JP2002052406A - Spindle apparatus with automatic tool changing function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discriminate miss grasping regardless of an unclamp form, and discriminate without the problem of unbalance in high speed rotation. SOLUTION: A clamp mechanism 9 of a tool 8 is provided at the tip of a spindle 4. In the clamp mechanism 9, a draw bar 11 is pushed by a push rod 14 of the unclamp unit 13 in the rear of the spindle to unclamp a tool. A detecting means 6 for detecting the trailing end of the draw bar 11 is housed in the tip of the push rod 14. According to the detection signal of the detecting means 16, miss grasping for the tool is discriminated. This apparatus is applied also to the case of using a hydrostatic magnetic composite bearing for bearings 2, 3 supporting the spindle 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle device provided in a high-speed cutting device, a grinding device, or the like having an ATC mechanism, and more particularly, to an improvement in detection of an empty grip of a tool at the tip of a spindle.

[0002]

2. Description of the Related Art In a spindle device provided with an automatic tool change mechanism (ATC mechanism), a clamp mechanism is provided at the tip of a main spindle, in which a tool shank is pushed in so that a tool is gripped by a spring force. . The clamp mechanism performs unclamping by pushing the rear end of the draw bar that has penetrated the main shaft with the push rod of the unclamping unit.
The drawbar is generally pushed through a cylinder member arranged behind it. In such a spindle device, in order to prevent empty gripping of the tool, it is performed to detect the position of the drawbar and determine whether or not the gripping of the tool is normally performed. When an empty grip of the tool occurs, the drawbar is further pushed by a spring member for gripping the tool toward a push rod side of the unclamping unit from a normal position (a state where the clamp mechanism grips the tool). Therefore, conventionally, a sensor target is attached to a cylinder member behind the drawbar, and the position of the drawbar is measured from the side by a proximity sensor or the like.

[0003]

As an unclamping unit, there is a unit provided with a main shaft rear end engaging mechanism that engages with the outer periphery of the main shaft rear end during unclamping to prevent the main shaft from moving toward the front end side. A clamp mechanism using this type of unclamping unit is excellent in reducing the bearing axial load during unclamping. However, when a type that engages with the outer periphery of the rear end of the spindle is used as the unclamping unit, there is no place to install a sensor for detecting the drawbar position, and it is difficult to judge the empty grip.

Further, in the case where the sensor target is provided on the side surface of the drawbar or the cylinder member, there is a problem that imbalance of the spindle weight occurs and vibration occurs at high speed rotation. In particular, when the main shaft is supported by a non-contact bearing such as a magnetic bearing, the above imbalance has a large effect on vibration. Therefore, even when a hybrid non-contact bearing in which the following static pressure gas bearing and magnetic bearing are combined is used, the influence on the vibration is large. That is, in order to perform high-efficiency and high-accuracy machining, a spindle device that can rotate at high speed, has high rotational accuracy, and has high static rigidity and high dynamic rigidity is required. In response to this demand, a hybrid non-contact bearing in which a hydrostatic gas bearing and a magnetic bearing are combined has been proposed (Japanese Patent Application No. 10-097550). According to this, it is possible to provide a compact bearing that utilizes the characteristics of both bearings, that is, excellent dynamic rigidity and rotational accuracy of the hydrostatic gas bearing, and excellent static rigidity of the magnetic bearing. However, since a non-contact bearing is used, it is difficult to avoid the influence of vibration when the imbalance of the spindle weight due to the sensor target as described above occurs.

SUMMARY OF THE INVENTION An object of the present invention is to provide a spindle with an automatic tool changing function that can detect an empty grip by detecting a drawbar position regardless of the type of an unclamping unit and does not cause an unbalance problem at high speed rotation. It is to provide a device. Another object of the present invention is to enable discrimination between a normal clamping state and a half-grasping state.
It is still another object of the present invention to be able to detect a drawbar position and determine an empty grip even when an unclamping unit having a main shaft rear end engaging mechanism is used. Still another object of the present invention is to make it possible to discriminate an empty grip without obtaining a problem of generation of vibration due to unbalance of the spindle while obtaining excellent dynamic rigidity, rotation accuracy, and static rigidity by the hydrostatic magnetic composite bearing. It is to be.

