AT517975A1 - Method for adjusting the axial clearance in a fluid dynamic bearing system - Google Patents

Abstract

The invention relates to a method for adjusting the axial bearing play (AP) between a first bearing component (32) and a second bearing component (34) in a fluid dynamic bearing system, comprising the steps of: a) providing a preassembled assembly with the shaft (30) b) attaching the second bearing component (34) on the shaft (30) by pressing at an axial distance from the first bearing member (32), wherein the maximum of the axial bearing clearance distribution function (AP) is in the range between a setpoint (SW) and the upper limit (USL), c) measuring the axial bearing clearance (AP}, d) checking whether AP> USL, and if condition is met, then applying a defined impulse ( L1P} on the second bearing member (34), wherein the second bearing member (34) on the shaft displaces by a distance equal to or less than the difference between the upper limit value (USL) and the lower limit value (LSL) e) if condition in step d) is not met, check if AP> LSL, and if condition is met, then thrust clearance is considered good and the procedure is ended, f) if condition in steps) is not met, sorting out the bearing and leaving the procedure.

Description

Method for adjusting the axial clearance in a fluid dynamic bearing system

Field of the invention

The invention relates to a method for adjusting the axial clearance in a fluid dynamic bearing system. An apparatus for carrying out the method is also claimed.

State of the art

Fluid dynamic bearing systems are known in various designs, for example, in a first general design with one or more fluid dynamic radial bearing / -n and one or more fluid dynamic thrust bearing / -n or other general design, in which preferably two mutually-working conical fluid dynamic bearings are used.

When mounting fluid dynamic bearing systems, it is necessary to set or limit the axial bearing clearance AP (axial play), so that proper functioning of the bearing system is ensured. For many bearings, the axial bearing clearance must be set within a tolerance defined by a lower limit LSL and an upper limit (USL). In general, the axial bearing clearance is measured on an axially movable bearing component, which abuts against corresponding axial or conical surfaces of the bearing. These abutment surfaces can be realized by two in a defined axial distance from each other, for example, mounted on a shaft bearing components.

DE 103 16 940 A1, which is based on the applicant, describes an electric motor with a fluid-dynamic bearing system and a measuring method for

Determining the axial clearance or the lift height of the fluid dynamic bearing. Here, a shaft 20 is provided with a arranged at the upper end thrust washer 28, wherein the axial bearing clearance is defined by the respective axial upper and lower stop position of the thrust washer within the thrust washer 28 receiving recess 32. The bearing clearance is determined by the dimensioning of the pressure plate 28 and the recess 32. The possibility of adjusting the axial bearing clearance during assembly is not provided here.

In a fluid dynamic conical bearing system, as disclosed in DE 10 2011 016 888 A1, it is absolutely necessary to adjust the axial bearing clearance. The axial bearing clearance is determined by the axial distance of two arranged on a shaft bearing cones, which are each arranged in a corresponding recess of a bearing bush. When mounting such a bearing, the first bearing cone is mounted on the shaft, this shaft is inserted with the bearing cone in the bearing bore of the bearing bush and hereafter pressed the second bearing cone on the shaft. For this purpose, a high-precision press is used, which presses the second bearing cone as accurately as possible at a defined distance from the first bearing cone on the shaft. After pressing on the second bearing cone, the axial bearing clearance is measured. If the axial bearing clearance exceeds the upper limit value, the second bearing cone is re-pressed again and the distance between the bearing cones is reduced. This process is carried out until the axial bearing clearance AP is within the predetermined tolerance range between the upper limit value USL and the lower limit value LSL.

The axial bearing clearance AP must therefore be set within the specified tolerance between an upper limit value USL and a lower limit value LSL. After the first pressing operation is in a large part of the storage systems, the axial bearing clearance already within the specified tolerance range, whereas the remaining bearings must be re-pressed again. This is very time consuming and slows down the

Manufacturing process. Often, when repressing the lower limit of the thrust bearing play below, so these bearings must be reworked or sorted out.

