EP2127030A2

EP2127030A2 - Coaxial connector piece

Info

Publication number: EP2127030A2
Application number: EP08707301A
Authority: EP
Inventors: Markus Leipold; Thomas Reichel
Original assignee: Rohde and Schwarz GmbH and Co KG
Current assignee: Rohde and Schwarz GmbH and Co KG
Priority date: 2007-02-27
Filing date: 2008-01-25
Publication date: 2009-12-02
Anticipated expiration: 2028-01-25
Also published as: US7938663B2; US20090264016A1; WO2008104254A3; DE102007022744A1; ES2485382T3; WO2008104254A2; EP2127030B1

Abstract

Disclosed is a coaxial connector piece comprising a union nut (6) which is arranged in a rotatable and axially non-positive manner on the outer conductor (3) and can be screwed onto an external thread (9) of the opposite connector piece (2) in order to generate contact pressure between the front contact areas (10, 11) of the outer conductor of the connector. In said coaxial connector piece, the frictional torque of the axial non-positive connection between the union nut (3) and the outer conductor (3) is deliberately smaller than the frictional torque between the front contact areas (10, 11) of the outer conductor of the connector.

Description

Coaxial connector

The invention relates to a coaxial connector part according to the preamble of the main claim. Such a coaxial connector part is e.g. from WO 2007/002692 Al known.

Fig. 1 shows the longitudinal section through a coaxial connector, as it is known in a similar design, for example as an N-type plug. It consists of a plug part 1 and a female part 2. The plug 1 consists of an outer conductor 3, in which via a

Support disk 4 of the inner conductor 5 is arranged coaxially. The Koaxial1eitung consisting of inner conductor 5 and outer conductor 3 is continued on the rear side of the plug 1, not shown, for example, in a device or in a coaxial cable. On the outer conductor 3 a cap nut 6 is rotatably mounted, which is connected via a snap ring 7 axially frictionally connected to the outer conductor 3. The internal thread 8 of the union nut 6 must be screwed onto the external thread 9 of the socket 2 until the coaxial connection is produced, until the annular end contact surface 10 of the external conductor 3 of the plug 1 has the corresponding annular shape

End contact surface 11 of the socket 2 contacted. The tip 12 of the inner conductor 5 is thereby inserted into the radially sprung sleeve-shaped bushing 13 of the female part 2.

The currently commercially available coaxial connectors, as they are under the designations N-, 2.92 mm, SMA, 1.85 mm, 3.5 mm or 2.4 mm connector or as so-called hermaphroditic connector under the name PC7 are known, all are constructed according to this principle with a screwed onto the outer conductor union nut, in some cases, the union nut may also be provided on the female part. The quality of a coaxial connector is very much dependent on a sufficiently large axial preload. Too small values can lead to an unreliable connection, because the low contact pressure at the outer conductor is not sufficient to ensure a consistently low contact resistance over the entire circumference of the annular contact surface. Due to the disturbed current distribution in the contact region of the outer conductor reflections and attenuation increases can then occur at higher frequencies: an effect that can hardly be detected in the low frequency range, because there meets a low contact resistance at only a single contact point for the entire compound.

Too low axial preload also has the disadvantage that a connector can easily solve, in particular by torque attack on the bolted components, without the nut comes into play. On the other hand, excessively tight tightening can lead to premature plug wear and significant dimensional changes due to the introduced mechanical stresses. This is especially true for components of defined electrical length, such as e.g. Short circuits in calibration kits.

It is an object of the invention to avoid these disadvantages in a coaxial connector and to provide a reliable and durable connector part. This object is achieved by a coaxial connector part by the features of claim 1. Advantageous developments emerge from the subclaims.

The invention is based on the recognition that the

Friction conditions in the region of the axial frictional connection between the union nut and outer conductor of a coaxial high-frequency connector have a decisive influence on the quality of the connector. By reducing the coefficient of friction between them

Sharing is achieved according to the invention, that at a predetermined tightening torque, a higher contact pressure is achieved, the outer conductor also not so easy rotates and also higher security against unintentional release of the connector is.

Embodiments of the invention are described below with reference to the drawings. In the drawing show:

1 shows a section through a known connector.

