WO2022157143A1

WO2022157143A1 - Method for operating a dog clutch assembly, dog clutch assembly, powertrain, and motor vehicle

Info

Publication number: WO2022157143A1
Application number: PCT/EP2022/051001
Authority: WO
Inventors: Norman Schmidt-Winkel; Martin Ruider; Fabian HARTMANN; Ludwig GEISSELBRECHT; Bastian Schuh
Original assignee: Zf Friedrichshafen Ag
Priority date: 2021-01-21
Filing date: 2022-01-18
Publication date: 2022-07-28
Also published as: DE102021200504A1

Abstract

The invention relates to a method for operating a dog clutch assembly for a motor vehicle, comprising a clutch body, which has first teeth in a first toothing, and an axially movable sliding sleeve assembly with second teeth in a second toothing. The sliding sleeve assembly has a switching ring on the drive side and a sleeve comprising the second toothing on the output side, wherein the switching ring and the sleeve are coupled by a spring element, and in order to actuate the dog clutch assembly, - the sliding sleeve assembling is started from a starting point, - the sliding sleeve assembly reaches a tooth-on-tooth point at which a tooth-on-tooth position of the first teeth and the second teeth can be produced, and - the sleeve is further moved at a maximum speed starting at the tooth-on-tooth point, said maximum speed being ascertained on the basis of the differential rotational speed of the coupling body and the sliding sleeve assembly and the stroke length of the spring element. The invention also relates to a dog clutch assembly, a powertrain, and a motor vehicle.

Description

Method for operating a claw clutch arrangement,

Klauenkupplunqsanordnunq, Antriebsstranq and motor vehicle

The invention relates to a method for operating a dog clutch arrangement for a motor vehicle with a clutch body, the clutch body having first teeth in a first toothing, and an axially movable sliding sleeve arrangement with second teeth in a second toothing, the sliding sleeve arrangement having a switching ring and a sleeve with the second toothing, wherein the switching ring and the sleeve are decoupled by a decoupling element over a predetermined path.

Claw couplings are form-fitting couplings. With these, two gearings are engaged so that torque can be transmitted.

In hybrid vehicles and electric vehicles, there is a need to decouple one or the electrically driven axle or the electric motor, which is an add-on drive, from the rest of the drive train. This can prevent the drag torque of the electric motor from occurring as a power loss. There is a particular need to close the dog clutch while driving and thus allow the electric motor to be coupled during operation.

When engaging the dog clutches, it can happen that the teeth of the clutch elements come to rest on one another and initially do not mesh. This position is called the tooth-on-tooth position. There is the problem of designing the engagement process in such a way that engagement is carried out as quickly as possible and overloading of the electric motor can be reliably avoided.

To solve this problem, it is proposed that to actuate the dog clutch assembly

- the sliding sleeve arrangement is started from a starting point, - the sliding sleeve arrangement reaches a tooth-on-tooth point at which a tooth-on-tooth position of the first teeth and the second teeth can exist,

- The switching ring is moved further from the tooth-on-tooth point at a maximum speed, where

- The maximum speed is determined as a function of the differential speed of the clutch body and the sliding sleeve arrangement and the length of the specified path.

The essence of the invention is that the decoupled path is cleverly utilized during the engagement process in order to ensure a continuous engagement process on the part of the electric motor of the actuator of the claw clutch arrangement, so that the engagement process is also carried out in a minimized time.

To engage, the sliding sleeve arrangement, which consists of a switching ring and a sleeve that are decoupled via a decoupling element, is started. The point at which the sliding sleeve assembly passes the position where tooth-on-tooth may be achieved is known. From this point there are two possibilities: Firstly, there may be a tooth-on-tooth relationship or the teeth mesh, engagement can occur without any problems. In the first case, the actuator can still maintain the engagement process for a while since the switching ring and the sleeve are coupled via the decoupling element. This has a known predetermined path. The shift fork, which moves the sliding sleeve arrangement and which engages the shift ring, can be further displaced around this, even if the sleeve is blocked in a tooth-on-tooth position. If the sliding sleeve arrangement and here the switching ring is moved further from the tooth-on-tooth point at a predetermined maximum speed, a continuous movement can take place and it can be ensured that the electric motor of the actuator does not come to a standstill. Once the specified path has been covered, the electric motor can no longer move the switching ring, since the electromotive torque, which can be limited in this engagement phase, can only apply a specific, specifiable force to the switching ring. At the end of the given path is the Electric motor therefore silent, which should be avoided. The maximum speed depends on the one hand on the differential speed of the clutch body and the sliding sleeve arrangement. The greater the differential speed, the faster a tooth-on-tooth position is overcome. Furthermore, the length of the specified path of the decoupling element must be taken into account. The longer the distance that can be covered, the higher the maximum speed can be.

