Universal shaft

Abstract

The invention relates to a cardan shaft having a shaft element and a coupling element which can be pivoted relative to the shaft element by means of an articulated connection. The articulated connection has a plurality of rolling bodies distributed in the circumferential direction, which engage both with a first recess of the shaft element and with a second recess of the coupling element when the shaft element is coupled to the coupling element in a rotationally fixed form-fitting manner, the shaft element can be tilted relative to the coupling element, and the shaft element and the coupling element are connected to each other in a substantially rotationally fixed manner. According to the invention, the shaft element has a flange designed directly with the first recess. The flange is further provided with a plurality of windows distributed in the circumferential direction, and fixing elements are arranged in the windows in a protruding mode and used for being further connected with the coupling elements.

Description

Technical Field

[0001] This invention relates to a universal joint, particularly a compensating shaft, suitable for high-speed applications. Therefore, it is also referred to as a "high-speed" universal joint. Background Technology

[0002] Compensating shafts are used to compensate for misalignment between two rotating shafts. This misalignment can occur radially, angularly, or in a combination thereof. Compensating shafts typically have two joints because a single joint can only compensate for angular misalignment. To also compensate for radial misalignment, two universal joints (i.e., a universal joint with two joints) are required. A common application example of compensating shafts is the universal joint in vehicle axles.

[0003] The applicant manufactures gearboxes for high-speed applications, particularly in the development and testing fields. In most of these applications, measuring devices are mounted on the high-speed shaft to measure or monitor torque and power. This involves two possible configurations, as detailed below. Figure 1 and 2 The image illustrates these two possible structures using existing technology. Either ( Figure 1 The measuring unit 103, located between the driver 101 and the test sample 102, is connected to the driver 101 and the test sample 102 respectively via two connectors / universals 104; or ( Figure 2 The measuring flange 203 and test sample 202 are connected via a connector or universal joint 204, and the measuring flange is directly coupled to the drive. Since the connector / universal joint 204 is not separately supported, no other connector / universal joint is required besides this bearing. This simplifies the structure and improves accuracy by eliminating the bearing point. However, according to... Figure 2 A simpler structure is limited in speed range because the measuring flange 203 and universal joint 204 are typically quite heavy; otherwise, the overhanging mass would generate the natural frequency of rotor dynamics within the operating range. Therefore, for high speeds, two aspects are particularly important: the universal joint should be as light as possible, and its center of gravity should be as close as possible to the connection point (and thus to the nearest bearing point).

[0004] In order to achieve the highest possible rotational speed, not only the absolute mass of the universal joint (in order to require less acceleration energy) but also, most importantly, its mass distribution (to prevent imbalance and bending natural frequency), and especially its connection with the measuring flange and test sample, are very important. Summary of the Invention

[0005] Therefore, the objective of this invention is to manufacture a universal joint that reduces overall weight and optimizes weight distribution for high rotational speeds. In particular, the goal is to bring the center of gravity as close as possible to the bearing point.

[0006] According to the present invention, this objective is achieved through the extremely slender design of the joint of the universal joint and the fixed design of the universal joint on the threaded connection surface, which places the center of gravity close to the bearing point.

[0007] In particular, the present invention provides a universal joint having a shaft element and a coupling element pivotable relative to the shaft element by means of a hinged connection. The hinged connection has a plurality of rolling elements distributed circumferentially. The rolling elements engage with both a first notch of the shaft element and a second notch of the coupling element when the shaft element and the coupling element are coupled in a rotationally anti-rotational form-locking manner. According to the invention, the shaft element has a flange with the first notch directly designed into it. The flange also has a plurality of windows distributed circumferentially, each window having a protruding fixing element defined for further connection of the coupling element.

