Method of tightening a wheel brake disc on a track wheel of a rail vehicle

Abstract

The invention relates to a method for tightening a wheel brake disc (3) on a track wheel (2) of a rail vehicle by means of screws (4) received in screw-receiving means (33) of a wheel brake disc (3), with which contact surfaces (35) facing away from a friction belt (31) of the wheel brake disc (3) are pressed against a flat contact surface (24) of the track wheel (2), with the following method steps: a) tightening the screws (4) up to their yield point, and b) turning the screws (4) back by a predetermined angle.

Description

[0001] DESCRIPTION

[0002] Method for tightening a wheel brake disc on a rail wheel of a rail vehicle

[0003] The present invention relates to a method for tightening a wheel brake disc on a rail wheel of a rail vehicle.

[0004] Such wheel brake discs are usually mounted with screws to a wheel web of a rail wheel.

[0005] It is important to ensure that the preload force of the screw connection is selected so that it is large enough to ensure that the wheel brake disc is sufficiently strong against shocks and vibrations during use.

[0006] However, this preload force must not be too large so as not to hinder the sliding of the wheel brake disc along a contact surface of the rail wheel during thermal expansion of the wheel brake disc.

[0007] In order to meet these requirements, the screws for tightening the wheel brake disc are mounted on the rail wheel using the so-called angle tightening method.

[0008] In the angle tightening method, the elongation of the screw and thus the preload are calculated using the angle of rotation.

[0009] This angle tightening method is characterized by the fact that, in contrast to the usual tightening of screws with torque limitation, in this method the screws are tightened by a predetermined angle of rotation.

[0010] This method is virtually independent of the friction conditions of the bolted connection and thus ensures the achievement of a defined preload force with minimal variation. However, the angle tightening method requires that the areas of the wheel brake disc to be tightened are flush with the rail wheel before the angle tightening begins.

[0011] Particularly in the case of wheel brake discs that have already been used, the re-screwing of a wheel brake disc can be impaired by the increase in temperature that has occurred during use due to residual stresses caused by braking temperatures.

[0012] This increase in price means that the screwed components, i.e. the contact surfaces of the wheel brake disc on an inner side facing away from the friction belt of the wheel brake disc, no longer lie flat on the contact surface of the rail wheel and are therefore further deformed when the screws are tightened.

[0013] As a result, the correlation between the angle of rotation and the preload force to be achieved, which is assumed in the angle of rotation tightening method, no longer applies.

[0014] For this reason, the angle tightening procedure must always be carried out in a first step, for example by tightening the screws with a torque limiter, to ensure that the surfaces of the wheel brake disc and the rail wheel lie flat on one another before the angle tightening procedure can begin.

[0015] The preload force that is achieved here at the end is therefore made up of the preload force when pre-tightening with torque limitation and the preload force when tightening with a rotation angle.

[0016] In order to achieve a small scatter of the final preload force, it is desirable to keep the preload force from the torque tightening as small as possible compared to the preload force from the angle tightening method.

[0017] In practice, however, in the case of non-flat components, a very high pre-tightening torque is required to reliably ensure that the surfaces of the wheel brake disc and the rail wheel lie flush against each other. However, the higher this pre-tightening torque, the greater the variation in the pre-tension force resulting from friction differences.

[0018] The object of the present invention is therefore to provide a simple and reliable tightening method for wheel brake discs on a rail wheel, which generates a preload force with the smallest possible scatter even in the case of deformed, non-planar screwing surfaces.

[0019] This object is achieved by a method for tightening a wheel brake disc on a rail wheel of a rail vehicle having the features of claim 1.

[0020] According to the method according to the invention, in which a contact surface facing away from the friction belt of the wheel brake disc is pressed against a flat contact surface of the rail wheel by means of screws received in screw receptacles of the wheel brake disc, the screws are first tightened up to their yield point and then the screws are unscrewed by a predetermined angle.

[0021] By tightening the screws up to their yield point, the preload force achieved is always so large that even disc-shaped wheel brake discs lie flat on top of each other with their contact surfaces facing the contact surface of the rail wheel.

[0022] This refers to a plate-shaped deformation of the brake disc, known as "shielding." This type of deformation of the wheel brake disc can, after extended service life, lead to thickness fluctuations or even localized high thermal stresses, which should be avoided if possible. Particularly during so-called emergency braking, significant temperature increases in the wheel brake disc occur, leading to such deformation of the brake disc.

[0023] Tightening the bolts to their yield point has the further advantage that the resulting preload depends only on the yield point of the bolt material and is therefore extremely precisely defined. Starting from this preload force by tightening the bolts to their yield point, the bolts are then loosened by a predetermined angle, reducing the preload force to a desired value that allows the wheel brake disc to slide along the contact surface of the rail wheel during thermal expansion, as mentioned above.

[0024] Since this force reduction by turning back the screws by a predetermined angle depends only on the angle of reversal and not on the friction coefficient of the screw, the desired target value of the preload force can be achieved with high accuracy.

[0025] Advantageous embodiments of the invention are the subject of the subclaims.

[0026] According to an advantageous embodiment, after the screws have been turned back by the predetermined angle, an air gap measurement is carried out between a radial edge area of ​​the contact surfaces of the friction belt and the contact surface of the rail wheel.

[0027] This also ensures that all contact surfaces do not exceed a maximum permissible air gap.

[0028] The predetermined angle is dimensioned so that a predetermined target preload of the screws is achieved.

[0029] According to an advantageous embodiment variant, the predetermined angle lies in an angular range of 25° to 55°, particularly preferably in an angular range of 30° to 50°.

