Work holding device

Abstract

A workpiece holding device is provided that can improve the machining efficiency for a plurality of types of workpieces by facilitating the workpiece clamp replacement work for the spindle. [Solution] A workpiece holding device 100 includes a clamp base 101 attached to the spindle of a machine tool, and a workpiece clamp 130 having a workpiece-side hook portion 134 that can be detachably hooked onto the clamp base 101 and that detachably holds a workpiece WK. The clamp base 101 includes a drawbar 110 that has a base-side hook portion 111 that hooks onto the workpiece-side hook portion 134, and that fits within the clamp base 101 so that the base-side hook portion 111 slidably moves in two directions, moving away from or approaching the clamp base 101. The clamp base 101 also includes a drawbar displacement mechanism that includes a first pressure-receiving portion 113, a second pressure-receiving portion 116, and a drawbar operating body 120.

Description

[Technical Field]

[0001] The present invention relates to a workpiece holding device that holds a workpiece on the central axis of rotation of a main spindle of a machine tool. [Background technology]

[0002] Conventionally, there have been workpiece holding devices that detachably hold a workpiece to be machined. For example, Patent Document 1 below discloses a precision machine equipped with a driver that holds a workpiece, which is the workpiece to be machined, on a rotating spindle. In this case, the precision machine appears to have the driver attached to the spindle with a bolt (see Figure 1 in Patent Document 1). The driver is configured to fit into the outer circumferential surface of the workpiece or the opening of the bore hole, and is thought to be prepared for each workpiece. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-198025

[0004] However, in the precision machine described in Patent Document 1, it is thought that the driver (work clamp), which requires the bolt to be removed and attached, needs to be replaced on the spindle (main shaft) each time workpieces (workpieces) with different shapes are machined. This makes the driver replacement process cumbersome and reduces the efficiency of machining multiple types of workpieces. Summary of the Invention

[0005] The present invention has been made to address the above-mentioned problems, and its purpose is to provide a work holding device that can easily replace the work clamp with the spindle and improve the machining efficiency for multiple types of workpieces.

[0006] In order to achieve the above object, the present invention is characterized in that it is a work holding device that holds a workpiece on the central axis of rotation of the main spindle of a machine tool, and includes a clamp base attached to the main spindle, and a work clamp that has a work-side hook portion that can be detachably hooked onto the clamp base and holds the workpiece detachably, and the clamp base includes a draw bar that has a base-side hook portion to which the work-side hook portion is hooked and that fits within the clamp base so that the base-side hook portion can slide freely in two directions, either moving away from or approaching the clamp base, and a draw bar displacement mechanism that reciprocates the draw bar within the clamp base in the two directions.

[0007] According to this, the work holding device can fix or detach the work clamp hooked on the base-side hook portion to the clamp base by moving the draw bar back and forth via the draw bar displacement mechanism, which makes it easy to replace the work clamp with the spindle and improves the machining efficiency for multiple types of workpieces.

[0008] Another feature of the present invention is that in the work holding device, the clamp base has a clamp fitting portion into which the work clamp is removably fitted, and the work clamp has a base fitting portion into which the clamp fitting portion is removably fitted.

[0009] With this, the work clamp of the work holding device fits into the clamp fitting portion formed on the clamp base via the base fitting portion, so that it can be attached in a fixed position relative to the clamp base, thereby reducing the workload of positioning work when attaching it to the clamp base.

[0010] Another feature of the present invention is that in the work holding device, the drawbar displacement mechanism comprises a drawbar operating body that fits freely back and forth from the outer surface of the clamp base to the inside of the clamp base, a first pressure receiving part that is provided on the drawbar and is pressed by the drawbar operating body to displace the drawbar to one side in the reciprocating displacement, and a second pressure receiving part that is provided on the drawbar and is pressed by the drawbar operating body to displace the drawbar to the other side in the reciprocating displacement.

[0011] According to this, the workpiece holding device can easily reciprocate the drawbar by operating the drawbar operating body, and can easily lock or unlock the workpiece clamp relative to the clamp base.

[0012] Another feature of the present invention is that, in the work holding device, the draw bar operating body is formed in a rod shape, the draw bar has an operating body fitting hole formed in a hole shape into which the draw bar operating body fits, and the first pressure receiving portion and the second pressure receiving portion are respectively provided on opposite sides of the inner periphery of the operating body fitting hole.

[0013] According to this, the work holding device has a drawbar operating body formed in a rod shape, and the first pressure receiving portion and the second pressure receiving portion are respectively provided on opposite sides of the inner peripheral portion of the operating body fitting hole formed in the shape of a hole in the drawbar into which the drawbar operating body fits, so that the drawbar displacement mechanism can be easily configured.

[0014] Another feature of the present invention is that in the workpiece holding device, the draw bar operating body passes through the operating body fitting hole and both end sides of the draw bar operating body are fitted into the clamp base.

[0015] According to this, the work holding device has a drawbar operating body that passes through the operating body fitting hole and both end sides of the drawbar operating body are fitted into the clamp base, so that the drawbar operating body can be moved forward and backward stably as both ends are supported within the clamp base.

[0016] Another feature of the present invention is that, in the work holding device, the first pressure receiving portion is formed by the inner surface of a cylindrical surface formed within the operating body fitting hole, the second pressure receiving portion is formed by protruding from the cylindrical surface formed within the operating body fitting hole, and the cylindrical surface from which the second pressure receiving portion protrudes is formed with its axis at a different position from the axis of the cylindrical surface constituting the first pressure receiving portion.

