WO2010027402A2

WO2010027402A2 - Cooling arrangement for machine spindle

Info

Publication number: WO2010027402A2
Application number: PCT/US2009/004669
Authority: WO
Inventors: James J. Gnadt; Kenneth E. Glasow
Original assignee: The Gleason Works
Priority date: 2008-08-25
Filing date: 2009-08-14
Publication date: 2010-03-11
Also published as: WO2010027402A3

Abstract

Electrical apparatus, such as a direct drive motor or spindle, comprising a stator (8) rotor (6) and at least one bearing (18,20) having an arrangement for cooling wherein a cooling medium is introduced between the rotor and at leas one bearing.

Description

COOLING ARRANGEMENT FOR MACHINE SPINDLE

Field of the Invention

[0001] The present invention is directed to electrical apparatus, particularly direct drive motors and spindles in machine tools, and a means to cool internal components thereof.

Background of the Invention

[0002] There are many types of mechanisms for producing motion, particularly rotational motion, or electrical current that comprise a stator, rotor and bearings. For example, spindles comprising motors integral with a spindle shaft (i.e. direct drive spindles) are known for rotating tools and/or work pieces in machine tools. Electrical current is introduced into the stator windings and magnetic fields produced by the windings interact with magnetic fields of the rotor causing the rotor, and hence the spindle shaft to which the rotor is attached, to rotate. Heat is produced as a byproduct of the magnetic field interaction. As spindle speeds increase, so does the production of generated heat.

[0003] In vehicles, for example, alternators operate in a generally opposite manner to that above. Rotational motion imparted mechanically to a shaft with an attached rotor causes magnetic fields of the rotor to interact with magnetic fields of the stator thereby producing an electrical current.

[0004] In either type of arrangement, however, considerable heat is generated during operation and one or more bearings, which are utilized on the rotating spindle or shaft, are exposed to at least a portion of such heat. Excessive heat can damage or destroy a bearing in that, for example, the effectiveness of lubricating material may be diminished or the bearing pre-load may be weakened or destroyed. In any case, bearing damage can negatively affect the quality of machined work pieces or may lead to spindle, motor or other machine component damage or destruction.

[0005] It is known to pass coolant, such as air or an inert gas, over or through bearings for cooling. However, this can create significant temperature variations within the bearings, or between the bearings and the spindle shaft, potentially leading to warping of bearing elements and subsequent failure. Furthermore, while passing coolant over or through bearings may remove heat from the bearings, it fails to remove heat migrating along the spindle shaft. Additionally, coolant passing through bearings may introduce contaminants, entrained in the coolant flow, into the inner workings of the bearings, or if the bearings are grease-packed, coolant flow through the bearings may have a drying effect on the grease.

Summary of the Invention

[0006] The present invention is directed to an arrangement for cooling a mechanism comprising a stator, rotor and at least one bearing wherein a cooling means is introduced between the rotor and at least one bearing.

Brief Description of the Drawings

[0007] Figure 1 is a cross-sectional view of a direct drive spindle comprising the cooling arrangement of the present invention.

[0008] Figure 2 illustrates the spindle of Figure 1 wherein the path of coolant flow is shown. [0009] Figure 3 is a cross-sectional view of the coolant distribution collar of the present invention.

[0010] Figure 4 is an end view of the coolant distribution collar.

[0011] Figure 5 is a view of the discharge portion of the coolant distribution collar.

Detailed Description of the Invention

[0012] The invention will now be discussed with reference to preferred embodiments as illustrated by the accompanying drawings which are intended to be non-limiting and to represent the invention by way of example only. In the present invention, cooling or coolant "fluid" is intended to include appropriate substances in the liquid or gaseous states.

[0013] Figure 1 illustrates a direct drive spindle 2 comprising a spindle shaft 4, usually made of steel, rotatable about axis A, with attached rotor 6. The spindle shaft terminates (to the left in Figure 1 ) in a spindle face (not shown) where appropriate work piece or tool holding equipment (not shown) is attached. Such spindle face and work or tool holding equipment form no part of the present invention and therefore, no additional explanation is necessary. Located adjacent to and encircling the rotor 6 is a stator 8 attached to spindle housing 10. Heat exchange fins 12 project from housing 10 and are attached to an outer jacket 14 thereby forming channels 16 which encircle the spindle and through which a cooling fluid (e.g. chilled water) is circulated for cooling the spindle, particularly the stator 8.

