Spider

Abstract

The present invention relates to a spindle with a spindle bearing which, in the axial direction of the spindle around a shaft of the spindle, has angular contact ball bearings arranged in a housing of the spindle, a preload unit for applying an axial preload to the angular contact ball bearings and a regulator for controlling the axial preload, wherein the regulator has an expanding ring or an expanding bushing which has an outer ring forming a mass body and an inner ring on each side of the outer ring, wherein the inner rings are connected to the outer ring by means of an elastic connecting structure oriented at an obtuse angle to an inner edge of the outer ring and to an outer edge of the inner ring, and the outer ring has a radial distance to the housing.According to the invention, in the axial direction of the spindle, a first inner ring of the expanding ring or expanding bushing directly or indirectly borders a bearing inner ring of one of the angular contact ball bearings, and a second inner ring of the expanding ring or expanding bushing is directly or via a rigid driver connected to the shaft in a rotationally secured manner.

Description

[0001] The present invention relates to a spindle with a spindle bearing which has angular contact ball bearings arranged in a housing of the spindle around a shaft of the spindle in the axial direction of the spindle, a preload unit for applying an axial preload to the angular contact ball bearings and a controller for controlling the axial preload, wherein the controller has at least one expanding ring or an expanding bushing which has an outer ring which forms a mass body and an inner ring on each side of the outer ring, wherein the inner rings are connected to the outer ring via an elastic connecting structure which is aligned at an obtuse angle to an inner edge of the outer ring and to an outer edge of the inner ring, and the outer ring has a radial distance from the housing.

[0002] A spindle of this type is known from WO 96 / 18048 A2. The known spindle has a spindle bearing with several spindle bearings in the form of angular contact ball bearings, which are held under preload by a nut. To regulate the preload such that spindle corrosion does not occur even at high spindle rotational speeds, WO 96 / 18048 A2 proposes an axial expansion bushing arranged between the spindle bearings. The axial expansion bushing has two thrust rings, each of which is supported against a spindle housing via a regulator bearing. An outer bearing ring of a first regulator bearing located on a first of the thrust rings abuts an inner stop of the housing, while an outer bearing ring of a second regulator bearing located on a second of the thrust rings is connected via a spacer ring to a non-rotating outer bearing ring of a nut-side spindle bearing.

[0003] In this case, the outer circumference of each of the regulator bearings rests against the outer circumference of the respective thrust ring in the radial direction of the spindle. The second thrust ring of the axial expansion bushing, located closer to the preload unit than the first thrust ring, is connected to the spindle via a radially aligned annular diaphragm and a spacer sleeve, so that the axial expansion bushing rotates with the spindle.

[0004] The axial expansion bushing has inertial masses connected to the thrust rings by several elastic arcs between the thrust rings. Centrifugal forces act on these masses as a result of spindle rotation, causing the thrust rings to move toward each other in the axial direction of the spindle. This axial movement reduces the preload acting on the spindle bearings, causing the outer bearing ring of the nut-side spindle bearing, the control bearings, and the spacer ring to shift relative to the housing. The inner bearing rings of the spindle bearings, however, are not shifted relative to the spindle.

[0005] The known spindle has a very complex controller design with complex components that are difficult to manufacture. In particular, the arches of the axial expansion bushing are difficult to manufacture, as they must be manufactured identically to avoid imbalance. Furthermore, there is the problem that the inertial masses arranged on the arches tend to exhibit bending modes around the shaft axis, thus negatively impacting the stability of the spindle system.

[0006] It is therefore the object of the present invention to provide a spindle with a simple to manufacture and reliable controller for controlling the axial preload of spindle bearings.

