Patent Description:
In recent years, with advance of machining tools, the maximum rotational speed of a spindle of the tool has been increasing. Thus, especially in a metal mold machining or a micro machining, there is an increasing demand for a small-diameter high precision chuck that can withstand even a precision machining at an ultra high speed rotation.

For instance, with the conventional tool holder configured to push in a colette (an example of a "clamping member") by rotating a nut (an example of an "operational member"), friction occurs between the nut and the colette in the course of clamping of the nut. So, it may occur that the colette can be pushed in with torsional strain in the rotational direction of the nut. As a result, if the axis of the colette is displaced from the axis of the holder body, there is the risk of deterioration in the gripping precision of the tool.

As a technique designed to solve the above, a technique is known from e.g. PTL <NUM>.

According to this technique, a pressurizing member (a coupling ring) inserted within the nut holds the colette. And, as a key member embedded in the pressurizing member comes into engagement with a key groove defined in the outer face of the holder member, relative rotation between the pressurizing member and the holder body is inhibited. With this, during rotation of the nut, the pressurizing member is not rotated therewith, but can slide in the axial direction, so that the colette can be drawn in straight along the axial direction.

PTL <NUM> discloses a method according to the preamble of claim <NUM> and tool holder according to the preamble of claim <NUM>. PLT <NUM> describes a tool clamping system for clamping a tool, in particular an ultrasound-operated machine tool. The clamping system has a housing with a housing operating area, and a tool mount including a clamping element, which has an operating area. The housing operating area and the operating area are working together for clamping the insert tool.

However, with the conventional tool holder described above, there was a problem of difficulty encountered in obtaining alignment of relative phase along the rotational direction between the key member and the key groove when the pressurizing member and the nut are to be attached to the holder body.

Namely, the attachment of the pressurizing member to the holder body involves an operation of bringing the pressurizing member with the nut fitted thereon closer to the holder body and then threading the female thread of the nut with the male thread of the holder body. In this, the operator cannot visually recognize the key member and the key groove. Thus, the operator can confirm whether the positional relation between the key member and the key groove is appropriate or not only after the nut had been threaded with the holder body to a certain extent. On the other hand, once the nut and the holder body have been threaded with each other, it becomes no longer possible to significantly move the key member and the key groove in the direction of axis, so confirmation of the engaged state between the key member and the key groove by finger feel is difficult. In this manner, with the conventional tool holder, there remains room for improvement for realizing higher work efficiency in tool replacement.

For the reasons set forth above, there is a need for a tool clamping method of a tool holder and such tool holder having better tool replacement work efficiency.

The invention provides a tool clamping method according to claim <NUM>.

In the tool holder, the clamping member holding the tool is fitted in (or fitted on) the operational member, then, by fitting the operational member on the holder (or fitting the operational member in the holder), the clamping member is attached to the holder body. With this operation of the operational member, the clamping member clamps the tool. In general, the closer the clamping member moves toward the holder body in the axial direction, the stronger the clamping of the clamping member by the holder body due to the pressed contact therebetween. Then, as the clamping member clamped to the holder body clamps the tool, attachment of the tool to the body is completed.

In the above, if the clamping operation of the operational member is continued with non-alignment between the axis of the clamping member and the axis of the holder body, the clamping member will be clamped to the holder body, with such mutual misalignment between the respective axes thereof. As a result, the axis of the tool attached to the holder body will also be misaligned relative to the axis of the holder body. Then, according to the invention, when the clamping member is to clamp the tool, vibration is applied to the contact portion between the clamping member and the holder body. As the contact portion between the clamping member and the holder body receives this vibration, the posture of the clamping member will be corrected to correct its axis (the axis of the tool). Consequently, alignment will be established between the axis of the clamping member and the axis of the holder body. And, as the clamping operation of the operational member to the holder body is continued under this condition, the axis of the operational member will be brought into agreement with the axis of the clamping member, and with this condition maintained, the tool, together with the clamping member, will be attached to the holder body. Therefore, with the invention, when the tool is to be attached to the holder body via the clamping member, the tool can be clamped and maintained with high precision by the tool holder.

Further, at least one of the clamping member, the holder body and the operational member includes a vibration generating portion and this vibration generating portion applying the vibration to the contact portion.

With the above-described arrangement, since the vibration generating portion is included in a constituent member of the tool holder, the vibration can be applied directly from the tool holder to the contact portion between the clamping member and the holder body. Further, if the vibration generating portion is provided at an appropriate position in the tool holder, the vibration can be applied in an effective manner to the contact portion between the clamping member and the holder body.

