Adjustment device for an internal combustion engine

Abstract

Adjusting device comprising an actuating mechanism (3) designed as a wave gear and an electric motor (2), wherein a rotor (21) of the electric motor (2) is designed as an external rotor and is provided for actuating a wave generator (29) of the wave gear (3), and wherein an output element (4) of the wave gear (3) deformable by the wave generator (29) has a cup shape and projects beyond the rotor (21) at least in the radial direction, wherein the electric motor (2) has a hollow, annular stator (20) and the rotor (21) of the electric motor (2) is rotationally fixed to a separate inner ring (31) of the wave generator (29), wherein the stator (20) extends in the axial direction of the electric motor (2) beyond an electromagnetically interacting area (23) of the rotor (21), characterized in that the stator (20) in its area extending beyond the rotor (21) the protruding section is tapered and carries a rolling bearing (26),by means of which an inner cylindrical area (24) of the rotor (21), which does not interact electromagnetically with the stator (20), is mounted.

Description

[0001] The invention relates to an adjusting device suitable for adjusting a shaft, in particular for use in an internal combustion engine, according to the preamble of claim 1.

[0002] A generic adjusting device is known from DE 10 2015 204 420 A1. The known adjusting device enables the adjustment of the compression ratio of a reciprocating internal combustion engine and comprises an electric motor designed as a BLDC motor and a wave gear, wherein the rotor of the electric motor simultaneously functions as a component of a wave generator by providing an elliptical raceway for the rolling elements of a rolling bearing. With the aid of this non-circular rolling bearing, a flexible, cup-shaped running element, which is connected to an output shaft, is deformed during operation of the adjusting device.

[0003] Other designs of adjustment devices for internal combustion engines are known, for example, from documents DE 10 2011 083 798 A1, DE 10 2006 007 584 A1, and DE 41 10 195 C2. In these cases, the devices are electric camshaft adjusters.

[0004] An electromechanical adjustment system suitable for internal combustion engines, whose electric motor is designed as a brushless disc rotor motor, is disclosed, for example, in DE 10 2007 054 546 A1.

[0005] WO 2012 / 110132 A1 discloses a wave gear with a double-row wave generator. WO 2016 / 024340 A1 discloses a generic adjusting device.

[0006] The invention is based on the objective of providing an adjustment device suitable for an internal combustion engine of a motor vehicle, which is a further development compared to the aforementioned prior art and which is characterized by a particularly easy-to-assemble and at the same time compact design.

[0007] This problem is solved according to the invention by an adjusting device with the features of claim 1. The adjusting device comprises, in a basic concept known per se, an actuating mechanism constructed as a wave gear and an electric motor provided for actuating the wave gear, the rotor of which is designed as an external rotor. The wave gear comprises a wave generator by which an output element of the wave gear is deformable. This output element is cup-shaped and projects beyond the rotor of the electric motor at least in the radial direction, in particular both in the axial and radial directions. According to the invention, the electric motor has a hollow, annular stator, while the rotor of the electric motor is rotationally fixed to a separate inner ring of the wave generator. This inner ring provides a non-circular rolling element raceway for the wave generator.The stator cavity is preferably designed as a bore extending through the entire stator, concentric to the central axis of the electric motor, and not necessarily having a uniform diameter.

[0008] This design provides a compact, nested construction for the motor-gearbox assembly of the adjustment device, while simultaneously facilitating manufacturing by separating the inner ring of the wave generator from the rotor of the electric motor. The electric motor of the adjustment device is preferably a brushless direct current (BLDC) motor. The hollow design of the stator allows a tool to be inserted through a corresponding bore in the stator, attaching a component to be mounted. Depending on the design of the adjustment device, the through-hole in the stator can also be used for routing electrical conductors.

[0009] In a first embodiment of the invention, the stator comprises a stator support which extends in the axial direction of the electric motor beyond a region of the rotor that interacts electromagnetically with the stator, in particular a region that carries magnets. The stator support can be efficiently manufactured as a plastic component and preferably also represents a plastic overmolding of current-carrying coils and laminations of the stator. In a particularly space-saving design, the stator support is tapered in its section projecting beyond the rotor and carries a rolling bearing in this section, which supports an inner cylindrical region of the rotor that does not interact electromagnetically with the stator. The rolling bearing is, for example, a multi-row bearing arrangement, in particular in the form of two needle bearings.

[0010] The inner ring of the wave generator concentrically surrounds the rolling bearing, and in a preferred embodiment, it is spaced apart from it, i.e., separated by an annular gap, and the wave generator is guided radially through a cylindrical section of the output element. This means that the inner ring of the wave generator has clearance relative to the rolling bearing, which is provided for supporting the rotor of the electric motor.

