DEVICE FOR LOCKING A GEARBOX

Description

[0001] The present invention relates to a device for blocking a transmission, which prevents damage to the drive and transmission in the event of incorrect operation or malfunction. State of the art

[0002] In automatic transmissions for motor vehicles, devices for blocking a transmission are used as parking locks to prevent parked vehicles from rolling away unintentionally. Typically, locking gears with tooth gaps are operatively integrated into the drivetrain. When the parking lock is activated, these gears block the rotational movement of the drive by means of pawls that positively engage the tooth gaps. The parking lock gear is operatively connected to one of the transmission shafts and provided with coarse teeth. Suitable transmission shafts are the input shaft, the output shaft, or an intermediate shaft. The tooth gaps are distributed symmetrically around the circumference of the parking lock gear. A locking tooth adapted to the toothing of the parking lock gear is arranged as a counter tooth on the pawl. The pawl is movably mounted in the transmission housing and rests against the transmission housing.The pawl is actively held in the unlocked position by a return spring. When the parking lock is activated, the pawl is pressed towards the parking lock gear by a mechanical locking element. When the teeth of the pawl and parking lock gear are engaged, the mechanical locking element prevents the pawl from disengaging again. The mechanical locking element presses on the back of the pawl towards the parking lock gear and is supported on the transmission housing via a counterbearing. A compensating spring is also arranged on the mechanical pawl. The compensating spring makes it possible to activate the parking lock even when the locking tooth is in a tooth-to-tooth position on the teeth of the parking lock gear. In this position, the parking lock is ready to lock.If the vehicle continues to move while the parking lock is in standby mode, the drive continues to rotate the operatively connected parking lock gear. When the locking tooth is in a tooth-to-gap position with a gap in the parking lock gear teeth, the pawl automatically engages. This means that the vehicle continues to move a few centimeters despite the parking lock being engaged until the parking lock engages and the vehicle is immobilized.

[0003] If the parking lock is activated while the vehicle is moving due to incorrect operation or a malfunction, the locking tooth of the pawl attempts to engage the next tooth gap and lock the transmission by blocking the parking lock gear. If the parking lock gear rotates too quickly due to incorrect operation or a malfunction of the parking lock actuation, the preload of the compensating spring is not sufficient to push the locking element into its locked position. The locking tooth is not pressed deep enough into the tooth gap to achieve the locking effect. Due to the rotation of the parking lock gear, the locking tooth of the pawl is repelled by the subsequent tooth flank of the locking gear toothing and the pawl is pressed towards the unlocked position against the force of the compensating spring.The deflection process is repeated at each tooth of the rotating parking lock gear and is referred to as "ratcheting" due to the characteristic noise. The vibrations caused by the ratcheting are transmitted to the system and lead to increased noise emission. This deflection process is repeated until the rotational speed of the parking lock gear has decreased sufficiently that the compensating spring can press the locking tooth of the pawl completely into a tooth gap in the parking lock gear. The pawl, the locking tooth, and the toothing of the parking lock gear are then positively connected, locking the parking lock gear and thus the entire transmission.A design parameter for the parking lock mechanism is therefore the speed threshold of the vehicle, up to which a safe engagement of the parking lock must be guaranteed and, on the other hand, when the speed threshold of the vehicle is exceeded, engagement of the parking lock is excluded despite the parking lock being activated.

[0004] The engagement speed depends on the number of teeth on the parking lock gear, the size of the tooth gap and the locking tooth, the stiffness of the return spring and the compensating spring, the tooth inclinations on the parking lock gear and the locking tooth of the pawl, as well as the inclinations on the pawl and the pawl back. Using these parameters, the engagement speed of the parking lock can be designed to the desired range. Furthermore, when designing the parking lock mechanism, the maximum permissible rolling distance of the vehicle from a standstill until the locking tooth safely engages with the teeth of the parking lock gear with the parking lock activated from a tooth-on-tooth position must be taken into account. This rolling distance is determined by the gear ratio of the drive from the vehicle wheel to the parking lock gear and the pitch of the parking lock gear.In addition, the material strength and the desired service life are important parameters for the design of the parking lock mechanism.

