WO2018110681A1

WO2018110681A1 - Chatter-preventing structure for work machine

Info

Publication number: WO2018110681A1
Application number: PCT/JP2017/045005
Authority: WO
Inventors: 保宏駒井; 正樹中川
Original assignee: エヌティーエンジニアリング株式会社
Priority date: 2016-12-14
Filing date: 2017-12-08
Publication date: 2018-06-21
Also published as: JP7069540B2; JP2018094710A

Abstract

The present invention makes it possible to maintain the balance of a rotating body with high precision while the rotating body rotates at high speed. A chatter-preventing structure (10) includes a housing member (28) that is fixed, with respect to a tool holder (20), to the outer periphery of the rear end portion of a tool attachment part (24), and rotates together with the tool holder (20). An annular damper chamber (34) is formed within the housing member (28) and accommodates a divided ring-like friction damper part (36) in a manner that allows orbital movement thereof, said ring-like friction damper part (36) absorbing, by sliding friction, vibration energy that contributes to chatter during machining of a workpiece (W).

Description

Chatter prevention structure for work machines

The present invention relates to a chattering prevention structure for a work machine for preventing chattering when a workpiece is processed through a processing tool mounted on a rotating rotating body.

Generally, various machine tools are used to process a workpiece through a processing tool. A machine tool is usually incorporated in a work machine having a function and a mechanism for working in conjunction with the operation of the machine tool.

For example, in the boring process, a boring tool provided with a boring bar (cutting edge) is attached to a rotating spindle (spindle) of a machine tool, and the boring tool is sequentially fed out along a pilot hole while rotating the boring tool at a high speed. A highly accurate hole is processed at a predetermined position with a processing diameter.

Ordinarily, the boring bar is a so-called cantilever system, and is used for, for example, drilling a workpiece such as a connecting rod, so that it is relatively long and has a small diameter. This is because there is a concern about interference between the jig for clamping the workpiece to be machined and the shape of the machining hole. For this reason, the boring bar is likely to bend due to the cutting resistance, and chatter (including so-called regenerative chatter) appears.

Therefore, for example, a chattering prevention structure for a working machine disclosed in Patent Document 1 is known. The chattering prevention structure is fixed to the outer periphery of the rotating body, and is housed in a housing member that is rotated integrally with the rotating body, an annular damper chamber formed in the housing member, and is movably moved in the annular damper chamber. And a ring-shaped friction damper that absorbs vibrational energy that causes chatter during machining of the workpiece by sliding friction.

For this reason, when machining a workpiece with a machining tool, various vibrations including vibrations in the cutting direction can be reliably absorbed by the sliding friction of the friction damper, and chattering can be generated as much as possible with a simple configuration. It can be suppressed.

Japanese Patent Application Laid-Open No. 2014-91211

The present invention has been made in connection with this type of chattering prevention structure, and in particular, when a rotating body rotates at a high speed, the chattering of a work machine capable of maintaining the balance of the rotating body with high accuracy is provided. The purpose is to provide a structure.

The present invention relates to a chattering prevention structure for a working machine for preventing chattering when a workpiece is processed through a processing tool mounted on a rotating rotating body.

In this chattering prevention structure, the housing member rotated integrally with the rotating body, the annular damper chamber formed in the housing member, and accommodated in the annular damper chamber so as to be able to move around, and at the time of processing the workpiece And a split ring friction damper that absorbs vibration energy that causes chatter by sliding friction.

The ring-shaped friction damper portion is configured by dividing the ring body in the circumferential direction, and when a vibration occurs in the cutting direction of the processing tool, a plurality of ring body configurations that move in the opposite direction to the vibration due to inertial force And a magnet that is embedded in each piece of the ring body and that generates sliding friction with the inner wall of the housing member. The interval between the inner circumferential arc-shaped wall surface and the outer circumferential arc-shaped wall surface of each ring body constituting piece is set to a value smaller than the spacing between the inner circumferential wall surface and the outer circumferential wall surface constituting the annular damper chamber, and the annular damper The said outer peripheral wall surface of a chamber is arrange | positioned concentrically with the rotating shaft of a rotary body.

