JP2019069481A - Hole inner surface cutting processing head - Google Patents

Abstract

To provide a hole inner surface cutting processing head capable of accurately cutting an inner surface of a through-hole formed in a work-piece (including heavy cutting) without using sulfur.SOLUTION: A hole inner surface cutting processing head 1 cuts an inner surface of a through-hole H formed in a work-piece (shaft) W. The cutting processing head 1 includes a columnar head main body 2 rotated around a center shaft of the through-hole H, relatively for the work-piece W, a pair of cutting tools 3a, 3b which are retained by the head main body 2 slidably to the radially outer side with respect to the center shaft and cut the inner surface and a plurality of liquid static pressure pads 8 which are provided on a circumferential surface of the head main body 2 on at least one place along the center shaft. The pair of cutting tools 3a, 3b are arranged separately by 180° in a circumferential direction of the head main body 2 with respect to the center shaft.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a processing head for cutting the inner surface of a through hole formed in a work.

  Patent Document 1 below discloses a device for cutting the inner surface of a through hole formed in a long hollow shaft (work). In the section explaining the prior art of Patent Document 1, the through hole of the long hollow shaft (for example, the total length 3 m, the outer diameter of the main portion 10 to 20 cm) connecting the turbine of the jet engine and the fan (or compressor). The process of cutting the inner surface is described.

  In the process, the core bar is inserted into the through hole of the shaft, and sulfur is cast between the core bar and the inner surface of the through hole. When the core bar is pulled out after the solidification of the sulfur, a through hole through which a cutting head (boring bar) passes is formed in the portion where the core bar was present. The machining head is moved along the through hole inside the sulfur layer, and the inner surface of the shaft is cut together with the sulfur layer.

  Since the core bar is formed with high accuracy, the inner surface of the through hole formed inside the sulfur layer is also formed with high accuracy. Further, the inner surface of the through hole becomes the processing reference of the cutting head and the cutting head is accurately held, so that the processing accuracy can be secured. The sulfur layer also contributes to reducing the friction of the cutting edge (lubrication) and absorbing vibration during cutting.

JP, 2010-188484, A (Drawing 7)

  However, sulfur is difficult to handle, requires recovery after cutting, and requires post-treatment for reuse. In addition, the sulfur layer formed by the above-described method may be cracked or cracked, which may cause problems in cutting. In addition, in the case of so-called heavy cutting where the amount of cutting is large, there is also a problem that the sulfur layer can not sufficiently hold the cutting head. Furthermore, since some sulfur compounds are toxic, it is also necessary to pay attention to their management. Therefore, there is a need for a method that does not use the above-described sulfur.

  An object of the present invention is to provide a hole inner surface cutting head capable of accurately cutting (including heavy cutting) the inner surface of a through hole formed in a work without using sulfur.

  The hole inner surface cutting head according to the present invention is for cutting the inner surface of a through hole formed in a work, and is inserted into the through hole and relative to the work about the central axis of the through hole. A cylindrical head main body which is rotated in the first direction, a pair of first cutting tool and second cutting tool which are held by the head main body so as to be slidable radially outward with respect to the central axis, A plurality of hydrostatic pressure pads provided on the circumferential surface of the head body at at least one location along the central axis, the first cutting tool and the second cutting tool being relative to the central axis It is characterized in that it is spaced apart substantially 180 degrees in the circumferential direction of the head body.

  According to the present invention, since the hydrostatic pressure pad and the pair of cutting tools disposed approximately 180 ° apart are provided, the inner surface of the through hole formed in the work is accurately cut without using sulfur. (Including heavy cutting) can.

FIG. 5 is a cross-sectional view of an embodiment of a bore interior machining head. It is the II-II sectional view taken on the line in FIG. It is the III-III sectional view taken on the line in FIG. It is a block diagram of a cutting device containing the above-mentioned cutting head.

  An embodiment of the hole inner surface cutting head 1 will be described with reference to the drawings. As shown in FIG. 1, the workpiece W in the present embodiment is a long hollow shaft, the cutting head 1 is inserted into the through hole H, and the inner surface of the through hole H is cut by the cutting head 1 . The shaft W to be cut is fixed by a holding mechanism (not shown) of the cutting device. At this time, the central axis of the through hole H is held so as to coincide with the central axis of the cutting head 1. The cutting head 1, which is a part of the cutting device, includes a cylindrical head main body 2 that holds the pair of first cutting tools 3a and second cutting tools 3b. The first byte 3a and the second byte 3b will be described in detail later. A joint rod 4 is fixed to the proximal end of the head body 2.

