Tool driving device and method of producing drilled product

According to one implementation, a tool driving device includes a drill chuck, a motor, a casing and a vibrating mechanism. The drill chuck holds a drill. The motor is configured to rotate the drill chuck. The casing houses the motor. The vibrating mechanism is configured to periodically reciprocate the drill chuck relatively to the casing in a tool axis direction during rotation of the drill chuck. The vibrating mechanism is configured to distance the drill chuck from the casing at a first speed smaller than a second speed for bringing the drill chuck close to the casing.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2022-132188, filed on Aug. 23, 2022; the entire contents of which are incorporated herein by reference.

FIELD

Implementations described herein relate generally to a tool driving device and a method of producing a drilled product.

BACKGROUND

It is important for drilling to finely cut and discharge chips so that grooves of a drill may not be clogged with the chips. For that reason, a mechanism for cutting chips finely by intentionally vibrating a drill in a tool axis direction has been suggested conventionally (for example, refer to Japanese Patent Application Publication JP 2003-117852A, Japanese Patent Application Publication JP 2003-266426A and Japanese Patent Application Publication JP H10-000505A).

Specifically, a spindle can be vibrated in the rotation axis direction by putting balls, held by a retainer, in and out from concave portions rotated together with the spindle. More specifically, a drill moves together with the spindle in a direction away from an object to be drilled (workpiece) when the balls are put in the concave portions respectively while the drill moves together with the spindle in a direction toward the workpiece when the balls are put out from the concave portions respectively. Thereby, the spindle and the drill can be periodically reciprocated in the tool axis direction with constant amplitude.

As other examples of a mechanism for vibrating a drill, a mechanism which vibrates a spindle by sliding a cam fixed to the spindle, and a mechanism in which vibration is generated by ultrasonic waves are also suggested (for example, refer to Japanese Patent Publication JP H06-098579B2 and Japanese Patent Application Publication JP 2019-214079A).

However, when the conventional vibrating mechanism which vibrates a drill by rolling balls is used, the drill separates from a workpiece for a moment at the timing of entry of each ball into a concave portion, and subsequently the drill is suddenly pushed out toward the workpiece at the timing of exit of each ball from the concave portion. For this reason, when a user performs drilling using a handheld tool driving device, the tool driving device possibly held with loosen force may be pushed back due to drilling reaction. Consequently, drilling cannot be restarted promptly after the balls are put out from the concave portions respectively.

Conversely, when a user holds a handheld tool driving device with force, a drill collides with a workpiece at the timing of exit of each ball from the concave portion. Therefore, when the workpiece has large strength compared to that of the drill, the drill may be damaged. As a concrete example, when titanium is drilled with adopting the conventional vibrating mechanism, a drill may be damaged since titanium has strength larger than that of typical material of the drill.

Therefore, when hard-to-cut material, such as titanium, may be drilled, the conventional vibrating mechanism cannot be adopted. As a result, when metal, such as aluminum, as well as hard-to-cut material, such as titanium, is drilled by a tool driving device having no vibrating mechanism, a discharged continuous chip of the metal cannot be divided, and thereby may clog a groove of the drill. When a groove of the drill is clogged with a chip, a problem that rotation of the drill stops or a workpiece is damaged may arise.

In particular, in a case where laminated material of metal and FRP (Fiber Reinforced Plastic), such as GFRP (Glass Fiber Reinforced Plastic) or CFRP (Carbon Fiber Reinforced Plastic), which is also called composite material, is drilled from the FRP side, a problem that a drill is clogged with a metal chip, and thereby it becomes difficult to continue drilling, or a problem that the hole size of the FRP becomes excessive as a result that the inner surface of the FRP is cut by the drill clogged with a metal chip may arise when the drilling of the metal starts after the drilling of the FRP has been completed.

On the other hand, adopting a mechanism which vibrates a spindle by sliding a cam having recesses and projections causes a problem that the vibration becomes unstable and an exchange frequency of a part increases, compared with a mechanism which vibrates a spindle by rolling balls, due to remarkable wear of the cam. Accordingly, in order to vibrate a drill stably for a long period of time, it is realistic to adopt a mechanism which vibrates a spindle by rolling rotating bodies, such as balls, whose friction and wear are small.

Accordingly, an object of the present invention is to make it possible to drill a workpiece stably by preventing chip clogging in a drill and breakage of the drill.

SUMMARY

In general, according to one implementation, a tool driving device includes a drill chuck, a motor, a casing and a vibrating mechanism. The drill chuck holds a drill. The motor is configured to rotate the drill chuck. The casing houses the motor. The vibrating mechanism is configured to periodically reciprocate the drill chuck relatively to the casing in a tool axis direction during rotation of the drill chuck. The vibrating mechanism is configured to distance the drill chuck from the casing at a first speed smaller than a second speed for bringing the drill chuck close to the casing.

Further, according to one implementation, a method of producing a drilled product includes: holding the drill by the above-mentioned tool driving device; and producing the drilled product by drilling an object by the drill rotated by the tool driving device.

DETAILED DESCRIPTION

A tool driving device and a method of producing a drilled product according to implementations of the present invention will be described with reference to accompanying drawings.

FIG.1is a partial sectional view showing structure of a tool driving device according to the first implementation of the present invention.

