Speed ​​reduction device

Abstract

Speed ​​reduction device (10) comprising the following: a case (31, 58), wherein a single centering collar connection surface (17, 17A, 17B) is provided in the housing (31, 58), wherein a component (54) of a front stage side of the speed reduction device (10) and a component (50, 15) of a rear stage side of the speed reduction device (10) are fitted onto the individual centering collar connecting surface (17, 17A, 17B) in a centering manner, and wherein the component (50, 15) of the rear stage side is a component of a connected machine (15) which is to be driven by the speed reduction device (10).

Description

BACKGROUND OF THE INVENTION Area of ​​the invention

[0001] The present invention relates to a speed reduction device. Description of the related technique

[0002] A speed reduction device comprising an output side housing as a housing part is disclosed in JP 2011-052785 A. Centering collar parts are formed on an outer circumference of the end part of the output side of the output side housing and on an inner circumference of an end part of an input side thereof. A connected machine is fitted together as a lateral element of the rear or next stage in a centering manner or via a centering collar with the centering collar part on the outer circumference of the end part of the output side. An input side housing as a lateral element of the front stage is fitted together in a centering manner with the centering collar connecting part on the inner circumference of the end part of the input side.

[0003] In the housing of the speed reduction device according to JP 2011-052785 A, the centering collar connecting part, onto which the component of the rear stage side is fitted, is formed on the outer circumference of the output side end part, and the centering collar connecting part, onto which the component of the front stage side is fitted, is formed on the inner circumference of the input side end part. Therefore, it is necessary to machine both centering collar connecting parts separately. This results in problems such as the difficulty of precisely aligning the wheel centers of the front stage side and rear stage side components, leading to higher machining costs.

[0004] Furthermore, DE 11 68 198 B discloses an eccentric gear with pin extensions, consisting of a ring gear fixed in the gear housing, a roller wheel provided with bores and mounted on a drive eccentric, and an output shaft mounted on both sides of the roller wheel, which receives rollers in the bores of its flanges which engage in the bores of the roller wheel, wherein the diameter of the bores of the flanges and of the roller wheel is equal to the outside diameter of the rollers plus the drive eccentricity. Summary of the invention

[0005] The invention was made to solve such problems in the prior art. The object of the present invention is achieved by speed reduction devices according to claims 1 and 5. The dependent claims relate to preferred embodiments of the invention.

[0006] One objective of the invention is to provide a speed reduction device that enables the precise alignment of the wheel centers of a component on the front stage side and a component on the rear stage side, which are connected to each other via the speed reduction device, and thus reduces machining costs. To solve the problems described above, a speed reduction device is provided which has a housing in which a single centering collar connection surface is provided, and both a component on the front stage side of the speed reduction device and a component on the rear stage side of the speed reduction device are fitted onto the single centering collar connection surface in the manner of a pin and collar or centering collar, respectively.

[0007] According to the invention, these components are configured such that both the front-stage component and the rear-stage component of the speed reduction device fit together in a centering manner with the single centering collar connection surface formed in the housing of the speed reduction device. This makes it possible to precisely align the wheel centers of the front-stage component and the rear-stage component due to the shared use of the centering collar connection surface. Additionally, machining costs are reduced because the machining operation only needs to be performed once.

[0008] To solve the problems described above, a speed reduction device is provided, which has a housing in which two centering flange connection surfaces are formed at a distance from each other. Additionally, the two centering flange connection surfaces have the same diameter, and a portion of the area between the two centering flange connection surfaces whose diameter is larger than that of the centering flange connection surface is not present.

[0009] According to the invention, it is possible to precisely align the wheel centers of a component of the front stage side and a component of the rear stage side, which are connected to each other via a speed reduction device, and to achieve a reduction in machining costs. Brief description of the drawings Fig. Figure 1 is a cross-sectional view showing a configuration of a speed reduction device according to an example of an embodiment of the invention. Fig. Figure 2 is a partially enlarged cross-sectional view of the speed reduction device, showing a part indicated by arrow II. Fig. 1 is displayed. Fig. Figure 3 is a cross-sectional view showing a configuration of a speed reduction device according to an example of a further embodiment of the invention. Detailed description of the invention

[0010] The following describes details of a speed reduction device according to an example of an embodiment of the invention with reference to the accompanying drawings.

