DE112017001483T5 - SPINDLE BALL BEARINGS WITH BUILT-IN MOTOR - Google Patents

Abstract

An object of the present invention is to provide a bearing which does not easily dispense grease and base oil and has a long and stable lubricating life, while the lubricating property is maintained in the high-speed operation even in the state where air flows through the bearing. A high-viscosity grease G2 is filled in an air-sensitive region having side surfaces of the holder 14 on an inner ring side. The high-viscosity grease G2 makes it unlikely that a low-viscosity grease G1 mainly located on an inner diameter side of an outer race 12 and having excellent lubricating properties in high-speed operation and also the base oil will flow out, thereby ensuring a long and stable lubricating life.

Description

TECHNICAL AREA

The present invention relates to ball bearings for small spindles, and more particularly to spindles with built-in motor.

STATE OF THE ART

Small spindles are mainly used in a light-duty machining operation such as aluminum machining.

In recent years, the number of small spindles of a type like those in 7 for the sake of compactness one in a housing 1 built-in engine 2 (Patent Literature 1). In 7 A symbol W indicates a grindstone for grinding an object to be processed (workpiece).

As a spindle ball bearing with a built-in motor 3 For example, because of its advantages in high-speed operation and its small displacement of the main shaft, an angular contact ball bearing is often used to promote a high-precision machining operation upon occurrence of an external load exerted by the tip of the main shaft at the time of machining.

For these types, where the spindle itself is a motor 2 Inside, it is necessary to provide a cooling arrangement to prevent a decrease in machining accuracy caused by the change in the overall size of the spindle due to the by the motor 2 and the camp 3 heat generated during continuous operation.

A well-known example of the cooling arrangement is an outer shell cooling arrangement in which a cooling fluid around a housing 1 the spindle circulates. However, the outer jacket cooling arrangement requires increasing the outer diameter of the spindle and adding seals to prevent the cooling fluid from escaping. In other words, it tends to require a complicated structure.

For these reasons, air that does not require a complicated structure is used as the primary medium around the interior of the housing 1 the spindle with built-in motor to cool.

The air that is the interior of the case 1 the spindle cools, provides in the order of the engine 2 over the camp 3 for cooling from behind, after which the air from a tip portion of the housing 1 the spindle to the outside of the housing 1 the spindle is released.

The top section of the housing 1 The spindle also serves as a seal against flying objects. By means of an air curtain and a labyrinth seal, the pressure within the housing 1 Increase the spindle, prevents cutting fluid, machining dust, etc. in the housing 1 penetrate the spindle.

4 shows a spindle ball bearing with built-in motor 3 in which between an inner diameter portion of a seal plate 5 and an outer diameter portion of an inner ring 6 a labyrinth structure is provided, and in which the inner diameter portion of the seal plate 5 in a sealing groove 7 located in the outer diameter portion of the inner ring 6 is formed, is fitted. In 4 denotes a reference numeral 8th a holder, a reference numeral 9 an outer ring and a reference numeral 10, a rolling element (rolling elements).

In the labyrinth structure described above, the seal plate tends 5 to prevent air in the warehouse 3 is ejected. As indicated by the arrows in 4 shown, the air in the ball bearing 3 Turbulence flows within the bearing 3 cause the holder 8th begins to vibrate.

The vibrations of the holder 8th be on the case 1 transmitted to the spindle, whereby the noiseless operation of the operation is adversely affected.

In view of this, the applicant of the present invention has a patent application (Patent Literature 2 ) for a spindle bearing with a built-in motor capable of uniformly discharging cooling air entering the bearing of the spindle with built-in motor from the bearing without causing turbulence flows inside the bearing. In this arrangement, as in 6 shown has a sealing plate 5 a predetermined length in an inner diameter direction to allow the flow of air through the bearing from an input side to an output side substantially straight (directly) without resistance, so that a holder 8th does not vibrate easily and a very quiet operation is maintained.

CITATION

Patent Literature

• Patent Literature 1: JP-U 3150371 gazette
• Patent Literature 2: JP-A 2016-23719 gazette

SUMMARY OF THE INVENTION

TECHNICAL PROBLEM

A spindle bearing with built-in motor often has to work even with grease lubrication in a high-speed operation of 0.5 million to 1 million dn.

For this reason, grease used in the engine-mounted spindle ball bearing is excellent for high-speed operation. In other words, the grease can form a lubricating film with a very small amount of lubricant, has a low stirring resistance even in high-speed operation, and has no temperature rise. In addition, to reduce the stirring resistance, a base oil of the grease should preferably have a low viscosity; more specifically, a common range of grease viscosity is 20 to 40 mm ² / S (40 ° C), with a walk penetration of 200 to 300.