[0017] According to this, the work holding device is formed such that the cylindrical surface from which the second pressure receiving portion protrudes has an axis at a different position from the axis of the cylindrical surface constituting the first pressure receiving portion, so that it is possible to change the contact or non-contact relationship between the cylindrical surface from which the second pressure receiving portion protrudes and the drawbar operating body when the first pressure receiving portion is in contact with the drawbar operating body, or the contact or non-contact relationship between the cylindrical surface constituting the first pressure receiving portion and the drawbar operating body when the second pressure receiving portion is in contact with the drawbar operating body.

[0018] Another feature of the present invention is that, in the workpiece holding device, at least one of the first pressure receiving portion and the second pressure receiving portion is configured as a separate body from the draw bar.

[0019] According to this, in the work holding device, at least one of the first pressure receiving portion and the second pressure receiving portion is configured as a separate body from the draw bar, which increases the degree of freedom in the installation position of the first pressure receiving portion and the second pressure receiving portion, which are configured as separate bodies, within the draw bar, and also makes it possible to replace damaged first pressure receiving portion and second pressure receiving portion. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a side cross-sectional view showing an outline of the configuration of a workpiece holding device according to the present invention in a used state. [Figure 2] 2A and 2B show an outline of the configuration of a clamp base in the workpiece holding device shown in FIG. 1, where 2A is a cross-sectional view of the clamp base and 2B is a front view of the clamp base. [Figure 3]2A to 2C show an outline of the configuration of the draw bar in the work holding device shown in FIG. 1, where 2A is a plan view of the draw bar, 2B is a side cross-sectional view of the draw bar, and 2C is a front view of the draw bar. [Figure 4] 2 is a front view showing the outline of the configuration of a draw bar operating body in the work holding device shown in FIG. 1. [Figure 5] 2A and 2B show an outline of the configuration of a joint in the work holding device shown in FIG. 1, where 2A is a cross-sectional view of the joint and 2B is a front view of the joint. [Figure 6] 1A and 1B show how the work holder is set to a locked state or an unlocked state by operating the draw bar operating body in the work holding device shown in FIG. 1 to slide and displace the draw bar, where 1A is a partial cross-sectional side view when the work holder is in the locked state, and 1B is a partial cross-sectional side view when the work holder is in the unlocked state. DETAILED DESCRIPTION OF THE INVENTION

[0021] An embodiment of a workpiece holding device according to the present invention will now be described with reference to the drawings. Fig. 1 is a side cross-sectional view showing the outline of the configuration of workpiece holding devices 100 and 200 according to the present invention in use.

[0022] The workpiece holding device 100 is a mechanical device attached to a rotationally driven spindle in a machine tool (not shown) such as a lathe, milling machine, or machining center, and detachably holds a workpiece WK. The workpiece holding device 200 is attached to a tailstock in the machine tool, which is disposed opposite the axis of the spindle and supports the workpiece WK from both sides on the axis of the spindle, and detachably holds the workpiece WK. Because the workpiece holding device 200 has the same configuration as the workpiece holding device 100, this embodiment will describe the workpiece holding device 100, and parts of the workpiece holding device 200 will be assigned the same reference numerals as those of the workpiece holding device 100, with their descriptions kept to a minimum.

[0023] In this embodiment, the workpiece WK is an external gear with teeth formed on the outer circumferential surface of a metal cylinder. The workpiece WK is indicated by a two-dot chain line in Fig. 1. The machine tool is a grinding machine that grinds the tooth surface of the external gear that constitutes the workpiece WK.

[0024] (Configuration of work holding devices 100, 200) The workpiece holding device 100 is mainly composed of a clamp base 101 and a workpiece clamp 130.

[0025] The clamp base 101 is a component that is attached to the spindle of a machine tool and detachably holds the work clamp 130, and is made of a cylindrical metal material. As shown in Figures 2(A) and 2(B), the clamp base 101 has a clamp base main body 102 formed in the shape of a flat ring, which has a spindle fitting portion 103, a clamp fitting portion 104, a draw bar holding portion 105, a first operating body holding portion 106, and a second operating body holding portion 107.

[0026] The spindle fitting portion 103 is a portion that fits onto the spindle of the machine tool, and is formed by protruding cylindrically from the center of one end face (the right side in the figure) of the clamp base main body 102. In this case, the spindle fitting portion 103 is formed in a cylindrical shape that is coaxial with the axis of the spindle of the machine tool.

[0027] The clamp fitting portion 104 is a portion for fitting the base fitting portion 133 of the work clamp 130 to position the work clamp 130, and is formed to protrude cylindrically from the center of the other end face (left side in the figure) of the clamp base body 102. The clamp fitting portion 104 is formed in a cylindrical shape that is coaxial with the spindle fitting portion 103, i.e., coaxial with the axis of the spindle of the machine tool.

[0028] The drawbar holding portion 105 is a portion that holds a drawbar 110, which will be described later, in a state that allows it to slide freely in the axial direction of the clamp base main body 102, and is composed of through-holes that penetrate the clamp base main body 102, the spindle fitting portion 103, and the clamp fitting portion 104. In this embodiment, the drawbar holding portion 105 is formed in a cylindrical shape that is coaxial with the clamp base main body 102, the spindle fitting portion 103, and the clamp fitting portion 104.

[0029] The first operating body holding portion 106 is a part for reciprocatingly displacing the drawbar operating body 120 radially within the clamp base 101, and is composed of a female threaded hole that opens on the outer surface of the clamp base main body 102 and penetrates into the drawbar holding portion 105.

[0030] The second operating body holding portion 107 is a portion that holds the drawbar operating body 120 so as to be slidable in the radial direction within the clamp base 101, and is configured as a hole that opens in the drawbar holding portion 105 along the axis of the first operating body holding portion 106. In this case, the second operating body holding portion 107 is formed so as to open on the opposite side to the opening of the first operating body holding portion 106 on the outer surface of the clamp base main body 102, but this opening is closed by a plug. That is, in this embodiment, the second operating body holding portion 107 is configured as a bottomed hole, but it may also be a through-hole.