In this chattering prevention structure, the rotating body is preferably a tool holder to which a processing tool is attached or a main shaft to which the tool holder is fixed.

With the chattering prevention structure for a work machine according to the present invention, various vibrations including vibrations in the cutting direction are reliably caused by sliding friction of each ring body constituting piece constituting the ring-shaped friction damper when a workpiece is machined by a machining tool. Absorption can be absorbed, and chattering can be suppressed as much as possible with a simple configuration.

In addition, when each ring body component piece is urged (pressed) in the radial direction by centrifugal force, the outer circumferential arc-shaped wall surface of the ring body component piece is supported in contact with the outer circumferential wall surface of the annular damper chamber. In that case, the outer peripheral wall surface of the annular damper chamber is arranged concentrically with the rotating shaft of the rotating body. For this reason, the plurality of ring body constituent pieces are disposed concentrically with the rotating shaft of the rotating body as a whole, and it is possible to reliably prevent an imbalanced state from occurring in the ring-shaped friction damper portion. . Therefore, it is possible to avoid the imbalance state especially when the rotating body rotates at a high speed or when the mass of the ring-shaped friction damper portion increases.

It is principal part explanatory drawing of the machine tool in which the chatter prevention structure of the working machine which concerns on the 1st Embodiment of this invention is integrated. It is sectional explanatory drawing of the said chattering prevention structure. FIG. 3 is a cross-sectional view of the chatter preventing structure taken along line III-III in FIG. 2. It is a relationship diagram of vibration energy and dissipation energy. It is principal part explanatory drawing of the machine tool in which the chatter prevention structure of the working machine which concerns on the 2nd Embodiment of this invention is integrated.

As shown in FIG. 1, a chattering prevention structure 10 for a working machine according to a first embodiment of the present invention is incorporated in a machine tool 12. The machine tool 12 includes a spindle (main shaft) 18 that is rotatably provided in a machine spindle head 14 via a bearing 16 and a tool holder 20 that is detachable from the spindle 18. The work machine of the present application has a function and a mechanism in which a tool holder 20 mounted on a spindle 18 of a machine tool 12 works in conjunction with the operation of the machine tool 12.

A shank portion 22 connected to the spindle 18 is provided at one end of the tool holder 20, and a tool attachment portion (rotating body) 24 is provided at the other end of the tool holder 20. A tool, for example, a boring bar (processing tool) 26 is attached to the tip of the tool mounting portion 24.

The chattering prevention structure 10 includes a housing member 28 that is fixed to the outer periphery of the rear end portion of the tool attachment portion 24 with respect to the tool holder 20 and rotated integrally with the tool holder 20. The housing member 28 has a substantially ring shape, and a small-diameter portion 28s is provided at one end (for example, the tip) in the axial direction via a stepped portion. One or more screw holes 30 are formed in the small diameter portion 28s so as to penetrate in the radial direction. A set screw 32 screwed into the screw hole 30 is pressed against the outer peripheral surface of the tool mounting portion 24, whereby the housing member 28 is fixed to the outer periphery of the tool mounting portion 24.

As shown in FIG. 2, an annular damper chamber 34 is formed in the housing member 28. In the annular damper chamber 34, a split-type ring-shaped friction damper portion 36 that absorbs vibration energy that causes chatter during machining of the workpiece W by sliding friction is movable, that is, the outer periphery of the tool mounting portion 24. Is accommodated so as to be movable in a direction (arrow A direction).

As shown in FIG. 3, the ring-shaped friction damper portion 36 is configured by dividing the ring body in the circumferential direction. Specifically, when the ring-shaped friction damper portion 36 vibrates in the cutting direction of the boring bar 26, that is, in the twisting direction (rotating direction or counter-rotating direction) (arrow A direction) of the tool mounting portion 24. A plurality of, for example, six ring body constituting pieces 38 that move in the direction opposite to the vibration due to inertial force are provided.

