JPH02276938A - Equipment for adjusting axial preload of roller bearing or spindle nut - Google Patents

Abstract

PURPOSE: To enable adjustment in program control according to various operation conditions even during operation by providing a clamp member wherein multiple disclike piezoelectric elements are connected in series mechanically and in parallel electrically. CONSTITUTION: A pre-load adjusting device comprises two cover rings 30 and 31 and a ringlike clamp member 32 positions between them. The clamp member 32 comprises multiple platelike and ringlike piezoelectric elements in lamination. These piezoelectric elements are assigned in series mechanically and connected in parallel electrically, and electrically loaded according to a required axis- direction component. An orientation of a resistance line strain meter 34 provided an one cover ring 30 is so defined that the change in length caused by compression of the cover ring 30 under press can be detected in best manner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is a device for adjusting the axial component for clearance-free preloading of rolling bearings or spindle nuts. Is one tightening member located in and whose adjustment amount is variable? Concerning the format that is provided.

[Conventional technology]

In all cases, especially in the case of machine tools, it is customary to use structures capable of supporting and positioning movable machine parts or workpieces.

For example, is almost all machining mt < the main spindle or work spindle in the form of a rotating shaft? Additionally, the spindle holds a tool and/or a workpiece. The bearing part of such a spindle is of special significance because it is affected by the machining forces and determines the machining accuracy. Preload for Susa 1 compensation? Applied rolling bearings, such as angular roller bearings, tapered roller bearings, or pure thrust bearings, are used. What about quietness, precision and rigidity in bearings? For permanent guarantee, preloading is applied by mechanical means. These preloading means include rigid adjusting elements, such as adjusting discs mounted under the bearing cover, depth-adjustable and centering bearing covers, axle nuts, etc. Alongside this, for example, preload? Atara A
Elastic adjustment means, such as a 7'C disc spring set, are also known. All such preloading means are permanently set during assembly of the machine and are only adjusted during maintenance or overhaul.

In addition to the main spindle or work spindle mentioned above, there is also a feed spindle. Is this feed spindle threaded on its outer periphery? It has one nut fitted into the carriage. In order to move this carriage as precisely as possible, K
The following points need to be considered. That is, if a well-defined contact relationship is provided between the nut thread and the spindle thread, and this contact relationship is specially supported, it will remain accurately set! It is necessary to consider this as much as strictly adhering to the 81 rules.

In order to influence this contact relationship, nuts that are laterally or radially or longitudinally or axially segmented are generally used.

In the case of horizontally split nuts, double nuts are particularly known. The double Nand of C consists of two individual nuts, both nuts being arranged one after the other and tightened together in the axial direction.

The axial preload required for this purpose is set at the factory by the nut manufacturer.

In this case, both nuts are positioned side by side on the spindle and connected in position with one shrink-fit ring. This burn-in ring can be hydraulically removed for later adjustment. As an alternative to this shrink-fit ring type connection, mating keys can also be used in conjunction with other structural parts.

In the case of a vertically split nut, for example, is the tightening mechanism in which two shells act in the circumferential direction? are tightened together through the An undivided nut with just one longitudinal slit on one side is also used. This vertical slit is formed in the radial direction from the inner circumferential surface to the outer circumferential surface of the nut, and the slit width can be varied, for example, via a screw. This also changes the inner diameter of the nut, making it possible to fully compensate for the gap between the nut and the spindle. However, even in this case, the @1 adjustment or the preload adjustment is performed only when the machine is assembled or overhauled.

The disadvantage of such a one-off axial brake setting of the bearing or spindle nut is that this adjustment is directed exclusively to the point of application of the bearing or spindle nut. This point of application is itself preoriented in accordance with the maximum load of the machine, in other words adapted to the requirements of extreme cases.

Therefore, for example in the case of a spindle nut, the preload must be set such that the axial preload in the nut exceeds a minimum value. If the point of action for setting the preload deviates to the average load range, the nut will suffer from cracking under high loads.

