JPH0357372Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a holder used for attaching a rotary cutting tool such as a drill or tap to the main shaft of a machine tool.

(Prior Art) Rotary cutting tools such as drills have a reduced cutting performance due to wear of their blades and an increase in cutting torque. Therefore, the timing of re-sharpening of drills, etc. is determined by determining the number of pieces to be processed, but it is difficult to manage the lifespan when the workpiece material and cutting conditions change, and the workpiece may break during cutting, resulting in defective workpieces. There are many cases where Small-diameter drills and taps are particularly prone to breakage, and they often break easily even when chips become clogged during cutting.

A sensor that captures ultrasonic vibrations when a tool breaks is known as a means of detecting tool breakage during cutting, but what is actually required is to stop the machine before the tool breaks. , to replace the tool.

The main reason why a rotary cutting tool breaks is that the cutting torque increases due to wear of the blade or clogging of chips, as mentioned above. It is believed that rotating the tool via a safety clutch will prevent the tool from breaking, and it has been considered to interpose various torque limiters between the spindle that holds the tool and the holder body, which will cause the tool to slip when a certain torque is exceeded. Ta.

(Problem to be solved by the invention) However, with conventional holders, when the cutting torque exceeds a certain value, even if the torque limiter can automatically cut off the transmission of rotational force to the tool, the axial feed As the process continues as it is, the tool is compressed in the axial direction, and the increase in compressive stress causes the tool to break. In particular, small-diameter drills, taps, etc. may easily buckle and fail due to increased compressive stress in the axial direction. That is, as described above, simply interposing a torque limiter between the spindle that holds the tool and the holder body cannot reliably prevent tool breakage.

(Means for solving the problem) In order to solve the above-mentioned conventional problems, the present invention has a holder body that is attached to a machine tool.
A spindle having a tool chuck portion at the tip thereof is supported concentrically in a state that allows rotation around the axis and movement in the axial direction within a certain range, and between the holder body and the spindle, a torque limiting first ball clutch having a function of urging the spindle in the output limit direction and capable of engaging and disengaging the clutch when the spindle is at the output limit position; and a thrust force for holding the spindle at the output limit position. A second ball clutch for restriction is interposed, and the second ball clutch is configured such that the clutch ball fits into the deepest part of the recess on the spindle circumferential surface when the first ball clutch is in the engaged state. The present invention proposes a rotary cutting tool holder in which the depth of the recess is gradually decreased in the circumferential direction so that the clutch ball rides on the spindle circumferential surface during relative rotation between the holder main body and the spindle.

(Operation of the invention) The tool holder is set on the main shaft of a machine tool, and a rotary cutting tool such as a drill is attached to the tool chuck to carry out cutting work. The first ball clutch is held in the extended position by the biasing function of the first ball clutch and the second ball clutch, and both the first and second ball clutches are in the engaged state. Therefore, the first ball clutch breaks with a rotational force slightly lower than the limit cutting torque that is balanced with the torsional breakage strength of the tool, and the thrust force acting on the spindle when the first ball clutch breaks. By setting the biasing forces of both the first and second ball clutches so that the second ball clutch does not break, the cutting torque can be reduced to If the transmission torque of the first ball clutch is exceeded, the first ball clutch is automatically disengaged and the holder main body rotates idly relative to the spindle (tool).
That is, it is possible to prevent a torsional stress exceeding the torsional breakage strength from acting on the tool due to excessive cutting torque.

As mentioned above, when the first ball clutch operates and the forced rotational drive of the spindle (tool) stops,
As the holder body and the spindle rotate relative to each other, the clutch ball of the second ball clutch for thrust force limitation moves relative to the circumferential direction from the deepest part of the recess on the spindle side, rides on the spindle circumferential surface, and locks in the axial direction. The effect is canceled. That is, at the same time that the first ball clutch for limiting torque is disengaged, the second ball clutch for limiting thrust force is switched to a non-functional state. Therefore, even if the holder body moves forward in the direction of the rotation axis due to the feed of the main shaft after the first torque-limiting ball clutch is disengaged as described above, only the holder main body will move forward in the direction of the rotation axis with respect to the spindle (tool). This prevents excessive axial compressive stress from acting on the tool, which exceeds the compressive breakage strength, due to relatively advancing movement in the direction of the rotating shaft against the axial biasing function of the ball clutch. Can be prevented.

