JP3353951B2 - Machine tool diameter control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a machining diameter control device for a machine tool which variably controls a machining diameter by moving a cutting tool in a direction of a moving axis intersecting a rotation axis. To improve the structure of the link mechanism when moving the link mechanism.

[0002]

2. Description of the Related Art A machining diameter control device for a machine tool, for example, drives a cutting tool in a boring machine around a main shaft axis (rotation axis) and is capable of moving in a U-axis (moving axis) direction orthogonal to the rotation axis. This is a device that changes the processing diameter so that boring with different diameters can be performed by one blade. Conventionally, various structures have been proposed as mechanisms for changing the processing diameter.
There is one disclosed in Japanese Patent Application Laid-Open No. 5-205. This is achieved by arranging the blade at the tip of the main shaft so as to be movable in the radial direction, inserting a feed rod into the main shaft, providing a drive source for the feed rod separately from the main shaft drive source, and operating the feed rod. Is converted to the above-mentioned radial movement via a link mechanism and transmitted to the cutting tool.

[0003] The link mechanism portion of the machining diameter control device described in the above publication is configured as shown in FIG. In the figure, reference numeral 80 denotes a quill (tool attachment) attached to the tip of a spindle. On the base end side of the quill 80, a rod 81 having one end connected to the feed rod (not shown) is provided in the Z-axis direction. It is movably supported. One end of a link 83 is rotatably connected to the other end of the rod 81 protruding into the space 87 of the quill 80 via a pin 82.
The other end of the link 83 is rotatably connected to one end of a lever 84 via a pin 86. The lever 84 has an L-shape having a predetermined angle, and a curved portion thereof is rotatably supported via a hinge pin 85.
A spherical cam 84a formed at the other end of the quill 80 is slidably engaged with an engaging groove Ta of a cutting tool T supported movably in the radial direction at the tip of the quill 80.

In the above-described machining diameter control device, the linear motion of the feed rod and thus the rod 81 is once converted into the rotational motion of the lever 84, and the rocking motion of the cam 84a of the lever 84 causes the cutting tool T to linearly move in the radial direction.

[0005]

However, in the machining diameter control apparatus using the above-described conventional link mechanism, the axial movement amount of the feed rod, and hence the rod 81, and the radial movement amount of the cutting tool T have a simple proportional relationship. Rather, it is represented by a complex relational expression. Therefore, in order to move the cutting tool by a predetermined amount, a complicated calculation process is performed in the NC device according to the above relational expression.
There is a problem that it is necessary to control the operation of the feed rod. In addition, it is necessary to increase the rotation angle θ of the lever 84 for a workpiece having a large processing stroke, but when the rotation angle θ of the lever 84 is increased, the rotation angle amount of the lever 84 is constant with respect to the movement amount of the feed rod. Therefore, there is a problem that the feed accuracy varies and a processing error occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and can control the moving amount of the cutting tool without performing complicated arithmetic processing, and can feed even a workpiece having a large machining stroke. An object of the present invention is to provide a machine tool diameter control device capable of performing high-accuracy machining without variation in accuracy.

[0007]

According to a first aspect of the present invention, a cutting tool is provided so as to be rotatable around a rotation axis and to be movable in a direction of a movement axis intersecting the rotation axis. In a machining diameter control device for a machine tool in which a machining diameter is variably controlled by moving the cutting tool in the moving axis direction, a shaft feed member is disposed movably in the rotation axis direction, and the cutting tool is fixed. The movable slider is disposed so as to be movable in the direction of the movement axis, the first connection point of the first link is rotatably connected to the shaft feed member, and the second connection point of the first link is connected to the intermediate link. The intermediate link is rotatably connected to a second connection point, and the intermediate link is pivotally supported at a shaft fulcrum located at the intersection of a straight line parallel to the rotation axis and a straight line parallel to the movement axis. The connection point is rotatably connected to the third connection point of the second link, The fourth connection point of the second link is rotatably connected to the slider, and the first triangle formed by the first and second connection points and the fulcrum, the fourth triangle and the third connection point, and the fulcrum of the fulcrum. A feature is that the second triangle to be formed has a congruent shape or a similar shape.