A large axial preload, which is known to be constant, is necessary in order to ensure permanent accuracy and high stiffness of the bearing system. However, as the preload increases, the friction in the bearing system also increases. This not only reduces the mechanical efficiency, but also leads to heating and heating effects on the setting accuracy of the bearing system, as well as wear phenomena that significantly reduce the service life of the bearing system. This also applies to bearings and feed spindles.

A permanently set axial preload is particularly problematic in the case of rapid movements at high rotational speeds. This is because in such cases, the combination of preload and high rotational speed generates a large amount of heating, and this heating can cause wear and tear, especially in operating conditions where preload is not safe. ◇ [Problem to be solved by the invention] The problem of the present invention is to solve the problem of the axial component of the preload of the rolling bearing of the type mentioned at the beginning and the spindle nut. An object of the present invention is to enable a device for adjustment to be adjusted in a program-controlled manner even during operation in accordance with various operating conditions.

[Means for solving problems]

A challenge like this? The present invention has been solved as follows. That is, the device has one tightening member, and this tightening member consists of a large number of disc-shaped piezoelectric elements, and these piezoelectric elements are mechanically arranged in series and electrically connected. are connected in parallel, and these piezoelectric elements are electrically loaded in accordance with the required axial component.

Such tightening can be achieved by increasing the thickness of each piezoelectric element! A typical value is a voltage supply of 1 μ'A/100 volts. In this case, a large absolute transmission is required in relation to the size of the disc-shaped surface of the individual piezoelectric element. I can do it.

If the rollers are integrated into the line of force of the 9-bearing and the axial support of the spindle nut, the pressure hemisphere produces a large axial preload due to the voltage supply, which makes it possible to increase the rigidity and precision of the system. If the disc-shaped piezoelectric resistor is short-circuited, its elongation is canceled, thereby reducing the axial preload of the system and creating a gap 1. This reduction in preload or creation of a gap results in reduced friction of the system and thus increased mechanical efficiency. Reducing friction leads to less heating in rolling bearings or spindle nuts, increasing the durability and service life of the respective systems.

For safety reasons, it is advisable to assemble the parts in such a way that a minimum or standard preload is applied in the rolling bearing or in the spindle nut when the system is at rest. Such a preload can cause rolling bearings to damage the machine in which the spindle nut is installed, e.g. by breaking the wire.
It is possible to continue operation even if the reload system fails.

A typical value for such a standard preload is FI3KN. Preload beyond this value? To increase the voltage, a preload force of 1 (IKN) can be obtained by adding, for example, to -700 V'. To produce a blade below the basic setting, for example, +30
0V'(f-add. This f'L makes the preload zero.

In short, the device according to the invention makes it possible, depending on the desired load, to apply a prestress to a rolling bearing or a spindle nut in a machine during operation, or to eliminate this prestress.

In this way, it is possible to provide a preload, for example for machining processes that require precise precision, and for operating modes such as rapid traverse between each machining process or any movement in the rest phase. It can be resolved.

According to an embodiment of the invention, the clamping element is groove-bottomed as a ring body on which the member rests on a rotating shaft or spindle nut. In this case, individual disc-shaped piezoelectric elements are stacked in the axial direction of the ring body. This ring body design and the laminated structure have the advantage, in particular, that they save space.

This tightening element can be arranged in a minimum amount of space, such as in a spindle nut or next to a rolling bearing, and the ring shape is suitable for such applications.

Advantageously, the tightening is limited by one cover ring on each side in the direction of the geometric length change of the component, depending on its function. This allows the ring body, which consists of a piezoelectric element, for example, to be adapted to the support surface of the rolling bearing ring.

Furthermore, at least one of the at least one covering ring
The resistance wire strain can be placed on a plane having an elongation direction that is at least approximately parallel to the direction of length change.

Such a covering ring is arranged within the line of force of the axial support and is therefore compressed by the axial force. The axial force (preload) can be calculated from this compression detected by the resistance wire strain meter and the stiffness of the covering.