Furthermore, even if the cutting torque does not exceed the transmission torque of the first ball clutch, if an axial reaction force that exceeds the specified value is applied to the tool during cutting, the clutch ball of the second ball clutch will The second ball clutch is disengaged from the recess in the spindle axial direction, and the spindle is allowed to move backward relative to the holder body against the biasing function of the first ball clutch, resulting in compression breakage. Excessive axial compressive stress that exceeds the strength can be prevented from acting on the tool. Of course, in this case, since the first ball clutch is also in a disengaged state, the rotational force transmission from the holder body to the spindle (tool) is also cut off.

(Effects of the invention) As described above, according to the tool holder of the invention,
This not only prevents the cutting torque acting on the rotary cutting tool from exceeding a certain value, but also prevents excessive axial compressive force from acting on the tool, thereby reducing excessive cutting torque of the rotary cutting tool. This makes it possible to reliably prevent torsional breakage caused by bending and buckling breakage caused by excessive compressive force in the axial direction.

Moreover, since the second ball clutch for limiting thrust force is provided separately from the first ball clutch for limiting torque, there is no possibility that the spindle will be allowed to move backward in the axial direction with respect to the holder body before the cutting torque exceeds the limit value. The conditions under which each clutch is disengaged can be arbitrarily set for each clutch to prevent the clutch from disengaging. Further, according to the configuration of the present invention, at the same time as the first ball clutch for limiting torque is disengaged, the second ball clutch for limiting thrust force is switched to a substantially non-functional state, so that the second ball clutch for limiting thrust force is disengaged. Even if a thrust force of a size that can be used has not actually been applied,
At the same time as the first ball clutch for torque limiting is disengaged, the thrust force that is applied immediately after that allows the spindle to move backward in the axial direction relative to the holder body, avoiding excessive axial compressive force being applied to the tool. I can do it. This means that the thrust force when disengaging the second ball clutch for limiting thrust force is
It is only necessary to set the operating conditions of the second clutch so that it is sufficiently larger than the thrust force that is acting when the first ball clutch for torque limiting is disengaged. It becomes easy to set the operating conditions of the ball clutch.

(Example) An example of the present invention will be described below based on the attached illustrative drawings.

In Fig. 1, 1 is the holder body, and the shank part 3 serves as the attachment part to the main shaft 2 of the machine tool.
and a cylindrical main body 5 concentrically attached to the outer end of the shank portion 3 with bolts 4. A spindle 6 is supported concentrically within the cylindrical body 5 by a pair of front and rear rotary bearings 7a and 7b, and has a tool chuck 8 at its outer end protruding from the cylindrical body 5. This spindle 6
The cylindrical body 5 is rotated by the rotation bearings 7a and 7b.
In contrast, it is rotatable around the axis, and at the same time, it is movable within a certain range in the axial direction due to the existence of a minute gap (fitting tolerance) between the rotary bearings 7a and 7b. This spindle 6 and rotation bearing 7
Since an oil film of lubricating oil is present in the minute gap between the spindle 6 and the spindle 6, the spindle 6 can be supported with high accuracy in a state where it can move in the axial direction.

9 is a first ball clutch for torque limiting;
As shown in FIGS. 1 and 2, the spindle 6
A ball support plate 10 integrally protrudes from the ball support plate 10, a ball support groove 11 formed radially inside the ball support plate 10, and a portion of the ball support groove 11 is fitted into each ball support groove 11 so as to be movable in the radial direction with respect to the spindle 6. A clutch ball 12 that fits together, a ball press plate 13 loosely fitted to the spindle 6 inside the ball support plate 10 so as to be rotatable and movable in the axial direction, and this ball press plate 1
3 toward the ball support plate 11 side, and a plurality of compression coil springs 14 provided in the circumferential direction on the cylindrical inner circumferential surface 5a of the cylindrical body 5 so that a portion of each clutch ball 12 fits therein. It consists of a ball locking hole 15.

