Parking lock device for a motor vehicle transmission

Abstract

Parking lock device for a motor vehicle transmission, comprising a parking lock wheel (1) having teeth (3) and tooth gaps (4) and a parking lock pawl (2) having a pawl tooth (5), wherein the parking lock wheel (1) performs a rotary movement with a rotation angle (cp) and a rotational speed (φPoint) about an axis of rotation and the parking lock pawl (2) performs a pivoting movement with a pivot angle (w) and a pivoting speed (ωPoint) about a pivot axis which is arranged parallel to the axis of rotation, wherein the teeth (3, 13) of the parking lock wheel (1) each have a first contour (13a) and, viewed in the direction of rotation (D) of the parking lock wheel (1), each have front and rear tooth flanks (13b, 13c), wherein the pawl tooth (5,15) has a second contour (15a) and relative to the direction of rotation (D) of the parking lock wheel (1) has a front and a rear tooth flank (15b, 15c), wherein the parking lock wheel (1) has an outer radius (r aR ) shows, wherein at least one of the two contours (13a, 15a) is at least partially designed as a mathematical function whose curvature is no more than 20% of an outer curvature of the parking lock wheel (1), which is the reciprocal of the outer radius (r) aR ) of the parking lock wheel (1) is defined, differs, and wherein the teeth (13) and / or the pawl tooth (15) in the area of ​​the front tooth flanks (13b, 15b) of parking lock wheel (1) and / or parking lock pawl (2) have a head retraction (δ) relative to the outer radius (r) aR ) of the parking lock wheel (1), wherein the head retraction (δ) consists of a proportion (δ R ) for the teeth (13) of the parking lock wheel (1) and a proportion (δ K ) for the latch tooth (15), characterized in that the second contour (15a) with reference to the axis of rotation (M R ) is concave.

Description

[0001] The invention relates to a parking lock device for a motor vehicle transmission according to the preamble of claim 1 - known from EP 1 895 206 B1.

[0002] Parking pawls, designed to prevent a vehicle with an automatic transmission from rolling away, are subject to various criteria, in particular the requirement to meet a deflection condition at higher vehicle speeds. Generally, a parking pawl is designed for a specific engagement speed, i.e., a vehicle limit speed, at which the pawl can just barely engage into a tooth gap and the locking position is reached. Above this limit speed, it must be ensured that the pawl tooth does not enter a tooth gap but is deflected by the teeth or the tooth contour. The deflection of the pawl above the engagement speed is referred to as "ratcheting" and, depending on the tooth geometry, results in dynamic forces that can damage the components. It has therefore been suggested that a suitable tooth contour should ensure the softest possible deflection of the pawl.

[0003] EP 1 895 206 B1 discloses a parking lock device for a motor vehicle transmission, comprising a parking lock wheel with circumferential teeth and a parking lock pawl with a pawl tooth or a lug, respectively, which engages in a tooth gap of the parking lock wheel to lock a transmission output shaft. Viewed along the tooth head of the pawl tooth or lug in the direction of rotation of the parking lock wheel, the pawl tooth or lug has a rounded lug contour that follows a defined logarithmic or exponential function. The shape of the logarithmic and exponential functions is characterized by a variable curvature, with the greatest curvature occurring in the region of the leading edge of the lug and the least curvature in the region of the trailing edge. Thus, the curvature of this lug contour decreases across the tooth width in the direction of rotation of the parking lock wheel.This rounded nose is intended to ensure that, above the initial impact velocity and up to the vehicle's maximum speed, the pawl is deflected with a small impulse, particularly one of nearly constant magnitude. However, a disadvantage is that the impulse exerted on the parking pawl during ratcheting is highly dependent on the precise location of the contact point where the pawl tooth engages a tooth on the parking pawl wheel. The resulting variation can be perceived as disruptive by the driver.

[0004] Further parking barriers are known from DE 10 2006 042 637 B4, DE 36 38 045 A1, DE 11 2008 000 433 T5 and US 4 200 002 A.

[0005] The object of the present invention is to achieve, in a parking lock device of the type mentioned above, a deflection of the locking pawl that is as soft and material-friendly as possible above the impact speed up to higher vehicle speeds, and thus to reduce the shock load occurring when the locking pawl ratchets.

