JP5499328B2 - Variable preload spindle - Google Patents

Description

  The present invention relates to a variable preload spindle, and more particularly, to a variable preload spindle that prevents the influence of a center-through coolant supply on a bearing preload amount.

  Conventionally, a variable preload type spindle unit has been disclosed as a spindle having a variable preload mechanism capable of changing a preload amount of a bearing (see, for example, Patent Document 1). As shown in FIG. 4, a variable preload spindle unit 100 described in Patent Document 1 includes an outer cylinder 102, a main shaft 103 inserted through the outer cylinder 102, and an angular ball that rotatably supports the main shaft 103 at both front and rear ends. A front bearing 104 and a rear bearing 105, which are bearings, are provided.

  The rear bearing 105 is fitted in a bearing holding component 106 that is fitted to the outer cylinder 102 so as to be movable in the axial direction. The pressure chamber 108 provided between the flange 106a of the bearing holding component 106 and the lid component 107 is fitted with a pressing member 109 that is moved by high-pressure oil supplied from a hydraulic device 110 disposed outside. Yes. Further, an elastic member 111 that presses the flange 106a of the bearing holding component 106 in the direction of the lid component 107 is disposed between the surface of the flange 106a opposite to the pressing member 109 and the outer cylinder 102. .

  The elastic member 111 applies preload to the front bearing 104 and the rear bearing 105 via the bearing holding component 106 by elastic force. When the preload of the front bearing 104 and the rear bearing 105 rises due to the centrifugal force accompanying the rotation of the main shaft 103 and the thermal expansion of the main shaft 103, high pressure oil is introduced from the hydraulic device 110 into the pressure chamber 108 and pressed. By moving the member 109 to the left in the drawing and elastically deforming the elastic member 111, the preload amount is reduced and adjusted to an appropriate value.

Japanese Utility Model Publication No. 5-2802.

  For spindle devices of machine tools such as milling machines and machining centers, cooling is performed by injecting coolant from the tip of the tool as a center through coolant to the workpiece being processed via the coolant supply path provided in the drawbar of the spindle. By doing so, a spindle device is known which improves the machining accuracy of the workpiece and extends the tool life.

  However, when coolant is supplied in a center-through manner via the coolant supply path provided on the main shaft, the main shaft is pressed forward (tool side) by the coolant pressure, and the preload amount applied to the front bearing is thereby reduced to the initial preload amount. As a result, the rigidity becomes low and the shaft vibration increases, resulting in a serious influence on the machining accuracy.

  The preload variable spindle unit 100 of Patent Document 1 introduces high pressure oil into the pressure chamber 108 when the preload amount of the rear bearing 105 increases due to the centrifugal force or thermal expansion accompanying the change in the rotation speed of the main shaft 103. Thus, the elastic member 111 is pressed by the pressing member 109 to reduce the preload amount of the rear bearing 105, and it is possible to cope with the change in the preload amount of the front bearing accompanying the coolant supply as described above. There was room for improvement.

  The present invention has been made in view of the above-described problems. The purpose of the present invention is to provide a variable preload that can always give an appropriate preload amount to the bearing and improve machining accuracy regardless of whether or not coolant is supplied. It is to provide a type spindle.