Further, preferably, vibration generated outside the tool holder is applied to the contact portion.

With the above, vibration can be applied in a reliable manner to the contact portion between the clamping member and the holder body, with vitiation generated outside the tool holder. Moreover, since there is no need to provide any vibration generating portion in the tool holder, this tool holder can be formed simple.

Still preferably, the vibration generated outside the tool holder is applied to the contact portion via at least any one of the tool, the clamping member, the holder body and the operational member.

As the vibration generated outside the tool holder is applied to the contact portion via at least any one of the tool, the clamping member, the holder body and the operational member, vibration can be applied in a reliable manner to the contact portion between the clamping member and the holder body. Further, with application of the vibration from the outside to an appropriate position in the tool holder, the vibration can be applied in an effective manner to the contact portion between the clamping member and the holder body.

As described above, the application of vibration to the contact portion between the clamping member and the holder body is effected for the sake of achieving agreement (alignment) between the axis of the clamping member and the axis of the holder body through correction of the posture of the clamping member relative to the holder body. However, at the initial stage of tool clamping by the clamping member, the clamping torque of the clamping member is still small. So, the posture of the clamping member receiving the vibration relative to the holder body can vary easily, so the posture of the clamping member relative to the holder body may not be corrected. Then, according to the arrangement described above, the vibration to be applied to the contact portion is controlled based on the clamping torque of the clamping member, such that the application of the vibration to the contact portion is effected when the detected value of the torque detecting portion exceeds a predetermined value. With this arrangement, the vibration can be applied to the contact portion at a timing when the clamping torque of the clamping member is appropriate, so that agreement between the axis of the clamping member and the axis of the holder body can be acquired reliably.

The invention provides a tool holder according to claim <NUM>.

In case the tool is to be attached to the tool holder via the clamping member, if the attachment operation by the operational member to the holder body is continued with misalignment remaining between the axis of the clamping member and the axis of the holder body, the clamping member will be clamped to the holder body with such misalignment between the respective axes remaining. As a result the axis of the tool attached to the holder body will also be displaced from the axis of the holder body. Then, according to the tool holder having the inventive configuration, a vibration generating portion is provided for applying vibration to the contact portion between the clamping member and the holder body. As the contact portion between the clamping member and the holder body receives the vibration from the vibration generating portion, the posture of the clamping member will be corrected to correct its axis (the axis of the tool) when the clamping member clamps the tool. Consequently, alignment will be established between the axis of the clamping member and the axis of the holder body. And, as the clamping operation of the operational member to the holder body is continued under this condition, the axis of the operational member will be brought into agreement with the axis of the clamping member, and with this condition maintained, the tool, together with the clamping member, will be attached to the holder body. Therefore, with the inventive tool holder, when the tool is to be attached to the holder body via the clamping member, the tool can be clamped and maintained with high precision by the tool holder.

Further, the vibration generating portion is included in at least one of the clamping member, the holder body and the operational member.

Still preferably, the tool holder further comprises:.

With the above-described arrangement, by means of the vibration controlling portion, the vibration to be applied to contact portion can be controlled based on a detected value of the torque detecting portion. With this, there can be realized e.g. a control scheme according to which the vibration is applied to the contact portion when the detected value of the torque detecting portion exceeds a predetermined value. As a result, the vibration can be applied to the contact portion at a timing when the clamping torque of the clamping member is appropriate, so that agreement between the axis of the clamping member and the axis of the holder body can be obtained reliably.

Next, a tool holder <NUM> relating to embodiments will be explained with reference to the accompanying drawings.

As shown in <FIG>, the tool holder <NUM> includes a colette <NUM> (an example of a "clamping member") for clamping and holding a tool <NUM>, a holder body <NUM>, and a nut N (an example of an "operational member") having a holding member <NUM>. The holder body <NUM> includes, at its leading end, a receiving portion <NUM> for receiving the colette <NUM> along an axis AX. In this embodiment, the colette <NUM> is inserted along the axis AX to the inside of the receiving portion <NUM> of the holder body <NUM>. The holding member <NUM> is configured to be movable together with the colette <NUM> along an axial direction X based on the axis AX while holding the colette <NUM> therein. The nut N is fitted on the holder body <NUM> and houses the holding member <NUM> therein. With this, in association with an operation of the nut N, the colette <NUM> will clamp the tool <NUM>. Meanwhile, the axis AX of the holder body <NUM> corresponds to the rotational axis of the tool holder <NUM>. In the following discussion, the direction along the axis AX will be defined as the axial direction X. In this axial direction X, the side on which the colette <NUM> is to be inserted to the receiving portion <NUM> will be defined as an axial direction base end side X2 and the opposite side will be defined as an axial direction leading end side X1. Further, the direction perpendicular to the axis AX will be defined as a radial direction R and relative to this radial direction R, the axis AX side will be defined as a radial direction inner side R2 and the opposite side thereto will be defined as a radial direction outer side R1.