[0006] The object of the invention is achieved by a device having the features of claim 1. Advantageous embodiments are described in the dependent claims.

[0007] The invention is based on a parking lock assembly known from the prior art, comprising a parking lock wheel with teeth and tooth gaps, and a parking lock pawl with a pawl tooth, which can engage in one of the tooth gaps of the parking lock wheel by a pivoting movement to lock the parking lock wheel. In this process, the parking lock wheel rotates about its axis of rotation, and the parking lock pawl pivots about its pivot axis, which is arranged parallel to the axis of rotation of the parking lock wheel. In a known manner, the teeth of the parking lock wheel each have a first contour at the tooth head and, viewed in the direction of rotation of the parking lock wheel, front and rear tooth flanks, while the pawl tooth of the parking lock pawl has a second contour at the tooth head and, relative to the direction of rotation of the parking lock wheel, a front and a rear tooth flank.

[0008] The aim of the invention is to achieve a linear relationship between the pivot angle of the parking pawl and the rotation angle of the parking wheel, such that the pivot speed of the parking pawl remains constant. In contrast to the prior art, this results in an impulse exerted on the parking pawl during ratcheting, which, in the area of ​​contact between the head contours of the pawl tooth and the tooth head of the parking wheel, is independent of the precise contact point. The magnitude of the pivot speed, i.e., the change in the pivot angle, is a measure of this impulse. The constant impulse on the parking pawl reduces the shock excitation during ratcheting, and thus also the stress on the components.

[0009] To approximate this linear kinematics, the invention provides that the first contour provided on the tooth head of the parking lock gear teeth and / or the second contour provided on the pawl tooth of the parking lock pawl are at least partially designed as a mathematical function whose curvature deviates by no more than 20% from the outer curvature of the parking lock gear. The teeth of the parking lock gear and / or the pawl tooth of the parking lock pawl exhibit a defined tooth head recess relative to the outer radius of the parking lock gear in the region of the leading tooth flanks. The outer curvature of the parking lock gear is defined as the reciprocal of the outer radius of the parking lock gear.Ideally, this geometry achieves a linear relationship between the pivot angle of the parking pawl and the rotation angle of the parking wheel, thus ensuring a constant pivot speed of the parking pawl, so that the impulse exerted on the parking pawl during ratcheting is independent of the exact contact point when the head contours of the pawl tooth and the tooth head of the parking wheel make contact.

[0010] According to the invention, the head retraction mechanism comprises a portion for the wheel and a portion for the pawl, wherein the portions preferably behave like the tooth widths of the wheel tooth and the pawl tooth. This ensures that linear kinematics are maintained throughout the entire contact area during tooth contact, i.e., a constant impulse and reduced dynamic load on the parking lock.

[0011] The expert will select a suitable mathematical function that adequately represents this (ideal) linear kinematics within the accuracy required depending on the application, possibly also taking into account manufacturing aspects.

[0012] A first example of such a mathematical function is a circle whose radius deviates by no more than 20% from the outer radius of the parking lock wheel. A second example of such a mathematical function is an ellipse whose semi-axes deviate by no more than 20% from the outer radius of the parking lock wheel. Neither the logarithmic function nor the exponential function known from the prior art can represent the desired linear relationship between the pivot angle of the parking lock latch and the rotation angle of the parking lock wheel with sufficient accuracy.

[0013] Ideally, the first contour is convex with respect to the axis of rotation. The second contour is concave. Alternatively, the convex contour of the parking lock gear teeth can interact with a flat or non-concave pawl tooth. It is also possible for the pawl tooth with a concave tooth contour to interact with a parking lock gear that has tooth contours without a recessed head, i.e., a cylindrical outer contour.

[0014] In a further embodiment, additional tooth recesses are provided in the area of ​​the front and rear tooth flanks, which decrease in curvature towards the center of the tooth according to a circular function. The tooth contour is thus formed by two circular arc segments with different centers. This embodiment is particularly advantageous for forward and reverse travel, i.e., ratcheting in both directions of rotation of the parking pawl, because the parking pawl is reliably repelled in both directions of rotation due to the constant curvature of the tooth contour with a constant impulse. The two circular arc segments can have different lengths relative to the tooth width, for example, in a ratio of 1:2 or 1:3. This division is made with regard to the different forward and reverse travel speeds.