A tool driving device1is a device for holding and rotating a drill T in order to drill a workpiece W to be drilled. Note that, there is a case where a boring tool held by the tool driving device1is called a drill bit while the tool driving device1itself for rotating a drill bit is called a drill.

The tool driving device1may include not only a rotating mechanism of the drill T, but a feeding mechanism of the drill T. That is, the drill T may be fed out towards the workpiece W by pushing out the tool driving de vice1itself by a user. Alternatively, the drill T may be fed out towards the workpiece W automatically or semiautomatically by a tool feeding mechanism.

The tool driving device1can be composed of a drill chuck2for holding the drill T, a motor3for rotating the drill chuck2, and a casing4for housing the motor3. The motor3may be any of an electric type, a hydraulic type, a pneumatic type, and another type. The output shaft of the motor3can be operated as a spindle5which rotates the drill chuck2together with the drill T. In other words, the output shaft of the motor3may be integrated with the spindle5. As a matter of course, the output shaft of the motor3and the spindle5may be disposed in parallel or on a same straight line, and torque may be transmitted by gears or the like.

When the tool driving device1is handheld, a grip6for being grasped by a user is formed in the casing4. A switch7for operating the motor3may be attached to the grip6or the vicinity of the grip6.

In addition, the tool driving device1include a vibrating mechanism8which periodically reciprocates the drill T, the drill chuck2, and the spindle5relatively to the casing4in a tool axis AX direction during rotation of the drill T, the drill chuck2, and the spindle5. When the spindle5is reciprocated in the tool axis AX direction, the motor3is also reciprocated in the tool axis AX direction as long as the motor3is typical. Accordingly, a clearance may be made between the motor3and a motor casing3A for housing the motor3, for example, so that the motor3can be reciprocated in the tool axis AX direction although the motor casing3A originally houses the motor3without any clearance.

When the drill T and the drill chuck2are periodically reciprocated in the tool axis AX direction by the vibrating mechanism8by a distance of 0.01 mm to 0.15 mm which is slight compared to a feeding amount, a discharged continuous chip like a metal chip can be divided. In other words, when the drill T and the drill chuck2are vibrated with amplitude of 0.01 mm to 0.15 mm, a chip can be divided. As a result, the drill T can be prevented from being clogged with a chip.

This is because moving the drill T and the drill chuck2in the direction toward the casing4results in separation of the drill T from the workpiece W once during cutting, and thereby drilling is interrupted. After that, the cutting can be restarted by feeding the drill T and the drill chuck2. Such processing that drilling is intermittently performed while discharging chips by repeating cutting and intermission alternately is also called peck processing, peck drilling or step drilling.

Note that, too small amplitude of the vibration, which is concretely amplitude of less than 0.01 mm, results in insufficiency in the dividing effect of a chip while too large amplitude of the vibration, which is concretely amplitude of more than 0.15 mm, makes it difficult for a user to hold the tool driving device1by hand.

In particular, the vibrating mechanism8is configured to distance the drill T and the drill chuck2from the casing4at a speed smaller than that for bringing the drill T and the drill chuck2close to the casing4. That is, the drill T vibrates at different speeds between the forward path and the return path. More specifically, the drill T and the drill chuck2are instantaneously moved in the direction toward the casing4in order to interrupt drilling once by distancing the drill T, during cutting, from the workpiece W while the drill T and the drill chuck2are moved as slowly as possible in the direction away from the casing4in order to bring the drill T and the drill chuck2, distanced from the workpiece W once, close to the workpiece W again.

Accordingly, the drill T is instantaneously pulled apart from the workpiece W, and thereby a chip can be divided certainly by intermission of drilling. Meanwhile, the drill T is moved toward the workpiece W at a low speed at the time of restarting the drilling, and therefore trouble that the drill T collides to the workpiece W, and thereby the drill T is damaged can be prevented. In addition, since the drill T is moved toward the workpiece W at a low speed just after restarting the drilling, the increasing rate of the drilling reaction can be reduced, and thereby trouble that a user is pushed back due to precipitous increase in drilling reaction can be avoided.

The vibrating mechanism8can consist of a sliding surface9and balls10. The sliding surface9has recesses and projections corresponding to the moving speed of the drill T and the drill chuck2. The balls10roll on the sliding surface9during rotation of the drill chuck2. Note that, the vibrating mechanism8, i.e., the vibrator can also consist of the sliding surface9and rolling objects, such as rollers each having a rotation shaft, skids, or disk members each having smooth convexity to which lubricity is given, sliding on the recesses and projections of the sliding surface9, instead of the balls10. Henceforth, the most practical case where the balls10are used will be described as an example.

FIG.2is an enlarged partial longitudinal sectional view of the vibrating mechanism8shown inFIG.1.FIG.3is a left side view of a static ring11included in the vibrating mechanism8shown inFIG.2in a state where the balls10have been placed on the static ring11.FIG.4is a right side view of a rotary ring12included in the vibrating mechanism8shown inFIG.2.FIG.5shows the cross section, developed on a plane, of the rotary ring12at the position A-A shown inFIG.4.FIG.6shows the recesses and projections of the rotary ring12emphasized by enlarging the developed cross sectional view of the rotary ring12shown inFIG.5only in the thickness direction of the rotary ring12.

The balls10are equally spaced on a same circle between the drill chuck2and the casing4so that the respective balls10can roll. The sliding surface9to which the balls10contact while rolling during rotation of the drill chuck2can be formed directly or indirectly in either the drill chuck2or the casing4.