The above object of the present invention can be achieved by the following constitution.
(1) a housing;
A rotating shaft that supports the tool at one end;
A front bearing disposed on the tool side of the rotating shaft and rotatably supporting the rotating shaft;
A sleeve fitted in the housing and slidable in the axial direction of the rotation shaft with respect to the housing;
A rear bearing disposed on the opposite side of the rotary shaft and fitted in the sleeve, and rotatably supporting the rotary shaft;
Preload application means interposed between the housing and the sleeve and applying a constant pressure preload to the front bearing and the rear bearing via the sleeve;
A variable preload spindle with
The preload applying means includes
A first spring member interposed between the housing and the sleeve;
A hydraulic piston accommodated in the hydraulic chamber so as to move in the hydraulic chamber by hydraulic oil supplied to the hydraulic chamber formed in the housing so as to open to an end surface on the side opposite to the tool of the housing;
A piston stopper for limiting the amount of movement of the hydraulic piston;
A second spring member interposed between the hydraulic piston and the sleeve;
A variable preload spindle characterized by comprising:
(2) The sleeve is fitted in the housing, and a bearing sleeve in which the outer ring of the rear bearing is fitted, and is attached to the bearing sleeve, and positions the outer ring of the rear bearing in the axial direction. An outer ring presser,
The first spring member abuts against a flange portion of the outer ring presser extending radially outward from the bearing sleeve;
The hydraulic chamber is formed on an end surface on the side opposite to the tool of the housing facing the bearing sleeve,
The variable preload spindle according to (1), wherein the second spring member is interposed between the hydraulic piston and a recess formed in a tool side end surface of the bearing sleeve.
(3) The preload applying means can apply a constant pressure preload by the first spring member, and can change a preload amount via the second spring member by the hydraulic piston operated by the hydraulic oil. (1) The variable preload spindle according to (1), wherein
(4) The variable preload spindle according to any one of (1) to (3), wherein the coolant can be supplied by a center through method.

  According to the preload variable spindle of the present invention, the first spring member interposed between the housing and the sleeve and the hydraulic chamber formed in the housing so as to open to the end surface on the side opposite to the tool of the housing are supplied. A hydraulic piston housed in the hydraulic chamber so as to move in the hydraulic chamber by the hydraulic oil, a piston stopper for limiting the amount of movement of the hydraulic piston, a portion of the sleeve housing facing the non-tool side end surface, and the hydraulic piston A second spring member interposed therebetween. Accordingly, the preload amount can be controlled by changing the spring force acting on the sleeve by supplying the hydraulic oil to the hydraulic chamber or shutting off the supply and expanding and contracting the second spring member. Therefore, the preload can be appropriately maintained in response to the change in the preload amount of the front bearing accompanying the coolant supply.

It is sectional drawing of the preload variable spindle which concerns on this invention. It is an enlarged view of the A section of FIG. It is sectional drawing of a rotary joint. It is sectional drawing of the conventional preload variable spindle unit.

  Hereinafter, an embodiment of a variable preload spindle according to the present invention will be described in detail with reference to the drawings.

  As shown in FIGS. 1 and 2, a variable preload spindle 10 according to the present invention includes a housing 11, a rotary shaft 12 that is rotatable with a tool (not shown) attached to one end (left side in the drawing), and a rotary shaft 12. A pair of front bearings (angular ball bearings in this embodiment) 13, 13 disposed on the front end side (left side in the figure) and a pair disposed on the rear end side (right side in the figure) of the rotary shaft 12. And rear sleeves (in this embodiment, angular ball bearings) 14 and 14 and sleeves 15 that are inserted in the housing 11 and are slidable in the axial direction.

  The housing 11 includes a substantially cylindrical housing body 31, a front housing 32 fitted and fixed to the front end side of the housing body 31, and a rear housing 33 fitted and fixed to the rear end side of the housing body 31. ing. A front lid 34 is fastened and fixed to the front end of the front housing 32, and a rear lid 36 is fastened and fixed to the rear end of the rear housing 33.

  A stator 38 of a built-in motor 37 is fixed to the inner periphery of the housing body 31. A rotor 39 is fixed to an intermediate portion in the axial direction of the rotating shaft 12 so as to face the stator 38, and a rotating force is given by a rotating magnetic field generated by the stator 38 to rotationally drive the rotating shaft 12.

  A substantially cylindrical bearing sleeve 16 that is movable in the axial direction is fitted to the inner peripheral surface 33 a of the rear housing 33. Further, an outer ring presser 17 that extends radially outward from the outer peripheral surface of the bearing sleeve 16 is attached to the end surface on the side opposite to the tool of the bearing sleeve 16 with a screw (not shown). An O-ring 28 is attached to a fitting portion between the inner peripheral surface 33 a of the rear housing 33 and the bearing sleeve 16. The bearing sleeve 16 and the outer ring presser 17 constitute the sleeve 15 of the present invention.

