Electric motor drive unit for automotive applications

Abstract

The subject of the invention is an electric motor drive unit for automotive applications, equipped with an electric motor (4) having an output shaft (5) of substantially circular cross section and a drive element (6) mounted on the output shaft (5) and preferably made of plastic. The output shaft (5) engages in a receiving hole (9) of the drive element (6) which defines at least one ventilation hole (10). According to the invention, the output shaft (5) in one variant has, at least in the engagement area (E) of at least the receiving hole (9), two axially extending ridges (11) spaced apart from one another. A projection (13) of the drive element (6) engages between the ridges (11) and is rotationally coupled. Furthermore, the two ridges (11) define a ventilation hole (10) on their outer edge.

Description

[Technical Field]

[0001]

[0001] The present invention relates to an electric motor drive unit for automotive applications, the drive unit comprising an electric motor having an output shaft of substantially circular cross section, and further comprising a drive element mounted on the output shaft and preferably made of plastic, for example as a component of a gearbox, the output shaft engaging a receiving hole in the drive element and defining at least one ventilation hole.

[0002]

[0002] Such electric motor drive units for automotive applications are used, for example, but not exclusively, as actuators in or on vehicle locks, for adjusting vehicle seats, headlights, mirrors, or for adjusting associated window adjusters. The electric motors of such electric drive units are therefore typically operated with low DC voltages of 12 V, 24 V, or 48 V. To realize and convert a power-consuming actuation movement, the rotational movement of the electric motor's high-speed output shaft is converted with the aid of a gearbox, which is usually provided and connected downstream and to which a drive element usually belongs. The drive element itself can be, for example, a worm, which, together with a worm wheel, defines the aforementioned gearbox. Such worm gears are generally known in the context of automotive applications; reference is made, by way of example only, to DE 10 2009 036 834 A1 or 103 60 419 A1.

[0003]

[0003] Since relatively high forces are partially transmitted by the gearbox or the drive element, the connection between the output shaft and the receiving bore of the drive element (made of plastic) is particularly important. In fact, an output shaft with a D-shaped cross section has proven advantageous here. Such an embodiment is also called a D-cut, as described in particular in DE 10 2013 010 461 A1. In this location, the output shaft is equipped with at least one recess in the form of a groove. A drive element in the form of a worm or worm wheel with a protrusion engages in the groove, creating a closure.

[0004]

[0004] The groove extends parallel to the rotation axis of the output shaft. Typically, three parallel grooves are realized on the output shaft. The worm wheel or worm as a plastic driving element engages with the grooves with the help of three protrusions. In this way, if the worm or worm wheel is made of plastic, it is also possible to transmit higher forces overall. This is also intended to prevent the output shaft from peeling into the plastic driving element or worm wheel during operation.

[0005] In the prior art described in JP 2005-265169 A, an electric drive unit is used in connection with a CD player mounted inside a vehicle. Not only is a perfect connection between the metal output shaft and the plastic worm provided at this location, but ventilation holes are also provided to absorb temperature-related deformation of the worm or worm wheel. In this way, deformation of the plastic drive element or screw in the engagement area can be reliably prevented. This has been proven in principle.

[0006] However, the prior art allows for further improvements. For example, since the ventilation holes in the molded teachings are relatively small, deformation of the drive element or the plastic screw is still possible during operation without any change. Furthermore, in known teachings, the connection between the output shaft and the drive element is realized by an interference fit. Under certain circumstances, such an interference fit can shear under high torque loads, or the output shaft can "peel" within the drive element in the engagement area, as already described in DE 102013010461 A1. The present invention as a whole seeks to improve upon this.

[0007] overview

[0008]

[0007] The present invention is based on the technical problem of further developing an electric motor drive unit for such automotive applications so that a completely torsionally rigid connection is provided without any risk of mechanical damage and at the same time any temperature effects occurring during operation are completely controlled.

[0009]

[0008] In order to solve this technical problem, the present invention proposes that in a first variant of a typical electric motor drive unit for automotive applications, the output shaft has, at least in the engagement area of ​​the receiving hole, two spaced, axially extending ridges with a chord-shaped cross-section, between which protrusions of the drive element engage for rotational coupling, and each of these protrusions defines or delimits an air hole at its outer edge.