[0007] This object is achieved by a spindle with a spindle bearing, which has angular contact ball bearings arranged in a housing of the spindle around a shaft of the spindle in the axial direction of the spindle, a preload unit for applying an axial preload to the angular contact ball bearings and a controller for controlling the axial preload, wherein the controller has at least one expanding ring or an expanding bushing, which has an outer ring forming a mass body, and an inner ring on each side of the outer ring, wherein the inner rings are connected to the outer ring via an elastic connecting structure aligned at an obtuse angle to an inner edge of the outer ring and to an outer edge of the respective inner ring, and the outer ring of the expanding ring or the expanding bushing has a radial distance from the housing,and wherein, in the axial direction of the spindle, a first inner ring of the expansion ring or expansion bushing directly or indirectly adjoins a bearing inner ring of one of the angular contact ball bearings, and a second inner ring of the expansion ring or expansion bushing is connected to the shaft in a rotationally secured manner directly or via a rigid driver connected to the shaft.

[0008] Unlike in WO 96 / 18048 A2, in the present invention, the first inner ring adjoins the bearing inner ring of the adjacent angular contact ball bearing not in the radial direction, but in the axial direction of the spindle. The first inner ring can directly adjoin the bearing inner ring of the adjacent angular contact ball bearing, or at least one means can be located between the first inner ring and the bearing inner ring of the adjacent angular contact ball bearing, through which force can be transmitted. Such a means can, for example, be a spacer ring located between the first inner ring and the bearing inner ring of the adjacent angular contact ball bearing.

[0009] The connecting structures between the inner and outer rings of the expansion ring or expansion bushing form a spring structure. As a result, an elastic preload is applied to the angular contact ball bearings by means of the expansion ring or expansion bushing directly adjacent to the angular contact ball bearings in the spindle according to the invention. The expansion ring or expansion bushing thus acts as a preload unit or as part of it.

[0010] Similar to the document WO 96 / 18048 A2, in the spindle according to the invention, the outer ring of the expansion ring or expansion bushing forming the mass body moves radially outwards when it rotates, whereby the inner rings of the expansion ring or expansion bushing move towards each other in the axial direction of the spindle.

[0011] The axial movement of the inner rings that occurs during spindle rotation creates freedom of movement for the bearing inner ring of the angular contact ball bearing directly adjacent to the first inner ring, as well as for the bearing inner rings of the other angular contact ball bearings adjacent to this angular contact ball bearing, in the axial direction of the spindle. This allows the expansion ring or expansion bushing to vary the preload acting on the angular contact ball bearings depending on centrifugal force. The expansion ring or expansion bushing is capable of compensating for the relative displacement of the bearing rings of the spindle's angular contact ball bearings at high speeds.

[0012] Again, unlike in WO 96 / 18048 A2, the inner rings of the angular contact ball bearings slide on the shaft during this axial movement. This results in a shearing movement of the inner rings relative to the outer rings of the angular contact ball bearings. The angular contact ball bearings arranged to the side of the first inner ring are directly adjacent to one another, thus forming a group of angular contact ball bearings whose inner rings can all move axially when the spindle rotates, causing axial movement of the inner rings of the expansion ring or expansion bushing, in order to compensate for the axial preload on the angular contact ball bearings.

[0013] The spindle according to the invention therefore eliminates the need for complex force redirection to enable axial movement of the angular contact ball bearings during spindle rotation, thus regulating the axial preload on the angular contact ball bearings. This, in turn, results in an extremely short response time, which places significantly less stress on the angular contact ball bearings than is the case with the spindle described in WO 96 / 18048 A2.

[0014] In the spindle according to the invention, the connection of the second inner ring to rotating parts of the spindle is also solved much more simply and mechanically more stable than in the document WO 96 / 18048 A2. While in the device of the document WO 96 / 18048 A2 the second thrust ring is connected to the shaft via an elastic annular diaphragm, in the spindle according to the invention the second inner ring is connected to the shaft directly or via a rigid driver. This results in optimal power transmission between the shaft and the expansion ring or expansion bushing in the present invention, without unnecessary vibrations. Furthermore, the spindle according to the invention dispenses with the annular diaphragm used in the power transmission path, which can easily break in this position.

[0015] The spindle according to the invention can be used, for example, in machine tools.