2 shows a section through a first embodiment according to the invention;

3 shows a section through a second embodiment according to the invention;

4 shows a section through a third embodiment according to the invention;

5 shows a section through a fourth embodiment according to the invention and

Fig. 6 is a section through the fourth embodiment of the invention in the assembled state. In the following, the basic relationships between the torque applied to the cap nut and the axial preload force caused thereby are illustrated. Particular attention is paid to the influence of friction and adhesion on the various mechanical contact surfaces. It turns out that the snap ring used for transmitting power from the nut to the outer conductor of the plug has a considerable influence on the achievable axial preload and the reliability of the connection.

The achievable preload force and distribution of the tightening torque results as follows:

The torque M to be applied to the cap nut is proportional to the desired axial preload force F:

M = KF (1)

The coefficient K depends on the dimensions of the screw connection and the different coefficients of friction. There are two cases to be distinguished: a) The outer conductors of plug and socket do not twist against each other during screwing

(aspired case). Then, in addition to the effect of the thread (pitch p) and the friction in the thread (coefficient of friction / M ₃ ), the friction between the union nut and snap ring or snap ring and outer conductor must be taken into account (coefficient of friction ju _s , the smaller value applies). With ß as the flank angle of the thread (usually 60 °), d _m as the flank diameter and d _s as the mean diameter of the snap ring then applies: b) When tightening the connector, the outer conductor of the connector is completely taken away from the rotating union nut. In this case, rub the faces of the outer conductor of the plug and socket together. Analogously to (2), with d _o as mean

Diameter of the face and / Z ₀ as associated friction coefficient:

Table 1 shows, for cases a) and b), what preload force F is achieved with a 12 inch-lbs torque for an N-type connector and how the tightening torque applied to the nut splits. It is assumed that an N-type connector made of stainless steel with a snap ring made of bronze. The coefficients of friction are taken as follows: steel on steel (face and thread) 0.15; Bronze on steel 0.20 (dry) or 0.05 (lubricated).

Table 1: Preload force and torque split for an N-type connector The comparison of cases a) - dry and b) illustrates the phenomenon known to any practitioner that a N-bond can be tightened more tightly, if rotation of the outer conductors relative to each other is allowed. The same effect can apparently be achieved without rotation with a greased snap ring, which, among other things, protects the contact surfaces of the inner and outer conductors.

Even if one does not demand the high preload forces that result with greased snap ring, it would be desirable for the two outer conductors to pass through the

Do not turn the union nut on each other. This is the case when the torque exerted on the outer conductor via the snap ring is insufficient to turn the end faces against one another. With μ ' _o as static coefficient of friction at the end face is the condition

ds

Since the diameter of the snap ring for technical reasons, must be much larger than the average face diameter - in the conventional connector systems N, SMA or 2.4, it is about twice as large - the friction coefficient between snap ring and nut or snap ring and outer conductor in any case significantly smaller than be on the front surface. With a

Static friction coefficients μ ' _o of 0.18 would have to after this

Considering a maximum coefficient of friction μ ₃ of 0.076 be required for an N-type connector, which could be achieved in the lubricated case.

The best safeguard against loosening a screw connection is generally a sufficiently high preload force. This is based on the consideration that this caused axial deformation of the screw is so large that the bias is maintained even under the influence of thermal expansion and externally applied torques. In the conventional coaxial connectors but exactly this deformation is undesirable, because thereby the length of the coaxial line section, which is located in the region of the compression zone, would change. For this reason, the tightening torque remains below the yield strength of the material for this reason. Thus, the surface pressure occurring at a lubricated connector (Table 1) at the end face of the outer conductor with approximately 60 N / mm ^{2 is} far below the compressive strength of stainless steel. On the other hand, the outer conductor of the plug is already compressed under these conditions by 3 microns, which corresponds to a phase change of 0.12 ° at 18 GHz in two passes through the compound, eg for an offset short.

The safety of a screwed coaxial

Plug connection against release must therefore be formulated differently. Thus, it should be demanded that the release torque for the cap nut does not differ significantly from the tightening torque and the connection must not be released when the outer conductors are twisted against each other.

Even when loosening the union nut, as in the case of making the connection, the cases with and without mutual rotation of the outer conductor to distinguish.

If the outer conductors do not rotate against each other, the release torque applies

If the outer conductor is taken, applies

If one considers the screwing conditions, which are manifested by different preload forces F, four cases are to be distinguished, which are shown in Table 2. The tightening torque was assumed to be uniform at 12 inch-lbs, the static friction coefficients were chosen 20% higher than the coefficients of friction underlying the values in Table 1.

