JP3814021B2 - Tool holding device for machine tools - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, a wedge member such as a collet disposed at the tip of the draw bar is engaged with the flange surface of the pull stud of the tool while the taper surface of the tool is in contact with the taper surface of the main shaft, and the draw bar is urged. The present invention relates to a tool holding device for a machine tool that holds a tool on a spindle.
[0002]
[Prior art]
FIG. 6 is a cross-sectional view of the spindle head of the machine tool in a state where the tool is held. Reference numeral 1 denotes a tool or a holder for holding the tool (hereinafter referred to as a tool together), a tapered surface 2 is formed on the outer periphery, and a pull stud 3 is fixed to the end. Note that tapered surfaces 3b and 3c are formed at both ends of the flange portion 3a of the pull stud 3, respectively. Reference numeral 4 denotes a main shaft, and a tapered surface 5 that engages with the tapered surface 2 is formed on the inner surface of the tip, and a relief hole 6 and a guide hole 7 are formed inside. A collet 8 is divided into a plurality of parts in the radial direction and is positioned in the axial direction by a draw bar 9. An annular spring 10 biases the collet 8. A plurality of disc springs 11 are arranged side by side in the axial direction, and urge the draw bar 9 to the right in the figure with a force of 10 to 12 kN. An air cylinder is arranged at the other end (not shown) of the draw bar 9.
[0003]
The operation will be described below. When exchanging the tool 1, an air cylinder (not shown) is operated to move the draw bar 9 to the left against the disc spring 11. When the tip of the collet 8 moves from the guide hole 7 to the escape hole 6, as shown in FIG. 7, the collet 8 is opened in the radial direction by the spring 10, and the inner diameter becomes larger than the outer diameter of the flange portion 3a. In this state, the tool 1 is removed from the main shaft 4. In order to make it easy to remove the tool 1 from the main shaft 4, after the inner diameter of the collet 8 becomes larger than the outer diameter of the flange portion 3a, the end surface of the pull stud 3 at the distal end 9a of the draw bar 9 at the moving end of the air cylinder. Is slightly pushed (for example, it may be several tens of μm). Next, another tool 1 is inserted into the main shaft 4, the tapered surface 2 is brought into contact with the tapered surface 5, and then an air cylinder (not shown) is operated in the opposite direction. Then, the draw bar 9 is moved to the right by the disc spring 11, and the collet 8 is closed against the spring 10 when moving from the escape hole 6 to the guide hole 7. And it moves to the right further, the inner surface 8a of the flange part 3a of the collet 8 contacts the taper surface 3c, and urges the tool 1 to the right. As a result, the tool 1 and the main shaft 4 are united by the frictional force between the tapered surface 2 of the tool 1 and the tapered surface 5 of the main shaft 4.
[0004]
[Problems to be solved by the invention]
However, when the tool 1 is, for example, an end mill, a force (hereinafter referred to as a pulling force) in the direction of pulling out the tool 1 from the main shaft 4 (hereinafter referred to as a pulling force) is applied to the cutting edge (not shown) during machining, particularly during heavy cutting. The pulling force becomes larger than the force of the disc spring 11, and the tapered surface 2 and the tapered surface 5 may be instantaneously separated. And when the said separation | spacing generate | occur | produced, since the rotational force of the main shaft 4 was not transmitted to the tool 1, the blade edge was damaged. In addition, when the separation is generated in vibration, the contact surface between the tapered surface 2 and the tapered surface 5 is worn or rusted, so-called fretting (fretting / corrosion) occurs. In this case, fretting can be prevented by increasing the urging force of the spring 11, but it is necessary to increase the capacity of the air cylinder.
[0005]
An object of the present invention is to solve the above-mentioned problems, engage a wedge member arranged at the tip of the draw bar with the flange surface of the pull stud of the tool, and urge the draw bar to hold the tool on the spindle. To provide a tool holding device for a machine tool that can prevent damage to the blade edge and fretting of the spindle and the taper portion of the tool even when the force for biasing the draw bar remains the same. is there.
[0006]
[Means for Solving the Problems]
In the present invention, the wedge member (33) disposed at the tip of the draw bar (9) is engaged with the flange surface (3c) of the pull stud (3) of the tool (1), and the draw bar is moved to the first biasing means (11). In a tool holding device of a machine tool that is held by the main shaft (4) by being urged by
A positioning means (32) is provided which is inserted into a guide hole (7) formed in the main shaft (4) so as to be axially movable and is integrally connected to the draw bar (9),
Between the outer peripheral surface of the wedge member (33) and the inner peripheral surface of the positioning means (32), there are provided joint portions (32b, 33f) that contact each other and perform a wedge action,
In a state where the tool (1) is held on the main shaft (4), the joint (32b,) is caused by relative movement of the positioning means (32) with respect to the wedge member (33) based on the bias of the draw bar (9). The wedge member (33) is engaged with the flange surface (3c) based on the wedge action of 33f), and the positioning means (32) positions the wedge member while preventing the wedge member from spreading.