In the outer circumference of the holder body <NUM>, a male thread P1 is formed. And, this male thread P1 of the holder body <NUM> is arranged to be engaged (threaded) with a female thread P2 formed in the inner circumference of the nut N. Accordingly, the nut N fitted on the holder body <NUM> will be attached directly to the holder body <NUM> via the threading engagement between the male thread P1 and the female thread P2. In the inner circumferential face of the receiving portion <NUM> of the holder body <NUM>, there is formed a tapered inner circumferential face <NUM> whose diameter progressively increases toward the axial direction leading end side X1.

The colette <NUM> is configured in the form of a cylinder so as to grip a shank portion <NUM> of the tool <NUM> with its progressively decreasing diameter from the radial direction outer side R1. The colette <NUM> is rotated together with the tool <NUM> while gripping the shank portion <NUM>. In the outer circumference of the colette <NUM>, there is formed a tapered outer circumferential face <NUM> which comes into contact with the tapered inner circumferential face <NUM> of the receiving portion <NUM>. The tapered outer circumferential face <NUM> is configured with its diameter progressively increased toward the axial direction leading end side X1. Accordingly, like the tapered outer circumferential face <NUM>, the tapered inner circumferential face <NUM> is also configured with its diameter progressively increased toward the axial direction leading end side X1.

The holding member <NUM> is fitted within the nut N to be rotatable about the axis AX on the radial direction inner side R2 of the nut N. The holding member <NUM> is configured to be movable together with the nut N along the axial direction X in association with movement of the nut N relative to the holder body <NUM> along the axial direction X through the threading engagement between the nut N and the holder body <NUM>. Further, the holding member <NUM> is configured to be movable together with the colette <NUM> along the axial direction X while holding the radial direction outer side R1 of the colette <NUM>.

The holding member <NUM> is rotatably fitted to the inner circumferential face of the front end portion of the nut N. In the outer circumferential face of the holding member <NUM> and the inner circumferential face of the nut N corresponding thereto, there are respectively formed annular grooves having a semicircular cross section, and between these annular grooves, balls <NUM> are held in a gapless manner. With this arrangement, the nut N and the holding member <NUM> are coupled to be rotatable relative to and integral with each other in the axial direction X.

The tool holder <NUM> includes a colette pushing mechanism <NUM> for pushing the colette <NUM> to the back side of the receiving portion <NUM> of the holder body <NUM> in association with a movement of the holding member <NUM> toward the axial direction base end side X2. This colette pushing mechanism <NUM> includes a first outer side contact face 8a which is formed in the outer circumference of the colette <NUM> and a first inner side contact face 8b which is formed in the inner circumference of the holding member <NUM> and comes into contact with the first outer side contact face 8a. The first outer side contact face 8a and the first inner side contact face 8b are inclined in such a manner that their diameters progressively increase toward the axial direction base end side X2. Also, the first outer side contact face 8a and the first inner side contact face 8b are raised in the radial direction R to come into contact with each other. Thus, the first outer side contact face 8a and the first inner side contact face 8b can transmit power acting at least in the axial direction X to/from each other. With the above in operation, the colette pushing mechanism <NUM> is configured to be able to push the colette <NUM> to the back side (the axial direction base end side X2) of the receiving portion <NUM> of the holder body <NUM> in association with a movement of the holding member <NUM> to the axial direction base end side X2).

Further, the tool holder <NUM> includes a colette pulling mechanism <NUM> for pulling the colette <NUM> to the axial direction leading end side X1 relative to the holder body <NUM> in association with a movement of the holding member <NUM> to the axial direction leading end side X1. This colette pulling mechanism <NUM> includes a second outer side contact face 10a which is formed in the outer circumference of the colette <NUM> and a second inner side contact face 10b which is formed in the inner circumference of the holding member <NUM> and comes into contact with the second outer side contact face 10a. The second outer side contact face 10a and the second inner side contact face 10b are inclined in such a manner that their diameters progressively increase toward the axial direction leading end side X1. Upon establishment of the contact between the second outer side contact face 10a and second inner side contact face 10b, power transmission along the axial direction X is made possible.