For that purpose, in the illustrated example, the static ring11and the rotary ring12are fixed to the casing4and the drill chuck2respectively with a space so that the static ring11and the rotary ring12may not contact with each other. The static ring11has a through hole for passing through the spindle5at the center portion. The rotary ring12also has a through hole for passing through the spindle5at the center portion. Note that, the rotary ring12may be fixed to the spindle5by forming a female screw on the inner surface of the through hole of the rotary ring12while forming a male screw on the surface of the spindle5. Therefore, the rotary ring12rotates together with the drill chuck2and the spindle5relatively to the casing4and the static ring11although the static ring11does not rotate relatively to the casing4.

The balls10are partially housed in spherical concaves, formed on the static ring11at an equal interval on a same circle, respectively in a state where the respective balls10can roll. Accordingly, the balls10respectively roll at constant positions relative to the casing4to which the static ring11is fixed. In this case, the static ring11functions as an annular ball retainer for holding a part of each ball10in a state where each ball10can roll.

On the other hand, the rotary ring12has the sliding surface9having the recesses and projections. The shape of the recesses and projections of the sliding surface9is made to have level differences9A at an equal interval while changing smoothly from each level difference9A toward the adjacent level difference9A so that the balls10may fall down from the level differences9A simultaneously during the normal rotation of the drill chuck2while the balls10may ascend no level differences during the normal rotation of the drill chuck2. That is, the shape of the recesses and projections of the sliding surface9is determined so that the balls10simultaneously fall down from the level differences9A of the sliding surface9, and subsequently roll on the smoothly sloping surfaces up to the following level differences9A respectively since there are no level differences which the balls10have to ascend, as exemplified byFIG.5andFIG.6, as long as the drill T and the drill chuck2are normally rotated by the normal rotation of the motor3.

In this case, the balls10simultaneously fall down from the level differences9A of the sliding surface9respectively due to the drilling reaction from the workpiece W in the midst of drilling by the normal rotation of the drill T and the drill chuck2since the rotary ring12, having the sliding surface9, fixed to the drill chuck2rotates relatively to the balls10. As a result, the drill T and the drill chuck2are momentarily and temporarily distanced from the workpiece W to approach the casing4. Thereby, the drilling is interrupted, and a chip can be divided.

On the contrary, after the balls10have fallen down from the higher positions of the level differences9A to the lower positions respectively, the balls10roll on the sliding surface9, of which position changes smoothly, up to the higher positions of the adjacent level differences9A respectively while contacting with the sliding surface9since the drill T and the drill chuck2are fed, and thereby receive the drilling reaction from the workpiece W again. Consequently, the drill T and the drill chuck2do not collide with the workpiece W at a high speed, and therefore the drilling reaction from the workpiece W does not increase locally. As a result, a user can continue drilling stably without being pushed back by the drilling reaction from the workpiece W while avoiding breakage of the drill T.

The sliding surface9can be formed as the inner surface of a groove9B whose length direction is the rotation direction including the normal rotation direction and the reverse rotation direction of the drill chuck2, as illustrated. In that case, the groove9B has such slopes that the depth of the groove9B shallows gradually from the respective level differences9A, formed on the inner surface of the groove9B, toward the adjacent level differences9A.

Generally, the normal rotation is the clockwise rotation, and therefore the groove9B of the rotary ring12rotates together with the drill chuck2clockwise relatively to the balls10. Hence, the balls10rotate counterclockwise relatively to the groove9B of the rotary ring12. For this reason, each level difference9A is formed in the groove9B in the direction where the balls10fall down when the balls10rotate counterclockwise relatively to the annular groove9B, as exemplified byFIG.4toFIG.6. In other words, the groove9B has the level differences9A, from which the balls10fall down over the ridgelines when the balls10rotate counterclockwise relatively to the annular groove9B, i.e., the balls10move rightward relatively to the groove9B in the developed views shown inFIG.5andFIG.6, and no level differences whose ridgelines are targets which the balls10have to ascend. Note that, in case of special drilling by rotating the drill T counterclockwise, what is necessary is to reverse the direction of the level differences9A and the slopes.

Note that, the sliding surface9may be a tapered or corrugated surface having the level differences9A in the same direction in the rotating direction of the drill chuck2, instead of the inner surface of the groove9B.

When the groove9B is formed for the sliding surface9, the groove9B may be a V-groove whose cross section is V-shaped, a groove whose bottom surface is flat, or the like. When the shape of at least a part of the cross section of the groove9B is made to an arc having the same radius as that of each ball10so that the balls10may fit to a part of the bottom of the groove9B as illustrated, progress of wear of the balls10can be delayed since the balls10do not come into point contact with the groove9B but come into line contact with the groove9B. When the shape of the cross section of the groove9B is made to an arc, the groove9B is formed by groove machining using a ball end mill in many cases. For this reason, the valley side of each level difference9A may be rounded.

Although the bottom of the groove9B is wholly sloped between the level differences9A adjacent to each other in the example shown inFIG.5andFIG.6, ranges in which the bottom is sloped may be limited to parts beginning at the valley sides of the level differences9A while the remaining portions toward the mountain sides of the adjacent level differences9A may not have sloped bottoms respectively as long as edges of level differences which the balls10must ascend disappear.

