction from identical toothed discs, the gears according to the invention can be manufactured cost-effectively using casting and gear hobbing processes, or any other manufacturing process for mass production according to the current state of the art.

[0013] Because of the pitch associated with the Hirth gear (10 mm axial travel can compensate for play of between 0.5 and 2 mm, depending on the pitch), the Hirth gear can also be manufactured with sufficient precision for this purpose using the casting process without necessarily requiring subsequent machining.

[0014] The term "toothed disc" as used in the description and claims of the invention encompasses all functionally identical components, whether one-piece or assembled, that are provided with teeth. This includes, for example, components that bear teeth in sections, annular tooth carriers, and toothed discs with an infinite radius (= racks). A toothed disc combination consisting of two toothed discs for the two directions of rotation is hereinafter referred to as a "double toothed disc".

[0015] Furthermore, the term "Hirth gear" is consistently used in the description and claims; however, in the basic concept of the invention, any positive-locking element can be used that can be attached to the side surfaces of the toothed discs 3 with sufficient precision and mechanical strength to create the desired offset between adjacent toothed discs. All such positive-locking elements fall under the term "Hirth gear" in the description and claims.

[0016] The invention is not limited to the illustrated and described embodiments, but can be modified in various ways. For example, the Hirth gears in meshing packages can be made identical for both gear sets, provided this is possible given the tolerances and load, which reduces manufacturing costs and simplifies inventory management. If different load peaks reliably occur in different directions, the thickness of the gear sets can be adjusted accordingly, or a conventional gear pair can be combined with the inventive package for the "heavy" direction for the "light" direction.

[0017] In general, the self-positioning properties of the toothed discs according to the invention can be used not only for the novel, asymmetrical tooth geometries described in more detail below, but also for conventional, symmetrical involute gearing. Furthermore, the described toothed discs, which are movable on the shaft and attached to a sleeve, can also be used in the manner of the invention without self-positioning lateral features to easily mount toothed discs with mass-produced tolerances with optimal clearance: For this purpose, for example, each individual toothed disc can be mounted onto the designated shaft during assembly, then pre-assembled "with a stop" against the tooth flanks of the complementary gearing, and subsequently connected to the sleeve by means of appropriate screws, bolts, etc., that penetrate all toothed discs.In principle, all industrial processes (gluing, welding, honing, etc.) can be used for fastening the toothed discs to each other and to the sleeve in the position according to the invention.

[0018] Finally, it should be noted that the combination of toothed discs on one and the same shaft, which add up to toothed combinations with different overall modules, according to the invention, can also be used to reduce the torsional vibrations excited by gears.

[0019] The invention is described in detail with reference to an exemplary embodiment and the following figures, which show: Fig. 1 a gear according to the invention with a complementary gear, and a section through two double toothed discs, Fig. 2 graphics on the genesis of the shock-free involute spur gear and its implementation with a double toothed disc, and Fig. 3 a gear according to the invention, meshing with a mating gear, in a top view and the function of the backlash regulation.

[0020] Reference symbol list:

[0021] 1 gear 20 tooth bodies “output”

[0022] 2 Complementary gear 21 Head-tooth flank

[0023] 3 Wave 22 Pitch point

[0024] 4 Cuff 23 Foot-tooth flank

[0025] 5 Toothed disc 24 Line of engagement point

[0026] 6 Toothed disc 25 End of engagement line

[0027] 7 Hirth gear 26 toothed disc, drive under load

[0028] 8 Hirth toothing 27 Toothed disc, rotating

[0029] 9 Double toothed disc 2 (section) 28 Double toothed disc output

[0030] 10 Double toothed disc 1 (section) 29 Toothed disc output under load

[0031] 11 Tooth head area (bar) 30 Double toothed disc drive

[0032] 12 Size of the tooth gap 31 Gear firmly toothed

[0033] 13 Size of the tooth gap 32 Gear with backlash adjustment

[0034] 14 Size of the tooth gap 33 Interlocking detail 1 / 32

[0035] 15 Counter-cuff with thread 34 Toothing to detail 2 / 32

[0036] 16 Spring element 35 Toothing to detail 1 / 31

[0037] 17 Involute tooth profile “foot” 36 Toothing to detail 2 / 31

[0038] 18 Involute tooth profile “head” 37 Hirth toothing 31

[0039] 19 Tooth body “drive” 38 Hirth gear 32 Fig. 1

[0040] Shown is a gear 1 according to the invention, meshing with a second gear 2 also according to the invention, both attached to their shafts 3 with so-called “sleeves” 4, as well as a section through four so-called “toothed discs” 5, 6, along a plane lying in front of the axes 3 intersecting the Hirth teeth 7, 8, graphically indicated by line A.