Disclosure of the invention

It is the object of the invention to provide a method for adjusting the axial bearing clearance of a fluid dynamic bearing system, which operates reliably and quickly, in particular, the Committee is reduced. Here, the axial bearing clearance AP is preferably set between a predetermined lower limit value LSL and a predetermined upper limit value USL.

This object is achieved by a method having the feature of claim 1.

An apparatus for carrying out the method is specified in claim 6.

Preferred embodiments and further features of the invention are described in the respective dependent claims.

In the inventive method for adjusting the axial bearing clearance in a fluid dynamic bearing system, the axial bearing clearance is determined by a first bearing member and a second bearing member which are arranged at a mutual axial distance on a shaft, the axial bearing clearance between a predetermined lower limit and a preset upper limit is set.

In a first step, provision is made of a preassembled bearing assembly which comprises the shaft, the first bearing component fixedly arranged thereon, and a third bearing component loosely arranged on the shaft and axially displaceable. In addition, the second, aufzupressende bearing member may be additionally arranged and preferably pressed with small forces on the shaft to prevent the release of the assembly during transport or during processing.

In a second step, the first pressing-on process of the second bearing component takes place on the shaft with a predetermined axial distance from the first bearing component, so that the axial play AP is preferably in a range between 150 μm and 250 μm.

In a third step, the axial bearing clearance AP is measured.

In a fourth step, the force and displacement of the press ram are adjusted such that the second bearing component is positioned at a certain axial distance from the first bearing component on the shaft. This axial distance is selected so that the maximum of the distribution function of the axial bearing clearance AP measured below is in the range between a set value SW and the upper limit value USL.

In a fifth step, it is checked whether the measured axial bearing clearance AP is greater than the upper limit value USL. If this condition is met, exerting a defined impulse of force on the second bearing member, wherein pulse and direction of the impulse of force are chosen such that the second bearing member is displaced on the shaft by a defined amount in the direction of the first bearing member. Thereafter, the process continues at the third step.

If the condition of the fifth step was not met, it is checked in a sixth step whether the measured axial bearing clearance AP is greater than the lower limit value USL. If this condition is met, then the measured bearing clearance is within the specified tolerance. The procedure is successfully completed in this case.

If the condition of the sixth step is not met, in a seventh step, the stock is led to post-processing or sorted out. The process is finished.

A significant advantage of the invention is that the system for measuring the axial bearing clearance is integrated in an automatic pressing device, so that only a single device for carrying out the method is necessary.

Thus, the bearing components do not have to be recaptured or replaced. As a result, position inaccuracies that would be caused by the removal and insertion of the bearing in the pressing device or the measuring device, eliminated from the outset.

Another advantage of the invention is that the repressing, ie the adjustment of the axial bearing clearance, if this was measured as too large, is now carried out in the form of a pulse press. In this pulse compression method, the bearing clearance is readjusted in very small steps of typically 1 pm or less. In this pulse compression method, a defined force impact is exerted on the second bearing component, wherein the pulse and the direction of the force pulse are chosen such that the second bearing member is displaced by a defined amount in the direction of the first bearing member.

In pulse pressing, the ram is accelerated to a certain speed. The mass and speed of the ram determine the impulse force acting on the second bearing component. The pulse force is adjusted so that the second bearing member is repeatedly shifted by the defined amount in the direction of the first bearing member on the shaft.

The presettable travel amount is preferably equal to or less than the difference between the upper limit value USL and the lower limit value LSL. In a particularly preferred embodiment of the invention, the defined amount of travel is less than half or less than a quarter of the difference between the upper limit USL and the lower limit LSL.

According to the invention, all method steps are carried out in the same device without the need for re-clamping or replacement of components.

The apparatus for carrying out the method comprises a pressing device for receiving the bearing assembly, in which the axial bearing clearance is to be adjusted, a press ram for pressing the second bearing component onto the shaft at a defined distance from the first bearing component, a measuring device for measuring the axial bearing clearance AP, and an evaluation device for evaluating the measured bearing clearance AP and for comparing the measured axial clearance AP with a predetermined lower limit value LSL and a predetermined upper limit value USL. In particular, the pressing die of the pressing device is designed to exert a defined force pulse ΔΡ on the second bearing component, pulse and direction of the force pulse ΔΡ being selected such that the second bearing component is displaced only by the defined amount in the direction of the first bearing component at each impulse.

