Rolling bearing device

A rolling bearing device has an oil supply unit which includes: a lubrication oil tank with a discharge port of a lubrication oil; a pump which sucks the lubrication oil from the lubrication oil tank and discharges the lubrication oil; and an electric power source section for driving the pump. The oil supply unit is disposed inside the rolling bearing or inside a spacer which is placed adjacent to the rolling bearing, and the pump is operated intermittently. The electric power source section for driving the pump includes: a power generator section which generates power by temperature difference between inner and outer rings in the rolling bearing; and a charging section which stores the electric power from the power generator section. The pump is driven when a voltage in the charging section attains a driving voltage for the pump.

TECHNICAL FIELD

The present invention relates to rolling bearing devices used in machine tools, industrial machinery, etc., and particularly to a rolling bearing device constituted as a combination of a rolling bearing and an oil supply unit.

BACKGROUND ART

A rolling bearing device which incorporates an oil supply unit therein is conventional (see JP 2004-108388A). In this rolling bearing device, an oil supply unit is mounted on an inner diameter surface of one of two mutually opposed track rings of the rolling bearing, or a fixed-side track ring in this case. The oil supply unit includes a lubrication oil tank which stores lubrication oil; a pump which pumps out the lubrication oil stored in the lubrication oil tank into the bearing; and an electric power generator which drives the pump. The device also includes means which controls the pump in accordance with bearing conditions thereby controlling an amount of discharged oil.

JP 2005-180629A discloses a rolling bearing device, which is loaded with grease therein. A lubrication oil of the same kind as the base oil of the grease is stored in a spacer adjacent to the rolling bearing. The lubrication oil inside the spacer is supplied to inside of the rolling bearing by means of capillary action.

However, the arrangement such as disclosed in JP 2005-180629A, that lubrication oil inside the spacer is supplied to inside of the rolling bearing by capillary action, often results in excessive supply of the lubrication oil.

Also, the lubrication oil stored in the spacer is consumed quickly, posing a problem that stable, long-term supply of lubrication oil is impossible.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a rolling bearing device which is capable of supplying lubrication oil to the rolling bearing stably for a long time.

Solution to Problem

In order to solve the problems described above, the present invention provides a rolling bearing device including an oil supply unit which has: a lubrication oil tank with a discharge port of a lubrication oil; a pump which sucks the lubrication oil from the lubrication oil tank and discharge the lubrication oil; and an electric power source section for driving the pump. The oil supply unit is disposed inside a rolling bearing or inside a spacer which is placed adjacent to the rolling bearing, and the pump is operated intermittently.

Since the pump is operated intermittently, excessive supply of the lubrication oil can be avoided and stable supply of the lubrication oil for a long term is achieved.

In order to operate the pump intermittently, the electric power source section for driving the pump may include, for example: a power generator section which generates power by way of temperature difference between an inner and an outer rings in the rolling bearing; and a charging section which stores the electric power from the power generator section; and with this arrangement, the pump is driven when a voltage in the charging section attains a pump driving voltage.

As another arrangement, the pump maybe driven to perform the first supply of the lubrication oil after the voltage in the charging section is held for a predetermined time since the voltage in the charging section attains the pump driving voltage.

Also, there may be an arrangement that a cycle of charging to and discharging from the charging section is repeated for a plurality of times before the pump is driven to perform the first supply of the lubrication oil.

Further, there may be an arrangement that an operation interval of the pump is controlled by a timer for holding the voltage in the charging section for a predetermined time in accordance with an operation time of the rolling bearing after the first supply of the lubrication oil is performed by driving the pump.

Still further, the pump operation interval may be controlled by changing a number of times for which the cycle of charging to and discharging from the charging section is repeated, in accordance with an operation time of the rolling bearing.

Advantages of the Invention

According to the present invention, the pump is operated intermittently, whereby excessive supply of the lubrication oil is avoided, and stable, long-term supply of the lubrication oil is achieved.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described based on the attached drawings.

A rolling bearing device10according to an embodiment shown inFIG. 1throughFIG. 3includes a rolling bearing11; a spacer12press-contacted onto an axial end of the rolling bearing; and an oil supply unit13incorporated in the spacer12; and when used, is assembled into a space between a rotation shaft14and a housing15. The rolling bearing11has another end, on which another spacer16is press-contacted. These two spacers12,16provide axial positioning of the rolling bearing11. The rotation shaft14in this embodiment is horizontal.