[0015] According to a further embodiment, the radius of the circular arc forming the first and / or second contour lies in a range of 0.8 to 1.2 times the outer radius of the parking lock wheel. In particular, the radius of the circular arc contour is equal to the outer radius of the parking lock wheel; that is, the center of the contour circle lies within this range and is offset from the axis of rotation of the parking lock wheel. A radius of curvature for the first and / or second contour of this magnitude results in a relatively small, constant impulse, i.e., a reduced dynamic load on the parking lock.

[0016] Exemplary embodiments of the invention are shown in the drawing and are explained in more detail below, whereby further features and / or advantages may become apparent from the description and / or the drawing. The drawings show... Fig. 1a, b two intervention situations of a parking lock latch and a parking lock wheel, Fig. 2 a graphical representation of a function of the pivot angle of the latch versus the rotation angle of the wheel of a parking lock device according to the state of the art, Fig. 2a, b, c different impact situations of the parking lock latch on the parking lock wheel, Fig. 3 selected functions of the latch's swivel angle versus the wheel's rotation angle, Fig. 4a, b, c three contact situations of parking lock wheel and parking lock pawl, which are kinematically linked by a linear function of pivot angle and rotation angle, Fig. 5a, b, c a further embodiment of the invention with double-sided head retraction and linear kinematics, Fig. 6a, b, c a further embodiment of the invention for an optimized tooth contour on the gear tooth and the corresponding kinematics, Fig. 7a, Fig. 7b, Fig. 7c a further embodiment of the invention for an optimized tooth contour on the pawl tooth and the corresponding kinematics, Fig. 8 a schematic representation of a gear tooth with tooth contour according to the invention and Fig. 9 a schematic representation of a latch tooth with tooth contour according to the invention.

[0017] The Fig. 1a and Fig. Figure 1b shows two contact positions between a parking lock wheel 1 and a parking lock pawl 2 of a parking lock device (not fully illustrated), which can be used, for example, in an automatic transmission or a dual-clutch transmission of a motor vehicle. As is known, the parking lock device serves to mechanically block a transmission output shaft (not shown) to prevent the vehicle from rolling away. The parking lock wheel 1 is rotationally fixed to the transmission output shaft (not shown) and rotates in the direction of arrow D with an angle of rotation φ and a rotational speed φ̇. The parking lock pawl 2 is pivotally mounted in a transmission housing (not shown) and, when the two tooth heads are in contact, pivots in the direction of arrow P with a pivot angle ω and a pivotal speed ω̇.The parking lock wheel 1, hereinafter also referred to as wheel 1, has a toothed surface with teeth 3 and tooth gaps 4, while the parking lock pawl 2, hereinafter also referred to as pawl 2, has a pawl tooth 5 which engages in a tooth gap 4 to prevent rotation of the parking lock wheel 1. Fig. Figure 1a shows a first position in which the counterclockwise rotating tooth 3, also called gear tooth 3, touches the pawl tooth 5 at point A. Point A thus marks the beginning of a contact area between gear tooth 3 and pawl tooth 5. Fig. Figure 1b shows a second position, with point B marking the end of the contact area between gear tooth 3 and pawl tooth 5.

[0018] A parking lock device is generally designed for a specific engagement speed, i.e., a vehicle speed limit at which the pawl tooth 5 can just engage the tooth gap 4 and thus engage the locking position. However, a parking lock must also fulfill a so-called deflection condition. This means that if the pawl is engaged at a vehicle speed above the engagement speed—whether through misuse or fault—the pawl tooth 5 must not be able to plunge into the tooth gap 4, which would lead to damage or destruction. Instead, the pawl tooth 5 must be deflected by a suitable tooth geometry, which is generally achieved by a retraction mechanism, e.g., on the pawl tooth. This process of continuous deflection at speeds above the engagement speed is called ratcheting, which is generally associated with a certain degree of dynamic action.The pawl 2 is continuously accelerated and decelerated in the pivoting direction according to arrow P and in the opposite direction. This is also referred to here as an oscillating pivoting motion. The shock load occurring during ratcheting is examined and explained in more detail using the following diagrams.