  The front bearings 13, 13 have outer rings 18, 18 fitted inside the front housing 32, and inner rings 19, 19 fitted outside the rotary shaft 12, so that the front end side of the rotary shaft 12 is rotatably supported. The outer rings 18 of the front bearings 13, 13 are sandwiched by the step 32 a of the front housing 32 and the front lid 34 via the outer ring spacer 20 and are positioned in the axial direction with respect to the front housing 32. The inner rings 19, 19 are clamped by the front step portion 12 a of the rotating shaft 12 through the inner ring spacer 21 and a nut 22 screwed to the rotating shaft 12, and are positioned in the axial direction with respect to the rotating shaft 12. .

  In the rear bearings 14, 14, the outer rings 23, 23 are fitted into the bearing sleeve 16, and the inner rings 24, 24 are fitted to the rotary shaft 12, so that the rear end side of the rotary shaft 12 is rotatably supported. The outer rings 23, 23 of the rear bearings 14, 14 are sandwiched between the step 16 a of the bearing sleeve 16 and the annular convex portion 17 a of the outer ring retainer 17 via the outer ring spacer 25, and are pivoted with respect to the bearing sleeve 16. Positioned in the direction. The inner rings 24, 24 are clamped by the rear step portion 12 b of the rotating shaft 12 through the inner ring spacer 26 and a nut 27 screwed to the rotating shaft 12, and are positioned in the axial direction with respect to the rotating shaft 12. The

  The rear housing 33 is formed with a plurality of spring chambers 55 that open to the end surface on the side opposite to the tool (the right side surface in the drawing), and the flange portion of the outer ring retainer 17 that extends radially outward from the bearing sleeve 16. Opposite the tool side end face. The first coil spring 56, which is a first spring member, is accommodated in the spring chamber 55 and interposed between the flange portion of the outer ring retainer 17 and the spring chamber 55. A ring-shaped spring guide member 57 having a through-hole 57a through which the first coil spring 56 is inserted is disposed between the outer ring retainer 17 and the spring chamber 55. The first coil spring 56 applies an urging force in the axial direction (right direction in the drawing) to the sleeve 15, thereby applying a constant pressure preload to the front bearings 13, 13 and the rear bearings 14, 14.

  An annular groove-shaped hydraulic chamber 41 is formed in the small diameter portion 33b extending radially inward from the tool side end portion of the rear housing 33 so as to open to the opposite tool side end surface. It faces 16 tool side surfaces (left side surface). A hydraulic piston 43 is slidably fitted in the hydraulic chamber 41 and a hydraulic oil supply path 42 communicates therewith. The hydraulic piston 43 includes a large-diameter portion 43a that is slidably fitted into the hydraulic chamber 41, and a small-diameter portion 43b that protrudes from the hydraulic chamber 41 to the bearing sleeve 16 side. An O-ring 44 is attached to the outer peripheral surface of the large diameter portion 43 a of the hydraulic piston 43.

  The hydraulic piston 43 is formed with a spring seat composed of a bottom portion 43c and a cylindrical portion 43d with which a second coil spring 45, which is a second spring member, can abut. A spring receiving chamber 47, which is a concave portion having a bottom surface 47 a, is formed on the tool-side end surface of the bearing sleeve 16 so as to face the hydraulic chamber 41. The second coil spring 45 is interposed between the spring seat of the hydraulic piston 43 and the bottom surface 47 a of the spring receiving chamber 47.

  A ring-shaped piston stopper 48 is fixed to the end surface on the side opposite to the tool of the small-diameter portion 33 b of the rear housing 33 corresponding to the opening of the hydraulic chamber 41. The piston stopper 48 has a through hole 48a that is slightly larger than the small-diameter portion 43b of the hydraulic piston 43, and the small-diameter portion 43b is fitted in such a manner that it can advance. Thereby, the movement amount of the hydraulic piston 43 is limited within the range of the axial length of the hydraulic chamber 41.

