Device for testing the gearing of a differential gear

Abstract

Device for testing the gearing of a differential gear (1) comprising axle bevel gears (5, 6), axle shafts (16, 17), compensating bevel gears (7, 8) and a differential housing (2), comprising a machine table (11) on which the differential gear (1) is received and clamped, with first bearing devices (12, 13) for receiving the differential housing (2) and second bearing devices (14, 15) for receiving the axle shafts (16, 17), wherein the axle shafts (16, 17) are connected in a rotationally fixed manner to stationary cable drums (18, 19) which are held under tension in the direction of rotation by means of a cable pull (20).

Description

[0001] The invention relates to a device for testing the toothing of a differential gear, which has axle bevel gears, axle shafts, differential bevel gears and a differential housing.

[0002] In a differential gear, particularly for motor vehicles, axle bevel gears, which are non-rotatably mounted on the inner ends of axle shafts, mesh with differential bevel gears, which are rotatably mounted on a differential pin, forming a so-called differential gearing. The operating conditions typical for differential gearing are characterized by low speeds (typically 2 to 20 revolutions per minute) and high axle shaft torques (typically 500 to 3500 Nm), for example, in a passenger car application.

[0003] When the vehicle is traveling straight ahead, i.e., when the right and left wheels of an axle are traveling at the same speed, the differential gearing of a differential is only subjected to static stress, meaning there is no change in gear mesh. When cornering, however, different wheel and thus axle shaft speeds occur on the outside and inside of the curve, which are compensated for by the meshing between the differential and axle bevel gears. This results in a change in gear meshing, and the bevel gears mesh with each other.

[0004] State of the art is disclosed in DE 36 42 717 A1, US 7 921 712 B1 and US 3 712 127 A.

[0005] One object of the invention is to propose a testing device which represents the stresses occurring in practice as representatively as possible and makes them measurable.

[0006] The invention results from the features of patent claim 1. Advantageous embodiments result from the subclaims.

[0007] According to the invention, the testing device comprises a machine table with first bearing devices for supporting the differential housing and second bearing devices for radially guiding the axle shafts. These are non-rotatably connected to fixed and coaxially arranged cable drums, which are connected to each other via a cable pull and mechanically clamped. The differential housing to be tested is firmly clamped and thus cannot rotate. The axle shafts and thus the axle bevel gears are clamped via the cable drums, on which torques act in the same direction due to the cable pull, relative to the differential bevel gears, which are held in the differential housing via a differential bolt.

[0008] According to an advantageous embodiment, the cable pulley comprises a tensioning cable and a deflection device, with one end of each tensioning cable being fixed to a cable drum and wound up with a few turns. The deflection device guides the tensioning cable from one cable drum to the other, which corresponds approximately to a U-shaped cable path.

[0009] According to a further preferred embodiment, the cable pulley has a tensioning device, preferably designed as a spindle drive, which maintains tension on the tensioning cable guided between the two cable drums. This results in equal and identical torques acting on the two cable drums, which are transmitted to the axle shafts. The axle shafts, and thus the axle bevel gears, remain in equilibrium under this torque load.

[0010] According to a further preferred embodiment, the deflection device comprises two deflection pulleys, between which the tensioning device is arranged. This results in an approximately W-shaped path for the tensioning cable from cable drum to cable drum.

[0011] According to a further preferred embodiment, the tensioning device is adjustable, i.e., different tensile stresses can be set in the tensioning cable, resulting in different torques on the cable drums. This makes it possible to conduct tests with different torque loads (torque collectives), i.e., with different degrees of tension in the compensating gearing.

[0012] According to a further preferred embodiment, at least one of the two cable drums can be driven in reversing mode, i.e., oscillating over a rotation angle of less than 360°. Thus, the cable drums do not rotate completely, which is consistent with the tensioning cable being wound onto the cable drums in the same direction. For example, if the tensioning cable is wound onto the driven cable drum, it is simultaneously unwound onto the other cable drum. This corresponds to the vehicle cornering, with the tensioning cable simulating the road surface.

[0013] According to a further preferred embodiment, at least one of the two cable drums can be driven via a crank rocker. This allows for an oscillating drive of the cable drum, with the angle of rotation of the cable drum being in the range of less than 180° and being determined by the kinematic design of the crank rocker.

