Harmonic drive

Abstract

The invention provides a harmonic drive (1) comprising three connecting elements (2, 9, 12), namely an input element (2), an output element (13) and a regulating element (9), and comprising a torsion-proof mechanism (15) running between the connecting elements (2, 9, 12), which comprises a torsion-proof element (18) which is concentric with the connecting elements (2, 9, 13) and which engages interlocking with one of the connecting elements (9) and frictionally with the other connecting element (2).

Description

[0001] This application is a divisional application of Chinese National Application No. 201980089000.4 (PCT application No. PCT / DE2019 / 101099), filed on December 17, 2019, entitled "Harmonic Drive Device". Technical Field

[0002] This invention relates to a harmonic drive device suitable for use as an adjusting gear in an electromechanical camshaft adjuster. The invention also relates to a method for fixing the harmonic drive device, particularly during transport or installation, to prevent misalignment. Background Technology

[0003] A camshaft adjuster is known from DE 10 2016 216 594B3, which is fixed by means of an anti-torsion device to prevent unintentional adjustment. The anti-torsion device of the known camshaft adjuster includes a spring that preloads the adjusting gear. The adjusting gear of the camshaft adjuster is designed as a harmonic drive, which has a flexural ring as an elastic transmission element.

[0004] Other mechanisms for fixing electromechanical camshaft adjusters to prevent adjustment are known from documents DE 10 2008 022 931A1 and DE 10 2008 022 932A1. In these cases, a rotary swashplate drive is provided as the adjusting gear of the camshaft adjuster.

[0005] A phase adjuster with a locking element, namely a camshaft adjuster, is known from DE 10 2009 019 397B4 for an internal combustion engine. When the camshaft adjuster is in operation, the locking element remains in the parked position. The locking element can be moved from its locked position to the parked position by means of pressurized oil or pressurized air. Summary of the Invention

[0006] The object of the present invention is to provide a harmonic drive device that is a further improvement over the prior art and can prevent unintentional adjustment, wherein the anti-torsion mechanism is provided with particularly easy operability and the erosion of the component structure of the harmonic drive device is avoided as much as possible.

[0007] According to the present invention, this objective is achieved by a harmonic drive device having the following characteristics. This objective is also achieved by a method for fixing the harmonic drive device to prevent adjustment. The construction and advantages of the invention explained below in conjunction with the fixing method also apply similarly to this mechanism, i.e., a harmonic drive device including an anti-torsion mechanism, and vice versa.

[0008] In its basic concept, a harmonic drive includes three connecting elements: an input element in the form of a housing that can rotate as a whole, an output element that will be connected to the shaft to be adjusted, particularly the camshaft, and an adjustment element, and includes an anti-torsional mechanism that operates between two of the three connecting elements.

[0009] According to the present invention, the anti-torsion mechanism includes an anti-torsion element concentric with all connecting elements and interlockingly engaged with one of the three connecting elements, and frictionally engaged with another connecting element. It has been shown that, without any geometric modifications to any components, both anti-torsion operation and the ability to secure conventional harmonic drive devices, particularly during transport or installation, can be achieved.

[0010] In a preferred embodiment, the anti-torsion element is a retaining ring made of plastic, which can be positioned such that it frictionally engages with the input element and interlocks with the adjustment element.

[0011] In this configuration, the interlocking anti-torsional profile is preferably formed on the side of the adjusting element by two bolts, which are securely connected to the inner ring of the wave generator of the harmonic drive. The two bolts may be part of an Oldham coupling, which acts as a compensating coupling to compensate for axial misalignment between the harmonic drive and the electric motor driving the adjusting element (i.e., the inner ring of the wave generator including the bolts).

[0012] The retaining ring can be efficiently manufactured by injection molding. In an advantageous embodiment, the retaining ring is molded into a U-shape. In this case, the corrugated inner section of the U-shaped profile through which the retaining ring passes forms an interlocking anti-torsional profile that directly engages with the bolts of the adjusting element. Simultaneously, the retaining ring in this embodiment has a smooth outer section of the U-shaped profile, which is configured for frictional anti-torsional action relative to the housing of the input element, i.e., the harmonic drive.

[0013] The radially outward-pointing flange is preferably molded onto the U-shaped profile defined by the retaining ring, and sits against the end face of the input element when the retaining ring is inserted. For ease of handling, tabs suitable for manual removal of the retaining ring from the connecting element can be molded onto the flange.

[0014] The advantage of a retaining ring is that it can be placed between specified elements at any position relative to the input element. The retaining ring itself can also be positioned at any desired angular location.

[0015] During the installation of a camshaft adjuster, which includes a harmonic drive as an adjusting gear, if an electric motor for actuating the harmonic drive is attached to the harmonic drive, the defined angular relationship between the input and output elements of the harmonic drive can first be set and maintained by means of a retaining ring. At this point, the angular position of the adjusting element is crucial. Then, the compensating coupling and the electric motor must be attached to the adjusting element. This can only be achieved after removing the retaining ring from the harmonic drive, which can be easily done without tools. Therefore, due to the principles involved, the installation of the electric motor is excluded when the harmonic drive is locked.

