JPH02205405A - Clamping device for tool - Google Patents

Abstract

PURPOSE:To maintain tool clamping force during high speed rotation of a main shaft with a simple structure by matching a movable member fitted to the outer periphery of a shifter to the rotating speed of the main shaft by a balancer, and pushing it toward the end of the main shaft to press a disc spring. CONSTITUTION:Mounting load is applied to disc spring 9 by adjusting the axial position of a shifter 13, tension is applied to a draw bar 12 and a tool 6 is fitted into the tape hole 7 of a main shaft 2. When the rotating speed of the main shaft is increased, the disc spring 9 is expanded radially, so that the axial cumulative length of the disc spring 9 is shortened to produce a clearance toward the shifter 13. At this time, a movable member 17 fitted to the outer periphery of the shifter 13 is pushed in the direction of the end of the main shaft 2 by a balancer 15 moving in accordance with the rotating speed thereof and the disc spring 9 is pressed. Accordingly, the resiliency of the disc spring 9 acts on the shifter 13 and the tension is applied to the draw bar 12, thereby clamping force being maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tool clamping device for clamping a tool to the tip of a main shaft of a cutting machine or the like.

[Prior Art] In a conventional tool clamping device, a pull stud provided at the rear end of a tool is grasped by a collet provided at the tip of a drawbar, and the drawbar is moved in the tool clamping direction, that is, backward, by the elastic force of a disc spring. By being pulled in the direction, the taper part of the tool fits into the taper hole of the spindle,
It is used to clamp tools.

However, when unclamping the tool, it is necessary to move the drawbar several millimeters in the forward direction, so it is necessary to set a large number of disc springs to provide a large amount of deflection. Therefore, when rotating at high speed, the disc spring expands in the radial direction due to centrifugal force, so the elastic force of the disc spring applied to the disc spring stop becomes weaker, and the tensile force applied to the drawbar becomes weaker.

Furthermore, as the rotational speed of the spindle increases, the cumulative clearance in the axial direction caused by the radial expansion of the disc spring shifts the position of the disc spring, disrupting the rotational balance and increasing rotational vibration, which has a negative impact on machining accuracy. There were cases where it caused

Therefore, Japanese Patent Application Laid-Open No. 62-255038 proposes a tool clamping device that reduces rotational vibration by reducing the displacement of a disc spring when the main shaft rotates at high speed.

This tool clamping device is provided with a coned disc spring elastic force interrupter that intermittently applies the elastic force of the disc spring to the drawbar, a first pushing device that compresses the disc spring with a small stroke, and a drawbar. A second pushing device is provided for moving the tool forward to the tool unclamping position.

[Problem to be solved by the invention] However, the tool clamp device disclosed in the above publication has the following problems:
In addition to the disc spring that applies a strong tensile force to the drawbar, a coil spring that always applies a weak tensile force to the drawbar is provided, and the above-mentioned disc spring elastic force intermittent mechanism, the first pushing device, and Each of the second pushing devices is composed of a plurality of parts.

Therefore, since the number of parts of the device increases and the structure is complicated, assembly is difficult, the device becomes large, and the cost increases.

The present invention was made based on the above circumstances, and its purpose is to reduce rotational vibration with a small number of parts and a simple structure, and to ensure tool clamping force when the spindle rotates at high speed. An object of the present invention is to provide a tool clamping device.

[Means for Solving the Problems] In order to achieve the above object, the present invention is provided with a rotatable shaft which is rotatably held, has a tapered hole formed at its tip, and has a shaft hole communicated with the tapered hole formed in the axial direction. a cylindrical main shaft, a drawbar that is inserted into the shaft hole and moves forward and backward in the axial direction to unclamp and clamp the tool inserted into the tapered hole; a shifter whose axial position is adjustable relative to the drawbar; and a retraction that is fitted to the outer periphery of the drawbar within the shaft hole and clamps the tool relative to the drawbar by applying a mounting load by the shifter. a plurality of disc springs that apply a tensile force in the direction; a movable member that is fitted onto the outer periphery of the shifter and is slidable in the axial direction with respect to the shifter and the shaft hole; and a balancer that is attached to the main shaft and pushes the movable member toward the distal end of the main shaft and suppresses the disc spring when the main shaft rotates, thereby applying a force to the shifter in a direction in which the main shaft retreats. Adopt it as a technical means.

