Three-shaft gearbox and camshaft adjuster

Abstract

Three-shaft transmission (1), in particular in the form of an actuating transmission of a camshaft adjuster (10), comprises two connecting shafts (2, 3), namely a drive shaft (2) and an output shaft (3), as well as an adjusting shaft (16) concentric to the connecting shafts (2, 3), wherein a locking mechanism (5) effective between one of the two connecting shafts (2, 3) and the adjusting shaft (16) can be activated by a relative rotation between the connecting shafts (2, 3).

Description

[0001] The invention relates to a three-shaft transmission comprising three concentrically arranged shafts. The invention further relates to a camshaft adjuster with a three-shaft transmission.

[0002] DE 10 2021 105 281 A1 discloses an electromechanical camshaft adjuster comprising an actuating mechanism designed as a three-shaft drive. Several fail-safe positions exist for an output element of the three-shaft drive relative to a drive element of the same drive, which is driven by a traction element, namely a chain. The three-shaft drive is a wave gear drive. In the case of DE 10 2021 105 281 A1, the fail-safe positions are defined by the detent interaction between an actuating element of the wave gear drive and the drive element. An inner ring of the wave generator is considered part of the actuating element.

[0003] Another camshaft adjuster with at least one fail-safe position, which is defined as a detent position, is described in patent application DE 10 2022 126 038.0. In this case, a detent position is defined by a detent device acting directly between a drive element and an output element. The detent position can be identical to a stop position of the output element.

[0004] Various wave gears in which a torque is generated with the help of a spring are known, for example, from documents DE 10 2019 106 338 A1, DE 10 2019 132 995 A1 and DE 10 2018 117 976 A1.

[0005] A camshaft adjuster described in DE 10 2014 202 060 A1 comprises an actuator that drives an adjusting shaft by overcoming a torque dependent on its angular position, thereby providing detent positions of an output shaft. The detent function is achieved through a special design of components of a rolling bearing in a shaft generator of the camshaft adjuster. For this purpose, for example, a non-circular design of the inner ring of said rolling bearing with numerous flats is provided. Alternatively, the use of rolling elements whose cross-section deviates from a circular shape is proposed. Examples given are non-circular rollers or needles with a slightly elliptical or polygonal cross-section. Additionally, the possibility of using different rolling elements within the rolling bearing, which have slightly different diameters, is mentioned.The transmission of the camshaft adjuster according to DE 10 2014 202 060 A1 can be a three-shaft transmission or a four-shaft transmission.

[0006] The invention is based on the objective of providing a three-shaft transmission that is further developed compared to the aforementioned prior art, compact and easy to manufacture, and has at least one detent position, and which avoids voltage peaks as far as possible when approaching the detent position.

[0007] This problem is solved according to the invention by a three-shaft transmission according to claim 1. According to claim 10, the three-shaft transmission is particularly suitable for use in a camshaft adjuster.

[0008] The three-shaft transmission comprises two connecting shafts, namely a drive shaft and an output shaft, as well as an adjusting shaft concentric to the connecting shafts, wherein a locking mechanism effective between one of the two connecting shafts and the adjusting shaft can be activated and released by a relative rotation between the connecting shafts.

[0009] Thus, all three shafts of the gearbox—that is, the two connecting shafts as well as the adjusting shaft—are integrated into the locking mechanism. This represents a mechanically gentler solution than a direct blockage between the connecting shafts or a blockage between one of the two connecting shafts and the adjusting shaft that occurs without the involvement of the second connecting shaft.

[0010] As long as the adjusting shaft rotates at the same speed as the connecting shaft acting as the drive shaft, the output shaft also rotates at the same speed. Only a change in the speed of the adjusting shaft relative to the rotation of the drive shaft leads to a relative rotation between the two connecting shafts.

[0011] The term "locking mechanism" does not necessarily imply that all rotation between the adjusting shaft and the connecting shafts is prevented. Rather, variations of the locking mechanism are also possible in which this mechanism only prevents further rotation of the adjusting shaft relative to the connecting shaft in a specific direction, while allowing rotation of the adjusting shaft relative to the connecting shaft in the opposite direction. In such a case, the locking mechanism is designed as a stop mechanism between the adjusting shaft and one of the connecting shafts.

