Main spindle device of motor built-in type

Abstract

To provide a main spindle device of a motor built-in type in which prolongation of life of grease lubrication is achieved by suppressing exposure of grease filled in a bearing to high-temperature air.SOLUTION: A main spindle device 10 of a motor built-in type includes: a rotation shaft 11; a front bearing 50 and a rear bearing 60 rotatably supporting the rotation shaft 11; and a motor 30 rotating the rotation shaft 11. The front bearing 50 and the rear bearing 60 are lubricated by grease. In the periphery of a fitting portion in which the front bearing 50 or the rear bearing 60 fit to each other, a cooling groove 41 is formed. The main spindle device 10 of the motor built-in type includes a heat pipe 25 having a projection part 25a at least partially projecting to an internal space (motor chamber) 34 of the main spindle device 10, and arranged substantially in parallel to an axial core of the rotation shaft 11.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a spindle unit with a built-in motor, and more particularly to a spindle unit with a built-in motor used in machine tools, high-speed motors, or rotating machines that rotate at high speeds, such as centrifuges and turbo refrigerators. [Background technology]

[0002] Oil lubrication is the mainstream for machine tool spindles, high-speed motors, and rotating machinery that rotates at high speeds, such as centrifuges and turbo refrigerators. However, it has various issues, such as the need to be environmentally conscious due to noise and oil splashing, the need for large amounts of air, and the need for auxiliary equipment such as oil-air supply systems. For this reason, in recent years, there has been a trend toward grease lubrication in efforts to save energy and resources. With grease lubrication, lubrication is performed using the base oil of the grease sealed into the bearing when it is installed, but there is a limit to the amount of base oil required for bearing lubrication, and the amount of base oil affects the lubrication life.

[0003] Furthermore, if too much grease is packed into the bearing, the viscous resistance increases, which can lead to increased bearing heat generation when used at high speeds, causing the grease to deteriorate prematurely and leading to oil film breakdown and seizure. Therefore, to strike a balance between the temperature rise characteristics and grease life at high speeds, the amount of grease is typically limited to 10% to 30% of the bearing space volume. Even when the rotation speed is not high, packing in too much grease can lengthen the break-in time, which can slow down the return to the production line after a spindle replacement, affecting production efficiency.

[0004] Furthermore, grease is affected by temperature, and temperature, i.e., heat, can cause oxidation of the thickener and base oil. This oxidation can destroy the network structure of the thickener, leading to grease leakage and evaporation and decomposition of the base oil, which can shorten the life of the grease.

[0005] In particular, in the case of spindle units with built-in motors, the thermal impact of the motor has a significant impact on grease life. Also, since grease adheres to the outer ring after break-in, in order to mitigate the thermal impact of grease adhering to the outer ring, cooling grooves are provided in the housing into which the outer ring fits, and oil or water at a temperature of approximately ±0°C to +2°C above room temperature is poured into the cooling grooves to cool the outer ring, lowering the grease temperature and extending the grease life.

[0006] The spindle device of the machine tool described in Patent Document 1 is equipped with a heat pipe that is built into the spindle and transfers heat from the center of the spindle to the rear end, a plurality of plate-shaped inner fins that are fixed to the rear part of the spindle behind the rear bearing and extend in a direction perpendicular to the rotation axis of the spindle, and a plurality of plate-shaped outer fins that are fixed to the housing and arranged between the plurality of inner fins, making it possible to efficiently discharge heat from the spindle to the outside. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2019-162707 Summary of the Invention [Problem to be solved by the invention]

[0008] However, although the cooling grooves provided in the housing can cool the outer ring, they cannot cool the high-temperature air around the bearing, and there is a risk that the grease will be exposed to hot air, resulting in a shortened lifespan. Furthermore, the higher the rotation speed, the smaller the spindle device becomes, so the internal space of the spindle device becomes narrower, and hotter air remains inside, resulting in a greater impact on the grease. The spindle device described in Patent Document 1 is designed to cool the spindle, but does not solve the above problem.

