Ramp actuator

Abstract

The invention relates to a ramp actuator, comprising a first annular actuator element (2), which has a plurality of first ramps (3) distributed around the circumference, and comprising a second annular actuator element (4), which is coaxial to the first annular actuator element and has a plurality of second ramps (5) distributed around the circumference, the second ramps lying opposite the first ramps (3). Balls (6) are provided between the actuator elements (2, 4), and the two actuator elements (2, 4) can be rotated reversibly with respect to one another. The balls (6) run onto the first and second ramps (3, 5) according to the direction of rotation and run off the first and second ramps (3, 5) such that the actuator elements (2, 4) can be moved axially relative to one another. The first ramps (3) or the second ramps (5) have a gradient which varies over the length of the ramps (3, 5), said gradient decreasing in the run-on direction of the balls (6).

Description

[0001] Ramp actuator

[0002] The invention relates to a ramp actuator comprising an annular first actuator element with several first ramps distributed around the circumference and a coaxially arranged annular second actuator element with several second ramps distributed around the circumference, which are opposite the first ramps, wherein balls are provided between the actuator elements, wherein the two actuator elements are reversibly rotatable relative to each other and the balls run onto and off the first and second ramps depending on the direction of rotation, so that the actuator elements are axially movable relative to each other.

[0003] A ramp actuator of this type serves as a linear actuating element, converting a rotational movement into a translational movement. One application is the use of the ramp actuator to operate a clutch device, such as the clutch of a hybrid module located between an internal combustion engine and a transmission. This device transmits torque from both an electric motor and the internal combustion engine to the transmission. Such a clutch device, typically located in a hybrid module, is usually called a knock-out clutch and can be axially compressed by the ramp actuator, which can also be referred to as a ball ramp actuator.In this process, a spring element, usually a disc spring, is deformed by building up an axial restoring force, which restoring force allows the coupling device to be opened again when the ramp actuator is relieved and the ramp actuator to be reset at the same time.

[0004] The ramp actuator itself comprises a first annular actuator element with several first ramps distributed around its circumference, and a second annular actuator element arranged coaxially with several second ramps also distributed around its circumference. The number of ramps on both actuator elements is the same. Balls are positioned between the actuator elements. When the two actuator elements are rotated relative to each other, the balls run onto the ramps when rotated in one direction and off them when rotated in the other. The rotation is initiated by a rotary drive coupled to one of the actuator elements, for example, an electric motor used to actuate the ramp actuator or the coupling device. This electric motor is coupled to the actuator element via an output element and, if necessary, an intermediate gear arrangement.When a torque is applied via the electric machine, the actuator element is rotated relative to the other, preferably positionally fixed, actuator element. Depending on the direction of rotation, the balls either run onto the ramps and into an end position, or they run off the balls from the end position. If the balls run onto the ramps, this results in an axial offset of the actuator elements relative to each other. One of the actuator elements is not only rotationally fixed but also axially fixed, while the other can rotate and is mounted for axial movement. This axially movable actuator element is coupled to a pressure element, such as a release bearing, which in turn is coupled to the clutch assembly. This pressure element is also moved axially with the axial movement of the actuator element in order to either compress or release the clutch assembly, depending on the direction of movement. The basic design of such a ramp actuator is known.

[0005] To open or close the clutch against the clutch-side spring element, depending on the clutch design, a corresponding torque must be applied via the electric motor, which should of course be as small and low-powered as possible. This torque works against the spring mechanism of the clutch assembly and rotates the rotatable actuator element, causing the balls to run onto the ramp and the axially movable actuator element to perform the axial stroke. As already described, the rotation can be increased or decreased via a gearbox.While the electric motor, and thus the actuator, briefly delivers a higher torque to rotate the actuator element and perform the axial stroke, causing the balls to run onto the ramps, resulting in rapid rotation and axial stroke, keeping the clutch open or closed—which typically occurs over a longer period—requires a correspondingly longer torque output. This means the electric motor must deliver a correspondingly high power output for a correspondingly long time, necessitating a correspondingly larger motor. However, this results in a larger electric motor, requiring more installation space and in higher costs.