[0031] The spindle mounting portion 108 is a portion for mounting the clamp base 101 to the spindle of a machine tool, and is configured with a through hole through which a bolt 108a passes. Four spindle mounting portions 108 are formed around the circumferential direction of the clamp base 101 at positions corresponding to the holder mounting portions 136.

[0032] The draw bar 110 is a component for selectively switching between a locked state in which the work clamp 130 is fixed to the clamp base 101 and an unlocked state in which it can be removed, and is configured by forming a metal material into a rod shape that can slide freely on the draw bar holding portion 105. Specifically, as shown in Figures 3(A) to 3(C), the draw bar 110 is configured to include a base-side hook portion 111, an operating body fitting hole 112, a first pressure-receiving portion 113, a relief portion 114, and a second pressure-receiving portion forming body 115.

[0033] The base-side hook portion 111 is a portion to which the work-side hook portion 134 of the work clamp 130 is detachably hooked, and is formed in a state of projecting from one end (the left side in the figure) of the draw bar 110. More specifically, the base-side hook portion 111 is formed with a diameter smaller than the outer diameter of the draw bar 110 and is configured with three pieces that project radially outward from three positions in the circumferential direction at the tip of a round bar that extends in the axial direction of the draw bar 110.

[0034] The operation body fitting hole 112 is a portion into which the drawbar operation body 120 is slidably fitted, and is configured as a through-hole through which the drawbar operation body 120 passes in a direction perpendicular to the axial direction of the round bar-shaped drawbar 110. A first pressure-receiving portion 113 and a relief portion 114 are formed in this operation body fitting hole 112.

[0035] The first pressure receiving portion 113 is a portion for displacing the drawbar 110 to one side in the direction of reciprocating displacement of the drawbar 110 (axial direction of the drawbar holding portion 105) when the first pressing portion 123 on the side of the drawbar operating body 120 is pressed against it. Specifically, the first pressure receiving portion 113 is formed of a tapered round hole that opens on the outer surface of the drawbar 110 and has a depth slightly exceeding the center of the drawbar 110. In this case, the taper angle of the tapered round hole that forms the first pressure receiving portion 113 is set to 20° in this embodiment.

[0036] The relief portion 114 is a portion that surrounds the second pressing portion 124 of the drawbar operating body 120 and exposes the second pressure receiving portion 116 formed at the tip portion of the second pressure receiving portion forming body 115, and is configured as a straight round hole that is in communication with the first pressure receiving portion 113 and opens on the opposite side to the opening of the first pressure receiving portion 113 on the outer surface of the drawbar 110. In this case, the relief portion 114 is formed with an inner diameter that is larger than the outer diameter of the bar side second contact portion of the drawbar operating body 120.

[0037] In this embodiment, the relief portion 114 is formed at a position where the axis C114 is slightly offset from the axis C113 of the first pressure receiving portion 113 in the Y-axis direction toward the opposite side from the base-side hook portion 111. In this embodiment, the relief portion 114 is formed at a position where the axis C114 is offset by 0.5 mm from the axis C113 of the first pressure receiving portion 113 in the Y-axis direction toward the opposite side from the base-side hook portion 111. In this case, the position of the axis C114 of the relief portion 114 in the X-axis direction is the same as the axis C113 of the first pressure receiving portion 113, and the relief portion 114 is located on the axis of the drawbar 110. Here, the Y-axis direction in the figure is the axial direction of the drawbar 110, the Z-axis direction in the figure is the vertical direction (axial direction of the operating body fitting hole 112) perpendicular to the Y-axis direction in the figure, and the X-axis direction in the figure is the direction perpendicular to both the Y-axis direction and the Z-axis direction in the figure.

[0038] The second pressure-receiving portion forming body 115 is a component having a second pressure-receiving portion 116, and is configured by forming a metal material into a round bar shape. More specifically, the second pressure-receiving portion forming body 115 is configured by forming a male thread on the outer periphery of a metal round bar, and forming a tapered second pressure-receiving portion 116 whose outer diameter gradually narrows on one tip side. In addition, the second pressure-receiving portion forming body 115 has a recess with a hexagonal cross section formed on the other end for rotating it with a hexagonal wrench.

[0039] This second pressure-receiving portion forming body 115 is held in a state where it is screwed into an internally threaded hole 117 that is provided in the drawbar 110 and passes through from the base-side hook portion 111 to the recess 114. In this case, the second pressure-receiving portion forming body 115 is fixed in place by a set screw 117a that is screwed in from the base-side hook portion 111 side in a state where the second pressure-receiving portion 116 at the tip end of the internally threaded hole 117 protrudes into the recess 114.

[0040] The drawbar operating body 120 is a component for reciprocatingly displacing the drawbar 110 within the drawbar holding portion 105, and is configured by forming a metal material into a rod shape. Specifically, as shown in Figures 4(A) and 4(B), the drawbar operating body 120 is configured to include a first base fitting portion 121, a second base fitting portion 122, a first pressing portion 123, a second pressing portion 124, and an operating portion 125.

[0041] The first base fitting portion 121 is a portion that fits into the first operating body holding portion 106 of the clamp base 101, and is configured by forming a male thread that fits into the first operating body holding portion 106 in the area from approximately the axial center of the round rod body that constitutes the drawbar operating body 120 to one end (the upper side in the figure).

[0042] The second base fitting portion 122 is a portion that fits into the second operating body holding portion 107 of the clamp base 101, and is configured such that the area from approximately the axial center of the round rod body that constitutes the drawbar operating body 120 to the other (lower side in the figure) end is formed into a round rod shape with a smaller diameter than the outer diameters of the first base fitting portion 121 and the second operating body holding portion 107.