FIG.7is a right side view of another example of the rotary ring12shown inFIG.2in a case where ranges in which the bottom face of the groove9B formed on the rotary ring12slopes have been limited to the vicinities of the valley side portions of the level differences9A respectively.FIG.8shows the cross section, developed on a plane, of the rotary ring12at the position B-B shown inFIG.7.FIG.9shows the recesses and projections of the rotary ring12emphasized by enlarging the developed cross sectional view of the rotary ring12shown inFIG.8only in the thickness direction of the rotary ring12.

As exemplified byFIG.7toFIG.9, the ranges in which the bottom of the groove9B is sloped may be limited to the vicinities of the valley side portions of the level differences9A as long as the edges of the level differences which the balls10ascend are not generated. In this case, the shape of the rotary ring12can be simplified since the bottom of the groove9B is not oblique on the mountain sides of the level differences9A. Therefore, production of the rotary ring12can be also simplified. In particular, the smaller the height of each level difference9A becomes, the shorter each range in which the bottom of the groove9B is sloped can be made in order to remove an edge of a level difference, which the balls10must ascend, to a negligible degree.

The above-mentioned sliding surface9formed by the inner surface of the sloped groove9B or the like has the level differences9A at an equal interval, and therefore normally rotating the drill T and the drill chuck2at a predetermined rotating speed causes periodic vibration of the drill T and the drill chuck2at amplitude equivalent to the height of the level differences9A. That is, once the balls10ascend the ridgelines of the level differences9A, the moving direction of the drill T and the drill chuck2is reversed, and thereby drilling is interrupted.

Therefore, the height of the level differences9A from which the balls10fall down can be determined so that a user can hold the tool driving device1by hand while the vibration has desired amplitude from a viewpoint of achieving the diving effect of chip, concretely to not less than 0.01 mm and not more than 0.15 mm as described above. Note that, the size of the balls10is not important, but the moving distance of the balls10in the tool axis AX direction, i.e., the height of the level differences9A is important. Nevertheless, decreasing the size of the balls10leads to a merit that the vibrating mechanism8can be downsized, and conversely, increasing the size of the balls10leads to a merit that progress of wear of the balls10can be delayed.

The number of the balls10should be three or more from a viewpoint of preventing deflection amount of the drill T and the drill chuck2from increasing even when the drilling reaction is applied from the workpiece W. When the number of the balls10is increased, the number of the level differences9A also increases according to the number of the balls10, and therefore the interval between the level differences9A adjacent to each other becomes short. Hence, when the number of the balls10is increased, the frequency of the drill T and the drill chuck2increases.

When the frequency of the drill T and the drill chuck2increases, a merit that chips can be made finer can be achieved while the cutting period per unit time becomes short since the interrupt frequency of drilling increases. Accordingly, it is desirable to confine the number of the balls10to one required in order to make a chip fine to a degree that chip clogging of the drill T can be fully avoided, from a viewpoint of preventing the cutting time from increasing. Note that, it is considered that the sufficient number of the balls10is three as long as a typical metal material, such as aluminum, is drilled under typical drilling conditions, such as a hole size, a hole depth, a rotating speed of the drill T, and the number of the cutting edges of the drill T.

It is also possible to vibrate the drill T and the drill chuck2at a predetermined frequency when the number of the level differences9A formed on the sliding surface9is different from that of the balls10but equal to a multiple of the number of the balls10. Nevertheless, it is appropriate to confine the number of the level differences9A to one necessary for achieving the dividing effect of chip since the more the number of the level differences9A is increased, the shorter the cutting period per unit time becomes, similarly to a case of increasing the number of the balls10.

These conditions with regard to the balls10and the shape of the sliding surface9are the same in a case where the sliding surface9is not formed on the rotary ring12fixed to the drill chuck2but is formed on the static ring11fixed to the casing4. When the sliding surface9is formed on the static ring11fixed to the casing4, spherical concavities can be formed on the rotary ring12fixed to the drill chuck2so that the rotary ring12serves as a ball retainer. In that case, the balls10roll at constant positions relatively to the drill chuck2to which the rotary ring12is fixed. Therefore, when the drill T and the drill chuck2are normally rotated, the balls10also normally rotate while rolling on the sliding surface9.

The above-mentioned tool driving device1generates periodic vibration, which distances the drill T and the drill chuck2from the workpiece W instantaneously and brings the drill T and the drill chuck2close to the workpiece W side slowly, using the vibrating mechanism8consisting of, e.g., the sliding surface9, having appropriate concavities and convexities, and the balls10rolling on the sliding surface9.

According to the tool driving device1, chips can be divided finely and thereby discharged easily since the drill T is pulled apart from the workpiece W intermittently and periodically. Accordingly, deterioration in quality of a hole, such as excess in diameter of a hole in an FRP, caused by chip clogging in a groove of the drill T can be prevented. Therefore, when the drill T is held by the tool driving device1and the workpiece W is drilled by the drill T rotated by the tool driving device1, a drilled product having a hole with high quality can be produced. For example, even when the workpiece W consisting of laminated FRP and metal, such as laminated CFRP and aluminum or titanium, is drilled as exemplified byFIG.1, a drilled product having a hole with high quality can be produced since metal chips are divided and thereby do not clog any groove of the drill T.

