JPH0416306B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tool holding force measuring device for measuring the holding force of a tool in a machine tool such as a machining center.

Normally, in machine tools such as machining centers, when holding a tool on the spindle, the taper shank, which is the connecting part of the tool, is used to hold the tool on the spindle using the elastic force of a large number of disc springs contracted around the drawbar. A structure that presses and holds onto a surface is used. Therefore, the elastic force of the disc spring, that is, the holding force of the tool, is extremely important in transmitting power from the spindle to the tool, and generally, if the holding force decreases, machining accuracy, cutting ability, etc. will decrease.

In most cases, this decrease in holding force is caused by damage to the disc spring, but since the disc spring is stored inside the main shaft and cannot be seen from the outside under normal conditions, the disc spring cannot be seen from the outside. Even if the spring is damaged and the holding force is reduced, the operator continues to work without noticing this, which often results in a decline in machining quality. It has been desired to develop a tool holding force measurement device that can recognize abnormalities in the tool.

Furthermore, Japanese Utility Model Application Publication No. 58-143144 proposes a method in which a load transducer such as a strain meter element or a piezoelectric retractor is installed inside the tool shank to electrically convert and measure the tool holding force. However, since the outputs of the transducers are all electrical, this method requires a measuring device to convert those electrical outputs into loads, and such a measuring device must be connected inside or outside the tool shank. There is a need to.

If it is connected externally, a lead wire is required to connect the tool shank and the measuring device, making the measurement setup complicated. It is difficult to perform this efficiently while performing an automatic tool change operation on the spindle.

Also, if a measuring device is built inside,
Although it is possible to measure holding force using automatic tool changing operations, it is difficult to maintain reliability by installing such precision electronic equipment inside the tool shank, where there is a high possibility of mechanical impact. Including problems with. In addition, since it is necessary to have a power source such as a battery inside the tool shank to drive the electronic device, the structure becomes complicated, and work such as battery replacement occurs periodically, resulting in the inconvenience of complicated maintenance. .

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a tool holding force measuring device that can easily measure the holding force of a tool and recognize abnormalities in disc springs and the like.

Another object of the present invention is to provide a tool holding force measuring device that is capable of measuring tool holding force using an automatic tool exchange operation, is resistant to mechanical shock, and does not require a power source for driving. It is something.

That is, the present invention has a main body in which a taper shank to be attached to the main shaft of a machine tool and a tool gripping groove for automatic tool changing are formed, and a rod is inserted into the main body in the direction of the rod axis in a manner penetrating the main body. A pull stud is provided at the end of the rod on the tapered shank side, and a cylinder assembly is disposed on the opposite side of the main body in the axial direction from the part where the taper shank is formed with respect to the tool gripping groove. The rod is mounted to the main body in series in the axial direction of the rod, a cylinder is formed in the cylinder assembly, and a piston is fitted and engaged with the cylinder so as to be movable in the axial direction of the rod. In addition to connecting the rod, an incompressible fluid is sealed in the cylinder, and a pressure gauge capable of displaying the pressure of the incompressible fluid in the cylinder is installed from the outer periphery to the outer periphery of the cylinder assembly. A pressure transmission passage is provided inside the cylinder assembly so as to protrude in a direction perpendicular to the axial direction of the rod, and is capable of transmitting the pressure of the incompressible fluid in the cylinder to the pressure gauge. The cylinder is formed in such a way that the meter and the cylinder are connected.

Embodiments of the present invention will be described below based on the drawings.

Figure 1 is a sectional view showing an example of the main shaft part of a machining center, which is the object of measuring the holding force;
The figure is a sectional view showing an embodiment of the tool holding force measuring device according to the present invention.