The ball pressing plate 13 urged by the spring 14 presses each clutch ball 12 with its conical pressing surface 13a. As a result, the spindle 6 is urged outward in the axial direction via the ball support plate 10, so that the spindle 6 is held at the extreme position where the ball support plate 10 contacts the rotary bearing 7a. On the other hand, each clutch ball 12 is urged in the centrifugal direction with respect to the spindle 6 by the conical pressing surface 13a of the ball pressing plate 13.
When the spindle 6 is in the extended position as described above, a portion of each clutch ball 12 is attached to the cylindrical body 5.
They fit into the side ball locking holes 15, respectively. In other words, the clutch is engaged.

Reference numeral 16 denotes a transmission torque adjustment means, which, as shown in FIGS. 1 and 3, is loosely fitted onto the spindle 6 so as to be relatively movable in the axial direction and receives the inner end of the spring 14, and a spring receiving plate 17 which receives the inner end of the spring 14. The cylindrical main body 5 is arranged such that the two protrusions 17a protruding from the spring receiving plate 17 in the diametrical direction pass through each of the protrusions 17a.
Two elongated holes 18 that are long in the axial direction provided in the cylindrical body 5 are screwed into the threaded peripheral surface portion 19 provided on the outer peripheral surface of the cylindrical body 5, and the two protruding portions 17a are fitted into the inner peripheral surface of the cylindrical body 5. It consists of an adjustment ring 21 having a mating annular groove 20 and a lock bolt 22 of the adjustment ring 21.

The state shown in FIG. 1 is a state in which the spring receiver 17 is retracted to the maximum retraction position by the adjustment ring 21, and the initial compressive stress of the spring 14 is minimized, that is, the transmission torque of the ball clutch 9 is adjusted to the minimum. Indicates the condition. Therefore, when increasing the transmission torque of the ball clutch 9, rotate the adjustment ring 21 in the extending direction with the lock bolt 22 relaxed, and increase the torque transmitted through the protrusion 17a that is in contact with one side of the annular groove 20. The spring receiving plate 17 may be moved forward in the axial direction to compress the spring 14. That is, adjustment ring 2
1, the transmission torque of the ball clutch 9 increases, and as the adjustment ring 21 rotates back, the transmission torque of the ball clutch 9 decreases.

Reference numeral 23 denotes a second ball clutch for limiting thrust force, and as shown in FIGS. A radial ball support hole 25 is provided in the cylindrical body 5 to face the recess 24 , a clutch ball 26 is fitted across each recess 24 and the ball support hole 25 , and a clutch ball 26 is provided in each of the recesses 24 and the ball support hole 25 . Screwed spring catch screw 2
7 and a clutch ball 26. The recess 24
This is constructed by cutting a certain angular range of the spindle circumferential surface 6a in a straight line along the circumferential direction, and the circumferential center portion thereof is the deepest portion, and the depth gradually decreases in the circumferential direction. Of course, if the direction of rotation of the holder main body 1 is constant, the recess 24 can also be configured to have a shape in which the depth gradually decreases only in the counter-rotation direction from the deepest part.

In use, the shank portion 3 of the holder body 1 is attached to the main shaft 2 of a machine tool in the same way as a conventional tool holder, and a required rotary cutting tool, such as a drill T, is attached to the tool chuck 8 of the spindle 6. The transmission torque of the first ball clutch 9 is adjusted by the adjustment ring 21 as described above so that the cutting torque exceeding the breakage strength of the drill T does not act on the spindle 6. Further, the second ball clutch 23 is configured to move the clutch ball 26 into the recess 24 due to the thrust force acting on the spindle 6 when the first ball clutch 23 is disengaged.
The depth of engagement between the recess 24 and the clutch ball 26 and the urging force of the spring 28 are set so that the clutch does not disengage from the deepest part in the spindle axial direction (that is, the clutch does not break).