[0011] First, the entire configuration of a speed reduction device 10 is schematically described with reference to Fig. 1 described.

[0012] The speed reduction device 10 is a speed reduction device having a speed reduction mechanism 11 of an eccentrically oscillating type. The speed reduction device 10 is used in such a way that it slows the rotation of a motor shaft 13A of a motor 13 and drives a driven body (not shown) of an attached machine 15 (the full description of which is not given here). A detailed configuration of the connection between the speed reduction device 10, the motor 13, and the attached machine 15 via a centering collar connection surface 17 is described below.

[0013] An input shaft 12 of the speed reduction device 10 is formed by a hollow shaft having a hollow section 12A. The input shaft 12 is connected to the motor shaft 13A of the motor 13 via a spring 12B. The eccentric bodies 14 and 16 are integrally formed in the input shaft 12.

[0014] The wheel centers O2 and O3 of the eccentric bodies 14 and 16 are both eccentric with respect to a wheel center O1 of the input shaft 12, by the magnitude of the eccentricity Δe1. The eccentricity phase difference between the eccentric bodies 14 and 16 is set to 180° in this example.

[0015] Roller bearings 18 and 20 are each arranged on the outer circumferences of the eccentric bodies 14 and 16. Externally toothed gears (planetary gears) 22 and 24 are mounted in an oscillating manner in the outer circumferences of the roller bearings 18 and 20. The externally toothed gears 22 and 24 mesh internally with an internally toothed gear 26.

[0016] The internal gear 26 is primarily configured such that it has a main body 26A of the internal gear, which is integrated with a housing 31, an outer pin or pins 26B, which are supported by the main body 26A of the internal gear and have a cylindrical shape, and a roller 26C, which is fitted externally onto the outer pin 26B so that it is rotatable and forms the "inner teeth" of the internal gear 26. The number of inner teeth (the number of rollers 26C) of the internal gear 26 is slightly greater than the number of outer teeth of the external gears 22 and 24 (in this example, by only one).

[0017] In the externally toothed gears 22 and 24, a plurality (in this example 10) of through holes 22A and 24A are provided at positions offset from the gear centers (corresponding to O2 and O3). The plurality of through holes 22A and 24A are spaced apart from each other at intervals of 36° in the circumferential direction. Additionally, a pair of support elements (flange members) 32 and 34 are arranged axially on both side parts of the group of externally toothed gears 22 and 24. The support elements 32 and 34 are supported by the housing 31 via angular contact ball bearings 40 and 42. The angular contact ball bearings 40 and 42 do not have any additional inner rings. The outer circumferential parts of the support parts 32 and 34 act as the inner rings of the angular contact ball bearings 40 and 42. Furthermore, the supports 32 and 34 carry the input shaft 12 via bearings 35 and 37.

[0018] An inner bolt 28 is integrally formed on the support part 34 on a load-bearing side as described above. Additionally, it can be configured such that the inner bolt 28 is formed separately from the support part 34 and is connected to the support part 34, for example, via an interference fit or similar.

[0019] In this embodiment, 10 inner bolts 28 are formed as described above, such that they correspond to through holes 22A and 24A in the externally toothed gears 22 and 24. Each of the inner bolts 28 passes through the through holes 22A and 24A in the externally toothed gears 22 and 24. The support part 34 is integrated with an output shaft 48.

[0020] Furthermore, a recess 32D is formed on the non-load-bearing side of the support part 32 on a side surface adjacent to the externally toothed gears 22 and 24 of the support part 32. A tip of the inner bolt 28 fits into the recess 32D, and the inner bolt 28 connects the support part 32 and the support part 34 by means of a screw 45.

[0021] A sliding roller 44, acting as a sliding pressure element, is arranged between the inner bolt 28 and the externally toothed gears 22 and 24 (the inner circumferential surfaces of the through holes 22A and 24A therein). The sliding roller 44 normally bears against a portion of the inner circumferential surfaces of the through holes 22A and 24A in the externally toothed gears 22 and 24. Furthermore, gaps are provided on the sides of the other portion of the sliding roller 44, which do not bear against the through holes 22A and 24A, by twice the size of Δe1 (2·Δe1), which is the eccentricity of the eccentric bodies 14 and 16.

[0022] Next, a structure relating to the centering collar connection surface 17 of the speed reduction device 10 is described.