Table 2: Loosening moments on the union nut of a N

Plug connection (clamp value for lubricated snap ring)

Noticeable is the large variation of the release moments for a connection with unlubricated snap ring, especially the low value of 8 inch-lbs. In contrast, in the lubricated case, which causes no rotation, the tightening torque is reached. In contrast to a conventional screw joint coaxial plug connections often solve the fact that - unintentionally or due to the measurement setup - a torque is applied to the outer conductor. Thus, the connection can not solve even with very large torques, the transferable via the snap ring on the nut torque must be smaller than the counteracting moment of the thread. Since the thread pitch counteracts the friction when loosening, the following condition must be met:

After μ _'s disbanded results

For an N-plug connection with μ ₃ _'g = 0.18, a maximum permissible static friction coefficient μ would result according to this consideration' in the region of the snap ring of 0.16. This is usually not the case with a dry snap ring, always achievable with lubrication.

These considerations show that in the simplest case it is already sufficient to lubricate the snap ring 7 shown in FIG. 1 or the surface of the snap ring 7 and / or the surface of the groove of the cap nut 6 or the outer conductor 3 cooperating with this snap ring 7 to provide a corresponding lubricious coating. Instead of a lubricant, for example, the snap ring or the surfaces interacting therewith could be provided with a Teflon coating or a nano-slip film. In principle is suitable for this purpose any lubricious coating, for example so-called solid lubricants.

In commercial N-type connectors, the outer conductor and the union nut is usually made of stainless steel and the snap ring, for example, made of bronze. To reduce the coefficient of friction, these parts could also be made of other materials having a lower coefficient of friction, e.g. a suitable metal or plastic.

Figures 2 to 6 show further possibilities for the reduction of the friction coefficient between the union nut 6 and outer conductor 3 by installing corresponding bearings. For this purpose, in turn, types of many bearings are suitable, for example, axial and radial ball bearings, axial roller bearings, axial needle roller bearings, angular contact ball bearings or simple axial plain bearings.

Fig. 2 shows the installation of a radial ball bearing 20 between the union nut 6 and outer conductor 3. Each radial ball bearing acts not only as a radial bearing but also to a certain extent as a thrust bearing and is therefore also suitable for the purpose of the invention. The mounted in a cage ring balls 20 run in corresponding annular grooves on the inner circumference of the nut 6 and the outer circumference of the outer conductor 3. When axial screwing plug 1 and socket 2, the frictional force of the axial frictional connection between the union nut 6 and outer conductor 3 is strong on this ball bearing 20 lowered and thus achieved the purpose of the invention.

Fig. 3 shows another possibility using a needle or cylindrical roller bearing. Cylindrical rollers or needles 21 again arranged in a cage in a cage run on the annular end faces of a flange 22 of the outer conductor 3 and the opposite annular end face of one inside drawn radial flange 23 of the union nut 6. During axial screwing of the plug 1 and socket 2, these rollers 21 act friction friction reducing again.

Finally, FIG. 4 shows how the frictional force between cap nut 6 and outer conductor 3 can be reduced in both axial directions by a double roller bearing.

On the outer conductor 3, a radially projecting flange 24 is provided on the opposite annular surfaces each ball bearings 26, 27 roll, which in turn are mounted in corresponding grooves 28, 29 on the inside of the nut 6. Thus, both when screwing the nut 6 on the sleeve 2 via the rolling bearing 27, the coefficient of friction of the axial frictional connection between the union nut and outer conductor greatly reduced, but at the same time in the opposite axial direction over the second roller bearing 26, so that the nut 6 in non-bolted Position is ball-bearing rotatable.

In the embodiments according to Figures 2 to 4, the rolling bearings and their arrangement between the union nut and outer conductor are each shown only schematically, in practice, it is necessary for the installation of rolling bearings of course, the receiving parts such as outer conductor, union nut and the like divisible and, for example, each other screwable train. For clarity, these pure design features required for assembly are not shown.

Finally, FIGS. 5 and 6 show an arrangement with one-sided roller bearings. The rolling bearing is then loaded in this arrangement when an axial force has built up between the two end faces of plug and socket, ie in the course of the screwing or at the beginning of the release phase. When the connection is disconnected, the Bearing the union nut on various cylindrical surfaces; the rolling bearing is not involved.

This restriction of the rolling bearing effect on the Verschraubungsphase a very inexpensive, small axial needle roller bearings can be used. So that the needle bearing does not rattle or fall apart when the connection is released, it is preferably held together by spring elements. Due to the one-sided bearing effect no restrictions arise with respect to the statements made above.

