WO2020002412A1

WO2020002412A1 - Selector module, differential lock, transfer gearbox and axle selection

Info

Publication number: WO2020002412A1
Application number: PCT/EP2019/066971
Authority: WO
Inventors: Andreas Pfeffer
Original assignee: Zf Friedrichshafen Ag
Priority date: 2018-06-29
Filing date: 2019-06-26
Publication date: 2020-01-02
Also published as: DE102018210691A1

Abstract

The invention relates to a selector module (1) for a differential lock (2) or for axle selection, comprising a dog clutch (5), which has toothing (6), and a selector piston (11), which has a maximum applicable actuation force (11'), the gaps between the teeth of the toothing (6) being wide enough for the dog clutch (5) to be engaged under load. The selector module (1) according to the invention is characterised in that tooth flanks (7, 7') of the toothing (6) have an angle of inclination (α, β, γ) relative to an axial axis (8) of the dog clutch (5) such that the dog clutch (5) is subjected to a disengagement force (14, 14', 14'') under load and that the maximum applicable actuation force (11') is greater than the disengagement force (14, 14', 14''). The invention also relates to a corresponding differential lock, to a corresponding transfer gearbox, and to a corresponding axle selection.

Description

Switching module. Differential lock. Transfer case and axis connection

The invention relates to a switching module for a differential lock or for a

Axle engagement according to the preamble of claim 1 and a corresponding differential lock, a corresponding transfer case and a corresponding axle engagement.

Differential locks are known in the prior art, which are also used in particular in the drive trains of motor vehicles. This

Differential locks enable a distribution of the drive torque to the driven axles or the driven vehicle wheels by blocking a distributor function of the corresponding differential gears, which can facilitate locomotion especially in rough terrain. Axle connections are also known, which make it possible to either drive a vehicle axle or to drag it along. When the vehicle axle is driven, the off-road capability and the traction ability of the vehicle increase, whereas when the vehicle axle is carried along, the fuel consumption is reduced. The engagement or disengagement of the differential locks or the engagement or disengagement of the axle engagement takes place via a shift module suitable for this purpose, which usually has a shift fork, a shift sleeve, a

Shift rod and a shift piston and a shift cylinder comprises.

In this context, EP 0 510 457 B1 describes a positive coupling for a transfer case of a motor vehicle and a method for its actuation. The teeth of the coupling parts have sufficiently large tooth gaps to be inserted even under a relative speed

To enable coupling parts. An undercut in the toothing prevents the clutch from opening under load.

From DE 40 21 653 A1 a claw coupling with a large deflection angle is known, the contact surfaces of the two coupling parts against the

Axial direction are inclined that the clutch can be opened under load. However, there are axial forces that have to be absorbed by a locking device, which takes up space and one

requires a comparatively large number of components. It is not possible to insert the clutch under load.

The known dog clutch arrangements are disadvantageous in that, depending on the design, either the clutch cannot be inserted under load or the clutch cannot be released under load. In addition, they usually consist of a large number of individual parts, which is comparatively complex to manufacture and assemble.

It is an object of the present invention to propose an improved switching module for a differential lock or for an axle connection.

This object is achieved by the switching module for a

Differential lock or for an axle connection according to claim 1 solved.

Advantageous refinements and developments of the invention emerge from the dependent claims.

The invention relates to a switching module for a differential lock or for a

Axis connection, comprising a dog clutch with teeth and a switching piston with a maximum force that can be applied, tooth gaps of the teeth being designed to such an extent that the dog clutch can be closed under load. The switching module according to the invention is characterized in that tooth flanks of the toothing have an inclination angle against an axial axis of the

Have a dog clutch in such a way that the dog clutch engages under load

Disengagement force experiences and that the maximum actuating force that can be applied is greater than the disengagement force.

This results in the advantage that the shift module according to the invention thus enables both the opening of the dog clutch and the closing of the dog clutch under load or at relative speed. This in turn enables one

situation-specific activation or deactivation of a differential lock or an axle connection, since the differential lock or the axle connection can be activated immediately when required and while the vehicle is in motion, and can also be deactivated again immediately when the need is eliminated while the vehicle is in motion. The switching module according to the invention thus allows greater flexibility than known switching modules.