[0016] In a preferred embodiment of the spindle according to the invention, the connecting structure is an annular diaphragm. Unlike in the document WO 96 / 18048 A2, in which a plurality of spaced-apart arcs are used to connect the laterally arranged pressure rings to the centrally arranged inertial mass, this embodiment uses two preferably mirror-symmetrical annular diaphragms that connect the two laterally arranged inner rings to the centrally arranged outer ring. Since obtuse angles are formed between the annular diaphragms and the inner edge of the outer ring as well as with the outer edge of the inner rings, the annular diaphragms are funnel-shaped. The annular diaphragms are thus closed around their circumference, in contrast to the arcs known from the prior art. This significantly reduces the risk of breakage.In addition, the production of the two membranes is significantly less complex and less susceptible to tolerance errors than that of conventional arches. Due to the closed ring structure of the connecting structures, no parasitic natural vibration modes of individual masses occur during the rotation of the expansion ring or expansion bushing, and the expansion ring or expansion bushing can be manufactured with a high balance quality due to their preferably monolithic construction.

[0017] Particularly high stability of the expansion ring or expansion bushing is achieved when the expansion ring or expansion bushing is monolithic, i.e., without welds or the like and without individual mass elements. Individual mass elements, such as those used in WO 96 / 18048 A2, can cause parasitic natural vibration modes and thus compromise the stability of the spindle.

[0018] It is particularly advantageous in the spindle according to the invention if the expansion ring or expansion bushing is not supported by one or more ball bearings. This makes the design of the spindle according to the invention significantly simpler and the force distribution significantly more effective than is the case, for example, in the spindle of WO 96 / 18048 A2.

[0019] A particularly high mechanical strength of the expander ring or expander bushing is achieved when the transition areas between the respective connecting structure and the respective inner ring, as well as between the respective connecting structure and the outer ring, are rounded. This ensures that the connecting structure remains firmly attached to the inner and outer rings, even under high centrifugal forces. Furthermore, the rounding reduces the maximum component stresses.

[0020] Even though in principle the respective obtuse angle between the connecting structure and the inner rings as well as the outer ring can each assume any value between 90° and 180°, it has proven particularly advantageous if the respective obtuse angle is between 110° and 170°, preferably between 110° and 150°, particularly preferably between 110° and 130°.

[0021] Preferred embodiments of the present invention, their structure, function and advantages are explained in more detail below with reference to figures, wherein Fig. 1 schematically shows an embodiment of a spindle according to the invention in a sectional side view; Fig. 2 schematically shows an expanding ring of a spindle according to the invention in a perspective view; Fig. 3 schematically shows an expansion ring of a spindle according to the invention in a sectional side view; Fig. 4 schematically shows the expansion ring Fig. 3 with forces acting thereon during a rotational movement of the spindle according to the invention; and Fig. 5 schematically shows a further embodiment of a spindle according to the invention in a sectional side view.

[0022] Fig. Figure 1 schematically shows an embodiment of a spindle 1 according to the invention in a cross-sectional view. For the sake of simplicity, only one side of the spindle 1 is shown here, starting from a rotational axis R of the spindle 1, with the opposite side of the spindle 1 being mirror-symmetrical thereto. The orientation of the rotational axis R is equal to or parallel to an axial direction A of the spindle 1.

[0023] The spindle 1 has a shaft 2 rotatable about the rotation axis R. A tool holder 3 is formed at a front end of the shaft 2. A spindle bearing of the spindle 1 is arranged between the shaft 2 and a housing 4 of the spindle 1.

[0024] The spindle bearing has a first bearing package with a plurality of angular contact ball bearings 51, 52, 53, 54 in a front region of the spindle 1. Furthermore, the spindle bearing has a second bearing package with angular contact ball bearings 58, 59 in a rear region of the spindle 1. The angular contact ball bearings 51, 52, 53, 54, 58, 59 are arranged around the shaft 2 in the housing 4. The angular contact ball bearings 51, 52, 53, 54 are directly adjacent to one another in the axial direction A, and the angular contact ball bearings 58, 59 are also directly adjacent to one another in the axial direction A.