[0010]

[0009] Therefore, in the context of the present invention, a special design of the output shaft is utilized, at least in the engagement region of the receiving bore of the drive element. The drive element is generally a worm or worm wheel, similar to the embodiment described and shown in DE 10 2013 010 461 A1. Of course, other embodiments of the drive element are also possible and are in accordance with the present invention. The drive element is typically made of plastic, but may also be made of metal.

[0011] However, the two spaced apart, axially extending ridges of the output shaft, realized at least in the engagement region of the receiving bore, are decisive in the first case because they extend chord-like, i.e., along a circular chord of the output shaft, which has a substantially circular cross section. This results in two ridges, each extending along a circular chord, spaced apart from one another and forming a receptacle between them, into which the protrusion of the drive element engages for rotational coupling. The two ridges can extend at an angle to one another. However, it is usually observed that the two ridges extend parallel to one another.

[0012]

[0011] Furthermore, it has been proven useful in this context if the two ridges extend axially at equal distances from the center of the output shaft, which has a substantially circular cross section. The chordal extension of the ridges is further manifested by the fact that the ridges terminate at a tip around the circumference of the output shaft, which has a substantially circular cross section. On the foot side, the two ridges can be connected by an arc. As a result, the two ridges, together with the arc, form a compound U-shaped bridge.

[0013]

[0012] Here, a protrusion on the drive element engages with a U-shaped protuberance of the output shaft in the engagement area of ​​the receiving bore. Typically, this is done by friction locking to achieve a rotating ring, but usually also by force and form closure. The protrusion therefore has a shape complementary to the U-shaped protuberance or receptacle formed therein, resulting in a U-shaped protuberance. In this way, a particularly secure rotational connection is provided between, on the one hand, the U-shaped protuberance on the drive element and, on the other hand, the U-shaped design of the output shaft in the receiving area.

[0014]

[0013] Furthermore, ventilation holes are defined in the outer edges of each of the two protuberances or U-shaped legs of the U-shaped bridge in this manner, and they are necessarily defined. These ventilation holes are set substantially automatically, from the outer edge of each protuberance to the inner edge of the receiving hole in the engagement area that receives the output shaft or the axially extending U-shaped protuberance. These two ventilation holes formed on the outer edges of the protuberances are generally designed to have a circular cross section. Furthermore, the two ventilation holes usually have the same cross section size. In addition, the ventilation holes are regularly arranged in mirror symmetry with respect to an axis passing through the center of the output shaft, and the output shaft has a substantially circular cross section.

[0015] The fact that the ventilation holes each start at the edge of the U-shaped ridge or its two U-shaped legs means that any temperature-related changes in the diameter of the receiving hole can be easily accommodated and compensated for. This also prevents possible cracks on the inside of the plastic drive element. Shearing and delamination of the output shaft into the receiving hole are also avoided. As a result, the electric drive unit according to the invention has excellent functionality over its entire lifespan, even under heavy loads, and a long service life.

[0016]

[0015] In another second variant of the invention, the same ventilation holes are also observed. This provides that in a typical drive unit, the output shaft has a D-shaped extension with ventilation holes in each case on the outer wall, at least in the engagement area of ​​the receiving hole. The ventilation holes can be of the same design as before and offer the same advantages.

[0017]

[0016] In practice, thermoplastic materials such as PMMA (polymethyl methacrylate), PA (polyamide), PBT (polybutylene terephthalate), POM (polyoxymethylene) or PC (polycarbonate) are typically used to realize the drive elements or screws typically used here. Such plastics are particularly easy to process and have sufficient hardness for power transmission in connection with gearboxes constructed from them or when the worm typically realized meshes with the associated worm wheel. The use of polyamide (PA), namely the special homopolyamide PA 66, has proven particularly advantageous here.

[0018] The present invention also provides a vehicle lock, in particular a vehicle door lock, advantageously equipped with an electric drive unit of the initially described design. In this connection, the drive unit can be used to realize and implement individual function positions, such as "locked" or "anti-theft." In addition, such electric drive units can be used and deployed as pulling devices connected to vehicle locks. They can also be used and applied as lock drives connected to lock actuators in charging equipment for electric or hybrid vehicles.