The differential speed of the clutch body or the sliding sleeve arrangement does not have to be used directly. In particular, the rotational speed in the circumferential direction of the clutch elements does not have to be specified as a rotational speed; instead, for example, an angular speed or any other variable can also be used to describe this speed. Normally, however, speeds are determined. Furthermore, it is not mandatory to record two speeds. The clutch body or the sliding sleeve assembly may, under certain circumstances, have a known speed such that determining one of the two speeds may not be necessary. In this case, it is sufficient to measure a single speed in order to then be able to determine the maximum speed. As a rule of thumb, it can be stated that the greater the differential speed and the longer the specified path, the greater the maximum speed can be.

The decoupling element can preferably be designed as a spring element with a stroke. The specified path is then the stroke path. With a spring element, the switching ring and the sleeve are simultaneously connected to each other and decoupled for the stroke. In the following, the focus is on the spring element and the stroke without restricting the generality.

If a tooth-on-tooth position was present, the procedure described enables accelerated engagement to take place once this position has been overcome by the spring element. By setting the maximum speed, continuous engagement is enabled, reducing the engagement time can be minimized. In particular, braking of the actuator and the switching ring can be prevented.

Advantageously, the stroke of the spring element can be smaller than the coupling path of the sleeve. It can thereby be ensured that at least at certain points in time it is clear what the state of the dog clutch arrangement is, ie whether it is engaged.

The maximum speed can preferably be set in such a way that the tooth-on-tooth position is overcome at least once while the sleeve is covering the stroke path. In particular, the maximum speed can be set in such a way that it is overcome exactly once. In order to overcome the tooth-on-tooth position, a tooth must be over a tooth gap. The maximum angle of rotation or path of rotation that has to be covered in order to move from a position in which there is just a tooth-on-tooth position to a position in which a tooth is over a gap can be calculated purely geometrically. Of course, not only the tooth spacing has to be taken into account, but the teeth can also be beveled and other effects can occur that require a smaller rotational path to overcome the tooth-on-tooth position. If one has the twisting path to be covered in the worst case, the speed difference also results in a time in which this path is covered at the latest. Based on this time and the stroke of the spring, the maximum speed can be determined. If the switching ring moves at maximum speed, the sleeve is pressed against the teeth of the coupling body by the spring element in the worst case until the end of the stroke. At the latest at the end of the specified path, here the stroke, the tooth-on-tooth position is overcome and the toothing of the sleeve engages. Thus, at this point in time, it can be assumed that the toothing is meshing and that the dog clutch is thus engaged.

However, there can be operating situations in which the tooth-on-tooth position cannot be overcome or is not safely overcome if a safety reserve is observed. This can happen, for example, when a motor vehicle at a Traffic light is stationary or approaching a traffic light and there is a very low differential speed. In this case, it can advantageously be checked at the end of the stroke of the spring element whether a tooth-on-tooth position is present. In this case, a favorable relative position of sleeve and clutch body can still have existed at the beginning of the engagement process, so that the claw clutch was engaged from the start. However, the situation may also have arisen that initially there was a tooth-on-tooth position. In this case, the position of the electric motor can be used to determine whether the spring element is already blocking. In this case, there must also be a tooth-on-tooth position. This check can generally be carried out at the end of the stroke of the spring element, but it can also only be carried out if unfavorable boundary conditions are present, such as a differential speed below a predetermined threshold value.

If there is a tooth-on-tooth position, the block position will eventually be reached. If, on the other hand, it is not present, the sleeve moves unhindered to the end position. Further measures are therefore only required in the first case.

Advantageously, the sleeve can be moved further when an engagement is detected. If it is determined at the end of the stroke that the spring is not fully blocked, this means that the sleeve is meshed and the coupling process can be pursued accordingly.

For safety reasons, an upper threshold can also be provided for the differential speed, which can be called the reject limit speed, for example. Above this, an engagement process is not possible.