The dog clutch preferably consists of a first coupling part and a second coupling part, the first coupling part having a first toothing and the second coupling part having a second toothing. In the closed state of the dog clutch, the first toothing engages in the second toothing, so that a torque can be transmitted. When the dog clutch is open, the teeth do not mesh and it can

accordingly no torque can be transmitted. Instead, when the claw clutch is open, a relative speed occurs between the first clutch part and the second clutch part when a corresponding vehicle is in operation.

To enable the dog clutch to close under load, what

is guaranteed according to the invention, the toothing, i.e. Thus, both the first toothing and the second toothing must be designed to be correspondingly solid and stable, so that even if the first and second toothing, in particular the tooth tips of the first and second toothing, collide with one another, this does not lead to damage. The tooth gaps of the toothing must also be at least slightly wider than the circumference of the individual teeth of the claw coupling in order to enable mutual engagement even under load.

Due to the inclination of the tooth flanks against the axial axis

closed state of the dog clutch generates a release force according to the invention. The release force comes about because the

Tooth flanks are inclined towards the axial axis in such a way that they run at least slightly pointed from the tooth base to the tooth tip, so that the circumference of a tooth tip is less than the circumference of the associated tooth base. For the purposes of the invention, the axial axis denotes any straight line which runs parallel to the axial axis of the dog clutch, that is to say extends exclusively in the axial direction, but not in the radial direction.

Since the maximum actuating force that can be applied is greater than the disengaging force, an unintentional opening or at least an unintentional slipping of the claw clutch can be reliably prevented during operation of the switching module according to the invention even under high load. The maximum actuating force that can be applied is in particular greater than the disengaging force that is at the maximum permissible

Load on the dog clutch can occur. The maximum actuating force that can be applied is therefore greater than the maximum permissible disengagement force.

The release force depends on the one hand on the torque acting on the claw clutch, but also on the inclination angle of the tooth flanks. Also a surface condition of the tooth flanks and one influenced by it

The coefficient of friction affects the release force.

It is preferably provided that the toothing has no undercut, since an undercut usually prevents the claw clutch from opening under load, since part of the first toothing of the first coupling part engages in the undercut of the second toothing of the second coupling part and vice versa. The torque acting on the dog clutch under load makes opening the dog clutch significantly more difficult or completely prevents it.

It is further preferred that the first coupling part is designed as a claw sleeve. This gives the advantage of being an additional and separate

Shift sleeve for speed synchronization can be dispensed with. The

The switching module according to the invention therefore advantageously dispenses with additional components, which keeps the manufacturing costs and the module weight low.

According to a preferred embodiment of the invention, it is provided that the switching piston is designed as an annular piston. By training the Switching piston as an annular piston can advantageously be arranged directly on a gear shaft on which the claw sleeve or

Shift sleeve itself is arranged. The shift piston is particularly preferably arranged coaxially on the transmission shaft. By the switching piston and the

Claw sleeve or the shift sleeve are arranged together on the shaft, a shift rod, which is usually arranged parallel to the transmission shaft with the shift sleeve and on which the shift piston is usually arranged together with the shift fork, can advantageously be dispensed with. This again saves installation space, manufacturing costs and module weight.

The arrangement of the piston on the transmission shaft, which is made possible in this way, in particular the coaxial arrangement on the transmission shaft, also has the further advantage that a shift fork can also be dispensed with entirely. This not only means that both the module weight and the

Manufacturing costs of the switching module are further reduced, but also the switching times are optimized and the number of parts of the switching module is reduced.

Alternatively, a conventional shift piston can preferably also be used, in which case a shift rod and a shift fork are also required to operate the shift module.

When the switching module is actuated, the switching piston or ring piston is axially displaced on the gear shaft.

The dog clutch and the switching piston are preferably made of metal, in particular steel. This ensures a comparatively high level of robustness and thus longevity of the components, even under regular and high ones

Charges.