[0012] According to various possible embodiments, the locking mechanism comprises a pin guided in one of the connecting shafts, which is axially displaceable through the other connecting shaft and is designed to interact with a stop contour provided on the adjusting shaft. In particular, the pin can be received in a bore located in the output shaft. Regardless of in which of the two connecting shafts the pin is slidably guided, the pin can, for example, be arranged in the area of ​​an end stop acting directly between the connecting shafts.

[0013] The term "shafts" is used for rotating parts of the three-shaft transmission, which do not necessarily have an elongated wave shape. For example, so-called shafts, which function as one of the three shafts of the three-shaft transmission, can be designed as a disc or as a more complexly shaped rotatable part.

[0014] A detent device integrated into the three-shaft transmission can be formed, for example, on the one hand by the pin or another bolt-, blade-, or disc-shaped element, and on the other hand by a detent assembly located on the side of the adjusting shaft. The detent assembly can include a spring-loaded ball designed to engage with a detent recess on the end face of the pin or in a functionally equivalent element.

[0015] Regardless of the geometric design of the detent device, its detent function can be overridden by an existing electric drive of the adjusting shaft. This means that no separate device, such as an electromagnetic one, is required to release the detent function.

[0016] The three-shaft transmission can be designed as a wave gear. Other designs of three-shaft transmissions, such as swashplate transmissions, are also possible. If the three-shaft transmission is a wave gear, the adjusting shaft is typically the inner ring of a wave generator.

[0017] When using a three-shaft drive, particularly a wave drive, in an electromechanical camshaft adjuster, the drive shaft of the three-shaft drive is in many cases driven by a traction element, i.e., by means of a chain or a belt. Driving the drive shaft via a gear transmission, particularly a spur gear transmission, is also possible.

[0018] Several embodiments of the invention are explained in more detail below with reference to a drawing. This drawing shows: Fig. 1. A three-shaft gear unit, namely a wave gear unit, intended as an actuating mechanism for an electromechanical camshaft adjuster, in a cutaway perspective view. Fig. 2 the wave gear after Fig. 1 in another cutaway view, Fig. 3 and Fig. 4 a locking mechanism of the wave gear according to the Fig. 1 and Fig. 2 in different settings, Fig. 5 an alternative design of a locking mechanism for a three-shaft gearbox, Fig. 6 and Fig. 7 one compared to the variant according to the Fig. 1 to 4 further developed locking mechanism of a three-shaft gearbox.

[0019] Unless otherwise stated, the following explanations apply to all embodiments. Corresponding or essentially equivalent parts are marked with the same reference numerals in all figures.

[0020] A camshaft adjuster, designated by reference numeral 10, is designed as an electromechanical adjuster and is intended for adjusting the intake or exhaust camshaft of an internal combustion engine designed as a reciprocating piston engine. The camshaft adjuster 10 comprises an actuating mechanism, which is designed as a three-shaft drive 1 in the form of a wave gear. Regarding the fundamental function of the camshaft adjuster 10, reference is made to the prior art cited above.

[0021] A drive shaft 2 of the wave gear 1 is integrally formed with a sprocket 35, which rotates at half the crankshaft speed. Alternatively, a rigid connection of a separate sprocket 35 or belt pulley to the drive shaft 2 is possible. Likewise, another drive for the camshaft, for example via a gear drive, is also feasible. In any case, the drive shaft 2 is driven by the crankshaft of the internal combustion engine.

[0022] The output shaft of the wave gear 1, designated 3, is rigidly connected to the camshaft to be adjusted. The input shaft 2 and the output shaft 3 are collectively referred to as connecting shafts 2 and 3. An angle limiter 4 is in place between the input shaft 2 and the output shaft 3. A locking mechanism 5, which will be described in more detail below, prevents the output shaft 3 from directly and forcefully striking the input shaft 2.

[0023] The locking mechanism 5 is effective between one of the connecting shafts 2, 3 (in the present case, the output shaft 3) and an adjusting shaft 16, which is the third shaft of the three-shaft transmission 1. An actuating mechanism 6, formed by the two connecting shafts 2, 3, is provided for actuating the locking mechanism 5.

[0024] The function of the actuating mechanism 6 is particularly evident from a comparison of the Fig. 3 and Fig. 4 as well as from a comparison of the Fig. 6 and Fig. 7. Depending on the angular relationship between the connecting shafts 2 and 3, a ramp 7, located on the drive shaft 2, displaces a pin 11, which is guided in the output shaft 3 and aligned parallel to the central axis of the wave gear 1. A roof contour of the pin 11, which interacts directly with the ramp 7, is designated 8. Due to the rotationally symmetrical shape of the conical roof contour 8, anti-rotation protection of the pin 11 is not strictly necessary in these cases. A retaining ring 9 prevents the pin 11 from falling out of the output element 3. The pin 11 is spring-loaded by a spring 12, namely a helical spring designed as a compression spring.

