JP3779527B2 - Tool clamp spring monitoring device mounted on the machine tool spindle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an automatic monitoring device for a tool clamp spring in a spindle that detachably holds a tool in a machine tool such as a machining center.
[0002]
[Prior art]
A machining center equipped with an automatic tool changer includes a tool clamp mechanism that draws and holds a tool in a spindle.
The tool clamping mechanism includes a draw bar having a collet chuck that holds a pull stud attached to a tail portion of a tool shank, and a clamp spring biased in a direction in which the draw bar is always pulled.
When changing the tool, the actuator pushes out the draw bar against the clamp spring, opens the collet chuck and releases the tool.
[0003]
The clamp spring is a stack of many coil springs and disc springs in the axial direction, and generates a tensile force of, for example, 800 kg to clamp the tool.
In the machining center, tool change is performed many times, and the clamp spring repeats compression and extension each time. If the spring coefficient of the clamp spring is deteriorated by use, the spindle cannot hold the tool with a sufficient clamping force, which adversely affects the machining performance.
[0004]
Therefore, conventionally, the machining center is periodically stopped, and a measuring machine for measuring tensile stress is attached to the main shaft to measure the spring force of the clamp spring. When the spring force is reduced by a predetermined value from the initial value, the clamp spring is replaced.
[0005]
[Problems to be solved by the invention]
The conventional clamp spring monitoring means described above requires periodic maintenance and inspection work, and cannot cope with a sudden decrease in the spring force of the clamp spring, resulting in poor processing. There was a problem that caused a failure of the spindle.
Therefore, the present invention provides a tool clamp in a machining center having a structure in which a draw bar is mechanically pushed to an unclamping position by using a moving force of the head stock when a head stock equipped with a spindle is moved to a tool change position by a servo mechanism. An automatic spring monitoring device is provided.
[0006]
[Means for Solving the Problems]
A machining center to which the present invention is applied includes a bed, a column disposed on the bed, a headstock supported slidably with respect to the column, and a headstock attached to the column via a ball screw. Servo motor to be controlled, main shaft rotatably supported in the head stock, clamp spring mounted in the main shaft to clamp the tool, cam block having a cam groove attached to the tool change position of the column, and head A mechanical arm with a cam follower that is mounted on the stock and engages the cam groove, and when the headstock is moved to the tool change position by the servo motor, the clamp spring is moved by the pivoting motion of the mechanical arm that engages the cam block. Means are provided for releasing the clamp of the tool when pressed. And means for detecting the current value flowing in the servo motor that drives the headstock, the change value of the current value when the tool is unclamped by the tool change when the spring force of the clamp spring is the initial value, and the spring force is the initial value Means for comparing the value of the change in the current value when the tool is unclamped due to the tool change when the tool is further reduced is provided to monitor the spring force of the tool clamp spring.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a side view of a machining center provided with an automatic monitoring device for a clamp spring according to the present invention, and FIG.
The machining center denoted as a whole by reference numeral 1 has a bed 10 and a table 20 that moves on the bed 10 in the axis Z direction. On the bed 10, a pair of guide rails 31 and 32 are laid in a posture inclined with respect to the horizontal, and a column 30 having a linear motion guide device that engages with the guide rails 31 and 32 is orthogonal to the paper surface. Is supported so as to be movable in the direction of the axis X.
[0008]
A servo motor 36 is attached on the bed 10, and the movement of the column 30 is controlled by a ball screw 34 driven by the servo motor.
A head stock, indicated as a whole by 100, is supported relative to the column 30 so as to be slidable in the axis Y direction.
A servo motor 50 is attached to the top of the column 30 and controls the head stock 100 along the axis Y via a ball screw 52. A cam block 60 having a cam groove 62 is fixed to the top of the column 30. On the other hand, the mechanical arm 70 is attached to the headstock 100, and the cam follower 72 of the mechanical arm 70 engages with the cam groove 62 of the cam block 60.