The holder main body 1 and the spindle 6 are connected to each other by the first ball clutch 9 and the second ball clutch 23 when the spindle 6 is in the extended position.
Since they are connected in the rotational direction and the axial direction, when the main shaft 2 is rotated and feed is applied in the axial direction, the main shaft 2, holder body 1, spindle 6, and drill T rotate together and move in the axial direction. The drill T moves forward, and the workpiece W can be cut and drilled by the drill T.

During this cutting/drilling process, the cutting torque acting on the spindle 6 is reduced by the first ball clutch 9 due to clogging of chips in the cutting hole or wear of the blade of the drill T exceeding the limit. When the transmitted torque exceeds the transmission torque, the spring 14
The clutch ball 12 is connected to the ball locking hole 15 through the
The force that pushes out the clutch ball 12 from the periphery of the ball locking hole 15 overcomes the force that forces the clutch ball 12 to fit into the holder body 1 against the spindle 6.
(The cylindrical main body 5) pushes out the clutch ball 12 from the ball locking hole 15 as shown by the imaginary line in FIG. 2 while rotating relatively in the circumferential direction. At this time, the clutch ball 12 rolls in the centripetal direction within the ball support groove 11 while pushing away the ball pressing plate 13 against the biasing force of the spring 14 and disengages from the ball locking hole 15. It rolls on the cylindrical inner peripheral surface 5a in the rotational circumferential direction. As a result, the cylindrical main body 5, ie, the holder main body 1, becomes idle with respect to the spindle 6, and it is possible to prevent the drill T from being subjected to excessive cutting torque that would cause twisting and breakage.

When the first ball clutch 9 is disconnected and the holder body 1 (cylindrical body 5) rotates relative to the spindle 6 as described above, the clutch ball 26 of the second ball clutch 23 rotates as shown by the imaginary line in FIG.
moves circumferentially from the deepest part of the recess 24 on the spindle 6 side and rides on the spindle circumferential surface 6a. In this state where the clutch ball 26 rides on the spindle circumferential surface 6a, the spindle 6 of the second ball clutch 23
Since the function of locking the spindle 6 at the axial appearance position is lost, the thrust force acting on the spindle 6 causes the spindle 6 to move as shown in FIG.
is the spring 14 of the first ball clutch 9.
This results in a backward movement relative to the holder main body 1 against the holder body 1.

Of course, when the first ball clutch 9 is disconnected and only the holder main body 1 is rotating with respect to the spindle 6, the clutch ball 26 of the second ball clutch 23 moves in the circumferential direction with respect to the spindle 6 while each recess 24 is rotated. When the second ball clutch 23 is moving in and out in the circumferential direction, the second ball clutch 23
The axially transmitted force (clutch force) is significantly weaker than when the clutch ball 26 is stable at the deepest part of the recess 24. Therefore, as described above, the moment the clutch ball 26 of the second ball clutch 23 escapes from the recess 24 in the circumferential direction and first rides on the spindle circumferential surface 6a, the spindle 6
Even if the holder body 1 and the holder body 1 do not move relative to each other in the axial direction, due to the subsequent feeding action of the main shaft 2, only the holder body 1 is rotated and fed in the axial direction with respect to the stopped spindle 6. The second ball clutch 23 is easily broken,
By simply compressing the spring 14 of the first ball clutch 9 via the spring receiver 17 that moves forward together with the holder main body 1, an excessive axial compression force that may cause the drill T to break due to axial compression can be applied. There is no need for it to work. At this time, the clutch ball 12 of the first ball clutch 9 rolls on the cylindrical inner circumferential surface 5a of the cylindrical main body 5 at a position away from the ball locking hole 15 in the rotational axis direction.