In the case of the invention, the clamping element can also be provided with a measuring element next to the element. These two members are connected via a controller. This determines the preload for each time, regardless of system wear or machining accuracy. It can be accurately detected, adjusted and controlled. Electronic processing of resistance wire strain gauges
The preload signal, which is closely related to preload, is sent to the controller. The current value reached at the controller is compared with a setpoint value provided by manual or mechanical control. Is the current value the target value? If less, the tightening will reduce the axial preload by increasing the voltage on the member.

The resistance wire strain gauge in the cover ring does not detect a pure axial preload, but the external axial load and tightening caused by the machine is a superimposed value with the preload caused by the corresponding voltage supply to the component. Since it detects the magnitude of the external axial load? It is necessary to find it and subtract it from the superimposed value. To find the external axial load N, preload?
A length-measuring element can be arranged in the line of force between the bearing rollers or the spindle nut and all these supported machine parts.

In this way, the preload can be adjusted precisely to the particular requirements during operation. Variations in the preload can thus be compensated for via the total controller.

It is preferable that the cover ring provided as a measuring member has seven resistance wire strain gauges on four sides, and in this case, the four faces are uniformly arranged in the circumferential direction on the inner peripheral surface of the cover ring. There may be more than four such surfaces complete with resistance wire strain gauges. Moreover, it can also be provided on the outer periphery of such a surface covering ring. These surfaces do not necessarily have to be flat, and may be curved into a cylindrical shape within a range visible to the naked eye, for example.

The above-mentioned length measuring member that detects the force exerted from the outside into the system is equivalent to a covering ring equipped with a resistance wire strain gauge.

In addition to the previously described control system for adjusting the axial preload under load, other inexpensive circuit configurations are possible. That is, the preload of the rolling bearing or spindle nut can be set to adjust the output before any load is applied to the system. The reference point in this case is the expected load value, which is known on the basis of machine and machining data. Such a setting and power adjustment has the advantage that only one measuring system is required.

Tightening is another possibility for assembling members. In the case of a spindle nut with slots l'f- parallel to the axis, the tightening acting circumferentially on the axial slot is affected by the members. It can also be applied. In this case, a rectangular parallelepiped-shaped laminate member consisting of a large number of disc-shaped piezoelectric elements is placed and supported between both end faces of an axis-parallel slit. The individual piezoelectric elements are located one after the other in the circumferential direction. When this piezoelectric element is energized, it reduces the axial preload of the spindle nut.

The features of the spindle nut are such that the inner diameter of the spindle nut is slightly undersized! ! ! It is based on the points made. The spindle nut thus has a maximum axial preload as well as a maximum radial preload on the spindle. Is the clamping element installed in the slit and supplied with voltage with a smaller preload as required? In addition, a gap 1 is also generated due to elongation in the circumferential direction due to voltage supply. When tightened with such elongation, the member expands within the spindle nut, so that the piezoelectric element is subjected to a larger surface pressure in the inner diameter range than in the outer diameter range due to the return force of the spindle nut. In order to counteract such surface pressures, the stack of piezoelectric elements is bounded on each side by one support element, viewed in its direction of action. Each support member is arranged in this case so that it can be pivoted through a small angle, its pivot axis being parallel to the imaginary center line of the spindle nut. It is preferable that the contact surface between the support member and the slit surface of the spindle nand is cylindrical.

Of course, the piezoelectric element can also be directly fitted into the slit. In this case, consideration must be given to ensuring that the laminate is not pushed outward in the radial direction due to the expansion of the slit, and that the surface pressure exerted on the piezoelectric element does not exceed a predetermined limit value. There is.

Even in such a case, is the tightening a member? It can be combined with length measuring members arranged in series. In this case, the length measuring member is a rectangular parallelepiped block, and at least one resistance wire strain gauge is arranged on the outer or inner surface of the block. The resistance wire strain gauge may be placed on the end face of the block, which is substantially perpendicular to the imaginary center line of the spindle nut.

In summary, the device of the present invention has many advantages, some of which are multifaceted. For example, in the case of spindle drives (Hall screw drive, roller screw drive, see-through roller screw drive, etc.), the device according to the invention can be used in two ways at the same time; Therefore, it can be used for the axial preload of the spindle nut which is moved by the spindle on the other side.