Advantageously, the dog clutch arrangement can be designed without sensors on the side of the clutch body. Due to the procedure when engaging, the actuator can always be operated at any time and even under unfavorable boundary conditions, without the need for a sensor on the clutch body side. Due to the omission of a sensor on this side, the dog clutch arrangement can be built more cheaply overall. Advantageously, the spring element can be designed as a disk spring. With a disc spring, force can be transmitted uniformly to the sleeve. In this case, the sleeve and/or the switching ring is/are preferably designed in the form of a ring.

Alternatively, the spring element can be designed as a corrugated spring. A corrugated spring is particularly preferred for longer spring deflections.

Expressed more generally, the spring element is preferably annular. As a result, an even power transmission to the sleeve can be achieved.

If a block position is detected at the end of the stroke, the motor torque of the electric motor of the electric axis can be limited. Here, to emphasize it once again, the electric motor of an actuator is meant. In order to enable meshing of the toothing from a standstill or when driving slowly, the torque mentioned is limited so that the meshing of the claw clutch arrangement only takes place at the start of the journey.

In addition, the invention relates to a dog clutch arrangement for a motor vehicle with a clutch body, the clutch body having first teeth in a first toothing, and an axially movable sliding sleeve arrangement with second teeth in a second toothing, the sliding sleeve arrangement having a switching ring and a sleeve with the second toothing , wherein the switching ring and the sleeve are decoupled by a decoupling element over a predetermined path, with an actuator, a switching unit that can be moved axially by the actuator, in particular a shift fork, and a control device, characterized in that the control device for carrying out the method according to one of the preceding claims is formed. The gear teeth of the clutch body and sliding sleeve can extend in the axial or radial direction. Furthermore, the movable sliding sleeve also has axial or radial sliding teeth.

The first teeth and/or the second teeth can advantageously extend in the radial direction. So far, only the teeth of the coupling body and the sleeve have been addressed with the teeth. However, the sleeve can also be connected to a drive shaft via teeth. The toothing can preferably be designed as a fitting toothing. Alternatively, the toothing can be designed as face toothing. Furthermore, a spline and a face spline can also be used. In particular, there can be a spline between the drive shaft and the sleeve and a face spline between the sleeve and the clutch body.

The invention also relates to a drive train for a motor vehicle with a first axle and a second axle, at least one wheel being arranged on each side of each axle and a differential gear being arranged on at least one of the axles. The drive train is characterized in that between the differential gear and one of the wheels a claw clutch arrangement is arranged, which is designed as described.

In addition, the invention relates to a drive train for a motor vehicle with a first axle and a second axle, with at least one wheel being arranged on each side of each axle and the two axles being connected via a cardan shaft. The drive train is characterized in that a dog clutch arrangement is arranged on the cardan shaft as described.

In addition, the invention relates to a drive train for a motor vehicle with a first axle and a second axle, with at least one wheel being arranged on each side of each axle. There is a gear ratio between the rotor and the differential. A shaft, called the intermediate shaft, is part of this gear stage. It advantageously carries at least two spur gears. The powertrain draws characterized in that a dog clutch arrangement is arranged as described on the intermediate shaft.

At least one electric motor, in particular a traction electric motor, is assigned to each of the drive trains described. This can be decoupled from the rest of the drive train with the dog clutch arrangement. The traction electric motor is so named to distinguish it from other powertrain electric motors such as the electric motor of the jaw clutch assembly actuator. Of course, it has a multiple of power, since it is intended to drive the motor vehicle.

The invention also relates to a drive train for a motor vehicle with a first axle and a second axle, at least one wheel being arranged on each side of each axle and a differential gear being arranged on at least one of the axles. The drive train is characterized in that a dog clutch arrangement is arranged in the differential gear as described.

In addition, the invention relates to a motor vehicle with a dog clutch arrangement and/or a drive train. The motor vehicle is characterized in that the dog clutch arrangement and/or the drive train is designed as described.

Further advantages, features and details of the invention result from the following description of exemplary embodiments and figures. show:

1 a motor vehicle,

2 shows a path profile of an actuation process of a dog clutch,

3 shows a dog clutch arrangement in a first position,

4 shows a dog clutch arrangement in a second position, 5 shows a dog clutch arrangement in a third position, and

6 shows a dog clutch arrangement in a fourth position.

1 shows a motor vehicle 1 with two axles 2 and 3. A differential 4 is arranged on at least one of the axles. The axles can be connected via an intermediate shaft 5. So-called side shafts 7 are located between the differential and the wheels 6 of the axles. However, it can just as well be arranged on the sideshaft 7 or in the differential 4 .