The rolling bearing11may be provided by whichever of an angular contact ball bearing and a deep groove roller bearing, and includes an inner ring17, which is a rotation-side track ring; an outer ring18on a fixed side; a predetermined number of rolling elements19placed between these track rings; and a retainer21which keeps a predetermined distance between the rolling elements19. The rolling bearing11is pre-packed with desirable grease, and a seal plate22is attached to an end on the spacer16side.

The spacer12includes an inner-ring-side spacer12aand an outer-ring-side spacer12b. The inner-ring-side spacer12ais fitted in and fixed to the rotation shaft14side, and is press-contacted onto an end surface of the inner ring17. The outer-ring-side spacer12bis fitted in and fixed to an inner diameter surface of the housing15, and is press-contacted onto an end surface of the outer ring18. The other spacer16is also fitted in and fixed to the rotation shaft14side and the housing15side in the same fashion, and is press-contacted onto the other end surfaces of the inner ring17and of the outer ring18.

As shown inFIG. 3, the oil supply unit13includes an annular housing24and various components housed therein in a circumferential direction. The components include a power generator section41, a charging section42, a controller section43, a driving section44, a pump45, a lubrication oil tank46, etc.

As shown inFIG. 2, the annular housing24of the oil supply unit13is constituted by a housing main body24awhich has a generally U-shaped section with an open end facing away from the rolling bearing11; and a lid24bwhich closes the open end of the housing main body24aand is detachable from/attachable to the housing main body24a. The housing main body24aand the lid24bare made of the same thermally plastic resin material such as PPS.

The lid24bof the housing24is fixed to the housing main body24awith screws24c. By unscrewing the screws24cand removing the lid24b, it becomes possible to replenish the lubrication oil tank46inside the housing main body24a, with lubrication oil without removing the entire oil supply unit13.

The housing main body24ahas its outer circumferential surface adhesively fixed to an inner diameter surface of the outer-ring-side spacer12b. The adhesive for fixing the housing main body24amay be provided by epoxy resin for example.

FIG. 4shows an embodiment in which the housing24is fixed without using an adhesive, to the inner diameter surface of the outer-ring-side spacer12b.

In this example inFIG. 4, a pair of recesses12c,12dreceding in a radially outward direction are formed on both axial sides of an inner diameter surface of the outer ring-side spacer12b;the housing main body24ahas an outer diameter surface on the rolling bearing11side, where there is formed a ridge24dto fit into the recess12c, and this ridge24dis fitted into the recess12c;the other recess12dis fitted by an outer diameter portion of the lid24bwhich is fixed to the housing main body24awith screws24c, so that the lid24bis screw-fixed to the housing main body24aby the screws24c. Thus, the inner diameter surface of the outer ring-side spacer12bis sandwiched by the ridge24dof the housing main body24aand the outer diameter portion of the lid24b, thereby fixing the housing24to the inner diameter surface of the outer ring-side spacer12b, without using an adhesive.

Next, the lubrication oil tank46which is incorporated inside the housing main body24ais provided by a bag46aof an elastic resin, and is disposed in an arcuate form along the annular housing24.

As shown in an enlarged view inFIG. 5, the plastic bag46ais, for example, made of a resin film, by placing a sheet of the resin film on another, and then thermally welding their perimeters. InFIG. 5, a reference symbol46bindicates the thermally welded region.

The bag46ais provided with a suction tube45awhich leads to the pump45. The suction tube45ais integrated with the bag46aby sandwiching the tube between two films of resin for forming the bag46aand then performing the thermal welding to complete the bag46a.

FIG. 6shows a bag46awhich is formed by blow molding. When the bag46ais formed by blow molding, a suction tube45amay be blow-formed integrally with the bag46a.

Desirably, however, the bag46aof the lubrication oil tank46formed by blow molding should receive a flattening process to flatten a bag portion since the bag portion is bulged as it is formed in the blow molding process. By altering the shape of the bag to a flat shape, the bag becomes possible to discharge lubrication oil completely even after the amount of the lubrication oil has become small. This way, it is possible to completely consume the lubrication oil stored in the bag46a.

The bag46awhich constitutes the lubrication oil tank46can be formed of such a material as nylon, polyethylene, polyester and polypropylene; there is no specific limitation to the material as far as the material is not attacked by lubrication oil stored in the bag46a.

The suction tube45awhich is provided in the bag46aof the lubrication oil tank46is preferably detachable from the pump45. The suction tube45awhich is detachable from the pump45allows the suction tube45ato be removed from the pump45for replenishing lubrication oil from the suction tube45ainto the bag46awhen lubrication oil level becomes low in the lubrication oil tank46.