In addition, trouble that the drill T is damaged due to collision of the drill T with the workpiece W and trouble that the tool driving device1held by hand of a user is pushed back by the drilling reaction can be avoided since the speed of the drill T is small at the time of approaching the workpiece W and change of the drilling reaction is also small in case of adopting the vibrating mechanism8of the tool driving device1while the conventional vibrating mechanism which vibrates a drill by rolling balls causes precipitous change of the vibrating direction when the balls come out from concave portions as well as when the balls go into the concave portions, and thereby trouble that the drill collides with a workpiece or trouble that a user is pushed back due to instantaneously increased drilling reaction sometimes arises.

In addition, in case of the vibrating mechanism8of the tool driving device1, wear of the balls10due to repeated collision of the balls10with edges of level differences can be avoided since there are no level differences, which the balls10ascend, on the sliding surface9although the conventional vibrating mechanism, which makes balls go into and come out from concave portions, causes a problem that the balls and the edges of the concave portions are worn away since the balls repeatedly contact with the edges of the concave portions when the balls come out from the concave portions.

FIG.10is a partial sectional view showing structure of a tool driving device according to the second implementation of the present invention.

A tool driving device1A in the second implementation shown inFIG.10is different from the tool driving device1in the first implementation in structure that a vibrating mechanism8A has the balls10rolling while rotating relatively to both the drill chuck2and the casing4. Other structure and actions of the tool driving device1A in the second implementation are not substantially different from those of the tool driving device1in the first implementation. Therefore, the same signs are attached to the same elements and the corresponding elements while explanation thereof is omitted.

In case of rotating the balls10without fixing the positions of the balls10relatively to both the drill chuck2and the casing4, what is necessary is to dispose an annular ball retainer20, for holding parts of the balls10in a state where the balls10can roll, rotatably in the rotating direction of the drill chuck2including the normal rotation direction and the inverse rotation direction, i.e., around the tool axis AX, without fixing the ball retainer20to any of the drill chuck2and the casing4. For example, the ball retainer20can be rotatably disposed in a space formed between the static ring11fixed to the casing4and the rotary ring12fixed to the drill chuck2, as exemplified byFIG.10.

FIG.11is an enlarged partial longitudinal sectional view of the vibrating mechanism8A shown inFIG.10.FIG.12is a left side view of the ball retainer20shown inFIG.11in a state where the balls10have been held by the ball retainer20.FIG.13is a right side view of the rotary ring12shown inFIG.11.

As exemplified byFIG.11andFIG.12, the balls10and the ball retainer20, consisting of an annular plate having through holes whose number is same as that of the balls10, can be disposed between the static ring11and the rotary ring12in a state where the balls10are held by the ball retainer20. Note that, in the example shown inFIG.11andFIG.12, the ball retainer20can be housed between the static ring11and the rotary ring12since the static ring11has a cylindrical edge whose inner diameter is larger than the outer diameter of the rotary ring12.

As exemplified byFIG.13, the rotary ring12has the sliding surface9, having the level differences9A, formed as the inner surface of the sloped groove9B or the like, similar to that in the first implementation. As a matter of course, when the sloped groove9B is formed on the rotary ring12, the bottom of the groove9B may be locally or partially sloped as exemplified byFIG.7toFIG.9

When the ball retainer20can be rotated relatively to both of the static ring11and the rotary ring12as illustrated, the drilling reaction acts not only on the balls10from the rotary ring12, but on the static ring11from the balls10. Therefore, the balls10are rotated while rolling relatively to both the static ring11and the rotary ring12due to the frictional force between the balls10and the static ring11, and the frictional force between the balls10and the rotary ring12. That is, the balls10roll while rotating relatively to the drill chuck2and the casing4.

For this reason, a groove11A, having a constant depth, for rolling the balls10may be also formed on the static ring11. In this case, making the shape of the cross section of the groove11A such an arc that the inner surface of the groove11A may fit with the balls10allows decreasing the progression rate of wear of the balls10since the balls10roll while coming into line contact with the inner surface of the groove11A. As a matter of course, the sliding surface9having the level differences9A, formed as the inner surface of the sloped groove9B or the like may be formed on the static ring11side.

According to the above-mentioned second implementation, effect that the frictional force between the balls10, and the static ring11and the rotary ring12can be reduced remarkably can be attained in addition to effect similar to that in the first implementation. Specifically, in a case where the balls10are held by a ball retainer consisting of the static ring11having spherical concavities like the first implementation, the balls10necessarily roll while sliding relatively to either the static ring11or the rotary ring12. Accordingly, when the rotation speed of the drill T and the drill chuck2is large, the frictional force between the balls10, and the static ring11and the rotary ring12also becomes large, and thereby the balls10may be worn out in a short time.

In particular, when drilling is performed with the drill T having a small tool diameter of about 3 mm to 10 mm, the rotation speed of the drill T becomes 2000 rpm to 6000 rpm in many cases. As a result of actual examinations using prototypes under the corresponding drilling conditions, it has been confirmed that the balls10were occasionally heated up to not less than 100° C. and worn out due to friction, and thereby the diameter of each ball10decreased. Therefore, when drilling is performed using the drill T having a small diameter, it is desirable to adopt the second implementation, which allows reducing the frictional force between the balls10, and the static ring11and the rotary ring12to a negligible extent, from a viewpoint of securing a tool life.