When high-speed operation is a high priority, among others, a grease having a base oil viscosity of 20 to 30 mm ² / S (40 ° C) and a milling penetration of 200 to 230 is used.

However, the spindle ball bearing has a built-in motor 3 according to the patent literature 2 a structure that allows a flow of air through the bearing, and the amount of air flowing through can be up to 10 to 30 Nl / min. Greater air flow within the bearing will cause the originally charged grease or base oil to be discharged in a larger amount, and this is especially true for the group of greases that have better high speed lubrication, ie those having a base oil viscosity of 20 to 30 mm ² / S (40 ° C) and a walk penetration of 200 to 230.

It is thus an object of the present invention to provide a bearing which does not easily dispense grease or base oil and has a long and stable lubricating life, while in a high-speed operation, even when air flows through the bearing, lubricating properties are maintained.

THE SOLUTION OF THE PROBLEM

In order to solve the above-described problem, the present invention provides a spindle motor-incorporated ball bearing comprising: an inner ring; an outer ring; Rolling elements disposed between opposing rolling surfaces of the inner ring and the outer ring; a holder holding the rolling elements; and a seal plate extending from an inner diameter surface at each end of the outer ring toward the inner ring; and wherein the sealing plate has a radially inwardly-directed length with a dimension such that a flow of air substantially directly without resistance from an input side to an output side through the bearing is possible; wherein the outer ring and the inner ring have a portion holding two kinds of grease therebetween, one formed of a low viscosity grease located mainly on an inner diameter side of the outer ring and the other formed of a high viscosity grease is located in an air-sensitive area, which includes side surfaces of the holder on an inner ring side.

The low-viscosity grease, which is mainly on the inner diameter side of the outer ring, has a base oil viscosity in a range of 20 to 30 mm ² / S (40 ° C) and a worked penetration in a range of 200 to 230, while the high-viscosity grease, which is in the air-sensitive region comprising the side surfaces of the holder on the inner ring side, has a base oil viscosity in a range of 30 to 40 mm ² / S (40 ° C) and a walk penetration in the range of 240 to 260.

ADVANTAGEOUS EFFECTS OF THE INVENTION

While the spindle ball bearing with In accordance with the present invention, a built-in engine having a structure that allows air to flow through the bearing, the high-viscosity grease is filled in the air-sensitive areas, which include the side surfaces of the holder on the inner ring side. The high-viscosity grease makes it less likely that the low-viscosity grease, which is mainly on the inner diameter side of the outer ring and has excellent lubricating properties in high-speed operation, and also the base oil, thereby ensuring a long and stable lubricating life.

list of figures

• 1 shows a partial cross-sectional view of a spindle bearing with built-in motor according to the present invention.
• 2 shows an enlarged partial view illustrating the guiding of a holder of the spindle motor with built-in motor according to the present invention.
• 3 FIG. 11 is an enlarged fragmentary view illustrating the guidance of a holder according to another embodiment of the engine-mounted spindle ball bearing according to the present invention. FIG.
• 4 shows a partial cross-sectional view of a conventional spindle ball bearing with built-in motor.
• 5 shows an enlarged partial view illustrating the guide of a holder of the conventional spindle bearing with built-in motor.
• 6 shows a partial cross-sectional view of a spindle ball bearing with built-in motor according to patent literature. 2
• 7 shows a schematic drawing of a spindle with built-in motor.

DESCRIPTION OF THE EMBODIMENTS

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

As in 1 As shown, a spindle bearing with built-in motor according to an embodiment of the present invention is an angular contact ball bearing.

The angular contact ball bearing according to the present invention comprises: an inner ring 11 , an outer ring 12 ; rolling elements 13 that lie between opposing rolling surfaces of the inner ring 11 and the outer ring 12 are arranged; a holder 14 that the rolling elements 13 holds; and sealing plates 15 on both end surfaces of the inner ring 11 and the outer ring 12 , The inner ring 11 is with a counterbore 11b formed, which is located at an axial end of its outer peripheral surface.

The sealing plates 15 are in Befestigungsnuten 16 fitted in an inner diameter surface of the outer ring 12 are provided.

An outer diameter surface 11a of the inner ring 11 that is an inner diameter portion of the seal plate 12 is facing, as in 1 shown, just trained and contrary to the one in 4 shown conventional bearing no sealing grooves, which has a labyrinth structure between the inner diameter portion of the sealing plate 15 and the outer diameter surface of the inner ring 11 form.

As indicated by an arrow A in 1 shown, the sealing plate extends 15 radially inwardly for a predetermined length to allow substantially direct flow of air from an input side to an output side without resistance, such that a gap exists between the outer diameter surface of the inner ring 11 on the exit side and the inside diameter portion of the seal plate 15 has a projection area that is substantially equal to a projection area of a flow path for air flowing through the bearing.

