DE102019132326A1 - Overload protection for gearboxes - Google Patents

Abstract

The invention relates to an overload protection device (1) for a motor vehicle transmission (27) with an inner ring (7, 20) and an outer ring (4, 19), with several pinch rollers between the inner ring (7, 20) and the outer ring (4, 19) (6) are arranged, the pinch rollers (6) being radially preloaded against the inner ring (7, 20) by a spring ring (5) and guided in the circumferential direction by a cage (7, 26) The outer ring (4, 19) relative to the inner ring (7, 20) is made possible by the fact that when a threshold value for the drive torque (Ms) is exceeded, the energy is absorbed in the spring ring (5) and released again after the load has been reduced. The invention also relates to a transmission (27), in particular a motor vehicle transmission, with at least a first transmission shaft (2) and a second transmission shaft (17), with a first gear (8) on the first transmission shaft (2) and a second on the second transmission shaft (17) Gear (18) arranged t, which are in engagement with one another, and wherein such an overload protection (1) is arranged on at least one of the transmission shafts (2, 17).

Description

The invention relates to overload protection for a transmission, in particular a planetary transmission or a shaft transmission, as well as a transmission with such an overload protection according to the preamble of the independent claims.

During various driving maneuvers or technical processes, impulsive load changes can occur in the drive train, which cause an overload in the drive train. The pulsed load changes in the drive train of a motor vehicle can be described both by wheel-side impacts and by load peaks caused by the drive system.

Impacts on the wheel side are mostly caused by driving maneuvers. These include, for example, driving up and down a curb, driving over obstacles on the road or a sudden change in the friction ratio between wheel and road. When driving over an obstacle, the drive train experiences a strong interference pulse, which is due, among other things, to the changing wheel contact force. The resistance acting on the drive train increases when it hits the obstacle. When driving away from the obstacle, there may be another interference pulse, which is caused, for example, by slip when the wheel hits the road.

Another interference pulse can be introduced into the drive train if the parking lock is activated while the motor vehicle is still moving. The motor vehicle is suddenly braked, as a result of which a violent blow is exerted on the drive train. This blow results mainly from the relatively high inertia of the drive motor, which pushes with its inertia against the closing parking lock. The resulting torque peaks lead to high loads in the drive train, which can also result in damage.

To minimize the vibrations occurring in the drive train, either a damper or overload protection can be provided. The functioning of both measures is fundamentally different and accordingly also differs in terms of their design. In the case of a vibration damper, the vibration energy is dissipated from the system and converted into heat by means of suitable damping principles, in particular by means of friction. Overload protection primarily provides for decoupling the drive train and, if necessary, using additional measures to achieve a power loss in order to calm the system. A typical example of overload protection is a slip clutch.

From the DE 195 35 239 C1 a parking lock for a motor vehicle is known which allows the motor vehicle to be parked securely so that it does not roll away. In the case of a rotationally fixed connection between an engagement wheel and a drive shaft, a positive engagement of the pawl is made possible, although the drive shaft still has rotational energy. The ratchet wheel is firmly connected to the drive shaft and the pawl engages the ratchet wheel in a form-fitting manner. As a result, the stationary motor vehicle is reliably prevented from rolling away. So that no damage occurs when the pawl engages in the engagement wheel while the drive shaft is still rotating, the rotational energy is reduced by elastic deformation on the engagement wheel and / or on the pawl.

The EP 2 148 109 B1 discloses a freewheel unit with at least one freewheel ring and at least one freewheel star, wherein clamping bodies are arranged between the freewheel ring and the freewheel star. The freewheel unit comprises at least one cage and at least one damping element, wherein the freewheel star has blocking surfaces and at least one row of circumferentially spaced clamping bodies are arranged between the freewheel ring and the freewheel star. It is provided that each clamping body is arranged between a pair of the blocking surfaces.

The disadvantage of the parking locks and freewheels with damping element known from the prior art, however, is that the units are either exposed to a relatively high mechanical load and thus wear out relatively quickly or are constructed in a correspondingly complex and costly manner.

The object of the invention is to provide overload protection for a transmission, in particular a motor vehicle transmission of an electrically driven motor vehicle, which is comparatively simple and inexpensive and overcomes the disadvantages known from the prior art and thus reliably protects the transmission from overload.