[Function] The tool clamping device of the present invention having the above configuration adjusts the axial position of the chic and applies a mounting load to the disc spring, thereby applying tensile force to the drawbar and retracting the tool. It is fitted into a tapered hole and clamped.

Thereafter, as the rotational speed of the main shaft increases, each disc spring expands in the radial direction, so that the cumulative length of the disc springs in the axial direction becomes shorter, creating a cumulative clearance between the disc springs and the shifter.

At this time, the movable member fitted around the outer periphery of the shifter
It is pushed toward the tip of the main shaft by the balancer, and presses the disc spring with a pressing force that corresponds to the rotational speed of the main shaft.

As a result, as the rotational speed of the main shaft increases, even if a cumulative clearance in the axial direction occurs between the chic and the disc spring, the elastic force of the disc spring acts on the shifter via the movable member. In other words, the reaction force of the pressing force on the movable member by the balancer acts on the shaft and the lid in the backward direction of the spindle, so the direction in which the tool is clamped to the drawbar (toward the rear end of the spindle)
A tensile force can be applied to.

[Effects of the Invention] According to the present invention, the action of the movable member and the balancer makes it possible to obtain a force that presses the shifter in the main shaft backward direction even when the main shaft rotates at high speed, so that no tensile force is applied to the drawbar. It is possible to secure the tool clamping force.

Further, since the disc spring is pressed by the movable member, it is possible to prevent rotational balance of the disc spring from being lost and to reduce rotational vibration.

As a result, the tool clamping device of the present invention is smaller, has fewer parts, has a simpler structure, and can reduce the cost of the device compared to conventional tool clamping devices.

[Example] Next, a tool clamping device of the present invention will be described based on an example shown in the drawings.

1 is a sectional view of the tool clamping device, FIG. 2 is an explanatory view of the operation of the main part of FIG. 1, and FIG. 3 is a view from A in FIG. 1.

The tool clamp device I11 of this embodiment is configured so that the rotational output of a motor (not shown) serving as a power source is connected to a power transmission component (for example, a pulley) fixed to the outer periphery of the rear end portion (right side in FIG. 1) of the main shaft 2. gear, etc.) 3 to the main shaft 2.

The main shaft 2 is rotatably held in a housing 5 via a bearing 4, and has a tapered hole 7 formed at its tip (left side in figure fJ1) into which a tapered part 6a of a tool 6 to be clamped is fitted, A shaft hole 8 communicating with the tapered hole 7 is formed in a cylindrical shape.

A portion of the shaft hole 8 on the tapered hole 7 side is formed to have a slightly smaller diameter, and therefore, a step 8a is formed on the inner peripheral surface of the shaft hole 8 over the entire circumference.

A holder 10, which also serves as a valve holder for a disc spring 9, which will be described later, is fitted into the tip side of the shaft hole 8. This holder 10 has a cylindrical shape with only the tip side open, and is fitted into the shaft hole 8 to a position where the open end abuts a step 8a formed on the inner peripheral surface of the shaft hole 8.

A drawbar 12 for clamping the tool 6 via a collet 11, which will be described later, is inserted into the shaft hole 8.

The tip of the drawbar 12 penetrates the center of the rear end side wall surface of the holder 10, reaches the inside of the holder 10, and is inserted into the holder 10 for gripping the pull stud 6b provided at the rear end of the tool 6. It is coupled to the collet 11.

The collet 11 is formed with a plurality of elastic walls 11a that can be elastically deformed in the radial direction, and an engaging portion 11b for engaging with the pull stud 6b is provided at the tip of the elastic wall 11a. In the holder 10, the collet 11 is inserted into the engaging portion 11 of the collet 11 while gripping the pull stud 6b.
b is in contact with the inner circumferential surface of the holder 10, and the engaging portion 11b
cannot expand outward, so the pull stud 6b will not come off from the engaging portion 11b.

