WO2009065686A1

WO2009065686A1 - Load shifting element

Info

Publication number: WO2009065686A1
Application number: PCT/EP2008/064230
Authority: WO
Inventors: Matthias Reisch; Gerhard Gumpoltsberger; Bernard Hunold
Original assignee: Zf Friedrichshafen Ag
Priority date: 2007-11-23
Filing date: 2008-10-22
Publication date: 2009-05-28
Also published as: DE102007047852A1

Abstract

The invention relates to a frictionally configured load shifting element, comprising a lamella packet (1), wherein at least two pistons (2, 5) are provided for the activation or application of force onto the lamella packet (1), which are disposed at a radial offset in the same piston chamber (7), and are held in the initial position by means of spring force, and can be returned thereto, wherein a pressure is defined for each of the at least two pistons (2, 5) as a function of the piston surface and/or of the spring layout, from which point the piston (2, 5) moves.

Description

Load switching element

The present invention relates to a load switching element according to the preamble of patent claim 1.

Power shift elements are usually used in automatic transmissions, for example in automatic transmissions in planetary design.

Planetary-type automatic transmissions include planetary gear sets and load shifting elements designed as frictionally engaged multi-plate clutches and brakes for shifting the planetary gear sets, wherein the shifting elements are as a rule hydraulically actuated by means of pistons. The dimensioning of the switching elements, in particular with respect to the diameter and the number of lamellae and the piston depends on the maximum torque to be transmitted in the various gears of the transmission.

Especially with very large torques to be transmitted on the one hand very large diameter and a large number of fins are needed. On the one hand, this is very unfavorable with regard to the drag torques of the shift elements occurring in those gears in which these are not engaged. On the other hand, the piston forces generated by oil pressure and piston surface must be very large, which proves to be unfavorable with regard to the pressure resolution or the controllability of different friction torques and / or the filling speed of the piston chambers.

In some known planetary gearboxes, such as the transmission according to EP 0 434 525 B1 or US 4,070,927 A, a switching element is provided which is actuated only in the first forward gear and in reverse gear and which, especially in reverse, a significantly higher torque must support as in the first forward. In the transmission according to EP 0 434 525 B1, this function is taken over by the brake D.

From the prior art it is known to control a piston of a load switching element by two separately controllable pressure chambers, which act either against each other or with each other. In a disadvantageous manner, the additional piston chamber and the associated additional processing, the additional oil supply and the additional control result in a significant additional effort compared to a conventional single-piston solution.

From the not yet published DE 10 2007036100 the Applicant shows a load switching element, which has both a frictional and a positive mode of action. The known power shift element comprises a frictional and a form-locking switching element, which are preferably connected in series and are operable for closing the switching element by an actuator in this order. In this case, an axially movable element (for example a piston) is displaced with a force, which presses via a transmission element both on a disk set of a frictionally engaged switching element and on a displaceable jaw element.

Furthermore, from the not yet published DE 10 2007036097 of the Applicant another load switching element is known, which has both a frictional and a positive mode of action. The known power shift element comprises a frictional and a form-locking switching element which are connected in parallel and are operable to close the switching element of an actuator in the order frictional switching element, form-locking switching element. According to DE 10 2007036097, the friction-locked shifting element comprises a disk pack, the form-fitting shifting element having a claw assembly comprising an axially displaceable claw element guided in the housing of the shifting element. In addition, a spring element is provided, which is on the one hand with an actuator, which is preferably designed as a hydraulically operated piston and on the other hand with the end plate of the plate pack and with the jaw member in operative connection.

Here, the frictional and the positive switching element by means of a piston or an actuator via a spring element are actuated such that first the frictional switching element for generating a friction torque (and also for synchronization) and from a defined piston or Aktuatorkraft the positive switching element is actuated whereby the jaw member is engaged in a corresponding dog teeth of a plate carrier of the plate pack, so that a positive connection is established.

The present invention has for its object to provide a load switching element, which can be small in size, is suitable for transmitting high torques, in a specific work area with lower forces can be controlled and in the open state has lower drag torques than those of the prior art known load switching elements. Furthermore, the switching element according to the invention should open at signal or power interruption, so that an existing safety concept in the transmission can remain unchanged.