[0016] Fixed rings that operate on a frictional / interlocking basis and move equally at each corner position of the components to be fixed relative to each other are also suitable for automated production lines.

[0017] In general, the method of using its fixed harmonic drive to prevent adjustment is characterized by inserting a fixed ring between the adjustment element and the housing of the harmonic drive, so that a frictional connection is formed between the fixed ring and the housing, and an interlocking connection is formed between the fixed ring and the adjustment element.

[0018] Harmonic drives can be used not only as electromechanical camshaft adjusters, but also in industrial applications such as industrial robots or machine tools. Attached Figure Description

[0019] An exemplary embodiment of the invention is described in more detail below with the aid of the accompanying drawings. In the text:

[0020] Figure 1 The harmonic drive mechanism of the electric camshaft adjuster with an inserted anti-torsion device is shown in perspective view.

[0021] Figure 2 Showing according to Figure 1 The cross-sectional view of the arrangement shown.

[0022] Figure 3 The fixed ring of the harmonic drive device is shown. Detailed Implementation

[0023] The harmonic drive unit, generally identified by reference numeral 1 in the accompanying drawings, is part of an electric camshaft adjuster (not shown further) used to adjust the camshaft of an internal combustion engine (i.e., a reciprocating piston engine) relative to the crankshaft of the engine. For the main function of the harmonic drive unit 1, which includes the camshaft adjuster, refer to the prior art cited at the beginning.

[0024] The harmonic drive 1, used as the adjusting gear, is a three-axis gear. The three elements capable of rotating about a common axis (i.e., the axis of rotation of the camshaft) are generally referred to as connecting elements 2, 9, and 13, each interacting directly with external components (i.e., components not belonging to the harmonic drive 1). This involves the input element 2, designed as a housing, the adjusting element 9, and the output element 13, designed as a ring gear.

[0025] In an exemplary embodiment, input element 2 is constructed of several parts and includes a sprocket 3, which is driven by the crankshaft when the camshaft adjuster is in operation, rotating at half the crankshaft speed. Output element 13 is configured to be non-rotatably connected to the camshaft to be adjusted. Adjustment element 9 is designed as the inner ring of rolling bearing 8, which is part of wave generator 7. Wave generator 7 is driven by an electric motor (e.g., a brushless synchronous motor, not shown) via a compensating coupling, namely an Oldham coupling. The compensating coupling has an Oldham disc (not shown), into which two bolts 14 engage when the camshaft adjuster is fully assembled. Bolts 14 are fastened in the aforementioned inner ring of the rolling bearing and are assigned to adjustment element 9.

[0026] As long as the adjusting element 9 rotates at the speed of the input element 2, the camshaft also rotates at that speed along with the output element 13. Therefore, phase adjustment of the camshaft will not occur under this operating condition of the harmonic drive 1.

[0027] The adjusting element 9 is designed such that the outer contour of the rolling bearing ring deviates from a circular shape. In a manner known per se, the adjusting element 9 forms a non-circular, elliptical raceway for the rolling element 10 (i.e., the ball). Compared to the adjusting element 9, the associated outer ring 11 in which the ball 10 rolls is designed to be flexible, allowing it to permanently adapt to the non-circular shape of the adjusting element 9. The outer ring 11 is further surrounded by a flexible transmission element 12, which is externally toothed and also referred to as a flexure ring.

[0028] The external teeth of the flexural ring 12 engage with the internal teeth of the sprocket 3 and the output element 13 at two radially opposite points. The sprocket 3 is securely connected to the housing element 4 by screws 6, and the housing element is also assigned to the input element 2. Furthermore, the input element 2 is assigned a housing cover 5, which is located on the end face of the harmonic drive 1 facing the camshaft to be adjusted. The output element 13 is axially fixed within the harmonic drive 1 by the housing cover 5. The housing element 4 serves to fix the outer ring 11 within the harmonic drive 1 along opposite axial directions, thereby securing the entire wave generator 7.

[0029] Different numbers of teeth in the flexure ring 12, input element 2, and output element 13 ensure, in a manner known per se, that complete rotation of the adjusting element 9 relative to the input element 2 results in relatively small pivoting between the input element 2 and the output element 13. Here, the coupling stage can be formed between the flexure ring 12 and the input element 2, or between the flexure ring 12 and the output element 13. The transmission stage of the harmonic drive is correspondingly formed by the flexure ring 12 and the output element 13, or between the flexure ring 12 and the input element 2. In the former case, the harmonic drive 1 is a spur gear; in the latter case, it is a negative gear.

[0030] Before the electric motor is installed on the harmonic drive device 1, it is first blocked in a defined position. For this purpose, an anti-torsion mechanism 15 is provided, which is formed on one hand by two elements 2, 9 (i.e., input element 2 and adjustment element 9, which are assigned to the connecting elements of the harmonic drive device 1), and on the other hand by an anti-torsion element 18 in the form of a retaining ring.

[0031] The retaining ring 18 frictionally engages with the input element 2 on its outer side and interlocks with the adjusting element 9 on its inner side. In cross-section, the retaining ring 18 (which is a plastic part produced by injection molding) defines a U-shaped profile 19.