[0019] In all these locations, functional actuation is provided and temperature-related effects can be particularly well controlled, so that large forces can also be transmitted, which is an essential advantage. [Brief explanation of the drawings]

[0020]

[0019] The invention will now be explained in more detail with reference to the drawings, which show only one exemplary embodiment. [Figure 1] FIG. 1 shows diagrammatically and exemplarily an electric motor drive unit for technical applications in motor vehicles according to the invention. [Figure 2] FIG. 2 shows a perspective view of a drive element designed as a worm. [Figure 3] FIG. 3 shows a cross section through the object shown in FIG. [Figure 4] FIG. 4 shows an alternative output shaft of an electric motor in a perspective view. [Figure 5] FIG. 5 is a cross-sectional view through the object shown in FIG.

[0021] Detailed Description

[0022]

[0020] The figure shows a representative example of an electric motor drive unit for automotive applications. Indeed, in the context of the embodiment, the electric motor drive unit is used in connection with a lock for a motor vehicle, in particular a lock for a motor vehicle door. In fact, within the scope of the embodiment according to Fig. 1, but without being limited thereto, the electric motor drive unit is designed as an opening drive for a locking mechanism 1, 2 consisting of a rotary latch 1 and a pawl 2, and is shown therein as a schematic. For this purpose, the electric drive unit operates on a release lever 3. To open the locking mechanism 1, 2, the electric motor drive unit acts on the release lever 3, causing it to pivot clockwise about its axis.

[0023]

[0021] As the release lever 3 moves clockwise, it engages with the lock mechanism 1 in the closed position, and the lock mechanism 2, which engages with the rotary latch 1, rotates counterclockwise around its axis 2. This releases the rotary latch 1, which can then swing clockwise around its axis to open, releasing the previously captured lock bolt, not explicitly shown. The same applies to an automobile door that supports a lock bolt, although not specifically shown.

[0024]

[0022] To this end, the electric drive unit according to the invention comprises an electric motor 4 and an output shaft 5, which is provided on the output side of the electric motor 4 and has a substantially circular cross section, for rotating the output shaft 5 at a high speed. A drive element 6 is mounted on the output shaft 5. In the embodiment, the drive element 6, made of plastic, is a worm 6, as shown in detail in the perspective views according to FIGS. 2 and 4. The worm 6 or drive element 6, made of plastic, meshes with a worm wheel 7, also made of plastic. The worm wheel 7 has an actuating pin 8. In this way, gearboxes 6, 7, 8 connected to the electric motor 4 are realized.

[0025] 1, the counterclockwise movement of the worm wheel 7 acting on the actuating pin 8 on the release lever 3 can be understood to mean the aforementioned clockwise movement of the release lever 3. This causes the pawl 2 to be lifted out of engagement with the rotary latch 1, effectively releasing the vehicle door. Of course, the electric motor drive unit described in detail below can also be used for other purposes and applications, as explained at the beginning.

[0026] 2 to 5, it is clear that the drive element or worm 6 made of plastic is not the only component of the gearboxes 6, 7, 8. However, in this embodiment, the drive element or worm 6 is also mounted on the output shaft 5, plugged into the output shaft 5 and, if necessary, further axially fixed. This can be done, for example, by additional application of adhesive or by other means.

[0027] For this purpose, the output shaft 5 engages in a receiving bore 9 inside the drive element or worm 6. In this embodiment, the receiving bore 9 is arranged centrally in the cylindrical thread 6 and extends axially.

[0028] 2 and 4, it can be seen that the output shaft 5 engages the worm 6 over a certain axial length, i.e., under the definition of an engagement area E. Furthermore, when the output shaft 5 engages the receiving hole 9 of the worm 6, a bilateral vent hole 10 is defined, which can best be understood by referring to the representation in FIG.

[0029]

[0027] In fact, according to the invention, the formation of the output shaft 5, which has an approximately circular cross section in the engagement area E of the receiving bore 9 of the worm 6, is substantially designed and pronounced in that at this location, two axially extending ridges 11, which have a chordal cross section, are realized in the first variant according to Figures 2 and 3. This is particularly clear from the cross section in Figure 3, in which it can be seen that the centre point M of the output shaft is approximately circular in cross section 5.

[0030]

[0028] Relative to this midpoint M, the two ridges 11 extend along a circular chord, each having an end at the circumferential tip of the associated output shaft 5 and connected to each other at their foot ends by an arc 12. The two ridges 11 associated with the arc 12 therefore define a compound U-shaped bridge 11, 12.