[0014] According to a further preferred embodiment, the crank rocker, which represents a reliable gear, comprises four gear elements, namely a crank designed as a drive element which rotates about a fixed axis of rotation, a coupler and a rocker designed as an output element which is coupled to the cable drum, i.e. the movements of the rocker are transmitted 1:1 to the cable drum. The pivot point of the rocker corresponds to the pivot point of the cable drum. The coupler connects the outer end of the crank with the outer end of the rocker. The two fixed pivot points of the crank and rocker, which are at a defined distance apart, are referred to in gear technology as the frame. The crank rocker gear is characterized by two dead or extended positions, in which two gear elements, namely the crank and the coupler, form a line. As mentioned, the angle of rotation of the rocker can be determined by the dimensions of the gear elements.Another advantage is that the crank has full rotational capability and therefore only needs to be driven in one direction, i.e., without reversing the direction of rotation. The crank is preferably driven by an electric motor with a gear reduction. Another advantage is that, due to the kinematics of the crank rocker, the reversal point of the rocker is always the same. This is of great importance for the evaluation of the measurement.

[0015] According to a further preferred embodiment, the cable drum is driven partly via the crank rocker and additionally via a downstream traction drive, which preferably provides a speed increase. To ensure a defined, fixed speed ratio of the traction drive, chains or toothed belts, which provide a positive connection, are preferred as traction means. The downstream traction drive allows the angle of rotation achieved at the rocker of the crank rocker drive to be increased at the cable drum. In particular, angles of rotation greater than 180° are achievable for the cable drum.

[0016] According to a further preferred embodiment, the traction drive has a drive wheel and a driven wheel, with the drive wheel being coupled to the rocker arm of the crank-rocker drive and the driven wheel being coupled to the cable drum. Depending on the selected transmission ratio, the angle of rotation of the rocker arm is increased or decreased.

[0017] Embodiments of the invention are illustrated in the drawings and are described in more detail below, whereby further features and / or advantages may emerge from the description and / or the drawings. Fig. 1 a differential gear (test specimen) according to the state of the art, Fig. 2 a test bench according to the invention in a front view, Fig. 3 the test bench according to Fig. 1 in a view from above, Fig. 4 a detail E from Fig. 3, Fig. 5 the test bench in a side view with a drive designed as a crank swing and Fig. 6 an extended drive with crank swing and traction drive.

[0018] Fig. 1 shows a known differential gear 1, which is used as a test specimen on a test bench according to the invention in accordance with Fig. 2 to Fig. 6 is to be subjected to a test of its gearing. The differential gear 1, hereinafter also referred to as differential 1 for short, comprises a differential housing 2, also called differential cage 2 or cage 2 for short, with bearing supports 3, 4 arranged coaxially on both sides, via which the differential 1 is held in the vehicle or axle carrier. Inside the differential cage 2, two axle bevel gears 5, 6 are arranged on coaxially arranged axes x, y, which are connected in a rotationally fixed manner to axle shafts (not shown here), indicated by the axes x, y. Two differential bevel gears 7, 8 are arranged perpendicular to the axes x, y, i.e. on the axis z, which are arranged rotatably on a differential pin 9 and mesh with the axle bevel gears 5, 6. The toothing between the axle and differential bevel gears 5, 6, 7, 8 is also called differential toothing - it is the subject of testing on the test bench according to the invention.

[0019] Fig. Figure 2 shows a front view of a device 10 according to the invention for testing the gearing of a differential gear, hereinafter (as previously) referred to as test bench 10. The test bench 10 comprises a machine table 11, on which first bearing devices 12, 13 and second bearing devices 14, 15 are arranged. In the claimed subject matter, the differential 1, as shown in Fig. 1, is received and clamped. The differential 1 is connected to two axle shafts 16, 17, which are received and radially guided on the one hand in the differential 1, in the area of ​​the first bearing devices 12, 13, and on the other hand - with their outer ends - in the second bearing devices 14, 15. The differential housing 2 (cf. Fig. 1) is fixed relative to the bearing devices 12, 13 and thus cannot rotate. Outside the second bearing devices 14, 15, a first cable drum 18 and a second cable drum 19 are rotatably arranged and connected to the axle shafts 16, 17 via couplings (not shown in detail). Both cable drums 18, 19 are connected and tensioned to one another via a cable pulley 20. The cable pulley 20 comprises a tensioning cable 21, a deflection device 22 consisting of a first deflection pulley 22a and a second deflection pulley 22b, and a tensioning device 23.The first end of the tensioning cable 21 is fixed to the first cable drum 18 and wound up with a few turns; it is guided from the first cable drum 18 via the first deflection pulley 22a, the tensioning device 23, designed as a tensioning pulley, and via the second deflection pulley 22b to the second cable drum 19, onto which the second end of the tensioning cable 21 is also wound up and fixed with a few turns. As can be seen from the drawing, the guide of the tensioning cable 21 has a W-shaped course. As indicated by the double arrow P, the tensioning device 23 is adjustable, preferably by means of a spindle drive, as is known in particular from . Fig. 5. The tensioning device 23 loads the tensioning cable 21 with a defined tensile stress; the resulting tensile forces cause torques in the same direction on the first and second cable drums 18, 19. These torques in the same direction are introduced into the two axle shafts 16, 17 and transmitted to the axle bevel gears 5, 6 ( Fig. 1) which is transmitted via the differential gearing to the differential pinion gears 7, 8 ( Fig. 1). The degree of tension can thus be adjusted using the tensioning device 23.