  The head body 2 is connected to a head rotation device 104 via a joint rod 4. The head body 2 (cutting head 1) inserted into the through hole H is rotated by the head rotating device 104 around the central axis via the joint rod 4. In the present embodiment, the work W is fixed and the head body 2 is rotated, but the head body 2 may be rotated relative to the work W. That is, the head body 2 may be fixed without being rotated, and the workpiece W may be rotated about the central axis. In this case, the head body 2 is fixed to the cutting device, and the head rotation device 104 functions as a workpiece rotation device.

  The head body 2 is also connected to a head stroke device 102 via a joint rod 4. The cutting head 1 (head body 2) is stroked in the through hole H in the central axis direction by the head stroke device 102 via the joint rod 4. The joint rod 4 has a length sufficient to stroke the cutting head 1 over the entire length of the shaft W.

  In the inside of the head body 2 and the joint rod 4, an insertion hole 5 is formed along the central axis thereof. In the insertion hole 5, a rack bar 6 for controlling the amount of projection of the first cutting tool 3a and the second cutting tool 3b in the radial direction is accommodated. The radial direction is perpendicular to the central axis of the head body 2. The proximal end of the rack bar 6 is connected to the rack stroke device 103. The rack bar 6 is stroked relative to the head body 2 by the rack stroke device 103 along the central axis described above.

  Here, the pair of first bit 3 a and second bit 3 b and the rack bar 6 will be described in detail with reference to FIGS. 1 and 2. The cross-sectional shape of the rack bar 6 is basically circular, but a part near the tip has a plate-like cross-section, and a plurality of inclined first rack grooves 6a are formed on one side, and the other side A plurality of inclined second rack grooves 6b are formed in the. The rack bar 6 is cut only at the portion where the first rack groove 6a and the second rack groove 6b are formed.

  On the other hand, a plurality of inclined third rack grooves 30a are formed on the inner side surface of the first cutting tool 3a, and a plurality of inclined fourth rack grooves 30b are formed on the inner side surface of the second cutting tool 3b. The inclination directions of the third rack groove 30a and the fourth rack groove 30b with respect to the stroke direction of the rack bar 6 (the central axis of the through hole H) are opposite to each other. The plurality of first rack grooves 6a are engaged with the plurality of third rack grooves 30a, and the plurality of second rack grooves 6b are engaged with the plurality of fourth rack grooves 30b.

  The first cutting tool 3a and the second cutting tool 3b are slidably held by the head main body 2 in the radial direction, as shown in FIGS. The first cutting tool 3a and the second cutting tool 3b are separated by approximately 180 degrees in the circumferential direction when viewed along the central axis, and are disposed so as to be opposite to each other. In other words, when viewed along the central axis, the first byte 3a and the second byte 3b are arranged on opposite sides of the central axis. Since the inclination directions of the third rack groove 30a and the fourth rack groove 30b with respect to the stroke direction of the rack bar 6 are opposite to each other, the first rack groove 6a and the fourth rack groove 30b engaged with the third rack groove 30a are engaged. The inclination directions of the second rack grooves 6b to be engaged with respect to the stroke direction of the rack bar 6 are also opposite to each other (see FIG. 1).

  Therefore, for example, when the rack bar 6 is stroked to the left in FIG. 1 with respect to the head body 2, the first cutting tool 3 a and the second cutting tool 3 b are slid so as to be stored in the head main body 2. That is, the amount of protrusion of the first bit 3a and the second bit 3b from the head main body 2 is reduced. On the other hand, when the rack bar 6 is stroked to the right in FIG. 1 with respect to the head body 2, the first cutting tool 3 a and the second cutting tool 3 b are slid so as to protrude from the head main body 2.

  Here, the inclination angle α of the first rack groove 6a and the third rack groove 30a is different from the inclination angle β of the second rack groove 6b and the fourth rack groove 30b (the angle direction is not considered, but the size of the angle think of). By setting the inclination angles α and β in this manner, the amount of projection of the second cutting tool 3b from the head main body 2 is always twice the amount of projection of the first cutting tool 3a from the head main body 2. In other words, the cutting radius of the first cutting tool 3a is always smaller than the cutting radius of the second cutting tool 3b (see FIG. 2). Thus, the pair of first cutting tool 3a and second cutting tool 3b, which always have different amounts of projection (cutting radius), are controlled by the single rack bar 6. In the present embodiment, the rack bar 6 in which the first rack groove 6a and the second rack groove 6b described above are formed, the third rack groove 30a formed in the first cutting tool 3a, and the fourth forming the second cutting tool 3b A bite slide mechanism is constructed by the rack groove 30 b and the rack stroke device 103. The bite slide mechanism slides the first bit 3a and the second bit 3b while maintaining the ratio of the amount of projection of the second bit 3b to the amount of projection of the first bit 3a constant (1: 2 in the present embodiment) Do.