The axial bearing may in such a case be constructed in such a way that at least the axial component of the bearing is oriented towards the shaft end. In such an arrangement, the variable clamping element can serve as a regulating element in a closed-loop control system, such that the shaft is permanently subjected to axial tensile stress during operation. In this case, the axial preload can be adapted to the thermal expansion of the shaft. The tightening means that the measuring member connected to the member detects any reduction in axial load due to thermal elongation of the shaft. The tightening is countered by an additional voltage supply to the component. The increase in axial force obtained in this way not only increases the bearing accuracy and bearing quietness, but also improves the resonance frequency of the spindle held between the bearings. Ru. This is because the preload in the longitudinal direction has a damping effect.

At the same time, a double nut mounted, for example on a spindle, can also be preloaded via a variable tightening element. In this case, the axial preload causes a large force noise inside the system of nut and spindle. In short, the rolling bearing has a supporting effect more than ever before.

This increases the static and dynamic stiffness of the system, which also has a positive effect on the Im accuracy.

If great precision is not required, for example during preparatory movement or rapid forwarding, the preload can be eliminated by shorting the piezoelectric element.

This significantly reduces friction and thus also heat loss. This leads to increased efficiency, permanence of accuracy and service life of the bearing and all systems involved in the movement.

〔Example〕

The invention will now be explained according to the exemplary embodiments shown in the drawings: FIG. 1 shows a stationary bearing for supporting a shaft part in a housing.

The primary part of this bearing is a double row angular contact ball bearing 1.

The inner ring 2 of this bearing is fitted onto the shaft portion 3 and has one end abutted against the shaft collar 4. The inner ring 2 is press-fitted to the shaft collar 4 via a shaft nut 5 and a sleeve 6.

A divided outer ring of the angular contact ball bearing 1 is arranged within the housing 7. This outer ring consists of two rings 8,9. The ring 8 is attached to the inner flange 10 of the housing 7
is supported by

Ring 9 includes bearing cover 11 and preload adjuster 12
is held in place by the

The bearing cover 11 is fixedly screwed to the housing γ. The housing 7 is fixed via a length measuring member 13 to a mechanical part 14 that supports the entire bearing. In this case, the length measuring element 13 serves to detect the external force exerted between the housing 7 and the mechanical part 14.

One of the preload regulators is shown in FIG. This preload regulator essentially consists of two cover rings 30, 31 and a ring-shaped clamping element 32 located between them. The tightening member 32 is composed of a large number of laminated flat ring-shaped piezoelectric elements.

The cover ring 30 has four rectangular grooves 33 on the inner surface of its central hole 37. These grooves 33 are each angularly shifted by f130 degrees. The flat surface at the bottom of each groove is used to receive a resistance wire strain gauge 34. Each resistance wire strain gauge is oriented to best detect changes in length due to compression of one covering ring under pressure. The radial bore 35 and the axial bore 36 are used for guiding the measuring wire.

The preload regulator thus constitutes an adjustment element in which the force measuring part is integrated. For example, when assembled into the angular contact ball bearing 1 shown in Fig. 1, the preload adjuster changes its length in the axial direction by supplying voltage to the piezoelectric element. axial preload is thereby transmitted to the angular contact ball bearing 1. In this case, does the preload decrease the bearing clearance in both the axial and radial directions?
arise. Also within the brake load regulator itself, the cover ring 30 (FIG. 3), which in this case has a resistance wire strain gauge 34, is compressed.

This compression causes a resistance change within the resistance wire, which resistance change is processed separately in the evaluation electronics, for example to make the axial blemish larger or smaller depending on the load.

FIG. 4 schematically shows a control circuit block diagram for this purpose. The illustrated closed loop control system includes a control circuit 40, a high voltage amplifier 41, a piezoelectric adjustment member 42 corresponding to the tightening member 32 in FIG. 6, and a measuring member 43 corresponding to the covering ring 30 in FIG. It consists of

When the preload in the axial direction is set in the control circuit 40 as the target value 44, the control circuit 40 converts this set value into a constant current value 45 measured at the measuring member 43 and a force (external force) exerted from the outside on the system. Tightening in the bearing or in the nut is compared with the current deviation value 45 calculated by superimposing it with the force. At the same time, pure axial preload? An external force Fax is supplied to the control circuit for determination.

