Gears, especially parking ratchets

Abstract

The invention relates to a gear (10), in particular a parking ratchet, comprising an annular body (1) having a first toothing portion (2) arranged on the outer circumference of the annular body for engaging a ratchet pawl (20) and a second toothing portion (3) arranged on the inner circumference of the annular body for positively locking connection with a shaft (30).

Description

Technical Field

[0001] The invention relates to a gear, in particular a parking ratchet for an automatic transmission, an automated transmission or an electric drive, and a parking lock device. Background Art

[0002] The parking lock is the mechanical locking of the transmission output shaft to the transmission housing. In most cases, a pawl fastened to the housing engages the meshing wheel of the output shaft for this purpose. For road vehicles with electric traction drives, a mechanical parking lock is often required, which brakes the drive when the vehicle is stationary in order to prevent the vehicle from rolling unintentionally.

[0003] This is usually achieved by an activatable pawl which engages in a groove of a gear, in particular a parking ratchet. If the parking lock is not engaged when the vehicle is stationary, but rather when the vehicle is at very low speed, impacts may occur on the parking lock when the pawl is engaged. This is the case, for example, when the vehicle is stationary on a gentle slope. This can also happen when a "tooth-to-tooth position" is present when the parking lock is engaged, and the pawl can only engage after the vehicle has rolled away. This can also happen when the parking lock is engaged by the vehicle driver before the vehicle has come to a complete standstill. The parking lock, in particular the pawl and the parking ratchet, must be dimensioned in such a way that they can withstand these loads.

[0004] In electric traction drives, the rotor of the electric motor has a very large moment of inertia. When the parking lock is engaged from a low speed, not only the vehicle but also the rotor of the electric motor must be decelerated, which results in a very large impact load on the parking lock. The impact energy is dissipated by the subsequent torsional vibration process, which is an additional load on the system and has an unpleasant effect on the vehicle occupants.

[0005] Axially translating annular springs are known as structural elements which dampen and absorb impacts, for example as shock-absorbing springs in railway vehicles. Summary of the invention

[0006] The object of the present invention is to provide an alternative gear wheel, in particular a parking ratchet, and an alternative parking lock device.

[0007] This object is achieved by a gear having the features of the invention. This object is also achieved by a parking lock device having such a gear. A preferred design is obtained from other additional technical features.

[0008] The gear, which is in particular a parking ratchet for an automatic transmission, an automated transmission or an electric drive, comprises an annular body. A first toothing for engaging a pawl is arranged on the outer circumference of the annular body. A second toothing for a positively locking connection to a shaft is arranged on the inner circumference of the annular body. Other terms for the parking ratchet are parking locking ring or parking gear.

[0009] The first toothing is designed to cooperate with the pawl in a known manner. The second toothing is provided to be arranged on a shaft of the transmission in a form-fitting manner. The shaft has a third toothing corresponding to the second toothing of the gear.

[0010] A toothing is understood to be a shaped part of a structural element, in particular a ring body or a shaft, which has serrations, pointed teeth or wedges for establishing a connection and / or for increasing friction. The term toothing can refer not only to the shape and arrangement of the teeth, but also to the manufacture of the teeth.

[0011] The parking lock device comprises the previously described gear and a shaft, to which the gear is mounted. In the mounted state of the parking lock device, the second toothing and the third toothing are preferably arranged radially opposite each other with tooth flanks interlocking in a form-locking manner. In other words, there is a shaft-hub connection, which is preferably realized by means of a toothed fit (also known as a spline). A toothed fit is a so-called multiple follower connection, in which the torque is transmitted by the tooth flanks. The shaft is externally meshed and the gear is internally meshed. The toothed fit can be present, for example, in the form of a splined shaft or a radially oriented face tooth meshing (Hirth-Verzahnung). Thus, power, torque or rotational speed can be transmitted from the shaft to the gear.

[0012] The second and third toothings do not have to act radially, ie, they do not have to be arranged radially opposite each other. The second and third toothings can also act axially, ie, they also extend in the axial direction. A face toothing is an example of a flat lateral toothing that acts axially.