[0008] The rolling elements, shaft element, and coupling element are located approximately in the same plane, the normal of which extends along the axial direction of the universal joint. This allows the shaft element to tilt (slightly) relative to the coupling element while both roll on the rolling elements. Compared to the prior art, the universal joint is fixed through the movable joint portion of the universal joint, instead of having the helical connection located outside the hub and thus outside the universal joint as in the prior art. This allows the diameter of the rolling circle (on which the rolling elements are arranged) to be larger than the diameter of the helical connection. The larger rolling circle results in improved bearing stability and thus higher rotational speeds. Furthermore, mass imbalance in the inner part of the fixed element, i.e., closer to the axis of rotation, has less impact on potential imbalances because the distance from the axis of rotation is kept small. Such mass imbalance can never be completely avoided due to manufacturing tolerances, etc.

[0009] Preferably, the fixing element is a screw element, which is further preferably made of lightweight metal, high-strength steel, or fiber-reinforced plastic. In principle, fixing can also be achieved by other means, such as locking devices like snap-fits, or theoretically by force-transmitting locking, such as by magnetism, friction (where a normal force can be applied by clamping, as occurs in screwing), or by adhesive / cohesive forces (gluing), welding, riveting, brazing, etc. However, the latter method results in a connection that cannot be loosened without damage, which is particularly unsuitable for replacing test structures, and friction and magnetism are almost ineffective at absorbing the reaction forces that arise at high speeds. Snap-fits require complex and specialized designs, which are unlikely to offer any advantages in use; accidental loosening during operation can lead to imbalance and even the risk of component ejection and injury. A screw connection, on the other hand, is a proven, inexpensive, and loosely repositionable connection with sufficient strength, and is therefore the preferred choice in this case.

[0010] Furthermore, threaded connections are preferably made via bushings passing through the shaft flange. This allows for thinner or flatter shaft flanges, resulting in weight reduction, and also brings the structure's center of gravity closer to the hub. This further reduces vibration. Additionally, the bushings ensure clearance between the shaft elements and coupling elements, as they do not need to be in contact with each other. These bushings are preferably made of steel, light metals, or fiber-reinforced plastics. If the bushings are made of light metals, such as aluminum or titanium, or plastics, especially fiber-reinforced plastics, the overall weight is further reduced compared to steel bushings. This further reduces the rotational inertia and potential imbalances of the structure.

[0011] The aforementioned rolling element is preferably a ball. The universal joint component supported on the ball can effectively compensate for angular misalignment of the structure. Furthermore, balls are inexpensive and are available in a variety of sizes, making this preferred structure highly scalable.

[0012] Furthermore, the shaft element and the coupling element are preferably connected by a clamping device that surrounds the flange of the shaft element and is fastened to the coupling element by means of another fixing device. In this case, the clamping device is preferably fastened to the coupling element by means of screws as fixing devices and is supported by a bushing.

[0013] In a particularly preferred embodiment, the universal joint is designed as a constant velocity universal joint. This ensures uniform transmission of rotational motion and thus prevents torsional vibration from occurring through the universal joint. Attached Figure Description

[0014] Figure 1 A diagram illustrating the system structure according to the first prior art is shown; Figure 2 A diagram illustrating the system structure according to a second prior art upon which the present invention is based is shown; Figure 3 The universal joint according to the invention is shown in equidistant sectional views; Figure 4 An embodiment of the invention is shown in an exploded view; Figure 5 A cross-sectional view shows the assembled shaft portion according to the invention; and Figure 6 The behavior of the universal joint according to the invention under torque introduction is shown. Detailed Implementation

[0015] Embodiments of this disclosure will now be described with reference to the accompanying drawings.

[0016] Figure 1The diagram schematically illustrates a (conventional) test structure on a test bench. A drive 101 is supported in a housing 101A by a bearing 101B, and the opposing test sample 102 is similarly supported in a housing 102A by a bearing 102B. A measuring unit 103, located between the test sample 102 and the drive 101, is supported in a housing or frame 103A by a bearing 103B. A coupling 104 is provided not only between the drive 101 and the measuring unit 103 but also between the measuring unit 103 and the test sample 102, enabling a (largely) torsional-resistant connection between the respective components, while compensating for angles and, if necessary, length. "Largely" torsional resistance means that even slight (rotational) play is possible, for example, when reversing the drive direction.