[0041] The sleeve 4 is fixedly mounted on the shaft 3, optionally forming it as a single unit. In principle, any number of double toothed discs 9, 10 (three per gear 1, 2 in the exemplary illustration shown here) are freely movable on the shaft 3 and arranged axially one behind the other. The toothed discs 5, 6 have Hirth teeth 7, 8 on both flanks, as does the sleeve 4 on its side facing the toothed discs 5, 6. The toothed discs 5, 6 have circumferential teeth, which, to distinguish them from those of the Hirth teeth, are called "circumferential teeth".The Hirth toothing is attached to the toothed discs in such a way that, after appropriate pre-positioning according to the invention and subsequent axial contraction of the stacked toothed discs until positive engagement, it shifts the circumferential teeth of all toothed discs in the direction of rotation by that part of the gear module required to achieve a uniform distribution of all circumferential teeth and thus also equally sized tooth gaps between all successively engaging circumferential teeth. In the embodiment shown in Fig. 1, with three double toothed discs 9, 10 per gear shown, the required partial module offset 12, 13, 14 is one-third of the circumferential tooth pitch. To illustrate the offset, four tooth tip regions of the double toothed discs 9, 10 are graphically represented as bars in the three-dimensional view.

[0042] 11 is highlighted, and the three equal distances 12, 13, 14 are shown with adjoining dashed lines.

[0043] According to the invention, the tightening of the toothed discs 5, 6 movable on the shafts 3 can be carried out with one or more tensioning elements, e.g. with a counter-sleeve 15 which can be screwed continuously onto the shaft 3 from the side opposite the sleeve 4, and can be carried out in such a way that all toothed discs are connected so tightly to the sleeve 4 that the torque to be transmitted by the circumferential teeth is completely introduced into the shaft.

[0044] To regulate the backlash during the meshing of the circumferential gears shown in Fig. 1, a spring element (or a corresponding actuator controlled by sensors, or a hydraulic system) 16 can be provided and act on the gear discs with a degressive force in the axial direction over a practical spring travel of 5 mm to a maximum of 10 mm. As shown in Fig. 3, this axially acting force can then be translated into a rotationally acting torque for regulating the backlash of the circumferential gears by means of an additional positioning of the Hirth gears offset by a gap.

[0045] The toothed discs of gear 1, which regulate the backlash, are dimensionally slightly wider than the toothed discs of the fixed gear 2 due to the axial spring travel they must accommodate. However, this widening can be omitted if the complementary gear has a mirror-symmetrical design like gear 1, i.e., is also equipped with a spring element, or if a simpler axial guidance mechanism (operating without adjustment in the direction of rotation) is installed in the complementary meshing gear 2.

[0046] Fig. 2 illustrates the kinematics of a shock-free tooth engagement for spur involute gears, as achievable with axially and rotationally offset gears. Starting from the conventional tooth flank geometry of spur involute gears 17, 18, including and beginning with the pitch point 22, only those tooth flank sections 21, 23 are supported by the tooth bodies 19, 20 (hatched) according to the invention which are subjected to torque while maintaining contact during and after passing through the pitch point 22. Starting with the pitch point 22 as the engagement point, the tooth flanks thus transmit moments counterclockwise along position 24 until they disengage from each other again at position 25.The portion of the involute gearing located before the pitch point can be omitted because, simultaneously, further, offset tooth flanks rotate on the same shaft, ensuring permanent contact between the tooth flanks: These tooth flanks are indicated by dashed lines in the area of ​​points 22, 24, and 25. For the counterclockwise rotation direction shown in the same diagram, a profile overlap factor of at least two is achieved kinematically with three toothed discs.

[0047] Conveniently, the amount of the radiant between the tooth flanks of all circumferential teeth that engage successively in one direction of rotation is identical.

[0048] The simultaneous, and in principle always reliable, contact with the tooth flanks for thrust reversal, which is indispensable in practice, can be achieved, as illustrated, by the appropriately combined (but generally not one-piece) double toothed discs 28 and 30. When the toothed disc 30 rotates counterclockwise as the drive wheel, torque is transmitted to the double toothed disc 28 with gentle tooth engagement from the point of contact 22 onwards. The toothed disc 26 and the meshing toothed disc 29 of the double toothed disc bear the load, while the toothed disc 27 rotates freely in contact with the double toothed disc 30. The load distribution changes analogously during thrust reversal. Therefore, despite the tooth flank movement occurring in one of the two directions of rotation, the toothed discs rotating freely produce neither increased abrasion nor noise.Other combinations of directions of rotation than those provided for with the double toothed discs are possible according to the invention, provided that the required distribution of forces and moments does not preclude this.

[0049] The increased installation space required is offset by significant advantages in terms of friction, cooling, and smooth running. Therefore, the comparison should not be made to other spur gears, but rather to the similarly wide, helical involute gears. Assuming an approximately equal required contact area between the tooth flanks, as with a helical gear of the same load-bearing capacity, the toothed discs according to the invention can be kept relatively small and narrow. This is particularly true since the elimination of butt tooth engagement, the gaps remaining between the circumferential tooth rows, and the use of high-viscosity lubricants (in conjunction with backlash control) allow for very good cooling of the thermally stressed tooth flanks.Finally, due to the unusually high profile overlap and the additional tooth flank adjustment, the occurrence of destructive torsional vibrations is also significantly reduced - another advantage for a comparatively lightweight and therefore compact design.