[0013] The gears can be mounted on different shafts of the transmission, in particular on the transmission input shaft, on the intermediate shaft of the transmission, on the driven shaft or on a shaft connected to a corresponding shaft. The shaft is particularly preferably the rotor shaft of the electric machine, since the transmission can correspondingly reduce the torque of the wheel via the transmission ratio. Therefore, the size of the gears can be determined to be particularly small.

[0014] The second toothing is designed in particular such that when the pawl engages in the rotating gear, the gear is stretched in the radial direction relative to the positively connected shaft.

[0015] Preferably, the second and third teeth have a plurality of teeth with inclined tooth flanks.

[0016] The surface of the tooth flanks of the teeth of the second and third toothing can be designed in a variety of ways. The inclined tooth flanks can, for example, be flat or convex in their surface, i.e., for example, be rounded. The convex tooth flanks prevent so-called edge loads during the twisting of the second and third toothings. It is conceivable that only the second toothing is convex and the third toothing is flat, or that only the third toothing is convex and the second toothing is flat. It is also conceivable that both the second and third toothings are convex. → Hertzian stress.

[0017] If the pawl of the parking lock device is engaged in the first meshing portion during the rotation of the shaft on which the parking ratchet is mounted, the gear is twisted relative to the shaft and stretched in the circumferential direction. In other words, the diameter of the gear increases. Here, the gear absorbs the impact energy while it buffers the torque impact. In addition, the load acting on the pawl is significantly reduced as a result. In addition, the friction of the second meshing portion also damps the torsional vibration formed, whereby the parking lock device attenuates the subsequent torsional vibration of the torsional vibration system more quickly. During this process, the gear is basically subjected to tensile load. Therefore, in general, the present invention can achieve optimal energy absorption, that is, a uniform energy distribution on the annular body due to the deformation of the annular member.

[0018] The angle of two adjacent tooth surfaces is preferably selected so as to avoid self-locking of the shaft and ensure the reset of the shaft after the parking lock device is unloaded. In a preferred embodiment of the invention, the angle α of two adjacent tooth surfaces opening in the axial direction has an angle between 140° and 166°.

[0019] On the one hand, this angle range prevents the parking lock system from self-locking at too small an angle. In other words, within this angle range, self-locking is prevented when the second and third meshing parts are twisted relative to each other, wherein the parking lock system comprises at least a shaft and a gear. Self-locking should be avoided because a rest state can occur again after the pawl is hung out, wherein the rest state means that the second and third meshing parts are not twisted relative to each other, i.e. the diameter of the gear is the smallest. On the other hand, this angle range enables a spring travel that is large enough to absorb the impact energy. Too large an angle would reduce the spring travel.

[0020] An angle between 150°≤α≤156° has been found to be particularly preferred. This narrow angle range is optimal for preventing self-locking on the one hand and for a sufficiently large spring travel on the other hand.

[0021] According to another aspect of the present invention, a parking lock device is proposed, which comprises the gear wheel described above and a shaft on which the gear wheel is arranged. The advantages explained for the gear wheel also apply to the parking lock device having such a gear wheel.

[0022] The invention is not limited to the combination of features described in the independent claims or in the dependent claims. In addition, it is possible to combine individual features from the claims, the subsequent description of preferred embodiments of the invention or directly from the drawings. The reference of the claims to the drawings by the use of reference signs is not intended to limit the scope of protection of the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Advantageous embodiments of the invention described below are shown in the accompanying drawings. In them:

[0024] Figure 1 The gears in a preferred embodiment are shown in an axial cross-sectional view;

[0025] Figure 2 Shown in stereogram Figure 1 Gears;

[0026] Figure 3 Show Figure 1 A gear having a preferred angle of the second meshing portion;

[0027] Figure 4a , 4b shows the characteristics of the inclined tooth flanks, such as they can be found in the Figures 1 to 3 Used in the implementation method of. DETAILED DESCRIPTION

[0028] Figure 1 A gear 10 in the form of a parking ratchet of a parking lock device (not shown in detail) of a vehicle transmission (not shown) and a pawl 20 are shown, which engages in a first toothing 2 of the parking ratchet 10. The parking ratchet 10 is arranged coaxially with the axis 98. The pawl 20 is arranged coaxially with the axis 99. The two axes 98, 99 are arranged parallel to each other.