[0005] EP 1 855 033 A2 shows a parking lock gear with a uniformly arranged external toothing. Furthermore, the pawl with the locking tooth is shown. With such a design, the ratcheting of the locking tooth on the external toothing of the parking lock gear disadvantageously results in impulses in the form of shocks being transmitted to the transmission mechanism and the drive each time the locking tooth is deflected by the external toothing of the parking lock gear. If the locking tooth penetrates deeply into the toothing of the parking lock gear, high forces arise that can lead to lasting damage in the transmission system. For example, tooth damage or tooth breakage, as well as deformation or fractures of the transmission housing and the parking lock mechanism, can occur.In electric drive motors, these shocks can lead to damage due to rotor slippage due to the high rotor moment of inertia of the electric motor and an inelastic connection to the parking lock gear. The periodically recurring shocks when the locking tooth deflects during ratcheting transmit vibrations to the transmission and drive, resulting in increased noise radiation. These periodically recurring shocks can also lead to oscillation of the mechanical locking system, resulting in premature locking of the parking lock at excessively high vehicle speeds. This phenomenon is caused by the elements of the parking lock mechanism not moving in phase. This can cause the locking tooth of the pawl to engage too deeply in a tooth gap in the parking lock gear when ratcheting.Likewise, the locking tooth of the pawl can directly engage a tooth gap in the parking lock gear and thus no longer be deflected by the tooth flanks. This premature locking of the parking lock by the locking element leads to the required engagement speed being exceeded and can cause lasting and irreparable damage to the transmission and drive, even leading to system failure.

[0006] There is therefore a need for a robust and reliable device for locking transmissions that prevents unwanted transmission locking in the event of incorrect operation or malfunction of the parking lock and thus does not cause damage to the transmission and drive and also does not cause increased noise emissions.

[0007] JP 2013 193 465 A, DE 10 2011 081883 A1 and FR 3 031 787 A1 each disclose parking lock gears, wherein FR 3 031 787 A1 has a parking lock gear with an uneven arrangement of tooth gaps on the circumference of the parking lock gear. Disclosure of the invention

[0008] The device according to the invention has the advantage of creating a mechanism for locking the transmission that, in the event of incorrect operation or a malfunction of the parking lock, does not cause damage due to unwanted transmission locking. This parking lock also has the advantage of being robust and functionally reliable, completely independent of additional monitoring, control, and regulation systems, reliably preventing unwanted transmission locking. Furthermore, it advantageously prevents additional damage from vibrations that could damage or destroy bearings, shafts, gears, housings, and, in electric drive systems, even the rotor. Furthermore, increased noise emission is advantageously avoided.

[0009] According to the invention, a device for blocking a transmission with at least one shaft and at least one locking gear arranged coaxially and operatively connected on the shaft is provided, wherein the locking gear advantageously has an uneven arrangement of tooth gaps on the circumference of the locking gear, wherein the tooth gaps are arranged asymmetrically on the circumference of the locking gear with increasing angles Beta 1 to Beta n between the tooth gaps, wherein the angles Beta 1 to Beta n are the angles between the individual tooth gaps and the sum of the angles Beta 1 to Beta n is 360°, and the following relationship applies to the angles Beta 1 to Beta n between the tooth gaps arranged on the circumference of the locking gear: Beta 1 > Beta 2 > Beta 3 > ... > Beta n,

[0010] According to the invention, the size of the angles Beta 1 ... Beta n between the tooth gaps arranged on the circumference of the locking wheel follows a logarithmic gradation. The uneven arrangement of the tooth gaps advantageously calms the parking lock system in the event of incorrect operation or a malfunction and prevents the pawl from oscillating. Advantageously, this prevents the pawl with the locking tooth from penetrating deeply into the tooth gaps of the locking wheel, thus avoiding damage to the transmission and drive. Likewise, increased noise radiation is avoided. The logarithmic gradation of the successive angles between the tooth gaps according to the invention has the advantage that resonant oscillation is reliably avoided due to the logarithmic gradation of the calming sliding paths. The logarithmic gradation also prevents the formation of vibration-inducing harmonics.

