TECHNICAL FIELD

This invention relates to a tool clamping method of a tool holder configured to hold a tool by clamping a clamping member attached to a holder body and relates also to such tool holder.

BACKGROUND ART

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 1.

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.

CITATION LIST

Patent Literature

PTL 1: Publication Document of Unexamined Utility Model Application No. S53-011779

SUMMARY OF INVENTION

Technical Problem

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.

Solution to Problem

According to a characterizing feature of a tool clamping method of a tool holder relating to the present invention:

the tool holder comprises:

a clamping member for clamping and holding a tool;

a holder body having, at a leading end thereof, a receiving portion for receiving the clamping member along an axis;

an operational member for attaching the clamping member to the holder body; and

the clamping member clamping the tool by an operation of the operational member;

wherein when the clamping member clamps the tool, vibration is applied to a contact portion between the clamping member and the holder body.

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 inventive configuration, 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 inventive configuration, 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, preferably, 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.

Still preferably:

there is provided a torque detecting portion for detecting a clamping torque of the clamping member;

the vibration to be applied to the contact portion is controlled based on a detected value of the torque detecting portion; and

the vibration is applied to the contact portion when the detected value exceeds a predetermined value.

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 inventive 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.

According to a characterizing feature of a tool holder relating to the present invention, the tool holder comprises:

a clamping member for clamping and holding a tool;

a holder body having, at a leading end thereof, a receiving portion for receiving the clamping member along an axis; and

an operational member for attaching the clamping member to the holder body;

the clamping member clamping the tool by an operation of the operational member; and

a vibration generating portion for applying vibration to a contact portion between the clamping member and the holder body.

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 described above, 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 configuration, 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, preferably, the vibration generating portion is included in at least one of the clamping member, the holder body and the operational member.

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.

Still preferably, the tool holder further comprises:

a torque detecting portion for detecting a clamping torque of the clamping member; and

a vibration controlling portion for controlling the vibration based on a detected value of the torque detecting portion.

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.