  Furthermore, here, the cutting surface of the cutting insert 31a of the first cutting tool 3a with a small amount of protrusion is slightly smaller than the cutting surface of the cutting insert 31b of the second cutting tool 3b with a large amount of protrusion (Not visible in FIG. 1). That is, the cutting insert 31a of the first cutting tool 3a is positioned on the leading side along the central axis with respect to the cutting insert 31b of the second cutting tool 3b. Accordingly, as shown in FIG. 1, the inner surface of the shaft W is cut by being stroked to the right while the cutting head 1 is rotated, but at this time, the first cutting tool 3a with a small amount of protrusion is cut. The insert 31a leads the inner surface of the through hole H in advance. Then, the uncut portion of the inner surface partially cut by the first cutting tool 3a is subsequently cut by the second cutting tool 3b.

  Therefore, the reaction force acting on the cutting insert 31a of the first cutting tool 3a and the cutting insert 31b of the second cutting tool 3b by the cutting is equalized (distributed). As a result, it is easy to carry out heavy cutting (deep) with a large amount of cutting at one time. Further, since the first cutting tool 3a and the second cutting tool 3b are separated by approximately 180 degrees in the circumferential direction, the back forces at the time of cutting cancel each other, and the cutting head 1 is eccentric within the through hole H of the shaft W The cutting force can be reduced and the cutting accuracy is improved. Furthermore, since the main component force and feed component force at the time of cutting are substantially symmetrical with respect to the central axis, the force for eccentrically moving the cutting head 1 with respect to the through hole H can be reduced, and the cutting accuracy is improved.

  Forces acting on the cutting head 1 by arranging the first cutting tool 3a and the second cutting tool 3b in the circumferential direction substantially 180 ° apart as in the present embodiment (main component force, back component force, feed component force And so on), the force for radially deflecting the cutting head 1 can be reduced to about 1⁄5 in the case of heavy cutting as compared to a conventional cutting head having only one cutting tool.

  The description returns to the configuration of the cutting head 1. The head body 2 includes a plurality of hydrostatic pressure pads 8. The plurality of hydrostatic pressure pads 8 not only function as pads for holding the position of the head main body 2, but also function as static pressure coolant bearings. That is, the hydrostatic pressure pad 8 supports the head main body 2 which rotates relative to the work W as a bearing. In the present embodiment, the plurality of hydrostatic pressure pads 8 are disposed at two locations along the central axis of the cutting head 1, and four hydrostatic pressure pads 8 are provided at one location. As shown in FIG. 3, the four hydrostatic pressure pads 8 are evenly arranged in the circumferential direction. The hydrostatic pressure pad 8 forms a liquid film between the rotating cutting head 1 and the inner surface of the shaft W to reduce the friction between them, and cuts the shaft W (through hole H). Position the head 1 stably. By providing the hydrostatic pressure pads 8 at two locations along the central axis, the runout of the cutting head 1 is suppressed. Further, one of the two places is provided as close as possible to the pair of first cutting tool 3a and second cutting tool 3b as much as possible, so that the positions of the cutting inserts 31a and 31b (cutting points) are positioned with high accuracy. ing.

  The hydrostatic pressure pad 8 is formed of a metal softer than the metal of the shaft W, for example, copper, in consideration of contact with the shaft W. Further, each hydrostatic pressure pad 8 is fixed to the head main body 2 with four bolts and is replaceable. The bottom of the hydrostatic pressure pad 8 is flat so that it can be stably attached to the head body 2. On the other hand, the upper surface 8 a of the hydrostatic pressure pad 8 is a curved surface along the outer peripheral surface of the head main body 2 as shown in FIG. 3. The upper surface 8 a of the hydrostatic pressure pad 8 slightly protrudes from the outer peripheral surface of the head main body 2 to prevent the contact between the head main body 2 and the inner surface of the shaft W.

  The upper surface 8a of the hydrostatic pressure pad 8 is a square quadric surface, but a square liquid reservoir 8b is formed at the center thereof. The liquid pool 8b is formed by digging the upper surface 8a slightly. Although the depth of the liquid reservoir 8a is constant, four mounting holes for bolts described above are provided inside (see FIG. 3). At the center of the liquid reservoir 8a, a supply hole 8c for supplying the working fluid to the liquid reservoir 8a is formed. By supplying hydraulic fluid to the liquid pool 8a under pressure, a liquid film is formed between the hydrostatic pressure pad 8 and the inner surface of the shaft W, and the friction between the two is reduced. For the working fluid in the present embodiment, a cutting coolant (cutting fluid) supplied to a cutting point by the pair of first cutting tool 3a and second cutting tool 3b is used.