[0007]
In the present invention, the wedge member (33) includes a first tapered surface (33c) that engages with the flange surface (3c) and a second tapered surface (33f) that constitutes the joint portion. Have
The second tapered surface of the wedge member corner (a) with respect to the axis of (33f), is rather smaller set than the corner (b) relative to the axis of the first tapered surface (33c).
[0008]
Further, according to the present invention, a third tapered surface (33 a ) is provided at the tip of the wedge member (33), a contact portion (31b) is provided integrally with the main shaft (4), and the wedge member ( 33) and the draw bar (9), the second biasing means (35) for biasing the third taper surface (33a) of the wedge member so as to abut against the abutting portion (31b). interposing a, more movement of the tool releasing direction of the drawbar, relative movement in the axial direction the wedge member on the basis of the biases (33) relative to the spindle (4) of said second biasing means (35) The wedge member is moved so as to be released from the flange surface (3c) by the contact between the third tapered surface (33a) and the contact portion (31b).
[0010]
[Action]
Based on the above configuration, in order to mount and hold the tool (1), the pull stud (3) of the tool (1) is inserted into the main shaft (4), and in this state, the draw bar (9) is attached to, for example, a disc spring (11 ). Then, the positioning means (cylinder case) (32) integral with the draw bar (9) moves, and the wedge member acts by the wedge action of the wedge member (collet) (33) and the joint (33f, 33b) of the positioning means. (33) engages the flange surface (3c) of the pull stud (3).
[0011]
At this time, the angle (a) formed by the second tapered surface (33f) of the wedge member constituting the joint portion is larger than the angle (b) formed by the first tapered surface (33c) engaged with the flange surface. The biasing force of the draw bar (9) is boosted by the wedge action of the second tapered surface (33f), and the first tapered surface (33c) is engaged with the flange surface (3c). Match. Further, when a force acts in the direction of pulling out the tool (1) from the main shaft (4), the positioning means (32) is boosted by the second taper surface (33f) and the positioning means (32) is guided into the guide hole (7) of the main shaft (4). Pressed against.
[0012]
Thus, the wedge member (33) is positioned by being prevented from spreading outward by the positioning means (32), and the force in the direction of pulling out the tool (1) is determined by the tool (1) and the pull stud (3). , Flange surface (3c), first taper surface (33c), wedge member (33), third taper surface (33a), contact portion (31b), collet opener (31), main shaft (4), taper A closed loop (R) consisting of a surface (5) and a tapered surface (2) of the tool is constructed, and the tool (1) is securely held by a mechanical lock.
[0013]
On the other hand, when the draw bar (9) is moved against the disc spring (11) by an air cylinder, for example, the wedge member (collet) (33) is moved through the collet holder (34) and the spring (35), for example. The third taper surface (33a) comes into contact with a contact portion (33a) integrated with a main shaft such as a boss (31), for example, and the wedge member (33) is expanded in the outer diameter direction to form a flange surface (3c). Release the engagement. In this state, the tool (1) can be removed from the main shaft (4).
[0014]
In addition, although the code | symbol in the said parenthesis is for contrast with drawing, it does not limit the structure of this invention at all.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
1 is a cross-sectional view of a main part of a spindle head of a machine tool in a state where a tool is held according to an embodiment of the present invention, and FIG. 2 is a main part of the spindle head of a machine tool in a state where a tool is not held. FIG. 3 is an enlarged view of the main part, and FIG. 4 is a front view of the collet holder. 6 and 7 are given the same reference numerals. 31 is a collet opener, the outer periphery is fitted in the guide hole 7 of the main shaft 4, and a boss 31a is formed at one end. 31b is a tapered surface formed at the end of the boss 31a, 31c is a hole, and the diameter thereof is larger than the outer diameter of the flange portion 3a. Reference numeral 32 denotes an annular cylinder case, the outer periphery of which is fitted into the guide hole 7 of the main shaft 4, and a hole 32a that is fitted around the boss 31a is formed at one end. A tapered surface 32b connects the hole 32a and the hole 32c having a larger diameter than the hole 32a. The cylinder case 32 is integral with the draw bar 9 by a female screw 32 d screwed into the male screw 9 b of the draw bar 9 on the rear end side. Reference numeral 33 denotes a collet, which will be described in detail later. Reference numeral 34 denotes a collet holder. The outer periphery is fitted into a hole 32c of the cylinder case, and three guide grooves 34a extending in the radial direction for positioning the collet 33 in the radial direction are provided on one side surface. Is formed. Further, the bottom surface 34c of the guide groove 34a is formed in a tapered surface in a direction (tapered surface 3c direction) that becomes deeper toward the outer diameter. In addition, as shown in FIG. 4, the adjacent side surfaces of the guide groove 34a are parallel to each other. Reference numeral 35 denotes a disc spring which is contracted between the collet holder 34 and the flange portion 9 c of the draw bar 9. Note that an air cylinder is arranged on the rear end side of the draw bar 9 (not shown) as in the case of FIG.
