WO2015185713A1

WO2015185713A1 - Bearing friction test with tilting moment

Info

Publication number: WO2015185713A1
Application number: PCT/EP2015/062550
Authority: WO
Inventors: Alexander Kiforiuk; Dennis Kontner
Original assignee: Thyssenkrupp Presta Ag
Priority date: 2014-06-06
Filing date: 2015-06-05
Publication date: 2015-12-10
Also published as: DE102014008127A1

Abstract

The invention relates to a device for measuring the internal friction of anti-friction bearings (1) with a loading device for loading the anti-friction bearings (1) to be tested with a test load during simultaneous rotation of the bearing rings (2, 3), relative to one another, with a driving motor which can be coupled to one of the two bearing rings (2, 3), with the result that the motor drives the rotating part of the bearing (1) about a longitudinal axis during the measurement, and with a frame which is set up to hold the other of the two bearing rings (2, 3) in a holder (21) fixedly so as not to rotate, in which device the loading device has a first means for generating a force as a first component of the test load parallel to the longitudinal axis and a second means for generating a torque about a tilting axis which lies perpendicularly with respect to the longitudinal axis as second component of the test load.

Description

Bearing friction test with tilting moment

The present invention relates to a device for measuring the internal friction of bearings with the features of the preamble of claim 1 and a method having the features of the preamble of claim 7.

Electromechanical power steering systems for motor vehicles are becoming

Support of a driver-initiated steering wheel hand torque

used. In this case, the electric motor on the steering column or the

Steering gear support the driver's steering movement. One type of electromechanical power steering system provides that a rack is provided in addition to the usual pinion teeth with a screw thread on which a ball screw is arranged. This ball screw is driven in operation by an electric servomotor and causes an auxiliary force in the axial direction of the rack, which supports the driver in a steering movements. Ball screws usually comprise a bearing by means of a ball bearing ball nut, wherein the ball bearing comprises a plurality of balls which are arranged between an outer ring and an inner ring.

There are particularly high demands on the noise behavior of

Ball screw, placed on its carrying capacity and life. In particular, the ball bearing must be manufactured with high precision.

At the same time, the production costs should be kept low.

From DE 10 2009 060 528 AI a device and a method for testing a ball screw is known, in which the backlash is determined. In this case, the ball nut is acted upon in the axial direction with a biasing force relative to the spindle. Meanwhile, the ball nut is moved over the entire useful range of the spindle. The preload force is each introduced in a positive and negative direction, so that the

Backlash over the entire range can be determined exactly.

In order to detect the radial play of the transmission, a device and a method are known from DE 10 2012 008 106 AI, in which the tilting of the ball nut relative to the spindle is measured. Again, the ball nut is moved over the entire threaded portion of the spindle, while on a recording of the ball nut an oblique position is provoked.

The bearings, however, are tested by the bearing inner ring of a drive shaft in rotation and hydraulically with a test load

is applied while the torque is measured on the bearing outer ring. The test load is oriented parallel to the axis of rotation. This test determines the dynamic course of the internal friction of the test bearing under pure axial load.

After installing the ball screw into the housing and putting it into operation, the bearing may become acoustically noticeable even though the previous test has been performed.

This noise can be caused by tilting of the bearing.

The invention has for its object to provide a device and a method for friction testing a ball bearing, in which the bearing behavior is simulated at skewed bearing.

This object is achieved by a device having the features of claim 1 and a method having the features of claim 7.

Thereafter, a device for measuring the internal friction of rolling bearings with a loading device for loading the test to be tested

Rolling bearing with a test load with simultaneous rotation of the bearing rings relative to each other, with a driving motor, with one of the two

Bearing rings can be coupled, so that the motor when measuring the rotating Part of the bearing about a longitudinal axis drives, and provided with a frame which is adapted to hold the other of the two bearing rings rotatably in a holder provided, wherein the loading means a first means for generating a force as a first component of the test load parallel to

Having a longitudinal axis and a second means for generating a torque about a tilt axis perpendicular to the longitudinal axis as a second component of the test load. Due to the second component of the test load, the

Bearing behavior is simulated with skewed bearing.

It is preferably provided that a bearing inner ring of the rolling bearing is rotatably connected to a test shaft of the motor, wherein the bearing inner ring rotates about the longitudinal axis, and that a bearing outer ring of the rolling bearing is pivotally mounted by means of the holder in a frame. Of the

Bearing outer ring can thus tilt with the bearing inner ring. From the tilting moment as a function of the relative position of the bearing rings to each other can be concluded on the friction of the bearing.

In one embodiment, it is provided that the holder is held firmly in space. By measuring the drive torque so can on the friction of the bearing as a function of the relative position of the bearing rings

be closed to each other.

It is advantageous if the holder is part of the loading device, wherein the defined test load by a weight at one end of one of the

Bracket protruding arm is acted upon. By this construction, it is possible that during rotation of the bearing rings relative to each other, the rotationally fixed ring can tip over.

Preferably tension the longitudinal axis of the bearing inner ring and a

Longitudinal axis of the bearing outer ring at an angle less than one degree.