[0008]

In the machine tool diameter control device according to the present invention,
When the shaft feed member is moved in the direction of the rotation axis, the first connection point of the first link moves in the direction of the rotation axis.
The link rotates the intermediate link about the pivot, and the rotation of the intermediate link causes the fourth connection point of the second link to move in the direction of the movement axis, and as a result, the slider and, consequently, the cutting tool to move in the direction of the movement axis. In this case, since the first triangle formed by the first and second connection points and the fulcrum and the second triangle formed by the fourth and third connection points and the fulcrum are congruent or similar,
The movement amount of the first connection point and the movement amount of the fourth connection point are the same or a simple proportional amount according to the similarity ratio.

As described above, in the present invention, the relationship between the input movement amount and the output movement amount is the same or a simple proportional amount.
In controlling the amount of movement of the cutting tool, complicated calculations as in the related art are unnecessary, and even in the case of a work having a large processing stroke, there is no variation in feed accuracy, and high-precision processing can be performed.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIGS. 1 to 5 are views for explaining a machine diameter control apparatus for a machine tool according to a first embodiment of the present invention.
FIG. 1 is a sectional front view of the tool attachment, and FIG.
FIG. 3 is a sectional view taken along line II-II of FIG. 3, FIG. 3 is a sectional view taken along line III-III of FIG. 2, FIG. 4 is a partial sectional front view of a spindle ram provided with the tool attachment, and FIG.

In FIG. 1, reference numeral 1 denotes a spindle ram. The spindle ram 1 comprises a cylindrical ram body 2, a rotary drive motor 3 arranged and fixed coaxially in the ram body 2, A main shaft 5 that is inserted into the output shaft 4 of the drive motor 3 so as to rotate with the output shaft 4 and is movable in the axial direction, and a shaft that is attached to the ram body 2 and moves the main shaft 5 in the axial direction. A feed mechanism 6 and an engagement / disengagement mechanism 7 for locking / unlocking a shaft feed rod 40 of a tool attachment 8 described later on the main shaft 5 are provided. The tool attachment 8 is detachably attached to the lower end of the ram body 2. The shaft feed mechanism 6 and the engagement / disengagement mechanism 7 constitute a drive source of the machining diameter control device of the present embodiment.

The rotary drive motor 3 is connected to the ram body 2
The output shaft 4 is rotatably arranged via a bearing 10 in a motor case 9 fixed to the inner surface of the motor shaft, and the rotor 11 is fixed to the output shaft 4 and is arranged to face the periphery of the rotor 11. The stator 12 is fixed to the inner surface of the motor case 9.

The shaft feed mechanism 6 has a rotary cylinder 14 rotatably disposed at the upper end of the ram main body 2 via a bearing 13, and connects the rotary cylinder 14 and the shaft feed motor 15 to a pulley 16 a and a belt. 17, connected via pulley 16b,
A shaft feed screw 19 is screwed into a feed nut 18 provided in the rotary cylinder 14, and a shaft feed cylinder 20 is connected and fixed to the lower end of the shaft feed screw 19 so as to be coaxial. The shaft feed tube 20 is axially movably and non-rotatably inserted into a guide tube portion 9 a formed in the motor case 9. The shaft feed tube 20 has a bearing 21 at the upper end of the main shaft 5. Are coaxially connected so as to be relatively rotatable and move together in the axial direction. With this configuration, when the rotary tube 14 is rotated by the shaft feed motor 15, the shaft feed screw 19 moves in the axial direction, and the axial movement is transmitted to the main shaft 5 via the shaft feed tube 20.

The engagement / disengagement mechanism 7 fixes the cylinder 25 to the upper end of the shaft feed screw 19 and
Piston 26 formed at the upper end of engaging rod 26 within 5
a is inserted and arranged, and the engaging / disengaging rod 26 is configured to face and abut on the draw bar 27 inserted into the main shaft 5. The draw bar 27 is provided with the main shaft 5.
The collet 29 is extended to the vicinity of the lower end of the draw bar 27 and is urged upward in the figure by a disc spring 28 so that the collet 29 locked at the lower end of the draw bar 27 is engaged and disengaged with a shaft feed rod 40 described later.

