JP2019014017A - Tool clamp device - Google Patents

Abstract

To provide a tool clamp device which can accurately grasp deterioration of tool clamp force resulting from time degradation of a biasing member.SOLUTION: A tool clamp device includes: a draw bar 11 which switches clamp/unclamp states of a tool holder 20 which holds a tool 17; a biasing member 12 which biases the draw bar 11 in a clamp direction of the tool holder 20; a cylinder 13 which pushes the draw bar 11 in an unclamp direction of the tool holder 20 against biasing force of the biasing member 12; and a hydraulic mechanism 14 which has a hydraulic selector function, which can selectively generate a first hydraulic pressure being a hydraulic pressure generated when normal unclamping is performed and a second hydraulic pressure which is lower than the first hydraulic pressure, and drives the cylinder 13.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a tool clamp device for a machine tool such as a machining center, and more particularly to a tool clamp device having a tool clamp force measuring mechanism.

  A tool clamping device of a machine tool such as a machining center attaches a tool to a tool holder such as a collet, and biases a main shaft connected to the tool holder with a biasing force of a biasing member such as a disc spring. The clamp is held with the tool held by the holder. On the other hand, the tool is brought into an unclamped state by moving the main shaft in the axial direction against the urging force of the urging member.

  The clamping force of the tool by the tool holder is generated based on the biasing force of the biasing member. When the urging member is in a new state, an urging force of a predetermined magnitude is applied by the urging member, and a clamping force large enough to hold the tool can be ensured. On the other hand, when the urging member deteriorates with time, the urging force of a predetermined magnitude by the urging member cannot be exhibited, and a clamping force of a predetermined magnitude cannot be ensured. If the clamping force is insufficient, the tool clamped by the tool holder may be shaken, resulting in problems such as a reduction in processing accuracy or damage to the tool.

  In order to solve this problem, for example, in the spindle device of a machine tool according to Patent Document 1, the collet is based on the rod pressing force detected by the rod pressing force detection means and the rod displacement detected by the rod displacement detection means. The clamping force due to is detected. Then, based on the change with time of the clamping force of the tool, the replacement time determination means determines the replacement time of the urging means (see paragraph 0019 of Patent Document 1).

  In the tool clamping force measuring device according to Patent Document 2, the piston rod is driven by the hydraulic pressure from the hydraulic source, and when the unclamping operation is performed, the pressing force acting on the draw bar from the piston rod is detected by the load cell. The spring replacement time is grasped (see paragraphs 0007 and 0015 of Patent Document 2).

Japanese Patent No. 4638464 Japanese Patent Laid-Open No. 10-291105

  In the configuration according to Patent Document 1, a hydraulic pressure is generated by a hydraulic control device to operate a driving device, but the magnitude of this hydraulic pressure is considered to be equivalent to that when the tool is unclamped. Since the hydraulic pressure for unclamping needs to be performed quickly against the urging force of the urging member, the hydraulic pressure is usually sufficiently larger than the urging force. In this case, an error between the hydraulic pressure at the moment of unclamping the tool and the actually measured hydraulic pressure becomes large, and there is a possibility that an error occurs in the life prediction of the biasing member.

  Also, in the configuration according to Patent Document 2, the piston rod is driven by the hydraulic pressure from the hydraulic power source. Like the hydraulic control device according to Patent Document 1, the magnitude of the hydraulic pressure unclamps the tool. It is considered to be a sufficiently large hydraulic pressure equivalent to the time. For this reason, there is a concern that an error may occur in grasping the disc spring replacement time. In addition, when a load cell is provided on the main shaft side which is a rotating body, there is a possibility that problems such as heat generation due to friction and rotation loss may occur when the pressing force is detected.

  Therefore, an object of the present invention is to accurately grasp the decrease in the tool clamping force accompanying the aging member deterioration with time.

  In order to solve the above-described problems, in the present invention, a draw bar that switches a clamp / unclamp state of a tool holder that holds a tool, and a biasing member that biases the draw bar toward the clamping direction of the tool holder, A cylinder that pushes the draw bar toward the unclamping direction of the tool holder against the urging force of the urging member, a first hydraulic pressure that is a hydraulic pressure when performing normal unclamping, and the first And a hydraulic mechanism for driving the cylinder, which has a hydraulic pressure switching function capable of selectively generating a second hydraulic pressure lower than the hydraulic pressure.