[0011] In a preferred embodiment, the inner ring of the wave generator is coupled to the rotor of the electric motor, allowing for radial misalignment. The wave generator, including the inner ring, is located on the open side of the cup-shaped output element of the wave gear. Optionally, a compensating coupling, particularly an Oldham coupling, is arranged between the rotor of the electric motor and the inner ring of the wave generator. This coupling allows for a limited axial misalignment between the rotor and the inner ring and is simultaneously rigid in the circumferential direction. A single-finger coupling is also suitable as a compensating coupling acting between the rotor of the electric motor and the inner ring of the wave generator.

[0012] In the embodiment according to claim 6, the overall cup-shaped output element has a base section through which a central screw, designed for attachment to an adjustable shaft, passes, the head of which is arranged in the through-hole cavity of the stator. Thanks to the through-hole of the stator, the entire adjustment device, i.e., the assembly consisting of the electric motor and the actuating gear including the shaft generator, can be mounted as a whole on the adjustable shaft by means of the central screw.

[0013] The stator is held within the adjustment device, for example, by a mounting plate or a housing element, wherein a connector housing made of plastic is attached to a first end face of the mounting plate or housing element and, optionally, a rotary angle sensor is arranged axially between the mounting plate and the rotor of the electric motor on the opposite end face.

[0014] The adjusting device is suitable, among other things, for use in a device for varying the compression ratio of a reciprocating engine. The adjusting device can also be used as an electric camshaft adjuster for an internal combustion engine.

[0015] An embodiment of the invention is explained in more detail below with reference to a drawing. This drawing shows: Fig. 1. An adjustment device in a simplified sectional view.

[0016] An adjustment device, designated in its entirety by reference numeral 1, comprises an actuating gear 3, namely a wave gear, and an electric motor 2, namely a BLDC motor, wherein the electric motor 2 is integrated into the actuating gear 3.

[0017] The actuator 3 has a cup-shaped flexible gear component as a deformable output element 4, which is also referred to as a flexible cup. A cylindrical section of the gear component in its undeformed state is designated 5, and an adjoining bottom section is designated 6.

[0018] On the end face of the deformable output element 4, facing away from the base section 6, an external toothing 7 is formed on the outer circumference of the cylindrical section 5. The external toothing 7 partially engages with an internal toothing 8 of a rigid housing component 9, which is fixedly connected to an surrounding structure. A cylindrical section 10 of the housing component 9, which directly surrounds the external toothing 7, is integrally connected to a flange 11 of the housing component 9. Another housing element 12 is connected to the housing component 9, which in turn is connected to a connector housing 13.

[0019] The flexible gear component 4 of the wave gear 3 functions as the output element of the wave gear 3 and is rigidly connected to a shaft 14, namely an eccentric shaft of a device for varying the compression ratio of a reciprocating engine. The output element 4 is attached to the shaft 14 by a central screw 15, the head 16 of which is located inside the wave gear 3.

[0020] On the end face of the wave gear 13 opposite the central screw 15, it is covered by a cover plate 17, which has a central opening 18. Through this central opening 18, as long as the plug housing 13 is not placed on the wave gear 3, a tool can be attached to the head 16 of the central screw 15, the central screw 15 being inserted through an opening 19 in the bottom section 6 of the output element 4.

[0021] The electric motor 2, which is integrated into the installation space occupied by the wave gear 3 including the output element 4, has a stator 20 that is rigidly connected to the housing component 9, the cover plate 17, and the housing element 12. The stator 20 interacts with a rotor 21, which carries several magnets 22, namely permanent magnets. The entire stator 20 is designed as an annular, hollow component, with its cavity extending as a through-bore from the opening 18 to the opening 19 and widening in steps along this direction. Both the inner and outer circumferences of the stator 20 are formed by a plastic overmolding that surrounds currentable coils that interact with the magnet 22 of the rotor 21.

[0022] In principle comparable to the stator 20, the rotor 21 also has a ring-shaped, stepped form, with a widening from the end face where the connector housing 13 is located to the end face where the shaft 14 is connected. An outer cylindrical section of the rotor 21, on the inside of which the magnets 22 are held, is designated 23. The outer cylindrical section 23 is rigidly connected via an intermediate piece 25 to an inner cylindrical section 24, in which the rotor 21 has no electromagnetic function.

[0023] The inner cylindrical section 24 is rotatably mounted on the stator 20 by means of a double-row needle bearing, generally referred to as a rolling bearing 26. Needles 28 of the needle bearing roll on a sheet metal sleeve 27, which directly surrounds the stator 20.