[0023] The speed reduction device 10 is used in a state in which the motor 13 is connected to its input side and the entire arrangement is mounted on a base plate 50 of the connected machine 15.

[0024] A motor housing 13B of the motor 13 is attached to an adapter 54 by a first screw 52. The adapter 54, to which the motor 13 is attached, is attached to the speed reduction device 10 by a second screw 56. That is, in this embodiment, the adapter 54 corresponds to a component of the front stage.

[0025] In this embodiment, the adapter 54 is located between the motor 13 and the speed reduction device 10. The adapter 54 acts as a connecting element to link the motor 13 and the speed reduction device 10, and it also acts as a housing for the speed reduction device 10.

[0026] Therefore, the adapter 54, as part of the housing 54 of the speed reduction device 10, serves to seal lubricants within the speed reduction device 10. The adapter 54 is externally fitted onto an outer ring 40A of the angular contact ball bearing 40 in the speed reduction device 10. However, when the adapter 54 is connected to the housing 31 of the speed reduction device 10 (with a main housing part 58 thereof), there is a possibility of interaction between the two centering collar connecting parts. To prevent such interaction, the fitting, or insertion, of the outer ring 40A of the angular contact ball bearing 40 into the adapter 54 is intentionally designed in a non-centering manner, as shown in Fig. Figure 2 shows that the connection is made with a gap δ that is larger than the gap in a centering manner, as is the case with the fitting or mating with respect to the centering collar connection surface 17. Furthermore, to ensure the sealing of the lubricant in the speed reduction device 10, an O-ring 70 is arranged in a fitting between the adapter 54, which is part of the housing 31 of the speed reduction device 10, and the outer ring 40A of the angular contact ball bearing 40. In particular, a recess 54B with a hook or shoulder shape is formed on an inner circumferential side of an end surface 54A on the adapter 54, the end surface 54A being opposite to the axial end surface 58A on the main housing body 58. The O-ring 70 is inserted into the recess 54B and bears against it on four surfaces along three links.The three components are the main housing body 58, the adapter 54, and the outer ring 40A of the angular contact ball bearing 40, which is located on the inner circumferential side of the adapter 54. Therefore, the inside and outside of the speed reduction device 10 are sealed.

[0027] Furthermore, the housing 31 of the speed reduction device 10 is configured such that the adapter 54 functions as the front housing, the main housing body 58, and the load-side cover 60, which are fastened together by the second screw 56. The main housing body 58 accommodates the speed reduction mechanism 11 of the eccentrically oscillating design, and the load-side cover 60 primarily accommodates the support 34 and the output shaft 48.

[0028] In this embodiment, an annular centering collar connection surface 17 is formed according to the invention in the manner above on an outer circumference of an end part on the side of the adapter 54 of the main housing body 58.

[0029] The centering collar connection surface 17 has an outer diameter d2, which is slightly larger than an outer diameter d1 of the main housing body 58. Finishing is carried out on the centering collar connection surface 17.

[0030] The axial length of the centering collar connection surface 17 is represented by L1. Within the surface with axial length L1, the surface with axial length L2 on the side of the adapter 54, which is approximately half the axial length L1, is a centering collar connection surface 17A of the front stage side, used to fit the adapter 54. Additionally, the remaining surface with axial length L3 on the side not belonging to the adapter 54, which is approximately half the axial length L1, is the centering collar connection surface 17B of the rear stage side, used to fit the base plate 50 of the connected machine 15. That is, in this embodiment, the base plate 50 of the connected machine 15 corresponds to the "component of the rear stage side".

[0031] In this embodiment, the adapter 54, as a component of the front stage, and the base plate 50 of the connected machine 15, as a component of the rear stage, are fastened to each other by a third screw 72. In this embodiment, the adapter 54 and the base plate 50 are elements that do not rotate relative to each other.

[0032] However, the adapter 54 and the base plate 50 are not necessarily in a fixed state. That is, assuming that the speed reduction device 10 is a single unit, it is generally understood that the housing 31 is a fixed body and that the output shaft 48 is a rotating body. Thus, the adapter 54 and the base plate 50 are considered a fixed body. However, depending on the application, the housing 31 and the output shaft 48 may be links that rotate relative to each other, for example, if the speed reduction device 10 is used for an articulated part of a multi-axis industrial robot. Therefore, it is difficult to determine "which element is fixed" and "which element rotates."This means that, depending on the actual installation position of the speed reduction device 10, it can be said that the adapter 54 and the base plate 50 themselves rotate relative to the output shaft 48 of the speed reduction device 10. In other words, it is irrelevant whether the adapter 54 and the base plate 50 are a rotating body or a stationary body according to the exemplary embodiment.