FIG.14is a longitudinal sectional view showing structure of a vibrating mechanism included in a tool driving device according to the third implementation of the present invention.

A tool driving device1B in the third implementation shown inFIG.14is different from each of the tool driving device1in the first implementation and the tool driving device1A in the second implementation in a point that a vibrating mechanism8B has a function to adjust the amplitude of the vibration generated in the drill T and the drill chuck2, and a function to switch the vibration off. Other structure and actions of the tool driving device1B in the third implementation are not substantially different from those of each of the tool driving device1in the first implementation and the tool driving device1A in the second implementation. Therefore, only the vibrating mechanism8B is illustrated, and the same signs are attached to the same elements and the corresponding elements while explanation thereof is omitted.

The vibrating mechanism8B in the third implementation is configured so that the amplitude of the vibration in the tool axis AX direction generated in the drill T and the drill chuck2, i.e., the amplitude of the reciprocation of the drill T and the drill chuck2in the tool axis AX direction can be adjusted with an amplitude adjusting thread30.

In this case, when the length of the amplitude adjusting thread30is determined so that the amplitude of the drill T and the drill chuck2in the tool axis AX direction can be adjusted to zero, the amplitude of the reciprocation of the drill T and the drill chuck2can be switched between an on-state and the off-state. That is, a vibration mode in which the drill T and the drill chuck2are reciprocated in the tool axis AX direction can be switched to the non-vibration mode in which the drill T and the drill chuck2are not reciprocated in the tool axis AX direction.

FIG.14shows an example of the vibrating mechanism8B composed of the balls10, the static ring11, the rotary ring12and the ball retainer20. Similarly to the second implementation, the ball retainer20holding the balls10is rotatably disposed between the static ring11fixed to the casing4and the rotary ring12fixed to the drill chuck2. Accordingly, the amplitude of the vibration of the drill T and the drill chuck2can be adjusted by adjusting the interval between the static ring11and the rotary ring12by the amplitude adjusting thread30.

FIG.15is a left side view of the static ring11shown inFIG.14.FIG.16is a left side view of the ball retainer20shown inFIG.14in a state where the balls10have been held by the ball retainer20.FIG.17is a right side view of the rotary ring12shown inFIG.14.

Similarly to the second implementation, the ball retainer20holding the balls10as shown inFIG.14andFIG.16can be rotatably disposed between the static ring11fixed to the casing4and the rotary ring12fixed to the drill chuck2. In this case, a groove11A whose depth is constant can be formed on the static ring11as shown inFIG.14andFIG.15while a groove9B having a sliding surface9consisting of slops and level differences9A of 0.01 mm to 0.15 mm can be formed on the rotary ring12as shown inFIG.14andFIG.17. As a matter of course, the depth of the groove9B on the rotary ring12may be decreased gradually between the level differences9A as shown inFIG.13. Meanwhile, the groove11A on the static ring11may be omitted.

The space formed between the groove11A of the static ring11and the groove9B of the rotary ring12can be used as the pathway for moving the balls10relatively to the static ring11and the rotary ring12. In this case, when the rotary ring12rotates relatively to the casing4and the static ring11together with the drill chuck2and the spindle5, the balls10pass through the level differences9A on the rotary ring12which receives the drilling reaction force from the workpiece W together with the drill T and the drill chuck2, and thereby, the drill T and the drill chuck2can be vibrated in the tool axis AX direction.

The more the interval between the static ring11and the rotary ring12is widened, the more the moving distance of the rotary ring12in the tool axis AX direction decreases gradually even when the balls10passes through the level differences9A on the rotary ring12. That is, when the interval between the static ring11and the rotary ring12is widened, the amplitude of the vibration of the drill T and the drill chuck2decreases. When the interval between the static ring11and the rotary ring12reaches a certain distance, the amplitude becomes zero and the vibration stops.

This is because the balls10pass through the interspace formed between the groove11A of the static ring11and the groove9B of the rotary ring12without resistance to the drilling reaction force in principle in a case where the drilling reaction force is applied from the workpiece W to the rotary ring12fixed to the drill chuck2as long as the interspace formed between the groove11A of the static ring11and the groove9B of the rotary ring12has a size corresponding to the diameter of the balls10.

Accordingly, as shown inFIG.14andFIG.15, the static ring11can be configured to be slidable relatively to the casing4in the tool axis AX direction by coupling the static ring11to the casing4with the amplitude adjusting thread30. In this case, since the rotary ring12is fixed to the drill chuck2, the interval between the static ring11and the rotary ring12can be finely adjusted by sliding the static ring11in the tool axis AX direction.

AlthoughFIG.14shows an example of case where an internal thread is formed on the inner surface of the portion, having cylindrical structure, of the static ring11while an external thread is formed on the outer surface of the portion, having cylindrical structure, of the casing4, the internal thread may be reversed with the external thread. That is, the static ring11may be inserted into the inside of the casing4instead of inserting the distal portion of the casing4into the inside of the static ring11.

In order to make it possible to slide the static ring11relatively to the casing4in the tool axis AX direction, it is necessary to space the static ring11from the casing4with an interval varying slightly. Accordingly, an elastic O ring31made of rubber or the like may be disposed between the static ring11and the casing4. Thereby, the static ring11can be supported with the O ring31in the tool axis AX direction since the O ring31is crushed by the moving distance of the static ring11even when the static ring11is moved in the tool axis AX direction within a range of the 0.01 mm order to the 0.1 mm order.