[0043] The first pressing portion 123 is a portion that is pressed against the first pressure receiving portion 113 of the drawbar 110, and the portion of the first base fitting portion 121 on the second base fitting portion 122 side is formed in a tapered shape that corresponds to the tapered shape of the first pressure receiving portion 113.

[0044] The second pressing portion 124 is a portion that is pressed against the second pressure receiving portion 116 of the drawbar 110, and is configured such that the outer diameter of the portion of the second base fitting portion 122 on the first base fitting portion 121 side is continuously tapered toward the first base fitting portion 121 side, forming a narrow tapered shape.

[0045] The operating portion 125 is a part for rotating the drawbar operating body 120, and has a recess with a hexagonal cross section formed at one end (the upper side in the figure) of the drawbar operating body 120 for rotating it with a hexagonal wrench.

[0046] The work clamp 130 is a component for holding the workpiece WK in cooperation with the work holding device 200, and is mainly composed of a joint 131 and a work holder 140.

[0047] The joint 131 is a component for attaching the work clamp 130 to the clamp base 101, and is made of a cylindrical metal material. As shown in Figures 5(A) and 5(B), the joint 131 has a cylindrical joint body 132, a base fitting portion 133, a work-side hook portion 134, a holder fitting portion 135, and a holder mounting portion 136.

[0048] The base fitting portion 133 is a part that is used to position the clamp base 101 by fitting into the clamp fitting portion 104 of the clamp base 101, and is composed of a cylindrical hole that opens in the center of one end face (right side in the figure) of the joint body 132.

[0049] The workpiece-side hooking portion 134 is a portion that can be detachably hooked onto the base-side hooking portion 111 of the drawbar 110 that fits into the clamp base 101, and is formed in a state in which it protrudes radially outward in a concave shape at the innermost portion of the base fitting portion 133 of the joint body 132. More specifically, the workpiece-side hooking portion 134 is configured by three recesses that protrude radially outward from three circumferential positions on the inner peripheral portion of the axial center of the joint body 132. In this case, these three recesses in the workpiece-side hooking portion 134 are formed into shapes that correspond to the three pieces that make up the base-side hooking portion 111 so that the three pieces can be inserted (inserted and passed through) into these recesses.

[0050] The holder fitting portion 135 is a portion for fitting the joint fitting portion 142 of the work holder 140 to position the work holder 140, and is composed of a cylindrical hole opening in the center of the other end face (left side in the figure) of the joint body 132.

[0051] The holder mounting portion 136 is a portion for mounting the work holder 140, and is configured with a female threaded hole into which a bolt 148 is screwed. Four holder mounting portions 136 are formed on the joint body 132 at equal intervals along the circumferential direction.

[0052] The work holder 140 is a component that holds the workpiece WK in cooperation with the work holder 240 that is disposed opposite the work holder 140, and is made of a cylindrical metal material. The work holder 140 has a cylindrical work holder body 141 that has a joint fitting portion 142, a work pressing portion 143, a work holding bar 144, and a joint mounting portion 147.

[0053] The joint fitting portion 142 is a portion for positioning with respect to the joint 131 by fitting into the holder fitting portion 135 of the joint 131, and is formed so as to protrude cylindrically from the center of one end face (the right side in the figure) of the work holder main body 141. This joint fitting portion 142 is formed in a cylindrical shape that is coaxial with the axis of the work holder main body 141.

[0054] The workpiece pressing portion 143 is a portion that presses one end face (the right side in the figure) of the workpiece WK in order to sandwich and hold the workpiece WK together with the work holder 240, and is formed in a ring-shaped protrusion at the other end (the left side in the figure) of both end portions of the workpiece holder main body 141. This workpiece pressing portion 143 is formed in a cylindrical shape that is coaxial with the axis of the workpiece holder main body 141.

[0055] The workpiece holding bar 144 is a component that passes through the workpiece WK to hold the workpiece WK, and is configured with a metal rod body having a workpiece holding portion 144a formed in the axial center thereof for holding the workpiece WK. One end (right side in the figure) of the workpiece holding bar 144 in the axial direction is inserted into and held in the workholder main body 141, and the other end (left side in the figure) is inserted into and held in the workholder 240.

[0056] Specifically, the workpiece holding bar 144 is held by having one end (the right side in the figure) inserted into a bottomed bar holding hole 145 that opens into the inner portion of the workpiece pressing portion 143 in the workpiece holder main body 141 and extends in the axial direction of the workpiece holder main body 141. In this case, the one end (the right side in the figure) of the workpiece holding bar 144 is inserted into the bar holding hole 145 via a coil spring 146a, and two anti-detachment bolts 146b are fitted to the outer periphery of the workpiece holding bar 144 to prevent the workpiece holding bar 144 from coming out of the bar holding hole 145 while allowing the workpiece holding bar 144 to slide back and forth relative to the bar holding hole 145. In other words, the workpiece holding bar 144 is elastically pressed toward the workpiece holder 240 by the coil spring 146a, and is held by the anti-detachment bolts 146b in a state in which it can move back and forth in the axial direction by a predetermined amount within the bar holding hole 145.

[0057] On the other hand, the other end (left side in the figure) of the work holding bar 144 is slidably fitted into a bar holding hole 245 of the work holder 240. In other words, the work holding bar 144 is supported at both ends by the work holder 140 and the work holder 240.

[0058] The joint mounting portion 147 is a portion for mounting the work holder 140 to the joint 131, and is configured as a through hole through which a bolt 148 passes. Four joint mounting portions 147 are formed around the circumferential direction of the work holder body 141 at positions corresponding to the holder mounting portions 136.