The holder body <NUM> includes a vibration generating portion <NUM>. This vibration generating portion <NUM> is constituted of e.g. piezoelectric elements. The vibration generating portion <NUM> is provided in annular form in the outer circumferential face 2a of the holder body <NUM>, with its piezoelectric elements being distributed continuously or dispersedly. In its operation, the vibration generating portion <NUM> applies vibration to a contact portion T between the colette <NUM> and the holder body <NUM> when the colette <NUM> clamps the tool <NUM>. The vibration generating portion <NUM> is operably connected to a vibration controlling portion <NUM> such that generates the vibration when receiving a signal voltage from the vibration controlling portion <NUM>. Thus, the vibration of the vibration generating portion <NUM> can be controlled by the vibration controlling portion <NUM>. More particularly, the vibration controlling portion <NUM> controls the amplitude, the period, the timing etc. of the vibration. In this embodiment, the vibration controlling portion <NUM> is configured to be capable of coming into contact with or detaching from the vibration generating portion <NUM>. Alternatively, the vibration controlling portion <NUM> can be formed integral with the vibration generating portion <NUM>.

Next, a method of clamping the tool <NUM> by the tool holder <NUM> will be explained. This clamping of the cool <NUM> is done by pressing the colette <NUM> toward the back side of the receiving portion <NUM> when the nut N, the holding member <NUM> and the colette <NUM> are to be attached to the holder body <NUM>.

More specifically, with the nut N, the holding member <NUM>, the colette <NUM> and the tool <NUM> being assembled to each other, the colette <NUM> will be inserted to the back side (axial direction base end side X2) of the receiving portion <NUM> of the holder body <NUM>. And, as shown in <FIG>, the nut N will be threaded into the holder body <NUM>.

Here, while the holding member <NUM> is non-rotatable about the axis AX, the nut N coupled with the holding member <NUM> on the radial direction outer side R1 of the holding member <NUM> is rotatable about the axis AX through rolling movements of the balls <NUM>. As the balls <NUM> are assembled in a gapless manner between the annular grooves, when the nut N is moved to the axial direction base end side X2 via the threading engagement of the nut N relative to the holder body <NUM>, the nut N and the holding member <NUM> will move together toward the axial direction base end side X2. In this, the tapered inner circumferential face <NUM> formed in the receiving portion <NUM> and the tapered outer circumferential face <NUM> formed in the collet <NUM> are placed in contact with each other.

In this way, when the colette <NUM> is clamping the tool <NUM>, the vibration generating portion <NUM> will have its vibration controlled by the vibration controlling portion <NUM> and will apply this vibration to the contact portion T between the colette <NUM> and the holder body <NUM>. And, as the contact portion T receives this vibration from the vibration generating portion <NUM>, the posture of the colette <NUM> is corrected, thus correcting the axis of the colette <NUM> (the axis of the tool <NUM>). Consequently, agreement will be established between the colette axis and the axis AX. If the clamping operation of the nut N to the holder body <NUM> is continued under this condition, with the agreement of the axis of the colette <NUM> and the axis of the nut N being maintained, and with this condition being maintained, the tool <NUM>, together with the colette <NUM>, will be attached to the holder body <NUM>. With this, the tool <NUM> can be clamped and held with precision by means of the tool holder <NUM>.

In the instant embodiment, in the holder body <NUM>, there is provided a torque detecting portion <NUM> for detecting a clamping torque of the colette <NUM>. For this reason, the vibration controlling portion <NUM> may control the vibration to be applied to the contact portion T, based on a detected value of the torque detecting portion <NUM>. For instance, in the vibration controlling portion <NUM>, control is effected for applying vibration to the contact portion T if a detected value of the torque detecting portion <NUM> becomes a value equal to or higher than a predetermined value. With this, vibration can be applied to the contact portion T at an appropriate timing. The torque detecting portion <NUM> may be provided in the holding member <NUM> or the colette <NUM>.

The vibration generating portion <NUM> included in the holder body <NUM> may be incorporated on more radial direction inner side R2 than the outer circumferential face 2a, rather than projecting from the outer circumferential face 2a. With this arrangement, the vibration generating portion <NUM> can be disposed in the holder body <NUM> without increasing the diameter of this holder body <NUM>.

In this embodiment, as shown in <FIG>, the vibration generating portion <NUM> is provided in the nut N. In <FIG>, the vibration generating portion <NUM> is provided to protrude from the outer circumferential face A of the nut N. Like the first embodiment, in this embodiment too, and also in all the other embodiments or variations thereof, the vibration generating portion <NUM> is provided in the annular form. Though not shown, the vibration generating portion <NUM> may be incorporated on more radial direction inner side R2 than the outer circumferential face A of the nut N.