  The supply path of the cutting coolant to each fluid static pressure pad 8 will be described. As shown in FIG. 1, a first coolant supply passage 9 a is formed at the center of the rack bar 6. The first coolant supply path 9a is extended to the base end of the rack bar 6, and is connected to a coolant unit 105 that pumps cutting coolant. The end of the first coolant supply passage 9 a is radially bent and is opened on the circumferential surface of the rack bar 6.

  A coolant chamber 9b is formed in an open portion of the first coolant supply passage 9a. The coolant chamber 9 b is constituted by a gap between the rack bar 6 and the inner surface of the insertion hole 5 of the head body 2 and a gap between the base end surface of the head body 2 and the tip surface of the joint rod 4. In a gap between the rack bar 6 forming the coolant chamber 9 b and the inner surface of the insertion hole 5 of the head main body 2, two second coolant supply paths 9 c connected to the supply holes 8 c of the respective hydrostatic pressure pads 8. Is open (see FIG. 3).

  Each second coolant supply passage 9c extends in the radial direction from the opening of the coolant chamber 9b and then extends parallel to the central axis inside the head body 2. Each second coolant supply passage 9 c is branched toward the supply holes 8 c of the two hydrostatic pressure pads 8 along the way, and its end is also bent in the radial direction so that the other two hydrostatic pressure pads 8 are It is connected to the supply hole 8c (see FIG. 3). That is, the cutting coolant is supplied to the liquid reservoir 8 b of the four hydrostatic pressure pads 8 by one second coolant supply passage 9 c.

  In the coolant chamber 9b, two third coolant supply paths 9d for supplying cutting coolant to the pair of first cutting tool 3a and second cutting tool 3b are also opened (not shown). The third coolant supply passage 9d is also extended inside the head body 2 in parallel to its central axis (see FIG. 3). The end of the third coolant supply passage 9d is opened toward the pair of first cutting tool 3a and second cutting tool 3b (see FIG. 1). The cutting coolant supplied to the pair of first cutting tool 3a and second cutting tool 3b, as usual, reduces the friction during cutting and cools the heat generated by the cutting.

  That is, in the present embodiment, the supply of cutting coolant to all of the hydrostatic pressure pads 8 and the pair of first cutting tools 3a and second cutting tools 3b is performed by the supply source (the coolant tank 105a and the coolant pump 105b of the coolant unit 105). It has been done. In addition, after the coolant coolant discharged from the liquid reservoir 8b of the hydrostatic pressure pad 8 and the coolant coolant supplied to the pair of first cutting tool 3a and second cutting tool 3b flow out from the through hole H of the shaft W, the coolant unit 105 To be collected.

  Thus, the cutting coolant supplied to the liquid reservoir 8b of the total of eight hydrostatic pressure pads 8 forms a liquid film with the inner surface of the shaft W, and the cutting head 1 is moved by the pressure of the cutting coolant. The inside of the through hole H is in a floating state. As a result, the rotation of the cutting head 1 in the through hole H is lubricated, and the cutting head 1 is accurately positioned in the through hole H.

  Note that the plurality of hydrostatic pressure pads 8 provided at two locations along the central axis basically have the same configuration, and both are as a cross-sectional view taken along line III-III in FIG. Indicated. However, in the present embodiment, the area of the liquid reservoir 8b of each liquid static pressure pad 8 (on the left side in FIG. 1) closer to the pair of first cutting tool 3a and second cutting tool 3b (cutting point) It is made wider than the area of the liquid reservoir 8b of each liquid static pressure pad 8 (right side in FIG. 1). Therefore, the holding force by the hydrostatic pressure pad 8 is higher in the plurality of hydrostatic pressure pads 8 closer to the pair of first cutting tool 3a and the second cutting tool 3b.

  That is, the holding force of the cutting head 1 by the four hydrostatic pressure pads 8 on one side (left side in FIG. 1) closer to the pair of first bite 3a and second bite 3b among the two points is the pair of two points. The holding force of the cutting head 1 by the four hydrostatic pressure pads 8 on the other side (right side in FIG. 1) far from the first cutting tool 3a and the second cutting tool 3b is set higher. As a result, it is possible to more accurately maintain the cutting positions of the pair of first cutting tool 3a and second cutting tool 3b while countering the reaction force at the time of cutting, and it is possible to further suppress the vibration at the time of cutting. Also, with such a configuration, the cutting coolant used in the four hydrostatic pressure pads 8 in the other (right side in FIG. 1) far from the pair of first cutting tool 3a and second cutting tool 3b in two places The amount can be reduced and the total usage of cutting coolant is reduced. Furthermore, with such a configuration, when the cutting coolant is supplied from a single source, that is, even when the cutting coolant has only a single supply pressure, the hydrostatic pressure pad 8 is held. Force can be changed by position.

