Switchable freewheel for use in a drive train, motor vehicle drive train comprising the switchable freewheel, method for switching the freewheel

Abstract

The invention relates to a switchable freewheel (1) for use in a drive train (16), comprising a ramp ring (2), on the ramps (3) of which rolling elements (5) guided in a cage (4) are rollably arranged, wherein: an additional ring (6) is provided concentrically to both the ramp ring (2) and the cage (4) in order to form an additional contact face for the rolling elements (5); and a position determination relating to the ramp ring (2) with respect to the cage (4) and with respect to the additional ring (6) is carried out via at least one spring (7) fastened to the ramp ring (2), characterized in that the cage (4) and the spring (7) define a spring-mass system which is configured in such a way that, during operation, switching of the freewheel (1) is forced according to an adjustment speed of the ramp ring (2). The invention also relates to a motor vehicle drive train (16) comprising a switchable freewheel of this kind. The invention also relates to a method for switching a freewheel of this kind.

Description

[0001] P240840

[0002] - 1 -

[0003] Switchable freewheel for use in a drivetrain, motor vehicle drivetrain with the switchable freewheel, method for switching the freewheel

[0004] The invention relates to a switchable freewheel for use in a drive train with a ramp ring on whose ramps rolling elements guided in a cage are arranged to roll, wherein an additional ring is provided concentrically to both the ramp ring and the cage in order to provide an additional contact surface for the rolling elements, wherein a position determination of the ramp ring to the cage and to the additional ring is carried out by means of at least one spring attached to the ramp ring, a motor vehicle drive train with such a switchable freewheel and a method for switching such a freewheel.

[0005] Freewheels for drive trains are generally known from the prior art. The freewheel serves to decouple two rotating shafts and allows one shaft to rotate independently of the other when it slows down or stops. In this context, there are also switchable freewheels that can determine the direction of freewheeling. These usually require mechanical actuators, which are generally expensive and complex. DE 10 2020 104 249 B3 discloses a switchable freewheel comprising a radially outer, annular freewheel outer part and a radially inner, annular freewheel inner part, which rotate coaxially about an axis of rotation. At least one clamping element is arranged between the freewheel outer part and the freewheel inner part, which is guided circumferentially in a clamping element cage. In a first basic operating mode, a basic freewheel function is activated.in which the freewheel outer part rotates as the drive part in a first direction of rotation and presses the clamping body against a basic clamping contour into a basic switching position, thereby establishing a torque-transmitting locking effect, in which both the freewheel outer part and the freewheel inner part rotate at the same speed in the first direction of rotation and the freewheel inner part acts as the output part, wherein the freewheel has a centrifugal actuator acting between the freewheel inner part and the clamping body cage, which, under centrifugal force, adjusts the clamping body cage by a travel distance and thus switches the freewheel from the basic freewheel function to a reverse-acting auxiliary freewheel function, wherein the freewheel has an auxiliary P240840,

[0006] - 2 -

[0007] The clamping contour is spaced in the circumferential direction from the basic clamping contour via a freewheel section, and when the additional freewheel function is activated, the centrifugal actuator presses the clamping body against the additional clamping contour into an additional switching position, forming a torque-transmitting locking effect, which results in the additional load path.

[0008] DE 40 07 208 C2 discloses a torque limiter with an outer ring having a plurality of clutch cam surfaces and spring support surfaces on its inner circumferential surface, an inner body that sits in the outer ring, a plurality of clamping rollers arranged between the respective clutch cam surfaces and the inner body, and springs that are supported on the spring support surfaces and preload the clamping rollers in a direction in which they are clamped between the clutch cam surfaces and the inner body.

[0009] DE 10 2017 124 646 B3 discloses a backstop comprising a rotatable inner ring and a stationary outer ring, as well as a cage arranged radially between the inner ring and the outer ring with at least two pairs of rollers, each consisting of a first and a second roller, wherein a clamping ramp is formed on an outer circumferential surface of the inner ring for each roller of the respective pair of rollers, wherein a radial recess is formed on the inner ring directly adjacent to the respective clamping ramp in the circumferential direction, wherein furthermore the two respective clamping ramps of the respective pair of rollers are designed to lead away from each other in the circumferential direction in opposite directions.and wherein, in a freewheeling operation of the backstop, only one roller of each roller pair simultaneously contacts the inner ring and the outer ring, and the other roller of each roller pair, due to the respective radial recess, does not contact the inner ring, wherein a spring element designed as a wire bending spring is arranged on the inner ring to spring the two rollers of each roller pair at least against the outer ring, wherein the spring element has an annular spring section and two spring arms, wherein the annular spring section elastically couples the two spring arms together. P240840

[0010] - 3 -

[0011] The object of the present invention is to provide an improved drive train with a switchable freewheel for use in the drive train.