[0006]

According to the present invention, a spindle device having an automatic tool changing function supports a main shaft via a housing through a bearing, and a clamp mechanism is provided at a tip of the main shaft.
This clamp mechanism clamps the tool by the backward biasing force of the drawbar that penetrates the inside of the spindle by the tool being pushed into the tip of the spindle, and presses the rear end of the drawbar with a push rod to push the clamp mechanism. The housing is provided with an unclamping unit for setting an unclamping state, and the clamping mechanism is applied to a unit in which the rear end position of the drawbar is rearward in the idle gripping state rather than the tool gripping state. In this spindle device, detection means for detecting the rear end of the drawbar is incorporated at the tip of the push bar of the unclamping unit, and the gripping state of the tool is determined based on a detection signal of the detection means. And According to this configuration, when the tool is correctly grasped by the clamp mechanism at the tip of the spindle, the rear end of the drawbar is far from the detecting means built in the tip of the push rod, and the drawbar is not detected or the drawbar position is far. Is detected by the detection means. When the tool causes an empty grip by the clamp mechanism, the rear end of the drawbar is close to the detection means built in the tip of the push rod, and the drawbar is detected or the drawbar position is detected to be close. Therefore, it can be determined from the detection signal of the detection means that the gripping state of the tool is the empty gripping. Since the detection means is built into the tip of the push rod, the drawbar position can be detected even when the arrangement space of the detection means cannot be obtained near the outer periphery of the rear end of the main spindle by the unclamping unit or the like. Further, since the detection means is built in the tip of the push rod, it is not necessary to provide a sensor target in a member such as a drawbar which rotates together with the main shaft. Therefore, even during high-speed rotation of the main shaft, stable rotation can be obtained without generating vibration.

In the present invention, the detecting means may protrude from the distal end surface of the push rod so as to be freely retractable, and may be arranged so as to be biased to project toward the distal end side of the push rod. The clamp mechanism at the tip of the spindle
A semi-grabbing condition can occur, which is an incomplete clamping condition where the tool is not fully pushed in. Since the difference in the drawbar position between the normal clamping state and the half-grasping state is slight, it is necessary to accurately detect the distance between the detecting means and the rear end of the drawbar in order to determine the difference. In addition, the detection distance of the detection means is shortened due to a demand for miniaturization for incorporating the detection means into the push rod. In order to meet such technical requirements, in the case of this configuration, the detection means can detect the rear end of the drawbar closer to the rear end of the drawbar than the push rod. Therefore, even if the distance detectable by the detecting means is short, the rear end of the drawbar can be detected, and the normal clamp state and the half-grasping state can be determined.

In the present invention, the detecting means may detect the rear end of the drawbar via a cylinder member arranged in contact with the rear end surface of the drawbar. Also,
In the present invention, the unclamping unit may have a main shaft rear end engaging mechanism that engages with a rear end outer periphery of the main shaft at the time of unclamping to prevent the main shaft from moving toward the front end side.

In the present invention, the bearing may be a radial-type hydrostatic composite bearing in which a hydrostatic gas bearing and a magnetic bearing are combined. As described above, when the hydrostatic composite bearing is used, it is possible to provide a compact bearing that utilizes the advantages of both the dynamic rigidity and rotational accuracy of the hydrostatic gas bearing and the superior static rigidity of the magnetic bearing. Since the hydrostatic magnetic composite bearing is a non-contact bearing, it is easily affected by the bias of the spindle weight.However, since the detecting means for discriminating the idle grip is built into the tip of the unclamping push rod, it is biased to the spindle. There is no need to provide a sensor target, while using a non-contact bearing,
An empty grip can be determined without adversely affecting the operation.

In the present invention, the detecting means may be a proximity switch for magnetically detecting displacement. Proximity switches are often small, lightweight, inexpensive, and have excellent accuracy, and are preferable as detection means built in a small push rod of an unclamping unit.

[0011]

FIG. 1 shows a first embodiment of the present invention.
This will be described with reference to FIG. First, the overall outline is shown in FIG.
It is explained together with. The spindle device with an automatic tool changing function is used, for example, as a spindle head of a high-speed cutting device or a grinding device. The spindle device includes a housing 1 having a radial bearing 2 and a thrust bearing 3.
And a spindle drive source 5 is supported. The spindle drive source 5 is a motor built in the housing 1 and includes a rotor 6 provided integrally with the main shaft 4 and a stator 7 provided in the housing 1 to constitute a built-in motor type spindle device. A clamp mechanism 9 for a tool 8 is provided at the tip of the main shaft 4. The clamp mechanism 9 is capable of exchanging the tool 8 by an automatic tool exchanging device (ATC device) 10. The automatic tool changing device 10 performs insertion and removal of the tool 8 with respect to the spindle 4 and movement of the tool 8.