[0025] The angular contact ball bearings 51, 52, 53, 54 each have an inner bearing ring 55 and an outer bearing ring 56, between which balls 57 are inserted. The respective outer bearing ring 56 of the angular contact ball bearings 51, 52, 53, 54 is fixedly mounted in the housing 4. The respective inner bearing ring 55 is movable in the axial direction A.

[0026] In the embodiment of Fig. 1, the outer bearing rings 56 of the angular contact ball bearings 58, 59, i.e., the second bearing assembly, are not firmly fixed to the housing 4. Furthermore, a disc spring arrangement 60 is arranged adjacent to the angular contact ball bearing 58 in the axial direction A.

[0027] The spindle 1 is a motor spindle. Therefore, a rotor 91 and a stator 92 are provided between the first and second bearing assemblies on the shaft 2. However, in other embodiments of the present invention (not shown), the spindle according to the invention can also have a different drive principle.

[0028] The spindle 1 further comprises a nut 6, with which a preload is applied to the angular contact ball bearings 51, 52, 53, 54 of the spindle bearing.

[0029] An expansion ring 7 is directly adjacent to one of the angular contact ball bearings 51. The expansion ring 7 forms both a preload unit for generating an elastic preload on the angular contact ball bearings 51, 52, 53, 54 of the spindle 1 and a controller for regulating the axial preload on the angular contact ball bearings 51, 52, 53, 54. Instead of the expansion ring 7, in other embodiments of the present invention, an expansion bushing, which has a longer axial extension than the expansion ring 7, can also be used.

[0030] The expansion ring 7 has, in the axial direction A, in the following order, next to one another and connected to one another: a first inner ring 71, a first connecting structure 72, an outer ring 73, a second connecting structure 74, and a second inner ring 75. In the embodiment shown, the expansion ring 7 is monolithic. In principle, however, it is also possible for the outer ring 73, which acts as a mass body, to be formed from several interconnected parts. The inner rings 71, 75 and / or the outer ring 73 can also be formed from at least two rings connected to one another in the axial direction A or in the radial direction. The shape of the cross-section of the outer ring 73, which acts as a mass body, is largely variable.

[0031] For example, the expansion ring 7 can be made of spring steel or high-alloy steel.

[0032] The two inner rings 71, 75 each have an outer diameter that is smaller than the outer diameter of the outer ring 73 arranged between the inner rings 71, 75. In the embodiment shown, the outer diameter of the two inner rings 71, 75 is the same, but can also be different in other embodiments of the present invention. Furthermore, in the embodiment shown, the outer diameters of the two inner rings 71, 75 are smaller than the inner diameter of the outer ring 73. In other embodiments of the present invention (not shown), however, the inner diameter of the outer ring 73 can also be moved inward so far that it is smaller than the outer diameters of the inner rings 71, 75.

[0033] The outer ring 73 has a radial distance from the housing 4.

[0034] The connecting structures 72, 74 are arranged on both sides of the outer ring 73 and connect the inner rings 71, 75 to the outer ring 73, respectively. In the embodiment shown, the connecting structures 72, 74 are each circumferential, funnel-shaped or V-shaped annular membranes. The connecting structures 72, 74 are elastic, i.e., their movement is reversible. This means that they can be moved toward each other in the axial direction A and relax back to their original position when no further force acts on them in the axial direction A. The connecting structures 72, 74 are mirror-symmetrical to each other.

[0035] Each of the connecting structures 72, 74 encloses an obtuse angle α, α' with an inner edge 77 of the outer ring 73 and with an outer edge 76, 78 of one of the inner rings 71, 75.

[0036] The expansion ring 7 is not supported by a ball bearing.

[0037] In the axial direction A of the spindle 1, the first inner ring 71 of the expander ring 7 directly adjoins the bearing inner ring 55 of one of the angular contact ball bearings 51. The second inner ring 75 of the expander ring 7 is connected to the shaft 2 in a rotationally secured manner via a rigid driver 8 connected to the shaft 2. In the embodiment shown, the driver 8 is a driver ring, but can also be another suitable driver. The connection between the second inner ring 75 and the driver 8 can be established, for example, by a toothing. However, any shaft-hub connection can be used for the connection. Furthermore, the second inner ring 75 can also be coupled directly to the shaft 2, for example, via a toothing.