Each ring body constituting piece 38 has the same shape, and is configured by dividing a single ring body by the same angular interval. In the state shown in FIG. 3 (a state where the ring body is moved outward by centrifugal force), the end faces 38f of the ring body constituting pieces 38 are arranged slightly apart from each other. Each ring body component piece 38 may have a different shape.

The interval t1 between the inner circumferential arc-shaped wall surface 38i and the outer circumferential arc-shaped wall surface 38o of each ring body constituting piece 38 is determined by the inner circumferential contact surface (inner circumferential wall surface) 40i and the outer circumferential contact surface (outer circumferential wall surface) constituting the annular damper chamber 34. It is set to a value smaller than the interval t2 with respect to 40o (t1 <t2). The outer peripheral contact surface 40 o of the annular damper chamber 34 is disposed concentrically with the rotation axis of the tool mounting portion 24. Each ring body constituting piece 38 is movable in the direction of circling along the outer periphery of the tool mounting portion 24 and in the radial direction of the tool mounting portion 24. As shown in FIG. 2, a cover ring member 41 having an L-shaped cross section is attached to the housing member 28 so as to cover the annular damper chamber 34.

Each ring body constituting piece 38 has one or a plurality of magnets 42 embedded therein. Each ring body constituting piece 38 has a second contact surface 38 a that generates sliding friction with the first contact surface (inner wall) 28 a of the housing member 28. The first contact surface 28a and the second contact surface 38a are attracted and contacted by the magnetic force of each magnet 42. The first contact surface 28a has a ring shape arranged concentrically with the rotation axis of the tool mounting portion 24, and is configured as a smooth surface for smoothly sliding the magnet 42 to the side. The second contact surface 38a is also preferably configured as a smooth surface.

The inner diameter dimension of the housing member 28 is set to a slightly larger diameter than the outer dimension of the tool mounting portion 24 to be mounted. Although due to a difference (gap) in dimensions between the inner diameter of the housing member 28 and the outer shape of the tool mounting portion 24, the use of a plurality of set screws 32 allows the tool mounting portion 24, which is a rotating shaft, to be It is preferable that the inner diameter portion of the housing member 28 is attached so as to have an equal distance.

The operation of the machine tool 12 to which the chattering prevention structure 10 according to the first embodiment configured as described above is applied will be described below.

As shown in FIG. 1, in the machine tool 12, the spindle 18 to which the tool holder 20 is attached is rotationally driven and is fed along the pilot hole Wa of the workpiece W. And the tool attachment part 24 moves relatively to the pilot hole Wa side of the workpiece W integrally with the tool holder 20. For this reason, a boring process is given to the inner wall surface which comprises the pilot hole Wa via the boring bar 26 with which the rotating tool attachment part 24 was mounted | worn.

In this case, in the chattering prevention structure 10, as shown in FIG. 3, when vibration in the cutting direction (arrow A direction), that is, vibration in the twisting direction (rotating direction or counter-rotating direction) of the tool mounting portion 24 occurs, Each ring body constituting piece 38 having a mass tends to move in the direction opposite to the vibration due to inertial force.

Here, if the vibration energy (amplitude) is small, the attracting force by each magnet 42 becomes larger than the inertial force of each ring body constituting piece 38, and the ring body constituting piece 38 moves in the same direction as the vibration. Become. That is, as shown in FIG. 4, it becomes a state below Xs point which is the range which does not slip.

On the other hand, when a vibration amplitude of a certain level or more is generated, the inertial force of each ring body constituting piece 38 is increased, and the ring body constituting piece 38 tries to move in the direction opposite to the acting vibration. That is, in FIG. 4, the state is at or above the point Xs. At that time, the second contact surface 38a of each ring member constituting piece 38 and the first contact surface 28a of the housing member 28 are attracted and contacted by the magnetic force of the magnet 42 provided on the ring member constituting piece 38 (FIG. 2).