[0033] Next, the operation of the speed reduction device 10 will be described.

[0034] First, the operation of the eccentrically oscillating speed reduction mechanism 11 is described.

[0035] When the input shaft 12 rotates, the eccentric bodies 14 and 16, which are integrated with the input shaft 12, rotate eccentrically. This causes the externally toothed gears 22 and 24, which are mounted on the outer circumferences of the eccentric bodies 14 and 16 via the roller bearings 18 and 20, to oscillate with phase differences of 180°. The externally toothed gears 22 and 24 mesh internally with the internally toothed gear 26. Furthermore, in this embodiment, the main body 26A of the internally toothed gear 26 is integrated with the housing 31. Thus, with each rotation of the input shaft 12, the externally toothed gears 22 and 24 rotate relative to the internally toothed gear 26 (housing 31) by the amount of a difference in the number of teeth between them (in this example, the difference is one).

[0036] The rotational components of the externally toothed gears 22 and 24 are transmitted to the carrier parts 32 and 34 via the sliding roller 44 and the inner bolts 28, which pass through the through holes 22A and 24A in the externally toothed gears 22 and 24. This causes the carrier parts 32 and 34 to rotate relative to the housing 31 at the same speed as the rotational components of the externally toothed gears 22 and 24. As a result, power output (rotation relative to the housing 31) can be derived from the output shaft 48, which is integrated with the carrier 34.

[0037] In this embodiment, the motor 13, the adapter 54, and the main housing body 58 of the speed reduction device 10 are connected to one another as follows. The motor 13 is connected to the adapter 54 by the first screw 52. The adapter 54, which is connected to the motor 13, is fitted externally onto the centering collar connection surface 17A of the front stage side, and then the adapter 54, together with and in conjunction with the main housing body 58 of the speed reduction device 10, is connected by the second screw 56. In this case, the centering collar connection surface 17A of the front stage side is approximately half the area of ​​the single centering collar connection surface 17 formed on the outer circumference of the main housing body 58 of the speed reduction device 10, specifically on one adapter side in the axial direction.

[0038] Furthermore, the base plate 50 of the connected machine 15 is fitted externally onto the centering collar connection surface 17B of the rear stage side and is connected to and fastened to the adapter 54 via the third screw 72. In this case, the centering collar connection surface 17B of the rear stage side is approximately half the size of the corresponding centering collar connection surface 17 on the non-adapter side in the axial direction. That is, in this embodiment, the adapter 54 and the base plate 50 do not rotate relative to each other and are securely and directly connected.

[0039] The adapter 54 and the base plate 50 are fitted in a centered manner onto the same centering flange connection surface 17 (externally fitted), and thus the adapter 54 and the base plate 50 are connected to each other in a state in which a common wheel center is maintained (in accordance with O1). As a result, it is possible to realize the connection in which the wheel center (O1) of the motor 13 and the wheel center (O1) of a driven body of the connected machine 15 are precisely aligned (regardless of the arrangement of the speed reduction device 10).

[0040] The reason is as follows. Normally, deviations or tolerances between the wheel center (O1) of the motor 13 and the wheel center (O1) of the speed reduction device 10, and the deviation or tolerance between the wheel center (O1) of the speed reduction device 10 and the wheel center (O1) of the connected machine 15, are likely to accumulate or add up. However, in this embodiment, the motor 13 and the connected machine 15 are directly controlled or aligned by the same centering collar connection surface 17. Therefore, the deviation between the wheel center (O1) of the motor 13 and the wheel center (O1) of the connected machine 15 is not accumulated or added up, even though the speed reduction device 10 is positioned between them.Such a characteristic, that the deviation is not added up, is particularly useful when the configuration is applied to devices that are configured to have a large number of axes that are directly connected to each other, for example in an application with a multi-axis industrial robot with multiple degrees of freedom (for example with six axes).

[0041] Since the centering collar connection surface 17 itself, which acts as two centering collar surfaces, is shaped in such a way that it is a single surface (one component), the machining effort only needs to be carried out once. Therefore, it is possible to significantly reduce the machining costs.