[0038] Fig. Figure 2 schematically shows a perspective view of an expander ring 7 that can be used, for example, in the spindle according to the invention. The above description applies to the expander ring 7.

[0039] Fig. Figure 3 schematically shows a sectional side view of an expander ring that can be used in the spindle according to the invention. The above description of the expander ring 7 also applies here. In the expander ring 7 shown, transition areas 79, 80 between the respective connecting structure 72, 74 and the respective inner ring 71, 75, as well as between the respective connecting structure 72, 74 and the outer ring 73, are rounded.

[0040] Fig. 4 shows the expansion ring 7 from Fig. 3 with prestressing forces F acting on it V These are reduced as a result of a rotation of the spindle 1. The deformation in the radial direction V is also shown schematically using arrows. rad and the deformation in the axial direction V ax of the expansion ring 7.

[0041] The spindle 1 according to the invention operates as follows: The expansion ring 7 serves to generate preload for the fixed bearing arrangement. As the speed of the shaft 2 increases, the inner bearing rings 55 of the angular contact ball bearings 51, 52, 53, 54 move in such a way that the elastically adjusted bearings would have to withstand additional preload forces. During the rotation of the shaft 2, the expansion ring 7 is moved by its coupling with the shaft 7 via the driver 8. Due to the centrifugal force acting in particular on the outer ring 73 of the expansion ring 7, which functions as a mass body, during the rotation of the spindle 1, the outer ring 73 moves radially outward, as indicated by the arrow V. rad schematically in Fig. 4. At the same time, the elastic connecting structures 72, 74 are moved towards each other in the axial direction, as shown by the arrows V ax in Fig. 4. This means that the inner rings 71, 75 are subjected to lateral forces F V, which also moves the inner rings 71, 75 toward each other. This creates space in the axial direction A for the bearing inner rings 55 of the angular contact ball bearings 51, 52, 53, 54, so that the bearing inner rings 55 can move in the axial direction A toward the first inner ring 71.

[0042] There is a quadratic relationship between the axial displacement of the bearing inner rings 55 and the speed of spindle 1.

[0043] The outer radii on the inner rings 71, 75 and on the outer ring 73, the inner radii between the respective connecting structure 72, 74 and the outer ring 73, the inner radii between the respective connecting structure 72, 74 and the inner rings 71, 75 and the membrane thickness of the connecting structures 72, 74, together with the respective angle α, α' between the connecting structures 72, 74 and the inner rings 71, 75 and the outer ring 73, define the stiffness behavior of the expansion ring 7. The dimensions and the material of the outer ring 73 additionally define the centrifugal force-dependent deformation behavior of the expansion ring 7, as described in Fig. 4 is shown schematically. The thickness of the membranes of the connecting structures 72, 74 has a decisive influence on the axial stiffness of the expansion ring 7. If this is too high, higher centrifugal forces are required, for example, by enlarging the mass body.

[0044] If membranes that are too thin are used as connecting structures 72, 74, these can in turn lead to high component stresses and thus to strength problems.

[0045] Fig. Figure 5 schematically shows a further embodiment of a spindle 1' according to the invention in a cross-sectional view. The spindle 1' is identical to the spindle 1 of Figure 1 except for the position of the expansion ring 7, the disc spring arrangement 60 not present on the second bearing assembly, and the fixing of the outer bearing rings 56 of the angular contact ball bearings 58, 59 to the housing 4. Fig. 1, which is why reference is made here to the above description of spindle 1 with regard to the unchanged features.