[0009] The present invention has been made in view of the above-mentioned problems, and its object is to provide a spindle device with a built-in motor that prevents the grease sealed in the bearings from being exposed to high-temperature air, thereby extending the lubrication life of the grease. [Means for solving the problem]

[0010] Therefore, the above object of the present invention is achieved by the following configuration [1] relating to a spindle device of a motor built-in type. [1] A rotation axis; a front bearing and a rear bearing that respectively support the rotary shaft rotatably relative to a housing; a motor including a rotor disposed between the front bearing and the rear bearing so as to be rotatable integrally with the rotary shaft, and a stator disposed around the rotor; a motor-built-in type spindle device in which the front bearing and the rear bearing are lubricated by enclosed grease, a cooling groove is formed around a fitting portion of the housing where the front bearing or the rear bearing is fitted, a heat pipe having at least a portion thereof projecting into an internal space of the motor-built-in type spindle device, and disposed between the fitting portion and the cooling groove in the housing and substantially parallel to the axis of the rotating shaft; Spindle unit with built-in motor. [Effects of the Invention]

[0011] According to the motor-built-in type spindle device of the present invention, by providing a heat pipe that directly removes heat from the high-temperature air, it is possible to prevent the grease sealed in the bearings from being exposed to high-temperature air, thereby extending the grease lubrication life. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view of a spindle device with a built-in motor according to a first embodiment of the present invention. [Figure 2]FIG. 2 is a side view of an example of the arrangement of heat pipes. [Figure 3] FIG. 3 is a perspective view of an example of the arrangement of the heat pipes shown in FIG. [Figure 4] FIG. 4 is a side view of another example of the arrangement of heat pipes. [Figure 5] FIG. 5 is a perspective view of an example of the arrangement of the heat pipes shown in FIG. [Figure 6] FIG. 6 is a cross-sectional view of a spindle device with a built-in motor according to a second embodiment of the present invention. [Figure 7] FIG. 7 is a cross-sectional view of a spindle device with a built-in motor according to a third embodiment of the present invention. [Figure 8] FIG. 8 is a cross-sectional view of a motor built-in type spindle device according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, a motor built-in type spindle device according to each embodiment of the present invention will be described in detail with reference to the drawings.

[0014] (First embodiment) Fig. 1 is a cross-sectional view of a motor built-in type spindle device according to a first embodiment of the present invention. In the cross-sectional views of Fig. 1 and Fig. 6 to Fig. 8, only heat pipe 25, which is a feature of the present invention, is shown by diagonal lines.

[0015] As shown in Fig. 1, in a motor-built-in type spindle unit 10 for a machine tool spindle (hereinafter also simply referred to as "spindle unit 10"), a rotating shaft 11 is rotatably supported in a housing H by two rows of front bearings 50, 50 arranged on the tool side (left side in Fig. 1) and two rows of rear bearings 60, 60 arranged on the side opposite to the tool (right side in Fig. 1). The housing H is mainly composed of, in order from the tool side, a front housing 12, an outer cylinder 13, a rear housing 14, and a rear cover 15, which are all fastened and fixed together by bolts (not shown).

[0016] Each front bearing 50 is an angular contact ball bearing having an outer ring 51, an inner ring 52, balls 53 as rolling elements arranged at a contact angle, and a cage (not shown). Each rear bearing 60 is also an angular contact ball bearing having an outer ring 61, an inner ring 62, balls 63 as rolling elements arranged at a contact angle, and a cage (not shown). The front bearings 50, 50 (parallel combination) and the rear bearings 60, 60 (parallel combination) are arranged so as to cooperate with each other to form a back-to-back combination.

[0017] The outer rings 51, 51 of the front bearings 50, 50 are fitted into the front housing 12 and are axially positioned and fixed relative to the front housing 12 via an outer ring spacer 54 by a front outer ring holder 16 which is threadedly fixed to a female thread 12a formed in the front housing 12.

[0018] The front housing 12 has an annular recess 12b on its outer peripheral surface and is fitted into the outer cylinder 13, and a substantially annular cooling groove 41 is provided between the inner peripheral surface of the outer cylinder 13 and the outer peripheral surface of the front housing 12. A cooling medium (oil, water, etc. at room temperature ±0°C to +2°C) is supplied to the cooling groove 41.

[0019] In addition, the inner rings 52, 52 of the front bearings 50, 50 are fitted onto the rotating shaft 11, and are axially positioned and fixed to the rotating shaft 11 by a nut 17 fastened to the rotating shaft 11 via a flinger 40 fitted onto the front end side of the rotating shaft 11 and an inner ring spacer 55.

[0020] The outer rings 61, 61 of the rear bearings 60, 60 are fitted into a sleeve 18 which is fitted into the rear housing 14 so as to be freely slidable in the axial direction, and are positioned and fixed in the axial direction relative to the sleeve 18 via an outer ring spacer 64 by a rear outer ring holder 19 which is fixed integrally to the sleeve 18 with a bolt (not shown).

[0021] The sleeve 18 has an annular recess 18a on its outer circumferential surface and is fitted into the rear housing 14, and a substantially annular cooling groove 41 is provided between the inner circumferential surface of the rear housing 14 and the outer circumferential surface of the sleeve 18. A cooling medium (oil, water, etc. at room temperature ±0°C to +2°C) is supplied to the cooling groove 41.