[0017] Figure 2 A schematic test structure for a universal joint with shaft element 204 is shown, where no additional bearing point is required for the measuring unit. In principle, this structure could also have a conventional universal joint, but would suffer from the problems described in the prior art. Specifically, the structure includes: a driver 201 with bearing 201B within housing 201A; a test sample 202 with bearing 202B within housing 202A; shaft element 204; and a measuring flange 203 directly positioned between shaft element 204 and driver 201. Figure 1 Compared to the structure shown, by according to Figure 2 The structure can omit frame 103A and associated bearing 103B. Fixed connections between driver 201 and measuring flange 203, between measuring flange 203 and shaft element 204, and between shaft element 204 and test sample 202 allow for more stable force transmission than with coupling 104, which is why measuring flange 203 and shaft element 204 do not need separate supports. Similar to bearing 103B, the absence of bearings also helps reduce the mass to be accelerated and potential imbalances at desired high speeds.

[0018] As described above, in this existing structure, the rotational speed is still limited due to the large mass of the measuring flange and universal joint, and the resulting imbalance during rapid rotation. This is precisely where the present invention comes in, such as... Figures 3 to 6 As shown below, a more detailed explanation will follow.

[0019] Figure 3 A three-dimensional cross-section of the universal joint according to the invention of the shaft element 4 on the measuring flange (not shown) is schematically shown.

[0020] Figure 4 The design of the universal joint according to the invention is shown in an exploded view, and Figure 5The assembly design is shown in cross-section. The flange hub 2 according to the invention is implemented in a flat configuration. This reduces weight and brings the center of gravity closer to the threaded connection surface. Specifically, the shaft flange 4A of the shaft element 4 is provided with through holes or windows 4B through which screws 3 can be guided as fixing elements to the bushing 5. The bushing 5 provides the necessary stability to reliably guide the threaded connection in the shaft flange 4A, which is thinner than in the prior art. The bushing 5 is preferably made of steel, but in some cases it can be made of, for example, a light metal or fiber-reinforced plastic to further reduce weight. The ball bearing 6 functions similarly to the ball body 6 described above, and the ball bearing is received in a separate recess 4C in the shaft flange 4A. In other words, the ball bearing 6, as a rolling element, forms a hinged connection with the flange hub 2 and the recess 4C located on the shaft flange 4A of the shaft element 4. The ball bearing 6, flange hub 2, and shaft flange 4A are preferably clamped together to create a backlash-free design. If torque is transmitted directly through this backlash-free arrangement, the universal joint will function as a constant velocity universal joint. Screw 3 is used to screw the entire design onto a drive flange (not shown here), such as the drive flange of driver 201. Clamping device 7 is screwed onto hub portion 2 and placed on bushing 5 by additional screws 8 (which act as fixing devices). Thus, clamping device 7 engages shaft flange 4A and prevents shaft flange 4A from detaching from hub portion 2. Although shaft flange 4A is secured by bushing 5 against which clamping device 7 rests, a slight gap remains, allowing shaft flange 4A to tilt on rolling elements 6. This ensures angular mobility (and, when mounted on both sides of the driver and test sample, ensures flexibility of the shaft element).

[0021] Since no strong force is applied to the clamping device 7 in the axial direction of the structure during testing, it can be screwed onto the thin hub portion 2 with relatively few, smaller, and lighter screws 8. This further reduces the weight of the structure, especially on the outer periphery, compared to existing technologies.

[0022] According to the structure of the present invention, the fixed threaded connection with screws 3 is arranged within the diameter in which the balls 6 run. Therefore, the relatively heavier screws 3 are positioned closer to the central axis of the shaft, resulting in less imbalance due to potential mass differences between similar screws caused by manufacturing tolerances and other factors compared to the prior art. Furthermore, the overall mass inertia is reduced due to the possible thin-profile implementation of the flange and the use of bushings 5. The center of gravity of the universal joint is closer to the hub, and thus closer to the bearing point, thereby better absorbing any remaining imbalances. As a result, universal joints and test structures for higher speeds can be manufactured compared to the structures described in the prior art.