On the outer conductor 3 of the plug disc springs 29 are pushed, which act between a cage-like spring retainer 31, which in turn is positively mounted in the union nut 6, and a radial annular wall 30 of two wave disks 32, 33 and only schematically indicated roller bearing 34. The disc springs can be performed either on the outer conductor 3 or in the spring holder 31.

When screwed not yet with the socket part union nut 6 (Fig. 5), the wave washer 33 is due to the spring bias on an annular projection 35 of the union nut, and the rolling bearing does not press on the flange ring 36 of the outer conductor. The bearing parts 32, 33, 34 are held by the prestressed disc springs 29 only in the union nut 6 (fixed). Only when the union nut 6 is screwed onto the external thread 9 of the schematically indicated female part 2 (FIG. 6) and the wave washer 33 presses on the flange 36 of the outer conductor 3, the frictional connection between the wave washer 33 and the annular projection 35 is released, and the axial contact force is on the union nut 6 and the

Disc springs 29 on the needle bearing 32, 33, 34 and thus transferred to the outer conductor 3. By the plate springs, the necessary axial displacement for the mounting of the bearing parts 32, 33, 34 and the spring retainer 31 with the nut 6 is guaranteed (bayonet locking the spring retainer 31 with nut 6). The bearing parts 32, 33, 34 are held together by these disc springs within the union nut, wherein thermal changes in length of the connector can be compensated without tensions occur. In addition, the use of springs allows a more cost-effective production and assembly of the relevant items, since disturbing summations of manufacturing tolerances can be easily compensated by spring elements. From the optimization of these spring functions, it also depends on how many disc springs are used, in the simplest case, a single plate spring, in the embodiment, five disc springs are shown.

The invention is not limited to the illustrated embodiments and is not only suitable for so-called N-plug but for all types of commercial coaxial connectors. All described and / or drawn features can be combined with each other in the context of the invention.

Claims

claims

1. Coaxial connector part with a rotatably and axially non-positively on an outer conductor (3) arranged union nut (6) for generating the contact pressure between outer conductor Stirnkontaktflächen (10, 11) of the connector with an external thread (9) of a counter-plug connection part (2 ), wherein the friction torque of the axial frictional connection between the union nut (6) and outer conductor (3) is smaller than the friction torque between the outer conductor end contact surfaces (10, 11) of the connector is selected.

2. Plug connection part according to claim 1, characterized in that the friction torque of the axial frictional connection between the union nut (6) and outer conductor (3) at least 20% to 50% smaller than the friction torque between the outer conductor end contact surfaces (10, 11) is selected.

3. Plug connection part according to claim 1 or 2, characterized in that the axial KraftSchluss between union nut (6) and outer conductor (3) via a snap ring (7) and that the friction coefficient between the union nut (6) and outer conductor (3) taking into account Diameter ratio of snap ring (7) and outer conductor end contact surfaces (10, 11) is selected smaller than the static friction coefficient of these end contact surfaces.

4. Plug connection part according to one of the preceding claims, characterized in that between the union nut (6) and outer conductor (3) a snap ring (7) is arranged and that the surface of the snap ring (7) and / or cooperating with this snap ring surfaces of the Union nut (6) and the outer conductor (3) have a lubricious coating.

5. Plug connection part according to claim 4, characterized in that the lubricious coating is a lubricant or a film of Teflon or nanotechnology material.

6. Plug connection part according to one of the preceding claims, characterized in that the low coefficient of friction by different materials of the union nut (6), snap ring (7) and / or outer conductor (3) is achieved.

7. Plug connection part according to claim 1 or 2, characterized in that the axial frictional connection between the union nut (6) and outer conductor (3) via a roller bearing, in particular a ball or roller bearings (20, 21, 26, 27, 34).

8. Plug connection part according to claim 7, characterized in that the axial frictional connection via an acting in both axial directions double roller bearing (26, 27).

9. Plug connection part according to claim 7 or 8, characterized in that the axial adhesion is effected by a unidirectional roller bearing, which then acts when the outer conductor end contact surfaces (10, 11) press each other.

10. Plug connection part according to claim 9, characterized in that the one-sided roller bearing is held together in the unloaded state of the connector by spring elements in the union nut (6).

11. Plug connection part according to claim 10, characterized in that the tension springs (29) cooperate with the roller bearing (34) such that only when screwing the union nut (6) with the external thread (9) of the male connector part, the rolling bearing (34) assumes a position in which on the Rolling (34) of the axial adhesion between the union nut (6) and outer conductor (3) is produced.