Even when the first ball clutch 9 is transmitting the cutting rotational force from the holder body 1 to the spindle 6, if an excessive axial reaction force acts on the spindle 6, the reaction force is transferred to the second ball clutch 23. When the clutch ball 26 becomes larger than the axial transmission force (clutch force), the clutch ball 26 moves into the recess 24.
The second ball clutch 23 is automatically disengaged from the deepest part of the ball in the spindle axial direction. Therefore, only the holder main body 1 (cylindrical main body 5) moves forward in the axial direction with respect to the spindle 6 while compressing the spring 14. That is, it is also possible to prevent excessive axial compressive force from acting on the drill T, regardless of the cutting torque. Of course, in this case as well, the clutch ball 12 of the first ball clutch 9 separates from the ball locking hole 15 in the axial direction and the first ball clutch 9 also breaks, so that the cutting torque is not transmitted to the drill 6 either. This causes the holder body 1 to rotate idly relative to the spindle 6.

In any case, the operator must use the drill T as described above.
Since it is possible to know when the rotation of has stopped,
While the holder body 1 is moving forward in the axial direction with respect to the spindle 6, that is, before the spindle 6 reaches the retraction limit position from the extended position with respect to the holder body 1 (cylindrical body 5), the main shaft 2 is moved forward. Necessary measures such as stopping the feed manually, moving the spindle 2 backward to allow the drill T to escape from the cut hole of the workpiece W, and replacing the drill T can be taken.

When the holder body 1 is moved backward by the main shaft 2, the spindle 6 moves forward in the axial direction relative to the holder body 1 due to the biasing force of the spring 14 and reaches the limit position again, so that the ball press plate 1
The clutch ball 12 of the first ball clutch 9, which is biased in the centrifugal direction by the spring 14 via the clutch ball 3, is automatically inserted into the ball locking hole 15 of the rotating holder body 1 (cylindrical body 5). It will fit and return to the engaged state again. Further, as the spindle 6 returns to the extended position and the first ball clutch 9 returns to the engaged state as described above, the clutch ball 26 of the second ball clutch 23 also fits into the deepest part of the recess 24. , the clutch returns to the engaged state.

Incidentally, it is also possible to use a spindle backward movement detection means that electrically detects that the spindle 6 has moved backward by a certain amount with respect to the holder body 1 and sends an overload detection signal to the outside.

[Brief explanation of the drawing]

Figure 1 is a partially longitudinal side view, Figure 2 is A of Figure 1.
3 is a sectional view taken along line B-B in FIG. 1, FIG. 4 is a sectional view taken along line C-C in FIG. 1, and FIG. FIG. 1...Holder body, 2...Main shaft of machine tool,
3... Shock part, 5... Cylindrical main body, 6... Spindle, 7a, 7b... Rotating bearing, 8... Tool chuck, 9... First ball clutch for torque limiting, 10... Ball support plate, 11... Ball support groove, 12... Clutch ball, 13... Ball pressing plate, 14... Compression coil spring, 15...
Ball locking hole, 16...transmission torque adjustment means, 2
3...Second ball clutch for limiting thrust force, 2
4... recess, 26... clutch ball, 28...
spring.

Claims (1)

[Scope of utility model registration request] A spindle with a tool chuck at the tip is concentrically supported in a holder body that is attached to a machine tool so that it can rotate around the axis and move in the axial direction within a certain range, and the holder body and the spindle, a first ball clutch for torque limiting, which has a function of urging the spindle in the extension direction and is capable of engaging and disengaging the clutch when the spindle is in the extension limit position; A second ball clutch for limiting thrust force that is held at the output limit position is interposed, and the second ball clutch is arranged so that when the first ball clutch is in the engaged state, the clutch ball moves into the recess on the spindle circumferential surface. Rotary cutting is configured to fit in the deepest part, and the depth of the recess is gradually tapered in the circumferential direction so that the clutch ball rides on the spindle circumferential surface during relative rotation between the holder body and the spindle. tool holder.