[0011] The measures mentioned in the dependent claim enable advantageous further developments of the device specified in the independent claim.

[0012] It is particularly advantageous to choose the number of tooth gaps so that a prime number results. Since prime numbers are only divisible by themselves and by 1 and therefore cannot be represented as the product of two natural numbers greater than 1, this advantageously prevents the formation of resonant oscillations or harmonics.

[0013] Further features and advantages of the present invention will become apparent to those skilled in the art from the following description of exemplary embodiments, which, however, are not to be construed as limiting the invention, with reference to the accompanying drawings. Short description of the drawings

[0014] They show: Fig. 1: a schematic representation of a parking lock device for blocking the transmission with a locking wheel not according to the invention, a parking lock actuation and a pawl with a locking tooth; Fig. 2 : a schematic representation of a locking wheel not according to the invention with tooth gaps arranged in pairs on the circumference; Fig. 3 : a schematic representation of a locking wheel not according to the invention with tooth gaps arranged in pairs on the circumference, wherein a group of teeth is reduced by one tooth gap to achieve an odd number of tooth gaps; Fig. 4 : a schematic representation of a locking wheel not according to the invention with tooth gaps arranged in pairs on the circumference, wherein an additional tooth gap supplements the existing groups of teeth to achieve an odd number of tooth gaps; Fig. 5: a schematic representation of a locking wheel according to the invention with tooth gaps arranged asymmetrically on the circumference of the locking wheel with increasing angles.

[0015] All figures are merely schematic representations of the device or its components. In particular, distances and size relationships are not shown to scale. Corresponding elements in the different figures are provided with the same reference numbers.

[0016] Figure 1shows a schematic representation of a parking lock device 1 for blocking the transmission 2 in a parked vehicle 11, with a locking gear 4 not according to the invention, a locking element 9 and a pawl 7 with a locking tooth 12. The locking gear 4 is operatively connected to a shaft 3 of the transmission 2, so that when the locking tooth 12 of the pawl 7 engages, the locking gear 4 is positively locked and thus movement of the transmission 2 is blocked. The transmission 2 is operatively connected via the drive 16 to at least one vehicle wheel 17 of a vehicle 11, so that the blocked transmission 2 also prevents movement of the vehicle 11. The locking gear 4 of the parking lock device 1 is provided with coarse teeth. The teeth with the tooth gaps 5 are arranged symmetrically on the circumference of the locking gear. A locking tooth 12 adapted to the toothing of the locking wheel 4 is arranged on the locking pawl 7.The pawl 7 is rotatably mounted in the transmission housing 8. The pawl 7 is supported by the bearing in the transmission housing 8. The pawl 7 is actively held in the unlocked position by the return spring 14. When the parking lock device 1 is actuated, a mechanical locking element 9 between the pawl back 15 and the counter-bearing on the transmission housing 8 is pressed by the parking lock actuation 13. This pivots the pawl 7 toward the locking wheel 4, thus preventing the pawl 7 from disengaging when the locking tooth 12 is engaged in a tooth gap 5 of the locking wheel 4. A compensating spring 10 is located on the mechanical locking element 9. This enables the parking lock actuation 13 to be activated even when the locking tooth 12 and the locking wheel 4 are in a "tooth-on-tooth" position. In this state, the parking lock device 1 is ready to lock.If the vehicle 11 continues to roll, the locking wheel 4, which is operatively connected to at least one vehicle wheel 17 via the transmission 2 with its shafts 3 and the drive 16, continues to rotate until the locking tooth 12 of the pawl 7 engages in the next tooth gap 5. This means that the vehicle 11 can still move a few centimeters despite the parking lock device 1 being activated, until the locking of the transmission 2 by the parking lock device 1 takes effect.