Also, the bag46awhich is detachable from the pump45allows such a replacement system that lubrication oil is loaded in a replacement bag46a, and when there is no more lubrication oil left in the original bag46a, then the used bag46ais taken out and is replaced with the replacement bag46a. In this way, replenishing lubrication oil can be finished within a short time. Since the replacement bag46acan be loaded with lubrication oil under a controlled environment in the lubrication oil manufacturer, it is possible to reduce such a risk as foreign matter inclusion in the bag46aat the time of loading oil. It should be noted here that a lid should desirably be placed to the suction tube45aof the replacement bag46ain order to prevent foreign matter inclusion during storage.

Lubrication oil which is loaded in the lubrication oil tank46desirably has a viscosity of VG22 for example, since an excessively high viscosity will bear too much burden on the pump and the power source.

Next,FIG. 7shows another embodiment. In this embodiment, there is no need for removing the bag46aout of the housing24or removing the lid24bwhen replenishing the bag46aof the lubrication oil tank46with lubrication oil. In other words, it is possible to fill the bag46awith lubrication oil from outside while the bag46astays inside the housing24.

As shown inFIG. 7, a through-hole25is made radially, from an outer circumferential surface of the housing15in which the rolling bearing device10is installed, to inside of the housing24in the oil supply unit13. When replenishing lubrication oil, a lubrication oil syringing needle26is inserted through the through-hole25into the bag46ainside the housing24, to fill the bag46awith the lubrication oil. A lubrication oil injection port28which is made of a highly elastic rubber is provided at a place in the bag46awhere lubrication oil syringing needle26is inserted so that insertion/removal of a needle tip27of the lubrication oil syringing needle26will not cause leakage of lubrication oil.

The housing15in which the rolling bearing device10is installed, the spacer12, the radial through-hole25made in the housing24of the oil supply unit13, and the lubrication oil injection port28in the bag46aare circumferentially aligned with each other at the time of assembling.

In each of the embodiments described thus far, the annular housing24houses, the power generator section41, the charging section42, the controller section43, the driving section44, the pump45, etc. in its circumferential direction, in addition to the lubrication oil tank46.

As shown inFIG. 8, the power generator section41may be provided by, for example, an element which generates electric power by way of Seebeck effect. When the rolling bearing device10is operating, temperature of the inner ring17and the outer ring18increases due to heat caused by friction with the rolling elements19(seeFIG. 1). In general configuration, the outer ring18is assembled into the housing15of the machine it serves, and therefore loses heat by thermal conduction, resulting in temperature difference between the inner ring17and the outer ring18. Different temperatures conducted to the respective heat conductors52,53causes the Seebeck element54to have temperature difference between its two end surfaces, causing the element to generate electric power according to Seebeck effect.

When using the above configuration where heat conductors52,53are provided to penetrate the inner circumferential surface and the outer circumferential surface of the housing main body24arespectively and a Seebeck element54is placed between these heat conductors52,53, an adhesive having good heat conductivity should desirably be used on a surface where the heat conductor52which penetrates the outer circumferential surface of the housing main body24amakes contact with the inner diameter surface of the outer ring-side spacer12b. It should be noted here that the heat conductor52which is on the outer ring-side has its outer diameter equal to an inner diameter of the outer ring spacer12band is fitted thereto for improved heat radiation. On the other hand, the heat conductor53which is on the inner ring side has its inner diameter not in contact with the inner ring spacer12a. If possible, it is desirable that the outer ring-side and the inner ring-side heat conductors52,53have the same volume.

Preferably, thermal grease, for example, should be applied between the inner diameter surface of the outer-ring-side spacer12band the heat conductor52; between the heat conductor52and the Seebeck element54; and between the Seebeck element54and the inner-ring-side heat conductor53, for improved contact and heat conductivity. Thermal grease generally contains silicone as a primary ingredient. The heat conductors52,53should be made of a metal which has a high heat conductivity rate. For example, silver, copper, gold, etc. are good candidates, among which copper is the most common due to cost reasons. In addition, copper alloys which contain copper as a primary ingredient can also be used. Further, sintered alloys containing copper as a primary ingredient are also usable.

Electric charge generated by the power generator section41is stored in the charging section42which is provided by a storage battery, condenser, etc. If a condenser is employed, an electric double layer condenser (capacitor) is desirably used.

As shown inFIG. 9, the controller section43has sensors such as a bearing temperature sensor47a, a bearing rotation sensor47b, a lubricant remaining quantity sensor47c, and a lubrication oil temperature sensor47d. Signals from these sensors are inputted to a CPU51, which then automatically controls the pump45in accordance with temperature and rotation status of the rolling bearing11, thereby controlling the amount of lubrication oil supply.