An attachment / detachment mechanism 2 for attaching / detaching the tool attachment 8 to / from the ram main body 2 is provided on the lower inner surface of the ram main body 2.
2 are provided. The attachment / detachment mechanism 22 includes the ram body 2
The piston 23 is inserted and disposed in the cylinder portion 2a formed on the inner surface of the collet 24 so as to be movable in the axial direction, and the collet 24 is moved in the axial direction by the piston 23 so as to be detached.

The tool attachment 8 constitutes an operating part of the machining diameter control device of the present embodiment, and the ram body 2
An attachment case 30 which is detachably attached to the lower part of the case and is pivotally indexable, and a bearing 31 is provided in the case 30.
a drive shaft 31 inserted rotatably and immovably in the axial direction, a guide block 32 fixed to the lower end of the drive shaft 31, and a rotation coaxial with the main shaft axis by the guide block 32. The axis of movement (U
The slider 33 supported movably in the (axial) direction, the holder 34 detachably attached to the slider 33, and the axial movement of the main shaft 5 are replaced with the movement in the movement axis direction (arrows J and K directions). And a link mechanism 35 for converting and transmitting the converted light to the slider 33.

The attachment case 30 is a cylindrical body having a locking step 30a formed at the upper end, and the locking step 30a is pulled up in the axial direction by the collet 24 of the attachment / detachment mechanism 22. A turning index coupling 36a for setting an angular position of the attachment case 30 around the rotation axis CT is mounted on the outer periphery of the attachment case 30, and is mounted on a lower portion of the inner surface of the ram main body 2. At a predetermined angular position.

The drive shaft 31 has a cylindrical shape, and has a slide tooth 3 on its upper end inner surface which is axially movable on the lower end outer surface of the main shaft 5 and meshes with the main shaft 5 so as to rotate therewith.
1b is formed. The guide block 32 fixedly connected to the lower end surface of the drive shaft 31 has a substantially rectangular parallelepiped shape, and has a pair of side guide grooves 32a on both outer surfaces.
In addition, a bottom surface guide groove 32b is formed on the bottom surface thereof so as to extend in a direction perpendicular to the rotation axis CT, and a pair of inner surface guide grooves 32c is formed on both inner side surfaces of the bottom surface guide groove 32b. It is recessed in parallel with the side guide groove 32a. The inner surface guide groove 32c is opposed to the side surface guide groove 32a via a partition 32d, and a pinion gear 37a is rotatably disposed on the partition 32d by a pin 37b.

A balancer 38 is provided in each side guide groove 32a of the guide block 32 in the vertical direction in FIG.
It is slidably disposed in the directions of arrows J and K). Each of the balancers 38 has a square rod shape, and has rack teeth 38a formed on the inner surface thereof, and the rack teeth 38a mesh with the pinion gear 37a.

In the bottom guide groove 32b of the guide block 32, the slider 33 is disposed with its bottom protruding downward. The slider 33 has a rectangular parallelepiped box shape with an open top, and has a pair of sliding pieces 33a formed on the left and right sides thereof. Further, rack teeth 33b are formed on the outer surface of each sliding piece 33a, and the rack teeth 33b mesh with the left and right pinion gears 37a. With this configuration, the slider 33
Is slid in one direction, each balancer 38 slides in the opposite direction, and the center of gravity substantially coincides with the rotation axis CT even when the slider 33 moves.

A boss 33c for mounting the holder 34 protrudes from the bottom surface of the slider 33. A mounting screw is formed on the outer periphery of the boss 33c, and a tapered convex portion for positioning is formed on the bottom surface. I have. The tapered concave portion of the holder 34 fits into the tapered convex portion, and is fastened and fixed with a mounting nut 39, and the cutting tool T is fixed to the holder 34.

A shaft feed rod 40 is inserted into the drive shaft 31 so as to be movable in the axial direction. The upper end of the shaft feed rod 40 is formed with a tapered portion 40a that fits into a tapered hole formed at the lower end of the main shaft 5, and the lower end is a boss to which the link mechanism 35 is connected. 4
0b is formed.