[0012] This problem is solved using the features of independent claim 1.

[0013] Furthermore, the problem is solved by a motor vehicle powertrain with the features of independent claim 9.

[0014] Features disclosed in connection with the freewheel according to the invention naturally also apply in connection with the motor vehicle drivetrain and the method according to the invention, and vice versa, so that the disclosure of the individual aspects of the invention always refers to each other or can refer to each other.

[0015] According to a first aspect of the present invention, a switchable freewheel is provided for use in a drive train, with a ramp ring on whose ramps rolling elements guided in a cage are arranged to roll, wherein an additional ring is provided concentrically to both the ramp ring and the cage in order to provide an additional contact surface for the rolling elements, wherein a position determination of the ramp ring relative to the cage and the additional ring is carried out by means of at least one spring attached to the ramp ring, characterized in that the cage and the spring define a spring-mass system which is designed such that, in operation, a switching of the freewheel is forced depending on an adjustment speed of the ramp ring.

[0016] The term drivetrain, as used here, refers to an assembly designed to transmit the power of an engine to the wheels. The drivetrain includes, among other things, an electric motor and an intermediate shaft. Preferably, the drivetrain includes a differential gear. P240840

[0017] - 4 -

[0018] The term "ramp ring" in this context refers specifically to a structural ring with at least one ramp. The ramp ring can be an inner ring of a freewheel. The ramp ring can also be an outer ring of a freewheel.

[0019] The term ramp refers to a structural projection designed to engage with a rolling element when a clamping force is applied. Individual ramps can have different profiles. They can vary in width and be axially offset or aligned.

[0020] The term rolling element, in this context, refers to a structural element that enables rotational movement between the ramp ring and the auxiliary ring. The rolling element can comprise one or more of the following: ball, cylindrical roller, tapered roller, or needle. The rolling elements are guided within a cage. Within the cage, the rolling elements can be spring-loaded by an additional spring that exerts equal or opposing pressure on the rolling element. The rolling element can become jammed.

[0021] In this context, the term "additional ring" refers specifically to an outer ring. The additional ring may, in particular, be connected to an intermediate shaft.

[0022] The spring can consist primarily of one or more springs. It can be attached to the cage or the ramp ring. The spring can engage one or two counter-holders located on the ramp ring and / or cage. Another name for the spring is detent spring. The spring is preferably a wave spring.

[0023] The term "adjustment speed" in this context refers specifically to a change in the speed of the electric motor acting on the ramp ring. The adjustment speed causes a switching impulse to the arrangement of rolling elements or cage, spring, and ramp of the ramp ring. Depending on the direction of rotation of the ramp ring, i.e., left or right, a switching position can be established at a sufficiently high adjustment speed. The switching impulse can cause the rolling elements to jam against the ramp. In this context, a distinction can be made between a first switching position, a second switching position, and a third switching position. P240840

[0024] - 5 -

[0025] The first switching position allows freewheeling, for example, in clockwise direction and torque transmission in counterclockwise direction; the second switching position allows freewheeling in counterclockwise direction and torque transmission in clockwise direction. The third switching position corresponds to a neutral position in which there is no clamping, so freewheeling is possible in both directions of rotation.

[0026] The invention is based on the understanding that an actuator is generally required to engage a freewheel. To enable this switching function, the invention proposes combining the freewheel with the control of the connected electric machine (i.e., electric motor). No further external auxiliary actuators are needed. For this purpose, for example, when the vehicle is stationary, a pulse is initiated from the electric machine, causing the rolling elements to move from their pre-tensioned state to the opposite ramp, thus closing one or more of the freewheel components. A pulse is also initiated from the electric motor to switch the freewheel back to a neutral position. When the rotational speeds are equal, the spring pushes the roller body (i.e., the rolling elements) out of the clamped position and holds it in the neutral position; that is, one or more of the freewheel components are disengaged.This (negative) torque impulse can also be used during forward travel to switch the roller body from the neutral position into the freewheeling mode. This is necessary, among other things, to enable energy recuperation from the electric drivetrain.

[0027] The change in the freewheel's switching state is achieved by a relative rotation of the cage to the ramp ring. Accordingly, a force from the detent spring must be counteracted by another force. For this purpose, a pulse from the motor can be introduced, accelerating the rolling element from a neutral position into the opposite ramp. By accelerating the ramp ring with the electric motor, the cage can be automatically accelerated via the coupling of the detent spring. Due to the cage's inertia, a counterforce arises, depending on the magnitude of the acceleration, which acts against the spring force of the detent spring. If the acceleration is high enough, a relative rotation occurs between the cage and the ramp ring. This relative rotation results in the rolling elements automatically shifting between the P240840

[0028] - 6 -

[0029] Clamp the ramp and additional ring together. Torque can then be transferred to the wheel via the electric motor.