[0032] The internal corrugated section 20 is formed of a U-shaped profile 19, which can be configured to create an interlocking anti-torsion device between the adjusting element 9 and the retaining ring 18. The interlocking anti-torsion device consists of an internal anti-torsion profile 16 on the side of the adjusting element 9 and an external anti-torsion profile 17 on the side of the retaining ring 18. Here, the internal anti-torsion profile 16 is provided by a component already present in the harmonic drive device 1, i.e., by bolts 14. The associated external anti-torsion profile 17 is in the form of an annular closed corrugated section 20 of the retaining ring 18.

[0033] The corrugated section 20 is concentrically surrounded by an outer smooth section 21, which is also formed by the U-shaped profile 19 of the retaining ring 18. In an exemplary embodiment, the outer annular section 21 contacts the cylindrical inner circumferential surface of the housing element 4. In any case, the smooth section 21 is part of an anti-torsional device against friction between the retaining ring 18 and the input element 2.

[0034] The radially outward-pointing flange 22 of the retaining ring 18 abuts the outer cylindrical section 21. According to... Figure 1 and Figure 2 In this arrangement, the flange 22 rests against the end face of the housing element 4. A tab 23 extending from the flange 22 can also be seen, which is used for simple manual removal of the retaining ring 18 from the harmonic drive 1. Connection of the electric motor of the camshaft adjuster to the harmonic drive 1 is only possible with the retaining ring 18 removed.

[0035] Explanation of reference numerals in the attached figures

[0036] 1 Harmonic Drive Device

[0037] 2. Housing, Input Components

[0038] 3 sprockets

[0039] 4. Housing components

[0040] 5. Housing cover

[0041] 6 screws

[0042] 7-wave generator

[0043] 8 Rolling bearings

[0044] 9. Inner ring, adjusting element

[0045] 10 Rolling elements

[0046] 11 Outer Ring

[0047] 12. Flexural ring, flexible transmission element

[0048] 13 Output ring gear, output element

[0049] 14 bolts

[0050] 15 Anti-torsion mechanism

[0051] 16 Internal anti-torsional profile components

[0052] 17 External anti-torsional profile component

[0053] 18. Anti-torsion element, retaining ring

[0054] 19U profile

[0055] 20 Internal corrugated sections

[0056] 21 External smooth section

[0057] 22 Flange

[0058] 23 protrusions

Claims

1. A harmonic drive device having three connecting elements, namely an input element (2), an output element (13), and an adjusting element (9), and an anti-torsion mounting and fixing mechanism (15) operating between said connecting elements (2, 9, 13), characterized in that, The mounting and fixing mechanism (15) includes an anti-torsion element (18) concentric with the connecting element. The anti-torsion element (18) is designed to frictionally engage with the input element (2) and to interlock with the adjusting element (9). The anti-torsion element (18) has an outer annular section (21) that contacts the cylindrical inner circumferential surface of the input element to achieve a frictional engagement.

2. The harmonic drive device according to claim 1, characterized in that, The interlocking anti-torsion profile (16) on the side of the adjusting element (9) is formed by two bolts (14) which are securely connected to the inner ring of the wave generator (7).

3. The harmonic drive device according to claim 2, characterized in that, The two bolts (14) are components of the compensating coupling.

4. The harmonic drive device according to claim 1, characterized in that, The interlocking anti-torsion profile (17) on the side of the anti-torsion element (18) is formed by the corrugated inner section (20) of the U-shaped profile (19) of the anti-torsion element (18).

5. The harmonic drive device according to claim 4, characterized in that, The anti-torsion element (18) has a smooth outer section (21) of the U-shaped profile (19) for frictional anti-torsion relative to the input element (2).

6. The harmonic drive device according to claim 5, characterized in that, A flange (22) is formed on the U-shaped profile (19) defined by the anti-torsion element (18), and the flange is configured to rest against the input element (2).

7. The harmonic drive device according to claim 6, characterized in that, A tab (23) adapted to be manually removed from the connecting elements (2, 9, 13) of the anti-torsion element (18) is formed on the flange (22).

8. A method for fixing a harmonic drive device (1) to prevent adjustment, the method comprising the steps of: - Provide a harmonic drive device (1) having a housing that can be rotated as a whole and used as an input element (2), and an adjustment element (9) of a component designed as a wave generator (7). - A retaining ring (18) is provided as an anti-torsion mounting element or a movable locking element, wherein the retaining ring has an outer annular section (21) for frictional engagement with the cylindrical inner circumferential surface of the input element. - Insert the retaining ring (18) between the adjusting element (9) and the housing, such that a frictional fit is generated between the retaining ring (18) and the housing, and an interlocking fit is generated between the retaining ring (18) and the adjusting element (9).

9. The method according to claim 8, wherein after the retaining ring (18) is inserted, the input element (2) and the output element (13) are each fixed to a component such that relative adjustment of the components is prevented when the adjusting element (9) is stationary, and wherein the retaining ring (18) is removed after fixing.

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