When removing the pull stud 6b from the engaging part 11b, the collet 11 is moved forward together with the drawbar 12 toward the distal end of the main shaft 2 to a position where the engaging part 11b can expand outward. , when the holder 10 is fitted into the shaft hole 8, the shaft hole 8 formed with a small diameter on the tapered hole 7 side
The diameter of the shaft hole 8 or the wall thickness of the holder 10 is set so that the diameter of the shaft hole 8 is slightly larger than the inner diameter of the holder 10. Therefore, the engaging portion 11b of the collet 11 is
By moving forward from the open end of G toward the tapered hole 7 side, the engaging portion 11b expands outward, and the pull stud 6b can be removed.

The drawbar 12 is attached to the outer periphery of the drawbar 12 in the shaft hole 8.
A plurality of disc springs 9 are fitted to apply a tensile force to the
A mounting load is applied to the disc spring 9 by a shifter 13 fixed to a disc spring attached to the rear end of the drawbar 12.

The shifter 13 is fitted around the outer periphery of the drawbar 12 in such a way as to cover the open end on the rear end side of the main shaft 2, and a nut 14 screwed onto the drawbar 12 is attached to the rear end of the shifter 13.
The axial position is adjusted by.

As shown in FIG. 2, this shifter 13 is provided with a balancer attachment part 13b on the rear end side of a cylindrical part 13a inserted into the shaft hole 8, to which a balancer 15, which will be described later, is attached.

As shown in FIG. 3, three balancer attachment parts 13b are newly formed at equal intervals on the circumference, and in the circumferential center of each balancer attachment part 13b, there are
A groove 16 of a constant width is formed.

A cylindrical movable member 17 is fitted onto the outer periphery of the cylindrical portion 13a of the shifter 13, and is slidably provided in the cylindrical portion 13a and the shaft hole 8.

Groove 16 of balancer mounting part 13b provided in shifter 13
A balancer 15 having a substantially doglegged shape is assembled therein, and is rotatably provided within the groove 16 using a bin 18 attached in the width direction of the groove 16 as a fulcrum.

This balancer 15 has the following: Distance from the bottle 18 to one end (point B on the right side in Figure 2): jll, Distance from the bottle 18 to the other end (point B on the right side in Figure 2) +N2, Mass at point B: ml, and the mass of point C is 2 m2, then rnl ・11 < m2 ・! It is provided so that the relationship J2 holds true.

Also, the position of the bin 18 installed in the groove 16 is
The distance from the rear end surface of the movable member 17 (the right end surface in FIG. 2) to the bin 18 is set to be shorter than the distance from point 8 to point B.

Therefore, in this balancer 15, when comparing the magnitude of the rotational moment acting on point B and point 0 around the bin 18 due to the rotation of the main shaft 2, in FIG.
For example, the counterclockwise rotational moment at point 0 is greater than the clockwise rotational moment acting on point B. As a result, when the main shaft 2 rotates at high speed, the balancer 15
In FIG. 2, a counterclockwise rotational force acts around the bottle 18, and pushes the movable member 17 toward the tip of the main shaft 2 with point B as the point of action.

On the other hand, when the movable member 17 pushed out toward the tip of the main shaft 2 by the balancer 15 presses the disc spring 9,
The reaction force is transmitted to the shifter 13 via the balancer 15 and presses the shifter 13 in the backward direction of the main shaft 2.

Next, the operation of this embodiment will be explained.

The rotational output of the motor is transmitted to the main shaft 2 via the power transmission component 3, thereby rotating the main shaft 2 on which the tool 6 is clamped.

At this time, as the rotational speed of the main shaft 2 increases, each disc spring 9 slightly opens its diameter due to the centrifugal force F, as shown in FIG. is lowered by Δ1, so the entire length of the disc spring 9 in the axial direction of the main shaft 2 becomes shorter than the original length by ΔL7 (see FIG. 2).

Therefore, if we only look at the relationship between the disc spring 9 and the shifter 13,
When the diameter of the disc spring 9 is opened and the height of the disc spring 9 is shortened, the force of pushing the shifter 13 due to the elastic force of the disc spring 9 becomes weaker, so that the tensile force applied to the drawbar 12 is reduced. Furthermore, as shown in FIG. 2, the disc spring 9 and the shifter 1
3, the elastic force of the disc spring 9 no longer acts on the shifter 13, and the tensile force applied to the drawbar 12 disappears.