[0030] Advantageous embodiments are claimed in the dependent claims and are explained in more detail below.

[0031] According to a preferred embodiment, the spring can have at least one or two wraps that engage the ramp ring.

[0032] In this context, the term "encirclement" refers to a structural element designed to at least partially encircle a counterpart element of the ramp ring. Preferably, the spring may have at least one further area that at least partially encircles a portion of the cage, directly and / or indirectly.

[0033] In this way, a relative movement between the ramp ring and the rolling element or cage can be enabled, which allows switching.

[0034] According to a preferred embodiment, a freewheel can be provided in which no actuator is used to rotate the cage.

[0035] The rotary motion is caused by an impulse from the electric motor of the drivetrain. This has a positive effect on costs, as an additional actuator can be omitted.

[0036] According to a preferred embodiment, the spring can encompass at least one projection of the cage or two projections of the cage.

[0037] In this way, a relative movement between the ramp ring and the rolling element or cage can be enabled, which allows switching.

[0038] According to a preferred embodiment, the ramp ring can be designed as an inner ring or as an outer ring. P240840

[0039] - 7 -

[0040] According to a preferred embodiment, the additional ring can be designed as an outer ring or an inner ring.

[0041] According to a preferred embodiment, the cage can be designed as an intermediate ring between the inner ring and the outer ring.

[0042] According to a preferred embodiment, the ramp ring can be directly connected to a rotor shaft of an electric motor and / or the additional ring can be connected to an intermediate shaft.

[0043] According to a preferred embodiment, a torsional vibration damper and / or a slip clutch for damping sudden shock loads can be arranged in front of the ramp ring and / or after the additional ring.

[0044] Since the freewheel is engaged by torque pulses from the electric motor, the strength of the pulse can cause a sudden shock load in the drivetrain after it jams. This shock load can be felt by the driver. A torsional vibration damper or a slip clutch can advantageously dampen this sudden shock load so that the driver no longer perceives it.

[0045] Another aspect of the present invention relates to a motor vehicle drive train comprising a switchable freewheel described above, wherein an electric motor is connected to the ramp ring, the auxiliary ring is connected to the intermediate shaft, and the intermediate shaft is connected to a differential gear.

[0046] Another aspect concerns a method for switching the freewheel described above, whereby an electric motor is accelerated so strongly that switching of the freewheel is caused.

[0047] In its initial state, the electric motor may be disengaged and, for example, have no rotational speed. The freewheel may be in the neutral position. The P240840

[0048] - 8 -

[0049] The vehicle can have an initial speed, which allows the output shaft to reach a corresponding rotational speed. To connect the electric motor to the rest of the drivetrain, it can then be accelerated to the existing output speed. The torque required to accelerate the electric motor can be below the system's limit torque for engaging the freewheel. The speed can then be held briefly, thus reducing the torque. Now the freewheel can be engaged. The electric motor can briefly accelerate the system, thereby engaging the freewheel. The torque at the electric motor can be above the system's limit torque during this time. Subsequently, the torque can be reduced to a lower value and held briefly. During this phase, a preload can be built up in the drivetrain.In the final step, the torque can be increased as desired in order to transmit a drive torque for accelerating the vehicle.

[0050] The invention is explained below with the aid of a drawing. The drawing shows:

[0051] Figure 1 shows a freewheel according to the invention;

[0052] Figure 2 shows an exploded view of a freewheel according to the invention.

[0053] Figure 3 shows a freewheel according to the invention in the first switching position,

[0054] Figure 4 shows a freewheel according to the invention in a second switching position,

[0055] Figure 5 shows a freewheel according to the invention in a third switching position, and

[0056] Figure 6 shows a motor vehicle powertrain according to the invention.

[0057] Identical elements are provided with the same reference numerals. Features of the individual embodiments can be interchanged, complemented, or replaced. P240840

[0058] - 9 -

[0059] Figure 1 shows a first embodiment of a switchable freewheel 1. The switchable freewheel 1 is used in a drive train 16. The drive train 16 can be part of an electric vehicle or a hybrid vehicle. The freewheel 1 comprises a ramp ring 2. In this case, the ramp ring 2 is configured as an inner ring 12.

[0060] Ramps 3 are arranged on the ramp ring 2. The freewheel 1 comprises a cage 4 for guiding the rolling elements 5. The cage 4 is designed as an intermediate ring 14. The rolling elements 5 are cylindrical rollers. The freewheel 1 further comprises an additional ring 6. The additional ring 6 is designed as an outer ring 13. The freewheel 1 also includes a spring 7 for determining the position of the ramp ring 2, cage 4, and additional ring 6. The cage 4 and the spring 7 form a spring-mass system designed such that, during operation, the freewheel is forced to engage depending on the adjustment speed of the ramp ring 2. The spring 7 has two wraps 9 that engage two projections 10 on the ramp ring 2. The spring 7 wraps around two projections 11 of the cage 4.