The link mechanism 35 rotatably connects the upper end (first connection point) of the strip-shaped first link 41 to the boss 40b of the shaft feed rod 40 with a first connection pin A.
A lower end portion (second connection point) of the first link 41 is connected to one end of a triangular plate-shaped intermediate link 43 by a second connection pin B, and a corner portion (a shaft fulcrum) of the intermediate link 43 is connected to a shaft support pin C. And is rotatably supported by the support boss portion 32e of the guide block 32 via the third link pin D to the other end of the intermediate link 43 to the right end (third connection point) of the second link 44. The left end (fourth connection point) of the second link 44 is
The slider 33 is connected to the inner surface of the slider 33 by a connecting pin E. The first to fourth connection pins A,
Although not shown, B, D, E, and the support pin C have a structure in which a ball bearing is fitted to the pin and a backlash is applied by applying excess pressure.

Here, the vertical axis formed by the first connecting pin A and the pivot pin C is parallel to the rotation axis CT, and the first connecting pin A moves on the vertical axis. The horizontal axis formed by the shaft support pin C and the fourth connection pin E is the rotation axis CT.
And the fourth connecting pin E moves on the horizontal axis.

The distance L1 between the first and second connecting pins A and B of the first link 41 is the same as the distance L1 'between the fourth and third connecting pins E and D of the second link 44. The dimension L2 between the second connecting pin B and the supporting pin C of the intermediate link 43 is the same as the dimension L2 'between the third connecting pin D and the supporting pin C,
The angle formed by the second connecting pin B, the pivot pin C, and the third connecting pin D is set to 90 degrees, which is the same as the angle formed by the vertical axis and the horizontal axis. As a result, the first triangle formed by the first and second connection pins A and B and the support pin C and the second triangle formed by the fourth and third connection pins E and D and the support pin C are congruent, Therefore, the dimension L3 between the first connecting pin A and the pivot pin C is equal to the dimension L3 'between the fourth connecting pin E and the pivot pin C. The first and second triangles correspond to the first and fourth connecting pins A,
Regardless of the movement of E, the above-mentioned joint relationship is always maintained.

Next, the operation and effect of this embodiment will be described.
In the present embodiment, when the main shaft 5 is driven to rotate by the rotary drive motor 3, the drive shaft 31 of the tool attachment 8 is driven to rotate by the main shaft 5, so that the cutting tool T is rotated together with the guide block 32 and the slider 33 by the rotation shaft CT. Rotate around. In order to change the rotation diameter (working diameter) of the cutting tool T, the rotary cylinder 14 is driven to rotate by the shaft feed motor 15 and the main shaft 5 is moved in the rotation axis direction by the shaft feed screw 19. For example, when the main shaft 5 is lowered, the shaft feed rod 40
Lowers the first link 41, and accordingly, the intermediate link 43 rotates clockwise in FIG.
The link 44 is moved rightward in FIG. This second link 4
By the movement of 4, the slider 33 and, consequently, the cutting tool T move in the direction of arrow K, and the processing diameter changes.

In the operation of the link mechanism 35, FIG.
As shown in the figure, for example, the first connecting pin A of the first link 41
Is lowered by ΔL, the first and second connecting pins A,
B, a first triangle A′B′C formed by the pivot pin C,
A second triangle E 'formed by the third connection pins E and D and the pivot support pin C
Since D'C is congruent, U at the fourth connection point E
The axial movement amount ΔL ′ is equal to the above ΔL. Accordingly, the amount of movement in the Z-axis direction by the shaft feed screw 19 and the amount of movement of the cutting tool in the U-axis direction are the same, and control of the processing diameter is extremely easy.

In the apparatus of this embodiment, when the slider 33 moves, the rack teeth 33b of the slider 33 rotate the pinion gear 37a, and the pinion gear 37a moves the balancer 38 in the opposite direction to the slider 33. As a result, the balancer 38 is displaced to the opposite side to the slider 33 in accordance with the amount of displacement of the slider 33 from the rotation axis CT, and as a result, the center of gravity of the entire tool attachment substantially coincides with the rotation axis CT. The balance of time is taken, and high-speed rotation becomes possible.

In the first embodiment, the Z axis (the blade rotating axis)
The case has been described in which the right angle is formed between the U-axis and the U-axis (the blade moving axis), but the present invention can be applied to cases other than the right angle. FIG. 6 shows Z
A second embodiment in which the axis and the U axis form 120 degrees is shown.
In the second embodiment, the angle formed by the second linking pin B, the pivot pin C, and the third linking pin D of the intermediate link 43 is Z.
It is formed so as to be 120 degrees which is the same as the angle between the axis and the U axis. As a result, the first triangle ABC and the second triangle EDC are congruent as in the case of FIG. 5, and the amount of input movement of the first link 41 to the first connecting pin A and the second link 4
4 is equal to the output movement amount from the fourth connecting pin E,
The same effect as in the first embodiment can be obtained.