[0025] As long as the drive element 2 does not contact pin 11, pin 11 is extended to its maximum extent from the output element 3 in the direction of the drive element 2. The adjusting shaft 16 is located on the side of the output shaft 3 that faces away from the area of ​​the drive shaft 2 equipped with the ramp 7.

[0026] A bolt 14 is held in the adjusting shaft 16, through which a stop contour 13 is provided against which the pin 11 can abut when it is pressed by the drive shaft 2 against the force of the spring 12. As can be seen from the Fig. 3 and Fig. As can be seen from Figure 4, the stop contour 13, which is part of the locking mechanism 5, represents a rotational anti-rotation device effective in one direction between the adjusting shaft 16 and the output shaft 3. The adjusting shaft 16 remains rotatable in the opposite direction. An adjustment from the configuration according to Fig. 4 into the constellation after Fig. 3 corresponds approximately to a full revolution of the adjusting shaft 16. Due to the given reduction ratio of the wave gear 1, a full revolution of the adjusting shaft 16, with respect to the drive shaft 2, is accompanied only by a slight pivoting between the connecting shafts 2, 3.

[0027] In contrast to the exemplary embodiment according to the Fig. 1 to 4 exist in the construction form according to Fig. 5 on the output shaft 3 a stop surface 27, which is provided for direct interaction with a counter contour of the drive shaft 2 adjacent to the ramp 7. Before the drive shaft 2 is stopped at the stop surface 27, even in the embodiment according to Fig. 5 the ramp 7 the roof contour 8, so that before the relative rotation between the connecting shafts 2, 3 is stopped, the pin 11 is displaced in its axial direction, i.e. in the axial direction of all shafts 2, 3, 16 and thus of the entire wave gear 1, which has a damping effect on the stop function.

[0028] In contrast to the one in Fig. In the constellation sketched in Figure 5, a stop surface 27 can also be located at an angle further away from pin 11. This also applies to the angle limits 4 in the embodiment according to the Fig. 1 to 4 and in the exemplary embodiment according to the Fig. 6 and Fig. 7.

[0029] In all embodiments, the wave gear 1 operates with a wave generator 15. The adjusting shaft 16 is identical to an inner ring of a rolling bearing 17 of the wave generator 15. Rolling elements 18, namely balls, of the rolling bearing 17, guided in a cage 19, roll on the inner ring 16. The raceway provided by the inner ring 16 for the rolling elements 18 has an elliptical, non-circular shape, as is known per se. In contrast to the inner ring 16, the associated outer ring 20 of the rolling bearing 17 is flexible, so that it permanently adapts to the non-circular shape of the inner ring 16. The outer ring 20 is surrounded by a flexible gear element 21, which in the present cases is designed as a collar sleeve.

[0030] The collar sleeve 21 has a sleeve-shaped toothed section 36 and a collar 37 adjoining it, which is connected to the drive shaft 2. An external toothing 22 located on the section 36 engages with an internal toothing 23 of the output element 3. The outer ring 20 is supported axially against a flange 26 of a sheet metal sleeve 24, which is attached to the drive shaft 2. The flange 26 is located on a cylindrical section 38 of the sheet metal sleeve 24. The sheet metal sleeve 24, like the flexible transmission element 21, has a collar shape. One collar of the sheet metal sleeve 24 is designated 25.

[0031] Due to the non-circular shape of the inner ring 16, which functions as an adjusting shaft, the internal teeth 23 mesh with the external teeth 22 only at two diametrically opposed points. Otherwise, the teeth 22 and 23 are offset from each other. A slightly different number of teeth on the various teeth 22 and 23 ensures, in a manner known in principle, that a full rotation of the adjusting shaft 16 relative to the drive element 2 is converted into only a slight pivoting motion between the two connecting shafts 2 and 3. Simultaneously, the torque acting between the connecting shafts 2 and 3 is multiplied compared to the torque of the electric motor driving the adjusting shaft 16. Overall, the wave gear 1, which includes the wave generator 15, is a non-self-locking gear.