[0017] When the vehicle 11 is traveling at high speeds, the parking lock device 1 must under no circumstances block the transmission 2 and thus the drive 16 in the event of incorrect operation or a malfunction, in order to avoid unstable driving conditions of the vehicle 11 due to blocked vehicle wheels 17 and major damage to the transmission 2 and drive 16. If the parking lock actuation 13 is activated in this case, the locking element 9, together with the compensating spring 10, slides between the pawl back 15 and the counterbearing on the housing of the transmission 8. The pawl 7 is thereby pressed onto the parking lock gear 4, the locking tooth 12 attempts to engage the next tooth gap 5 and lock the transmission 2. Due to the traveling movement of the vehicle 11, the locking gear 4 rotates too quickly to push the pawl 7 with the locking tooth 12 into the locking position in the tooth gap 5 of the locking gear 4. The preload of the compensating spring 10 is not sufficient for this.The pawl 7 with the locking tooth 12 is not pressed deep enough into the tooth gap 5 of the locking wheel 4 to achieve the locking effect. As the locking wheel 4 continues to rotate, the locking tooth 12 is repelled by the following tooth flank of the locking wheel 4. The pawl 7 thus presses the locking element 9 against the compensating spring 10 towards the unlocking position. This repelling process is repeated until the rotational speed of the locking wheel 4 has slowed to such an extent that the locking element 9 can press the pawl 7 with the locking tooth 12 completely into a tooth gap 5 of the locking wheel 4. The locking wheel 4 is then positively locked by the locking tooth 12 of the pawl 7.

[0018] Figure 2shows a schematic representation of a locking gear 4 not according to the invention with tooth gaps 5, each of which is combined to form tooth groups 6. The angle between the tooth gaps 5 is always the same size and amounts to 2 x alpha z. The angles alpha 1 to alpha n between the tooth groups 6 are greater than the angle 2 x alpha z between the tooth gaps 5 and add up to 360°. The tooth groups 6 can be arranged symmetrically on the circumference of the locking gear 4 or with unequal angles alpha 1 to alpha n.

[0019] Figure 3 shows a schematic representation of a locking gear 4 not according to the invention, with tooth gaps 5 also arranged in pairs on the circumference, wherein at least one tooth group 6 is reduced by one tooth gap 5 to achieve an odd number of tooth gaps. The tooth groups 6 can also be arranged symmetrically on the circumference of the locking gear 4 or at unequal angles alpha 1 to alpha n.

[0020] Figure 4 shows a schematic representation of a locking gear 4 not according to the invention with tooth gaps 5 also arranged in pairs on the circumference, wherein the tooth groups 6 are supplemented by at least one tooth gap 5 to achieve an odd number of tooth gaps. The tooth groups 6 can in turn be arranged symmetrically on the circumference of the locking gear 4 or at unequal angles alpha 1 to alpha n.

[0021] Figure 5 shows a schematic representation of a locking gear 4 according to the invention with tooth gaps 5 arranged asymmetrically on the circumference of the locking gear 4 with increasing angles. The tooth gaps 5 are arranged at unequal angles Beta 1 to Beta n on the circumference of the locking gear 4. The angles between the individual tooth gaps 5 Beta 1 ... Beta n add up to 360°.

Claims

1. Device (1) for blocking a transmission (2) having at least one shaft (3) and at least one ratchet wheel (4) arranged in a coaxially and operatively connected manner on the shaft (3), wherein the ratchet wheel (4) has a non-uniform arrangement of tooth gaps (5) on the circumference of the ratchet wheel (4), wherein the tooth gaps (5) are arranged asymmetrically on the circumference of the ratchet wheel (4) with increasing angles beta 1 to beta n between the tooth gaps (5), wherein the angles beta 1 to beta n are the angles between the individual tooth gaps (5) and the sum of the angles beta 1 to beta n is 360°, and the following relationship applies to the angles beta 1 to beta n between the tooth gaps (5) arranged on the circumference of the ratchet wheel (4): beta 1 > beta 2 > beta 3 > ... > beta n, wherein the magnitude of the angles beta 1 ... beta n between the tooth gaps (5) arranged on the circumference of the ratchet wheel (4) follows a logarithmic spacing.

2. Device (1) for blocking a transmission (2) according to Claim 1, characterized in that the number of tooth gaps (5) on the circumference of the ratchet wheel (4) corresponds to a prime number.