[0042] Furthermore, the adapter 54 partially functions as the housing 31 of the speed reduction device 10 and is externally fitted onto the angular contact ball bearing 40. However, with respect to the outer fitting part, the opposing effect of two fitting parts does not occur because the fitting process is performed in a non-centering manner, whereby this fit is designed such that the gap δ is larger than the gap in the centering manner applied to the fit with respect to the centering collar contact surface 17. Additionally, the function of the lubricant seal in the speed reduction device 10 is not impaired because the O-ring 70 is located in the fitting part of the outer ring 40A of the angular contact ball bearing 40.

[0043] Fig. Figure 3 shows an example of another embodiment of the invention.

[0044] In this embodiment, two centering collar connecting surfaces 117A and 117B, which form centering collar connecting surfaces 17, are formed at a distance from each other on the housing 131 of the speed reduction device 110, which is the same as in the embodiment described above. The two centering collar connecting surfaces 117A and 117B have the same diameter d102, and they are formed in such a way that no part with a diameter greater than the diameter of the centering collar connecting surface 117A or 117B is present between the two centering collar connecting surfaces 117A and 117B. More precisely, the centering collar connecting surfaces 117A and 117B are formed on the outer circumference of the main housing body 158 in the manner described above, spaced apart from each other by a clearance L104, so that they have an annular shape.In the main housing body 158, a portion located further axially on the adapter side than the centering collar connection surface 117A, a portion located between the centering collar connection surface 117A and the centering collar connection surface 117B, and a portion located axially laterally on the side not facing the adapter than the centering collar connection surface 117B all have the same outer diameter d101 and no portion has an outer diameter larger than the outer diameter d102 of the centering collar connection surface 117A or 117B. Therefore, it is possible to form the centering collar connection surfaces 117A and 117B simultaneously in a single machining operation (a machining operation performed using the same tool in the same setup), regardless of which side in the axial direction the machining operation starts from.Therefore, it can be assumed that the two centering collar connection surfaces 117A and 117B have practically identical characteristics, and thus it is unlikely that a deviation between the two centering collar connection surfaces 117A and 117B will occur. Additionally, it is possible to reduce machining costs.

[0045] Furthermore, with regard to the configuration according to this embodiment, the practical form length or practically implemented length (axial length) L101 of the centering collar connection surface 117 can be ensured or designed to be long. Therefore, it is possible to further improve the concentricity of the adapter 154 of the front-stage component with the base 150 of the rear-stage component.

[0046] Furthermore, machining costs (costs for machine processing) for the machining operation can be reduced, as it is not necessary to machine the central part of the centering collar connection surface 117. Compared to the case where a centering collar connection surface 117 with the same axial length L101 is continuously formed, it is also possible to extend the tool life, shorten the machining time, and reduce machining costs.

[0047] The other configurations are the same as those in the previous embodiment. Therefore, in the drawings, a reference numeral whose last two digits are the same as those in the previous embodiment is assigned to a member or element that is the same or functionally identical to the one in the previous embodiment. Furthermore, the description of the element is not repeated.

[0048] In addition, some supplementary explanations regarding the front-stage side component and the rear-stage side component according to the invention are appended.

[0049] In addition to a motor as a drive source, a speed reduction device of a front stage or first stage, a coupling device, or a similar device is also included as a "front stage component," which is arranged on an upstream side or input side in a power transmission path of the speed reduction device according to the present invention. If, as in the previous embodiment, the motor is connected to the speed reduction device as a front stage component or input stage component via the adapter (connecting element), a component for connecting the front stage component to the speed reduction device, which is "a component for connecting a front stage component," such as the adapter, is included as the "front stage side component" according to the invention, in addition to the front stage component mentioned above by way of example.

[0050] Furthermore, in addition to a member which is completely independent with respect to the speed reduction device, a member, such as the adapter 54 in the previous embodiment, which acts as part of the components of the speed reduction device when connected to the speed reduction device, is included in the concept of the “front stage side component”.

[0051] Similarly, in addition to a connected machine as a driven object, a speed reduction device of a rear stage or second stage, a coupling device, or the like is also included as a "rear stage component," which is arranged on a downstream side or output side of the power transmission path of the speed reduction device. In addition to the rear stage components shown above as examples, a component for connecting the rear stage component to the speed reduction device is also included in the "rear stage side component" according to the invention.