The invention will be explained in more detail below by means of an example with reference to the drawings. From the drawings and the description below, further features and advantages of the invention will become apparent.

Brief description of the drawings:

Fig. 1 shows schematically the device for adjusting the axial bearing clearance of a conical fluid dynamic bearing.

Fig. 2 shows schematically a diagram of the statistical distribution of the bearing clearance according to a previously used method.

Fig. 3 shows schematically a diagram of the statistical distribution of the bearing clearance in the inventive method.

Fig. 4 shows a possible flow diagram of the inventive method for adjusting the axial bearing clearance.

Description of a preferred embodiment of the invention

In Fig. 1, a device for adjusting the axial bearing clearance in a conical fluid dynamic bearing is shown schematically.

The apparatus comprises a pressing device 10 which comprises a press frame with a press table 12 and an anvil 14. The bearing system to be machined is received between the anvil 14 and a press top 16. In the press upper part, a press ram 18 is movably mounted and driven in the axial direction.

The storage system comprises a shaft 30 which is inserted in a receptacle of the press table 12. The lower end of the shaft 30 rests on the anvil 14. On the shaft 30, a first bearing member 32 (first bearing cone) is arranged. A second bearing component 34 (second bearing cone) is pressed by means of the press ram 18 by applying a force in the direction of arrow 24 at a distance on the shaft 30.

Between the bearing components 30, 32 and 34 a movable relative to these bearing components third bearing member 36 (rotor member) is arranged. The third bearing component 36 is separated from the stationary bearing components 30, 32 and 34 by a bearing gap 38.

The axial bearing clearance AP is defined by the maximum axial movement that the third bearing component 36 can perform between the first bearing component 32 and the second bearing component 34. For measuring the axial bearing play AP, the device comprises at least one measuring sensor 22, which is integrated in the press table 12. The measuring sensor 22 is, for example, a measuring probe which detects the absolute movement of the third bearing component 36 in the axial direction. The measuring sensor 22 can also be designed as a non-contact distance sensor. To improve the measurement accuracy are preferably several

Measuring sensors used, which are arranged distributed along the circumference of the lower end face of the third bearing member 36.

For measuring the axial bearing clearance AP, the current axial position of the third bearing component 36 is detected by the measuring sensor 22 in a first stop position. The third bearing component 36 is in the first stop position when it strikes the first bearing component 32 due to the acting force of gravity. Thereafter, the third bearing member 36 is moved by means of preferably a plurality of integrated in the press table 12 lifting cylinders 20 to a second stop position, in which it abuts the second bearing member 34. In this second stop position, the axial position of the third bearing component 36 is determined by the measuring sensor 22 relative to the previously measured first axial position. The lifting cylinders 20 preferably press on the lower end face of the third bearing component 36.

The difference between the axial position of the third bearing member 36 in the first stop position and the axial bearing in the second stop position results in the axial bearing clearance AP.

FIG. 2 schematically shows the statistical distribution of the bearing clearance AP after pressing on the second bearing component 18 according to a previously used method.

So far, the second bearing member 34 has been pressed by the ram 18 with a preset force 24 and a preset path on the shaft 30. In this case, force and travel were adjusted such that a certain distance between the first bearing member 32 and the second bearing member 34 was achieved, which corresponded to a target value SW of the bearing clearance AP. This is illustrated by the curve 40 in FIG. 2.

The statistical distribution of the actual bearing clearance varies around the setpoint SW and moves predominantly within the tolerance, which is lower

Limit LSL and an upper limit USL is determined. It can be seen that in the previous method after the pressing process, a large part of the bearings have an axial bearing clearance AP in the range of the target value SW and within the tolerance between LSL and USL, but there are outliers that lie beyond LSL or USL. These outliers with a bearing clearance AP beyond LSL and USL must be reworked, in particular, the bearing whose axial bearing clearance is greater than USL, can be brought by repressing in the range of permissible bearing clearance AP are no longer outliers with a bearing clearance AP above the upper limit USL in production.