Therefore, frictional sliding (sliding motion) occurs between the first contact surface 28a and the second contact surface 38a, and the kinetic energy is absorbed and dissipated. Specifically, it is converted into heat. Due to the effect of energy dissipation due to the sliding friction, the vibration amplitude does not increase any more, and consequently chatter vibration is suppressed (see FIG. 4).

Thereby, in the first embodiment, when the workpiece W is processed by the boring bar 26, various vibrations including vibrations in the cutting direction can be surely absorbed by the sliding friction of the ring-shaped friction damper portion 36. For this reason, it is possible to obtain an effect that chattering can be suppressed as much as possible with a simple configuration.

Further, centrifugal force acts on each ring body constituting piece 38 under the rotating action of the tool mounting portion 24. At that time, when the vibration in the rotational direction is a small state equal to or less than the Xs point, each ring body constituting piece 38 is concentrically brought into contact with the outer peripheral contact surface 40o of the annular damper chamber 34 by contacting the outer peripheral arcuate wall surface 38o. Is arranged.

Next, when the vibration in the rotational direction is in a large state equal to or higher than the Xs point, each ring body constituting piece 38 slides in the rotational direction by sliding friction, and in FIG. Try to move outward (radially outward). Accordingly, each ring body constituting piece 38 slides along the outer peripheral contact surface 40o in a state where the outer peripheral arcuate wall surface 38o is brought into pressure contact with the outer peripheral contact surface 40o of the annular damper chamber 34.

In this case, the outer peripheral contact surface 40o is disposed concentrically with the rotation axis of the tool mounting portion 24, and each ring body constituting piece 38 that is in pressure contact with the outer peripheral contact surface 40o is disposed concentrically as a whole. ing. Thereby, the ring-shaped friction damper part 36 will be arrange | positioned in the concentric position with the rotating shaft of the tool attachment part 24 as a whole, and it can prevent reliably that an imbalanced state generate | occur | produces. For this reason, in particular, even when the tool mounting portion 24 rotates at a high speed or when the mass of the ring-shaped friction damper portion 36 increases, it is possible to avoid the imbalance state. .

Moreover, as shown in FIG. 3, the ring-shaped friction damper portion 36 is configured by dividing the ring body in the circumferential direction. Therefore, the entire mass can be reduced as compared with the ring-shaped integrally molded product, and the effect as a friction damper can be obtained up to the high frequency vibration region.

In the first embodiment, the ring-shaped friction damper portion 36 constituting the chattering prevention structure 10 is fixed to the outer periphery of the rear end portion of the tool attachment portion 24 with respect to the tool holder 20, but is not limited thereto. Is not to be done. For example, the ring-shaped friction damper portion 36 may be fixed to the outer periphery of the distal end portion of the tool attachment portion 24.

Furthermore, in the ring-shaped friction damper portion 36, the housing member 28 is fixed to the outer peripheral surface of the tool attachment portion 24 by one or more set screws 32, but is not limited thereto. For example, a method of press-fitting the housing member 28 onto the outer peripheral surface of the tool attachment portion 24, a method of fixing with an adhesive, a method of attaching with a circlip (retaining ring), or a method of attaching with a wedge body can be employed.

FIG. 5 is an explanatory view of a main part of a machine tool 52 in which a chattering prevention structure 50 for a work machine according to a second embodiment of the present invention is incorporated. In addition, the same referential mark is attached | subjected to the component same as the chattering prevention structure 10 and machine tool 12 which concern on 1st Embodiment, and the detailed description is abbreviate | omitted.

The machine tool 52 includes a spindle (rotating body) 54. A front housing member 56a is fixed to a front end portion 54a on the large diameter side of the spindle 54, and a rear housing member 56b is fixed to a rear end portion 54b on the small diameter side. Is done. An annular damper chamber 34a is formed in the front housing member 56a, and an annular damper chamber 34b is formed in the rear housing member 56b. In each of the

annular damper chambers

34a and 34b, a split ring friction damper portion 36 is accommodated so as to be able to move around.