  In the above configuration, the second hydraulic pressure is a hydraulic pressure when a tool clamping force is measured from the biasing force of the biasing member, and the hydraulic pressure switching function is performed when the tool clamping force is measured. It is preferable that hydraulic pressure is supplied to the cylinder.

  In each of the above-described configurations, it is preferable that a displacement meter is provided that measures the amount by which the draw bar is pushed in the axial direction by the cylinder in a non-contact manner.

  In each of the above configurations, it is preferable that the second hydraulic pressure is in a range of 10 to 30% of the first hydraulic pressure.

  In each of the above configurations, it is preferable that the hydraulic mechanism generates the second hydraulic pressure in a state where the tool is not clamped by the tool holder.

  In the present invention, the hydraulic mechanism can selectively generate a first hydraulic pressure that is a hydraulic pressure when performing normal unclamping and a second hydraulic pressure that is lower than the first hydraulic pressure. For this reason, even in a region where the displacement amount of the urging member is small, it is possible to accurately grasp the decrease in the tool clamping force accompanying the deterioration of the urging member with time. Thereby, management of a tool clamp apparatus is made easy and the trouble accompanying the malfunction of an apparatus can be avoided as much as possible.

Sectional drawing which shows the clamped state of the tool clamp apparatus which concerns on this invention The figure which shows the solenoid switching state of the hydraulic mechanism in a clamped state Sectional drawing which shows the unclamp state of the tool clamp apparatus which concerns on this invention The figure which shows the solenoid switching state of the hydraulic mechanism in an unclamped state Sectional drawing which shows the clamp force measurement state of the tool clamp apparatus concerning this invention The figure which shows the solenoid switching state of the hydraulic mechanism in the clamp force measurement state The figure which shows the relationship between the amount of spring contraction and cylinder oil pressure in the low oil pressure region The figure which shows the relationship between the amount of spring contractions and crank force derived | led-out from the relationship shown in FIG.

  A clamp state of the tool clamp device 10 according to the present invention will be described with reference to FIGS. The tool clamp device 10 is applied to a machine tool such as a machining center, and includes a draw bar 11, an urging member 12, a cylinder 13, and a hydraulic mechanism 14 as main components.

  The draw bar 11 is provided in the hollow cylindrical main shaft 15 so as to be movable in the axial direction. A clamping cone 16 is connected to the end of the draw bar 11 on the tool mounting side. The clamping cone 16 includes a small-diameter portion 16a formed on the connection side with the draw bar 11, a large-diameter portion 16b formed on the tool 17 side with respect to the small-diameter portion 16a, and a small-diameter portion 16b. It is located between the portion 16a and the large diameter portion 16b, and has an outer diameter changing portion 16c whose outer diameter continuously changes from the outer diameter of the small diameter portion 16a to the outer diameter of the large diameter portion 16b. .

  The clamping cone 16 is movable in the axial direction integrally with the draw bar 11, and is driven around a shaft integrally with the draw bar 11 by driving a motor (not shown) provided on the main shaft 15. It can be rotated. The draw bar 11 is provided with a displacement meter 18 that measures the amount of pushing of the draw bar 11 in the axial direction by the cylinder 13 (corresponding to the amount of contraction of the biasing member 12) in a non-contact manner.

  A cylindrical holding member 19 is fitted at the tip of the main shaft 15. On the inner diameter surface of the holding member 19, a tapered surface 19 a that increases in diameter toward the tip end side is formed. A tool holder 20 to which the tool 17 is fixed is attached to the holding member 19. The tool holder 20 is formed with a tapered surface 20a that can come into contact with the tapered surface 19a formed on the holding member 19.

  A gripper 21 is provided on the inner diameter side of the holding member 19. The gripper 21 includes a plurality of arms 21a divided in the circumferential direction that can be expanded and contracted in the radial direction. A grip portion 21b that protrudes radially outward is formed on the distal end side of the arm 21a.

  The urging member 12 has a function of urging the draw bar 11 toward the clamping direction of the clamping cone 16 (the direction of the white arrow in FIG. 1). The arm 21a of the gripper 21 is in a state of being reduced in diameter along the small diameter portion 16a of the clamping cone 16 in the unclamped state of the tool holder 20 (see FIG. 3).