According to a preferred embodiment of the invention it is provided that a coupling sleeve of the dog clutch is rotatably mounted axially in the annular piston. The advantage of this arrangement of the coupling sleeve in the ring piston is that that the ring piston can take the coupling sleeve with it and also move it when pressure is applied, which leads to an axial displacement of the switching piston. Since the coupling sleeve is still rotatably mounted in the ring piston, the coupling sleeve can be rotated against the

Ring piston guaranteed. Since the coupling sleeve follows a rotational movement of a gearwheel which is in engagement with the coupling sleeve or an associated shaft in the engaged state, the annular piston can be caused by the

However, rotatability remains at rest. Among other things, this simplifies the production of a reliable pressure tightness of the annular piston with respect to the shift cylinder, since the annular piston does not twist against the shift cylinder.

It is preferably provided that the claw sleeve is mounted coaxially in the ring piston. Thus, when the ring piston is pressurized or the claw sleeve is actuated, no tilting moments between the ring piston and

Claw sleeve created.

According to a particularly preferred embodiment of the invention, it is provided that the claw sleeve or the shift sleeve is rotatably mounted in the annular piston by means of a roller bearing. The roller bearing is more complex than a plain bearing, but it enables comparatively lower friction values to be achieved and thus better efficiency. Another advantage is that the exact position of the ring piston relative to the claw sleeve or shift sleeve is specified via the roller bearing, so that time-consuming work for setting the tooth tip-tooth tip distance and the tooth tip-tooth base distance can be omitted. A prestress necessary for the rolling bearing is preferably generated by an elastic restoring element which urges the ring piston into the idle state in the depressurized state.

The roller bearing is preferably designed as an angular contact ball bearing, as a deep groove ball bearing or as an axial bearing. Alternatively, it is preferably provided that a rolling bearing is provided between the shift fork and the claw sleeve or between the shift fork and the shift sleeve when using a shift fork.

According to a further preferred embodiment of the invention, it is

It is provided that the switching module further comprises a switching cylinder, which is designed to pressurize the switching piston.

Shift cylinders for pressurizing and thus for actuating shift pistons are widespread and technically mature. For example, across from

Servomotors are also a cost-effective solution. be designed to actuate the switching piston using oil or air. The switching cylinder can also be single or double acting.

Depending on the pressurized surface of the switching piston, the pressure generated in this way causes a corresponding force.

According to a further preferred embodiment of the invention, it is

provided that the switching module further comprises an elastic reset element which is designed to connect the switching piston with one of the

to apply pressure-induced force to counteracting force. It is preferably provided that the restoring element is designed as a helical spring or as a plate spring. Coil springs and disc springs can be obtained inexpensively in almost any form of training.

It is preferably provided that the switching piston is pressurized on one side

is acted upon. When a release pressure is reached, the switching module is actuated in such a way that a differential lock is disengaged or an axle engagement is disengaged. In the depressurized state, however, is

Differential lock or the axle engagement preferably engaged. In this case, the actuating force, which prevents the claw clutch from opening under load due to the then disengaging force, is generated by the restoring element. Alternatively, it is preferably provided that the differential lock or the axle engagement are disengaged in the depressurized state. The engagement occurs in this case by pressurizing the switching piston with the

Engagement pressure. Accordingly, the positioning force in this case is determined by the

Pressurization generated. It must be large enough not only to counteract the restoring force that occurs under load, but also to counteract the force generated by the restoring element.

Furthermore, alternatively, preferably, the shift piston shares a shift cylinder

Shift actuators in a release space and an engagement space, the

Release space absorbs the release pressure and the engagement space absorbs the engagement pressure. In this case it is a double-acting one

Shift cylinder.

The coil spring or plate spring is particularly preferably prestressed under pressure.

The restoring element is preferably supported on the claw sleeve. Since the

Claw sleeve is arranged radially within the switching piston, can

Restoring element, in particular if it is designed as a coil spring or

Belleville washer, saves weight and material with comparatively little

Be radial circumference.

According to a further preferred embodiment of the invention, it is

provided that the switching module further comprises a rear piston stop. A front piston stop can advantageously be omitted if the

Coupling sleeve is mounted by means of roller bearings. If there is no rolling bearing, a front piston stop is preferably additionally provided. The front piston stop or the rolling bearing limits the displaceability of the switching piston in a first axial direction and the rear piston stop limits the displaceability of the switching piston in a second axial direction. This has the advantage that the exact position of the shift piston relative to the claw sleeve is specified via the front and rear piston stops, so that too in this case, time-consuming work to set the tooth tip-tooth tip distance and the tooth tip-tooth base distance can be omitted.