[0014] Spindle 2 also comprises bearings, namely a forward pair of bearings 18 and rear pair of bearings 20. While pairs of bearings are shown, it should be understood that in some applications, a single forward and/or rear bearing may be present or more than two forward and/or rear bearings may be present. Alternatively, rear bearings may not be utilized in a particular application. [0015] When the spindle 2 is in operation, heat that is generated, particularly in the stator 8, is partially removed via coolant flow in channels 16 as described above. However, there is also a tendency for remaining heat to migrate into the spindle shaft 4 and then to the bearings 18 and 20. Should the bearings become too hot, lubricants or pre-load conditions may diminish or fail as previously mentioned. Excessive heat in the spindle shaft 4 may cause unwanted expansion thereof which can undesirably affect the position of a tool or work piece attached to the end of the spindle shaft. Heat related effects are most noted and particularly undesirable in the portion of the spindle forward of the rotor where spindle shaft growth and/or bearing damage has a more pronounced effect on work piece quality and/or machine performance.

[0016] The inventors have discovered that a heat removing means, such as a heat sink 22 and/or 24 positioned on and around the spindle shaft 4 at a location between the rotor 6 and the respective bearings 18, 20 removes heat from the spindle shaft ahead of the respective bearings. Preferably, heat sinks 22, 24 are made of aluminum, however, any material suitable for use as a heat sink for removing heat from the material of the spindle shaft (e.g. steel) is contemplated. A cooling medium, such as compressed air, is introduced into spindle 2 (at a forward location) via an inlet 26 to a distribution collar 28 (see Figure 3) positioned closely around the heat sink 22 wherein the coolant is directed into a distribution manifold 29 and then into the gaps 30 between the fins 32 of the heat sink via respective openings (i.e. inlet ports) 34 in the distribution manifold 29. The coolant flows around the heat sink exiting at one or more ports 36 (preferably three exit ports 36, 38 and 40 as shown in Figures 4 and 5) with each of the exit ports having respective openings 42 to permit coolant flowing between the heat sink fins 32 to escape from the distribution collar 28.

[0017] After the coolant has left the distribution collar 28, it is directed toward the rear portion of the spindle 2. The coolant may be directed through the spindle housing 10 in an area between the stator 8 and the heat exchange fins 12 as seen D

in Figure 1. In this manner, the coolant may assist coolant channels 16 in cooling the stator 8. Alternatively, the coolant may be directed via one or more tubes along the outside of the outer jacket 14 and then re-enter the spindle 2. With this arrangement, the temperature of the coolant is decreased due to presence of the cooled outer jacket 14. In either arrangement, once the coolant has passed along the length of the stator 8, it is directed through the rear portion of the spindle 2 and around and past the rear hear sink 24 (if present) and then to a discharge outlet 44. Figure 2 shows the preferred path of coolant through the spindle 2.

[0018] Of course, if rear bearings are not present, it may be desirable to omit the rear heat sink 24 altogether. In this case, once the coolant exits the distribution collar 28, it can be immediately discharged from the spindle 2 such as, for example, in the area designated by 46 in Figure 2. Alternatively, coolant exiting from the distribution collar 28 may still be routed along the stator 8, either within the housing 10 or along the outer jacket 14 as discussed above, and then discharged from the spindle 2 such as, for example, in the area designated by 48 in Figure 2.

[0019] It is to be understood that although it is preferred to utilize the inventive heat removal means with respect to a forward heat sink and bearings, the invention is not limited thereto. If desired, a distribution collar as shown in Figures 1-5 may be utilized for a rear heat sink only. In this embodiment, the coolant inlet and discharge outlet would preferably be positioned proximate the rear portion of the spindle 2. Also, separate distribution collars for each of forward and rear heat sinks are also contemplated. In this embodiment, a second coolant inlet and a second discharge outlet would preferably be utilized. Thus, a spindle so equipped would have two coolant inlets and two discharge outlets.