[0006] The invention is based on the problem of specifying an improved ramp actuator.

[0007] To solve the problem, in a ramp actuator of the type mentioned at the outset, it is provided according to the invention that the first ramps or the second ramps have a gradient that varies over the length of the ramps, with the gradient decreasing in the direction of the balls' approach.

[0008] While in known ramp actuators, such as those described in DE 37 27 370 A1, the ramps all have a straight, rising running surface, thus exhibiting a constant gradient from beginning to end, the ramp actuator according to the invention is characterized by the fact that the first or second ramps have a gradient that varies over their length. The gradient profile is selected such that it decreases in the direction the balls are running onto the ramp. Thus, as the balls begin to run onto the ramp, the gradient is initially steeper, but decreases towards the end. This means that as the balls approach their final position on the ramps, which corresponds to the end of the axial stroke, the gradient is lower.This means that in the area of ​​the gentler gradient, and thus particularly at the end of the ramp path where the maximum axial stroke occurs and where the balls remain if the coupling device is to stay in the corresponding position permanently, a lower torque needs to be applied via the electric motor, and therefore less power is required to maintain the switching state. This, in turn, means that even a correspondingly low-power electric motor, which is capable of briefly providing a higher power output at the beginning of the ramp, is also able to hold the ramp actuator and thus the coupling device in the final position for extended periods, since only a lower power output and therefore a lower torque are required.

[0009] Although either only the first ramps or only the second ramps can have varying gradient profiles, it is advantageous for both the first and second ramps to have a gradient that varies along their length. This means that both the first and second ramps flatten out towards the end of the approach path, and thus both ramp profiles contribute to reducing the torque or power demanded by the electric motor.

[0010] The first and second ramps can have an identical profile, meaning that the gradient variation is identical on both the first and second ramps.

[0011] According to a first embodiment of the invention, each first ramp and / or each second ramp can have at least one linear first ramp section and a linear second ramp section adjoining it, both having different gradients. That is, two ramp sections with different gradients are provided one after the other, with the first ramp section, onto which the balls first run, being steeper, i.e., having a greater gradient, than the second ramp section leading to the end of the ramp. In principle, more than two ramp sections can also be provided, adjoining one another, with the gradient preferably decreasing continuously from ramp section to ramp section in the direction of travel.

[0012] If, for example, two ramp sections are provided, the angle of the first ramp section can be between 1.8° and 20°, and the angle of the second ramp section between 0° and 10°. Depending on the design of the ramp actuator, the gradients of the two ramp sections can therefore be varied in the corresponding intervals, whereby the gradient angle of the second ramp section, leading towards the exit, is always smaller than the angle of the first ramp section. If the angle of the second ramp section is 0°, this ramp section runs perpendicular to the axis of rotation, which means that ideally no torque, or for safety reasons only a very small amount, needs to be applied by the electric motor to maintain the assumed position.

[0013] According to a second variant, it is conceivable that each first ramp and / or each second ramp has a non-linear profile. In this design, the respective ramp profile is at least partially arc-shaped or curved. The profile can, for example, be convex, so that there is a steeper gradient at the beginning of the approach surface, which then decreases continuously towards the end.

[0014] Preferably, the gradient of the first and / or second ramps is designed such that balls that have completely reached the ramps automatically roll off again. The ramp actuator is therefore not self-locking, but rather allows the coupled coupling device to automatically reset itself via its integrated spring mechanism when no torque is applied by the electric motor. This means, for example, that it opens again, which also resets the ramp actuator, thus reversing the previously rotated actuator element and allowing the balls to roll off the ramps again. This design can be advantageous, not least for safety reasons, in the event that the electric motor loses power for any reason, so that in an emergency the coupling can automatically return to its unadjusted initial position, i.e., open.

[0015] It is advantageous if the ramps have a stop at least at the end viewed in the direction of travel. This ultimately limits the rotation angle of the rotatable actuator element and thus also the axial stroke.