[0022] The inner rings 62 of the rear bearings 60 are fitted onto the rotary shaft 11, and are axially positioned and fixed to the rotary shaft 11 via inner ring spacers 65 by another nut 21 fastened to the rotary shaft 11. A coil spring 23 is disposed between the rear housing 14 and the rear outer ring retainer 19, and the spring force of this coil spring 23 presses the rear outer ring retainer 19 rearward together with the sleeve 18. This applies a preload to the front bearings 50 and the rear bearings 60.

[0023] The tool side of the rotating shaft 11 is provided with a tool mounting hole and internal thread (not shown) that pass through the center of the shaft and are formed in the axial direction. The tool mounting hole and internal thread are used to mount a tool (not shown) such as a cutting tool to the rotating shaft 11. Instead of the tool mounting hole and internal thread, a conventionally known draw bar (not shown) may be slidably inserted into the axial core of the rotating shaft 11. Each draw bar has a collet portion that secures a tool holder (not shown), and is biased in the direction away from the tool by the force of a disc spring.

[0024] A motor 30 is disposed approximately in the axial center between the front bearings 50, 50 and the rear bearings 60, 60 of the rotating shaft 11. The motor 30 includes a rotor 31 arranged to be rotatable integrally with the rotating shaft 11, and a stator 32 arranged around the rotor 31. The stator 32 is fixed to the outer cylinder 13 by fitting a cooling jacket 33 shrink-fitted to the stator 32 into the outer cylinder 13 that constitutes the housing H.

[0025] An electric wire 35, which is connected to the coil of the stator 32 and supplies power to the stator 32, is inserted through wiring holes 36a, 36b provided in the rear housing 14 and the rear cover 15 and connected to an external power source. The motor 30 supplies power to the stator 32 via the electric wire 35, thereby generating a rotational force in the rotor 31 and rotating the rotary shaft 11. The motor 30 is housed in a motor chamber 34, which is a space surrounded by the front housing 12, the outer cylinder 13, the rear housing 14, and the sleeve 18 around the rotary shaft 11.

[0026] The rear cover 15 has an opening cover 28 that covers the opening 15a formed at the rear end, and a rear space 45 formed mainly by the rear housing 14, the rear cover 15, and the sleeve 18 is provided behind the rotating shaft 11.

[0027] Next, the main configuration of the present invention will be described with reference to Figures 2 and 3. At least one heat pipe 25 (eight in this embodiment) is embedded in the front housing 12 in the radial direction, approximately parallel to the axis of the rotating shaft 11, between the portion where the outer ring 51 fits and the cooling groove 41. The heat pipe 25 is formed in a straight rod shape, and its protruding portion 25a on the motor side protrudes linearly into the motor chamber 34.

[0028] Furthermore, at least one heat pipe 25 is embedded in the sleeve 18 in the radial direction, between the portion where the outer ring 61 fits and the cooling groove 41, and approximately parallel to the axis of the rotating shaft 11. The heat pipe 25 is formed in the shape of a straight rod, and its protruding portion 25a on the motor side protrudes linearly into the motor chamber 34.

[0029] The heat pipe 25 has a hollow body made of copper or aluminum, which has good thermal conductivity, and a highly volatile liquid (working fluid) sealed inside the pipe.The working fluid vapor is evaporated in the high-temperature section, cooled in the low-temperature section to return it to liquid, and the liquid is then evaporated again in the high-temperature section, and this cycle is repeated.By circulating the working fluid within the heat pipe, heat is transferred from the high-temperature section to the low-temperature section.

[0030] In this embodiment, as shown in FIGS. 2 and 3, eight heat pipes 25 are arranged at equal intervals on a circumference, and protrusions 25a at one end of each heat pipe 25 extend linearly into the space.

[0031] 4 and 5, four heat pipes 25 may be used, the protruding portions 25a may be formed in a substantially U-shape, and both ends of the heat pipes 25 may be embedded in the front housing 12 or the sleeve 18. This is effective when there is a limit to the space available for installing the heat pipes, and also allows the protruding portions 25a to be positioned more reliably.

[0032] In such a spindle unit 10, heat energy is generated in the motor 30 due to various losses that occur when the motor is driven. Furthermore, as the rotating shaft 11 rotates at high speed, the temperatures of the front bearing 50 and the rear bearing 60 also rise. This heat energy heats the air inside the housing H, particularly the air in the motor chamber 34 in which the motor 30 is housed, and the air becomes high temperature.