According to the invention, the force 24 and the path that are applied to the second bearing component 34 by the pressing ram 18 during the first pressing operation are selected such that the maximum of the distribution of the axial bearing clearance AP between the setpoint value SW and the upper limit value USL located. The thus desired setpoint of the bearing clearance AP is therefore selected as the optimized setpoint SL. This is shown in the curve 42 of FIG. 3. This ensures that there are much less outliers whose bearing clearance AP is below the lower limit LSL, and then need to be reworked or sorted out. However, this results in a larger number of bearings whose bearing clearance is above the upper limit value USL. These bearings must then be reworked by another pressing operation. According to the invention, a pulse-Nachpressverfahren is used for this purpose.

Fig. 4 shows schematically the possible sequence of the pressing operation according to the invention or the setting of the axial bearing clearance AP. Here, reference is also made to FIG. 1 reference.

The shaft 30 is inserted into the pressing device 10.

In a first step 50, the first bearing component 16 (lower cone) is fastened to the shaft 14, for example by being pressed on. Alternatively, the first bearing component may already be attached to the shaft or, for example, integrally formed with the shaft 12 and thus be an integral part of the shaft. Step 50 can therefore be omitted entirely.

In the second step 52, the third bearing component 36 (hub) is pushed onto the shaft and the second bearing component 34 (upper cone) is placed on the shaft 30. This third bearing component may additionally be pressed onto the shaft 30 with small forces, for example between 100 N and 200 N, in order to prevent the assembly from being loosened during transport or during processing.

In a third step 54, the second bearing member 34 is pressed onto the shaft 30, wherein force 24 and way of the press ram 18 are selected such that a predefined distance between the first bearing member 32 and the second bearing member 34 is achieved, so that the axial play AP preferably is in a range between 150 pm and 250 pm.

The second pressing process 56, in which the second bearing component is moved such that the axial play AP reaches the region of the desired target value SW, leads to a distribution of the axial bearing clearance AP according to FIG. 3.

In the fourth step 55, the axial bearing clearance AP is determined by the measuring sensor 22 by measuring the axial position of the third bearing component 36 in the first stop position and the second stop position, as already described above.

In the sixth step 57, the axial bearing clearance AP is again determined by the measuring sensor 22 by measuring the axial position of the third bearing component 36 in the first stop position and the second stop position.

In a further step 58, it is checked whether the axial bearing clearance is greater than the upper limit value USL. The nominal axial bearing clearance AP should be 14 pm +/- 2 pm, for example. The upper limit USL would therefore be 16 pm in this example. If the axial bearing clearance AP is not greater than the upper limit value USL, then the process continues with step 60, in which it is checked whether the axial bearing clearance is greater than the lower limit value LSL, which in the example is 12 pm. If the axial bearing clearance AP is greater than the lower limit value LSL, then the bearing clearance AP is in order and lies within the tolerance. The good part may be removed from the device at step 62, and the process is completed.

If it is determined in step 60 that the axial bearing play AP is smaller than the lower limit value LSL, then the method is terminated with step 64 and the bearing can be sorted out or optionally fed to a post-processing.

If it is determined in step 58 that the axial bearing clearance AP is greater than the upper limit value USL, then in a step 66, the axial position of the second bearing member 34 is corrected by impulse repressing by the second bearing member 34 on the shaft 30 in the direction of the first bearing member 32 is moved.

During this pulse pressing in step 66, a defined force pulse ΔΡ = m * λV is exerted on the second bearing component 34 by the pressing ram 18. Here, the ram 18 is accelerated to the speed AV. He then encounters the second bearing member 34, which is displaced by the received force pulse ΔΡ by a small distance in the direction of the first bearing member 16 on the shaft 14. The force pulse ΔΡ is such that the small path change is equal to or less than the difference between USL and LSL. Preferably, the path is only a fraction of the difference between USL and LSL. In the present example, the distance is a maximum of 1 pm or any other value less than 1 pm.

After the pulse repressing according to step 66, the method continues with step 57, in which the axial bearing clearance AP is repeatedly measured. In the following step 58, it is determined whether the axial bearing clearance AP is still greater than the upper limit value USL. If so, another pulse pressing operation is performed in step 66 and then closed

Step 57 branches. If the above is not the case, continue with steps 60 to 62 or 64.