  On the other hand, when the draw bar 11 is drawn by the urging force of the urging member 12, the clamping cone 16 is drawn together with the draw bar 11. Then, the tip of the arm 21 a is guided by the outer diameter changing portion 16 c formed on the clamping cone 16, and the arm 21 a is smoothly expanded in diameter along the large diameter portion 16 b of the clamping cone 16. As the diameter increases, the grip portion 21b comes into strong contact with the inner diameter surface of the tool holder 20 to exert a clamping force (see FIG. 1).

  Due to this clamping force, the tapered surfaces 19 a and 20 a formed on the holding member 19 and the tool holder 20 come into strong contact with each other, and the tool holder 20 (tool 17) is reliably clamped by the holding member 19. Thus, the clamp / unclamp state of the tool holder 20 holding the tool 17 can be switched in accordance with the operation of the draw bar 11. In this embodiment, a plurality of disc springs (in the following, the same reference numerals as those of the urging member 12) are employed as the urging member 12 in the axial direction.

  The cylinder 13 has a function of pushing the draw bar 11 in the unclamping direction of the clamping cone 16 (the direction of the white arrow in FIG. 3 described later) against the urging force of the disc spring 12. As shown in FIG. 2, the cylinder 13 is provided with a partition wall 22 that divides the internal space, and an unclamp chamber 23 and a clamp chamber 24 are formed by the partition wall 22.

  When the hydraulic oil is supplied to the unclamping chamber 24, the draw bar 11 is pushed in the unclamping direction, and the tool holder 20 can be detached from the holding member 19 (see FIG. 3). On the other hand, when the supply of the hydraulic oil to the unclamping chamber 23 is canceled, the tool holder 20 can be held in the clamped state by the holding member 19 by the biasing force of the disc spring 12 (see FIG. 1).

  The hydraulic mechanism 14 is a member for driving the cylinder 13. The hydraulic mechanism 14 includes a first hydraulic pressure (for example, 5 MPa; hereinafter, the first hydraulic pressure is referred to as a normal hydraulic pressure) that is a hydraulic pressure when performing normal unclamping, and an urging force of the disc spring 12. The second hydraulic pressure lower than the normal hydraulic pressure (for example, 1 MPa. In the following, the second hydraulic pressure is referred to as a measurement hydraulic pressure), which is a hydraulic pressure for measuring the tool clamping force. It has a hydraulic pressure switching function that can occur. The piping from the hydraulic mechanism 14 is connected to the unclamp chamber 23 and the clamp chamber 24 of the cylinder 13, respectively.

  As shown in FIG. 2, the hydraulic mechanism 14 includes an oil tank 25 that stores hydraulic oil, an oil pump 26 that circulates hydraulic oil, a first solenoid 27, a second solenoid 28, a pressure reducing valve 29, a check valve 30, In addition, a check valve control flow path 31 is provided. From this oil tank 25, piping is provided so that hydraulic oil can be supplied not only to the cylinder 13 shown in FIG. 2 but also to a cylinder (not shown) of another tool clamp device.

  The first solenoid 27 is formed with three types of flow paths that switch the direction in which the hydraulic oil flows in accordance with the unclamped or clamped state. The second solenoid 28 is formed with two types of flow paths for switching the flow of hydraulic oil when measuring the tool clamping force. The pressure reducing valve 29 is provided in the second solenoid 28, and the pressure of the hydraulic oil passing through the second solenoid 28 is reduced from the normal pressure to the measurement pressure.

  The check valve 30 acts to prevent the hydraulic oil from flowing out from the unclamp chamber 23 while allowing the hydraulic oil to be supplied to the unclamp chamber 23. The check valve control flow path 31 connects the supply valve to the clamp chamber 24 and the check valve 30. Then, when the check valve 30 is closed, the check valve 30 is opened by applying the hydraulic pressure of the supply-side flow path to the clamp chamber 24 to the check valve 30, and the hydraulic fluid from the unclamp chamber 23 is allowed to flow out. To do.

  In the clamped state shown in FIG. 1, the solenoids 27 and 28 of the hydraulic mechanism 14 are switched as shown in FIG. At this time, the hydraulic oil supplied from the oil tank 25 is supplied to the clamp chamber 24 side via the first solenoid 27. Further, due to the presence of the check valve control flow path 31, the check valve 30 is opened by the pressure of the hydraulic oil flowing through the supply-side flow path to the clamp chamber 24, and the hydraulic oil in the unclamp chamber 23 To the oil tank 25 through the check valve 30. The partition 22 between the unclamp chamber 23 and the clamp chamber 24 is moved toward the unclamp chamber 23 by the biasing force of the disc spring 12. In this clamped state, the flow path passing through the second solenoid 28 is blocked. A transmission member 32 is interposed between the partition wall 22 and the draw bar 11. The transmission member 32 moves the partition wall 22 and the draw bar 11 integrally in the axial direction.