The clamp mechanism 9 includes a tool 8 at the tip of the spindle 4.
Is pushed in, the drawbar 1 penetrates through the main shaft 4.
The tool 8 is clamped by the backward biasing force of the first spring member 12. An unclamping unit 13 is provided behind the main shaft 4 in the housing 1. The unclamping unit 13 includes a push rod 14 driven forward and backward.
By pressing the rear end of the draw bar 11, the clamp mechanism 9 is brought into an unclamped state. Push rod 14
Is a cylinder member 15 disposed at the rear end of the drawbar 11.
Push the drawbar 11 via. Unclamp unit 1
Reference numeral 3 denotes a main shaft rear end engagement mechanism 20 which engages with the outer periphery of the rear end of the main shaft 4 during unclamping to prevent the main shaft 4 from moving toward the front end.
Having. At the tip of the push rod 14 of the unclamping unit 13, a detecting means 16 for detecting the rear end of the draw bar 11 via a cylinder member 15 is built in.
A determination means 17 is provided for determining a gripping state such as an empty grip of the tool 8 by the clamp mechanism 9 based on the detection signal 6. The determination means 17 is provided, for example, in a spinning device or a control device (not shown) that controls the entire machine equipped with the spinning device.

The arrangement of the bearings 2 and 3 and the spindle drive source 5 is such that, in this example, the front part (tool mounting side part) and the rear part of the main shaft 4 are supported by a radial type bearing 2, and the middle part thereof is a thrust type bearing 3. And a spindle drive source 5 is disposed at the rear end. The bearings 2 and 3 may be non-contact type bearings such as magnetic bearings or contact type bearings such as rolling bearings. In this example, as shown in FIG. 2, a hydrostatic / magnetic composite bearing is used. .

The radial type bearing 2 composed of the hydrostatic magnetic composite bearing is a composite of the hydrostatic gas bearing 2A and the magnetic bearing 2B. The term "combination" as used in this specification means that both types of bearings of a static pressure type and a magnetic type are combined so as to generate a common part. For example, a common part (a radial bearing) In this case, an axially overlapping portion may be generated, or at least a part of parts may be shared by both types of bearings.

In this embodiment, as shown in FIG. 3 and FIG. 4, the throttle 23a of the static pressure gas bearing 2A is provided on the core 23 of the electromagnet of the magnetic bearing 2B, so that the static pressure gas It constitutes a part of the bearing surface. The core 23 has a pair of main cores 23a, 23a separated in the axial direction, and a connecting core 23b connecting the main cores 23a, 23a. The magnetic bearing 2 </ b> B
The coil 25 is wound around b. The coil 25 is embedded in a non-magnetic material 26 such as a resin material. The static pressure gas bearing 2A is formed on the inner diameter side surface of the core 23 and the non-magnetic body 26, and forms a bearing gap d1 between the main shaft 4 and a static pressure magnetic receiving surface 2Aa. 23a
And a diaphragm 24a which is provided on the hydrostatic bearing surface 2Aa. The throttles 24a are provided at the ends of the air supply holes 24 opened on the outer diameter side surfaces of the main core portions 23a. The cores 23 are arranged at a plurality of locations in the circumferential direction around the main shaft 4 (four locations in the example of FIG. 1) and fixed to the housing 1. The gap between the circumferentially adjacent cores 23 is filled with a non-magnetic material 27 such as a resin material. This non-magnetic material 27 is
It may be integrated with the non-magnetic body 26 around the coil 25 (FIG. 3). These nonmagnetic materials 26 and 27 and core 2
3 form the static pressure magnetic bearing surface 2Aa.