The invention also relates to a differential lock for locking a

Distributor function of a transfer case, wherein the differential lock can be engaged and disengaged by means of a switching module. The invention

Differential lock is characterized by the fact that the switching module

switching module according to the invention.

Furthermore, the invention relates to a transfer case with a differential lock. The transfer case according to the invention is characterized in that the

Differential lock is a differential lock according to the invention.

Finally, the invention also relates to an axis connection, the

Axis activation can be activated and deactivated by means of a switching module. The axis connection according to the invention is characterized in that the

Switch module is a switch module according to the invention.

The invention is illustrated below with reference to the figures

Exemplary embodiments explained.

Show it:

1 exemplarily and schematically a known switching module,

2 exemplarily and schematically a toothing of a dog clutch or a second clutch part,

Fig. 3 exemplarily and schematically a further toothing

Claw coupling or a second coupling part,

Fig. 4 exemplary and schematic of a possible form of training

switching module according to the invention,

Fig. 5 exemplarily and schematically a toothing of an inventive

Switching module and

Fig. 6 shows an example of the course of the disengagement force for different

Tilt angle depending on the acting torque. The same objects, functional units and comparable components are identified with the same reference symbols in all figures. This

Objects, functional units and comparable components are identical in terms of their technical characteristics, unless the description explicitly or implicitly states otherwise.

1 shows, by way of example and schematically, a known switching module 1 which is used, for example, for a differential lock 2. As can be seen, the switching module 1 takes up a comparatively large amount of installation space due to its known design with a shift rod 3 and a shift fork 4. This is essentially due to the parallel arrangement of the shift rod 3 to a gear shaft 8, on which the dog clutch 5 is arranged. In the known switching module 1 shown in FIG. 1, it is also necessary to adjust the distance between the tooth heads of a first toothing of a first coupling part 5 ″ of the claw coupling 5 and the tooth heads of a second toothing of a second coupling part 5 ″

To calibrate claw coupling 5 both in the closed and in the open state. Such calibration processes are time-consuming and therefore cost-intensive. The closed state can be locked via a ball lock 15.

Fig. 2 shows an example and schematically a toothing 6 of a dog clutch 5 or a second coupling part 5 ". As can be seen, the tooth flanks 7, 7 'are inclined at an angle of inclination a against an axial axis 8 of the dog clutch. By the angle of inclination a of the tooth flanks 7, 7 'against the axial axis 8 is in

closed state of the dog clutch 5 generates a disengagement force under load.

3 shows an example of a further toothing 6 of a

Claw coupling 5 or a second coupling part 5 ". In contrast to

The toothing 6 of FIG. 2, the toothing 6 of FIG. 3 is inclined towards the axial axis 8 such that an undercut 9 is created. As can be seen, the toothing 6 also has comparatively solid teeth and comparatively large tooth gaps 13. This makes it possible to close the dog clutch 5 even under load. However, the undercuts 9 prevent the claw coupling 5 from opening under load. Fig. 4 shows an example and schematically a possible embodiment of a switching module 1 according to the invention, for example for a differential lock 2. As can be seen first, the switching piston 11 is designed as an annular piston 11. This results in a space-saving design of the whole

Shift module 1 on the transmission shaft 10. The dog clutch 5 comprises a first clutch part 5 ″ and a second clutch part 5 ″. Both the first and the second coupling part 5 ″, 5 ″ have identical toothing 6 (see FIG. 5), tooth gaps 1 1 of the toothing 6 being designed to such an extent that the claw coupling 5 can be closed under load. The tooth flanks 7, 7 ′ of the toothing 6 furthermore have an inclination angle α against a toothing 8 of the dog clutch 5 in such a way that the dog clutch 5 engages under load

Disengagement force experienced. The disengagement force arises from the fact that the tooth flanks 7, 7 'run at least slightly pointed from the tooth base to the tooth tip, that is to say that the circumference of a tooth tip is less than the circumference of the associated tooth base. The greater the angle of inclination a, the greater the disengagement force, depending on an effective torque. In order to avoid inadvertent opening of the closed claw clutch 5 under load, the annular piston 11 is designed such that its maximum actuating force that can be applied is greater than a maximum possible disengagement force, the maximum possible disengagement force resulting from the maximum load capacity of the switching module 1. The first coupling part 5 ″ simultaneously represents the coupling sleeve 5 ″ of the claw coupling 5, so that an additional coupling sleeve can be dispensed with. The coupling sleeve 5 'is, for example, rotatably mounted in the switching piston 11 by means of a roller bearing 12.