[0016] The ramp actuator, as described, is to be coupled to the electric machine, i.e., a drive element. For this purpose, it expediently has a rotatable input element that is coupled to one of the actuator elements, in particular via several spring elements. The input element is, for example, a toothed disc that meshes with a drive pinion of the electric machine. The input element is connected to the rotatable actuator element, this mechanical connection being expediently realized via several spring elements, in particular leaf springs. These springs ensure, on the one hand, that the actuator element is driven in the circumferential direction, and on the other hand, generate a restoring force in the event of an axial displacement of the actuator element relative to the axially fixed input element. This restoring force assists in resetting the ramp actuator.Instead of leaf springs, other springs or elastomer elements can also be used to connect the input element, for example the toothed disc, to the actuator element.

[0017] In addition to the ramp actuator itself, the invention further relates to a hybrid module for arrangement between an internal combustion engine and a transmission, via which a torque from an electric machine and a torque from the internal combustion engine can be transmitted to a module output element that can be coupled to the transmission. This module comprises a clutch device for opening and closing a torque-transmitting coupling between the internal combustion engine and the module output element, as well as an electric machine for actuating an actuator for actuating the clutch device. This hybrid module is characterized in that the actuator includes a ramp actuator of the type described above.

[0018] Furthermore, the invention relates to a drive train of a motor vehicle, comprising an internal combustion engine and a transmission, between which a hybrid module of the aforementioned type is connected.

[0019] The invention is explained below with reference to exemplary embodiments and the drawings. The drawings are schematic representations and show:

[0020] Figure 1 shows a schematic representation of a ramp actuator according to the invention, Figure 2 shows a schematic representation of a first and second ramp with a gradient profile having two different linear ramp sections,

[0021] Figure 3 shows a schematic representation of the ramp actuator and a coupling device switched via it, with the ramp actuator in a starting position.

[0022] Figure 4 shows a schematic representation of the two ramps in this position,

[0023] Figure 5 shows a schematic representation of the ramp actuator and the circuits controlled by it.

[0024] Coupling device with the ramp actuator in the end position,

[0025] Figure 6 shows a schematic representation of the two ramps in this position,

[0026] Figure 7 shows a schematic representation of the force curve of a return mechanism.

[0027] clutch mechanism diaphragm spring,

[0028] Figure 8 shows a schematic representation of the gradient profile of a ramp with a non-linear slope.

[0029] Figure 9 shows a schematic representation of a hybrid module according to the invention in the mounting position between an internal combustion engine and a transmission, with an external electric machine.

[0030] Figure 10 shows a detailed view of the essential components of the hybrid module and the actuator, and

[0031] Figure 11 shows a schematic representation of the actuator arrangement relative to the gear arrangement. Figure 1 shows a schematic representation of a ramp actuator 1 according to the invention. This comprises an annular first actuator element 2, on which several first ramps 3 are provided distributed around its circumference, and a coaxially arranged annular second actuator element 4, on which an equal number of second ramps 5 are provided, also distributed around its circumference. Balls 6 are accommodated between the actuator elements 2 and 4, corresponding to the number of ramp pairs. When the two actuator elements 2 and 4 are rotated relative to each other, the balls run onto the ramps and cause the first actuator element 2, which is both rotatable and axially movable, to be axially adjusted relative to the second actuator element 4, which is fixed in position both rotationally and axially.The first actuator element 2 is connected to an input element 7, here a toothed disc, via several spring elements 8, in particular leaf springs, which are attached to the first actuator element 2 by rivet connections 9 and to the input element 7 by rivet connections 10. These spring elements 8 allow, on the one hand, that when the input element 7 rotates, the first actuator element 2 is also rotated, and on the other hand, the spring elements 8 allow an axial positioning movement of the first actuator element 2 relative to the axially fixed input element, while simultaneously generating a restoring force via the spring elements 8. The input element 7 is mounted on the second actuator element 4, which is rotationally and axially fixed as described, via an axial bearing 11. It has external teeth 12 that mesh with the external teeth 13 of a drive pinion 14, which is connected to, or rather rotated by, an electric machine 15, i.e., an electric motor.When the electric motor 15 is operated, as indicated by arrow P1, the drive pinion 14 rotates, and with it the input element 7, i.e., the toothed disc, which in turn leads to a rotation of the first actuator element 2. During this rotation, the balls 6 run onto the first and second ramps 3 and 5, since the first ramps 3 are necessarily also rotated relative to the fixed second ramps 5, thus changing their position. The running of the balls 6 inevitably results in an axial stroke movement of the first actuator element 2, which is coupled to a release bearing 16. It bears against one ring 17 of the release bearing 16, which is coupled via balls 18 to a second ring 19. This second ring 19 is in turn coupled to a pressure element connected to the clutch housing, or directly to the clutch assembly. This release bearing ultimately achieves the linear positioning movement of the ramp actuator 1 on the clutch device.