FIG. 5 is an enlarged view of a bearing 3 formed of a thrust type hydrostatic magnetic composite bearing. This pair of bearings 3, 3
Are installed in the housing 1 so as to oppose both sides of the flange portion 4a provided on the main shaft 4, and constitute one double-sided thrust-type hydrostatic composite bearing 30 with each other. The hydrostatic magnetic bearings 3 on both sides have the same configuration. These hydrostatic magnetic composite bearings 3 are each composed of a hydrostatic gas bearing 3
A and the magnetic bearing 3B are combined. In this embodiment, the throttle 33a of the hydrostatic gas bearing 3A is provided in the core 33 of the electromagnet of the magnetic bearing 3B so that the bearing components are shared and a part of the bearing surface is overlapped in the axial direction. . The core 33 has a C-shaped longitudinal section so that the opening 33d is formed on the surface facing the main shaft flange 4a, and the coil 35 is housed therein. The thrust type hydrostatic gas bearing 3A is formed on the side surface of the core 33 and forms a bearing gap d2 with the main shaft flange 4a, and the hydrostatic bearing surface 3Aa provided on the core 33. And a stop 34a which is open to the outside. The throttle 34 a is provided at the tip of an air supply hole 34 opened on the outer diameter side surface of the core 33.

In the static pressure gas bearings 2A, 3A in the static pressure magnetic composite bearings 2, 3 shown in FIG. 2, the air supply holes 24, 34 are compressed from the air supply inlet 40a of the air supply hole 40 provided in the housing 1. Air or other compressed gas is supplied.

FIG. 8 shows the operating states of the clamp mechanism 9 at the tip of the main shaft 4. FIG. 3A shows an unclamped state,
(B) shows a clamp state, and (C) shows a tool empty gripping state (no tool state). A tapered tool fitting recess 41 for fitting the tapered shank portion 8a of the tool 8 is provided at the tip of the main shaft 4. The shank portion 8a is formed hollow, and has an inner flange 8b at the rear end. In the spindle 4,
Subsequent to the tool fitting recess 41, a clamp mechanism housing recess 42 is provided.

The clamp mechanism 9 has a gripper 43 inserted into the shank portion 8a and engaged with the inner flange 8b, and a gripper spreading member 44 disposed in the gripper 43. The gripper 43 is a cylindrical member that is divided into a plurality of pieces in the circumferential direction.
It has an engagement projection 43a that can be engaged with. Gripper 4
Reference numeral 3 denotes a tapered surface 43 which engages with a tapered expansion / contraction guide surface 4b provided in the clamp mechanism receiving recess 42 of the main shaft 4.
b, and the diameter is reduced by being pressed against the expansion / contraction guide surface 4b by the diameter-reducing urging spring 45 in the clamp mechanism housing recess 42. The gripper expanding member 44 is a member that expands the gripper 43 by being drawn into the gripper 43, and has an outer peripheral surface formed as a tapered diameter expanding guide surface. Due to the spread, the engagement protrusion 43a of the gripper 43 is engaged with the inner flange 8b of the tool 8. The gripper spreading member 44 is provided at the tip of the draw bar 11, and the draw bar 11 is urged backward by the spring member 12 in the main shaft 4. The spring member 12 holds the gripper 4
The diameter expansion force of No. 3 is designed to be larger than the diameter reduction force of the diameter reduction urging spring 45. Accordingly, in a natural state in which no external force is applied to the drawbar 11, the shank portion 8a of the tool 8 is in a clamped state in which the shank portion 8a of the gripper 43 is pulled toward the back side of the tool fitting concave portion 41 by the engagement protrusion 43a.

According to the clamp mechanism 9, the clamp operation is performed as follows. In the unclamped state in which the drawbar 11 is pushed forward as shown in FIG. 8A, the shank portion 8a of the tool 8 is pushed into the tool fitting recess 41 of the main shaft 4 to cancel the pushing of the drawbar 11. Due to the elimination of the pressing, the expanded front portion of the gripper expanding member 44 enters the gripper 43 together with the draw bar 11 by the urging force of the spring member 12, and the gripper 43 expands its diameter to bring the tool 8 into a clamped state (FIG. 8 ( B)). When the drawbar 11 is pushed forward from this state, an unclamped state shown in FIG. In the state where the tool 8 is gripped in an empty state, the gripper spreading member 44 moves backward from the regular tool clamp position because the gripper 43 does not hit the tool 8 (FIG. 8C). Assuming that the difference between the positions is L, the rear end position of the draw bar 11 is more in the empty grip state than in the grip state of the tool 8 (FIG. 9B,
(C) is also located behind by the distance L.