In a preferred embodiment, the rolling bearing is part of a

Ball Screw.

Furthermore provided is a method for measuring the internal friction of Rolling bearings with a loading device for acting on the rolling bearings to be tested with a defined test load while rotating the bearing rings relative to each other, and a motor driving the rotating part of the bearing, the method comprising the steps of

Clamping the bearing outer ring in a holder;

Rotationally securing the bearing inner ring on a test shaft of the engine;

Pivoting of the holder relative to a longitudinal axis of

test shaft;

Rotate the test shaft or the bearing inner ring.

Preferably, the bearing outer ring during the rotation of the

Bearing inner ring held firmly in place. It is preferred that

Drive torque and the relative angular position of the engine measured.

It can also be provided in another embodiment, that the bearing outer ring is pivotally mounted during the rotation of the bearing inner ring by means of the holder and a pivoting of the holder is measured by means of an angle sensor in response to a relative angular position of the motor.

In the foregoing methods, preferably, prior to the rotation of the bearing inner race, a longitudinal axis of the support or the bearing outer ring is pivoted relative to the longitudinal axis of the test shaft by less than one degree.

It is advantageous if the rolling bearing is part of a ball screw. The ball screw in turn is part of an electromechanical

Power steering .

Hereinafter, an embodiment of the invention with reference to the

Drawings described in more detail. Show it : Fig. 1: a ball bearing in an unloaded state in a transverse and a longitudinal section,

Fig. 2: a schematic representation of a test method according to the

State of the art,

Fig. 3: a schematic representation of a device according to the invention

Test method, as well

Fig. 4: a longitudinal section of a section of a device according to the invention

Dynamometer.

Figure 1 shows a bearing in an unloaded state in a transverse and a longitudinal section. The ball bearing 1 has a bearing inner ring 2 and a bearing outer ring 3. The bearing outer ring 3 comprises the bearing inner ring 2 peripherally. The bearing rings 3, 2 are arranged coaxially to a longitudinal axis 4. Between the bearing rings 2, 3 balls 5 are arranged, which roll on a ball track 6, which is formed on an inner side of the bearing outer ring 7 and an outer side of the bearing inner ring 8. The balls 5 are in the unloaded state in contact with the ball track 6 in four ball contact points 9. Furthermore, an axis of the ball centers 10 is identical to an axis of the track centers 11th

FIG. 2 shows the prior art of the test in a longitudinal section of a ball bearing. The bearing inner ring 2 is from a

Drive shaft 12 is set in rotation and the bearing inner ring 2 is acted upon hydraulically with a test load 13. In this case, the torque is measured on the bearing outer ring 3. The test load 13 is oriented parallel to the axis of rotation or longitudinal axis 4. The balls 5 are in two ball contact points 9 'in contact with the ball track 6. The axis of the ball centers 10' has a constant offset to the axis of the raceway centers 11 'on. By the

The test shown can determine the dynamic course of the internal friction of the test bearing with pure axial load 13. Figure 3 shows schematically an inventive device for measuring the internal friction of ball bearings 1 in the design of a test stand. The test stand has a test shaft 12 which is rotatably connected to a bearing inner ring 2 of a ball bearing 1 to be tested. The bearing outer ring 3 of the ball bearing 1 is held firmly in space. A test load attacks on the

Bearing outer ring 3 so that the resulting torque the

Bearing outer ring 3 relative to the bearing inner ring 2 tilted. The tilt angle is shown exaggerated in this illustration for clarity. In reality, the tilt angle generated by the test load will be less than one degree.

As a result of this tilting, only two ball contact points 9 "are present in which the balls 5 are in contact with the ball track 6. An angular offset α occurs between the axis of the ball centers 10" and the axis of the track centers 11 " a friction measurement is performed, in which the bearing inner ring 2 is driven by the test shaft 12 in a real speed range of a ball screw and the

Drive torque 14 as a function of the rotation of the bearing inner ring 2 in space-fixed bearing outer ring 3 or the torque 15 of the

Bearing outer ring 3 is measured.

In the figure 4, a part of the test stand is shown in a longitudinal section. The bearing inner ring 2 is clamped by two discs 16, 17, whose

Outer diameter coincides with the outer diameter of the bearing inner ring 2. The two discs 16, 17 thereby form a seat 18 for the bearing inner ring 2. The lower disc 17 is inserted into the test shaft 12. The discs 16, 17 have, like the test shaft 12, in the middle one each

Hole 19, which is penetrated by a screw 20 along the longitudinal axis 4. By tightening the screw 20, the bearing inner ring 2 is clamped with the discs 16, 17 and the bearing inner ring 2 is rotatably connected to the test shaft 12. The test shaft 12 is driven by a motor, not shown, which is arranged fixed in space on a base plate of the test stand. The test shaft 12 is perpendicular to the Baseplate. On the base plate is still a not shown frame that carries a tiltable bracket 21 for the bearing outer ring 3. The holder 21 is cup-shaped and designed substantially rotationally symmetrical to the longitudinal axis 4. It covers the bearing 1 on the drive-far side. The holder 21 has on its inside a coaxial bearing seat 22 for the drive remote top side of the bearing outer ring 3. The bearing outer ring 3 is held in this seat 22 by a connected to the underside of the holder 21 via screws 23 coaxial closure plate 24. The bearing outer ring 3 is thus between the holder 21 and the