[0032] Figure 2 shows a schematic representation of a first ramp 3 and a second ramp 5, which are geometrically identical but arranged in reverse to each other. The ramp profile 20 is explained in more detail using the second ramp 5 as an example. Its gradient varies. It has a linear first ramp section 21 and a linear second ramp section 22, which, viewed in the direction of travel P2 of the ball 6, connect to each other but have different gradients. The running surface of the first ramp section 21 runs at an angle α1 to the base 23, while the running surface of the second ramp section 22 runs at a smaller angle α2 to the base 23. The gradient of the first ramp section 21 is greater than that of the second ramp section 22, at the end of which a stop 24 is provided that limits the travel and thus the maximum axial stroke.The two ramp sections 21 and 22 also have different lengths; the first ramp section 21, with its length x1, is slightly longer than the second ramp section 22, with its length x2. This profile, varying in its gradient, causes the ball 6, at the beginning of the rotational movement of the first ramp 3 relative to the ramp 5 (during which the ramp 3 is also moved in the direction of arrow P2), to initially run onto the first two ramp surfaces 21, which are correspondingly steep. This necessitates a correspondingly high torque, which is applied by the electric motor 15. Upon reaching the second ramp surfaces 22, the gradient changes, becoming shallower. As a result, while the axial stroke achieved during further running decreases, so does the required torque, meaning the electric motor has to deliver less power.Upon approaching the stops 24, the end position is reached. In this position, the ramp actuator 1, and thus also the associated coupling device, is held by the electric motor 15. Since the gradient in this ramp section 22 is correspondingly low, a reduced torque is required to permanently maintain the state, allowing the electric motor 15 to be designed with correspondingly low power consumption. Figure 3 shows a schematic representation of the ramp actuator according to the invention with an associated coupling device 25, which is, for example, integrated into a hybrid module. This coupling device is often also referred to as a knock-out coupling. The first actuator element 2 and the second actuator element 4 of the ramp actuator 1 are shown, with the second actuator element 4 being axially fixed against a support 26 as shown and not rotatable.The balls 6 are located between the two actuator elements 2 and 4. In this position, as shown in Figure 4, which depicts the two corresponding first and second ramps 3 and 5, the balls are not positioned on the ramps 3 and 5, or only at their very beginning. A coupling element 27 is connected via the release bearing 16. Unlike the coupling element 28, the coupling element 27 can be axially displaced, as indicated by arrow P3, while the coupling element 28 is axially fixed against an abutment 29. The coupling element 27 is spring-loaded by a disc spring 31, which is also mounted against an abutment 30. The coupling element 27 is movable against this disc spring 31, which thereby generates a restoring force.