The machining center 1, as shown in FIG.
It has a cylindrical main shaft 5 that is rotatably supported by the frame 2 via a plurality of bearings 3, and the left end of the main shaft 5 in the figure has a tapered tool holding surface 5a.
is formed. A drawbar 6 is fitted into and engaged with the main shaft 5 so as to be movable in the directions of arrows A and B, that is, parallel to the main shaft axis CL. A large number of disc springs 9 are compressed through blocks 7 fitted in such a manner that they abut against each other, and constantly bias the bar 6 in the direction of arrow B. A collet 10 is located at the left end of the bar 6 in the figure, and a plurality of holding claws 10a are connected to the main shaft center CL.
On the right side of the drawbar 6 in the figure, a piston 11 with a rod portion 11a is opened and closed in the directions of arrows A and B by hydraulic pressure. It is provided so that it can be moved freely.

On the other hand, tool holding force measuring device 12 according to the present invention
As shown in FIG.
The main body 13 has an annular tool gripping groove 13b for automatic tool exchange. Also,
A cylinder assembly 18 is arranged in series with the main body 13 in the axial direction of the rod 19, which will be described later, on the opposite side of the main body 13 in the axial direction of the rod 19, which will be described later, from the part where the taper shank 13a is formed with respect to the tool gripping groove 13b. It is set up in the form of That is, the main body 18
A ring 15 constituting a cylinder assembly 18 is fitted into the ring 15 . A cylinder 15a having a circular cross section is formed in the ring 15, and a piston 16 is fitted into the cylinder 15a so as to be movable in the directions of arrows A and B. Pressure oil 17, which is an incompressible fluid, is sealed in the space. A rod 19 with a pull stud 19a formed at its tip is screwed into the piston 16 so as to pass through the main body 13, and seals such as O-rings are provided between the rod 19 and the ring 15 and between the piston 16 and the ring 15. A ring 20 is provided to prevent the pressure oil 17 from leaking to the outside. A pressure gauge 21 is installed on the outer periphery of the ring 15.
is provided inside the cylinder 15a and via an oil passage 15b formed in the ring 15, and a pressure gauge 21 is provided on the outer circumference of the ring 15 of the cylinder assembly 18 in the axial direction of the rod 19. Arrows A, B
It is provided so as to protrude in a direction perpendicular to the direction. Note that the pressure gauge 21 includes a cylinder 15a.
The pressure applied to the pressure oil 17 inside the pull stud 19a
The value converted to the tensile force in the B direction is the scale 2
It is graduated as 1a. Note that 22 is a plug for sealing pressure oil inside the cylinder 15a.

Tool holding force measuring device 12 according to this embodiment, and
Since the machining center 1 has the above-described configuration, the tool 23 is attached and detached in the normal state by the first
As shown in the figure, first, the piston 11 is projected in the direction A, and the tip of the rod portion 11a and the drawbar 6
are abutted and engaged, and further the bar 6 is moved in the direction A against the elasticity of the disc spring 9. Then, collect 1
0 holding claw 10a and the taper portion 6b of the drawbar 6
A, until the collet 10, together with the bar 6, abuts the stepped portion 25b of the sleeve 25, and further movement in the A direction is prevented.
As a result, the abutting and engaging relationship between the holding claw 10a and the tip 25a of the sleeve 25 is released. Furthermore, since the drawbar 6 moves in the A direction even after the collet 10 stops contacting the stepped portion 25b, the tapered portion 6b forces the pawl 10a in the D direction against the elasticity of the collet 10. Open. In this state, when the tool 23 is inserted into the main shaft 5 until the taper shank 23b contacts the tool holding surface 5a, and the piston 11 is further retreated in the direction B, the drawbar 6 is moved to the direction B by the elasticity of the disc spring 9.
The claw 10a is moved in the direction of the tapered portion 6b.
By moving in direction B, it converges in direction C by its own elasticity. Then, the claw 10a and the pull stud 23a of the tool 23 engage with each other, but when the draw bar 6 further moves in the direction B, the engaging portion 6a of the bar 6 at the left end in the figure engages with the stepped portion 10b of the holding claw 10a. ,
The collet 10 is inserted into the sleeve 25 while being pulled in the direction B while being engaged with the pull stud 23a, and the sleeve 25 firmly maintains the engaged state of the collet 10 and the pull stud 23a. On the other hand, since the tool 23 is pulled in the B direction by the disc spring 9 via the drawbar 6 and the collet 10, the taper shank 23b of the tool 23 is pressed against the tool holding surface 5a of the spindle 5 with a predetermined pressing force. , the tool 23 is securely held on the spindle 5. In this state, the main spindle 5 is rotated together with the tool 23 to perform predetermined machining, and the rotational force of the main spindle 5 is reliably transmitted via the tool holding surface 5a and the taper shank 23b, making it possible to perform excellent machining. On the other hand, when removing the tool 23 from the main shaft 5, the piston 11 moves the bar 6 in the A direction, opens the retaining claw 10a of the collet 10 in the D direction, and then removes the bar 6 from its engagement. When the joint 6a comes into contact with the pull stud 23a and pushes the pull stud 23a in the direction A, the holding state between the taper shank 23b and the tool holding surface 5a is released, and the tool 23
is removed from the main shaft 5.

