DE102019133150A1 - Overload protection for gearboxes - Google Patents

Abstract

The invention relates to an overload protection device (1) for a motor vehicle transmission (18) with a drive shaft (2) on which a parking lock wheel (4) is arranged, which is non-rotatably connected to the drive shaft (2), as well as with a gear wheel (7), which is also arranged on the drive shaft (2). A spring (5) is arranged between the parking lock gear (4) and the gear (7). The toothed wheel (7) is positively connected to an external toothing of the drive shaft (2) via internal teeth and is displaceable in the axial direction. The gear wheel (7) has a helical tooth system, whereby an overload on the helical tooth system of the gear wheel (7) causes an axial displacement of the gear wheel (7) against the spring (5), so that the spring (5) when a threshold value is exceeded the drive torque (Ms) acting on the gear (7) absorbs the energy in the spring (5) and releases it again after reducing the load by releasing the spring (5). The invention also relates to a gear (18) with a first gear shaft (2) and a second gear shaft (16), a first gear wheel (7) being arranged on the first gear shaft (2) and a second gear wheel (17) being arranged on the second gear shaft (16) which mesh with one another, the first gear wheel ( 7) and the second gear (17) are toothed by means of helical teeth, and such an overload protection (1) is arranged on at least one of the gear shafts (2, 16).

Description

The invention relates to overload protection for a transmission, in particular a motor vehicle 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.

The EP 2 855 967 A1 discloses a transmission having a first gear disposed on a shaft to rotate the first gear with respect to the shaft in a circumferential direction and with a second gear disposed on the shaft about the second gear and the shaft in common to turn. In this case, a projection is arranged on the first gear which faces the second gear. A stopper rubber which faces the first gearwheel is arranged on the second gearwheel, the stopper rubber being elastically deformed in the circumferential direction when the projection is pressed.

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 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 an overload protection for a motor vehicle transmission with a drive shaft on which a parking lock wheel is arranged, which is connected to the drive shaft in a rotationally fixed manner, and with a gear wheel, which is also arranged on the drive shaft. A spring is arranged between the parking lock gear and the gear. The gear wheel is positively connected to external teeth of the drive shaft via internal teeth and is displaceable in the axial direction. The gear has a helical toothing, one Overload on the helical toothing of the gear causes an axial displacement of the gear against the spring, so that the spring absorbs the energy in the spring when a threshold value for the drive torque acting on the gear is exceeded and releases it again after reducing the load by releasing the spring. This makes it possible to dampen interference pulses, for example when crossing a threshold, as well as impacts on the drive side in the drive train. 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. Another advantage over the overload protectors known from the prior art is the structurally simple design which, in addition to a known transmission without overload protection, only requires one additional component, namely a spring between the parking lock gear and the first gear. This structure means that the drive shaft is only minimally longer in the axial direction than a drive shaft without overload protection. It is also advantageous that such a drive shaft with overload protection does not wear and therefore does not have to be readjusted in comparison to other overload protection measures, for example with regard to clutches.

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 a stop is formed on the drive shaft which secures the parking lock gear in the axial direction. Axial displacement of the parking lock gear can thereby be prevented in a simple and inexpensive manner. In addition, the parking lock wheel can be used to support the spring, so that a fixed stop is formed for the spring.

In an advantageous embodiment of the invention it is provided that the spring rests with a first end on the parking lock gear and with a second end on the gearwheel. As a result, an overload acting on the gear can be used in a simple manner by axially displacing the gear against the spring to temporarily store the energy of the overload in the spring and to dampen a shock in the drive train.

In a further improvement of the invention it is provided that at least one bearing surface for receiving a roller bearing is formed on the drive shaft. A bearing section for receiving a roller bearing is preferably formed on each of the two end sections of the drive shaft. This enables a particularly simple mounting of the drive shaft, in particular in a gear housing.

In a preferred embodiment of the overload protection it is provided that the gear wheel rests against an inner ring of a roller bearing, in particular a tapered roller bearing, in an unloaded initial state. This means that there is no need for an additional locking ring to limit the axial movement of the gearwheel.

It is particularly preferred if the inner ring of the roller bearing is secured against axial displacement on the drive shaft. This can be done, for example, by a locking ring or another locking element or by a non-positive connection between the inner ring and the drive shaft. The design of the roller bearings, in particular the arrangement of tapered roller bearings, allows both axially and radially acting forces to be introduced into a gear housing in a targeted manner.

In an advantageous embodiment of the invention it is provided that the spring is designed as a wave spring, plate spring or spiral spring. The spring is preferably pretensioned in the axial direction in order to ensure a defined contact of the spring on the gearwheel and on the parking lock. A corrugated spring or a plate spring can be used to press the gearwheel against an axial stop in a particularly uniform manner distributed over the circumference. A spiral spring makes it possible to use a particularly simple and inexpensive spring.