FIG. 7 shows the operating states of the unclamping unit 13 and the rear end of the main shaft 4. FIG. 7 (A), (B)
The upper half shows the operating state at the time of unclamping in FIG.
The lower half shows the operating state at the time of tool clamping, and the lower half shows the operating state at the time of empty gripping. A flange 11 a is provided at the rear end of the draw bar 11 in the main shaft 4.
The rear end of the spring member 12 is engaged with a. At the rear end of the hollow hole through which the draw bar 11 of the main shaft 4 is inserted, a cylinder member 15 for abutting the push rod 14 of the unclamping unit 13
However, it is fitted adjacent to the flange 11a so as to be able to move forward and backward. The cylinder member 15 is prevented from falling back to the rear of the main shaft by a ring-shaped locked member 19 attached to the rear end of the main shaft 4, and is pressed together with the draw bar 11 by the urging by the spring member 12 and the pressing by the push rod 14. Retreat. Locked member 1
9 has a projection 19a on the outer periphery.

The unclamping unit 13 includes a push rod 14
The push rod 14 is constituted by the tip of a piston rod 54 of the hydraulic cylinder 51. The piston rod 54 penetrates through the cylinder body 52 of the fluid pressure cylinder 51 before and after. The cylinder main body 52 is provided with fluid ports 58 and 59 that communicate with the cylinder chambers before and after the piston 53, respectively. The fluid pressure cylinder 51 has a cylindrical guide member 55 installed in the housing 1, and a cylinder body 52 is installed to be able to advance and retreat, and stoppers 56, 57 provided before and after are engaged with the guide member 55. The longitudinal movement range of the cylinder body 52 is restricted. The cylinder body 52 is urged forward by a return spring 60 with respect to the guide member 55.

The spindle rear end engaging mechanism 20 will be described. At the front of the cylinder body 52, the engaged member 19 at the rear end of the spindle 4 is provided.
A hooking member 61 that engages with the shaft is mounted to be freely openable and closable about a support shaft 62, and is urged in a closing direction by a closing urging spring 63 such as a torsion coil spring. Behind the hooking member 61, an opening operation member 64 having an inwardly tapered guide surface 64a is provided on the outer periphery of the cylinder body 52 so as to be able to advance and retreat, and by opening the opening operation member 64, the guide surface 64a The hooking member 61 is closed.
The opening operation member 64 can be pressed forward on the step surface 52 a of the cylinder body 52, and is lightly pressed against the hook member 61 by a pressing spring 65.

When the tool is clamped by the clamping mechanism 9 (FIG. 1) at the tip of the spindle 4, the unclamping unit 13 is actuated by the return spring 60 as shown in the lower half of FIG. The main body 52 has advanced to a forward end where it hits a rear stopper 57. When performing unclamping, a working fluid is supplied to the cylinder chamber behind the pitson 53. As a result, the push rod 14 at the tip of the piston rod 52 pushes the cylinder member 18 behind the draw bar 11 to cause the clamp mechanism 9 to perform the clamping operation of the tool 8. At this time, the entire hydraulic cylinder 51, that is, the cylinder body 52, retreats against the return spring 60 due to the resistance acting on the push rod 14, and the hook member 61 also retreats together with the cylinder body 52. By this retreat, the hook member 61 is engaged with the engaged member 19 at the rear end of the main shaft 4, and the main shaft 4 is prevented from moving forward by the pushing operation of the pushing member 14.

When the working fluid is supplied from the unclamped state to the cylinder chamber in front of the fluid pressure cylinder 51, the pushing member 14 retreats, and the cylinder body 52 moves forward to open the operating member 64 on the step surface 52a. Push. Therefore, the hooking member 61 is opened by the opening operation member 64, and the engagement between the hooking member 61 and the engaged member 19 is released.

As shown in FIG. 10, the push rod 14 is formed to be hollow, and the piston rod 52 is formed by the male screw portion 14a at the base end.
Mounted on the tip of Detecting means 16 for detecting the cylinder member 15 behind the drawbar 11 is built in the hollow internal space of the push rod 14, and is fixed with a set screw 69. The detecting means 16 may be any as long as it can detect the difference L between the rear end positions of the draw bar 11 when the tool is gripped by the clamp mechanism 9 and when the tool is idle, and a magnetic or optical displacement detecting means can be used. In Although,
In this example, a proximity switch that magnetically detects displacement is used. The lead wire 68 of the detecting means 16 is drawn out from the center hole of the piston rod 52 having a hollow shaft.