[0019] Fig. Figure 2 shows the result of an investigation by the applicant, namely the dependence of the pivot angle ω of the pawl 2 on the rotation angle φ of the parking lock wheel 1. The points A, B of the function ω = f(φ) correspond to the points of tangency A, B in Fig. 1a and Fig. 1b. The function ω = f(φ) is characterized by varying slopes: The curve initially rises gently, then transitions into a steeper section, before finally descending slightly again at point B. The pivot angle ω at point B, i.e., at the end of the contact path, can also be described as the radial stroke of the pawl tooth 5 and corresponds to a head retraction δ on the gear tooth 3 and on the pawl tooth 5.

[0020] Fig. 2a, Fig. 2b, Fig. Figure 2c shows different impact situations of the pawl 2 onto the parking lock wheel 1, i.e., of the pawl tooth 5 onto one of the wheel teeth 3. Fig. Figure 2a shows an impact at point A1, i.e., in a region with a relatively shallow slope of the curve. In this case, a shallow slope means that the pivot angle ω of the pawl changes relatively slowly, i.e., the pivot velocity ωpoint is relatively low – thus, the pawl receives a relatively small (rotational) momentum. Fig. Figure 2b shows the pawl impacting at point A2, i.e., in an area with a steeper slope than at point A1. This means the pawl experiences a greater momentum. Momentum is physically defined as the product of mass and velocity; in this case, the velocity is the pivoting velocity ω at the point of the pawl. Fig. 2c finally shows an arbitrary point of impact A n . The in Fig. The curve shown in Figure 2 is based – as mentioned – on the contours of the gear tooth and the pawl tooth according to the prior art. The inventors have thus concluded that the pawl experiences different impulses depending on the point of impact, leading to the dynamics mentioned above. The inventors have therefore recognized a direct correlation between the kinematic relationship of the pawl and the gear in tooth contact and the dynamics of the pawl movement during ratcheting.

[0021] Fig. Figure 3 shows various hypothetical functions for the pawl's pivot angle ω, plotted against the wheel's rotation angle φ, taking into account the aforementioned finding. Three functions, f1, f2, and f3, are shown as examples, where f1 exhibits a progressive curve, f2 a degressive curve, and f3 a linear curve from the beginning to the end of the tooth contact. A straight line g represents the gradient of the degressive function f2, i.e., the slope at a specific point, which corresponds to the pivot velocity ωpoint (ω̇). The variable slopes of functions f1 and f2 have the undesirable effect of making the impact load on the parking pawl dependent on the precise location of the tooth contact. In contrast, the linear function f3, with its constant slope, results in an impulse on the pawl that is at least largely independent of the precise location of the tooth contact.

[0022] Fig. 4a, Fig. 4b, Fig. Figure 4c shows three positions A, B, and C for tooth contact between parking lock wheel 1 and pawl 2, where the wheel tooth 3 and the pawl tooth 5 are designed such that the function ω = f(φ) has a linear relationship. Regardless of whether the pawl tooth 5 engages the wheel tooth 3 in position A, B, or C, the adjacent diagrams show a uniformly increasing pivot angle ω, i.e., a constant pivoting speed ωpoint (ω̇), and thus a constant impulse transmitted from wheel 1 to pawl 2. This significantly reduces the dynamics of the ratcheting process.

[0023] Fig. 5a, Fig. 5b, Fig. Figure 5c shows a further development of the invention, wherein a head recess is provided on the tooth contour on both the leading and the trailing tooth flank. This ensures that the pawl 2 is deflected both when the parking lock wheel 1 is rotated forwards and backwards. The adjacent diagrams of the Fig. Figures 5a to 5c each show a left-hand, linearly rising curve branch and a right-hand, linearly falling curve branch, labeled V and R, respectively. The diagrams depict a symmetrical division for forward and reverse ratcheting. However, an asymmetrical division is also possible, e.g., 1:2 or 2:3. This accounts for the different speeds during forward and reverse travel.