[0029] The parking ratchet 10 comprises an annular body 1. The annular body 1 comprises a first toothing portion 2 arranged on the outer circumference of the annular body 1 for embedding a pawl 20. The annular body 1 further comprises a second toothing portion 3 arranged on the inner circumference of the annular body 1 for being connected in a form-locking manner to a shaft not shown. The two toothing portions 2, 3 are radially acting toothing portions. The first toothing portion 2 comprises teeth 4 in a known manner, which have tooth flanks 4a, 4b with straight teeth. There are corresponding recesses between adjacent teeth 4. The inner toothing portion 3 comprises teeth 5 with lateral tooth flanks 5a, 5b. Unlike the tooth flanks 4a, 4b of the teeth 4 of the first toothing portion 2, the tooth flanks 5a, 5b of the teeth 5 of the second toothing portion 3 are inclined. There is an angle α between adjacent inclined tooth flanks 5a, 5b. The angle α is within the range of 150°≤α≤156° (see Figure 3). In other words, the elevation angle of the tooth surfaces 5a, 5b is 12°≤β≤15°.

[0030] Figure 2 The stereogram shows Figure 1 The parking ratchet 10 and the shaft 30 on which the parking ratchet 10 is arranged. The shaft 30 (which is the rotor shaft of the electric motor) has a third toothing 32, which corresponds to the second toothing 3 of the parking ratchet 10. The third toothing 32 is therefore a radially acting toothing, that is, extending in the radial direction, with teeth 34. The teeth 34 have inclined tooth surfaces 34a, 34b. The tooth surface 34a is in contact with the tooth surface 5a, and the tooth surface 34b is in contact with the tooth surface 5b. The shaft 30 (which is currently the rotor shaft of the electric motor not shown in detail) is transferred to the contact surfaces 5a, 5b and thus the parking ratchet 10 via its contact surfaces 34a, 34b in a form-locking manner.

[0031] If the pawl 20 is engaged in the first meshing portion when the parking ratchet 10 rotates, the parking ratchet 10 is twisted relative to the shaft 30 and stretched in the circumferential direction 97, that is, in other words, the radius of the parking ratchet 10 is enlarged. Here, while the parking ratchet buffers the torque impact, the parking ratchet 10 also absorbs the impact energy. As a result, on the one hand, the load acting on the tooth surface 20 can be significantly reduced, and on the other hand, the torsional vibration formed can be damped by the friction of the internal meshing portion.

[0032] Furthermore, the friction of the second toothing damps the torsional vibrations that are formed, whereby the parking lock device damps subsequent torsional vibrations of the torsional vibration system more quickly. During this process, the gear is essentially subjected to tensile loads. In general, therefore, the invention enables optimal energy absorption, i.e. a uniform energy distribution on the ring body, by deformation of the ring.

[0033] In the present example, the torsional vibration system can be described in a simplified manner as follows: The rotor of the electric machine performs torsional vibrations. The torsion spring is formed by the elasticity of all components that are in a force-locked state when the pawl is engaged. This is primarily the elasticity of the corresponding parts of the connecting shaft(s), the elasticity of the parking ratchet 10, the elasticity of the pawl 20 and the elasticity of the housing part that absorbs the forces from the pawl support. The vibration level is essentially formed by the moment of inertia of the rotor of the electric machine.

[0034] Figure 3 Shows Figure 1 , wherein a preferred angle α is additionally drawn in, which in the present case is between 150° and 156°.

[0035] Furthermore, an elevation angle β is shown. This angle β is developed by a tangent line extending through point P1 and a connecting line (which extends through points P1 and P2). Point P1 is a point where adjacent tooth surfaces 5a, 5b intersect, and the intersection point has a minimum distance r1 relative to the axis 98 of the parking ratchet 10. P2 is a point where adjacent tooth surfaces 5a, 5b intersect, and the intersection point P2 has a maximum distance r2 relative to the center point of the parking ratchet 10. This angle β is a so-called elevation angle, and is 12°≤β≤15°.