[0033] If this high-temperature air flows toward the front bearing 50 and rear bearing 60, it may affect the grease that lubricates the front bearing 50 and rear bearing 60, thereby reducing the lubrication life of the grease.

[0034] On the other hand, in the spindle device 10 of this embodiment, the heat transferred to the air from the coil 32a of the stator 32 and the rotating shaft 11 is efficiently removed by the protruding portion 25a of the heat pipe 25 protruding into the motor chamber 34, and is cooled via the front housing 12 and the sleeve 18, which are cooled by the cooling medium passing through the cooling groove 41, thereby mitigating the thermal effect that high-temperature air has on the grease and extending the life of the grease.

[0035] (Second embodiment) 6, in the motor-built-in type spindle unit 10 of this embodiment, the shape of the heat pipe 25 is different from that of the heat pipe 25 of the first embodiment. Specifically, a protruding portion 25a of the heat pipe 25, which is embedded in the front housing 12 and the sleeve 18 and protrudes into the motor chamber 34, is bent radially inward (toward the rotating shaft 11) by approximately 30° and fits into the radially inner side of the coil 32a of the stator 32, thereby reliably preventing interference with the coil 32a.

[0036] According to the motor built-in type spindle device 10 of this embodiment, the protrusion 25a of the heat pipe 25 can be arranged closer to the coil 32a of the stator 32, which is the heat source, and heat can be removed efficiently.

[0037] (Third embodiment) 7, the motor built-in type spindle unit 10 of this embodiment is arranged in a vertical position with the rear bearing 60 located at the top. In the vertical position, high-temperature air in the motor chamber 34 and the like moves upward, and may accumulate in the rear space 45 behind the rotating shaft 11, causing the air in the rear space 45 to become hot.

[0038] Therefore, in the spindle unit 10 of the present embodiment, in addition to the heat pipe 25 embedded in the front housing 12 and the sleeve 18, another heat pipe 25 is embedded radially in the rear cover 15, and its protruding portion 25a protrudes into the rear space 45. This makes it possible to cool the air temperature in the rear space 45, which tends to become high in a vertical position, and to mitigate the thermal effect on the grease that lubricates the rear bearing 60 in particular.

[0039] (Fourth embodiment) As shown in FIG. 8, in the motor built-in type spindle device 10 of this embodiment, the high-temperature air in the internal space 57 in which the pair of front bearings 50, 50 are arranged and the internal space 67 in which the pair of rear bearings 60, 60 are arranged is directly cooled by the heat pipe 25.

[0040] Specifically, the front housing 12 is composed of a front housing main body 71 into which the outer ring 51 of the front bearing 50 is fitted, and a cooling jacket 72 which has an annular recess 12b on its outer peripheral surface and which is fitted externally to the front housing main body 71 and is fitted internally to the outer cylinder 13.

[0041] The front housing main body 71 has an axial groove 73 formed on its outer peripheral surface that can accommodate the heat pipe 25, and further has a hole 74 that radially communicates between the axial groove 73 and an internal space 57 in which the pair of front bearings 50, 50 are disposed. Note that the outer ring spacer 54 also has a hole that is continuous with the hole 74 and communicates with the internal space 57.

[0042] The cooling jacket 72 is fitted into the outer cylinder 13 to form a substantially annular cooling groove 41 between the inner peripheral surface of the outer cylinder 13 and the outer peripheral surface of the cooling jacket 72 .

[0043] The heat pipe 25 is housed in the axial groove 73, and its protruding portion 25a is bent at a substantially right angle and disposed so as to protrude into the internal space 57 in which the pair of front bearings 50, 50 are disposed.

[0044] The sleeve 18 is also composed of a sleeve body 75 into which the outer ring 61 of the rear bearing 60 is fitted, and a cooling jacket 76 which has an annular recess 18a on its outer peripheral surface and which is fitted onto the sleeve body 75 and also fitted into the rear housing 14.

[0045] The sleeve body 75 has an axial groove 77 formed on its outer peripheral surface that can accommodate the heat pipe 25, and further has a hole 78 that radially communicates between the axial groove 77 and an internal space 67 in which the pair of rear bearings 60, 60 are disposed. Note that the outer ring spacer 64 also has a hole that is continuous with the hole 78 and communicates with the internal space 67.

[0046] The cooling jacket 76 is fitted into the rear housing 14 , thereby forming a substantially annular cooling groove 41 between the inner circumferential surface of the rear housing 14 and the outer circumferential surface of the cooling jacket 76 .