An operation for detecting an empty grip by the above configuration will be described. The operations of the clamp mechanism 8 and the unclamping unit 13 are as described above. As shown in FIG. 9A, when the clamp mechanism 8 is unclamped, the push rod 14 of the unclamping unit 13 moves forward and pushes the cylinder member 15 behind the drawbar 11. At the time of clamping, the drawbar 11 is pushed rearward by the spring member 12, and the cylinder member 15 is retracted to a predetermined position as shown in FIG. 9B. In this state, the distance between the push rod 14 and the cylinder member 15 is long, and the detection means 16 built in the push rod 14 does not detect the cylinder member 15. At the time of empty gripping, the tool 8 does not hit the gripper 43 by the clamp mechanism 9 (FIG. 8).
The drawbar 11 is moved further backward by a certain distance L than at the time of clamping. Therefore, the cylinder member 15 is detected by the detection means 16 built in the push rod 14. Based on this detection signal, it is determined by the determination means 17 that it is an empty grip. In the unclamped state shown in FIG. 9A, the push rod 14 comes into contact with the cylinder member 15 and the detection means 16 built in the push rod 14 is turned on. Since the device can be distinguished by a control signal for controlling the device, it can be distinguished between an empty grip and an unclamped state.

According to this spindle device, since the detecting means 16 for empty gripping is incorporated at the tip of the push rod 14 for pushing the draw bar 11, the unclamping unit 13 is hooked to the engaged member 19 on the outer periphery of the rear end of the main shaft. The position of the drawbar 11 can be detected without causing a problem in securing the arrangement space while using the structure in which the member 61 is engaged. Further, since the detecting means 16 is built in the tip of the push rod 14, there is no need to provide a sensor target in a member such as the draw bar 11 which rotates together with the main shaft 4. Therefore, even when the main shaft 4 rotates at high speed, no vibration occurs.
Stable rotation is obtained.

Further, in this spindle device, since the hydrostatic compound bearings are used as the bearings 2 and 3 for supporting the main shaft 4, the dynamic dynamic rigidity and rotational accuracy of the hydrostatic gas bearing and the magnetic bearing are excellent. A compact bearing that takes advantage of the dual-bearing characteristics of static rigidity. Hydrostatic magnetic composite bearings
Since it is a non-contact bearing, it is susceptible to the bias of the spindle weight. However, since the detection means 16 for discriminating the idle grip is built in the tip of the unclamping push rod 14, a sensor target is provided on the spindle 4 with a bias. It is not necessary, and it is possible to judge the empty gripping without adversely affecting the operation while using the non-contact bearing. Since the proximity switch is used as the detection means 16, a small, lightweight and inexpensive one can be used, and the detection means 16 has excellent accuracy.
It is preferable as a detection means incorporated in the device. As described above, in a spindle device having a high-precision and compact configuration using a hydrostatic composite bearing as the bearings 2 and 3 for supporting the main shaft 4, the problem of vibration due to the eccentric load of the main shaft 4 does not occur, and It is possible to detect an empty grip.

FIGS. 11 and 12 show a second embodiment of the present invention. In this embodiment, in the first embodiment, the detection means 16A is configured to protrude from the distal end surface of the push rod 14 so as to be freely protruded and retracted, so that it is possible to distinguish between the normal clamp state and the half-grasped state. Things. The detecting means 16A is disposed in the hollow push rod 14, and is urged toward the distal end of the push rod by a projection urging spring 71 built in the push rod 14. The most protruding position of the detecting means 16A is regulated by the stopper means 72. The detection means 16A is held in the support cylinder 73,
Is fitted to the inner diameter portion of the tip of the push rod 14 so as to be able to advance and retreat, so that the detecting means 16A can freely project and retract with respect to the push rod 14. The stopper means 72 includes an enlarged diameter portion 72 a provided at the rear end of the support cylinder 73 and a step surface 72 b provided in the push rod 14. The push rod 14 is fixed to the piston rod 54 of the fluid pressure cylinder 51 in the unclamping unit 13 by screwing a screw cylinder 74 that is screwed into a female screw portion on the inner diameter surface of the two 14, 14.