According to the invention, this object is achieved by overload protection for a motor vehicle transmission with an inner ring and an outer ring, a plurality of pinch rollers being arranged between the inner ring and the outer ring. The pinch rollers are radially pretensioned against the inner ring by a spring ring and are guided in the circumferential direction through a cage. In the event of an overload, the outer ring can be rotated relative to the inner ring, in that when a threshold value for the drive torque is exceeded, the energy is absorbed in the spring ring and released again after the load has been reduced. Thereby Both light interference impulses, for example when crossing a threshold, and effective overload protection in the event of strong interference impulses are possible. The maximum forces and torques that can be transmitted by the drive shaft can thus be limited, so that the risk of damage to components connected to the drive shaft is reduced.

The features listed in the dependent claims allow advantageous improvements and further developments of the overload protection specified in the independent claim.

In a preferred embodiment of the invention it is provided that the outer ring is a parking lock gear of a parking lock and the inner ring is a roller carrier, the parking lock gear being rotatable relative to the drive shaft, and the roller carrier being connected to the drive shaft in a rotationally fixed manner. Since activating the parking lock in a motor vehicle that is still rolling induces particularly high overload surges into the drive train, it is advantageous to provide the parking lock with an overload protection device according to the invention in order to decouple such overload surges from the drive train.

In an advantageous embodiment of the invention it is provided that the roller carrier has an internal toothing which is in positive engagement with an external toothing of the drive shaft. This enables a particularly simple and operationally reliable connection between the roller carrier and the drive shaft.

In a further improvement of the invention it is provided that several stops, preferably several stops evenly distributed over the circumference of the parking lock wheel, are formed on the parking lock gear, which protrude in the radial direction beyond the inner diameter of the parking lock gear, the stops causing the movement of the pinch rollers limit, and wherein the stops preload the spring ring in the radial direction. In this way, overload protection can be created which dampens torque peaks and, in the event of an overload, temporarily stores the mechanical energy in the spring ring. In the event of an overload, the pinch rollers slide over the stops, whereby the frictional connection is briefly interrupted in order to reduce the overload.

In a preferred embodiment of the overload protection it is provided that recesses are formed on the roller carrier in which the clamping rollers are positively received, the clamping rollers protruding in the radial direction over the outer contour of the roller carrier. By means of recesses in the roller carrier, a form-fitting reception of the clamping rollers in the roller carrier can be realized in a particularly simple and inexpensive manner. In addition, the roller carrier acts like a cage and keeps the pinch rollers at a defined distance from one another.

In an advantageous embodiment of the invention it is provided that a rotation of the parking lock gear relative to the roller carrier causes a deformation of the spring ring. As a result, the energy of the overload surge can be temporarily stored in the spring ring in a simple manner.

In an alternative embodiment of the invention, it is provided that flat depressions are formed on the roller carrier, which have a ramp contour on which the clamping rollers can roll.

In a further preferred embodiment of the invention it is provided that the outer ring is an outer ring of a freewheel and the inner ring is an inner ring of the freewheel, the clamping rollers being guided in a cage between the inner ring and the outer ring and being prestressed in the radial direction with a spring ring. When a threshold torque is exceeded, the spring ring can slip through with respect to the outer ring, which means that alternatively or in addition to the reversible deformation of the spring ring, a torque limitation for overload protection can be implemented.

In an advantageous improvement of the invention, it is provided that several clamping ramp pairs, preferably evenly distributed over the circumference, are formed on the spring ring, the clamping rollers each resting on a clamping ramp of the clamping ramp pair when the inner ring is rotated relative to the outer ring and a reversible one in the event of an overload Cause deformation of the spring ring.

In an advantageous improvement of the invention it is provided that the clamping ramps have a different slope in the pulling direction than the clamping ramps in the pushing direction. Thus, the torque that can be transmitted can be configured differently in the pulling and pushing directions. In this way, the transmission of force and torque in the main transmission direction can be strengthened, while the feedback into the drive train can be minimized.

Another aspect of the invention relates to a transmission, in particular a motor vehicle transmission, particularly preferably a planetary gear in a motor vehicle, with a first gear shaft and a second gear shaft, with a first gear on the first gear shaft and on the second Transmission shaft a second gear is arranged, which are in engagement with each other, wherein such an overload protection is arranged or formed on at least one of the transmission shafts. As a result, interference pulses can be dampened and overload disturbances, in particular hard impacts from wheel-side obstacles or high rigidity in the drive train, for example when the parking lock is activated while the drive shaft is still rotating, can be reduced in such a way that mechanical damage to the components is reliably prevented.

The various embodiments of the invention mentioned in this application can be advantageously combined with one another, unless stated otherwise in the individual case.