[0050] Fig. 3 illustrates the backlash regulation between the tooth flanks of the circumferential teeth of meshing gears according to the invention. A top view shows a gear with fixed toothed discs 31, and a gear 32 with a slightly different composition for backlash regulation, both gears meshing in the area of ​​the circumferential teeth 33, 34, 35, 36. The fixed-tooth gear 31 has toothed discs with the circumferential teeth according to the invention with asymmetrical teeth, as well as Hirth teeth 37 attached to both sides of the toothed discs, which are also shown in enlarged detail and are positively connected to one another.

[0051] The gear 31 has toothed discs in which the Hirth teeth are offset circumferentially by an additional gap, so that, for example, the tooth flanks 33 and 34 already bear on the tooth flanks of the gear teeth 35 and 36 before the positive engagement of the Hirth teeth 38 is fully achieved. In this configuration, one flank of each Hirth tooth bears on the mating tooth, while a gap remains open on the other side of the mating tooth. The axially acting force 39 is, in this configuration, transformed by the pitch of the Hirth teeth into the rotationally acting forces 40 and 41. These should, in principle, close the remaining gap.

[0052] The gaps are caused - but are prevented from doing so by the tooth flanks of the turnover toothing 33, 34, which already rest on the turnover tooth flanks 35, 36.

[0053] The pitch of the Hirth teeth and the preferably degressive axial force 39 can be designed such that, on the one hand: the moment with which the circumferential teeth are preloaded tends practically towards zero, but nevertheless ensures a sufficient tracking effect for permanent tooth flank contact during shear reversal, and on the other hand: any moment that acts back from the circumferential teeth onto the toothed discs and exceeds a dangerous maximum value can lead to deflection of the toothed discs, and can thus be cushioned and damped - a task which, in the design example, is taken over by spring element 16 of effectively layered disc springs.

[0054] To reduce or partially smooth the torsional vibrations excited by gear teeth, a combination of toothed discs 5, 6 with different overall modules can also be used.

[0055] The invention is not limited to the illustrated and described embodiment, but can be modified in various ways. For example, other basic tooth shapes can be used to form the teeth according to the invention; if only small torques need to be reliably transmitted in one direction of rotation, the toothed discs for that direction of rotation can be thinner than those for the other direction of rotation, and so on.

[0056] In the description and claims, the terms "front", "back", "top", "bottom", "inside", "outside" and so on are used in their common form and, where applicable, with reference to the object in its usual position of use.

[0057] In the description and claims, "essentially" means a deviation of up to 10% of the specified value, if physically possible, both downwards and upwards; otherwise, only in the sensible direction. For degree specifications (angle and temperature), this means ± 10°.

[0058] Unless otherwise specified, the term "combination" or "combinations" refers to all types of combinations, from two of the components in question to a multitude or all such components; the term "containing" also refers to "consisting of".

[0059] The features and variants specified in the individual embodiments and examples can be freely combined with those of the other examples and embodiments and, in particular, used to characterize the invention in the claims without necessarily including the other details of the respective embodiment or example. In particular, the different types of adjustment elements can be freely combined with the different types of tooth shapes.

Claims

Patent claims:

1. Gear (1) with at least two rows of circumferential teeth offset both axially and in the direction of rotation, characterized in that the gear has toothed disks (5, 6) of identical construction.

2. Gear (1) according to claim 1, characterized in that the magnitude of the radian between the tooth flanks of all circumferential teeth which engage successively in one direction of rotation is identical.

3. Gear 1, according to claim 1 or 2, characterized in that the toothed discs (5, 6) are provided with features for self-positioning or with integrated mounting jigs.

4. Gear 1 according to claim 3, characterized in that the toothed discs (5, 6) are connected to a shaft by frictional or positive locking.

5. Gear 1 according to claim 4, characterized in that the toothed discs (5, 6) are rotatably and slidably arranged on a common shaft and are connected by clamping elements (15, 16) to a sleeve which is non-rotatably connected to the shaft.

6. Gear according to one of claims 1 to 3, characterized in that the toothed discs (5, 6) have formations on their side surfaces which are designed and positioned such that the axial action of the clamping elements (15, 16) finely adjusts the position in the direction of rotation of the rows of teeth carried by the toothed discs (5, 6) with a tolerance of ± 0.3 mm per toothed disc or less.

7. Gear according to claim 6, characterized in that the features are Hirth teeth (7, 8).

8. Gear according to one of the preceding claims, characterized in that the circumferential teeth of the toothed discs (5, 6) are asymmetrically designed, transmit torques in only one direction of rotation, and at least two identical toothed discs (5, 6) are provided for each direction of rotation of the gear.

9. Gear according to claim 8, characterized in that the circumferential teeth of toothed discs only have the tooth flank section of the head region of an involute toothing located at and / or above the pitch point (22).

10. Gear according to claim 8, characterized in that the circumferential teeth of toothed discs only have the tooth flank section of the foot region of an involute toothing located at and / or below the pitch point (22).

11. Gear according to claim 1, characterized in that the partial modules of groups of several toothed discs add up to different total modules.

12. Gear transmission, characterized in that it has at least one pair of gears according to one of claims 1 to 11.