[0046] In contrast to spindle 1 from Fig. 1 excludes spindle 1' Fig. 5, the expansion ring 7 is directly connected to one of the angular contact ball bearings 59 in the rear area of ​​the spindle 1'. The expansion ring 7 is designed as described above. The expansion ring 7 forms both a preload unit for generating an elastic preload on the angular contact ball bearings 59, 58 of the spindle 1' and a regulator for regulating the axial preload on the angular contact ball bearings 59, 58. Instead of the expansion ring 7, an expansion bushing can also be used here.

[0047] In the axial direction A of the spindle 1', the first inner ring 71 of the expansion ring 7 directly adjoins the bearing inner ring 55 of one of the angular contact ball bearings 59. The second inner ring 75 of the expansion ring 7 is rotatably connected to the spindle shaft 2 via an inelastic driver 8 connected to the spindle shaft 2. In the embodiment shown, the driver 8 is a driver ring, but can also be another suitable driver. The connection between the second inner ring 75 and the driver 8 can also be established here, for example, by a gearing. However, any shaft-hub connection can be used for the connection. Furthermore, the second inner ring 75 can also be directly coupled to the spindle shaft 2, for example, via a gearing.

[0048] In the present invention, the expansion ring 7 can be inserted in the force flow in front of or behind the angular contact ball bearings 51, 52, 53, 54, 58, 59, depending on the load direction, so that it reduces the preload at high speeds. As can be seen from the spindle 1, 1' in the Fig. 1 and Fig. As can be seen in Figure 5, the position of the expansion ring 7 is independent of the bearing arrangement used.

[0049] In a further embodiment, not shown, an expanding ring 7 can be arranged before and after each respective bearing assembly of angular contact ball bearings. In such an embodiment of the invention, an expanding ring is provided depending on the load direction, with which the preload applied to the angular contact ball bearings can be reduced. QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] WO 96 / 18048 A2 [0002, 0008, 0010, 0012, 0013, 0014, 0016, 0017, 0018]

Claims

[1] Spindle (1, 1') with a spindle bearing which has angular contact ball bearings (51, 52, 53, 54, 58, 59) arranged in a housing (4) of the spindle (1, 1') around a shaft (2) of the spindle (1, 1') in the axial direction (A) of the spindle (1, 1'), a preload unit for applying an axial preload to the angular contact ball bearings (51, 52, 53, 54, 58, 59) and a controller for controlling the axial preload, wherein the controller has at least one expanding ring (7) or an expanding bushing which has / which has an outer ring (73) which forms a mass body, and an inner ring (71, 75) on each side of the outer ring (73), wherein the inner rings (71, 75) are each connected to the outer ring (73) via a connection formed at an obtuse angle (α, α') elastic connecting structure (72, 74) aligned with an inner edge (77) of the outer ring (73) and with an outer edge (76, 78) of the respective inner ring (71, 75) are connected to one another, and the outer ring (73) has a radial distance from the housing (4),, characterized by that in the axial direction (A) of the spindle (1, 1') a first inner ring (71) of the expansion ring (7) or of the expansion bushing directly or indirectly adjoins a bearing inner ring (55) of one of the angular contact ball bearings (51, 59), and a second inner ring (75) of the expansion ring (7) or of the expansion bushing is connected to the shaft (2) in a rotationally secured manner directly or via a rigid driver (8) connected to the shaft (2). [2] Spindle according to claim 1, characterized by that the connecting structure (72, 74) is an annular membrane. [3] Spindle according to one of the preceding claims, characterized by that the expansion ring (7) or the expansion bushing is monolithic. [4] Spindle according to one of the preceding claims, characterized by that the expansion ring (7) or the expansion bushing is not supported by one or more ball bearings. [5] Spindle according to one of the preceding claims, characterized bythat transition areas (79, 80) between the respective connecting structure (72, 74) and the respective inner ring (71, 75) as well as between the respective connecting structure (72, 74) and the outer ring (73) are rounded. [6] Spindle according to one of the preceding claims, characterized by that the respective obtuse angle (α, α') is between 110° and 170°. [7] Spindle according to one of the preceding claims, characterized by that the inner rings (71, 75) and / or the outer ring (73) is / are formed from at least two rings connected to one another in the axial direction (A) or in the radial direction.

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