On the other hand, the movable member 17, which is slidably provided in the shifter 13 and the shaft hole 8, is pushed toward the distal end side of the main shaft 2 by the action of the balancer 15, so that the movable member 17 is moved to the position shown by the solid line in FIG. , moves the clearance ΔL between the disc spring 9 and the shifter 13, and presses the disc spring 9.

At a position where the force with which the movable member 17 presses the disc spring 9 and the elastic force of the disc spring 9 are balanced, the balancer 15 stops rotating around the bottle 18 (the position shown by the solid line in Figure 2), and the movable member 17 stops moving.

Due to the action of this balancer 15, the elastic force of the disc spring 9 acts on the shifter 13 via the movable member 17, and the drawbar 12
Since the tensile force is applied to the drawbar 12, the decrease in the tensile force applied to the drawbar 12 when the main shaft 2 rotates at high speed can be offset, and a reliable ramp operation can be obtained.

Also, there is a clearance Δ between the disc spring 9 and the shifter 13.
Even when the main shaft 2 rotates at such a high speed that L occurs, the elastic force of the disc spring 9 acts on the shifter 13 via the movable member 17, thereby preventing the rotation of the disc spring 9, drawbar 12, or shifter 13. Loss of balance can be prevented, and therefore rotational vibration can be suppressed to a low level.

In this way, by simply fitting the movable member 11 onto the outer periphery of the shifter 13 and attaching the balancer 15 that pushes the movable member 17 toward the tip side as the main shaft 2 rotates, a reliable tool clamping operation can be achieved as described above. At the same time, it is possible to suppress rotational vibration and prevent an adverse effect on machining accuracy.

Therefore, the tool clamping device 1 of the present invention is smaller, has fewer parts, has a simpler structure, and can reduce the cost of the device 1 compared to conventional tool clamping devices.

(Modified Example) In the above embodiment, the balancers 15 are provided at three locations, but it is not necessary to limit the number to three locations. It is sufficient if it is placed in a certain place.

When transmitting the rotational output to the main shaft 2, it was done via the power transmission part 3 fixed to the main shaft 2, but there is also a method of rotating the main shaft 2 with a built-in motor, or a method of directly connecting the main power source and the main shaft 2. , a method of directly rotating the main shaft 2, etc. may also be used.

In order to grasp the pull stud 6b of the tool 6, drawbar 1
A collet 11 is provided at the tip of the drawbar 12.
The pull stud 6b may be gripped by expanding and contracting a plurality of steel balls in the radial direction as the steel balls move forward and backward.

The shape of the balancer is as shown in the example, ml・1
If the relationship 1 < m2 ・p2 holds true, it is not necessary to have a dogleg shape.

[Brief explanation of the drawing]

1 to 4 show an embodiment of the present invention,
Figure 1 is a cross-sectional view of the tool clamping device, Figure 2 is an explanatory diagram of the operation of the main parts in Figure 1, Figure 3 is a view from A in Figure 1, and Figure 4 shows the deformation of the disc spring during high-speed rotation. FIG. In the figure 1... Tool clamp device 6... Tool 8... Shaft hole 11... Collet 13... Shifter 17... Movable member 2... Main shaft 1... Taper hole 9...・Disc spring 12...Drawbar 15...Balancer

Claims (1)

[Scope of Claims] 1) (a) A cylindrical main shaft that is rotatably held and has a tapered hole at its tip and a shaft hole that communicates with the tapered hole in the axial direction; (b) a drawbar that is inserted into the shaft hole and moves forward and backward in the axial direction to unclamp and clamp the tool inserted into the tapered hole; (d) a retraction member that is fitted to the outer periphery of the drawbar within the shaft hole and that clamps the tool against the drawbar by applying a mounting load by the shifter; (e) a movable member fitted to the outer periphery of the shifter and slidable in the axial direction with respect to the shifter and the shaft hole; (f) It is rotatably attached to the shifter, and when the main shaft rotates, it pushes the movable member toward the tip of the main shaft and presses the disc spring, thereby applying force to the shifter in the backward direction of the main shaft. A tool clamping device equipped with a balancer that gives