As shown inFIG.14andFIG.15, an internal thread whose depth direction is the radial direction of the static ring11can be formed in the static ring11so that a fixing screw32can be fastened. Thereby, the static ring11can be prevented from rotating relatively to the casing4by fastening the fixing screw32so that the casing4may be pressed with the tip of the fixing screw32. That is, the fixing screw32can be attached as a stopper for preventing the static ring11from rotating to the casing4and sliding in the tool axis AX direction.

The fixing screw32may be not only a slotted screw, fastened with a slotted screwdriver, but a hand screw, such as a wing bolt or a knurled screw. Although the O ring31may be omitted since the static ring11can be prevented from sliding in the tool axis AX direction using the fixing screw32, supporting the static ring11with both of the fixing screw32, which applies pressure in the radial direction on the static ring11, and the O ring31, which can support the static ring11in the tool axis AX direction, leads to the stabilization of the static ring11.

When the position of the static ring11in the tool axis AX direction is finely adjusted as a fastening amount of the amplitude adjusting thread30, the amplitude of the reciprocation of the drill T and the drill chuck2in the tool axis AX direction can be adjusted continuously and steplessly. When the amplitude of the reciprocation of the drill T and the drill chuck2in the tool axis AX direction is adjustable to zero by sufficiently securing the stroke of the amplitude adjusting thread30, the drill T and the drill chuck2can be rotated in the state that the reciprocation of the drill T and the drill chuck2is stopped.

Accordingly, the amplitude of the vibration of the drill T and the drill chuck2can be adjusted according to drilling conditions including the size of the drill T, the material of the workpiece W, and the rotating speed of the drill T so that chips may be divided to have appropriate sizes. As mentioned above, the amplitude of the vibration of the drill T and the drill chuck2changes according to the sliding amount of the static ring11in the tool axis AX direction. The sliding amount of the static ring11in the tool axis AX direction changes according to the rotating amount of the static ring11to the casing4, which is equivalent to the fastening amount of the amplitude adjusting thread30. Accordingly, scale marks for checking the rotating amount of the static ring11may be presented so that a user can finely adjust the amplitude of the vibration of the drill T and the drill chuck2manually and easily.

FIG.18shows an example of scale marks representing degrees of the amplitude of the vibration of the drill T and the drill chuck2, generated by the vibrating mechanism8B shown inFIG.14.

For example, as shown inFIG.18, the position of the fixing screw32can be set to a reference position while scale marks can be presented on the casing4. In the example shown inFIG.18, indications of the amplitude of the vibration consist of three levels of L (large), M (middle) and S (small), and the matching position for switching the vibration off is also presented.

Accordingly, a user can finely adjust the amplitude of the vibration according to drilling conditions easily by reference to the scale marks. Specifically, a user can fix the position of the static ring11in the tool axis AX direction by rotating the static ring11by reference to the scale marks and fastening the fixing screw32at a desired rotation position.

As described above, the vibrating mechanism8B in the third implementation has an amplitude adjustment mechanism, i.e., an amplitude adjuster consisting of the amplitude adjusting thread30for adjustable setting of the amplitude of the vibration of the drill T and the drill chuck2so that the amplitude of the vibration of the drill T and the drill chuck2can be adjusted according to drilling conditions.

According to the third implementation, the amplitude of the vibration generated in the drill T and the drill chuck2can be adjusted according to drilling conditions including the tool diameter of the drill T to be used, the material of the workpiece W, and the rotating speed of the drill T so that chips may have appropriate sizes. As a result, the drilling quality can be improved and drilling can be stabilized by preventing chip clogging

As a practical example, in case of rotating the drill T, having a small diameter, at a high speed, the amplitude can be set small so as to decrease interruption times of cutting due to the vibration since the cutting amount is small. Conversely, in case of rotating the drill T, having a large diameter, at a low speed, the amplitude can be set large so as to divide chips certainly since the cutting amount is large.

As another example, in case of drilling a laminated material of a metal and an FRP from the metal side, dividing metal chips can avoid a trouble that a hole in resin becomes too large. Conversely, in case of drilling the workpiece W made of a single material, it may be desirable to generate no vibration from a viewpoint of shortening a cutting time. That is, in a case where any continuous chip is not discharged ever as well as a case where an undivided chip does not cause a problem in drilling quality, vibrating the drill T and the drill chuck2causes interruptions of cutting which lengthen a cutting time.

In such a case, the vibration of the drill T and the drill chuck2can be switched off so that the increase in a cutting time can be avoided. That is, not only an adjustment of the amplitude of the vibration but switching between an on state and the off state can be performed so that the balance between a drilling quality and a cutting time may become optimum.

Note that, the amplitude of the vibration of the drill T and the drill chuck2can be changed also in each of the first and second implementations by exchanging the rotary ring12for another rotary ring12having a groove9B whose depth is different, or exchanging the static ring11for another static ring11having a groove11A whose depth is different.

On the other hand, in case of the third implementation, it is unnecessary to exchange any part of the vibrating mechanism8B. Therefore, working hours of a user can be reduced. In addition, it also becomes unnecessary to produce two or more parts. Moreover, in case of the third implementation, the amplitude of the vibration can be changed continuously. Therefore, changing drilling conditions according to the amplitude of the vibration, such as changing the thrust force at the time of the drilling, becomes unnecessary. That is, the amplitude of the vibration can be adjusted according to drilling conditions instead of determining drilling conditions according to settable amplitude of the vibration.