[0009]
FIG. 1 shows a state in which the head stock 100 is pulled up to an ATC (automatic tool change) position by a servo motor 50. At this ATC position, the cam follower 72 of the mechanical arm 70 attached to the headstock 100 engages with the cam groove 62 of the cam block 60 fixed to the column 30. The cam groove has a curved profile, and the mechanical arm 70 is turned in the direction of the arrow R1 about the pin 74 by this profile.
The spindle tool clamp mechanism installed in the headstock 100 is unclamped with the turning of the mechanical arm as a power source.
[0010]
2 is a cross-sectional view showing the main part of the headstock 100, and FIG. 3 is a view taken along the line DD in FIG.
The head stock 100 supports a main shaft 110 in a housing 105 rotatably by bearing groups 114 and 116. The main shaft 110 has a tool mounting hole 112 and holds the tool 200.
[0011]
The main shaft 110 has a motor rotor 122 attached to the outer periphery thereof, and is directly driven by electric power supplied to the stator 120.
A draw bar 130 is slidably inserted into the main shaft 110. A collet chuck 132 is provided at the front end of the draw bar 130 and detachably holds the pull stud 210 of the tool 200.
[0012]
A push rod 140 having a small diameter portion is connected to the rear end portion of the draw bar 130. The small diameter portion of the push rod 140 passes through a spring receiving member 170 fixed in the main shaft 110. A large number of disc springs 160 are inserted between the small diameter portion of the push rod 140 and the main shaft 110. The disc spring 160 exerts a spring force in a direction in which the push rod 140 and the draw bar 130 connected to the push rod 140 are always drawn into the main shaft 110, and functions as a clamp spring for the tool.
The rear portion 142 of the push rod 140 passes through the sleeve 150, and the sleeve 150 engages with the mechanical arm 70.
[0013]
As shown also in FIG. 3, the mechanical arm 70 is pivotally supported by a pin 74 relative to the headstock housing 105. The cam follower 72 provided at the upper end of the mechanical arm 70 engages with the cam groove 62 of the cam block 60 fixed to the column side at the ATC position. When the head stock 100 is raised along the axis Y to the ATC position, the cam follower 72 of the mechanical arm 70 is inserted into the cam groove 62 of the cam block 60. The cam groove 62 has a curved cam profile as shown in the figure, and the mechanical arm 70 is pivoted in the direction of the arrow R1 with the pin 74 as a fulcrum.
[0014]
As shown in FIG. 3, a Y-shaped fork portion 80 is provided, and a roller 82 attached to the inside of the fork portion 80 engages with a stepped portion formed on both sides of the sleeve 150.
[0015]
When the mechanical arm 70 pivots in the direction of the arrow R1, the roller 82 pushes the sleeve 150 toward the tip of the main shaft 110, and the push rod 140 engaged with the sleeve 150 by the shoulder 152 of the sleeve 150 causes the draw bar 130 to clamp the spring. It pushes out toward the tool mounting hole 112 against the spring force of 160.
By this operation, the collet chuck 132 at the tip of the draw bar 130 pushes the pull stud 210 of the tool 200 to push out the tool 200 from the tool mounting hole of the main shaft 110 and releases the grip of the pull stud 210.
[0016]
At the ATC position, a new tool is inserted into the tool mounting hole 112 of the spindle 110 by an automatic tool changer (not shown).
Thereafter, an instruction to complete the tool change is given to the servo motor 50, and the servo motor 50 lowers the head stock 100 along the axis Y and moves it to a predetermined lowered position.
When the head stock 100 is lowered, the cam follower 72 of the mechanical arm 70 is detached from the cam groove 62 of each block 60. A spring 90 stretched between the mechanical arm 70 and the head stock housing 105 returns the mechanical arm 70 to the initial state.