The detecting means 16A uses a magnetic distance detecting means and detects the distance to the rear end of the drawbar 11. Specifically, the distance from the rear end of the drawbar to the rear end surface of the cylinder member 15 is detected. As the magnetic distance detecting means, for example, an overcurrent type or reluctance type displacement sensor is used. The determining unit 17A that determines the grip state of the tool based on the detection signal of the detecting unit 16A is based on the distance detection value of the detecting unit 16A and the like.
As the determination of the gripping state, a determination is made of an unclamped state, a normal clamped state, a half gripped state, and an empty gripped state. Other configurations in this embodiment include:
This is the same as the first embodiment described with reference to FIGS.

The determination of the tool gripping state in this embodiment will be described. In the unclamping state in FIG. 12A, the push rod 14 of the unclamping unit 13 moves forward and pushes the cylinder member 15 behind the drawbar 11. At this time, the detecting means 16 </ b> A comes into contact with the cylinder member 15 and is immersed and housed in the push rod 14. In the normal clamping state shown in FIG. 3B, the push rod 14 of the unclamping unit 13 is retracted, and the detecting means 1
6A and the cylinder member 15 are separated from each other. At this time, the detection means 16A is actuated by the projection urging spring 71 in the push rod 14.
The push rod 14 is pushed forward (left side in the figure) from the distal end face. Although the pushing amount is regulated by the stopper means 72, the pushing amount is set so that the distance to the rear end of the cylinder member 15 can be detected by the detecting means 16A. In the half-grasping state shown in FIG. 4C, the rear end position of the cylinder member 15 is slightly forward of the normal clamping state. If the distance La at this time is equal to or greater than the specified value, the determination means 17A (FIG. 11) determines that the user is half-grasping. In the empty gripping state shown in FIG.
Is located rearward (rightward in the figure) of the normal clamp state. FIG. 5 shows an example in which the rear end surface of the cylinder member 15 and the detection means 16A come into contact with each other. In this case, the discriminating means 17A uses an on / off signal of the operation of the unclamping unit in order to distinguish it from the unclamped state in FIG. In a magnetic bearing spindle or a hydrostatic composite bearing spindle, the state in which the push rod 14 of the unclamping unit is pushing the cylinder member 15 can be detected by measuring the current value of the axial magnetic bearing. The measured value of the current value makes it possible to distinguish between the unclamped state and the idle gripping state.

According to this embodiment, the detecting means 16A is projected from the tip end surface of the push rod 14 so as to be able to protrude and retract, and is urged to protrude. In addition, it is possible to determine the normal clamping state and the half-grasping state. The half-grasping state is an incompletely clamped state in which the tool 8 (FIG. 1) and the tapered tool fitting surface formed on the distal end surface of the main shaft 4 are insufficiently fitted and are clamped. This half-grasping state occurs when foreign matter adheres to the fitting surface. In the case of the first embodiment, it is possible to determine the unclamped state, the normal clamped state, and the empty gripping state, but it is difficult to determine the half gripped state. In order to determine the normal clamping state and the half-grasping state, the distance between the rear end surface of the cylinder member 15 and the front end surface of the push rod 14 (the detection surface of the detection means 16) must be accurately detected. On the other hand, magnetic displacement sensors that can be built into the push rod 14 are limited to small ones,
The distance may be outside the detectable range. For this reason, it is structurally difficult for the magnetic proximity sensor fixed to the tip of the push rod 14 to detect the end face of the cylinder member 15 in the half-grasped state. However, in the case of the second embodiment, since the detecting means 16A protrudes from the push rod 14 and is urged toward the push rod 14, the detecting means 16A is pushed in the normal clamping state and the half-grasping state. Since it is located at a position near the rod 14, even if the detectable distance of the detecting means 16A composed of a magnetic displacement sensor is short, the distance can be detected.