(First Modification of Third Implementation)

FIG.19is a longitudinal sectional view showing structure of the first modification of a vibrating mechanism included in a tool driving device according to the third implementation of the present invention.

As shown inFIG.19, the groove9B having the slopes and the level differences9A may be formed on the static ring11instead of the rotary ring12, as described also in each of the first and second implementations. In that case, forming a groove12A, having a constant depth, on the rotary ring12allows delaying the progress of wear of each ball10since each ball10is brought into line contact with the rotary ring12.

The amplitude adjusting thread30may be formed on the rotary ring12as shown inFIG.19although the amplitude adjusting thread30may be formed on the static ring11as shown inFIG.14. That is, the amplitude adjusting thread30can be formed on at least one of the static ring11and the rotary ring12.

In the example shown inFIG.19, the internal thread of the amplitude adjusting thread30is formed on the inner surface of a cylindrical portion formed on the drill chuck2side of the rotary ring12. Meanwhile, the external thread of the amplitude adjusting thread30is formed on the outer surface of the drill chuck2. Therefore, the rotary ring12can be slid in the tool axis AX direction relatively to the drill chuck2by adjusting the fastening amount of the amplitude adjusting thread30. As a result, the interval of the static ring11and the rotary ring12can be changed.

In case of moving the rotary ring12relatively to the drill chuck2, it is necessary to change the interspace between the rotary ring12and the drill chuck2. Accordingly, an O ring31can be disposed between the rotary ring12and the drill chuck2. In addition, the rotary ring12can be fixed to the drill chuck2with a fixing screw32.

Note that, the amplitude adjusting thread30may be formed between the spindle5and the rotary ring12. Specifically, the external thread may be formed on the outer surface of the spindle5while the internal thread may be formed on the inner surface of the rotary ring12. Also in that case, the rotary ring12can be fixed to the drill chuck2with a fixing screw32from the outside as long as a cylindrical portion is formed on the drill chuck2side of the rotary ring12.

(Second Modification of Third Implementation)

FIG.20is a front view showing structure of the second modification of a vibrating mechanism included in a tool driving device according to the third implementation of the present invention.

The amplitude adjustment mechanism for adjusting the amplitude of the vibration of the drill T and the drill chuck2by changing the interval between the static ring11and the rotary ring12can also be formed using a key40and a key groove41although a case where the vibrating mechanism8B has the amplitude adjusting thread30as the amplitude adjustment mechanism has been described in the above-mentioned example.

As a concrete example, the columnar key40whose length direction is a radial direction of the static ring11can be projected from the distal portion of the casing4inserted into the cylindrical portion of the static ring11as shown inFIG.20. On the other hand, the key groove41in which the key40can be slid in the length direction of the key groove41can be formed in the static ring11.

The pathway of the key groove41can be determined so that the static ring11may slide in the tool axis AX direction when the key40is slid along the key groove41by rotating the static ring11relatively to the casing4. In this case, the static ring11can be slid in the tool axis AX direction relatively to the casing4according to the rotating amount of the static ring11.

In the example shown inFIG.20, the static ring11has the stepwise key groove41derived by coupling the end portions of three parallel partial key grooves41, of which length directions are the circumferential direction of the static ring11, to each other. Therefore, when the static ring11is rotated, the static ring11can be slid in the tool axis AX direction in stages by a distance corresponding to a level difference in the key groove41.

Accordingly, when the positions of the key groove41are determined according to possible intervals to be adjusted between the static ring11and the rotary ring12, the interval between the static ring11and the rotary ring12can be set to a target interval out of the possible intervals. Since each level difference in the key groove41is equivalent to a sliding amount of the static ring11, each level difference is in the 0.01 mm order to the 0.1 mm order.

In the example shown inFIG.20, the static ring11has the key groove41consisting of the three partial key grooves41. The first partial key groove41is for sliding the static ring11to a position where the interval between the static ring11and the rotary ring12becomes large sufficiently and thereby vibration becomes the off state. The second partial key groove41is for sliding the static ring11to a position where the interval between the static ring11and the rotary ring12becomes a middle degree and thereby vibration arises with small amplitude. The third partial key groove41is for sliding the static ring11to a position where the interval between the static ring11and the rotary ring12becomes the minimum and thereby vibration arises with large amplitude.

Note that, the key groove41whose length direction is spiral may be formed on the static ring11, and the static ring11may be configured to be fixable to the casing4with a fixing screw32. In that case, the static ring11can be continuously slid in the tool axis AX direction.

Alternatively, the key groove41may not be a through-slit but be a groove having the bottom face. Therefore, the key40may be projected from the inner surface of the static ring11toward the casing4while the key groove41may be formed on the casing4. Nevertheless, forming the through key groove41in the static ring11allows checking the position of the key40from the outside.

The amplitude adjustment mechanism formed with the key40and the key groove41may also be disposed between the rotary ring12and the drill chuck2. That is, the amplitude adjusting thread30shown inFIG.19may be replaced with the amplitude adjustment mechanism formed with the key40and the key groove41.

OTHER IMPLEMENTATIONS