[0024] Fig. 6a, Fig. 6b, Fig. Figure 6c shows a further embodiment of the invention, wherein only one of the two components involved, namely the contour of the gear tooth 3, is optimized such that the functional profile shown in the adjacent diagrams results. The contour of the gear tooth 3 is designed such that for the contact area from Figure A to Figure B ( Fig. 6a, Fig. 6b) a linear progression L of the function ω = f(φ) results. For the tangent area from the position according to Figure B ( Fig. 6b) to the position shown in Figure C ( Fig. 6c) In contrast, an approximately constant course K for the swivel angle w results, since the contour of the pawl tooth 5 is not optimized, but is formed, for example, by a flat tooth head surface.

[0025] One of the Fig. A similar course of the function ω = f(φ) is obtained in sections 6a to 6c if the tooth head of the parking pawl is designed concavely according to the invention and interacts with a parking pawl wheel whose teeth have no head recess, i.e., a cylindrical outer contour. The corresponding embodiment is shown in the Fig. 7a, Fig. 7b and Fig. 7c is shown, where only the contour of the ratchet tooth 5 is optimized in such a way that the function curve ω = f(φ) shown in the adjacent diagrams is obtained.

[0026] Fig. Figure 8 shows a schematic representation of a tooth 13 of a parking lock wheel (not shown) with center point M. R , through which the axis of rotation of the parking lock wheel passes. The parking lock wheel has an outer radius r. aR and a radius r1 - the difference between the two radii is called the head reduction δ RThe profile of the gear tooth 13, i.e., a section perpendicular to the axis of rotation through the center point M, is designated. R The tooth profile comprises a convex tooth head surface 13a, hereinafter also referred to as contour 13a, a tooth flank 13b facing forward in the direction of rotation according to arrow D, and a tooth flank 13c facing backward in the direction of rotation D. The forward tooth flank 13b transitions into contour 13a at point A, and the backward tooth flank 13c transitions into contour 13a at point B. Point A lies on radius r1, while point B lies on the outer radius r. aR , both around the center M R The point A, which lies at the front in the direction of rotation D, is therefore moved by the amount of the head retraction δ. R withdrawn. The head retraction δ R As explained above, it serves to deflect the pawl during ratcheting. According to the invention, the contour 13a between points A and B is a circular arc with outer radius r. aR around a center point M KRformed. The tooth head surface 13a is thus a circular cylindrical surface with a constant curvature, where M KR the center of curvature and r K The radius of curvature is given by the following values: The width of the gear tooth 13 is defined by a sector φ. ZR denoted. The tooth width φ ZK is a key factor in calculating the head return δ R .

[0027] Fig. Figure 9 shows a schematic representation of a pawl tooth 15 of a pawl (not shown). The pawl tooth 15 has a concave tooth head surface 15a, hereinafter also referred to as contour 15a, which extends in the direction of rotation D of the parking pawl (not shown) from a front point A' to a rear point B'. A tooth flank located at the front relative to the direction of rotation D is referred to as the front tooth flank 15b, and a tooth flank located at the rear relative to the direction of rotation D is referred to as the rear tooth flank 15c. With reference to Fig. 8, the point A of the gear tooth 13, therefore, first passes the point A' of the pawl tooth 15. Point B' lies on the outer radius r. aR of the parking barrier wheel around the center point M R The tooth width is defined by a sector φ. ZK The point A' is located relative to point B' by the amount of a head retraction δ. K offset radially outwards. It therefore lies on a radius r2, which is the sum of the outer radius r. aR and the head return δ K for the handle. The total head retraction δ results from the proportion δ R for the wheel and the proportion δ K for the door handle, i.e., the following applies: δ=δR+δK

[0028] According to the invention, the contour 15a between points A' and B' is a circular arc with outer radius r. aR , i.e., the tooth head surface 15a is a hollow cylindrical surface with constant curvature. The center of the circle of curvature is given by MKK and the radius of curvature is given by r K The proportions of the head reductions for the gear tooth 13 and the pawl tooth 15 are proportional to their tooth widths, i.e., the following applies: δR:δK=φZR:φZK.