With respect to a flow passage resistance during the time when the air passes through, this radially inwardly directed length of the seal plate 15 be formed such that the projection surface is about 10% smaller than the projection area of the flow path of the air flowing through the bearing.

By the radially inwardly directed length of the sealing plate 15 is formed as described above, so that the gap between the inner diameter portion of the sealing plate 15 and the outer diameter surface of the inner ring 11 Opposite this, having a projection surface which allows air to flow substantially directly without resistance, enables the invention that the sealing plate 15 is less likely to be exposed to unnecessary force as the air passes through the bearing; that prevents the sealing plate 15 fluctuates and deforms; and that a stable seal is guaranteed. As far as this condition is satisfied, the gap between the inner diameter portion of the seal plate 15 and the opposite outer peripheral surface of the inner ring 11 however, it is desirably smaller than an inner diameter of the holder 14 should be to prevent leakage of lubricant from inside the bearing.

In order to allow a flow of air with a lower resistance, it is desirable that the outer diameter surface 11a of the inner ring 11 that is the inner diameter portion of the seal plate 15 is opposite, straight.

2 and 3 show enlarged partial views showing a state in which a holder 14 of the spindle ball bearing with built-in motor according to the present invention is performed. In 2 and 3 the lines, alternately one long and two short dashed lines, represent a pitch circle diameter ( PCD ) of the rolling element 13 while a reference numeral 14a a recess representing the rolling element 13 holds.

Preferably, the dimension d of an inner diameter portion becomes 14b of the owner 14 formed as large as possible to allow passage of the air with low resistance. However, enlargement of the inner diameter portion reduces 14b of the owner 14 the stiffness of the holder 14 , so preferably the Dimension d of the inner diameter section 14b of the owner 14 satisfies the following equation, where D is a dimension of the outer diameter section 14c of the owner 14 Q represents a load coming from the rolling element 13 is recorded, μ represents a coefficient of friction between the rolling element 13 and the races, σ is an acceptable tensile strength of a resin material of the holder 14 represents and B is an axial total thickness of the holder 14 represents.

$$\text{d}\leqq \text{D}-\left(4*\text{Q}*\mathrm{\mu }\right)/\left(\mathrm{\sigma }*\text{B}\right)$$

Further, preferably, the dimension d of the inner diameter portion 14b of the owner 14 larger than an inner diameter of the seal plate 15 so as not to hinder the flow of air. Even more preferred, as in 2 shown a peripheral contact surface 14d a recess 14a of the roller holder 14 at a radially outward point than the PCD of the rolling element 13 in contact with the rolling element 13 stand. This arrangement in which the peripheral contact surface 14d the recess 14a of the owner 14 at a radially outward point of the PCD of the rolling element 13 with the rolling element 13 is in contact, as shown by the thick arrows, that when the rolling element 13 moved in a circumferential direction, the holder 14 always under a radially outward force, creating a gap between the holder 14 and the outer peripheral surface 11a of the inner ring 11 forms and the air flow is not limited.

As in 3 shown, the holder can 14 be formed so that its inner diameter section 14b at a radially outward point than the PCD of the rolling element 13 lies, causing the holder 14 always under a radially outward force when the rolling element 13 performs a circumferential movement.

In other words, as in a conventional example in 5 shown is a holder 8th with a rolling element 10 on a circumferential contact surface 8b his recess 8a ie at one PCD of the rolling element 10 , in contact. According to the embodiment of the present invention, which in 2 however, the peripheral contact surface is shown 14d the recess 14a of the owner 14 at a radially outer side than the PCD the rolling element in contact.

In the in 1 The embodiment shown is a grease chamber 17 as a part of the outer ring 12 provided a stable lubricant supply between a race of the outer ring 12 and the rolling element 13 and between the race of the outer ring 12 and the holder 14 to ensure.

In cases where the angular contact ball bearings according to the present invention are arranged immediately after one another in two rows, the bearing has the grease chamber on each of its right and left sides 17 because the bearings point in two rows with respect to the air flow in mutually different directions.

The grease occupies up to 40 to 50% of a static range. If the amount is less than 40%, the fat distribution becomes uneven due to the air pressure, which makes the durability unstable. If the amount is more than 50%, the rotation becomes unstable as the grease distribution becomes uneven due to the air pressure, causing excessive local recirculation of grease and causing enormous temperature variations and vibration variations.

Two types of grease are used: a low viscosity grease G1 Primarily on the inner diameter side of the outer ring 12 applied while a high viscosity grease G2 is filled in an air-sensitive area having side surfaces of the holder on an inner ring side.

When the bearing is filled with grease, a grease having excellent high-speed performance, ie, a spindle grease having a base oil viscosity of 20 to 30 mm ² / S (40 ° C.) and a rolling penetration of 200 to 230, is first charged such that it primarily on the inner diameter side of the outer ring 12 liable.