[0052] Although not mentioned in the previous embodiment as being similar to the "front-stage component," the concept of the "rear-stage component" according to the invention can include a member that acts as part of the components of the speed reduction device when connected to the speed reduction device, in addition to a member that is completely independent with respect to the speed reduction device. Thus, it is applicable, or included, that the speed reduction device is organically mounted on the connected machine, and that, for example, part of the connected machine itself forms part of the housing of the speed reduction device.

[0053] Depending on the actual mounting position or installation position, it is also conceivable that the front-stage component and the rear-stage component, which are fitted onto the centering collar connection surface, are configured to rotate relative to the output shaft of the speed reduction device, as described above. In other words, it is irrelevant whether the front-stage component and the rear-stage component according to the invention are rotating bodies or stationary bodies.

[0054] Although the front-stage component and the rear-stage component are attached together in the previous embodiment, according to the invention, the front-stage component and the rear-stage component do not necessarily have to be attached together. Thus, according to the invention, the front-stage component and the rear-stage component can be connected to the housing of a speed reduction device by different screws. First, one of the components, i.e., the front-stage component or the rear-stage component, can be configured to rotate relative to the other component. For example, one component, i.e.,the component of the front stage side or the component of the rear stage side is integrally connected to the housing of the speed reduction device via the centering collar connection surface, and the other component rotates relative to the housing of the speed reduction device in the centering collar surface part by means of a sliding bearing (whereby it is connected, for example, to the output shaft 48 in the previous embodiment).

[0055] If, in the previous embodiment, the front-stage component has the other mating surface next to the centering collar connection surface, the fit of the other mating surface is additionally designed with a large gap, so that the fit is practically non-centering in order to prevent counteraction. However, the invention is not intended to prevent the other centering collar surface from being provided next to the centering collar connection surface. It can be configured so that the front-stage component (or the rear-stage component) is mounted more precisely using a plurality of centering collar connection surfaces, as long as adequate accuracy is ensured between them.

[0056] The speed reduction device according to the invention can achieve a significant effect, particularly when applied to a speed reduction device such as the speed reduction device in the previous embodiment, where an input shaft and an output shaft are coaxial. However, this is sufficient for the purposes of the invention as long as the front-stage component and the rear-stage component have mating surfaces that fit onto a single or common centering collar interface (with the same diameter). Thus, the configuration of the speed reduction mechanism of the speed reduction device is not specifically limited and can be a simple planetary gear speed reduction mechanism, a speed reduction mechanism with parallel shafts, an angle speed reduction mechanism, or, for example, a combination of these mechanisms.

Claims

[1] Speed ​​reduction device (10) comprising the following: a case (31, 58), wherein a single centering collar connection surface (17, 17A, 17B) is provided in the housing (31, 58), wherein a component (54) of a front stage side of the speed reduction device (10) and a component (50, 15) of a rear stage side of the speed reduction device (10) are fitted onto the individual centering collar connecting surface (17, 17A, 17B) in a centering manner, and wherein the component (50, 15) of the rear stage side is a component of a connected machine (15) which is to be driven by the speed reduction device (10). [2] Speed ​​reduction device (10) according to claim 1, wherein the component of the front stage side (54) and the component (50, 15) of the rear stage side, which are fitted onto the individual centering collar connecting surface (17, 17A, 17B), are attached to each other. [3] Speed ​​reduction device (10) according to claim 1 or 2, wherein the component of the front stage side (54) and / or the component (50, 15) of the rear stage side also fit externally onto an outer surface of an outer ring (40A) of a bearing (40) in the speed reduction device (10), and where the external fitting is carried out with a gap (δ) that is larger than a gap in the fitting with respect to the individual centering collar connection surface (17, 17A, 17B). [4] Speed ​​reduction device (10) according to claim 3, wherein the housing (31, 58) is also arranged on the outer surface of the bearing (40). [5] Speed ​​reduction device (110) comprising the following: a case (131, 158), wherein two centering collar connecting surfaces (17, 117A, 117B) are formed apart from each other in the housing (131, 158), wherein the two centering collar connecting surfaces (17, 117A, 117B) have the same diameter (d102), and wherein the diameter of the part between the two centering collar connecting surfaces (17, 117A, 117B) is smaller than the diameter (d102) of the two centering collar connecting surfaces (17, 117A, 117B).

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