  A pressure control circuit 60 capable of controlling the pressure of the hydraulic oil is connected to the hydraulic oil supply path 42. The pressure control circuit 60 includes a connection pipe 61, a hydraulic pump 62, a flow rate adjustment valve 63, a relief valve 64, and a switching valve 65. By switching the switching valve 65, hydraulic oil having a pressure set in the relief valve 64 is provided. Is supplied to the hydraulic chamber 41 via the hydraulic oil supply passage 42.

  On the rear end side of the rotating shaft 12, a rotation sensor 50 including a magnetic encoder 51 and a sensor 52 that detects magnetism of the magnetic encoder 51, and a rotary joint 53 that supplies a liquid such as cutting coolant to the rotating shaft 12 are arranged. It is installed. As shown in FIG. 3, the rotary joint 53 includes a rotary tube shaft 71, a floating sheet 72, a seal portion 73, a floating sheet mounting portion 74, guide pins 75, and a rotary housing 76.

  A floating seat mounting portion 74 is mounted on the rotary housing 76 so as to seal the opening 76a of the rotary housing 76 from the inside. The floating seat mounting portion 74 is provided with a seal hole (not shown) that communicates with the coolant supply port 77 of the rotary housing 76. The floating sheet 72 is slidably attached to the seal hole in a state in which the rotation is restricted by the guide pin 75. The floating sheet 72 is formed with an axial hole 72a that constitutes a fixed-side flow path. The seal portion 73 includes a seal ring 78 fixed to the rear end portion of the rotary tube shaft 71 and a seal ring 79 fixed to the front end portion of the floating sheet 72. Communicate. Then, a liquid such as a coolant for cutting supplied from a coolant supply device (not shown) to the coolant supply port 77 is supplied to the rotary shaft 12.

  The operation of this embodiment will be described. 1 and 2, the preload variable spindle 10 of the present embodiment is accommodated in the spring chamber 55 and is loaded by the spring force of the first coil spring 56 mounted between the rear housing 33 and the outer ring presser 17. When the sleeve 15 is urged to the right in the figure, the axial position is regulated by the front bearings 13 and 13 whose axial position is regulated by the step 32 a of the front housing 32 and the step 16 a of the bearing sleeve 16. A constant pressure preload is applied to the rear bearings 14, 14. Thereby, the fluctuation of the preload amount due to the influence of the thermal expansion generated with the rotation of the rotating shaft 12 is prevented, and the preload amounts of the front bearings 13 and 13 and the rear bearings 14 and 14 are kept constant.

  Further, the sleeve 15 is biased in the right direction in the figure by the spring force of the second coil spring 45 mounted between the hydraulic piston 43 and the bearing sleeve 16, so that the step portion 32 a of the front housing 32 Corrected preload is applied to the front bearings 13 and 13 whose axial positions are regulated and the rear bearings 14 and 14 whose axial positions are regulated by the step portions 16 a of the bearing sleeve 16. This corrected preload can be changed by moving the hydraulic piston 43 in the hydraulic chamber 41 to change the compression amount of the second coil spring 45 and changing the pressing force of the sleeve 15.

  When machining a workpiece, when a coolant such as coolant is supplied from a coolant supply device (not shown) via the rotary joint 53 in a center-through manner, the rotary shaft 12 is moved to the tool side (left direction in the figure) by the pressure of the coolant. As a result, the preload amount of the front bearings 13 and 13 becomes smaller than the initial preload, and the rigidity of the rotary shaft 12 decreases.

  In this case, the switching valve 65 is switched and hydraulic oil is supplied from the pressure control circuit 60 to the hydraulic chamber 41 and moved to the right in the drawing until the hydraulic piston 43 contacts the piston stopper 48. Then, by compressing the second coil spring 45, the sleeve 15 is pressed with a larger spring force to prevent a decrease in the amount of preload from the initial preload.

  If the amount of increase in the preload due to the compression of the second coil spring 45 at the hydraulic piston 43 is set to the same magnitude as the amount of decrease in the preload due to the coolant pressure, it is easy to switch the switching valve 65. A decrease in the preload amount of the front bearings 13 and 13 due to the coolant supply can be prevented and maintained constant, and a reduction in machining accuracy due to a decrease in the preload amount is prevented.