[0016]
Next, the shape of the collet 33 will be described in detail with reference to FIG. In the figure, the solid line indicates the position of each member when the tool 1 is held, and the two-dot chain line indicates the position of the collet 33 and the cylinder case 32 when the tool 1 is replaced. First, the inner shape will be described. The tip of the collet 33 is formed in a V shape, and the tapered surface 33a has the same angle as the tapered surface 31b of the collet opener. 33b is a surface parallel to the axis, 33c is a tapered surface having the same angle as the tapered surface 3c, and 33d is a surface connecting the tapered surface 33c and the rear end portion 33e, and is parallel to the axis. Next, the outer shape of the collet 33 will be described. Reference numeral 33f denotes a tapered surface, and an angle a formed by the tapered surface 33f and the axis is smaller than an angle b formed by the tapered surface 33c and the axis, for example, the cotangent value is ½ or less. 33g is a plane parallel to the axis. The rear end portion 33e is a tapered surface having the same angle as the bottom surface 34c. One collet 33 is obtained by dividing the annular part on which each of the surfaces is formed into three in the radial direction, and further forming the divided surface in parallel with the diameter. It is arranged in the circumferential direction. The collet is a wedge member, and the cylinder case 32 constitutes a positioning means for the wedge member.
[0017]
Hereinafter, an operation when the tool 1 is replaced will be described. When an air cylinder (not shown) is operated and the rear end of the draw bar 9 is urged, the cylinder case 32 integrated with the draw bar 9 moves to the left. Since the collet 33 is urged to the left in the figure by the disc spring 35, the tapered surface 33a, the tapered surface 31b, and the rear end portion 33e abut against the bottom surface 34c of the guide groove 34a as the hole 32a moves. In this state, the surface 33b is located outside the outer diameter of the flange portion 3a at the moving end of the air cylinder, and the tip of the draw bar 9 is just before the moving end as in the conventional case. 9a pushes the end face of the pull stud 3 by, for example, several tens of μm. Note that, at the moving end of the air cylinder, a gap is formed between the surface 31d perpendicular to the axis of the collet opener 31 and the end surface 32e of the cylinder case 32 and between the hole 32c and the surface 33g. ing.
[0018]
Next, another tool 1 is inserted into the main shaft 4, the taper surface 2 is brought into contact with the taper surface 5 of the main shaft 4, and an air cylinder (not shown) is operated in the direction opposite to the above. Then, the cylinder case 32 moves rightward together with the draw bar 9 by the spring 11. Since the tip of the collet 33 is in contact with the taper surface 32b of the cylinder case, the taper surface 33a, the taper surface 31b, and the rear end portion 33e are opposed to the disc spring 35 along with the movement of the taper surface 32b. And move in a direction approaching the axis while being in contact with the bottom surface 34c. Then, after the outer end of the tapered surface 33a becomes equal to the outer end of the tapered surface 31b, the collet 33 has a tapered surface against the disc spring 35 by the end of the hole 32a coming into contact with the tapered surface 33f. The tool 1 moves further along 31b, and the tapered surface 33c abuts against the tapered surface 3c of the pull stud, thereby biasing the tool 1 to the right. As a result, the tool 1 and the main shaft 4 are united by the frictional force between the tapered surface 2 and the tapered surface 5. When the tapered surface 33c comes into contact with the tapered surface 3c, a gap is formed between the surface 33d and the outer diameter of the flange portion 3a, and between the surface 33d and the side surface in the inner diameter direction of the guide groove 34a. It is configured.