In this embodiment, as shown in <FIG>, the vibration generating portion <NUM> is provided in the colette <NUM>. In <FIG>, the vibration generating portion <NUM> is provided to protrude from a leading end face 4a of the colette <NUM>. Though not shown, the vibration generating portion <NUM> may be incorporated on more axial direction base end side X2 than the leading end face 4a of the colette <NUM> or may be provided along the axial direction of the tool <NUM>.

In this embodiment, as shown in <FIG>, a vibration generator V having the vibration generating portion <NUM> is provided outside the tool holder <NUM>. The vibration generator V will be disposed e.g. on a jig (not shown) for holding the holder body <NUM>. The vibration generator V is configured to come into contact with the holder body <NUM> when the holder body <NUM> is attached to the jig. And, like the first embodiment, under the control of the external vibration controlling portion <NUM>, the vibration generating portion <NUM> of the vibration generator V will apply vibration to the contact portion T via the holder body <NUM>. As shown in <FIG>, it is possible to arrange such that vibration may be applied to the contact portion T via the tool <NUM> from the vibration generating portion <NUM> with disposing the vibration generator V having the vibration generating portion <NUM> to come into contact with the tool <NUM>. Further, though not shown, vibration may be applied from the vibration generating portion <NUM> to the contact portion T via the nut N and the colette <NUM>, with causing the vibration generator V having the vibration generating portion <NUM> to come into contact with the nut N and the colette <NUM>.

In this embodiment, there will be explained a tool holder <NUM> configured to generate vibration without relying on the vibration generating portion <NUM> which generates vibration electrically. As shown in <FIG>, in the tool holder <NUM>, in the outer circumference of a leading end portion <NUM> of the holder body <NUM>, there is formed a leading end outer circumferential face 23a which comes into contact with the inner circumferential face of the holding member <NUM>. Further, an intermediate portion <NUM> and the leading end portion <NUM> of the holder body <NUM> together constitute a tubular portion <NUM>. And, this tubular portion <NUM> includes a receiving portion <NUM> in which the colette <NUM> can be inserted.

The holding member <NUM> is fitted on the radial direction outer side R1 of the leading end portion <NUM> of the holder body <NUM> to be movable relative to the leading end portion <NUM> along the axial direction X and also non-rotatable relative thereto about the axis AX. The holding member <NUM> includes a first holding member <NUM> fitted in the nut N and a second holding member <NUM> fitted in the first holding member <NUM> and fitting the colette <NUM> therein. The first holding member <NUM> and the second holding member <NUM> are formed annular about the axis AX. The first holding member <NUM> is disposed on the radial direction outer side R1 relative to the second holing member <NUM>. Thus, the second holding member <NUM> is disposed on the radial direction inner side R2 relative to the first holding member <NUM>.

The tool holder <NUM> includes an anti-rotation mechanism <NUM> for restricting rotation of the holding member <NUM> relative to the holder body <NUM>. The anti-rotation mechanism <NUM> includes a thrust ball <NUM> to be fitted in a ball engaging hole <NUM>, a guide recess <NUM> for guiding the thrust ball <NUM> along the axial direction X, an enlarged width portion <NUM> formed on the axial direction base end side X2 of the guide recess <NUM> and a pair of circumferential direction contacting faces (not shown) which come into contact with the thrust ball <NUM> on the opposed sides in the circumferential direction along the axis AX. Incidentally, in the following discussion, the circumferential direction about the axis AX will be referred to simply as the "circumferential direction".

The ball engaging hole <NUM> is provided at a portion in the circumferential direction of the leading end outer circumferential face 23a of the leading end portion <NUM>. The thrust ball <NUM> is held by the ball engaging hole <NUM>. The guide recess <NUM> is provided at a portion in the circumferential direction of the inner circumferential face of the first holding member <NUM>. The guide recess <NUM> is provided in the form of a groove that is receded from the inner circumferential face of the first holding member <NUM> toward the radial direction outer side R1 and extends along the axial direction X. When the holding member <NUM> together with the nut N is to be attached to the holder body <NUM>, the thrust ball <NUM> held in the ball engaging hole <NUM> will enter the guide recess <NUM> from the end portion on the axial direction base end side X2 of the guide recess <NUM>. The enlarged width portion <NUM> is shaped to be cut away on the radial direction outer side R1 at the end portion on the axial direction base end side X2 of the guide recess <NUM>. This enlarged width portion <NUM> facilitates entrance of the thrust ball <NUM> from the end portion on the axial direction base end side X2 of the guide recess <NUM>. Though not shown, on the opposed circumferential sides of the ball engaging hole <NUM> and the guide recess <NUM>, there are formed a pair of circumferential contacting faces. And, these circumferential contacting faces are configured to come into contact with the thrust ball <NUM> in the circumferential direction. And, this contact prevents relative rotation between the first holding member <NUM> having the guide recess <NUM> and the holder body <NUM> having the ball engaging hole <NUM> about the axis AX. On the other hand, since the guide recess <NUM> along which the thrust ball <NUM> is guided extends along the axial direction X, the first holding member <NUM> is movable relative to the holder body <NUM> to the axial direction base end side X2. Therefore, by means of the anti-rotation mechanism <NUM>, relative rotation between the holding member <NUM> and the holder body <NUM> about the axis AX is restricted and at the same time their relative movement along the axial direction X is permitted.