  The cutting device 100 provided with the cutting head 1 described above will be described with reference to FIG. In addition, since the head stroke apparatus 102, the rack stroke apparatus 103, the head rotation apparatus 104, the coolant unit 105, etc. which were mentioned above have the structure similar to a well-known apparatus, description of the detailed structure is abbreviate | omitted. Below, the whole structure of the cutting device 100 is demonstrated.

  The head stroke device 102 includes a stroke drive source 102 a that causes the cutting head 1 to stroke via the joint rod 4. When the stroke mechanism is configured by a feed screw, the stroke drive source 102a is a feed motor that rotates the feed screw. The stroke drive source 102 a is connected to a control unit 101 described later, and is controlled by the control unit 101. The stroke mechanism is not limited to the above-described mechanism as long as the cutting head 1 can be made to stroke with high accuracy. For example, a ball screw mechanism, a rack and pinion mechanism, a belt / chain drive mechanism, a linear actuator, and the like can also be used. In these cases, the stroke drive source 102 a is an actuator that causes the cutting head 1 to stroke.

  The rack stroke device 103 includes an actuator 103 a that causes the rack bar 6 to stroke relative to the head body 2. When the stroke mechanism is configured by a feed screw, the actuator 103a is a feed motor that rotates the feed screw. The actuator 103 a is also connected to the control unit 101 described later, and is controlled by the control unit 101. The stroke mechanism is not limited to the above-described mechanism as long as the rack bar 6 can be stroked with high accuracy. For example, a ball screw mechanism, a rack and pinion mechanism, a belt / chain drive mechanism, a linear actuator, and the like can also be used.

  The head rotation device 104 includes a rotational drive source 104 a that rotates the cutting head 1 via the joint rod 4. The rotary drive source 104 a rotatably holds the joint rod 4 and rotates the joint rod 4 by its rotary motor. The rotational drive source 104 a is also connected to the control unit 101 described later, and is controlled by the control unit 101. The joint rod 4 may be rotated by a rotary motor via a gear mechanism.

  The coolant unit 105 described above is also connected to the control unit 101, and is controlled by the control unit 101. As described above, the coolant unit 105 includes the coolant tank 105 a and the coolant pump 105 b. The recovered cutting coolant is returned to the coolant tank 105a again after chips and the like are removed by the reprocessing apparatus 105c.

  As described above, the control unit 101 is connected to the stroke drive source 102 a of the head stroke device 102 and controls the stroke position (cutting position) of the cutting head 1. At this time, the stroke position of the cutting head 1 is grasped by the control unit 101 based on the number of rotations of the feed motor as the stroke drive source 102a (control information of the stroke drive source 102a). The stroke position of the cutting head 1 may be grasped not by the number of rotations of the feed motor but by the number of rotations of the feed screw or the number of rotations of the gear when the gear mechanism is interposed. After the shaft W is held by the holding device, the stroke position of the cutting head 1 is initially set before starting cutting.

  The control unit 101 may also be connected to the rotational drive source 104 a of the head rotation device 104. In this case, the rotational position of the cutting head 1, that is, the rotational positions of the pair of the first cutting tool 3a and the second cutting tool 3b can also be controlled. In this way, the rotational position of the pair of first bite 3a and second bite 3b is grasped by the control unit 101 based on the state of the rotational drive source 104a. The rotational positions of the pair of first cutting tools 3a and the second cutting tool 3b may be grasped by the rotational speed of the gears, not by the state of the rotational drive source 104a itself, but by the gear mechanism. When such control is performed, the rotational position of the cutting head 1 is initially set before the cutting is started after the shaft W is held by the holding device.

  The control unit 101 is also connected to the actuator 103a of the rack stroke device 103, and also controls the cutting radius of the pair of first cutting tool 3a and second cutting tool 3b. At this time, the cutting radius (radial position) of the pair of first cutting tool 3a and second cutting tool 3b is grasped by the control unit 101 based on the control state of the actuator 103a. The control unit 101 can also variably control the amount of projection (cutting radius) of the first cutting tool 3a and the second cutting tool 3b during cutting by controlling the actuator 103a. A detector may be provided to detect the stroke position of the rack bar 6 with respect to the head body 2 instead of the state of the actuator 103a to grasp the cutting radius of the pair of first cutting tool 3a and second cutting tool 3b. In addition, after holding the shaft W in the holding device, the cutting radii of the pair of first cutting tool 3a and second cutting tool 3b are initialized (the tip positions of the cutting inserts 31a and 31b are initialized) before cutting is started. ).