[0029] Starting from a given total headcount redemption δ, the shares δ then result. R for the wheel and δ K for the handle according to the following two formulas: δR=δ⋅φZR / (φZR+φZK) δK=δ⋅φZK / (φZR+φZK)

[0030] A parking lock wheel with the wheel tooth contour 13a (first contour) and a parking lock pawl with the pawl tooth contour 15a (second contour) result in a linear progression of the function ω = f(φ), as shown in the diagrams according to Fig. 4a, Fig. 4b, Fig. 4c is shown.

[0031] In the illustrated embodiment according to Fig. 8 and Fig. 9 is the radius of curvature r K equal to the outer radius raR However, it is also within the scope of the invention to determine the radius of curvature r. K larger or smaller than the outer radius r aR to choose, e.g., deviating by up to 20% above or below. In practical trials, for example, a variant with a deviation of approximately 10% has proven to be advantageous.

Claims

[1] Parking lock device for a motor vehicle transmission, comprising a parking lock wheel (1) having teeth (3) and tooth gaps (4) and a parking lock pawl (2) having a pawl tooth (5), wherein the parking lock wheel (1) performs a rotary movement with a rotation angle (cp) and a rotational speed (φPoint) about an axis of rotation and the parking lock pawl (2) performs a pivoting movement with a pivot angle (w) and a pivoting speed (ωPoint) about a pivot axis which is arranged parallel to the axis of rotation, wherein the teeth (3, 13) of the parking lock wheel (1) each have a first contour (13a) and, viewed in the direction of rotation (D) of the parking lock wheel (1), each have front and rear tooth flanks (13b, 13c), wherein the pawl tooth (5,15) has a second contour (15a) and relative to the direction of rotation (D) of the parking lock wheel (1) has a front and a rear tooth flank (15b, 15c), wherein the parking lock wheel (1) has an outer radius (r aR ) shows, wherein at least one of the two contours (13a, 15a) is at least partially designed as a mathematical function whose curvature is no more than 20% of an outer curvature of the parking lock wheel (1), which is the reciprocal of the outer radius (r) aR ) of the parking lock wheel (1) is defined, differs, and wherein the teeth (13) and / or the pawl tooth (15) in the area of ​​the front tooth flanks (13b, 15b) of parking lock wheel (1) and / or parking lock pawl (2) have a head retraction (δ) relative to the outer radius (r) aR ) of the parking lock wheel (1), wherein the head retraction (δ) consists of a proportion (δ R ) for the teeth (13) of the parking lock wheel (1) and a proportion (δ K ) for the flap tooth (15) is composed, characterized by , that the second contour (15a) with reference to the axis of rotation (M R ) is concave. [2] Parking lock device according to claim 1, characterized by , that the mathematical function is a circle whose radius is no more than 20% of the outer radius (r) aR ) of the parking barrier wheel (1) differs. [3] Parking lock device according to claim 1, characterized by that the mathematical function is an ellipse whose semi-axes are no more than 20% of the outer radius (r) aR ) of the parking barrier wheel (1) differ. [4] Parking lock device according to claim 1, 2 or 3, characterized by , that the shares (δ R , δ K ) the head retraction (δ) for the teeth (13) and for the palate tooth (15) as their tooth widths (φ) R , φ K ) behave. [5] Parking lock device according to one of claims 1 to 4, characterized by , that the teeth (13) and / or the cleft tooth (15) also exhibit a head retraction in the area of ​​the posterior tooth flanks (13c, 15c), to which circular arc segments are attached. [6] Parking lock device according to any one of claims 1 to 5, characterized by , that the first and / or the second contour (13a, 15a) has a radius of curvature (r K exhibiting values ​​in the range of 0.8 r aR ≤ r K ≤ 1.2 r aR , especially in a range of 0.9 r aR ≤ r K ≤ 1.1 r aR lies, where the outer radius (r) aR ) of the parking barrier wheel. [7] Parking lock device according to claim 6, characterized by , that the radius (r K ) of the first and / or the second contour (13a, 15a) equal to the outer radius (r aR ) of the parking barrier wheel (1). [8] Parking lock device according to any one of claims 1 to 7, characterized by , that the first contour (13a) with reference to the axis of rotation (M R ) is convex.

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