Lock plate 24 clamped against rotation. The closure plate 24 has a centrally arranged circular cutout whose diameter corresponds approximately to the inner diameter of the bearing outer ring 3. The holder 21 is pivotally connected centrally with the frame projecting beyond. In order to produce a pivoting of the bearing outer ring 3 relative to the bearing inner ring 2, the holder 21 is connected at a location on the outside with a projecting arm 25, at the end of which a weight is provided. This arm 25 is attached to the bracket 21 by means of screws 26. The weight generates a torque by which the bearing outer ring 3 tilts relative to the bearing inner ring 2, wherein the weight and the lever arm are chosen so that a tilt of less than one degree is achieved. It can be a tilt angle sensor for measuring the relative position of the

Bearing outer ring 3 may be provided to the bearing inner ring 2.

In this tilted state of the bearing 1, the friction measurement is performed, in which the bearing inner ring 2 is driven by the test shaft 12 in a real speed range of a ball screw and the

Drive torque is measured in dependence on the rotation of the bearing inner ring 2. The bearing outer ring is held firmly in space. In this case, the maximum values of the drive torque and / or the integral of the differences can be used to assess the manufacturing quality of the bearing.

To assess the manufacturing quality can also be provided, a pivoting of the holder in the frame during the rotation of the To allow bearing inner ring and to measure by means of a Kippwinkelaufnehmers the pivoting function of a relative angular position of the motor.

The aforementioned measuring methods allow the bearing behavior to be checked when the bearing is tilted. By the method according to the invention, it is possible the failure of the steering systems by errors in the camp of the

Ball screw clearly reduce.

Claims

claims

1. A device for measuring the internal friction of rolling bearings (1) with a loading device for acting on the test

Rolling bearing (1) with a test load with simultaneous rotation of the bearing rings (2, 3) relative to each other, with a driving motor which is coupled to one of the two bearing rings (2, 3), so that the motor in the measurement of the rotating part of Bearing (1) about a longitudinal axis drives, and with a frame which is adapted to the other of the two bearing rings (2, 3) rotatably in a holder (21) to hold, characterized in that the loading means comprises a first means for generating a force as a first component of the test load parallel to the longitudinal axis and a second means for generating a torque about an axis perpendicular to the longitudinal axis

Tilting axle as the second component of the test load.

2. Apparatus according to claim 1, characterized in that a

Bearing inner ring (2) of the rolling bearing (1) with a test shaft (12) of the motor is rotatably connected, wherein the bearing inner ring (2) about the longitudinal axis (4) rotates, and that a bearing outer ring (3) of the rolling bearing (1) by means of the holder (21) is pivotally mounted in a frame.

3. Apparatus according to claim 1 or 2, characterized in that the holder (21) is held fixed in space.

4. Device according to one of the preceding claims, characterized

in that the holder (21) is part of the loading device, the defined test load being acted upon by a weight at one end of an arm (25) projecting from the holder (21).

5. Device according to one of the preceding claims, characterized

characterized in that the longitudinal axis (4) of the bearing inner ring and a longitudinal axis of the bearing outer ring (3) span an angle less than one degree.

6. Device according to one of the preceding claims, characterized in that the rolling bearing (1) is part of a ball screw.

7. A method for measuring the internal friction of rolling bearings (1) with a loading device for acting on the test

Rolling bearing (1) having a defined test load with simultaneous rotation of the bearing rings (2, 3) relative to one another, and a motor driving the rotating part of the bearing (1), characterized in that the method comprises the following steps:

Clamping the bearing outer ring (3) in a holder (21);

Rotationally securing the bearing inner ring (2) on a test shaft (12) of the engine;

- pivoting the holder (21) relative to a longitudinal axis (4) of the test shaft (12);

Rotate the test shaft (12) or the bearing inner ring (2).

8. The method according to claim 7, characterized in that the

Bearing outer ring (3) is held firmly in space during the rotation of the bearing inner ring (2).

9. The method according to claim 7 or 8, characterized in that during the rotation of the test shaft (12) the drive torque and the relative angular position of the motor are measured.

10. The method according to claim 7, characterized in that the

Bearing outer ring (3) during the rotation of the bearing inner ring (2) by means of the holder (21) is pivotally mounted and a pivoting of the holder (21) by means of an angle sensor in response to a relative angular position of the motor is measured.

11. The method according to any one of claims 7 to 10, characterized in that a longitudinal axis of the holder (21) and the bearing outer ring (3) before the rotation of the bearing inner ring (2) relative to the longitudinal axis (4) of the test shaft (12) less than a degree is pivoted.

12. The method according to any one of claims 7 to 11, characterized

in that the roller bearing (1) is part of a ball screw drive.

13. Steering system with a bearing which has been measured with a device according to one of the preceding claims.