[0033] When a torque is applied via the electric motor 15 and the input element 7 is rotated, the first actuator element 2 is rotated relative to the second actuator element 4. The balls 6 run onto the first and second ramps 5, as shown in Figure 6. This inevitably results in an axial stroke movement of the first actuator element 2, which is moved axially away from the second actuator element 4. The release bearing 16 is also moved in the direction of arrow P3, and together with it, the first clutch element 27 is also moved, compressing the disc spring 31. In this position, the clutch assembly 25, which was closed in the position shown in Figure 3, is now open. For example, an internal combustion engine coupled via the clutch assembly 25 is now disengaged.To maintain this state, as described above, only a relatively low torque and consequently relatively low power need to be supplied by the electric motor 15, since the balls 6 have run onto the second ramp sections 22, which have a relatively shallow gradient. This still provides a slight gradient, ensuring that in the event of a failure of the electric motor 15, i.e., when it no longer supplies torque, the disc spring 31 can reset the entire assembly, in conjunction with the restoring force from the also deformed spring elements 8, so that the coupling device 25 can automatically return to its initial position, i.e., be closed.

[0034] It is conceivable to incorporate the characteristic curve of the disc spring 31 into the design of the ramp profiles of ramps 3 and 5. Figure 7 shows an example of the force F of the disc spring (ordinate) along the path x (abscissa). In the example shown, it can be seen that the force of the disc spring 31 decreases from the installation position at point W1 until it reaches the end position at point W2, where the coupling device 25 is open. This means that as the coupling device 25 opens further, corresponding to the increasing contact of the balls 6 with the ramps 3 and 5, the force to be overcome by the disc spring 31 decreases, allowing the ramp profile to be adjusted accordingly.

[0035] Figure 8 shows an example of the profile of a first or second ramp 3, 5, which has a non-linear gradient. The ramp profile 20 is clearly not linear; it is rather concave. At the beginning of the ramp length, there is a first stop 32 against which the ball 6 rests, and at the end of the ramp length, the second stop 24, already described, against which the ball 6 (shown with dashed lines) runs. Thus, there is no abrupt change in gradient, but rather a continuously changing gradient that decreases towards the end of the ramp length. The ramp length is denoted here by x1, but it does not have any differentiable ramp segments.

[0036] Figures 9-11 show an embodiment of a hybrid module 33 according to the invention, which is mounted between an internal combustion engine 34 and a transmission 35. An external electric motor 36 is also arranged on the hybrid module 33. The task of the hybrid module 33 is, on the one hand, to continuously transmit the torque supplied by the electric motor 36 to the transmission 35, and, on the other hand, to engage the internal combustion engine 34 as needed, so that its torque is also transmitted to the transmission 35. Figure 9 shows a sectional view along line IX-IX and Figure 10 shows a sectional view along line XX in Figure 1.

[0037] For the continuous transmission of the torque of the electric machine 36, a gear arrangement 38 is provided in a housing 37 of the hybrid module 33. This arrangement comprises a first gear 39, which is coupled to an output of the electric machine 36 via an input element 40, for example, an input shaft. A second gear 41, which, for example, directly represents a module output element 42 and is coupled to an input 43 of the gearbox 35, meshes with the first gear 39. The torque of the electric machine 36 is transmitted directly via this gear arrangement 38.

[0038] To selectively engage the internal combustion engine 34, a clutch assembly 25 is provided, which is also commonly referred to as a knock-out clutch. Associated with it is a ramp actuator 1, i.e., a ball ramp release mechanism. When this is actuated, the clutch assembly 25 is closed, and the torque of the internal combustion engine 34, which is preferably coupled to the clutch assembly 25 via a torsional damper 44, is also transmitted via the closed clutch assembly 25 to the module output element 42 and via this to the input 43 of the transmission.

[0039] The electric motor 15 is used to actuate the ramp actuator 1. It consists of an actuator electric motor and an actuator gearbox. The torque of the actuator electric motor is transmitted to the reducing actuator gearbox. The actuator gearbox is, for example, a planetary gear or a Harmonic Drive gearbox and has a gear ratio of i = 1.2 <-> 120. As Figure 10 shows, an actuator output element is provided here, for example, in the form of a drive pinion 14, which meshes with the input element 7, i.e., the toothed disc, of the ramp actuator 1, so that a rotation of the drive pinion 14 leads to a rotation of the input element 7, thereby effecting the actuation of the ramp actuator 1 or the axial stroke. Figure 11 shows the first gear 7 and the second gear 9, each rotating about axes D1 and D2, respectively. The electric machine 15 is clearly arranged radially offset to the axis of rotation D2, as well as circumferentially offset to the axis of rotation D1.In the embodiment shown in Figure 11, the actuator 14 is arranged offset clockwise to D1, but it can also be positioned on the other side.