This object is achieved by the features of claim 1. Further advantages and advantageous embodiments will become apparent from the dependent claims. Accordingly, a designed as a frictional shift element load switching element is proposed, comprising a disk set, wherein for actuation or loading of the disk set with force at least two pistons are provided, which are arranged radially offset in the same piston chamber. These pistons are held by spring force in the initial position and returned to this, wherein for each of the at least two pistons in dependence on the piston surface and / or the spring design, a pressure is defined, from which the piston moves.

The frictional switching element may in this case be designed as a multi-plate clutch, multi-disc brake, as a cone clutch, etc.

According to the invention, an axially displaceable seal is arranged between each two radially adjacent pistons, whereby the pistons are sealed to each other, so that is sealed by the movable sealing point of the pressure chamber even with axial movement of one or both pistons against the environment; Accordingly, the at least two pistons are actuated with the same pressure medium, for example with oil, air, water etc. Alternatively or in addition to the axially displaceable seal, in the event that two pistons are provided, if the order of movement of the pistons when pressurized is that only at higher pressure movable piston have a sealing ring for sealing against the other piston.

Furthermore, both pistons are held by spring force in the starting position, wherein the spring force is also used to return the piston according to the invention. Preferably, a separate spring is provided for each piston; Alternatively, it can be provided that acts on the at least two pistons a single spring via a common abutment. The springs may be formed, for example, as disc springs with or without slotting and with any linear or non-linear characteristic or as coil springs, wherein any other mechanical spring design can be used as a spring.

According to the invention, the springs and / or the piston surfaces are coordinated so that one of the at least two pistons from a first pressure, preferably from the application pressure is moved and applies to the disk set, the second piston only at a (clearly ) moves higher pressure and also applies to the disk pack to exert an additional force on the disk pack.

In the event that more than two pistons are provided, it is provided that each additional piston by means of the spring design and the piston surface, a pressure is assigned, from which the piston moves, wherein the piston associated pressures have different values. In this way, the characteristic of the switching element can meet any requirements.

According to an advantageous development of the invention, the first pressure range, in which only the first piston acts, is used to control / regulate the friction torque in the slip state of the frictional engagement element during a drive, engage a gear or during a gear change or to set a defined slip for vibration decoupling within a corridor. The second pressure range, in which the second piston acts in addition, on the other hand serves to safely transmit an applied torque on the frictional switching element without slip within an inserted gear.

Advantageously, in the switching element according to the invention, the fail-safe principle, as in switching elements according to the prior art maintained so that when signal or power interruption, the switching element opens, whereby an existing safety concept in the transmission can remain unchanged.

The invention will be explained in more detail below with reference to the accompanying figures by way of example. Show it:

Figure 1: A schematic sectional view of an advantageous embodiment of the invention in the open state;

Figure 2 is a schematic sectional view of the embodiment of the invention shown in Figure 1 in a state in which the first piston is applied;

Figure 3 is a schematic sectional view of the embodiment of the invention shown in Figure 1 in a state in which the first and the second piston are applied; and

Figure 4: A pressure-force diagram illustrating an exemplary pressure-force curve of a switching element according to the invention.

Referring to Figure 1, the load switching element according to the invention as a multi-disc brake, comprising a disk set 1 is formed. As can be seen from the figure, two pistons 2, 5 are provided for actuating or for acting on the disk set 1 with force, which pistons 2, 5 are arranged radially offset in the same piston chamber 7. Between the piston 2, 5, an axially displaceable seal 4 is preferably arranged, whereby the pistons 2, 5 are sealed to each other. By the seal 4 of the common pressure chamber 7 is sealed even with axial movement of one or both pistons 2, 5 against the environment. In FIG. 1, G denotes a housing.

In the example shown in Figure 1, each piston 2, 5 associated with a spring 3 and 6, which serves to hold the respective piston in the starting position and to the provision thereof.

Preferably, the springs 3, 6 and / or the piston surfaces of the pistons 2, 5 are coordinated so that a piston is moved from the contact pressure, and applies to the disk set 1, so that this for controlling the friction torque in the slip state of frictionally engaged switching element is used wherein the second piston moves only at a higher pressure and also applies to the disk set, which is used for safe transfer of an applied torque on the frictional switching element without slippage.

According to the invention, the following exemplary switching sequence can be realized:

In a first step, the common piston chamber 7 is filled and the first piston 2 is applied against the force of the spring 3 to the disk set 1. Subsequently, the pressure in the piston chamber 7 is increased, whereby a friction torque is generated in the disk set by the piston 2. Subsequently, the circuit can be carried out, wherein modulation of the pressure, a control / regulation of the friction torque in the disk set is possible.