  An unclamped state of the tool clamp device 10 according to the present invention will be described with reference to FIGS. In the unclamped state, the draw bar 11 is pushed in the unclamping direction (see the white arrow in FIG. 3) against the biasing force of the disc spring 12, and the grip portion 21 b strongly contacts the inner diameter surface of the tool holder 20. The generated clamping force is released. As the clamping force is released, the contact between the tapered surfaces 19a and 20a formed on the holding member 19 and the tool holder 20 is eliminated, and the tool holder 20 can be removed from the holding member 19 (see FIG. 3). ).

  In the unclamped state shown in FIG. 3, the solenoids 27 and 28 of the hydraulic mechanism 14 are switched as shown in FIG. That is, the hydraulic oil supplied from the oil tank 25 is supplied to the unclamping chamber 23 side via the first solenoid 27. Thereby, the partition wall 22 between the unclamp chamber 23 and the clamp chamber 24 moves to the clamp chamber 24 side against the biasing force of the disc spring 12.

  At this time, the hydraulic oil in the clamp chamber 24 is returned to the oil tank 25 through the pipe. The hydraulic pressure of the hydraulic oil supplied to the unclamping chamber 23 is a normal hydraulic pressure (for example, 5 MPa) that is sufficient to quickly bring the tool holder 20 into the unclamped state. In this unclamped state, the flow path passing through the second solenoid 28 is blocked.

  A clamp force measurement state of the tool clamp device 10 according to the present invention will be described with reference to FIGS. The clamping force measurement state is the point where the draw bar 11 is pushed in the unclamping direction (the white arrow direction in FIG. 5) against the urging force of the disc spring 12, as in the unclamping state described in FIGS. However, the size of the hydraulic pressure for the pushing is set to a measurement hydraulic pressure (for example, 1 MPa) lower than the normal hydraulic pressure (for example, 5 MPa) applied in the unclamped state. Different.

  In the clamping force measurement state shown in FIG. 5, the solenoids 27 and 28 of the hydraulic mechanism 14 are switched as shown in FIG. That is, the hydraulic oil supplied from the oil tank 25 is supplied to the unclamping chamber 23 side via the pressure reducing valve 29 and the second solenoid 28. At this time, since there is no hydraulic oil acting on the check valve 30 via the first solenoid 27, the check valve 30 is closed. Therefore, the entire amount of hydraulic oil that has passed through the pressure reducing valve 29 and the second solenoid 28 is supplied to the unclamping chamber 23 side without passing through the check valve 30. Thereby, the partition wall 22 between the unclamp chamber 23 and the clamp chamber 24 moves to the clamp chamber 24 side against the biasing force of the disc spring 12. At this time, the hydraulic oil in the clamp chamber 24 is returned to the oil tank 25 through the pipe.

  Since the measurement hydraulic pressure supplied to the unclamping chamber 20 in this clamping force measurement state is sufficiently lower than the normal hydraulic pressure, both the pressing amount and the pressing speed of the draw bar 11 are both the pressing amount and the pressing speed in the unclamping operation performed with the normal hydraulic pressure. Smaller than. For this reason, it is possible to accurately detect the state of deterioration of the disc spring 12 with time in a region where the amount of spring contraction is small (around the minimum and maximum amount of spring contraction).

  When the reproducibility test of the amount of contraction of the disc spring 12 when this measurement hydraulic pressure was applied, the measurement hydraulic pressure was 10-30% larger than the normal hydraulic pressure at the time of unclamping. The amount of spring contraction is as shown in FIG. 7, particularly when it is within the range of 15 to 25% (within the range indicated by F in FIG. 7). The relationship between x and the cylinder oil pressure F could be derived with good reproducibility.

  Note that it is not preferable that the measurement hydraulic pressure is smaller than 10% of the normal hydraulic pressure because the spring contraction amount x may not be accurately measured due to play of the apparatus or the like. Further, it is not preferable that the measurement hydraulic pressure is larger than 30% of the normal hydraulic pressure because the possibility of a decrease in measurement reproducibility increases.