[0020] Although compressed air (e.g. "shop air") is a preferred coolant, other types of coolant fluids may also be utilized, such as inert gases. The coolant employed may be filtered and/or chilled prior to entering a spindle. Alternatively, discharged coolant may be captured and re-circulated (i.e. a "closed" coolant system). A venturi style nozzle may be utilized for coolant entering the distribution manifold 29 from the inlet 26 (Figure 3). The rapid volume expansion produced by the venturi would bring about a drop in temperature of the coolant thus further reducing its temperature prior to entering the gaps 30 of the heat sink 22.

[0021] Although the present invention has been discussed with reference to machine tool spindles, particularly direct drive spindles, the invention is not to be limited thereto. As mentioned above, the inventive elements are applicable to any arrangement wherein a rotor, stator, shaft and bearings are utilized and heat is generated thereby. Some other non-limiting examples are alternators for passenger, commercial and industrial vehicles and equipment, household and industrial electric generators, and power tools.

[0022] While the invention has been described with reference to preferred embodiments it is to be understood that the invention is not limited to the particulars thereof. The present invention is intended to include modifications which would be apparent to those skilled in the art to which the subject matter.

Claims

CLAIMSWhat is claimed is:

1. An electrical apparatus comprising: a rotatable shaft; a rotor attached to said shaft and a stator located adjacent to said rotor; at least one of bearings located forward of said rotor and bearings located rearward of said rotor; heat removing means located on said shaft and positioned between said rotor and said at least one of the forward bearings and the rearward bearings thereby defining at least one of a forward heat removing means and a rearward heat removing means; at least one coolant inlet and at least one coolant discharge outlet; a coolant flow path defined between said at least one coolant inlet and at least one coolant discharge outlet for the passage of coolant through said apparatus, with at least a portion of said coolant flow path directing coolant to contact said at least one of the forward heat removing means and the rearward heat removing means.

2. The apparatus of claim 1 wherein said heat removing means comprises a heat sink.

3. The apparatus of claim 2 wherein said heat sink comprises a plurality of fins defining gaps therebetween.

4. The apparatus of claim 3 said at least a portion of said coolant flow path comprises flow through said gaps.

5. The apparatus of claim 1 further comprising a distribution collar positioned around at least said forward heat removing means, said distribution collar including inlet ports and exit ports for introducing and exhausting coolant flowing along said at least a portion of said coolant path.

6. The apparatus of claim 5 wherein said inlet ports are located in a distribution manifold.

7. The apparatus of claim 6 wherein said distribution manifold includes a venturi nozzle through which coolant is introduced into said distribution manifold.

8. The apparatus of claim 6 wherein said distribution collar is positioned around at least said forward heat removing means comprising a heat sink having a plurality of fins defining a plurality of gaps therebetween, said distribution collar communicating with said gaps whereby coolant is introduced into said gaps via said inlet ports and coolant is discharged from said gaps via said exit ports.

9. The apparatus of claim 5 wherein said discharge outlet is positioned proximate to said exit ports.

10. The apparatus of claim 5 wherein said coolant flow path further extends along said stator prior to reaching said discharge outlet.

11. The apparatus of claim 10 wherein said coolant flow path further extends across said rearward heat removing means prior to reaching said discharge outlet.

12. A method of cooling an electrical apparatus comprising a rotatable shaft, a rotor attached to said shaft and a stator located adjacent to said rotor, at least one of bearings located forward of said rotor and bearings located rearward of said rotor, said method comprising: providing heat removing means located on said shaft and positioned between said rotor and said at least one of the forward bearings and the rearward bearings thereby defining at least one of a forward heat removing means and a rearward heat removing means, introducing coolant into at least one coolant inlet, passing said coolant along a coolant flow path defined between said at least one coolant inlet and at least one coolant discharge outlet, at least a portion of said coolant flow path directing coolant to contact said at least one of the forward heat removing means and the rearward heat removing means, discharging coolant from said coolant discharge outlet.

13. The method of claim 12 wherein the flow path directs coolant to flow in contact with the forward heat removing means and along said stator.

14. The method of claim 13 wherein flow path directs coolant to flow in contact with the rearward heat removing means.

15. The method of claim 12 wherein said coolant comprises air.