The holding force when the tool 23 is attached to the main shaft 5, that is, the force by which the collet 10 pulls the tool 23 in the direction B via the pull stud 23a, is applied by the disc spring 9. When measuring the holding force, the tool holding force measuring device 12 is attached to the tool holding surface 5a of the spindle 5 in the same manner as when attaching a tool.
The taper shank 13a of the main body 13 is inserted in the direction B in FIG. 2 while being pressed, and the collet 10 is pulled in the direction B using the elastic force of the disc spring 9 via the pull stud 19a of the rod 19. At this time, since the holding force measuring device 12 is formed with a tool gripping groove 13b like a normal tool, the main shaft 5 of the measuring device 12 is attached manually using a normal automatic tool changing operation. It can be done without any problem. In addition, a pressure gauge 21 that displays the holding force
is mounted in an offset manner to the left side in FIG. 2, that is, to the outer circumferential side of the cylinder assembly 18 with respect to the tool gripping groove 13b. At this time, there is no interference between the tool changing device on the machine tool side and the pressure gauge 21, and the mounting operation of the measuring device 12 on the main shaft 5 is performed smoothly. In addition, since the measuring device 21 is mainly composed of a cylinder assembly 12 in which pressure oil 17 is sealed and a pressure gauge 21 driven by the pressure oil 17, an electronic circuit for converting and calculating electrical signals is used for measurement. It is extremely resistant to mechanical shocks that inevitably occur during tool exchange operations without being mounted inside the device. In this way, when the pull stud 19a is pulled, the pulling force in the B direction by the disc spring 9 is applied to the piston 16 via the rod 19.
is transmitted to pressurize the pressure oil 17 inside the cylinder 15a. The pressure fluctuation of the pressure oil 17 is immediately detected by the pressure gauge 21, and the value is converted into the pulling force by the collector 10 in the B direction on the scale 21.
Since it is displayed on a, the tensile force of the disc spring 9,
That is, the holding force of the tool can be immediately determined from the value of the pressure gauge 21. If the disc spring 9 is damaged, the pressure gauge 21 will indicate a lower holding force than in a normal case, so the operator can immediately recognize the abnormality of the disc spring 9.

As explained above, the main body 13 has a taper shank 13a attached to the main shaft 5 of a machine tool and a tool gripping groove 13b for automatic tool changing, and the rod 1 is inserted into the main body in a form that penetrates the main body.
A pull stud 19a is provided at the end of the rod on the tapered shank side, and a taper shank is formed in the tool gripping groove of the main body. Cylinder assembly 1 is installed on the opposite side of the part in the axial direction.
8 is attached to the main body in series in the direction of the rod axis, a cylinder 15a is formed in the cylinder assembly, and a piston 16 is attached to the cylinder.
is fitted and engaged so as to be movable in the axial direction of the rod to connect the piston and the rod, and an incompressible fluid such as pressure oil 17 is sealed in the cylinder, and the A pressure gauge 21 capable of displaying the pressure of the incompressible fluid within the cylinder is installed in a manner that projects from the outer periphery in a direction perpendicular to the axial direction of the rod, and is mounted inside the cylinder assembly. an oil passage 15b capable of transmitting the pressure of the incompressible fluid in the pressure gauge to the pressure gauge;
Since the pressure transmission flow path is formed to connect the pressure gauge and the cylinder, the operator can hold the device 12 in a machine tool such as the machining center 1 via the pull stud 19a at any time. As a result, the holding force of the tool can be immediately known, and it is thereby possible to easily recognize abnormalities in the disc spring 9 and the like.