Fig. 2 shows the distance 9 of an actuation path. This is given in millimeters, but the given path lengths are basically arbitrary. The sequence of essential points presented below is not limited to the specified path lengths, these can rather be adapted in individual cases.

The sliding sleeve of the dog clutch arrangement 8 is in the disengaged state at the position 10. This can also be referred to as the disengaged position. If the sleeve is then pushed in the direction of engagement, after a certain distance it reaches the tooth-on-tooth position 12. Since the electric motor of the claw clutch arrangement 8 has a rotation angle sensor, it is known when this position has been reached. Since, as will be explained further below, a spring element is arranged between the switching ring and the sleeve, its stroke path 15 can be moved further up to the blocking position 14 without any problems. Once the tooth-on-tooth position has been overcome, the sleeve can also be moved further in the direction of the coupling body until it reaches the end position 16. At the end position 16 the complete overlapping of the switching gearing is established. The stroke is limited either in the tooth base of the shifting teeth or at any stop in the clutch body. At the end position 16, the entire drive train torque/torque can be transmitted. The stroke path 15 is smaller than the engagement path 17. The engagement path 17 is the path that the sleeve or the switching ring travels from position 10 to position 16 when engaging.

3 shows the dog clutch assembly 8 in a first position, namely the disengaged position. Part of a shift fork 20 that engages in a shift ring 22 can be seen. This is connected to the sleeve 28 via a disc spring 24 as a spring element 26 . The switching ring 22, the plate spring 24 and the sleeve 28 together form the sliding sleeve arrangement 30.

Second teeth 34 are located on sleeve 28 as second teeth 32.

These second teeth 34 are to be brought into engagement with first teeth 36 of the first toothing 38 of the clutch body 40 .

The coupling body is axially stationary. That is, its axial mobility is insufficient to engage the dog clutch assembly 8 .

In Fig. 3, the dog clutch assembly 8 is in the disengaged position 10.

Furthermore, a seal 42 is arranged between the switching ring 22 and the sleeve 28 . This can be used in conjunction with the screen 44 to dampen the movement of the sliding sleeve assembly 30 .

4 shows the dog clutch arrangement 8 in the tooth-on-tooth position 12. The first teeth 36 and the second teeth 34 can stand on top of one another. In this position, the entire tooth surfaces do not have to be directly on top of each other, it is sufficient if a small part overlaps. Then the teeth cannot move into the corresponding gaps. The actuator can still move further, since the spring element 26 follows the switching ring 22 first. If there is a tooth-on-tooth position, this can initially be ignored since the spring element 26 is then simply prestressed. The tooth-on-tooth position between the first teeth 36 and the second teeth 34 is namely, at least as long there is a certain differential speed, eventually resolved. The toothings can then mesh, which happens in an accelerated manner, in particular when the spring element 26 is prestressed.

So that the tooth-on-tooth position is safely overcome by the end of the stroke path 15, at least when a required differential speed band is present, the switching ring 22 is moved from the tooth-on-tooth position 12 at a predetermined maximum speed. As stated, this speed is calculated in such a way that the tooth-on-tooth position is resolved before the stroke 15 of the spring element 26 is used up. Of course, the differential speed between the sleeve 28 and the coupling body 40 must be taken into account. The larger this is, the faster the tooth-on-tooth position is overcome. For safety reasons, an upper threshold can be provided, which can be called the reject limit speed, for example. Above this, an engagement process is not possible.

5 shows the dog clutch arrangement 8 in the blocked position 14. Whether there is a blockage here can be determined by an additional measurement of the force or by limiting the force on the electric motor of the actuator of the clutch arrangement. In and of itself, blockages are avoided if the differential speeds are large enough. However, in particular when the motor vehicle is stationary, for example at a red traffic light, it can happen that the tooth-on-tooth position is not overcome before blocking point 14 is reached. However, this does not automatically mean that the spring element 26 is blocked. If the tooth-on-tooth position has not resolved, the possibly force-limited actuator will come to a standstill, which is detected with the aid of the position sensor or angle of rotation sensor. If this is the case, it can be assumed that the spring element is currently blocked. Then the actuator current can be reduced so that damage to the dog clutch assembly can be avoided.