In the first and second embodiments, the case where the rotation axis of the cutting tool is coaxial with the main axis is described. However, the present invention can be applied to the case where the rotation axis of the cutting tool is not coaxial with the main axis. FIG. 7 shows a third embodiment of the present invention in which the axis of rotation of the cutting tool is perpendicular to the axis of the main axis, and the tool is moved in a direction parallel to the axis of the main axis. The same reference numerals indicate the same or corresponding parts.

The attachment case 52 of the tool attachment 51 of this embodiment is an L-shaped cylindrical body, and a first drive shaft 53 coaxial with the first rotation axis CT1 and the second drive shaft 53 in the attachment case 52. A second drive shaft 54 coaxial with a second rotation axis CT2 orthogonal to the one rotation axis CT1 is rotatably disposed via a bearing 31a. The first and second drive shafts 53 and 54 are connected by bevel gears 55a and 55b, whereby the first rotary shaft C of the main shaft is formed.
Due to the rotation around T1, the cutting tool T rotates around the second rotation axis CT2.

In the present embodiment, a first link mechanism 56 for converting the operation of the spindle in the direction of the first rotation axis CT1 to the direction of the second rotation axis CT2, and the first link mechanism 56 in the direction of the second rotation axis CT2. And a second link mechanism 57 that converts the above operation into the direction of the movement axis (the directions of the arrows L and M) orthogonal to the second rotation axis CT2.

The first and second link mechanisms 56 and 57 are
The configuration is basically the same as that of the link mechanism 35 in the first embodiment. That is, in the first link mechanism 56, the first and fourth connection pins A1 and E1 move on the vertical and horizontal axes parallel and perpendicular to the first and second rotation axes CT1 and CT2, respectively. C1 is located at the intersection of the vertical and horizontal axes, and the first triangle formed by the first and second connection pins A1, B1 and the support pin C1 is the fourth triangle of the fourth and third connection pins E1, D1, and the support pin C1. It is congruent with the second triangle to be formed.

In the second link mechanism 57, the first
The connection pin A2 moves on a horizontal axis parallel to the second rotation axis CT2, the fourth connection pin E2 moves on a movement axis perpendicular to the second rotation axis CT2, and the pivot pin C2 moves between the movement axis and the movement axis. It is located at the intersection with the horizontal axis, and the first and second connecting pins A
2, B2, and the first triangle formed by the pivot support pin C2 are fourth and third triangles.
This is the same as the second triangle formed by the connection pins E2, D2 and the pivot support pin C2.

The first link 41 of the first link mechanism 56 is rotatably connected via a first connecting pin A1 to a connecting member 59 rotatably supported on the first shaft feed rod 40 via a bearing 58a. Are linked. The second link 44 is rotatably connected to a connecting member 61 rotatably supported by a second shaft feed rod 60 via a bearing 58b via a fourth connecting pin E1.

In the apparatus of the third embodiment, when the main shaft rotates around the first rotation axis CT1, this rotation is performed by the first drive shaft 53,
The bevel gears 55a and 55b and the second drive shaft 54 transmit the power to the guide block 32, and thus to the cutting tool T.
It rotates around the rotation axis CT2. As a result, boring is performed.

In order to change the processing radius of the cutting tool T, the spindle is lowered. Then, the first link 41 of the first link mechanism 56 descends due to this lowering, and the intermediate link 43
Is rotated clockwise, and the intermediate link 43 moves the second link 44 rightward in the horizontal axis direction by the same amount as the amount of movement of the main shaft. Due to the movement of the second link 44, the first link 41 of the second link mechanism 57 moves rightward in the horizontal axis direction and rotates the intermediate link 43 counterclockwise. Is moved in the direction of arrow L by the same amount as the first link 41. As a result, the blade T moves in the direction of the arrow L by the same amount as the amount of movement of the main shaft in the vertical axis direction.