[0061] Figure 2 shows an exploded view of a freewheel 1 according to the invention. The rolling elements 5 are connected to each other via springs 15 for spring action.

[0062] Figure 3 shows a freewheel 1 according to the invention in its first switching position. In this position, the right rolling element 5 is clamped against the ramp 3 of the ramp ring 2. In this state, the vehicle can, for example, drive in reverse.

[0063] Figure 4 shows a freewheel 1 according to the invention in a second switching position. In this position, the left rolling element 5 is clamped against the ramp 3 of the ramp ring 2. In this state, the vehicle can, for example, move forward.

[0064] Figure 5 shows a freewheel 1 according to the invention in a third switching position. In the third switching position, no rolling element 5 contacts the ramp 3 of the ramp ring 2. This is a neutral position. This state enables a complete P240840

[0065] - 10 -

[0066] Separation between inner ring 2 and outer ring 6, or decoupling of the drive train 16. Both rolling elements 5 are arranged in this position such that neither rolling element 5 has contact with a ramp 3. Figure 6 shows a motor vehicle drive train 16 according to the invention. The motor vehicle drive train 16 comprises a switchable freewheel 1. The motor vehicle drive train 16 comprises an electric motor 17, which is connected to the ramp ring 2. The motor vehicle drive train 16 comprises an intermediate shaft for driving a differential gear 19. The intermediate shaft 18 is connected to the additional ring 6.

[0067] P240840

[0068] - 11 -

[0069] Reference symbol list

[0070] 1 Freewheel

[0071] 2 ramp ring

[0072] 3 Ramp

[0073] 4 cage

[0074] 5 rolling elements

[0075] 6 additional rings

[0076] 7 spring

[0077] 8, 9 Grip spring

[0078] 10 lead cage

[0079] 1 1 advantage Ramp Ring

[0080] 12 inner ring

[0081] 13 Outer ring

[0082] 14 Intermediate ring

[0083] 15 Suspension spring

[0084] 16 Powertrain

[0085] 17 Electric motor

[0086] 18 Intermediate shaft

[0087] 19 Differential gears

Claims

P240840 - 12 - Claims 1. Motor vehicle drive train (16) with a switchable freewheel (1 ) for use in the drive train (16), with a ramp ring (2) on whose ramps (3) rolling elements (5) guided in a cage (4) are arranged to roll, wherein an additional ring (6) is provided concentrically to both the ramp ring (2) and the cage (4) in order to provide an additional contact surface for the rolling elements (5), wherein the position of the ramp ring (2) relative to the cage (4) and the additional ring (6) is determined by means of at least one spring (7) attached to the ramp ring (2), wherein the cage (4) and the spring (7) form a spring-mass system, characterized in that a switching of the freewheel (1) is effected by a change in speed of an electric motor (17) acting on the ramp ring (2).

2. Motor vehicle drive train (16) according to claim 1 , characterized in that the spring (7) has at least one wrap (9) or two wraps (9) which engage the ramp ring (2).

3. Motor vehicle powertrain (16) according to claim 1 or 2, characterized in that no actuator is used to rotate the cage (4).

4. Motor vehicle powertrain (16) according to one of the preceding claims, characterized in that the spring (7) encompasses at least one projection (11 ) or two projections (11 ) of the cage (4).

5. Motor vehicle powertrain (16) according to one of the preceding claims, characterized in that the ramp ring (2) is designed as an inner ring (12) or as an outer ring (13).

6. Motor vehicle powertrain (16) according to one of the preceding claims, characterized in that the additional ring (6) is designed as an outer ring (13) or inner ring (12). P240840 - 13- 7. Motor vehicle powertrain (16) according to claim 5 or 6, characterized in that the cage (4) is designed as an intermediate ring (14) between the inner (12) and the outer ring (13).

8. Motor vehicle powertrain (16) according to any one of the preceding claims, characterized in that the ramp ring (2) is directly connected to a rotor shaft of an electric motor (17) and / or the auxiliary ring (6) is connected to an intermediate shaft (18) and / or a torsional vibration damper and / or a slip clutch for damping sudden shock loads are arranged upstream of the ramp ring (2) and / or downstream of the auxiliary ring (6).

9. Motor vehicle powertrain (16) according to one of claims 1 to 8, wherein the additional ring (6) is connected to the intermediate shaft (18) and the intermediate shaft (18) is connected to a differential gear (19).

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