[0040] List of reference signs

[0041] Ramp actuator, actuator element, ramps, actuator element, ramps, ball

[0042] Input element, spring element, riveted connection, riveted connection, axial bearing, external toothing

[0043] External gear drive pinion electric machine

[0044] Release bearing ring balls ring

[0045] Ramp profile Ramp section Ramp section Base

[0046] Stop coupling device abutment coupling element coupling element abutment 30 abutment

[0047] 31 Belleville spring

[0048] 32 stops

[0049] 33 Hybrid module

[0050] 34 Internal combustion engine

[0051] 35 gearboxes

[0052] 36 Electric machine

[0053] 37 cases

[0054] 38 Gear arrangement

[0055] 39 gear

[0056] 40 Input element

[0057] 41 gear

[0058] 42 Module output element

[0059] Entrance 43

[0060] P1 Arrow

[0061] P2 Arrow

[0062] P3 Arrow a1 Angle a2 Angle x Path x1 Length x2 Length

Claims

Patent claims 1. Ramp actuator comprising an annular first actuator element (2) with several first ramps (3) distributed around its circumference and a coaxially arranged annular second actuator element (4) with several second ramps (5) distributed around its circumference, which are opposite the first ramps (3), wherein balls (6) are provided between the actuator elements (2, 4), wherein the two actuator elements (2, 4) are reversibly rotatable relative to each other and the balls (6) run onto and off the first and second ramps (3, 5) depending on the direction of rotation, so that the actuator elements (2, 4) are axially movable relative to each other, characterized in that the first ramps (3) or the second ramps (5) have a gradient that varies over the length of the ramps (3, 5), wherein the gradient decreases in the direction of travel of the balls (6).

2. Ramp actuator according to claim 1, characterized in that both the first ramps (3) and the second ramps (5) have a gradient that varies over the length of the ramps (3, 5).

3. Ramp actuator according to claim 2, characterized in that the first and the second ramps (3, 5) have an identical profile.

4. Ramp actuator according to one of the preceding claims, characterized in that each first ramp (3) and / or each second ramp (5) has at least one linear first ramp section (21) and a linear second ramp section (22) adjoining it, which have different gradients.

5. Ramp actuator according to claim 4, characterized in that the angle (cd ) of the first ramp section (21 ) is between 1.8°-20° and the angle (a2) of the second ramp section (22) is between 0°-10°.

6. Ramp actuator according to one of claims 1 to 3, characterized in that each first ramp (3) and / or each second ramp (5) has a non-linear profile.

7. Ramp actuator according to one of the preceding claims, characterized in that the gradient is such that balls (6) that have completely run onto the ramps (3, 5) automatically run off again.

8. Ramp actuator according to one of the preceding claims, characterized in that the ramps (3, 5) have a stop (24) at least at the end seen in the direction of approach.

9. Ramp actuator according to one of the preceding claims, characterized in that a rotatable input element (7) which can be coupled to a drive means (15) is provided and which is coupled to one of the actuator elements (2, 4), in particular via several spring elements (8).

10. Hybrid module for arrangement between an internal combustion engine (34) and a transmission (35), via which a torque of an electric machine (36) and a torque of the internal combustion engine (34) can be transmitted to a module output element (42) that can be coupled to the transmission (35), comprising a coupling device (25) for opening and closing a torque-transmitting coupling of the internal combustion engine (34) with the module output element (42) and an electric machine (15) for actuating an actuator for actuating the coupling device (25), characterized in that the actuator comprises a ramp actuator (1) according to one of the preceding claims.

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