Thereafter, an axial load is applied and a rotation performed, so that the filled grease G1 over the entire inner diameter surface of the outer ring 12 , the surfaces of the rolling element 13 and the owner 14 is distributed.

This process ensures that there is a sufficient amount of grease in the grease chamber 17 is present, the inner diameter of the outer ring 12 , the recess surfaces of the holder 14 and the guide surfaces, with the outer ring 12 be shared, is provided.

Next, assuming that a maximum air flow of 10 to 30 Nl / min may be present, the grease G2 that has a higher viscosity than the previously filled grease G1 ie, a grease having a base oil viscosity of 30 to 40 mm ² / S (40 ° C) and a Wälzpenetration 240 to 260, from the side of the holder 14 so injected that the grease adheres to the inner diameter side.

In this process, assuming that there may be cases in which the angular contact ball bearing is arranged directly behind one another in two rows, the bearings in two rows with respect to the air flow in mutually different directions, each right and left side of the bearing filled with grease.

The two types of greases G1 and G2 can partially mix with each other. As a precautionary measure, therefore, specifications other than the base oil viscosity and the roller penetration, ie, the base oil type and the thickener type, are standardized.

In the present invention, first, the bearing is filled with low-viscosity grease, an intake operation is performed, and then a high-viscosity grease is filled in the left and right sides. If a large amount of grease is suddenly applied to one of the sides, a quantity of grease is moved at the time of running in and discharged from a sealing lip on the filled side. However, the discharge amount of the sealing lip 15 at the time of the run-in operation, when the run-in operation is performed with the grease applied first, and then the grease is applied to the respective areas on both sides.

Overall, the grease occupies 50 to 70% of a static range.

If the value is higher than 70%, a longer time is required for a running-in operation after a main shaft assembly. Another possible consequence is an unstable rotation, which is produced by a local or excessive recirculation of the grease, which leads to excessive temperature fluctuations and vibration fluctuations.

The grease G1 or the grease to be filled first should be about 50% of the total amount of grease to be filled. The remaining 50% or the high viscosity grease G2 should be split between the two sides of the camp, ie 25% on one side and the same amount on the other side.

For example, the thickener for the grease may be selected from urea thickeners, barium complex soap thickeners, and lithium soap based thickeners. The base oil can be selected from ester oils and synthetic oils.

LIST OF REFERENCE NUMBERS

11:

inner ring

11a:

Outer diameter surface

12:

outer ring

13:

rolling element

14:

holder

14a:

recess

14b:

Inner diameter section

14c:

Outside diameter portion

14d:

Peripheral contact surface

15:

sealing plate

16:

mounting groove

17:

Grease chamber

G1:

low viscosity grease

G2:

high viscosity grease

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• JP 3150371 U [0013]
• JP 2016023719A [0013]

Claims (6)

Spindle ball bearing with built-in motor, comprising: an inner ring; an outer ring; Rolling elements disposed between opposing rolling surfaces of the inner ring and the outer ring; a holder holding the rolling elements; and a seal plate extending from an inner diameter surface at each end of the outer ring toward the inner ring; and wherein the sealing plate has a radially inwardly-directed length with a dimension such that a flow of air substantially directly without resistance from an input side to an output side through the bearing is possible; wherein the outer ring and the inner ring have a portion holding two kinds of grease therebetween, one formed of a low viscosity grease located mainly on an inner diameter side of the outer ring and the other formed of a high viscosity grease is located in an air-sensitive area, which includes side surfaces of the holder on an inner ring side. Spindle ball bearing with built-in motor Claim 1 wherein the low viscosity grease, which is mainly on the inner diameter side of the outer ring, has a base oil viscosity in a range of 20 to 30 mm ² / S (40 ° C) and a worked penetration in a range of 200 to 230, while the high viscosity grease which is in the air-sensitive region comprising the side surfaces of the inner-ring-side holder, has a base oil viscosity in a range of 30 to 40 mm ² / S (40 ° C), and a wettability in the range of 240 to 260. Spindle ball bearing with built-in motor Claim 1 or 2 wherein the inner ring has a counterbore on one side, the outer ring has a grease chamber on one or two sides of its inner diameter surface, and the low viscosity grease is in the grease chamber. Spindle ball bearing with built-in motor according to one of the Claims 1 to 3 wherein the inner ring has a straight outer diameter surface facing an inner diameter portion of the seal plate. Spindle ball bearing with built-in motor according to one of the Claims 1 to 4 wherein the holder has recesses which are respectively in contact with the rolling element at its peripheral contact surface, which lies radially further outward than a PCD of the rolling element. Spindle ball bearing with built-in motor according to one of the Claims 1 to 4 wherein the holder has an inner diameter portion disposed at a radially outer position than a PCD of the rolling element.

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