The holding member <NUM> fitted within the nut N includes a movement allowing mechanism <NUM> as a "vibration generating portion". This movement allowing mechanism <NUM> allows a movement of the holding member <NUM> relative to the nut N along the axial direction X when the nut N is moved along the axial direction N relative to the holder body <NUM>. Specifically, the first holding member <NUM> and the second holding member <NUM> are configured to be movable relative to each other along the axial direction X. And, the movement allowing mechanism <NUM> is configured to allow the movement of the holding member <NUM> relative to the nut N along the axial direction X when the nut N is moved relative to the holder body <NUM> along the axial direction X.

As shown in <FIG>, the movement allowing mechanism <NUM> includes an engaging protruding portion <NUM> provided in the circumferential direction relative to the axis AX in either one of the first holding member <NUM> and the second holding member <NUM> and an engaged receded portion <NUM> which is provided in the other in the circumferential direction to come into engagement with the engaging protruding portion <NUM>. Further, the movement allowing mechanism <NUM> has a gap S in the radial direction R between the first holding member <NUM> and the second holding member <NUM>. And, this gap S allows the movement of the second holding member <NUM> in the radial direction R. Thus, when the colette <NUM> is pressed against the receiving portion <NUM>, the second holding member <NUM> follows the colette <NUM> in the radial direction R. More particularly, when the first outer side contacting face 8a of the colette <NUM> moves in the radial direction R, the first inner side contacting face 8b of the second holding member <NUM> follows the first outer side contacting face 8a. Also, when the colette <NUM> is not pressed against the receiving portion <NUM>, the second holding member <NUM> will move with its axis in agreement with the axis AX and the colette <NUM> will follow the second holding member <NUM> in the radial direction R. With this, vibration is applied temporarily to the contact portion T between the colette <NUM> and the holder body <NUM>, so that movement of the second holding member <NUM> along the radial direction R facilitates the agreement of the axis of the colette <NUM> with the axis AX.

The engaging protruding portion <NUM> is constituted of a groove portion 92b provided in the circumferential direction in either one of the first holding member <NUM> and the second holding member <NUM> and an elastic ring 92a disposed in the groove portion 92b and having a portion protruding from the groove portion 92b. In the instant embodiment, the groove portion 92b is provided along the entire circumference in the outer circumference of the second holding member <NUM>. The cross section of the elastic ring 92a along the axial direction X is formed circular. In this embodiment, the engaging protruding portion <NUM> constituted of the elastic ring 92a and the groove portion 92b is provided in the outer circumference of the second holding member <NUM> along the entire circumferential direction thereof. The engaging protruding portion <NUM> is configured to be elastically deformable in the radial direction R by the elasticity of the elastic ring 92a to be guided into the groove portion 92b.

In the instant embodiment, the engaged receded portion <NUM> is provided in the inner circumference of the first holding member <NUM> along the entire circumferential direction thereof. The engaged receded portion <NUM> is configured to be engaged with the engaging protruding portion <NUM> provided in the second holding member <NUM>. The engaged receded portion <NUM> includes a pair of small recesses 91a, 91c provided side by side along the axial direction X and holding the engaging protruding portion <NUM> and a small protrusion 91b provided between the pair of small recesses 91a, 91c and elastically deforming the engaging protrusion <NUM> in the radial direction R. In the instant embodiment, the pair of small recesses 91a, 91c consist of a base end side small recess 91a disposed on the axial direction base end side X2 and a leading end side small recess 91c disposed on the axial direction leading end side X1. The base end side small recess 91a and the leading end side small recess 91c have approximately same shapes. In the following discussion, the base end side small recess 91a and the leading end side small recess 91b may sometimes be referred to collectively as "a pair of small recesses 91a, 91c". Each one of the pair of small recesses 91a, 91c has a length set longer than the length of the engaging protruding portion <NUM> in the axial direction X. Therefore, each one of the pair of small recesses 91a, 91c can hold the engaging protruding portion <NUM>. In the instant embodiment, each one of the pair of small recesses 91a, 91c is capable of holding the elastic ring 92a and its depth is about half of the elastic ring 92a. The small protrusion 91b protrudes on the radial direction inner side R2. In the instant embodiment, the small protrusion 91b is disposed between the base end side small recess 91a and the leading end side small recess 91c in the axial direction X.