[0030] The process is explained in more detail below using the attached figures. They show:

[0031] Figure 1 is a sectional view through a rail wheel with wheel brake discs mounted on both sides and

[0032] Figure 2 is a top view of the wheel brake disc.

[0033] In the following description of the figures, terms such as top, bottom, left, right, front, rear, etc., refer exclusively to the exemplary representation and position of the wheel brake disc, rail wheel, contact surface, screws, friction belt, and the like chosen in the respective figures. These terms are not to be understood as limiting; i.e., these references may change due to different operating positions or the mirror-symmetrical design, etc.

[0034] In Fig. 1, the reference number 2 denotes a rail wheel of a rail vehicle.

[0035] The rail wheel 2 has a running surface 21 on its radial outer side for support on a rail. Furthermore, the rail wheel 2 has an annular brake disc mount 22 between a central machined area and the area adjacent to the running surface 21.

[0036] Preferably, two such brake disc receptacles 22 are formed on the rail wheel 2.

[0037] The area thus remaining, with its material thickness reduced and referred to here as wheel web 23, is flat and forms contact surfaces 24 against which contact surfaces 35 of a respective wheel brake disc 3 rest.

[0038] The respective wheel brake disc 3 essentially has a friction belt 31 with a friction surface 32 against which a brake pad of a rail vehicle brake can be pressed.

[0039] Centrally in the respective friction belt 31, several screw receptacles 33 are provided, as shown in Figure 2, which serve to receive screws 4 with which the wheel brake disc 3 is fastened to the rail wheel 2 of the rail vehicle by tightening the screws 4.

[0040] Each of the screws 4 has a screw head 41 and a screw shaft 42 which extends through a bore 25 in the wheel web 23 of the rail wheel 2.

[0041] A screw nut 5 is screwed onto an end of the screw shaft 42, preferably provided with an external thread, the end face of which rests against a step 34 of the wheel brake disc 3 that narrows the screw receptacle 33. In the illustrated embodiment, the screw head 41 rests on the end face of a sleeve 6, which in turn also rests against a step 34 in the screw receptacle 33 of the wheel brake disc 3.

[0042] The inner side of the respective wheel brake disc 3 facing away from the friction surface 32 of the wheel brake disc 3 is preferably provided with a plurality of cooling fins 37, the sides of which facing the contact surface 24 of the rail wheel 2 form the contact surfaces 35 of the wheel brake disc 3.

[0043] When the wheel brake discs 3 are not tightened by the screws 4, they may tend to become more expensive after prolonged use, which leads to parts of the contact surfaces 35 of the wheel brake disc 3 not contacting the contact surface 24 of the rail wheel 2.

[0044] In order to nevertheless ensure reliable contact of the contact surfaces 35 of the wheel brake disc 3 on the contact surface 24 of the rail wheel 2, the screws 4 are first tightened to their yield point in order to tighten the wheel brake disc 3 on the rail wheel 2.

[0045] The screws 4 are then turned back by a predetermined angle in the opposite direction to the tightening direction in order to ensure that the respective brake disc rests flat against the contact surfaces of the rail wheel 2 on the one hand and to ensure that the brake disc slides along the contact surfaces 24 of the rail wheel 2 as a result of thermal expansion of the brake disc on the other hand.

[0046] Since the angle of reversal of the screws 4 against the tightening direction depends only on the angle of reversal but not on the friction coefficient of the screw 4, a desired target value of the preload force can be achieved with extremely high accuracy.

[0047] Preferably, after the screws 4 have been turned back by the predetermined angle, an air gap measurement is performed between a radial edge region 36 of the contact surfaces 35 of the wheel brake disc 3 and the contact surfaces of the rail wheel 2 in order to check the contact of the contact surfaces 35 of the wheel brake disc 3 against the contact surface 24 of the rail wheel 2. The predetermined angle is dimensioned such that a predetermined target preload force of the screws 4 is achieved. This predetermined angle lies in particular in an angular range of 25° to 55°, more preferably in an angular range of 30° to 50°.

[0048] List of reference symbols

[0049] 2 rail wheels

[0050] 21 Tread

[0051] 22 brake disc mount

[0052] 23 bike bridge

[0053] 24 contact surface

[0054] 25 bore

[0055] 3 wheel brake disc

[0056] 31 Friction belt

[0057] 32 Friction surface

[0058] 33 screw receptacle

[0059] 34th level

[0060] 35 contact surface

[0061] 36 Marginal area

[0062] 37 cooling fin

[0063] 4 screw

[0064] 41 screw head

[0065] 42 screw shaft

[0066] 5 screw nut

[0067] 6 sleeve

Claims

Claims 1. Method for tightening a wheel brake disc (3) on a rail wheel (2) of a rail vehicle by means of screws (4) received in screw receptacles (33) of a wheel brake disc (31), with which contact surfaces (35) facing away from a friction belt (31) of the wheel brake disc (3) are pressed against a flat contact surface (24) of the rail wheel (2), with the method steps: a) tightening the screws (4) up to their yield point, b) unscrewing the screws (4) by a predetermined angle.

2. Method according to claim 1, characterized in that after turning back the screws (4) by the predetermined angle, an air gap measurement is carried out between a radial edge region (36) of the contact surfaces (35) of the friction belt (3) and the contact surface of the rail wheel (2).

3. Method according to claim 1 or 2, characterized in that the predetermined angle is dimensioned such that a predetermined target preload force of the screws (4) is achieved.

4. Method according to claim 3, characterized in that the predetermined angle lies in an angular range of 25° to 55°.

5. Method according to claim 3, characterized in that the predetermined angle lies in an angular range of 30° to 50°.

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