The pump45has a suction tube45awhich sucks lubrication oil from the lubrication oil tank46; and a discharge tube45bfrom which the sucked lubrication oil is discharged. The discharge tube45bhas a discharge nozzle45cat its tip, from which lubrication oil is supplied to between the fixed-side track ring and the rotation-side track ring of the rolling bearing11.

Although the pump45can be driven whenever the electric power stored in the condenser of the charging section42has attained a predetermined voltage, it is desirable that the following interval is utilized for extended lubrication life of the rolling bearing11which has grease sealed therein, and for extended operation hours between maintenance services.

For example, as shown inFIG. 10, in cases where charging time of the charging section42to attain a required voltage for driving the pump45is shorter than a required lubrication oil supply timing, a predetermined charging time (delay time) is added to extend the lubrication oil supply interval even after a full-charge state.

As another example for extending lubrication oil supply interval,FIG. 11shows an arrangement that the charging section42repeats a cycle of discharging its voltage once the voltage reaches a predetermined level, then being re-charged and thereafter discharging again upon achieving the predetermined voltage, until a sufficiently long lubrication oil supply interval is achieved.

Since the power generator section41makes use of temperature difference in the rolling bearing11for generation of the electric power, the amount of generated power will increase when there is a large temperature difference, i.e., when the inner ring17of the rolling bearing11has a high temperature, and this in turn shortens the charging time to the charging section42. On the contrary, when the inner ring17of the rolling bearing11has a low temperature, the temperature difference is small, the amount of generated power is small, and this in turn extends the charging time to the charging section42.FIG. 11shows a case in which the inner ring17of the rolling bearing11has a higher temperature difference and the charging time is shorter than in the case inFIG. 12, whereasFIG. 12shows a case in which the inner ring17of the rolling bearing11has a smaller temperature difference and the charging time is longer.

As described, the lubrication oil supply interval varies depending on the temperature difference of the inner ring17of the rolling bearing11.

Generally, a long lubrication oil supply interval is acceptable if the rolling bearing11has favorable internal lubrication conditions and there is only a small temperature increase inside the rolling bearing11, whereas a short lubrication oil supply interval is desirable if the rolling bearing11does not have very good internal lubrication conditions because such conditions cause a large temperature increase inside the rolling bearing11.

This means that the arrangement which makes use of temperature differences in the rolling bearing11for power generation provides an advantage that the lubrication oil supply interval changes automatically depending on the load born by the rolling bearing11whereby internal lubrication conditions of the rolling bearing11are always maintained favorably.

In an arrangement as described as the above where temperature difference in the rolling bearing11is utilized for power generation, there can be a case where power generation efficiency is too good and the charging time is too short. In such a case, the stored voltage may be discharged to, e.g., a resister upon attaining a predetermined voltage value, thereby providing a time interval in the operation timing of the pump45. In this case, there is a cycle(s) of charging and discharging before the pump45is operated. The number of this charge-discharge cycles can be used in controlling the operation interval of the pump45. As another example, a timer function may be triggered when the power storage voltage is reached a predetermined value, to provide an interval in the operation cycle of the pump45. In this case, the above-described charge-discharge cycle is not repeated.

In cases where the rolling bearing11is provided by a grease-sealed type, the grease sealed inside the rolling bearing11provides sufficient lubrication during an initial operation period. Therefore, as shown inFIG. 13, there may be an arrangement for these, that the first supply of the lubrication oil is started after the grease inside the rolling bearing11has ended its greasing life (e.g. 20,000 hours). Delaying the first supply of the lubrication oil as described, prolongs the life of the rolling bearing11, and prolongs the time to maintenance.

The suction tube45a, which is connected to the suction side of the pump45, extends into the lubrication oil tank46to suck lubrication oil stored in the lubrication oil tank46.

On the other hand, the discharge tube45bwhich is connected to the discharge side has its tip connected to a discharge nozzle45cfor discharging lubrication oil into the rolling bearing. It is desirable that the discharge nozzle45chas its tip disposed at a location between the inner and the outer rings of the bearing, closely to the inner ring's outer circumferential surface. The discharge nozzle45chas a nozzle hole of an appropriate inner diameter based on a relationship between surface tension due to base oil viscosity and the amount of discharge.

It should be noted here that the above embodiment is an example of inner ring rotation. Also, it has a horizontal rotation axis; however, the axis may be vertical. Further, it may be incorporated in a machine tool spindle.

REFERENCE SIGN LIST