Next, a method of clamping the tool <NUM> using the tool holder <NUM> of the instant embodiment will be explained in details. This clamping method of the tool <NUM> includes, when attaching the nut N, the holding member <NUM> and the colette <NUM> to the holder body <NUM>, a first step of pushing the colette <NUM> to the back side of the receiving portion <NUM>, a second step of moving the second holding member <NUM> (holding member <NUM>) toward the leading end side of the receiving portion <NUM> relative to the holder body <NUM> by the movement allowing mechanism <NUM> in response to a reaction force of the pushing of the first step, and a third step of pushing the colette <NUM> again to the back side of the receiving portion <NUM> and fixing the tool <NUM> to the holder body <NUM>. The first step, the second step and the third step are carried out in series in the process of continuation of threading engagement of the nut N to the holder body <NUM>. For the sake of clarity of explanation, these three steps will be explained separately.

Firstly, as shown in <FIG>, with the nut N, the first holding member <NUM>, the second holding member <NUM>, the colette <NUM> and the tool <NUM> being assembled with each other, the colette <NUM> is inserted toward the back side (axial direction base end side X2) of the receiving portion <NUM> of the holder body <NUM>. <FIG> illustrates a state when the male thread P1 of the intermediate portion <NUM> of the holder body <NUM> and the female thread P2 of the nut N are not net engaged with each other. When the colette <NUM> is to be inserted into the receiving portion <NUM>, the colette <NUM> will be inserted into the receiving portion <NUM> while aligning the disposing position in the circumferential direction of the guide recess <NUM> formed in the first holding member <NUM> with the disposing position in the circumferential direction of the thrust ball <NUM> held in the ball engaging hole <NUM> of the leading end portion <NUM> of the holder body <NUM>. As the enlarged width portion <NUM> flared in the radial direction R is formed on the axial direction base end side X2 of the guide recess <NUM>, the thrust ball <NUM> can be easily guided into the guide recess <NUM>.

Next, the first step of pushing the colette <NUM> to the back side of the receiving portion <NUM> is carried out. As shown in <FIG>, the nut N will be threaded into the holder body <NUM>. As the thrust ball <NUM> is guided into the recess portion <NUM>, the thrust ball <NUM> will come into contact with unillustrated circumferential contacting faces formed in the guide recess <NUM> and the ball engaging hole <NUM>, so that the first holding member <NUM> (holding member <NUM>) becomes non-rotatable relative to the holder body <NUM>. On the other hand, as the guide recess <NUM> in which the thrust ball <NUM> is guided extends along the axial direction X, the first holding member <NUM> is movable relative to the holder body <NUM> to the axial direction base end side X2.

While the first holding member <NUM> is non-rotatable about the axis AX, the nut N connected with the first holding member <NUM> on the radial direction outer side R1 is rotatable about the axis AX with rolling movements of the balls <NUM>. As these balls <NUM> are fitted in a gapless manner between the annular grooves, in association with the threading engagement of the nut N with the holder body <NUM>, this nut N will be moved to the axial direction base end side X2. As a result, the nut N and the first holding member <NUM> will move together toward the axial direction base end side X2.

<FIG> shows a process in which the threading engagement of the nut N with the holder body <NUM> is continued. As shown also by virtual lines in <FIG>, the elastic ring 92a is engaged in the base end side small recess 91a and also the elastic ring 92a is in contact with the small protrusion 91b from the axial direction base end side X2. With the contact of the elastic ring 92a with the small protrusion 91b, movement of the second holding member <NUM> to the axial direction leading end side X1 is temporarily restricted. The second holding member <NUM> pushes the colette <NUM> to the axial direction base end side X2 via the first outer side contact face 8a provided adjacent the end portion of the colette <NUM> on the axial direction leading end side X1 and the first inner side contact face 8b provided in the inner circumference of the second holding member <NUM>. The tapered inner circumferential face <NUM> formed in the receiving portion <NUM> and the tapered outer circumferential face <NUM> formed in the colette <NUM> are placed in contact with each other. As the tapered inner circumferential face <NUM> and the tapered outer circumferential face <NUM> have their diameters progressively increased toward the axial direction leading end side X1, with the contact of these, the colette <NUM> applies a force for pushing the receiving portion <NUM> to the axial direction base end side X2. Further, as the threading engagement of the nut N with the holder body <NUM> is further continued, the pushing force provided by the colette <NUM> to the receiving portion <NUM> is increased and as a reaction force thereto, there is applied a force to the receiving portion <NUM> which force pushes the colette <NUM> to the axial direction leading end side X1.