Steps 57, 58 and 66 are repeated until the axial bearing clearance AP is within the tolerance, i. between the lower limit LSL and the upper limit USL.

The method is suitable for adjusting the axial bearing clearance of all types of fluid dynamic bearings in which the axial bearing clearance is determined by the positions of two bearing components, which are arranged at a mutual axial distance on a supporting member, such as a shaft.

List of reference numerals 10 Pressing device 12 Pressing table 14 Anvil 16 Pressing upper part 18 Pressing punch 20 Lifting cylinder 22 Measuring sensor 24 Direction 30 Shaft 32 first bearing component 34 second bearing component 36 third bearing component 38 bearing gap 40 curve 42 curve 50-66 Method steps

Claims (8)

claims A method for adjusting the axial bearing clearance AP between a predetermined lower limit LSL and a predetermined upper limit USL in a fluid dynamic bearing system, wherein a first bearing member (32) is fixed to a shaft (30), a third bearing member (36) on the Shaft (30) is pushed and is rotatable relative to the shaft (30) and wherein a second bearing member (34) at a predetermined axial distance from the first bearing member (32) on the shaft (30) is fixed, so that the third bearing component ( 36) between the first bearing member (32) and the second bearing member (34) is arranged, wherein the axial bearing clearance AP by the first bearing member (32) and the second bearing member (34) is determined, comprising the steps of: (a) providing a preassembled subassembly, which comprises the shaft (30), the first bearing component (32) fixedly arranged on the shaft and the third bearing component (36) arranged on the shaft, (b) pressing on the z wide bearing member (34) on the shaft (30) at a predetermined axial distance from the first bearing member (32), (c) measuring the axial bearing clearance AP, (d) checking if AP> USL, and if condition is met, then applying a defined force pulse ΔΡ on the second bearing member (34), wherein pulse and direction of the force pulse .DELTA.Ρ are selected such that the second bearing member (34) is displaced on the shaft by a defined amount in the direction of the first bearing member (32), then continue the method in step (c), (e) if the condition in step (d) is not met, check if AP> LSL, and if condition is satisfied, then thrust bearing AP is good and terminate the method, (f) if the condition in step (e) is not met, sorting out the warehouse and terminating the process. 2. The method according to claim 1, characterized in that the axial clearance AP in step (b) is preferably in a range between 150 pm and 250 pm. 3. The method according to any one of claims 1 or 2, characterized in that the amount of travel of step (d) is equal to or less than the difference between the upper limit USL and the lower limit LSL. 4. The method according to claim 3, characterized in that the travel amount of step (d) is less than half the difference between the upper limit USL and the lower limit LSL. 5. The method according to claim 4, characterized in that the path amount of the method step (d) is less than a quarter of the difference between the upper limit value USL and the lower limit value LSL. 6. The method according to any one of claims 1 to 5, characterized in that the axial distance in step (b) is selected such that the maximum of the distribution function for the axial bearing clearance AP is in the range between a desired value SW and the upper limit USL. 7. The method according to any one of claims 1 to 6, characterized in that all process steps (b) to (f) are performed in the same device without re-clamping or replacement of components. 8. A device for carrying out the method according to one of claims 1 to 7, characterized by: a pressing device (10) for receiving the assembly comprising the shaft (30) fixed thereto first bearing member (32) and a third, rotatable on the Shaft arranged bearing component (36), a press ram (18) for pressing the second bearing member (34) on the shaft (30) at a defined distance from the first bearing member (32), a measuring device (22) for measuring the axial bearing clearance AP, and an evaluation device for evaluating the measured bearing clearance AP and for comparing the measured axial clearance AP with a predetermined lower limit value LSL and a predetermined upper limit value USL, wherein the press ram (18) of the pressing device (10) for exerting a defined force impact ΔΡ on the second bearing component ( 34) is formed, wherein pulse and direction of the force pulse .DELTA.Ρ are selected such that the second bearing member (34) is displaced by the force impulse by a defined amount in the direction of the first bearing member (34).