[0020] Fig. Figure 3 shows the test bench 10 in a top view. The first bearing devices 12, 13 for receiving and clamping the differential 1, as well as the second bearing devices 14, 15 for guiding the axial shafts 16, 17, are arranged on the machine table 11. Between the two deflection rollers 22a, 22b, a handwheel 24 is arranged for actuating the spindle drive for the clamping device 23 ( Fig. 2). The area marked with dashed lines as detail E with the first bearing devices 12, 13 and the differential 1 is enlarged in Fig. 4 shown.

[0021] Fig. 4 shows detail E from Fig. 3 in an enlarged view. The differential 1 is accommodated on both sides (with its connecting pieces not shown) in the first bearing devices 12, 13, from which the axle shafts 16, 17 protrude. A crown gear 25 is attached to the differential cage 2, by which the cage 2 is locked relative to the machine table 11.

[0022] Fig. 5 shows the test bench 10 in a side view. The clamping device 23 and the deflection device 22 are arranged below the machine table 11 and the handwheel 24 for actuating the clamping device 23 is arranged above the machine table 11. The cable drum 18 is driven in reversing operation via a crank rocker 26, i.e. the cable drum 18 does not make full revolutions, but only pivoting movements within a range of a rotation angle α that is less than 180°. The crank rocker 26 represents a four-link, reliable gear mechanism which has the following gear members: a crank a rotating about the fixed axis of rotation A, a coupler b, a rocker c and a frame d. The crank a is connected to the coupler b via a joint B and this is connected to the cable drum 18 via a further joint C, the rotating arm between the pivot point D of the cable drum 18 and the joint C being referred to as the rocker c.The distance between the fixed pivot point D and the pivot point A of the crank a is referred to (in terms of gearing) as the frame d. The crank rocker 26, which is not shown to scale here, has two dead or extended positions, in which two gear elements, namely the crank a and the coupling b, form a line. The angle of rotation α can be determined by the dimensions of the four gear elements a, b, c, d. At a rotation angle α of, for example, 90°, the cable drum 18 moves by 45° to the left and to the right from the illustrated central position when the crank a is fully rotating. The cable drum 18 thus performs an oscillating rotary movement in the range of the rotation angle α, which also corresponds to the movement of the differential compensation gearing. The tensioning cable, not shown here, leads from the cable drum 18 in the direction of the deflection device 22, i.e.downwards in the drawing and thus exerts a counterclockwise torque on the cable drum 18. In the same way, a counterclockwise torque, i.e. in the same direction, is exerted on the second cable drum (hidden here). If the cable drum 18 is deflected to the right from the central position shown via the coupling b, the tensioning cable on the first cable drum 18 is wound up by the amount of the rotational movement. At the same time, the tensioning cable on the second cable drum is unwound by the same amount, i.e. the second cable drum 19 moves in the opposite direction to the direction of rotation of the first cable drum 18, which corresponds to the vehicle cornering. During this rotational movement, the axle and differential bevel gears roll against each other. The crank a is preferably driven by an electric motor 27 with a reduction gear 28.The electric motor drives the crank a in the same direction of rotation each time; due to the kinematics of the crank rocker 26, a change in the direction of rotation (switching from clockwise to counterclockwise) is not necessary. The reversal point of the rocker c during reversing is always the same.