[0024] The inner cylindrical section 24 is radially surrounded by a shaft generator 29, forming an annular gap. The shaft generator 29 comprises a ball bearing 30 with an inner ring 31, which is rotationally fixed to the rotor 21. For this purpose, the inner ring 31 has an inner ring extension 32 facing the intermediate piece 25, which engages in a receptacle of the intermediate piece 25, thus forming a coupling device 33 between the rotor 21 and the inner ring 31. The coupling device 33 is a compensating coupling that establishes a rotationally fixed connection between the rotor 21 and the inner ring 31 while simultaneously allowing axial misalignment between the aforementioned parts 21 and 31.

[0025] The balls of the ball bearing 30, designated 34, contact an outer ring 35, which, unlike the inner ring 31, is elastically flexible. This allows the outer ring 35 to permanently conform to the elliptical, non-circular shape of the inner ring 31 of the shaft generator 29. In this way, the external teeth 7 of the output element 4 engage with the internal teeth 8 of the housing element 12, designed as a ring gear, only in two diametrically opposed sections. Otherwise, the external teeth 7 are displaced from the internal teeth 8. A slightly different number of teeth on the internal gearing 8 on the one hand and the external gearing 7 on the other hand ensures, in a manner known in principle, that during a full revolution of the rotor 21 the output element 4 is rotated slightly relative to the housing-fixed arrangement, which includes the ring gear 12, the housing element 12, and the connector housing 13.The wave gear 3 thus functions as a high-reduction actuator.

[0026] The angular position of the rotor 21 can be detected by means of a rotary angle sensor 36, which is arranged axially between the connector housing 13 and the shaft generator 29. The rotary angle sensor 36 is implemented as a circuit board-based through-hole solution and is located on the end face of the housing element 12 facing the rotor 21. Reference symbol list 1 Adjustment device 2 electric motors 3 actuating gears, wave gears 4 Output element 5 cylindrical section 6. Ground section 7 External teeth 8 Internal teeth 9 Housing component 10 cylindrical section 11 Flange 12 Housing element, ring gear 13 connector housings 14 shaft, eccentric shaft 15 Central screw 16 heads 17 Cover plate 18 Opening in the cover plate 19 Opening in the floor section 20 Stator 21 Rotor 22 Magnet 23 outer cylindrical area 24 inner cylindrical area 25 Intermediate piece 26 Rolling bearing 27 Sheet metal sleeve 28 needles 29 Wave generator 30 ball bearings 31 inner ring 32 Inner ring expansion 33 Coupling device 34 balls 35 Outer ring 36 Rotary angle sensors

Claims

[1] Adjusting device, comprising an actuating mechanism (3) designed as a wave gear, and an electric motor (2), wherein a rotor (21) of the electric motor (2) is designed as an external rotor and is provided for actuating a wave generator (29) of the wave gear (3), and wherein an output element (4) of the wave gear (3) deformable by the wave generator (29) has a cup shape and projects beyond the rotor (21) at least in the radial direction, wherein the electric motor (2) has a hollow, annular stator (20) and the rotor (21) of the electric motor (2) is rotationally fixed to a separate inner ring (31) of the wave generator (29), wherein the stator (20) extends in the axial direction of the electric motor (2) beyond an electromagnetically interacting area (23) of the rotor (21) with the stator (20), characterized by, that the stator (20) is tapered in its section extending beyond the rotor (21) and carries a rolling bearing (26) by means of which an inner cylindrical area (24) of the rotor (21), which does not interact electromagnetically with the stator (20), is supported. [2] Adjustment device according to claim 1, characterized by , that the electric motor (29) is designed as a brushless DC motor. [3] Adjusting device according to claim 1 or 2, characterized by , that the rolling bearing (26) is designed in multiple rows. [4] Adjustment device according to any one of claims 1 to 3, characterized by , that the inner ring (31) of the shaft generator (29) concentrically surrounds the rolling bearing (26), being spaced apart from it, and the shaft generator (29) is guided radially through a cylindrical section (5) of the output element (4). [5] Adjustment device according to any one of claims 1 to 4, characterized by, that the inner ring (31) of the wave generator (29) is coupled to the rotor (21) of the electric motor (2) while allowing a radial offset. [6] Adjustment device according to any one of claims 1 to 5, characterized by , that a central screw (15) for fastening to an adjustable shaft (14) is inserted through a bottom section (6) of the cup-shaped output element (4), the head (16) of which is arranged in the cavity of the stator (20). [7] Adjustment device according to any one of claims 1 to 6, characterized by , that the stator (20) is held by a housing element (12), wherein a connector housing (13) is connected to the housing element (12) on one end face and a rotation angle sensor (36) is arranged axially between the housing element (12) and the rotor (21) of the electric motor (2) on the opposite end face. [8] Use of an adjustment device according to one of the preceding claims in a device for varying the compression ratio of a reciprocating engine.

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