This external force Fax is applied to the length measuring member 1 shown in FIGS. 1 and 2.
3. Uke is taken through 26. If the actual value falls below the setpoint value, the control circuit 40 causes an additional voltage supply to the piezoelectric element in the regulating element 42 via the high-voltage amplifier 41 . The resulting length changes within the force line bundle are detected by the measuring member 43 and fed back to the control circuit 40.

The setpoint value 44 can be supplied externally, for example by a computer, and can thus be varied to adapt it to the machining purpose of the machine in which the axial preload adjuster receiver, for example in an axial bearing, is installed. It is thus possible, for example, for rapid traverse, to completely eliminate the preload and apply it again just before braking and positioning are introduced.

Of course, it is also possible to make do with just the measuring member 43 provided next to the adjusting member 42. In this case, however, the axial preload chip must be adjusted before external loads are applied. This is because post-adjustment is not possible when the goods have been received. First, the measuring member near the tightening member not only detects the preload force applied from the tightening member, but also detects the axial component t of the force acting on the system from the outside. .

FIG. 2 shows a double nut 21 of a ball screw drive with a device for generating and measuring the axial preload.

A double nut 21 is arranged on the ball screw spindle 20. This double nut 21 consists of two independent ball screw nuts (22, 23). Is the assembly of one ball screw nut 22U a flange, that is, a double nut? f
- For example, the assembly, which is fixed to the carriage, has a flange.

An adjustment member 24 is placed between both ball screw nuts 22 and 23.
and a measuring member 25 are arranged.

The adjusting member 24 corresponds to the tightening member 23 in FIG. 6, and the measuring member 25 corresponds to the covering ring 30 (resistance wire strain acupuncture @) also shown in FIG.

In this case, too, the voltage supply to the adjusting element causes an axial length change of the adjusting element, which causes the two ball screw nuts 22, 23 to be pushed apart from each other in the axial direction. This causes both nuts to tighten each other, which in turn causes the ball screw spindle and the double nut 21 to tighten.
The rigidity of the combination is increased. The magnitude of the axial preload is detected by a measuring element 25.

The double nut 21 is preferably fixed via a length measuring member 26 to the mechanical part 27 supporting the double nut. In this case, the lateral members 26 serve to detect the external force exerted between the double nut 21 and the mechanical part 27.

FIG. 5 shows a nut with a slit equipped with a device for completely eliminating axial preload. This nut is assembled with a ball nut body 50, a flange 51, and a pressure shell 5.
The rectangular parallelepiped fastening member 52 has three parts. The pole nut body 50, together with its internal ball screw thread, is manufactured in such a way that it is mounted on the ball screw spindle and leaves a so-called negative clearance 1. (1#), originally set to match the maximum axial and radial preload. The radial preload is loosened by a rectangular parallelepiped clamping member inserted without gap 1 into the slit 54, which is also supported in the slit 54 via pressure shells 53 on both sides by the clamping member 52. be able to. To eliminate this preload in the radial direction, the tightening that acts in the circumferential direction of the pole nut body 500 as voltage is supplied is achieved by changing the length of the member. In this case, the pole nut body 50
The space between the ball screw spindle and the ball screw nut inserted together with the ball (not shown) is
l is given.