  The stroke position of the cutting head 1 with respect to the shaft W, the rotational position and rotational speed of the cutting head 1 with respect to the shaft W, and the projection of the pair of first cutting tools 3a and 2b by the cutting device 100 configured as described above. Cutting is performed while the amount (cutting radius: stroke amount of the rack bar 6), the supply amount of the cutting coolant and the supply pressure (pressure of the liquid static pressure pad 8), and the like are controlled by the control unit 101.

  In the present embodiment, the plurality of hydrostatic pressure pads 8 are provided on the circumferential surface of the head body 2 at at least one location along the central axis, and the head body 2 is held slidably in the radial direction. A pair of first cutting tools 3a and second cutting tools 3b are provided spaced approximately 180 ° apart in the direction. Therefore, the hydrostatic pressure pad 8 can accurately position the cutting head 1 rotatably in the through hole H and can lubricate the rotation of the cutting head 1. Further, since the pair of first cutting tools 3a and the second cutting tools 3b are separated by approximately 180 degrees in the circumferential direction, the reaction force at the time of cutting is offset, and the magnitude of the reaction force can be reduced. As a result, heavy cutting with a large amount of cutting (deep) can be reliably performed. Furthermore, since the reaction force at the time of cutting is substantially symmetrical with respect to the central axis, the eccentricity of the cutting head 1 in the through hole H is suppressed, and the force for tilting the cutting head 1 in the through hole H is also It can be made smaller and the cutting accuracy is improved.

  Further, in the present embodiment, the amounts of projection of the pair of first cutting tools 3a and second cutting tools 3b from the head main body 2 along the radial direction are different. Therefore, the reaction force is made the same by making the cutting amount by the first cutting tool 3a with a small amount of protrusion the same as the cutting amount by the second cutting tool 3b with a large amount of protrusion. As a result, since the reaction force is equalized (distributed), cutting can be performed reliably. At the same time, by using the second cutting tool 3b having a large amount of protrusion in combination with the first cutting tool 3a having a small amount of protrusion, heavy cutting having a large amount of cutting (cutting amount) can be reliably performed.

  Here, in the present embodiment, the cutting insert 31a of the first cutting tool 3a having a small amount of protrusion from the head body 2 leads along the central axis before the cutting insert 31b of the second cutting tool 3b having a large amount of protrusion. Is located in That is, the cutting insert 31a of the first cutting tool 3a with a small amount of protrusion surely cuts the inner surface of the shaft W first. The cutting insert 31b of the second cutting tool 3b having a large amount of projection cuts the uncut portion of the inner surface partially cut by the cutting insert 31a of the first cutting tool 3a having a small amount of projection. Therefore, the reaction force acting on the two cutting inserts 31a and 31b is equalized (distributed), and heavy cutting can be performed more reliably. Moreover, since cutting is shared by the two cutting inserts 31a and 31b, reaction force and vibration at the time of cutting can be reduced, and cutting precision is further improved.

  Further, in the present embodiment, the first rack groove 6a and the second rack groove 6b are formed in the rack bar 6 in the insertion hole 5, and the third rack groove 30a engaged with the first rack groove 6a is the first bit 3a. A fourth rack groove 30b is formed in the second cutting tool 3b and is engaged with the second rack groove 6b. Here, the inclining direction of the first rack groove 6a and the inclining direction of the second rack groove 6b are opposite to each other, and the size of the inclination of the first rack groove 6a is the size of the inclination of the second rack groove 6b It is different. Therefore, by making the single rack bar 6 stroke, it is possible to simultaneously slide in the radial direction two bits (the first bit 3a and the second bit 3b) having different projecting amounts. In addition, although these components are built in the rotating cutting head 1, the mechanism is simple and the operation reliability is also improved.

  Further, in the present embodiment, the hydraulic fluid of the hydrostatic pressure pad 8 is a cutting coolant. Since the cutting coolant is used as the hydraulic fluid of the hydrostatic pressure pad 8, it is not necessary to construct a new supply system for the hydraulic fluid of the hydrostatic pressure pad 8 inside the cutting head 1 that rotates. Since the cutting coolant is supplied to the cutting point by the cutting tool (the first cutting tool 3a and the second cutting tool 3b), a supply system therefor can be utilized. Therefore, the configuration of the cutting head 1 can be simplified, and the use of the cutting coolant contributes to weight reduction and reduction in the number of parts. Furthermore, the hydraulic fluid of the hydrostatic pressure pad 8 and the cutting coolant supplied to the cutting point by the cutting tool (the first cutting tool 3a and the second cutting tool 3b) are mixed and discharged from the through hole H of the work W. In the present embodiment, since the hydraulic fluid of the hydrostatic pressure pad 8 is a cutting coolant, accessory equipment such as separation equipment for separating the discharged hydraulic fluid and the coolant is not necessary.