In addition, the mechanism for measuring holding force is formed from mechanical parts such as a cylinder assembly and a pressure gauge, and a measuring device with an electronic circuit is not attached. Even if the device is attached to the main shaft using a replacement operation, there is a low risk that the device will be damaged by the mechanical shock that accompanies the attachment. Therefore, it is possible to measure the holding force while the machine tool performs a normal tool exchange operation, and an efficient measurement operation is possible. In addition, since no electronic circuit is installed, there are no problems with power sources such as batteries, the internal structure of the device can be simplified, and work such as battery replacement is freed.
Easy to maintain.

In addition, since the pressure gauge is attached to the outer periphery of the cylinder assembly, there is no need to connect an external measuring device etc. via lead wires, making the measurement operation easy. Since the cylinder assembly and pressure gauge are installed on the opposite side of the groove where the taper shank is formed, the cylinder assembly and pressure gauge are offset from the tool gripping groove gripped by the automatic tool changer, and the cylinder assembly and pressure gauge are positioned on the opposite side of the groove where the taper shank is formed. The cylinder assembly and pressure gauge do not get in the way during the automatic mounting operation of the device, and the device can be smoothly attached to and removed from the machine tool.

Furthermore, since the pressure gauge is attached to the outer periphery of the cylinder assembly so as to protrude from the outer periphery in a direction perpendicular to the rod axis direction, a measuring device can be attached to the main shaft to measure the tool holding force. In this case, the measured value will be located on the side of the measuring device on the left side of the main shaft in Figure 2, and the measured value of the pressure gauge can not only be read easily and safely from outside the machine tool body, but also Since the pressure gauge does not protrude in the axial direction of the rod, even if the pressure gauge is made larger to improve visibility from the outside, the pressure gauge and the workpiece being machined (usually located on the left side of Figure 2) The risk of interference with the object (where the work is located) can be significantly reduced, making it possible to improve the reliability of measurement.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a main shaft portion of a machining center whose holding force is to be measured, and FIG. 2 is a sectional view showing an embodiment of a tool holding force measuring device according to the present invention. 12... Tool holding force measuring device, 13... Main body, 13
a... Connection part (taper shank), 15a... Cylinder, 16... Piston, 17... Incompressible fluid (pressure oil), 19... Rod, 19a... Pull stud, 2
1...Pressure gauge.

Claims (1)

[Scope of Claims] 1. A main body having a taper shank attached to the main shaft of a machine tool and a tool gripping groove for automatic tool changing, and a rod is inserted into the main body so as to pass through the main body. a pull stud is provided at the end of the rod on the tapered shank side, and a pull stud is provided on the opposite side of the main body in the axial direction from the part where the taper shank is formed with respect to the tool gripping groove;
A cylinder assembly is attached to the main body so as to be in series in the axial direction of the rod, a cylinder is formed in the cylinder assembly, and a piston is fitted into and engaged with the cylinder so as to be movable in the axial direction of the rod. and connecting the piston and rod, sealing an incompressible fluid in the cylinder, and providing a pressure gauge on the outer periphery of the cylinder assembly that can display the pressure of the incompressible fluid in the cylinder. A pressure transmission flow is provided in the cylinder assembly so as to protrude from the outer circumference in a direction perpendicular to the rod axis direction, and is capable of transmitting the pressure of the incompressible fluid in the cylinder to the pressure gauge. A tool holding force measuring device configured by forming a path connecting the pressure gauge and the cylinder.