As described above, the chattering prevention structure 50 is directly attached to the spindle 54 of the machine tool 52. For this reason, the diameter of the rear housing member 56b, in particular, the diameter of the front housing member 56a is considerably large, and the mass of the ring-shaped friction damper portion 36 and the mass of each ring body component piece 38 are large. Therefore, when each ring body component piece 38 is in an eccentric state due to vibration in the rotational direction, the amount of imbalance due to the centrifugal force generated from the magnitude of the mass tends to increase.

In this case, in the second embodiment, as in the first embodiment, each ring body component piece 38 is moved forward in the radial direction of the tool mounting portion 24 by centrifugal force. The outer peripheral contact surfaces 40o of 56a and the rear housing member 56b are in pressure contact with each other and are arranged concentrically as a whole. Thereby, an imbalance state can be avoided, and it becomes possible to prevent the occurrence of imbalance particularly during high-speed rotation. For this reason, the effect as a friction damper can be acquired even in the high frequency vibration region.

Moreover, the front housing member 56 a and the rear housing member 56 b are fixed to the outer periphery of the spindle 54. Therefore, the spindle 54 can be miniaturized as much as possible, and the spindle 54 can be manufactured economically.

In the chattering prevention structure for a work machine according to the present invention, when each ring body component piece is urged (pressed) in the radial direction by centrifugal force, the outer circumferential arc-shaped wall surface of the ring body component piece becomes the outer circumference of the annular damper chamber. Abutted on and supported by the wall surface. In that case, the outer peripheral wall surface of the annular damper chamber is arranged concentrically with the rotating shaft of the rotating body. For this reason, the plurality of ring body constituent pieces are disposed concentrically with the rotating shaft of the rotating body as a whole, and it is possible to reliably prevent an imbalanced state from occurring in the ring-shaped friction damper portion. . Therefore, it is possible to avoid the imbalance state especially when the rotating body rotates at a high speed or when the mass of the ring-shaped friction damper portion increases.

DESCRIPTION OF

SYMBOLS

10, 50 ...

Chatter prevention structure

12, 52 ...

Machine tool

18, 54 ... Spindle 20 ... Tool holder 26 ... Boring bar 28 ...

Housing member

28a, 38a, 40i, 40o ... Contact surface 38i, 38o ... Wall surface 34 ... Annular damper chamber 36 ... Ring-shaped friction damper 38 ... Ring body component piece ring body 42 ... Magnet

Claims

A chattering prevention structure for a work machine for preventing chattering when processing a workpiece through a processing tool mounted on a rotating rotating body,
A housing member rotated integrally with the rotating body;
An annular damper chamber formed in the housing member;
A ring-type friction damper part of a split type that is accommodated in the annular damper chamber so as to be able to move around, and absorbs vibration energy that causes chatter during machining of the workpiece by sliding friction;
With
The ring-shaped friction damper portion is configured by dividing a ring body in a circumferential direction, and when a vibration is generated in the cutting direction of the processing tool, a plurality of rings that move in a direction opposite to the vibration due to an inertial force. A body composition piece;
Embedded in each ring body component piece, and a magnet for generating the sliding friction with the inner wall of the housing member;
Have
The interval between the inner circumferential arc-shaped wall surface and the outer circumferential arc-shaped wall surface of each ring body constituting piece is set to a value smaller than the spacing between the inner circumferential wall surface and the outer circumferential wall surface constituting the annular damper chamber, and the annular damper chamber A chattering prevention structure for a work machine, wherein the outer peripheral wall surface is arranged concentrically with a rotating shaft of the rotating body.
The chattering prevention structure according to claim 1, wherein the rotating body is a tool holder to which the processing tool is attached or a main shaft to which the tool holder is fixed.