• 1 ein Ausführungsbeispiel eines erfindungsgemäßen Überlastschutzes für ein Getriebe in einer Explosionsdarstellung;
• 2 einen Schnitt durch eine Parksperre mit einem Parksperrenrad und einem Rollenträger, wobei zwischen dem Rollenträger und dem Parksperrenrad eine Feder angeordnet ist;
• 3 ein Getriebe mit einer ersten Getriebewelle und einer zweiten Getriebewelle, wobei auf der ersten Getriebewelle ein Überlastschutz in der Parksperre integriert ist;
• 4 ein weiteres Ausführungsbeispiel für eine Parksperre mit einem erfindungsgemäßen Überlastschutz;
• 5 ein Ausführungsbeispiel für einen Freilauf mit einem erfindungsgemäßen Überlastschutz;
• 6 den erfindungsgemäßen Überlastschutz in einem unbelasteten Ausgangszustand ;
• 7 den erfindungsgemäßen Überlastschutz nach einer Überlast, bei der die Klemmkörper an den Klemmrampen des Federrings anliegen und diesen verformen; und
• 8 den erfindungsgemäßen Überlastschutz beim Abbau der Überlast, wobei die Klemmrollen durch den Federring wieder in ihre Ausgangsposition zurückgedreht werden.

The invention is explained below on the basis of preferred embodiments with reference to the accompanying figures. The same components or components with the same function are identified with the same reference symbols. Show:

• 1 an embodiment of an overload protection device according to the invention for a transmission in an exploded view;
• 2 a section through a parking lock with a parking lock gear and a roller carrier, wherein a spring is arranged between the roller carrier and the parking lock gear;
• 3rd a transmission with a first transmission shaft and a second transmission shaft, an overload protection being integrated in the parking lock on the first transmission shaft;
• 4th a further embodiment for a parking lock with an overload protection according to the invention;
• 5 an embodiment for a freewheel with an overload protection according to the invention;
• 6th the overload protection according to the invention in an unloaded initial state;
• 7th the overload protection according to the invention after an overload, in which the clamping bodies bear against the clamping ramps of the spring ring and deform it; and
• 8th the overload protection according to the invention when the overload is reduced, the clamping rollers being rotated back into their starting position by the spring ring.

In 1 is a drive shaft 2 with an overload protection according to the invention 1 shown. The drive shaft 2 , in particular a transmission shaft, particularly preferably a transmission input shaft, is by means of a first roller bearing 3rd and a second roller bearing 9 rotatably mounted. The drive shaft 2 has an external toothing 12th on over which a first gear 8th and a roller carrier 7th form-fit with the drive shaft 2 are connected. These are on the first gear 8th and on the roller carrier 7th each with an internal toothing 11 formed, which with the external teeth 12th on the drive shaft 2 is in operative connection. On the parking lock wheel 4th is a locking gear 10 formed with which the drive shaft 2 is locked against rotation in a parking position. On the roll carrier 7th several recesses distributed over the circumference are formed, in each of which a pinch roller 6th is arranged. Between the parking lock wheel 4th and the scooter carrier 7th is a spring ring 5 arranged with which the pinch rollers 6th radially against the roller carrier 7th be biased.

In 2 is a section through the drive shaft 2 shown, which by the parking lock 4th , 7th runs. It can be seen that the internal toothing 11 on the roller carrier 7th form-fitting with the external toothing 12th on the drive shaft 2 is engaged. It can also be seen that the pinch rollers 6th in the recesses of the roller carrier 7th are added and by the spring ring 5 be biased in the radial direction. The pinch rollers are there 6th over the outer diameter of the roll carrier 7th so that the spring washer is only on the pinch rollers 6th and on the inner contour of the parking lock gear 4th is present. On the inner contour of the parking lock wheel 4th are several stops distributed over the circumference 13th formed, which the spring ring 5 Preload in the radial direction. In the event of an overload, the stops can be released from the pinch rollers 6th exceeded, so that the frictional connection is lost for a short time and an overload can be reduced.

In 3rd is a gear 27 with such a drive shaft 2 with overload protection 1 shown. The gear 27 includes a drive shaft 2 , at which a first storage area 14th and a second storage area 15th are trained. The drive shaft 2 is by means of a first roller bearing 3rd and a second roller bearing 9 rotatably mounted. Also on the drive shaft 2 a parking lock wheel 4th and a first gear 8th arranged. On the drive shaft 2 is a stop 16 formed, which as a stop 16 for the first rolling bearing 3rd and the parking lock gear 4th serves. The first gear 8th stands with a second gear 18th engaged, which rotatably with a second gear shaft 17th is connected so that a drive torque from the drive shaft 2 on the second gear shaft 17th can be transferred. The gear 17th is in 3rd shown both in a schematic representation and in a sectional view.