[0047] The heat pipe 25 is housed in the axial groove 77, and its protruding portion 25a is bent at a substantially right angle and disposed so as to protrude into the internal space 67 in which the pair of rear bearings 60, 60 are disposed.

[0048] In the motor built-in type spindle unit 10 of this embodiment, the high-temperature air in the internal space 57 in which the pair of front bearings 50, 50 are arranged and the internal space 67 in which the pair of rear bearings 60, 60 are arranged is directly cooled by the heat pipe 25, so that the effect of heat on the grease that lubricates the front bearings 50 and the rear bearings 60 can be efficiently suppressed and the life of the grease can be extended.

[0049] The present invention is not limited to the above-described embodiments, and modifications and improvements are possible as appropriate.

[0050] As described above, the present specification discloses the following: (1) a rotation axis; a front bearing and a rear bearing that respectively support the rotary shaft rotatably relative to a housing; a motor including a rotor disposed between the front bearing and the rear bearing so as to be rotatable integrally with the rotary shaft, and a stator disposed around the rotor; a motor-built-in type spindle device in which the front bearing and the rear bearing are lubricated by enclosed grease, a cooling groove is formed around a fitting portion of the housing where the front bearing or the rear bearing is fitted, a heat pipe having at least a portion thereof projecting into an internal space of the motor-built-in type spindle device, and disposed between the fitting portion and the cooling groove in the housing and substantially parallel to the axis of the rotating shaft; Spindle unit with built-in motor. According to this configuration, by providing a heat pipe that directly removes heat from the high-temperature air, the air temperature around the grease can be lowered, thereby extending the lubrication life of the grease, which is susceptible to thermal effects.

[0051] (2) The protruding portion of the heat pipe is formed in a straight line. A spindle device with a built-in motor as described in (1). This configuration makes it easier to fabricate the heat pipe.

[0052] (3) The protruding portion of the heat pipe has a bent portion. A spindle device with a built-in motor as described in (1). According to this configuration, the heat pipe can be arranged so as to avoid interference between the protrusion and the components of the spindle device.

[0053] (4) The bent portion is bent toward the inner diameter side of the stator. (3) A spindle device with a built-in motor. According to this configuration, the bent portion can prevent interference between the protrusion and the stator.

[0054] (5) The bent portion is formed in a U-shape. (3) A spindle device with a built-in motor. This configuration allows the length of the heat pipe to be used effectively.

[0055] (6) The rotating shaft is a machine tool spindle. The motor built-in type spindle device according to any one of (1) to (5). According to this configuration, the heat pipe can be provided in the spindle device of the machine tool.

[0056] (7) The rotating shaft is a main shaft for a high-speed motor. The motor built-in type spindle device according to any one of (1) to (5). According to this configuration, a heat pipe can be provided in the spindle device for a high-speed motor. [Explanation of symbols]

[0057] 10. Motor built-in spindle unit 11 Rotation axis 12 Front housing (housing) 13 Outer cylinder (housing) 14 Rear housing (housing) 15 Rear cover (housing) 25 heat pipe 25a Protrusion 30 motor 31 Rotor 32 Stator 34 Motor room (internal space of spindle device) 41 Cooling groove 45 Rear space (internal space of spindle device) 50 Front bearing 60 Rear bearing H Housing

Claims

1. A rotation axis; a front bearing and a rear bearing that respectively support the rotary shaft rotatably relative to a housing; a motor including a rotor disposed between the front bearing and the rear bearing so as to be rotatable integrally with the rotary shaft, and a stator disposed around the rotor; a motor-built-in type spindle device in which the front bearing and the rear bearing are lubricated by enclosed grease, a cooling groove is formed around a fitting portion of the housing where the front bearing or the rear bearing is fitted, a heat pipe having at least a portion thereof projecting into an internal space of the motor-built-in type spindle device, and disposed between the fitting portion and the cooling groove in the housing and substantially parallel to the axis of the rotating shaft; Spindle unit with built-in motor.

2. The protruding portion of the heat pipe is formed in a straight line.

2. The motor built-in type spindle device according to claim 1.

3. The protruding portion of the heat pipe has a bent portion.

2. The motor built-in type spindle device according to claim 1.

4. The bent portion is bent toward the inner diameter side of the stator.

4. The motor built-in type spindle device according to claim 3.

5. The bent portion is formed in a U-shape.

4. The motor built-in type spindle device according to claim 3.

6. The rotating shaft is a machine tool spindle. The motor built-in type spindle device according to any one of claims 1 to 5.

7. The rotating shaft is a main shaft for a high-speed motor. The motor built-in type spindle device according to any one of claims 1 to 5.

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