[0017]
The clamp spring 160 pulls the draw bar 130 and the push rod 140 inside the main shaft 110, and the collet chuck 132 of the draw bar 130 grips and pulls the pull stud 210 of the tool 200, and the clamping of the tool 200 with respect to the main shaft 110 is completed.
[0018]
FIG. 4 is a graph showing the current A flowing through the servomotor 50 and the moving speed V when the headstock 100 is moved in the fast-forward mode.
The headstock 100 starts to rise from the first origin Y1 on the axis Y to the ATC position, the cam follower 72 of the mechanical arm 70 engages with the cam groove 62 of the cam block 60, reaches the ATC position Y2, and stops. During this rise, the mechanical arm 70 pushes the draw bar 130 against the spring force of the clamp spring 160, so that the servo motor 50 is supplied with the current value A1 necessary for unclamping. When the ATC is completed, the servo motor 50 lowers the head stock 100 from the ATC device Y3 and returns it to the first origin Y4.
[0019]
Since the tool clamping and unclamping mechanism of the present invention operates using the movement of the head stock in the axis Y direction as a power source as described above, the current of the tool is detected by detecting the current flowing in the servo motor that operates the head stock. The spring force of the clamp spring can be monitored.
[0020]
That is, FIG. 5 is a graph showing changes in the current A flowing to the servo motor and the movement speed V when the head stock in which the spring force of the clamp spring 160 is reduced by 60% from the initial value is moved in the same mode as in FIG. It is.
Since the spring force of the clamp spring is reduced, the current value A2 required for unclamping flowing through the servo motor is clearly reduced compared to the current value A1 of the normal clamp spring.
[0021]
Therefore, the current flowing through the servo motor that drives the headstock is detected, and the current value at the time of starting ATC is compared with the preset current value to monitor the reduction of the spring force of the clamp spring for tool clamping. can do.
[0022]
【The invention's effect】
According to the present invention, every time the machining center performs ATC, it is possible to detect the degree of the spring force of the tool clamp spring mounted on the headstock. Therefore, it is possible to avoid the occurrence of a failure due to sudden deterioration of the clamping force and to know in advance the time for replacing the clamp spring, which is extremely advantageous in terms of machine maintenance and machining planning.
[Brief description of the drawings]
FIG. 1 is a side view of a machining center embodying the present invention.
FIG. 2 is a cross-sectional view of a main part of the headstock.
FIG. 3 is a view taken along the line DD in FIG. 2;
FIG. 4 is an explanatory diagram showing the operation of the present invention.
FIG. 5 is an explanatory diagram showing the operation of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Machining center 10 Bed 20 Table 30 Column 32, 34 Guide rail 50 Servo motor 52 Ball screw 60 Cam block 62 Cam groove 70 Mechanical arm 72 Cam follower 74 Pin 100 Headstock 105 Housing 110 Spindle 130 Draw bar 132 Collet chuck 140 Push rod 150 Sleeve 160 Clamp Spring

Claims (1)

A bed, a column disposed on the bed, a headstock supported slidably with respect to the column, a servomotor attached to the column and controlling movement of the headstock via a ball screw, and the headstock A main shaft that is rotatably supported inside, a clamp spring that is mounted in the main shaft and clamps the tool, a cam block that has a cam groove that is attached to the tool change position of the column, and a head stock that is mounted on the cam groove. Equipped with a mechanical arm that has a cam follower to be engaged, and when the headstock is moved to the tool change position by the servo motor, the clamp spring is pressed by the pivoting movement of the mechanical arm that engages the cam block to release the tool clamp. A machine tool that
Means for detecting the current value flowing in the servo motor that drives the headstock, the value of the change in the current value when the tool is unclamped by the tool change when the spring force of the clamp spring is the initial value, and the spring force is reduced from the initial value A tool clamp spring monitoring device comprising means for comparing a change value of a current value when a tool is unclamped due to tool change when the tool is replaced , and monitoring a spring force of the tool clamp spring.

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