Patent Application
20230279716
The invention relates to a spindle assembly for a spindle drive device according to the generic concept of claim 1.
To open and close doors, tailgates or hoods of a motor vehicle automatically and in a controlled manner, electric drives are used in combination with passive components such as, for example, gas pressure springs.
The electric drives often comprise spindle drive devices, which usually comprise an electric spindle drive by means of which the associated vehicle tailgate can be opened and/or closed.
A user of an associated vehicle therefore no longer needs to perform the opening and closing manually. They only need to send a command to open or close to the spindle drive assembly, which they can do, for example, via a radio remote control or via a switch located in the vehicle.
To enable a change in length of the spindle drive device, a spindle driven by a motor gear unit is rotated, which spindle engages in a spindle nut. The spindle nut itself is fixed in translation and rotation by a thrust tube.
To prevent the spindle nut from moving beyond the free end of the spindle, an end stop is usually provided at the free end of the spindle, which also serves as a guide element for the spindle in the thrust tube.
DE 10 2017 127 859 A1 shows a spindle drive device for a closure element of a motor vehicle, wherein an end stop in the form of a damping device is provided at the end of the spindle.
The damping device protects the motor gear unit used to drive the spindle from excessive loads. The damping element is configured as a sleeve-shaped plastic part that deforms plastically when a force is applied.
An end stop with a similar damping element is known from WO 2015 032 554 A1.
The known damping elements are plastically deformed upon impact with the spindle nut such that the impact energy is largely absorbed.
This impact situation does not, however, generally occur during normal operation of the drive device, but rather only in the cases of a misuse situation, during installation in the motor vehicle or a defect, wherein a plastic deformation of the damping element cannot for the most part be reversed, and the damping element should be replaced in the event of damage.
The configuration of the damping element arranged on the spindle is, in particular, a subject matter of the invention.
It is the task of the invention to improve the end stop of the spindle in a spindle assembly for a spindle drive device.
The task is solved by a spindle assembly and an end stop associated with the spindle assembly and having the features of claim 1.
Preferred configurations of the invention and further advantageous features are given in the subclaims.
The described spindle assembly for a spindle drive device comprises a thrust tube and a spindle nut, which is arranged on the thrust tube in a rotationally fixed manner, wherein the spindle nut can be brought into threaded engagement with a spindle of the spindle drive device and wherein an end stop for the spindle nut is arranged on the spindle.
According to the invention, the end stop comprises a damping element consisting of a stamped part which is hollow-cylindrical in shape and has spring-elastic properties. The end stop is preferably made from a stamped spring steel sheet and has the function of an elastic spring steel sleeve. The damping element can therefore also be referred to as a tubular spring.
In contrast to the damping elements known from the prior art, elastic deformation of the damping element occurs when a load is applied, such that the damping element does not undergo plastic deformation and is thus damaged or destroyed, but rather returns to its original shape on its own.
This stamped part is simple and inexpensive to manufacture and easy to install.
This results in a spring-elastic stamped end stop for the spindle drive, which has significant advantages over previously known damping elements with plastic deformation.
In a preferred configuration of the invention, the damping element is loosely arranged on the spindle at a defined position by means of a clearance fit, which is to say, it can be axially displaced on the spindle under load. With respect to its axial longitudinal extension in the vertical direction, the damping element or alternatively stamped part has a number of elongated—preferably horizontal-cutouts extending in the circumferential direction, which are arranged in a number of rows running in the circumferential direction of the stamped part and offset from one another. A series of solid state springs are hereby formed. Between the cutouts laid out in an offset manner, there are webs which transfer the force from one solid state spring to the other under load. The sum of these individually configured solid state springs gives the damping element its spring-elastic properties.
The multiple rows of cutouts in the cylindrically curved stamped part produce a spring-elastic element of the type of a spring sleeve or tubular spring, which exhibits springy properties similar to multiple disc springs stacked on one another or to bending springs having the same effect.
The cutouts of the stamped part preferably have a stress-optimized dumbbell-shaped or bone-shaped configuration.
Such a bone-shaped cutout preferably consists of two horizontally opposed semicircular arches punched out at intervals in the sheet material, the boundary sides of which are connected by a punched-out center area. The center area is indented in the shape of a bone because its opposing edge sides have a smaller distance between one another than the radius of the semicircular arches at the ends. This results in the characteristic bone shape of the cutouts. When a vertically directed force vector acts on the spring structure of the damping element, the sheet metal structures forming the center area of the cutouts each act as a bending spring inasmuch as the center area of the cutout undergoes elastic deformation.
The bone-shaped configuration of the cutouts punched out of the spring steel sheet has the advantage that a large plurality of bending springs distributed horizontally around the circumference are formed in the slotted spring sleeve and stacked on top of one another in a vertical direction. This results in a symmetrical bending structure without the risk of canting of the damping element and asymmetrical loading.
For further protection against canting, it may be provided in a second embodiment of the invention that the sleeve-shaped, slotted damping element respectively has a curled rim at its end faces which increases the diameter. The curled rim is formed from the material of the spring steel sheet and is beveled at an angle of about 90 degrees to the longitudinal center axis of the damping element. This eliminates the need for an enlarged-diameter washer adjacent to the end faces of the damping element, which is provided in the first embodiment for symmetrical force application to the slotted sleeve body.