[0023] Figure 6 The behavior of the universal joint according to the invention under torque introduction is shown. Figure 6 As can be seen from the arrows shown on the rolling elements, when torque is introduced through the shaft flange 4, the torque is pressed onto the rolling elements 6 located between the shaft flange 4 and the hub portion 2. From Figure 6 It can also be seen that these rolling elements 6 can be arranged without clearance between the shaft flange 4 and the hub portion 2. Therefore, in the embodiment shown here, the torque introduced through the shaft flange 4 acts directly on the hub portion 2 through the rolling elements 6. The introduced torque is thus directly transmitted. At the same time, it is clearly shown at the bushing 5 that the bushing 5 is supported on the hub portion 2, but as Figure 5 The image clearly shows that the clearance is smaller compared to the bushing 4. Furthermore, the bushing around the bushing has a small clearance and is relatively thin. This allows the bushing 4 to tilt relative to the bushing 5, thereby achieving an angular offset between the bushing 4 and the hub portion 2. Furthermore, the structural mass and thus the inertial forces are further reduced. Simultaneously, even in the tilted state, the aforementioned prestress maintains the force-transmitting lock between the bushing 4 and the hub portion 2 through the rolling elements 6. This arrangement further reduces mass while maintaining the same stability.

[0024] In summary, the present invention provides a universal joint having a shaft element 4 and a coupling element 2 pivotable relative to the shaft element 4 by means of a hinged connection. The hinged connection includes the coupling element 2, a notch 4C of the shaft element, and a plurality of rolling elements 6 distributed circumferentially. These rolling elements engage with both the first notch 4C of the shaft element 4 and the second notch of the coupling element 2 in a rotationally anti-rotationally form-locking coupling, thereby tilting the shaft element 4 relative to the coupling element 2, and connecting the shaft element 4 and the coupling element 2 substantially torsionally. According to the invention, the shaft element 4 has a flange 4A with the first notch 4C directly designed into it. The flange 4A also has a plurality of windows 4B distributed circumferentially, each window having a protruding fixing element 3 defined for further connection of the coupling element 2.

Claims

1. A universal joint having a shaft element (4) and a coupling element (2) pivotable relative to said shaft element (4) by means of a hinged connection (2, 4C, 6), wherein, The hinged connection includes the coupling element (2), the notch (4C) of the shaft element (4), and a plurality of rolling elements (6) distributed in the circumferential direction. The rolling elements engage with both the first notch (4C) of the shaft element (4) and the second notch of the coupling element (2) when the shaft element (4) and the coupling element (2) are coupled in a form-locking manner against rotation, thereby enabling the shaft element (4) to tilt relative to the coupling element (2), and the shaft element (4) and the coupling element (2) to be connected to each other against torsion. The shaft element (4) has a flange (4A) with the first notch (4C) directly designed, wherein the flange (4A) also has a plurality of windows (4B) distributed in the circumferential direction, and each window has a fixing element (3) protruding for further connecting the coupling element (2).

2. The universal joint according to claim 1, wherein, At least one fixing element (3) is a screw (3).

3. The universal joint according to claim 2, wherein, The screw (3) is made of a light metal.

4. The universal joint according to any one of claims 1 to 3, wherein, The flange (4A) is fixed to the coupling element by a screw (3) that is guided through the flange (4A) into the bushing (5).

5. The universal joint according to claim 4, wherein, The bushing (5) is made of light metal.

6. The universal joint according to any one of claims 1 to 3, wherein, The rolling element (6) is a ball.

7. The universal joint according to any one of claims 1 to 3, wherein, The shaft element (4) and the coupling element (2) are connected by a clamping device (7) surrounding the flange (4A) of the shaft element (4) and fastened to the coupling element (2) by means of another fixing device (8).

8. The universal joint according to claim 7, wherein, The clamping device (7) is fastened to the coupling element (2) by means of screws (8) and supported by the bushing (5).

9. The universal joint according to any one of claims 1 to 3, wherein, The universal joint (1) is designed as a constant velocity universal joint.

10. The universal joint according to any one of claims 1 to 3, wherein, The coupling between the shaft element (4) and the coupling element (2) through the anti-rotation shape locking of the rolling element (6) is generated by prestress, which clamps the coupling element (2) onto the shaft element (4) through the rolling element (6).

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