[0034]

The spindle device with an automatic tool changing function according to the present invention has a built-in detecting means for detecting the rear end of the draw bar at the tip of the push rod of the unclamping unit. Because the gripping state is determined, regardless of the type of unclamping unit,
An idle grip can be determined by detecting the drawbar position, and the problem of imbalance during high-speed rotation does not occur. When the detecting means is arranged to protrude from the distal end face of the push rod and to be protruded toward the distal end side of the push rod, it is possible to discriminate between the normal clamp state and the half-clamp state. When the unclamping unit has a main shaft rear end engaging mechanism that engages with the outer periphery of the main shaft rear end during unclamping to prevent the main shaft from moving toward the front end, a compact clamping mechanism can be obtained. However, it is difficult to obtain a detection means arrangement space near the rear end of the drawbar. However, since the detection means is built in at the tip of the push rod, empty gripping detection can be performed without any problem of the detection means arrangement space. When the above-mentioned bearing is a hydrostatic magnetic composite bearing, it is possible to discriminate the empty gripping without affecting the above-mentioned performances while obtaining excellent dynamic rigidity, rotational accuracy and static rigidity. If the detection means is a proximity switch,
Lightweight, inexpensive, excellent in accuracy, and can be easily incorporated into a small push rod.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a conceptual configuration of a spindle device with an automatic tool changing function according to a first embodiment of the present invention.

FIG. 2 is a sectional view of the spindle device.

FIG. 3 is an enlarged sectional view of a radial type hydrostatic composite bearing of the spindle device.

FIG. 4 is a cross-sectional view of the hydrostatic magnetic composite bearing.

FIG. 5 is an enlarged sectional view of a thrust type hydrostatic composite bearing of the spindle device.

FIG. 6A is a diagram showing a spindle of the spindle device.
FIG. 3B is a cross-sectional view showing the relationship between the clamp mechanism and the unclamping unit, and FIG.

FIG. 7 is an enlarged sectional view showing each operation state of the unclamping unit.

FIG. 8 is an enlarged sectional view showing each operation state of the clamp mechanism.

FIG. 9 is an operation explanatory diagram showing the relationship between the rear end of the drawbar and the push rod in each operation state.

10A is a cross-sectional view of the push rod, FIG. 10B is a front view of the push rod, and FIG. 10C is a side view of the push rod.

FIG. 11 is a sectional view of a push rod according to a second embodiment of the present invention.

FIG. 12 shows a drawbar rear end and a push rod according to the embodiment;
FIG. 7 is an operation explanatory diagram showing a relationship between detection means.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Housing 2, 3 ... Bearing 4 ... Spindle 5 ... Spindle drive source 8 ... Tool 9 ... Clamp mechanism 10 ... Automatic tool changer 11 ... Drawbar 12 ... Spring member 13 ... Unclamp unit 14 ... Push rod 15 ... Cylinder member 16 , 16A: detecting means 17, 17A: determining means 20: main shaft rear end engaging mechanism

Claims (6)

[Claims] 1. A main shaft is supported by a housing via a bearing, and a clamp mechanism is provided at a tip of the main shaft. The clamp mechanism is configured to retreat a drawbar penetrating through the inside of the main shaft by pushing a tool into the front end of the main shaft. An unclamping unit that clamps the tool by a force and presses the rear end of the draw bar with a push rod to set the clamp mechanism in an unclamping state is provided in the housing. In the spindle device with an automatic tool change function in which the rear end position of the drawbar is also rearward in the empty gripping state, a detection means for detecting the rear end of the drawbar is built in at the front end of the push rod of the unclamping unit. A spindle with an automatic tool changing function, wherein a gripping state of the tool is determined based on a detection signal of a detecting means. Location. 2. The automatic tool according to claim 1, wherein the detection means protrudes from the distal end surface of the push rod so as to be able to protrude and retract, and is arranged so as to be urged toward the distal end side of the push rod. Spindle device with exchange function. 3. The spindle with an automatic tool change function according to claim 1, wherein the detection means detects the replacement of the drawbar via a cylinder member arranged in contact with a rear end surface of the drawbar. apparatus. 4. The main shaft rear end engaging mechanism for engaging the main shaft rear end outer periphery at the time of unclamping to prevent the main shaft from moving toward the front end side. Item 4. A spindle device with an automatic tool change function according to any one of Items 3. 5. The bearing according to claim 1, wherein the bearing is a radial-type hydrostatic composite bearing in which a hydrostatic gas bearing and a magnetic bearing are combined. Spindle device. 6. The spindle device with an automatic tool change function according to claim 1, wherein said detecting means is a proximity switch for magnetically detecting displacement.