Both embodiments provide that the longitudinal sides of the spring steel sheet joining to form a sleeve form a gap extending in the vertical direction. In this embodiment, the longitudinal sides can only touch, but are not connected to each other.
In a second configuration of such a vertical gap, it may be provided to provide vertically spaced spot-welded joints between the opposing longitudinal sides of the spring steel sheet.
In a third configuration, it may be provided to span the longitudinally extending gap between the two opposite ends of the spring steel sheet. In this case, the damping element is configured as a winding body and preferably comprises at least two mutually overlapping windings, namely an inner winding and an outer winding that covers the inner winding. The winding structure is preferably configured in such a way that the inner longitudinal side of the inner winding is opposite the outer longitudinal side of the outer winding, so that when a vertical force is applied to the sleeve-shaped spring body, the result is a uniform deformation of all the bending springs formed by the edge sides of the cutouts.
Finally, in a fourth configuration, with regard to the formation of the vertical gap, it can be provided that a plurality of tab connections spanning the gap can be provided between the opposing vertical longitudinal sides of the sheet metal strip.
With regard to the configuration of the vertical longitudinal gap, the four embodiments described above can be combined in any desired set-up, either individually or as a plurality combined with one another.
The end is closed by a thrust washer at the end of the damping element facing the spindle motor, which thrust washer is also movably arranged on the spindle and against which the spindle nut may optionally abut.
At the other end of the damping element there is a bearing element, which rests on the inner circumference of the thrust tube.
The entire end stop assembly comprises the thrust washer, the damping element and the bearing element and is fixed to the spindle by a securing disk.
The spindle assembly according to the invention is part of a spindle drive device, such as may be used to move doors, tailgates or hoods of a motor vehicle.
A plurality of embodiment examples of the invention are elucidated in more detail below with reference to the drawings. In this connection, further features and advantages of the invention will become apparent.
The spindle drive device 10 comprises a spindle housing 12, which extends along a spindle axis 14, and a first end piece 16a, which is, for example, attached to the vehicle body, and a second end piece 16b, which is connected to the vehicle tailgate to be actuated.
A motor gear unit 18 and a spindle unit 26 are arranged in the spindle housing 12.
In the embodiment shown, the motor gear unit 18 is mounted non-rotatably in the spindle housing 12 by means of two bearing elements 22a, 22b.
The spindle unit 20 comprises a guide tube 24 in which a spindle 26 is mounted. At its end facing the motor gear unit 18, the spindle 26 is preferably rotatably mounted in the guide tube 24 by means of a roller bearing 28.
In the embodiment shown, the guide tube 24 is fastened to the spindle housing 12, for example, glued or welded to the spindle housing.
A thrust tube 30 is arranged between the guide tube 24 and the spindle 26, which thrust tube is coupled to the spindle 26 by means of a spindle nut 32 which is arranged axially and rotationally fixed in the thrust tube 30.
The free end of the spindle 26 is rotatably mounted and axially guided in the thrust tube 30 by means of a bearing assembly 33. The bearing assembly 33 further serves as an end stop for the spindle nut 32, with which an axial movement of the spindle nut 32 on the spindle 26 is limited so that the spindle nut 32 cannot move beyond the free end of the spindle 26.
The bearing assembly 33 preferably comprises a bearing element 34 and an elastically deformable damping element 36, which is arranged between a thrust washer 38 facing the spindle nut 32 and a securing disk 40 and are arranged on the spindle 26.
The motor gear unit 18 comprises a drive motor 42 with a motor shaft 44, which drives a gear shaft 48 via a Oldham-type coupling, a ring gear 50 is provided on the output via an epicyclic gearing 46, which is rotationally coupled to the spindle 26 via a coupling 52. The ring gear 50 is rotatably mounted in the spindle housing 12 or in a gear housing not described in more detail. The spindle nut 32 is fastened to one end of the thrust tube 30. The spindle nut 32 is preferably made of plastic and is connected to the metal thrust tube 30 in an axially and rotationally fixed manner.
The other end of the thrust tube 30 is connected to a housing tube 54 by means of an end piece 16h.
When the spindle 26 is rotated by the motor gear unit 18, the spindle nut 32 and the thrust tube 30 connected thereto perform a translational movement along the spindle 26. In so doing, the thrust tube 30 and the associated housing tube 54 move telescopically relative to the spindle housing 12 to move the vehicle tailgate from a first position to a second position.
A compression spring 56 is arranged within the housing tube 54 in order to power assist the spindle drive 20 in extending the housing tube 54.
The compression spring 56 surrounds the guide tube 24 and is supported at one end on a stop on the guide tube 24 and at the other end on the housing tube 54.
At its rear end, the spindle 26 is rotatably mounted in the guide tube 24 by means of a roller bearing 28 and is driven in rotation by the motor gear unit 18 (
The spindle nut 32 engages in the thread of the spindle 26 and is firmly connected to the thrust tube 30.