[0059] The work holding device 200 includes a clamp base 201, a draw bar 210, a base side hook portion 211, a draw bar operation body 220, a work clamp 230, a joint 231, a work holder 240, a work pressing portion 243, and a bar holding hole 245, which correspond to the clamp base 101, a draw bar 110, a base side hook portion 111, a draw bar operation body 120, a work clamp 130, a joint 131, a work holder 140, a work pressing portion 143, and a bar holding hole 145 in the work holding device 100, respectively.

[0060] (Installation of work holding devices 100, 200) Next, the work of installing the thus configured work holding devices 100, 200 on a machine tool will be described. First, an operator installs the clamp bases 101, 201 of the work holding devices 100, 200 on the spindle or tailstock of the machine tool, respectively. In the work of installing the work holding devices 100, 200 on a machine tool, the work of installing the work holding device 100 and the work of installing the work holding device 200 are the same, so the installation work of the work holding device 100 will be mainly described.

[0061] First, the worker assembles the drawbar 110 and the drawbar operating body 120 to the clamp base 101. Specifically, the worker inserts the drawbar 110 into the drawbar holding portion 105 of the clamp base 101. In this case, the worker positions the drawbar 110 at a position where the first pressure receiving portion 113 of the drawbar 110 communicates with the drawbar holding portion 105 of the drawbar 110.

[0062] Next, the worker inserts the second base fitting portion 122 of the drawbar operating body 120 into the first operating body holding portion 106 of the clamp base 101, and positions it in the second operating body holding portion 107 via the first pressure receiving portion 113 and the relief portion 114 of the drawbar 110. When the first base fitting portion 121 of the drawbar operating body 120 reaches the first operating body holding portion 106 of the clamp base 101, the worker rotates the drawbar operating body 120 to screw the first base fitting portion 121 into the first operating body holding portion 106, thereby inserting the second base fitting portion 122 into the second operating body holding portion 107. In this case, the worker screws the drawbar operating body 120 into the clamp base 101 until the second pressing portion 124 of the drawbar operating body 120 faces the female screw hole 117 of the drawbar 110.

[0063] Next, the worker screws the second pressure receiving portion forming body 115 into the female screw hole 117 of the drawbar 110 to position the second pressure receiving portion 116 relative to the second pressing portion 124, thereby regulating the operation of the reciprocating displacement in the axial direction of the drawbar 110 in response to the rotational operation of the drawbar operating body 120. Specifically, the worker rotates the second pressure receiving portion forming body 115 to adjust the amount of protrusion of the second pressure receiving portion 116 within the relief portion 114, thereby positioning the drawbar operating body 120 relative to the second pressing portion 124.

[0064] More specifically, when the worker rotates (for example, rotates clockwise) the drawbar operating body 120 to insert it into the clamp base 101, as shown in Figure 6(A), the part of the first pressing portion 123 of the drawbar operating body 120 that faces the spindle fitting portion 103 comes into contact with the part of the first pressure receiving portion 113 of the drawbar 110 that is located on the spindle fitting portion 103 side (see dashed circle A in Figure 6(A)), and when the worker rotates (for example, rotates counterclockwise) the drawbar operating body 120 to remove it from the clamp base 101, the part of the second pressing portion 124 of the drawbar operating body 120 that faces the second pressure receiving portion 116 comes into contact with the second pressure receiving portion 116 (see dashed circle C in Figure 6(B)).

[0065] In this case, when the portion of the first pressing portion 123 of the drawbar operating body 120 facing the spindle fitting portion 103 side is in contact with the portion of the first pressure receiving portion 113 of the drawbar 110 located on the spindle fitting portion 103 side (see dashed circle A in FIG. 6(A)), the portion of the first pressing portion 123 facing the clamp fitting portion 104 side is not in contact with the portion of the first pressure receiving portion 113 located on the clamp fitting portion 104 side (see dashed circle B in FIG. 6(A)), the portion of the second pressing portion 124 of the drawbar operating body 120 facing the second pressure receiving portion 116 side is not in contact with the second pressure receiving portion 116 (see dashed circle C in FIG. 6(A)), and the portion of the second pressing portion 124 facing the opposite side to the second pressure receiving portion 116 side is not in contact with the relief portion 114 opposite to the portion facing the opposite side (see dashed circle D in FIG. 6(A)).

[0066] Furthermore, when the portion of the second pressing portion 124 of the drawbar operating body 120 facing the second pressure receiving portion 116 is in contact with the second pressure receiving portion 116 (see dashed circle C in FIG. 6(B)), the portion of the second pressing portion 124 facing the opposite side from the second pressure receiving portion 116 is not in contact with the relief portion 114 facing the portion facing the opposite side (see dashed circle D in FIG. 6(B)), the portion of the first pressing portion 123 of the drawbar operating body 120 facing the spindle fitting portion 103 is not in contact with the portion of the first pressure receiving portion 113 of the drawbar 110 located on the spindle fitting portion 103 side (see dashed circle A in FIG. 6(B)), and the portion of the first pressing portion 123 facing the clamp fitting portion 104 is not in contact with the portion of the first pressure receiving portion 113 located on the clamp fitting portion 104 side (see dashed circle B in FIG. 6(A)).

[0067] As a result, when the clamp base 101 is rotated (for example, rotated clockwise) so as to insert the drawbar operation body 120 into the clamp base 101, the drawbar operation body 120 pushes the drawbar 110 toward the spindle fitting portion 103, and the drawbar 110 is displaced toward the spindle fitting portion 103 (see the dashed arrow in FIG. 6(A)). Also, when the clamp base 101 is rotated (for example, rotated counterclockwise) so as to remove the drawbar operation body 120 from the clamp base 101, the drawbar operation body 120 pushes the drawbar 110 toward the clamp fitting portion 104, and the drawbar 110 is displaced toward the clamp fitting portion 104 (see the dashed arrow in FIG. 6(B)). Then, when the worker has determined the position of the second pressure-receiving portion forming body 115, he or she fixes the position of the second pressure-receiving portion forming body 115 by screwing the set screw 117a into the female threaded hole 117 and pressing the second pressure-receiving portion forming body 115.