After completion of the circuit, the pressure can be increased to a first holding pressure, wherein the second piston is not moved, since the Holding pressure is below the pressure at which the second piston 5 can be moved against the force of the spring 6.

According to the invention, the piston pressure can be further increased in defined gears and with a required holding function, whereby the piston 5 is applied and a higher torque can be supported.

In Fig. 2, the power switching element shown in Fig. 1 is shown in a state in which the piston 2 is applied, and in Fig. 3, the switching element shown in Figs. 1 and 2 is shown in a state in which both pistons 2, 5 are applied ,

4 shows an exemplary pressure-force curve of a switching element according to the invention is shown. In this case, only the first piston 2 acts in the first region A and generates a force F corresponding to the piston surfaces on the disk set 1. In a second region, which is recognizable as a function of the pressure P on the basis of the buckling, the second piston 5 also commences accordingly its surface to generate an additional force F on the disk set. The first area A can advantageously serve the slip control and the second area B of the secure torque transmission or torque support.

The power shift element according to the invention can be used in any automatic transmission systems, for example in planetary gears, Vorgelegelastschaltgetriebe, dual-clutch transmissions or continuously variable transmissions. Advantageously, the load switch element may be employed in the V / R group of stepless wrap-around lifts and in a range of multi-range split power friction gearboxes, continuously variable hydrostatic transmissions, or multi-range electric power split transmissions. Of course, any structural design, in particular any spatial arrangement of the components of the switching element according to the invention per se and to one another and as far as technically feasible, within the scope of the present claims, without affecting the function of the switching element, as defined in the claims, also if these training are not explicitly shown in the figures or in the description.

REFERENCE CHARACTERS

1 disc pack

2 pistons

3 spring

4 seal

5 pistons

6 spring

7 piston chamber

Claims

claims

1. As a frictional shift element designed load switching element, comprising a disk set (1), characterized in that for actuating or loading of the disk set (1) by force at least two pistons (2, 5) are provided which radially offset in the same piston chamber (7 are arranged and held by spring force in the starting position and are reset in this, wherein for each of the at least two pistons (2, 5) in dependence on the piston surface and / or the spring design, a pressure is defined, from which the piston (2 , 5) moves.

2. Powershift element according to claim 1, characterized g e k e n n - characterized in that between two radially adjacent pistons (2, 5) an axially displaceable seal (4) is arranged, whereby the pistons (2, 5) are sealed to each other.

3. Powershift element according to claim 1 or 2, characterized marked - characterized in that in the event that two pistons (2, 5) are provided when the order of movement of the piston (2, 5) is set when pressurized, the only at Higher pressure movable piston (5) has a sealing ring (4) for sealing against the other piston (2).

4. Load switching element according to one of the preceding claims, characterized in that for each piston (2, 5) a separate spring (3, 6) is provided.

5. Powershift element according to one of the preceding claims 1 to 4, characterized in that a single spring is provided which acts on the at least two pistons (2, 5) via a common abutment.

6. Powershift element according to claim 4 or 5, characterized in that the springs (3, 6) are designed as disc springs with or without slotting and with any linear or non-linear characteristic or as spiral springs.

7. Power shift element according to one of the preceding claims, characterized in that the springs (3, 6) and / or the piston surfaces are coordinated so that one of the at least two pistons (2, 5) from a first pressure or from the Applying pressure is moved and applies to the disk set, wherein the second piston (5) moves only at a higher pressure and also applies to the disk set (1) to exert an additional force on the disk set (1).

8. Powershift element according to claim 7, characterized - characterized in that the first pressure range (A) in which only the first piston (2) acts to control / regulate the friction torque in the slip state of the frictional switching element during a journey, an engagement of a gear or a gear change or for setting a defined slip for vibration decoupling within a gear serves and that the second pressure range (B), in which the second piston (5) additionally acts, the safe transmission of an applied torque on the frictional engagement element without slippage within a Inlaid Ganges serves.

9. Power shift element according to one of the preceding claims, characterized in that the frictional engagement element is designed here as a multi-plate clutch, multi-disc brake or as a cone clutch.

10. Load switching element according to one of the preceding claims, characterized in that the at least two pistons (2) with oil, air or water can be actuated.