Next, the second step of moving the second holding member <NUM> to the leading end side of the receiving portion <NUM> relative to the holder body <NUM> by means of the movement allowing mechanism <NUM> is carried out. As shown by the virtual lines in <FIG> and <FIG>, the elastic ring 92a and the small protrusion 91b are placed in contact with each other in the axial direction X and the elastic ring 92a has a circular shape as viewed in its section. So, when the pushing force becomes greater than the restricting force, the elastic ring 92a will receive a force from the small protrusion 91b toward the radial direction inner side R2, thus being elastically deformed (reduced in its diameter) toward the radial direction inner side R2 to ride over and past the small protrusion 91b. With this, the second holding member <NUM> is rendered movable to the axial direction leading end side X1, so the second holding member <NUM> moves to the axial direction leading end side X1. The second holding member <NUM> becomes non-movable any further to the axial direction leading end side S1 when a first restricting face 93a of the first holding member <NUM> and a second restricting face 93b of the second holding member <NUM> come into contact with each other (see <FIG>). As the elastic ring 92a rides over past the small protrusion 91b to enter the small recess 91c and the second holding member <NUM> becomes movable to the axial direction leading end side X1, the second holding member <NUM> will be released from the pushing force of the elastic ring 92a, thus being vibrated. With this, vibration is applied temporarily to the contact portion T between the holder body <NUM> and the colette <NUM>, so that the pressed contact state between the tapered inner circumferential face <NUM> and the tapered outer circumferential face <NUM> is alleviated. Namely, the attaching precision relative to the axis by light pressing-in can be maintained good and also even if the axis of the colette <NUM> is tilted relative to the axis AX when the colette <NUM> is inserted into the receiving portion <NUM>, the posture of the colette <NUM> can be readily corrected to be aligned with the axis AX. Therefore, the axis of the colette <NUM> can be easily agreed with the axis AX. Further, in this embodiment, since the gap S is formed in the radial direction R between the first holding member <NUM> and the second holding member <NUM>, as the second holding member <NUM> moves in the radial direction R, this further facilitates alignment between the axis of the colette <NUM> gripped by this second holding member <NUM> and the axis AX.

Next, the third step of pushing again the colette <NUM> to the back side of the receiving portion <NUM> after the second step to fix the tool <NUM> to the holder body <NUM> is carried out. As shown in <FIG>, when the first restricting face 93a of the first holding member <NUM> and the second restricting face 93b of the second holding member <NUM> are in contact with each other, the nut N, the first holding member <NUM>, the second holding member <NUM> and the colette <NUM> become movable together toward the axial direction base end side X2. From this condition, as the threading engagement of the nut N to the holder body <NUM> is continued, the nut N, the first holding member <NUM>, the second holding member <NUM> and the colette <NUM> are moved together toward the axial direction base end side X2 (see <FIG>). With this, the colette <NUM> will be pushed progressively strongly by the holder body <NUM>, thus completing the clamping of the tool <NUM>.

Claim 1:
A tool clamping method for a tool holder (<NUM>), the tool holder (<NUM>) comprising:
a clamping member (<NUM>) for clamping and holding a tool (<NUM>);
a holder body (<NUM>) having, at a leading end thereof, a receiving portion (<NUM>) for receiving the clamping member (<NUM>) along an axis; and
an operational member (N) for attaching the clamping member (<NUM>) to the holder body (<NUM>);
said method comprising the step of moving the clamping member (<NUM>) towards the holder body (<NUM>) in the axial direction by an operation of the operational member (N), thus increasing a clamping of the clamping member (<NUM>) by the holder body (<NUM>) due to a pressed contact therebetween,
characterized in that the method comprises the step of when the clamping member (<NUM>) clamps the tool (<NUM>) during said moving of the clamping member (<NUM>), applying vibration to a contact portion (T) between the clamping member (<NUM>) and the holder body (<NUM>), to axially align the clamping member (<NUM>) with the holder body (<NUM>).