[0068] 6(A) and 6(B), in order to facilitate understanding of the operation of the drawbar 110 in response to the operation of the drawbar operation body 120, only the clamp base 101, the drawbar 110, and the drawbar operation body 120 in FIG.

[0069] Next, the worker attaches the clamp base 101, to which the draw bar 110 and the draw bar operating body 120 have been respectively assembled, to the spindle (not shown) of the machine tool. Specifically, the worker fits the spindle fitting portion 103 of the clamp base 101 into the spindle of the machine tool, and then passes the bolt 108a through the spindle mounting portion 108 and tightens it to the spindle to attach it. This allows the worker to attach the clamp base 101 to the spindle with the axis of the clamp base 101 aligned with the axis of the spindle of the machine tool.

[0070] Note that the worker may attach the clamp base 101 to the spindle (not shown) of the machine tool, and then assemble the draw bar 110 and the draw bar operating body 120 to the clamp base 101 attached to the spindle. The worker also attaches the clamp base 201 to the tailstock using the same procedure as for the clamp base 101.

[0071] Next, the worker assembles the work clamp 130 by attaching the work holder 140 to the joint 131. Specifically, the worker inserts the work holding bar 144 into the bar holding hole 145 of the work holder 140 via the coil spring 146a, and screws the retaining bolt 146b into the work holder main body 141 to fit it onto the outer circumferential surface of the work holding bar 144. This allows the worker to attach the work holding bar 144 to the work holder main body 141 in a state where it can freely advance and retreat in the axial direction.

[0072] Next, the worker attaches the work holder 140, to which the work holding bar 144 has been assembled, to the joint 131. Specifically, the worker fits the joint fitting portion 142 of the work holder 140 into the holder fitting portion 135 of the joint 131, and then passes the bolt 148 through the joint mounting portion 147 and tightens it to the holder mounting portion 136 to mount the work holder 140. In this way, the worker can assemble the work clamp 130 by attaching the work holder 140 to the joint 131 with the axis of the work holder 140 aligned with the axis of the joint 131.

[0073] After assembling the work holder 140 to the joint 131, the worker can assemble the work clamp 130 by assembling the work holding bar 144 to the work holder 140 assembled to the joint 131.

[0074] Next, the worker assembles the work clamp 130 to the clamp base 101. Specifically, the worker fits the work-side hook portion 134 of the joint 131 into the base-side hook portion 111 of the draw bar 110, while fitting the base fitting portion 133 of the joint 131 into the clamp fitting portion 104 of the clamp base 101, and rotates the work clamp 130 by about 60°. As a result, the work clamp 130 is loosely attached to the clamp base 101 with the work-side hook portion 134 hooked onto the base-side hook portion 111 of the draw bar 110.

[0075] Next, as shown in Figure 6(A), the worker rotates the drawbar operating body 120 (for example, rotates it clockwise) so as to insert it into the clamp base 101, causing the drawbar operating body 120 to push the drawbar 110 toward the spindle fitting portion 103, thereby displacing the drawbar 110 toward the spindle fitting portion 103. This allows the worker to pull the work clamp 130, which is hooked onto the drawbar 110, toward the spindle fitting portion 103 and press the joint 131 firmly against the clamp base 101, thereby locking the work holder 140 in place on the clamp base 101. In this case, the work clamp 130 can be attached coaxially with the axis of the clamp base 101, i.e., with the axis of the spindle of the machine tool.

[0076] Alternatively, after assembling the joint 131 to the clamp base 101, the worker can also assemble the work holder 140 to the joint 131 assembled to the clamp base 101.

[0077] Next, the worker can attach work holding device 200 to the tailstock of the machine tool using the same procedure as for work holding device 100. In this case, the worker attaches work holding device 200 to the tailstock without inserting work holding bar 144, which is shared with work holding device 100, into bar holding hole 145. As a result, work holding device 200 is attached to the machine tool facing work holding device 100. In this case, work holding device 200 can be attached coaxially with the axis of the tailstock, i.e., coaxially with the axis of the machine tool spindle and the axis of work holding device 100 attached to the spindle.

[0078] (Operation of work holding devices 100, 200) Next, we will explain the operation of the workpiece holding devices 100, 200 configured as described above. First, the worker attaches the workpiece WK, which is an external gear, to the workpiece holding bar 144. Specifically, the worker passes the annular workpiece WK through the workpiece holding bar 144 and positions it on the outer periphery of the workpiece holding portion 144a.

[0079] Next, the worker slides the tailstock of the machine tool toward the spindle side and inserts the workpiece holding bar 144 into the bar holding hole 245, while pressing the workpiece pressing portion 243 against the end face of the workpiece WK held by the workpiece holding bar 144 to sandwich the workpiece WK between the workpiece pressing portions 143 and 243, and then fixes the position of the tailstock. As a result, the workpiece WK is held on the workpiece holding portion 144a of the workpiece holding bar 144 while being sandwiched between the workpiece pressing portions 143 and 243.

[0080] Next, the worker operates the machine tool to grind the workpiece WK. In this case, the machine tool can rotate the workpiece holding devices 100, 200 by rotating the spindle. Since the grinding of the workpiece WK is not directly related to the present invention, a description thereof will be omitted.

[0081] Next, when grinding of the workpiece WK is completed, the worker removes the workpiece WK from the work holding device 100, 200. Specifically, the worker slides the tailstock of the machine tool in a direction away from the spindle to move the work pressing portion 243 away from the end face of the workpiece WK held by the work holding bar 144, and removes the work holding bar 144 from the bar holding hole 245. In this way, the worker can remove the workpiece WK from the work holding device 100, 200 by pulling it out from the work holding bar 144.