Another aspect of the invention relates to a transmission, in particular a motor vehicle transmission, particularly preferably a planetary gear or a shaft gear in a motor vehicle, with a first gear shaft and a second gear shaft, a first gear wheel being arranged on the first gear shaft and a second gear wheel being arranged on the second gear shaft which are in engagement with one another, the first gear wheel and the second gear wheel being interlocked with one another by means of helical teeth, and wherein such an overload protection is arranged or formed on at least one of the transmission shafts. This way, interference pulses can be dampened and the components of the transmission can be protected from damage caused by mechanical overload. Such overload disturbances, in particular hard knocks, which occur as a result of driving over obstacles on the wheel side or as a result of activation of the parking lock while the drive shaft is still rotating, can thus be reduced, and thus mechanical damage of the components is reliably prevented. In addition, the overload torque from which the transmission is to be protected can be set simply and inexpensively via the spring stiffness of the spring. Different limit torques can be achieved for different transmission variants in the same installation space by simply exchanging the springs. The overload protection saves weight and thus costs when designing these gears, since the limit torques are reduced and the component strength can therefore also be reduced accordingly.

In a preferred embodiment of the transmission it is provided that the gear on the first gear shaft and the gear on the second gear shaft have different widths. The first gear on the first gear shaft is preferably wider than the second gear on the second gear shaft. As a result, even in the event of an axial displacement of the first gear due to an overload, it can be ensured that the two gearwheels remain in mesh and torque transmission is not interrupted.

In a preferred embodiment of the transmission it is provided that the transmission is arranged in an electric drive train of a motor vehicle, the first gear shaft being at least indirectly connected to an electric drive motor and the second gear shaft being at least indirectly connected to a driven wheel of the motor vehicle. The use of such a transmission with such overload protection is particularly advantageous in motor vehicles with an electric drive train, since the transmission of electrical drive trains is very short and very stiff, so that they have only a few gear ratios and coupling elements and thus only little energy in the form of elastic Can reduce deformation. It is therefore particularly advantageous to provide appropriate overload protection for such transmissions.

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 ein erfindungsgemäßes Getriebe mit einer ersten Getriebewelle und einer zweiten Getriebewelle in einer schematischen Seitenansicht, wobei auf der ersten Getriebewelle ein Überlastschutz angeordnet ist;
• 3 ein Getriebe mit einer ersten Getriebewelle und einer zweiten Getriebewelle in einer Schnittdarstellung, wobei auf der ersten Getriebewelle ein Überlastschutz angeordnet ist; und
• 4 ein Getriebe mit einer ersten Getriebewelle und einer zweiten Getriebewelle, wobei auf der ersten Getriebewelle ein Überlastschutz angeordnet ist, in einer dreidimensionalen Darstellung.

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 transmission according to the invention with a first transmission shaft and a second transmission shaft in a schematic side view, an overload protection being arranged on the first transmission shaft;
• 3rd a transmission with a first transmission shaft and a second transmission shaft in a sectional view, wherein an overload protection is arranged on the first transmission shaft; and
• 4th a transmission with a first transmission shaft and a second transmission shaft, wherein an overload protection is arranged on the first transmission shaft, in a three-dimensional representation.

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 8th rotatably mounted. This is done in the end sections of the drive shaft 2 one storage area each 12th , 13th educated. The drive shaft 2 has an external toothing 11 on, with which a parking lock wheel 4th and a first gear 7th form-fit with the drive shaft 2 are connected. These are on the parking lock wheel 4th and on the first gear 7th each with an internal toothing 10 formed, which with the external teeth 11 on the drive shaft 2 is in operative connection. On the parking lock wheel 4th is a locking gear 9 formed with which the drive shaft 2 is locked against rotation in a parking position.

On the drive shaft 2 is a stop 14th trained against which the parking lock wheel 4th supported in the axial direction, so that a shift of the parking lock gear 4th is prevented in the axial direction. Between the parking lock wheel 4th and the first gear 7th is a feather 5 , preferably a wave spring 6th , arranged, which with a first end on the parking lock wheel 4th and having a second end on the first gear 7th is present. The gear 7th is in an unloaded initial state on an inner ring of the second roller bearing 8th on, the inner ring by a securing element (not shown) or by a non-positive connection with the drive shaft 2 is secured against axial displacement. The feather 5 is preferably installed under a pretension in an unloaded drive train in order to ensure that the ends of the spring rest reliably 5 on the parking lock wheel 4th and the first gear 7th to ensure.

The first gear 7th has a helical toothing, whereby the on the gear acting forces are diverted and an axial displacement of the gear against the spring 5 cause one to hit the gear 7th acting, defined threshold torque is exceeded. The drive shaft 2 furthermore has a second toothed section 15th on, which is preferably used for the positive connection of the drive shaft 2 can be used with an electric drive motor.