  For the relationship between the spring contraction amount x and the cylinder hydraulic pressure F, the basic formula of spring dynamics represented by the formula (1) is used. Further, here, the clamping force f and the cylinder hydraulic pressure F are associated with each other in consideration of the wedge effect that occurs when the grip portion 21b expressed by the mathematical formula (2) strongly contacts the inner diameter surface of the tool holder 20. Here, k is a spring constant, and e is a constant based on the wedge effect. The constant e is a value larger than 1, and the wedge effect can generate a clamping force larger than the urging force (repulsive force) by the disc spring 12.

(Formula)
F = kx (1)
F = f / e (2)

  When the spring constant k decreases as the disc spring 12 deteriorates with time, the amount of spring contraction x with respect to the same cylinder hydraulic pressure F increases. Here, the spring constant k is derived by detecting the amount of spring contraction x with the displacement meter 18. Further, based on the spring constant k derived from the relationship between the amount of spring contraction x and the cylinder hydraulic pressure F shown in FIG. 7, the contact state between the grip portion 21b and the inner diameter surface of the tool holder 20 is considered, As shown in FIG. 8, the clamping force f during actual clamping was calculated.

From Figure 8, when the contraction amount of the belleville spring 12 in the clamped condition of the tool holder 20 is for example a, the clamping force generated at that time becomes f _a. The clamp force f _a, is compared with the control reference value of the clamping force of the tool clamping device 10, the smaller the better clamping force f _a than control reference value, replacement timing of the disc springs 12 is reached Can be determined.

  The measurement of the clamping force is preferably performed periodically at a predetermined time interval (for example, at the start of each work). In this way, deterioration with time of the disc spring 12 can be reliably detected. Further, the measurement of the clamping force is preferably performed in the unclamped state of the tool holder 20 as shown in FIG. In this way, it is possible to prevent the tool holder 20 from dropping off from the holding member 19 when the measurement hydraulic pressure is applied to the cylinder 13.

  The above embodiment is merely an example, and as long as the problem of the present invention of accurately grasping the decrease in the tool clamping force accompanying the deterioration of the biasing member 12 with time can be solved, the constituent members of the tool clamping device 10 It is possible to appropriately change the above-described constituent elements, such as changing the shape and arrangement of the above, or changing the configuration of the piping of the hydraulic mechanism 14.

10 Tool Clamp Device 11 Draw Bar 12 Biasing Member (Belleville Spring)
13 Cylinder 14 Hydraulic mechanism 15 Main shaft 16 Clamping cone 16a Small diameter portion 16b Large diameter portion 16c Outer diameter changing portion 17 Tool 18 Displacement meter 19 Holding member 19a Tapered surface 20 Tool holder 20a Tapered surface 21 Gripper 21a Arm 21b Grip portion 22 Bulkhead 23 Unclamping chamber 24 Clamping chamber 25 Oil tank 26 Oil pump 27 First solenoid 28 Second solenoid 29 Pressure reducing valve 30 Check valve 31 Flow path 32 for check valve control Transmission member

Claims (5)

A draw bar that switches between the clamp and unclamp states of the tool holder that holds the tool;
A biasing member that biases the draw bar toward the clamping direction of the tool holder;
A cylinder that pushes the draw bar toward the unclamping direction of the tool holder against the urging force of the urging member;
A hydraulic mechanism for driving the cylinder, which has a hydraulic pressure switching function capable of selectively generating a first hydraulic pressure that is a hydraulic pressure for performing normal unclamping and a second hydraulic pressure that is lower than the first hydraulic pressure. When,
Tool clamping device with The second hydraulic pressure is a hydraulic pressure when measuring a tool clamping force from an urging force of the urging member,
The tool clamp apparatus according to claim 1, wherein the hydraulic pressure switching function supplies the second hydraulic pressure to the cylinder when measuring a tool clamp force. The tool clamp device according to claim 1 or 2, further comprising a displacement meter that measures the amount of pushing of the draw bar in the axial direction by the cylinder in a non-contact manner. 4. The tool clamp device according to claim 1, wherein the second hydraulic pressure is within a range of 10 to 30% of the first hydraulic pressure. 5. The tool clamping device according to any one of claims 1 to 3, wherein the hydraulic mechanism generates the second hydraulic pressure in a state where the tool holder is not clamped.

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