  Further, in the present embodiment, a plurality of hydrostatic pressure pads 8 are disposed on the circumferential surface of the head body 2 at two locations along the central axis. Therefore, it is possible to more effectively suppress axial runout of the cutting head 1 in the through hole H (inclination of the central axis of the cutting head 1 with respect to the central axis of the through hole H). At the same time, the rotation of the cutting head 1 can be lubricated more reliably.

  Further, in the present embodiment, the projecting amount (cutting radius) of the first cutting tool 3a and the second cutting tool 3b can be variably controlled during cutting by the cutting tool slide mechanism provided with the rack bar and the first to fourth rack grooves. . For this reason, the inner surface of the through hole H can be cut into a free shape by cutting the inner surface of the through hole H while changing the cutting inner diameter during cutting. For example, the through hole H can be cut into a tapered hole whose diameter is gradually increased or reduced, or the inner surface of the through hole H can be cut as a curved surface in the central axis direction (a naturally curved surface) Also, it is possible to cut into a locally expanded or contracted shape.

  Furthermore, the plurality of hydrostatic pressure pads 8 of the present embodiment are also static pressure coolant bearings that support the head body 2 that rotates relative to the workpiece W. That is, the hydrostatic pressure pad 8 functions as a bearing when cutting the inner surface of the through hole H with the through hole H of the workpiece W as a guide hole (lower hole). As described above, in order to cut the inner surface of the through hole H into a free shape, a situation where a large cutting force is loaded on the cutting head 1 (the first cutting tool 3a and the second cutting tool 3b), for example, the cutting amount Even in many situations, it must be able to cut stably. If the hydrostatic pressure pad 8 is a static pressure coolant bearing, stable cutting can be assured more reliably. That is, if the hydrostatic pressure pad 8 functions as a static pressure coolant bearing, it is convenient to cut the inner surface of the through hole H into the above-described complicated shape. In addition, if the hydrostatic pressure pad 8 is a static pressure coolant bearing, cutting can be performed stably even when the inner surface of the through hole H is cut to a constant radius, so that cutting with higher accuracy can be realized.

  Here, in the present embodiment, the holding force of the cutting head 1 by the four hydrostatic pressure pads 8 in one of the two locations close to the cutting tool (the first cutting tool 3a and the second cutting tool 3b) is the other one far from the cutting tool The holding force of the cutting head 1 by the four hydrostatic pressure pads 8 is set higher. Therefore, the cutting head 1 can be firmly held at a position close to the cutting tool so that the cutting position of the cutting tool can be maintained more accurately while countering the reaction force during cutting, and the vibration at the cutting can be further suppressed. On the other hand, the hydrostatic pressure pad 8 which is far from the cutting tool holds the rotating cutting head 1 and maintains a holding force sufficient to lubricate the rotation, but suppresses the consumption of the cutting coolant. Contribute to

  The present invention is not limited to the above embodiment. For example, although the work W of the present embodiment is a hollow shaft, it is not limited to the hollow shaft as long as the hole to be cut is formed in advance.

  Moreover, in the said embodiment, although the four hydrostatic pressure pads 8 were provided in one place, multiple should just be provided in one place. Providing three or more hydrostatic pressure pads 8 at one place is preferable in order to uniformly hold the rotating cutting head 1. Two hydrostatic pressure pads 8 may be provided at one place. In this case, the two hydrostatic pressure pads 8 are separated by 180 ° with respect to the central axis. Furthermore, two hydrostatic pressure pads 8 are provided at another location, and these two hydrostatic pressure pads 8 are also separated by 180 ° with respect to the central axis. Then, it is preferable to shift the positions of the two static pressure pads 8 by 90 °.

  Moreover, in the said embodiment, the four hydrostatic pressure pads 8 provided in one place were equally provided in the circumferential direction. However, due to the arrangement of the piping in the head main body 2 and the like, it may not be accurately provided evenly, so it may not be provided uniformly in the circumferential direction.

  Further, in the above-described embodiment, the supply of the cutting coolant to the hydrostatic pressure pad 8 and the supply of the cutting coolant to the pair of first cutting tool 3a and the second cutting tool 3b (cutting point) are integrated. However, the supply of cutting coolant to the hydrostatic pressure pad 8 and the supply of cutting coolant to the pair of first cutting tool 3a and second cutting tool 3b (cutting point) are separate systems, and the supply pressure is different. You may

  In the above embodiment, the cutting insert 31a of the cutting tool (first cutting tool 3a) with a small amount of protrusion from the head main body 2 is closer to the central axis than the cutting insert 31b of the cutting tool (the second cutting tool 3b) with a large amount of projection It is located on the cutting lead side along. In this way, preferably, the two cutting inserts 31a and 31b can share the cutting reliably, but the two cutting inserts 31a and 31b may be arranged at the same position along the central axis.