In 2 is a gear 18th with a first gear shaft 2 and a second gear shaft 16 shown. Here is the first gear shaft 2 a drive shaft 2 with overload protection 1 . The gear 18th includes a drive shaft 2 , at which a first storage area 12th for a first rolling bearing 3rd and a second storage area 13th for a second roller bearing 8th are trained. The drive shaft 2 is by means of these two bearings 3rd , 8th , in particular by means of two tapered roller bearings, rotatably mounted. Also on the drive shaft 2 a parking lock wheel 4th and a first gear 7th arranged, each by means of an internal toothing 10 with an external toothing 11 the drive shaft 2 are positively connected. On the drive shaft 2 is a stop 14th formed, which as an axial stop 14th for the first rolling bearing 3rd and the parking lock gear 4th serves. The first gear 7th has a helical toothing and is connected to a second gear 17th engaged, which rotatably with a second gear shaft 16 is connected so that a drive torque from the drive shaft 2 on the second gear shaft 16 can be transferred. Between the parking lock wheel 4th and the first gear 7th is a feather 5 arranged, which preferably as a wave spring 6th is trained.

In normal operation, the first gear moves 7th not in the axial direction and remains in its starting position, with a drive torque from the drive shaft 2 on the second gear shaft 16 is transmitted. The overload protection 1 is included, as in the left figure of 2 shown, not active.

In the event of an excessive torque, for example due to a blow on the drive train, when driving over an obstacle or when the parking lock is activated 4th with the drive shaft still rotating 2 , becomes the first gear 7th by the helical teeth in the axial direction against the spring force of the spring 5 shifted and thus reduces the energy of the moment impact. The overload protection 1 is included, as in the right figure of 2 shown, active. The first gear shifts 7th opposite the second gear 17th , being the first gear 7th wider than the second gear 17th is and also with an axial displacement with the second gear 17th remains engaged.

The overload torque before which the gearbox 18th is to be protected, can be easily and inexpensively due to the spring stiffness of the spring 5 can be set. Different springs can be installed in the same installation space, thus realizing different limit torques. 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 18th the weight of the gearbox 18th and the costs can be reduced, since the limit torques can be reduced and thus the component strength can also be adapted.

This in 2 described gear 18th is in 3rd in a sectional view and in 4th shown in a three-dimensional representation.

List of reference symbols

1

Overload protection

2

First gear shaft / drive shaft

3

First roller bearing

4th

Parking lock wheel

5

feather

6th

Wave spring

7th

First gear

8th

Second roller bearing

9

Locking teeth

10

Internal gearing

11

External gearing

12th

First storage area

13th

Second storage area

14th

attack

15th

Second gear section

16

Second gear shaft

17th

Second gear

18th

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

• EP 2855967 A1 [0006]
• DE 19535239 C1 [0007]

Claims (10)

Overload protection (1) for a motor vehicle transmission (18) with a drive shaft (2) on which a parking lock gear (4) is arranged, which is connected to the drive shaft (2) in a rotationally fixed manner, and with a gear (7) which is also on the Drive shaft (2) is arranged, a spring (5) being arranged between the parking lock gear (4) and the gear (7), the gear (7) being positively connected to an external toothing of the drive shaft (2) via internal teeth and axially Direction is displaceable, wherein the gear (7) has a helical toothing, whereby an overload on the helical toothing of the gear (7) causes an axial displacement of the gear (7) against the spring (5), so that the spring (5) when a Threshold value for the drive torque (Ms) acting on the gearwheel (7) absorbs the energy in the spring (5) and releases it again after reducing the load by releasing the spring (5). Overload protection (1) Claim 1 , characterized in that a stop (14) is formed on the drive shaft (2) which secures the parking lock gear (4) in the axial direction. Overload protection (1) Claim 1 or 2 , characterized in that the spring (5) rests with a first end on the parking lock gear (4) and with a second end on the gearwheel (7). Overload protection (1) after one of the Claims 1 to 3rd , characterized in that at least one bearing surface (12, 13) for receiving a roller bearing (3, 8) is formed on the drive shaft (1). Overload protection (1) Claim 4 , characterized in that the gear wheel (7) rests against an inner ring of a roller bearing (8) in an unloaded initial state. Overload protection (1) Claim 5 , characterized in that the inner ring of the roller bearing (8) is secured against axial displacement on the drive shaft (2). Overload protection (1) after one of the Claims 1 to 6th , characterized in that the spring (5) is designed as a wave spring (6), plate spring or helical spring. Transmission (18) with a first transmission shaft (2) and a second transmission shaft (16), a first gear (7) being arranged on the first transmission shaft (2) and a second gear (17) being arranged on the second transmission shaft (16), which are in engagement with one another, the first gear wheel (7) and the second gear wheel (17) being toothed with one another by means of helical gearing, and with an overload protection device (1) according to one of the at least one of the gear shafts (2, 16) Claims 1 to 7th is arranged. Gear (18) Claim 8 , characterized in that the first gear (7) on the first gear shaft (2) and the second gear (17) on the second gear shaft (16) have different widths. Gear (18) Claim 8 or 9 , characterized in that the transmission is arranged in an electric drive train of a motor vehicle, the first transmission shaft (2) being at least indirectly connected to an electric drive motor and the second transmission shaft (16) being at least indirectly connected to a driven wheel of the motor vehicle.

Images