[0031]

[0029] Furthermore, according to this embodiment, the two ridges 11 extend parallel to each other and are equally spaced from the center point M. The protrusion 13 of the drive element 6 engages between the two ridges 11. A rotational coupling or connection is thus realized or transformed between the output shaft 5 and the drive element 6. Furthermore, the two ridges 11 on the outer edge each define a ventilation hole 10. In fact, the ridges 11, together with the inner wall of the receiving hole 9, act as the boundary of each ventilation hole 10.

[0032]

[0030] The protrusion 13 generally forcefully engages with the U-shaped protrusions 11, 12 to form a closure. In fact, the protrusion 13 is designed to be complementary to the U-shaped protrusions 11, 12, and is therefore designed as the U-shaped protrusion 13. The ventilation holes 10 are designed to have a circular cross section. Furthermore, in this embodiment, the two ventilation holes 10 have the same cross section and are arranged mirror-symmetrically with respect to the axis A passing through the center M of the output shaft 5.

[0033]

[0031] The drive element or worm 6 (and worm wheel 7) is generally made of a thermoplastic material. Plastics such as polyamide and in particular homopolyamide have proven particularly advantageous here. In contrast, the output shaft 5 of the electric motor 4 is usually made of metal. To merge the worm 6 with the output shaft 5, the worm 6 is pressed against the output shaft 5 so that there is a geometric closure in the direction of rotation of the output shaft 5. Two U-shaped ridges 11, 12 in the engagement region E of the receiving hole 9 of the worm 6 are usually formed on the output shaft 5 by forming the output shaft 5.

[0034] Similar advantages and effects are observed for the second variant according to Figures 4 and 5. Here, the output shaft 5 engages in the engagement area E by means of a D-shaped extension 14 in the receiving hole 9, which also provides a threaded connection for the screw 6. The ventilation holes 10 realized at the outer edge of the D-shaped extension 14 also provide final cooling.

[0035] Explanation of symbols

[0036] 1, 2. Locking mechanism, 1...Rotary latch, 3...Release lever, 2...claw part, 4...electric motor, 5...output shaft, 6, 7, 8...driving elements, 6...Warm, 7...worm gear, 8...operating pin, 9...receiving hole, 10...ventilation holes, 11, 12. U-shaped bridge, 11...Web, 12...Arc, 13...protrusion, 14...D-shaped extension, A...Axis, E...engagement area, M...Middle point.

Claims

1. An electric motor drive unit for automotive applications, comprising an electric motor (4) having an output shaft (5) of substantially circular cross section, and a drive element (6) mounted on said output shaft (5), The output shaft (5) engages a receiving hole (9) of the drive element (6) which defines at least one ventilation hole (10); 1. An electric motor drive unit for a motor vehicle, wherein the output shaft (5) has two raised portions (11) at least in an engagement area (E) of the receiving hole (9), the two raised portions (11) extending axially apart from each other and chord-shaped in cross section, a protrusion (13) of the drive element (6) engaging between the two raised portions (11) so as to be rotationally coupled, and each of the two raised portions (11) defining a ventilation hole (10) on the side of its outer edge.

2. 2. A drive unit according to claim 1, characterized in that the two ridges (11) extend parallel to each other.

3. 3. A drive unit according to claim 1 or 2, characterized in that the two ridges (11) extend in the axial direction of the output shaft (5).

4. A drive unit according to any one of claims 1 to 3, characterized in that the two ridges (11) terminate at a tip around the output shaft (5).

5. 5. A drive unit according to claim 1, wherein the two ridges (11) are connected to each other at the foot end by an arc (12) to form a compound U-shaped ridge (11, 12).

6. A drive unit as described in claim 5, characterized in that the protrusion (13) engages with the U-shaped ridges (11, 12).

7. 2. A drive unit according to claim 1, characterized in that the output shaft (5) is provided with ventilation holes (10) on its outer edge at least in the engagement area (E) of the receiving hole (9).

8. 8. Drive unit according to any one of claims 1 to 7, characterized in that the ventilation holes (10) are designed in cross section as arc segments.

9. A drive unit according to any one of claims 1 to 8, characterized in that the ventilation holes (10) are designed to have the same cross section.

10. 10. A drive unit according to any one of claims 1 to 9, characterized in that the ventilation holes (10) are arranged mirror-symmetrically with respect to an axis (A) extending through the center (M) of the output shaft (5) which has a substantially circular cross section.

11. A lock for a motor vehicle, in particular a lock for a motor vehicle door, comprising a drive unit according to any one of claims 1 to 10.

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