[0023] Fig.6 shows, as a further embodiment of the invention, an expanded drive for the cable drum 18, which is also operated in reversing mode, but with an increased angle of rotation β, i.e., greater than 180°. This spread of the angle of rotation is achieved by an additional traction drive 28, which is connected downstream of the crank rocker 26. The traction drive 28 comprises a drive wheel 28a of larger diameter, a driven wheel 28b of smaller diameter, and a traction means 28c which wraps around the drive pulley 28a and the driven pulley 28b and is preferably designed as a positive traction means, in particular as a chain or toothed belt. This achieves a fixed speed ratio between the drive pulley 28a and the driven pulley 28b and prevents any slippage. The reversal point when reversing the cable drum 18 is therefore always exactly the same.By the transmission into high speed, the angle of rotation α, which is achieved by the rocker c on the drive pulley 28a, is increased proportionally to the transmission to the angle β on the cable drum 18, which is greater than α and greater than 180°. Reference symbol 1 differential 2 differential housings 3 nozzles 4 nozzles 5 axle bevel gear 6 axle bevel gear 7 differential bevel gear 8 differential bevel gear 9 differential bolts 10 Test bench 11 Machine table 12 first storage facility 13 first storage facility 14 second storage facility 15 second storage facility 16 axle shaft 17 axle shaft 18 first rope drum 19 second rope drum 20 cable pull 21 Tension cable 22 Deflection device 22a first pulley 22b second pulley 23 Clamping device 24 Handwheel 25 ring gear 26 crank swing arm 27 Electric motor 28 traction drive 28a Drive wheel 28b Output gear 28c traction device a crank b paddock c swingarm d frame A pivot point B joint C joint D Pivot point E Detail P double arrow x axle, first axle shaft y axis, second axle shaft z axis, differential bolt α angle of rotation β angle of rotation

Claims

[1] Device for testing the toothing of a differential gear (1) which has axle bevel gears (5, 6), axle shafts (16, 17), differential bevel gears (7, 8) and a differential housing (2), comprising a machine table (11) on which the differential gear (1) is received and clamped, with first bearing devices (12, 13) for receiving the differential housing (2) and second bearing devices (14, 15) for receiving the axle shafts (16, 17), wherein the axle shafts (16, 17) are connected in a rotationally fixed manner to fixedly arranged cable drums (18, 19) which are held under tension in the direction of rotation by a cable pull (20). [2] Device according to claim 1, characterized by in that the cable pull (20) comprises a tensioning cable (21) and a deflection device (22), wherein the tensioning cable (21) is fixed at each end on a cable drum (18, 19), can be wound up and is guided via the deflection device (22) from one cable drum (18) to the other cable drum (19). [3] Device according to claim 2, characterized by that the cable pull (20) has a tensioning device (23). [4] Device according to claim 2 or 3, characterized by that the deflection device (22) has two deflection pulleys (22a, 22b) and the tensioning cable (21) is guided in a W-shape over the two deflection pulleys (22a, 22b) and the tensioning device (23). [5] Device according to claim 4, characterized by that the clamping device (23) is adjustable. [6] Device according to one of claims 1 to 5, characterized by that at least one of the two cable drums (18, 19) can be driven in reversing operation. [7] Device according to claim 6, characterized by that one of the two cable drums (18, 19) can be driven via a crank rocker (26). [8] Device according to claim 7, characterized bythat the crank rocker (26) comprises four gear members (a, b, c, d), namely a crank (a) designed as a drive member, a coupling (b), a rocker (c) designed as an output member and a frame (d) with two fixed pivot points (A, D), wherein the crank (a) is connected to the coupling (b) via a rotary joint (B) and the latter is connected to the rocker (c) or to the cable drum (18) via a pivot joint (C). [9] Device according to claim 8, characterized by that the crank (a) can be driven by an electric motor (27). [10] Device according to claim 7, 8 or 9, characterized by that one of the two cable drums (18, 19) can be driven by the crank rocker (26) and additionally by a traction drive (28). [11] Device according to claim 10, characterized bythat the traction drive (28) has a drive wheel (28a) and a driven wheel (28b), wherein the drive wheel (28a) is drivable by the rocker (c) and the cable drum (18) is drivable by the driven wheel (28b). [12] Device according to claim 11, characterized by that the diameter of the drive gear (28a) is larger than the diameter of the driven gear (28b).

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