In normal operation, the parking lock gear is 4th by frictional engagement via the spring ring 5 taken and rotates with the drive shaft 2 . The parking lock wheel is thereby 4th over the spring ring 5 and the roller carrier 7th as well as the pinch rollers 6th held in this position via a frictional connection.

In the event of an excessive torque, for example from the drive train or when the parking lock is activated while the drive shaft is still rotating 2 , the parking lock wheel rotates 4th opposite the drive shaft 2 . The pinch rollers run in the process 6th of the roll carrier 7th along a curve on the spring washer 5 . The spring ring 5 is supported by spring systems on the stops 13th on the parking lock wheel 4th from. Thus the parking lock wheel can 4th opposite the drive shaft 2 twist and thus reduce the energy of the overload surge. Because of the attacks 13th on the parking lock wheel 4th can adjust the spring stiffness and the preload of the spring ring 5 to be influenced. In the event of an overload surge, the pinch rollers 6th the attacks 13th exceed, whereby the frictional connection is temporarily canceled and the overload surge can be reduced. Due to the spring preload of the spring ring 5 , which when the roller carrier is rotated 7th relative to the parking lock gear 4th is increased, the energy of the overload surge in the spring washer 5 cached.

The overload torque before which the gearbox 27 is to be protected, can be easily and inexpensively due to the spring stiffness of the spring ring 5 can be set. Different spring washers can be used in the same installation space 5 be installed and thus different limit torques can be realized. In addition, the limit torques can also be set by the geometric design of the stops 13th to be influenced. With such an overload protection 1 Further, comparatively complex and space-intensive measures for overload protection can be dispensed with. By the overload protection according to the invention 1 can be used in the design of the transmission 27 the weight of the gearbox 27 and the costs can be reduced, since the limit torques can be reduced and thus the component strength can also be adapted. The transmission according to the invention 27 can absorb and cushion or dampen overload surges in both directions of rotation.

In 4th is another embodiment of an overload protection 1 for a parking lock wheel 4th shown. There are instead of a roller carrier 7th an inner ring 20th as well as a cage 26th with pinch rollers 6th like a freewheel 23 intended. On the spring ring 5 are, as in 6th shown, per pinch roller 6th one pair of clamping ramps each 24 , 25th provided, depending on the direction of rotation when the inner ring is rotated 20th relative to the parking lock gear 4th one clamping ramp each 24 or 25th with the pinch roller 6th comes into operative connection.

Either a damper or overload protection can be used to minimize the vibrations that occur in the drive train 1 are provided. The functioning of both measures is fundamentally different and accordingly also differs in the design. In the case of a damper, the vibration energy is dissipated from the system by means of suitable damping principles (friction / viscous damping, etc.). An overload protection 1 primarily provides for decoupling the drive train and, if necessary, using additional measures (friction) to achieve a power loss in order to calm the system. A slip clutch is a suitable example here.

In 5 is a further embodiment of an overload protection device according to the invention 1 shown. The overload protection according to the invention 1 has a power transmission mechanism in the manner of a freewheel. The overload protection 1 includes an inner ring 20th on which various pinch rollers on the circumference 6th are arranged. The pinch rollers 6th are with a spring ring 5 against the inner ring 20th radially preloaded. The pinch rollers are in the circumferential direction 5 through a cage 26th guided. The assembly from these parts is preloaded in an outer ring 19th arranged.

How out 5 can be seen, the inner ring 20th of overload protection 1 be a ring gear of a planetary gear. Several planet gears roll on the ring gear 21 from which with a sun gear 22nd are in operative connection and in particular by the sun gear 22nd are driven.

In 6th to 8th is the overload protection 1 shown in a sectional view in different operating states. 6th shows the overload protection 1 in an unloaded initial state.

If torque is introduced into the component, the pinch rollers become 6th into the corresponding clamping ramp 24 , 25th pressed. Over the angle of the clamping ramp 24 , 25th , the preload and the thickness of the spring ring 5 the resulting stiffness gives the maximum transferable torque per pinch roller 6th . If the maximum transferable torque is exceeded, the pinch rollers are overridden 6th via the clamping ramps 24 , ie the pinch rollers 6th which in the cage 26th have a fixed position to each other, twist relative to the spring ring 5 . The pinch roller 6th is then located, for example, in the pair of clamping ramps, where the adjacent clamping roller was previously 6th was positioned.