Otherwise, this blocking position of the spring element 26 is already overcome in that meshing of the teeth becomes possible with increasing differential speeds between the sleeve 28 and the clutch body 40 . 6 shows the dog clutch arrangement 8 in the end position 16. The teeth are engaged, in other words meshed and overlap over such a length that the full torque of the traction electric motor of the drive train can be transmitted.

reference sign

motor vehicle

axis

differential

intermediate shaft

wheel

propeller shaft

dog clutch assembly

route

release position

tooth-on-tooth position

block position

stroke distance

final position

engagement travel

shift fork

switching ring

disc spring

spring element

sleeve

Sliding sleeve arrangement second toothing second tooth first tooth first toothing

clutch body

sealing element

recess

Claims

patent claims

1 . Method for operating a dog clutch arrangement for a motor vehicle with a clutch body, the clutch body having first teeth in a first toothing, and an axially movable sliding sleeve arrangement with second teeth in a second toothing, the sliding sleeve arrangement having a switching ring and a sleeve with the second toothing, wherein the switching ring and the sleeve are decoupled by a decoupling element over a predetermined distance, wherein for actuating the dog clutch assembly

- the sliding sleeve arrangement is started from a starting point,

- the sliding sleeve arrangement reaches a tooth-on-tooth point at which a tooth-on-tooth position of the first teeth and the second teeth can exist,

- The sleeve is moved on from the tooth-on-tooth point at a maximum speed, where

2. The method according to claim 1, characterized in that a spring element is used as a decoupling element and the predetermined path is the stroke of the spring element.

3. The method according to claim 2, characterized in that a stroke is used as the stroke of the spring element, which is smaller than the engagement path of the sleeve.

4. The method according to any one of the preceding claims, characterized in that the maximum speed is set so that the tooth-on-tooth position is overcome at least once while covering the predetermined path through the sleeve.

5. The method according to any one of the preceding claims, characterized in that it is checked at the end of the specified path whether a tooth-on-tooth position is present.

6. The method according to claim 5, characterized in that the sleeve is moved further when a meshing is detected.

7. The method according to claim 5, characterized in that the sleeve is stopped upon detection of a blocked position.

8. The method according to any one of the preceding claims, characterized in that the claw clutch arrangement is formed without sensors on the side of the clutch body.

9. The method according to any one of the preceding claims, characterized in that the spring element is designed as a plate spring.

10. Jaw clutch arrangement for a motor vehicle with a clutch body, wherein the clutch body has first teeth in a first toothing, and an axially movable sliding sleeve arrangement with second teeth in a second toothing, the sliding sleeve arrangement having a switching ring and a sleeve with the second toothing, the Shift ring and the sleeve are decoupled by a decoupling element over a predetermined path, with an actuator and a shift element coupled thereto, in particular a shift fork, for moving the shift ring, and a control device, characterized in that the control device for carrying out the method according to one of the preceding claims is formed.

11 . Drive train for a motor vehicle with a first axle and a second axle (2, 3), at least one wheel (6) being arranged on each side on each axle (2, 3) and a differential gear ( 4) is arranged, characterized in that between the differential gear (4) and one of the wheels (6) has a side shaft (7) with a dog clutch arrangement (8) is arranged, wherein the dog clutch arrangement (8) is formed according to claim 10.

12. Drive train for a motor vehicle with a first axle and a second axle (2, 3), wherein on each axle (2, 3) on each side at least one wheel (6) is arranged and the two axles (2, 3) via a cardan shaft (5), characterized in that a dog clutch arrangement (8), which is designed according to claim 10, is arranged on the cardan shaft (5).

13. Drive train for a motor vehicle with a first axle (2) and a second axle (3), at least one wheel (6) being arranged on each side on each axle (2, 3) and on at least one of the axles (2, 3) a differential gear is arranged, characterized in that a dog clutch arrangement (8) is arranged in the differential gear, which is designed according to claim 10.

14. Drive train for a motor vehicle with a first axle (2) and a second axle (3), wherein at least one wheel (6) is arranged on each side of each axle (2, 3) and at least one axle is assigned a traction electric motor and a differential gear is arranged on the axle, with a transmission stage being located between the rotor of the traction electric motor and the differential gear and an intermediate shaft being part of this transmission stage, characterized in that a dog clutch arrangement according to Claim 10 is arranged on the intermediate shaft.

15. Motor vehicle with a dog clutch arrangement and/or a drive train, characterized in that the dog clutch arrangement is designed according to claim 10 and/or the drive train is designed according to one of claims 11 to 14.

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