Although the third embodiment has described the case where the cutting tool rotation axis is at 90 degrees with respect to the main axis, the present invention is also applicable to a tool attachment having an arbitrary angle. This can be realized by applying the second embodiment to the first link mechanism of the third embodiment.

In the first to third embodiments, the length between the pins A and B of the first link 41 and the pins D to
E and the intermediate link 43
The length between B and C and the length between D and C are the same, and the angle between the two sides of the intermediate link 43 is set to be the same as the angle between the rotation axis and the movement axis. By making the triangles formed by the support pins congruent, the amount of input movement and the amount of output movement are the same, but in the present invention, the two triangles can be set to similar shapes. For example, the first
By setting the ratio of the length between A and B of the link to the length between D and E of the second link, and the length ratio between the first side and the second side of the intermediate link to 1: n, output movement is performed. The amount can be n times the input movement amount.

In this case, if n is set to be larger than 1, the amount of movement of the cutting tool can be increased as compared with the amount of movement of the main shaft. In such a case, the spindle feed mechanism of the main shaft can be made compact. Conversely, if n is set to be smaller than 1, the amount of movement of the cutting tool can be made smaller than the amount of movement of the main spindle. Since the machining error amount can be reduced, and the boosting action works, the cutting tool can be moved with a small driving force, and the driving source can be made compact.

[0041]

As described above, according to the machining diameter control apparatus for a machine tool according to the present invention, the shaft feed member and the slider of the cutting tool are connected by the first link, the intermediate link, and the second link. Since the first triangle composed of the first, second and third connection points and the pivot point and the second triangle composed of the fourth and third connection points and the pivot point are set to be congruent or similar, The amount of movement of the first connection point in the direction of the rotation axis and the amount of movement of the fourth connection point in the direction of the movement axis are the same or simply proportional in proportion to the similarity ratio. There is an effect that calculation can be made unnecessary, and even in the case of a work having a large processing stroke, there is no variation in feed accuracy, and there is an effect that high-precision processing is possible.

[Brief description of the drawings]

FIG. 1 is a sectional front view of a tool attachment for describing a machine diameter control device for a machine tool according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a sectional view taken along line III-III of FIG. 2;

FIG. 4 is a partial sectional front view of a spindle ram provided with the tool attachment.

FIG. 5 is a schematic diagram of a link mechanism for explaining the operation of the first embodiment.

FIG. 6 is a schematic view of a link mechanism of a machining diameter control device according to a second embodiment of the present invention.

FIG. 7 is a sectional front view of a tool attachment of a machining diameter control device according to a third embodiment of the present invention.

FIG. 8 is a schematic view of a link mechanism of a conventional processing diameter control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Spindle ram (machine tool) 2 Ram body (device fixing part) 34 Holder 40 Shaft feed rod (shaft feed member) 41 1st link 43 Intermediate link 44 2nd link A, A2 1st connection pin (1st connection point) B, B2 Second connection pin (second connection point) C, C2 Axle support pin (axis support point) D, D2 Third connection pin (third connection point) E, E2 Fourth connection pin (fourth connection point) ABC First triangle EDC Second triangle CT, CT2 Rotation axis T Cutting tool

Claims (1)

(57) [Claims] 1. A cutting tool is provided so as to be rotatable around a rotation axis and movably in a moving axis direction intersecting with the rotation axis, and the cutting tool is moved in the moving axis direction by the input operation in the rotation axis direction. In the machining diameter control device for a machine tool in which the machining diameter is variably controlled by, a shaft feed member is disposed so as to be movable in the rotation axis direction, and the slider to which the cutting tool is fixed is movable in the movement axis direction. And a first connection point of a first link is rotatably connected to the shaft feed member, and a second connection point of the first link is rotatably connected to a second connection point of the intermediate link. The intermediate link is flat on the rotation axis .
And supported by a shaft supporting point located at the intersection of the straight line parallel to the rows linearly with the moving shaft, and connecting the third coupling point of the intermediate link rotatably third connecting point of the second link, the The fourth connection point of the second link is rotatably connected to the slider, and the first triangle formed by the first and second connection points and the fulcrum, the fourth triangle and the third connection point, and the fulcrum of the fulcrum. A machining diameter control device for a machine tool, wherein a second triangle to be formed has a congruent shape or a similar shape.