When the spindle 26 rotates, the spindle nut 32 moves linearly, guided by the guide tube 24 along the spindle axis 14, such that the thrust tube 30 also moves linearly relative to the guide tube 24.
A guide sleeve 58 is arranged at the front end of the guide tube 24 to guide the thrust tube 30. Moreover, the guide sleeve 58 seals the thrust tube 30 against environmental influences or contamination.
An end stop with a damping element 6 is provided at the front free end of the spindle 26.
The end stop is fixed firmly to the spindle 26 by means of the securing disk 40.
A bearing element 34 rests against the securing disk 40, which bearing element slides against the inner circumferential surface of the thrust tube 30. Upon rotation of the spindle 26 and the resulting translational movement of the thrust tube 30, the thrust tube 30 slides along the bearing member 34.
The damping element 36 is in contact with the bearing element 34, which damping element is limited at the other end by a thrust washer 38.
The damping element 36 and the thrust washer 38 are arranged loosely on the spindle 26 and are fixed on the left side of the drawing only by the bearing element 34 and the securing disk 40 which is fastened to the end of the spindle 26.
When the spindle 26 rotates, the spindle nut 32 moves either to the left or to the right along the spindle 26 until it meets the thrust washer 38 with its end face 32a at the left-hand end of the spindle 26 and the rotation of the spindle is electronically switched off.
In this state, the end face 32a of the spindle nut 32 is thus in contact with the thrust washer 38 of the end stop and axial forces acting on the thrust tube 30, for example, caused by forces introduced by a user, can be absorbed by the damping element 36. Another overload event absorbed by the damping element 36 is when, for example, the spindle nut hits the end stop at too high a speed or with too high a force.
It can be seen here that the damping element 36 preferably consists of a cylindrically curved stamped part 60, which has a plurality of cutouts 62 arranged offset from one another in the circumferential direction. Webs remain between the cutouts, which webs thus transmit forces occurring in the axial direction, which is to say, in the direction of the spindle axis 14, and the cutouts are elastically deformable.
As shown in particular by
These cutouts 62 preferably have a stress-optimized bone-shaped or dumbbell-shaped design.
The flat stamped part 60 is rolled along its longitudinal ides to forma hollowcylindrical damping element 36 as shown in
Preferably, the edges of the rolled stamped part 60 that are contiguous with one another are not firmly joined to each other, but rather there remains a gap 64. Alternatively, the edges that are contiguous with one another can be joined to each other by means of, for example, (laser) welding. The elongated cutouts 62 extend with their longer side in the circumferential direction of the damping element 36. A plurality of rows of cutouts 62 arranged one above the other along the longitudinal center axis 66 are provided, wherein the cutouts 62 of each row are arranged offset with respect to the cutouts 62 of the adjacent rows. Moreover, it is known that the stamped layers can be wound one on top of the other to further increase the spring forces that can be imaged in small installation spaces.
The damping element 36 has spring-elastic properties due to the plurality of cutouts 62 arranged offset from one another since the webs between the cutouts 62 can deform elastically when axial force is applied to the damping element 36. This is illustrated in
In contrast to the prior art, where a plastically deformable body was used as the damping element, it is now proposed according to the invention to use a spring-elastic damping element 36 such that, in the event of an overload event, the load forces that occur are elastically absorbed and the damping element returns substantially undamaged to its original shape after the overload event.
In a load event, the end stop or alternatively the damping element can absorb forces, for example, of 300-1500 newtons or more or alternatively energies in the order of 20-150 joules. The spring force of the damping element 36 can be individualized, for example, by means of the choice of material and the number of cutouts 62.
The elastic damping element 36 thus prevents that these extraordinary forces affect the gear and ultimately the drive motor and damage the same.
In the illustrated embodiment example, the spindle 26 may, for example, have a diameter of about 8 millimeters, whereas the damping element 36 has an inner diameter of, for example, about 8.1 millimeters and an axial length of, for example, about 10 to 30 millimeters. The thickness of the stamped spring steel sheet is preferably in the range of 0.3 to 1 millimeter, wherein a thickness of 0.5 millimeter is particularly preferred.
The spring action of the damping element 36 or alternatively the spring force is also given by the diameter of the damping element 36, the axial length of the damping element 36 and the size and shape as well as the number of cutouts 62 and wound layers.
In
This results in the characteristic bone shape.
In this example, the vertical gap 64 is shown open. However, the invention is not limited to this. Various embodiments have been shown in the general description, by which means the gap 64 can be closed or spanned. The means for spanning the gap 64 described in the general part of the description are applicable to all embodiments of the invention.
In this regard,
The lobe-shaped connection tabs 79 engage with a positive fit n associated lobe-shaped connection cutouts 80 on the part lying opposite. Such a positive mechanical fit connection is also known in cardboard materials which may be connected to each other as pieces of a puzzle. Such a tab structure is an additional safeguard against uneven bulging or spreading of the spring sleeve in a radial direction when subjected to a compressive vertical force. It is understood that the tab structure is applicable to any of the above-described embodiment examples of a damping element 36, 36a,36b.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2022 104 079.8 | Feb 2022 | DE | national |