  In the above embodiment, the first cutting tool 3a and the second cutting tool 3b are provided slidably in the radial direction perpendicular to the central axis of the through hole H. However, the first cutting tool 3a and the second cutting tool 3b may be provided slidably in the radially outward direction with respect to the central axis. That is, the sliding directions of the first cutting tool 3a and the second cutting tool 3b may not be perpendicular to the central axis but may be oblique to the central axis. When the first cutting tool 3a and the second cutting tool 3b can slide radially outward, they can slide back inward.

  Further, in the present embodiment, a bite slide mechanism that slides the first bit 3a and the second bit 3b while maintaining the ratio of the amount of protrusion constant is the rack bar 6 (first rack groove 6a, second rack groove 6b) , The third rack groove 30a, the fourth rack groove 30b, and the rack stroke device 103. However, the tool slide mechanism may be constructed by a feed screw mechanism or the like.

1 cutting head 2 head main body 3a first bit 3b second bit 4 joint rod 5 insertion hole 6 rack bar (biting stroke mechanism)
6a 1st rack groove (tool stroke mechanism)
6b Second rack groove (tool stroke mechanism)
8 Hydrostatic Pressure Pad 9a First coolant supply passage 9b Coolant chamber 9c Second coolant supply passage 9d Third coolant supply passage 30a Third rack groove (bite stroke mechanism)
30b 4th rack groove (tool stroke mechanism)
31a cutting insert 31b cutting insert W work (shaft)
H through hole

Claims (8)

A hole inner surface cutting head for cutting an inner surface of a through hole formed in a work
A cylindrical head main body inserted into the through hole and rotated around the central axis of the through hole relative to the work;
A pair of first and second cutting tools for cutting the inner surface, held by the head body so as to be slidable radially outward with respect to the central axis;
A plurality of hydrostatic pressure pads provided on a circumferential surface of the head body at at least one location along the central axis;
The hole inner surface cutting head according to claim 1, wherein the first cutting tool and the second cutting tool are spaced apart substantially 180 degrees in the circumferential direction of the head body with respect to the central axis. The amount of protrusion of the first cutting tool radially outward from the head body is different from the amount of protrusion of the second cutting tool,
The apparatus further comprises a tool slide mechanism for sliding the first tool and the second tool while maintaining the ratio of the amount of protrusion of the second tool to the amount of protrusion of the first tool constant. The hole inner surface cutting head according to claim 1. The first cutting tool and the second cutting tool each have a cutting insert,
The cutting insert of the first cutting tool with a small amount of protrusion is positioned on the cutting leading side along the central axis with respect to the cutting insert of the second cutting tool with a large amount of protrusion. The hole inner surface cutting head according to claim 2. The bite slide mechanism is housed in an insertion hole formed at the center of the head body, and the rack bar which can be stroked relative to the head body, and a part of the rack bar is formed in a plate shape A plurality of inclined first rack grooves formed on the one surface, a plurality of inclined second rack grooves formed on the other surface, and the first rack groove formed on the first cutting tool And a plurality of fourth rack grooves formed on the second cutting tool and engaged with the second rack groove.
The inclination direction of the first rack groove with respect to the stroke direction of the rack bar and the inclination direction of the second rack groove with respect to the stroke direction are opposite to each other,
The hole inner surface machining head according to claim 2 or 3, wherein the magnitude of the inclination of the first rack groove with respect to the stroke direction is different from the magnitude of the inclination of the second rack groove with respect to the stroke direction.   The hydraulic fluid of the said hydrostatic pressure pad is a cutting coolant supplied to the cutting location of the said inner surface by the said 1st cutting tool and the said 2nd cutting tool, The any one of the Claims 1-4 characterized by the above-mentioned. A hole inner surface cutting head as described.   The hole inner surface cutting according to any one of claims 1 to 5, wherein a plurality of said hydrostatic pressure pads are arranged on said peripheral surface of said head body at two positions along said central axis, respectively. Processing head.   The holding force of the cutting head by the plurality of hydrostatic pressure pads on one side closer to the pair of the first cutting tool and the second cutting tool among the two positions is the pair of the first cutting tool and the pair of the first bit The hole inner surface cutting head according to claim 6, which is set higher than the holding force of the cutting head by the plurality of hydrostatic pressure pads far from the second cutting tool.   The internal hole surface machining head according to any one of claims 1 to 5, wherein the hydrostatic pressure pad is also a static pressure coolant bearing.

Images