[0019]
Next, functions will be described. When a pulling force greater than the force of the disc spring 11 is applied to the blade tip (not shown), the collet 33 tends to move in a direction away from the axis. However, since the force of the disc spring 11 is applied to the tapered surface 33f, for example, when the cotangent value of the angle a formed by the tapered surface 33f is 1/2 of the cotangent value of the angle b formed by the tapered surface 33c, the taper surface 33f is pulled out. The taper portion 2 and the taper portion 5 are not separated until the force becomes twice the force of the disc spring 11. Further, the collet 33 is positioned by being prevented from spreading outward by the cylinder case 32, and the pulling force from the tool 1 is, as shown in the loop R of FIG. 1, a pull stud 3, a tapered surface 3c, The taper surface 33c, the collet 33, the taper surface 33a, the taper surface 31b, the collet opener 31, the main shaft 4, the taper surfaces 5 and 2, and the tool 1 are closed loops, and the tool 1 is securely held by a mechanical lock.
[0020]
FIG. 5 compares the pulling force when the tool 1 is held in each of the tool holding device according to the present invention and the conventional tool holding device and the held tool 1 is urged in the pulling direction and the displacement amount of the tool 1. Is. As can be seen from the figure, in the case of the conventional tool holding device, when the pulling force exceeds 13 kN, the force for supporting the tool 1 depends on the tension force of the spring spring and the rigidity of the spring spring. Increase rapidly. On the other hand, in the case of the tool holding device according to the present invention, the amount of displacement is uniform and smaller than that of the conventional tool holding device. Since fretting is likely to occur when the amount of displacement is large, the fretting hardly occurs according to the tool holding device of the present invention.
[0021]
Instead of moving the collet 33 in the radial direction in parallel with the axial direction, the collet holder 34 is rotatably supported so that the V-shaped portion at the tip is opened in the radial direction while being supported by the collet holder 34. It may be configured to be engaged with both the surface 31b and the taper surface 3c by being moved to. Further, the collet opener 31 is not particularly provided, and the boss 31 a may be directly formed on the inner surface of the main shaft 4. The collet 33 is not limited to three divisions, and the number of divisions may be changed.
[0022]
【The invention's effect】
As described above, according to the present invention, even if a pulling force greater than the force of the disc spring that biases the draw bar is applied to the cutting edge, the taper surface of the tool and the taper surface of the spindle are not separated from each other. Even if the urging force remains the same, damage to the blade edge and fretting of the spindle and the taper portion of the tool can be prevented.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a main part of a spindle head of a machine tool in a state where a tool is held according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a main part of a spindle head of a machine tool in a state where a tool according to an embodiment of the present invention is not held.
FIG. 3 is an enlarged view of a main part showing an embodiment of the present invention.
FIG. 4 is a front view of a collet holder showing an embodiment of the present invention.
FIG. 5 is a diagram showing the change of the tool holder with respect to the tensile force between the conventional apparatus and the apparatus according to the present invention.
FIG. 6 is a sectional view of a spindle head of a machine tool in a state where a conventional tool is held.
FIG. 7 is a cross-sectional view of a spindle head of a machine tool in a state where a conventional tool is not held.
[Explanation of symbols]
1 Tool 2, 5 Tapered surface 3 Pull stud 3c Flange surface 4 Spindle 9 Draw bar 31 Boss (Collet opener)
31c Abutting portion 32 (positioning means) cylinder case 33 wedge member (collet)
33a 3rd taper surface 32b, 33f Joint part (contact part, 2nd taper surface)
33c First tapered surface 34 Collet holder 35 Belleville spring

Claims (1)

In a tool holding device for a machine tool, a wedge member disposed at a tip of a draw bar is engaged with a flange surface of a pull stud of a tool, and the draw bar is urged by a first urging means to hold the tool on the main shaft. ,
A positioning means is provided which is inserted into a guide hole formed in the main shaft so as to be axially movable and is integrally connected to the draw bar.
Between the second taper surface formed on the outer peripheral surface of the wedge member and the inner peripheral surface of the positioning means, a joint portion that abuts each other and performs a wedge action is provided,
In the state where the tool is held on the main shaft, the relative movement of the positioning means relative to the wedge member based on the bias of the first biasing means of the draw bar causes the inside of the wedge member based on the wedge action of the joint portion . The first taper surface formed on the peripheral surface is engaged with the flange surface, and the positioning means is positioned to prevent the wedge member from spreading ,
An angle with respect to the axis of the second tapered surface of the wedge member is set smaller than an angle with respect to the axis of the first tapered surface;
A third tapered surface is provided at the tip of the wedge member, a contact portion is provided integrally with the main shaft, and the third tapered surface of the wedge member is between the wedge member and the draw bar. Intervening second biasing means for biasing to contact the contact portion,
By moving the draw bar in the tool releasing direction, the wedge member is moved relative to the main shaft in the axial direction based on the bias of the second biasing means, and the third tapered surface and the contact portion The first tapered surface of the wedge member is moved so as to be released from the flange surface.
A tool holding device for a machine tool.

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