6 shows an example of the course of the disengagement force 14, 14 ', 14 "for

different angles of inclination a, ß, g depending on the acting torque. The straight line 14 shows the increase in the disengagement force 14 with increasing

Torque for a toothing 6 with the inclination angle a, the straight line 14 'shows the increase in the disengagement force 14' with increasing torque for a toothing with the inclination angle β and the straight line 14 '' shows the increase in the disengagement force 14 "with increasing torque for a toothing with the tilt angle g. As can be seen, the release force increases linearly with increasing torque. How can also be seen, the disengagement force is also dependent on the angle of inclination a, ß or Y, where the following applies, for example: a <ß <g. The greater the angle of inclination a, β, g, the greater the resulting disengagement force. The release force is proportional to the sine of the tilt angle a, ß, g. In order to avoid inadvertent opening of the closed claw clutch 5 under load, the switching piston 11 is designed in such a way that its maximum actuating force 11 ′ that can be applied is greater than a maximum possible disengagement force. The maximum actuating force 1 1 'that can be applied is shown in FIG. 5 as a straight line which is independent of the acting torque.

Bezuaszeichen

1 switching module

2 differential lock

3 shift rod

shift fork

5 claw coupling

5 ‘first coupling part, claw sleeve

5 “second coupling part

6 teeth

7, 7 'tooth flanks

8 axial axis

9 undercut

10 gear shaft

11 switching pistons, ring pistons

1 1 ‘force

12 rolling bearing

13 tooth gap

14, 14 ', 14 "release force

15 ball lock

a, ß, g tilt angle

Claims

claims

1. switching module (1) for a differential lock (2) or for an axle connection, comprising a dog clutch (5) with a toothing (6) and one

Shift piston (1 1) with a maximum actuating force (11 ') that can be applied, tooth gaps in the toothing (6) being designed to such an extent that the dog clutch (5) can be closed under load,

characterized in that tooth flanks (7, 7 ') of the toothing (6) one

Incline angles (a, ß, g) against an axial axis (8) of the dog clutch (5) in such a way that the dog clutch (5) experiences a disengagement force (14, 14 ', 14 ") under load and that the maximum actuating force (1 1 ') is larger than that

Release force (14, 14 ″, 14 “).

2. switching module (1) according to claim 1,

characterized in that the switching piston (1 1) is designed as an annular piston (1 1).

3. switching module (1) according to claim 2,

characterized in that a coupling sleeve (5 ') of the dog clutch (5) is rotatably mounted axially in the annular piston (1 1).

4. switching module (1) according to claim 3,

characterized in that the coupling sleeve (5 ') is rotatably mounted in the annular piston (11) by means of a roller bearing (12).

5. switching module (1) according to at least one of claims 1 to 4,

characterized in that the switching module (1) further comprises a switching cylinder which is designed to pressurize the switching piston (1 1).

6. switching module (1) according to claim 5,

characterized in that the switching module (1) further comprises an elastic return element which is designed to apply a force counteracting the pressure to the switching piston (1).

7. switching module (1) according to at least one of claims 1 to 6,

characterized in that the switching module (1) further comprises a rear piston stop.

8. differential lock (2) for locking a distribution function of the transfer case, the differential lock (2) being engageable and disengageable by means of a switching module (1),

characterized in that the switching module (1) is a switching module (1) according to at least one of claims 1 to 7.

9. transfer case with a differential lock (2),

characterized in that the differential lock (2) is a differential lock (2) according to claim 8.

10. Axis connection, wherein the axis connection can be switched on and off by means of a switching module (1),