[0082] Next, when grinding a workpiece WK with a different shape, the worker replaces the work clamps 130, 230. Specifically, the worker replaces the workpiece holding bar 144 and workpiece holders 140, 240 attached to the machine tool with workpiece holding bar 144 and workpiece holders 140, 240 that correspond to the shape of the workpiece WK to be ground.

[0083] For example, an operator can remove the work clamp 130 of the work holding device 100 attached to the machine tool from the clamp base 101, and then attach a new work clamp 130 to the joint 131 to replace the work clamp 130.

[0084] Specifically, as shown in Fig. 6(B), the worker rotates the drawbar operating body 120 (for example, rotates it counterclockwise) so as to remove it from the clamp base 101, causing the drawbar operating body 120 to push the drawbar 110 toward the clamp fitting portion 104, thereby displacing the drawbar 110 toward the clamp fitting portion 104. As a result, the worker can displace the work clamp 130, which is pressed firmly against the clamp base 101, toward the side away from the spindle fitting portion 103, thereby setting the work clamp 130 to an unlocked state (a state in which the work clamp 130 is loosely attached to the clamp base 101).

[0085] Therefore, the worker can remove the work clamp 130 from the clamp base 101 by rotating the work clamp 130 to release the work-side hook portion 134 from the base-side hook portion 111, and then pulling the work clamp 130 out of the clamp base 101. The worker can then replace the work clamp 130 by attaching a new work clamp 130 to the clamp base 101 using the same procedure as the above-mentioned installation procedure. The worker can also replace the work clamp 230 using the same procedure.

[0086] Furthermore, for example, an operator can loosen the anti-slip bolt 146b on the work holder 140 of the work holding device 100 attached to the machine tool to remove the work holding bar 144 from the bar holding hole 145, and then insert a new work holding bar 144 into the bar holding hole 145 to replace the work holding bar 144.

[0087] Furthermore, an operator can replace the work holders 140, 240 by, for example, reattaching the work holders 140, 240 to the joints 131, 231. Note that the replacement of the work clamps 130, 230, the work holding bar 144, and the work holders 140, 240 can be performed even if the work clamps 130, 230, such as the work holding bar 144, the work holders 140, 240, or the joints 131, are damaged.

[0088] As can be understood from the above description of operation, according to the above embodiment, the work holding devices 100, 200 can fix or detach the work clamps 130, 230 hooked to the base side hook portions 111, 211 to or from the clamp bases 101, 201 by advancing and retreating the draw bars 110, 210 via a draw bar displacement mechanism that displaces the draw bars 110, 210, respectively, thereby facilitating the replacement of the work clamps 130, 230 with the spindle and improving the machining efficiency for multiple types of workpieces WK.

[0089] Furthermore, the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the object of the present invention.

[0090] For example, in the above embodiment, the work clamp 130 is configured by the joint 131 and the work holder 140. However, the work clamp 130 can also be configured by integrally forming the joint 131 and the work holder 140.

[0091] Furthermore, in the above embodiment, the work holding device 100 is configured such that the clamp base 101 is equipped with the clamp fitting portion 104, and the work clamp 130 is equipped with the base fitting portion 133. In this case, the clamp fitting portion 104 and the base fitting portion 133 are formed so that the axis of the work clamp 130 is aligned with the axis of the clamp base 101, i.e., so that the work clamp 130 is coaxial with the clamp base 101. However, since the clamp fitting portion 104 and the base fitting portion 133 only need to be formed so that the work clamp 130 is positioned at a specific position relative to the clamp base 101, they can also be formed so that the axis of the work clamp 130 is aligned at a position different from the axis of the clamp base 101. Furthermore, the work holding device 100 can also be configured without the clamp fitting portion 104 and the base fitting portion 133.

[0092] Furthermore, in the above embodiment, the workpiece holding device 100 is configured so that the drawbar 110 is displaced reciprocally in the axial direction by pressing the drawbar operating body 120 against the first pressure receiving portion 113 and the second pressure receiving portion 116 formed on the drawbar 110, respectively. In other words, the first pressure receiving portion 113, the second pressure receiving portion 116, and the drawbar operating body 120 correspond to the drawbar displacement mechanism according to the present invention. However, the drawbar displacement mechanism only needs to be configured so as to displace the drawbar 110 reciprocally in the axial direction. Therefore, the drawbar displacement mechanism can also be configured by providing, in the machine tool, an actuator such as an electric motor, a hydraulic cylinder, or an air cylinder that drives the drawbar 110 reciprocally in the axial direction.

[0093] In the above embodiment, the first pressure receiving portion 113 is configured by forming a cylindrical surface having a conical surface inside the drawbar 110. The second pressure receiving portion 116 is formed in the second pressure receiving portion forming body 115 configured as a separate body from the drawbar 110. However, the first pressure receiving portion 113 can also be configured by forming it in a rod-shaped first pressure receiving portion forming body (not shown) configured as a separate body from the drawbar 110, like the second pressure receiving portion 116. The second pressure receiving portion 116 can also be configured by forming a cylindrical surface having a conical surface inside the drawbar 110, like the first pressure receiving portion 113.

[0094] In the above embodiment, the drawbar operation body 120 is configured as a doubly supported body in which both ends are supported by the first operation body holding portion 106 and the second operation body holding portion 107 formed in the clamp base 101. However, the drawbar operation body 120 can also be configured as a cantilever supported body in which it is supported by fitting only the first operation body holding portion 106 formed in the clamp base 101.

[0095] Furthermore, in the above embodiment, the relief portion 114 from which the second pressure receiving portion 116 protrudes is formed by shifting the axis C114 with respect to the axis C113 of the first pressure receiving portion 113 formed of a cylindrical surface toward the side where the drawbar 110 is locked. This makes it possible for the work holding device 100 to make it difficult for the relief portion 114 to come into contact with the drawbar operating body 120 when the first pressure receiving portion 113 is in contact with the drawbar operating body 120.