  Further, since the movement amount of the hydraulic piston 43 is regulated by the piston stopper 48, it is not necessary to control the pressure of the hydraulic oil supplied to the hydraulic chamber 41, and the switching valve is synchronized with the coolant supply timing. The change in the preload amount of the front bearings 13 and 13 due to the coolant supply can be prevented only by switching 65 on / off.

  As described above, according to the preload variable spindle 10 of the present embodiment, the preload applying means includes the first spring member 56 interposed between the rear housing 33 and the sleeve 15, and the rear housing 33. A hydraulic piston 43 accommodated in the hydraulic chamber 41 so as to move in the hydraulic chamber 41 by hydraulic oil supplied to the hydraulic chamber 41 formed in the rear housing 33 so as to open to the end surface on the side opposite to the tool; And a second spring member 45 interposed between the hydraulic piston 43 and a portion of the sleeve 15 that faces the end surface on the side opposite to the tool of the rear housing 33. Accordingly, the hydraulic oil is supplied to the hydraulic chamber 41, or the supply is shut off, the second spring member 45 is expanded and contracted, and the spring force acting on the sleeve 15 is changed to control the preload amount. Rukoto can. Thereby, irrespective of the presence or absence of coolant supply, the preload amount change of the front bearings 13 and 13 can be prevented and the preload amount can be appropriately maintained.

  Note that the present invention is not limited to the above-described embodiments and examples, and modifications, improvements, and the like can be made as appropriate. For example, in the above embodiment, the rolling bearing has been described as an angular ball bearing, but the present invention is not limited to this and can be similarly applied to other types of rolling bearings.

DESCRIPTION OF SYMBOLS 10 Preload variable spindle 11 Housing 12 Rotating shaft 13 Front bearing 14 Rear bearing 15 Sleeve 16 Bearing sleeve 17 Outer ring retainer 23 Outer ring 31 of rear bearing Housing main body 32 Front housing 33 Rear housing 41 Hydraulic chamber 43 Hydraulic piston 45 Second coil Spring (second spring member)
47 Spring receiving chamber (recess)
47a Bottom surface 48 Piston stopper 56 First coil spring (first spring member)

Claims (4)

A housing;
A rotating shaft that supports the tool at one end;
A front bearing disposed on the tool side of the rotating shaft and rotatably supporting the rotating shaft;
A sleeve fitted in the housing and slidable in the axial direction of the rotation shaft with respect to the housing;
A rear bearing disposed on the opposite side of the rotary shaft and fitted in the sleeve, and rotatably supporting the rotary shaft;
Preload application means interposed between the housing and the sleeve and applying a constant pressure preload to the front bearing and the rear bearing via the sleeve;
A variable preload spindle with
The preload applying means includes
A first spring member interposed between the housing and the sleeve;
A hydraulic piston accommodated in the hydraulic chamber so as to move in the hydraulic chamber by hydraulic oil supplied to the hydraulic chamber formed in the housing so as to open to an end surface on the side opposite to the tool of the housing;
A piston stopper for limiting the amount of movement of the hydraulic piston;
A second spring member interposed between the hydraulic piston and the sleeve;
A variable preload spindle characterized by comprising: The sleeve is fitted into the housing, and a bearing sleeve into which the outer ring of the rear bearing is fitted, and an outer ring presser that is attached to the bearing sleeve and positions the outer ring of the rear bearing in the axial direction. Have
The first spring member abuts against a flange portion of the outer ring presser extending radially outward from the bearing sleeve;
The hydraulic chamber is formed on an end surface on the side opposite to the tool of the housing facing the bearing sleeve,
2. The variable preload spindle according to claim 1, wherein the second spring member is interposed between the hydraulic piston and a recess formed in a tool side end surface of the bearing sleeve.   The preload applying means can apply a constant pressure preload by the first spring member, and can change a preload amount via the second spring member by the hydraulic piston operated by the hydraulic oil. The preload variable spindle according to claim 1 or 2, characterized in that the spindle is variable. The variable preload spindle according to any one of claims 1 to 3, wherein the coolant can be supplied by a center through method.

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