[0036] The formulated relationship between the angles α and β is:

[0037] α=180-2β.

[0038] Figure 4a and 4b shows the characteristics of the inclined tooth flanks, such as they can be found in the Figures 1 to 3 In the implementation method of Figure 4a In the embodiment, the tooth 5 has inclined and flat tooth flanks 5a, 5b. In contrast, the tooth flanks 34a, 34b of the tooth 34 are inclined and convex. Figure 4b In contrast, the tooth flanks 34a, 34b of the tooth 34 are designed to be inclined and flat, while the tooth flanks 5a, 5b of the tooth 5 are designed to be inclined and convex. Figure 4b The convex tooth flanks 5 a , 5 b of the parking ratchet 10 are shown without the shaft.

[0039] The invention is fully described and explained with the aid of the drawings and the description. The description and explanation are to be understood as examples and are to be understood without limitation. The invention is not limited to the disclosed embodiments. Other embodiments or variants will be apparent to a person skilled in the art when using the invention and when carefully analyzing the drawings, the disclosure and the subsequent claims.

[0040] In the claims, the words "comprising" and "having" do not exclude the presence of further elements or steps. The indefinite article "a" or "an" does not exclude the presence of a plurality. A single element or a single unit may perform the functions of a plurality of the units mentioned in the claims. The simple mention of some measures in several different dependent claims should not be understood as indicating that a combination of these measures cannot be used to the same advantage.

[0041] Reference numerals list

[0042] 1 Ring

[0043] 2 First toothing part, external toothing part

[0044] 3 Second meshing part, inner meshing part

[0045] 4 teeth, first meshing part teeth

[0046] 4a, 4b tooth surface

[0047] 5 teeth, multiple teeth

[0048] 5a, 5b Tooth surface, contact surface

[0049] 6. Recess(s) of first engagement portion

[0050] 7 Recess(s) of second engagement portion

[0051] 10 Gear, parking ratchet

[0052] 20 Pawl

[0053] 30 Shaft, rotor shaft

[0054] 32 Third toothing part

[0055] 34 teeth, third meshing part teeth

[0056] 34a, 34b Tooth surface, contact surface

[0057] 97 Rotation direction of shaft and gear; direction of stretching (circumferential direction)

[0058] 98 Axis of gear or shaft

[0059] 99 Swing axis of ratchet pawl

[0060] P1 Point of the internal toothing with the smallest distance from the center point

[0061] P2 Point of the internal toothing with the greatest distance from the center point

[0062] t Tangent

[0063] d Connection line between P1 and P2

[0064] r1 radius, distance between the center point and P1

[0065] r2 radius, distance between the center point and P2

Claims

1. A gear (10), the gear (10) being a parking ratchet for a parking lock device, the gear comprising an annular body (1), the annular body having: - a first toothing portion (2) arranged on the outer circumference of the annular body for engaging the pawl (20), - a second toothing (3) arranged on the inner circumference of the annular body for positively locking connection with the shaft (30), - in, The second toothing (3) is designed so that when the pawl (20) is engaged in the rotating gear (10), the gear (10) is stretched in a radial direction relative to the shaft connected in a form-locking manner. The second toothing portion (3) has a plurality of teeth (5) with inclined tooth surfaces (5a, 5b), and The angle α of two adjacent tooth flanks (5a, 5b) opening in the direction of the axis (98) is selected to avoid self-locking of the shaft (30) and ensure resetting of the shaft (30) after the parking lock device is unloaded, wherein the angle is 140°≤α≤166°.

2. The gear according to claim 1, wherein: The angle is 150º≤α≤156º.

3. A gear according to any one of the preceding claims, wherein: The first toothing portion (2) and the second toothing portion (3) are radially acting toothing portions.

4. A parking lock device comprising a gear wheel according to any one of claims 1 to 3 and a shaft (30), the gear wheel (10) being arranged on the shaft.

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