[0096] However, the relief portion 114 can also be formed by shifting it toward the side where the drawbar 110 is unlocked with respect to the axis of the first pressure-receiving portion 113. This makes it possible for the work holding device 100 to make it difficult for the relief portion 114 to come into contact with the drawbar operating body 120 when the second pressure-receiving portion 116 is in contact with the drawbar operating body 120.

[0097] In other words, the escape portion 114 is formed with its axis C114 at a different position relative to the axis C113 of the cylindrical surface constituting the first pressure receiving portion 113, thereby making it possible to change the contact or non-contact relationship of the escape portion 114 with the drawbar operating body 120 when the first pressure receiving portion 113 is in contact with the drawbar operating body 120, or the contact or non-contact relationship of the cylindrical surface constituting the first pressure receiving portion 113 with the drawbar operating body 120 when the second pressure receiving portion 116 is in contact with the drawbar operating body 120.

[0098] In the above embodiment, the workpiece WK is an external gear. However, the workpiece WK may be a gear other than an external gear, or a part other than a gear.

[0099] In the above embodiment, the machine tool is a grinding machine, but the machine tool may be a device that performs machining such as cutting or grinding on the workpiece WK.

[0100] Furthermore, in the above embodiment, the machine tool is configured such that the work holding device 100 is attached to the spindle and the work holding device 200 is attached to the tailstock to support the work holding bar 144 at both ends. However, the machine tool can also be configured such that the work holding device 200 is omitted and the workpiece WK is supported at one end by the work holding device 100 attached to the spindle alone. [Explanation of symbols]

[0101] WK...workpiece, C113...axis center of the first pressure receiving portion 113, C114...axis center of the relief portion 114, 100...Work holding device, 101... clamp base, 102... clamp base body, 103... main shaft fitting portion, 104... clamp fitting portion, 105... draw bar holding portion, 106... first operating body holding portion, 107... second operating body holding portion, 108... main shaft mounting portion, 108a... bolt, 110...draw bar, 111...base side hook portion, 112...operation body fitting hole, 113...first pressure receiving portion, 114...relief portion, 115...second pressure receiving portion forming body, 116...second pressure receiving portion, 117...female thread hole, 117a...set screw, 120...drawbar operating body, 121...first base fitting portion, 122...second base fitting portion, 123...first pressing portion, 124...second pressing portion, 125...operating portion, 130... work clamp, 131... joint, 132... joint body, 133... base fitting portion, 134... work side hook portion, 135... holder fitting portion, 136... holder mounting portion, 140...work holder, 141...work holder main body, 142...joint fitting portion, 143...work pressing portion, 144...work holding bar, 144a...work holding portion, 145...bar holding hole, 146a...coil spring, 146b...withdrawal prevention bolt, 147...joint mounting portion, 148...bolt, 200...Work holding device, 201...Clamp base, 210...Draw bar, 211...Base side hook portion, 220...Draw bar operating body, 230...Work clamp, 231...Joint, 240...Work holder, 243...Work pressing portion, 245...Bar holding hole.

Claims

1. A workpiece holding device that holds a workpiece on the rotation center axis of a spindle of a machine tool, a clamp base attached to the spindle; a work clamp having a work-side hook portion that can be detachably hooked onto the clamp base and that detachably holds the workpiece; The clamp base is a draw bar having a base-side hook portion on which the work-side hook portion is hooked, the base-side hook portion being fitted within the clamp base so as to be slidable in two directions, that is, a direction in which the base-side hook portion moves away from the clamp base and a direction in which the base-side hook portion moves toward the clamp base; a draw bar displacement mechanism that reciprocates the draw bar in the two directions within the clamp base.

2. 2. The workpiece holding device according to claim 1, The clamp base is A clamp fitting portion into which the work clamp is detachably fitted, The work clamp is A workpiece holding device comprising a base fitting portion that is detachably fitted to the clamp fitting portion.

3. 2. The workpiece holding device according to claim 1, The drawbar displacement mechanism includes: a drawbar operating body that is fitted into the clamp base from an outer surface thereof so as to be able to move forward and backward; a first pressure receiving portion provided on the drawbar and pressed by the drawbar operating body to displace the drawbar to one side in the reciprocating displacement; a second pressure receiving portion provided on the draw bar and pressed by the draw bar operating body to displace the draw bar to the other side of the reciprocating displacement.

4. 4. The workpiece holding device according to claim 3, The drawbar operating body is formed in a rod shape, The drawbar is an operating body fitting hole formed in a hole shape into which the drawbar operating body is fitted, The first pressure receiving portion and the second pressure receiving portion are A workpiece holding device characterized in that the workpiece holding members are provided on opposite sides of the inner periphery of the operating body fitting hole.

5. 5. The workpiece holding device according to claim 4, The drawbar operation body is A workpiece holding device characterized in that both end sides of the draw bar operating body pass through the operating body fitting hole and fit into the clamp base.

6. 5. The workpiece holding device according to claim 4, The first pressure receiving portion is The operating body fitting hole is formed on an inner peripheral surface of a cylindrical surface, The second pressure receiving portion is The operating body is configured to protrude from a cylindrical surface formed in the operating body fitting hole, The cylindrical surface from which the second pressure receiving portion protrudes is A workpiece holding device characterized in that the first pressure receiving portion is formed with its axis at a different position from the axis of the cylindrical surface constituting the first pressure receiving portion.

7. 4. The workpiece holding device according to claim 3, A workpiece holding device, wherein at least one of the first pressure receiving portion and the second pressure receiving portion is configured as a separate body from the draw bar.

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