Basically, in the event of an overload, there is a targeted slip in the overload protection 1 is produced. The opposing pair of clamping ramps 24 , 25th ensures that the overload protection 1 is guaranteed both in pulling and in pushing direction. The clamping ramps 24 , 25th can basically be different in pulling and pushing directions. There is also the possibility of a further embodiment in which the spring washer 5 between the pinch rollers 6th and the inner ring 20th is arranged.

Depending on the preload of the spring washer 5 it may be necessary that this is to the neighboring outer ring 19th or inner ring 20th must be rotationally fixed. The spring ring 5 is preferably designed as a formed part, which is axially attached to the outer ring 19th can be flanged.

List of reference symbols

1

Overload protection

2

First gear shaft / drive shaft

3

First roller bearing

4th

Parking lock wheel

5

Spring washer

6th

Pinch roller

7th

Roller carrier

8th

gear

9

Second roller bearing

10

Locking teeth

11

Internal gearing

12th

External gearing

13th

Spring system

14th

First storage area

15th

Second storage area

16

attack

17th

Second gear shaft

18th

Second gear

19th

Outer ring

20th

Inner ring

21

Planetary gear

22nd

Sun gear

23

Freewheel

24

First clamping ramp

25th

Second clamping ramp

26th

Cage

27

Gearboxes / automotive transmissions

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 19535239 C1 [0006]
• EP 2148109 B1 [0007]

Claims (10)

Overload protection (1) for a motor vehicle transmission (27) with an inner ring (7, 20) and an outer ring (4, 19), with several pinch rollers (6) being arranged between the inner ring (7, 20) and the outer ring (4, 19) The pinch rollers (6) are radially preloaded against the inner ring (7, 20) by a spring ring (5) and are guided in the circumferential direction by a cage (7, 26), whereby in the event of an overload, the outer ring (4, 19) is made possible relative to the inner ring (7, 20) in that when a threshold value for the drive torque (Ms) is exceeded, the energy is absorbed in the spring ring (5) and released again after the load has been reduced. Overload protection (1) Claim 1 , characterized in that the outer ring (4, 19) is a parking lock gear (4) and the inner ring (7, 20) is a roller carrier (7), the parking lock gear (4) being rotatable relative to the drive shaft (1), and wherein the roller carrier (7) is non-rotatably connected to the drive shaft (1). Overload protection (1) Claim 2 , characterized in that the roller carrier (7) has an internal toothing (11) which is positively engaged with an external toothing (12) of the drive shaft (2). Overload protection (1) Claim 2 or 3rd , characterized in that stops (13) are formed on the parking lock wheel (4) which protrude inward in the radial direction beyond the inner diameter of the parking lock wheel (4), the stops (13) being able to limit the movement of the pinch rollers (6) and wherein the stops (13) preload the spring ring (5) in the radial direction. Overload protection (1) after one of the Claims 2 to 4th , characterized in that recesses are formed on the roller carrier (7) in which the clamping rollers (6) are positively received, the clamping rollers (6) protruding in the radial direction over the outer contour of the roller carrier (7). Overload protection (1) after one of the Claims 2 to 5 , characterized in that a rotation of the parking lock gear (4) relative to the roller carrier (7) causes a deformation of the spring ring (5). Overload protection (1) Claim 1 , characterized in that the outer ring (4, 19) is an outer ring (19) of a freewheel (23) and the inner ring (7, 20) is an inner ring (20) of the freewheel (23), the pinch rollers (6) in one The cage (26) are guided and preloaded in the radial direction with a spring ring (5). Overload protection (1) Claim 7 , characterized in that several pairs of clamping ramps (24, 25) distributed over the circumference are formed on the spring ring (5), the clamping rollers (6) each on a clamping ramp (19) when the inner ring (20) is rotated relative to the outer ring (19). 24, 25) of the pair of clamping ramps and cause reversible deformation of the spring ring (5) in the event of an overload. Overload protection (1) Claim 8 , characterized in that the clamping ramps (24) have a different slope in the pulling direction than the clamping ramps (25) in the pushing direction. Gear (27) with at least one first gear shaft (2) and a second gear shaft (17), a first gear wheel (8) being arranged on the first gear shaft (2) and a second gear wheel (18) being arranged on the second gear shaft (17) which are in engagement with one another, and wherein an overload protection (1) according to one of the at least one of the transmission shafts (2, 17) Claims 1 to 9 is arranged.

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