[0032] In the exemplary embodiment according to the Fig. 6 and Fig. 7. A detent device 28 exists with which the angular relationship between the adjusting shaft 16 and the output element 3 can be fixed. On the adjusting shaft 16 side, the detent device 28 includes a sleeve 29, which in this case is located next to the bolt 14. A spring 30, acting as a compression spring, is inserted into the sleeve 29 and exerts a force on a pin 32 that is slidable within the sleeve 29. The preload of the spring 30 can be varied by means of an adjusting screw 31, which is screwed into the sleeve 29.

[0033] On the side of the pin 32 facing away from the spring 30, a ball 33 rests, which is suitable for engaging in a detent recess 34 on the end face of the pin 11. The sleeve 29, together with the spring 30, the adjusting screw 31, the pin 32, and the ball 33, forms a detent assembly.

[0034] Is the locking device 28 in the locked position, as shown in Fig.As illustrated in Figure 7, the torque generated by the electric motor driving the inner ring 16 allows the device to move out of this detent position at any time. No separate actuator is required to release the detent function. Several detent devices 28 of the type shown can be effective in any relative angular position of the connecting shafts 2, 3, for example, also in a neutral position between the two stop positions. Reference symbol list 1 three-shaft gearbox, wave gearbox 2 Drive shaft, connecting shaft 3 Output shaft, connection shaft 4 Angle Limitation 5 Locking mechanism 6 Actuating mechanism 7 Ramp on the drive shaft 8 Roof contour 9 retaining ring 10 camshaft adjusters 11 pin 12 springs 13 Stop contour 14 bolts 15 wave generator 16 Inner ring, adjusting shaft 17 rolling bearings 18 rolling elements 19 cage 20 outer ring 21 flexible gear element 22. Toothing of the flexible gear element, external toothing 23. Toothing of the output element, internal toothing 24 sheet metal sleeves 25 collars of the sheet metal sleeve 26 Edge of the sheet metal sleeve 27 Stop surface 28 Locking device 29 Sleeve 30 springs 31 Adjusting screw 32 pens 33 balls 34 Rest recess 35 sprocket 36 toothed section 37 collars 38 cylindrical section QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 105 281 A1

[0002] DE 10 2022 126 038.0

[0003] DE 10 2019 106 338 A1

[0004] DE 10 2019 132 995 A1

[0004] DE 10 2018 117 976 A1

[0004] DE 10 2014 202 060 A1

[0005]

Claims

[1] Three-shaft transmission (1), comprising two connecting shafts (2, 3), namely a drive shaft (2) and an output shaft (3), and an adjusting shaft (16) concentric to the connecting shafts (2, 3), wherein a locking mechanism (5) effective between one of the two connecting shafts (2, 3) and the adjusting shaft (16) can be activated by a relative rotation between the connecting shafts (2, 3). [2] Three-shaft transmission (1) according to claim 1, characterized by , that the locking mechanism (5) comprises a pin (11) guided in one of the connecting shafts (2, 3), which is displaceable through the other connecting shaft (3, 2) in the axial direction of the shafts (2, 3, 16) and is provided for interaction with a stop contour (13) provided on the side of the adjusting shaft (16). [3] Three-shaft transmission (1) according to claim 2, characterized by , that the pin (11) is received in a bore located in the output shaft (3). [4] Three-shaft transmission (1) according to claim 2 or 3, characterized by , that the pin (11) is located in the area of ​​an end stop acting directly between the connecting shafts (2, 3). [5] Three-shaft transmission (1) according to any one of claims 2 to 4, characterized by a detent device (28) which is formed on the one hand by the pin (11) and on the other hand by a detent assembly (29, 30, 31, 32, 33) located on the side of the adjusting shaft (16). [6] Three-shaft transmission (1) according to claim 5, characterized by , that the detent assembly (29, 30, 31, 32, 33) comprises a spring-loaded ball (33) which is designed to engage in an end-face detent recess (34) in the pin (11). [7] Three-shaft transmission (1) according to claim 5 or 6, characterized by , that the detent function of the detent device (28) can be overcome by an electric drive of the adjusting shaft (16). [8] Three-shaft transmission (1) according to any one of claims 1 to 7, characterized by, that this is designed as a wave gear (1). [9] Three-shaft transmission (1) according to claim 8, characterized by , that an inner ring of a shaft generator (15) is provided as the adjusting shaft (16). [10] Camshaft adjuster (10) comprising a three-shaft transmission (1) according to claim 1.

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