Nuts like this are structurally simple and can be manufactured at low cost.
Practically equal axial loads] 1 - Suitable for loads in applications where they can bear virtually equal axial loads. For application points of this type, the prestress is fixed in terms of manufacturing technology. During rapid traversal in the machine, the nut is released from the prestress by the tightening member, so that the nut moves lightly through a small clearance. Thus, only during rapid forwarding, unnecessary wear is avoided as a result of reduced frictional heating.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of a roller bearing equipped with the device of the present invention, Fig. 2 is a schematic longitudinal sectional view of the ball screw drive mechanism, Fig. 6 is an end view and longitudinal sectional view of the adjusting member, and Fig. 6 is a longitudinal sectional view of the ball screw drive mechanism. FIG. 4 is a block diagram showing a control system for operating the apparatus of the present invention, and FIG. 5 is a perspective view of a nut with a slit. 1...Double row angular contact ball bearing, 2...Inner ring, 3...
・Shaft part, 4...Shaft collar, 5...Shaft nut, 6...
- Sleeve, 7... Housing, 8, 9... Ring, 11... Bearing cover 12... Preload adjuster, 13... Length measuring member, 14... Mechanical part, 30.3
1...Cover ring, 32...Tightening member, 33.
... Groove, 34... Resistance wire strain meter, 40... Control circuit, 41... High voltage amplifier, 42... Piezoelectric adjustment member, 43... Measurement member, 44... Target value, 45
... Current value, 20 ... Ball screw spindle, 21
. . . Double nut, 24 . . Adjustment member, 25 . . . Measuring member, 26 . - Tighten the members, 53...Bearing shell, 54...Slit.

Claims (1)

[Claims] 1. A device for adjusting the axial component for clearance-free preloading of a rolling bearing or a spindle nut, the device being arranged within the flux of lines of force of the axial support so that the amount of adjustment is variable. In the type equipped with one clamping member, the clamping member (12, 24, 32, 52) is composed of a large number of disc-shaped piezoelectric elements, and these piezoelectric elements are mechanically arranged in series. device 2 for adjusting the axial component, characterized in that the piezoelectric elements are electrically connected in parallel and are electrically loaded in accordance with the required axial component; 3. The device 3 according to claim 2, wherein (12, 24, 32) is configured as a ring body surrounding the shaft or spindle, and the individual disc-shaped piezoelectric elements are stacked in the axial direction of the ring body. 3. Device 4 according to claim 2, characterized in that the clamping member (32) is limited on each side in the direction of functionally-based geometric length change by a covering ring (30, 31). 1, wherein at least one covering ring (30) is provided with a resistance wire strain gauge (34) on at least one surface, which also produces a direction of elongation at least approximately parallel to the direction of length change. Device 6 according to claim 4, wherein the covering ring (30) has four sides provided with resistance wire strain gauges (34); Device 7 according to claim 5, wherein the four sides are provided with a covering ring (30) 7. The device 8 according to claim 6, wherein the clamping members (24, 32) are adjusting members (42) and the resistance wire strain gauge (34) is uniformly distributed in the circumferential direction on the inner surface (37) of the Any one of claims 1 to 7, which is a measuring member (43) of a closed loop control system.
In the device 9 described in section 9, the axial clearance of the spindle nut in which the slit is formed parallel to the axis is influenced by one tightening member (52) that acts in the circumferential direction.
) is one rectangular parallelepiped-shaped laminate made of disk-shaped piezoelectric elements, and this laminate is arranged between the end faces of the slit (54) and supported by these end faces.
The device 10 according to claim 1, wherein the individual disk-shaped piezoelectric elements of the laminate are arranged one after the other in the circumferential direction, the device 11 according to claim 1, comprising a length measuring member in which a tightening member is connected in series. The combined device 12 according to any one of claims 1 to 10, wherein the length measuring member is one rectangular parallelepiped block,
Device 13 according to claim 11, characterized in that at least one resistance wire strain gauge is arranged on the outer or inner surface of this block, the axial preload of the spindle nut (50, 51) being reduced by the voltage supply of the piezoelectric element. 14. Device 14 according to claim 10, wherein the stack of piezoelectric elements is bounded on each side in its direction of action by a support member (53), each support member according to claim 10. (53) is arranged in the cap nut (50) so as to be pivotable through a small angle, the pivot axis being parallel to the imaginary center line of the spindle nut. (13, 26) is arranged in a line of force between a rolling bearing or a spindle nut subjected to preload and a machine part supporting this bearing or nut. or the device described in item 1.