Machine tool

Abstract

Provided is a machine tool having rib structures of a bed according to attachment states of machining devices. When the machine tool is constituted of a plurality of machining devices for executing machining of a workpiece, the machining devices are a fixing device fixed to the bed having a hollow structure and a movable device movably attached to the bed. Thus, a support part, of the bed, that is in contact with a floor surface is divided into a plurality of support parts. The support part on which the fixing device is mounted has a first rib structure in which rigidity is increased. The support part on which the movable device is mounted has a second rib structure in which rigidity is lower than that of the first rib structure.

Description

machine tools

[0001] The present invention relates to a machine tool in which a bed carrying a plurality of processing devices for processing a workpiece is configured according to the operating conditions of the processing devices.

[0002] Machine tools are comprised of a bed mounted with various machining devices, such as a spindle device that rotatably grips the workpiece to be machined, and a turret device equipped with a tool rest that holds multiple tools. Because machine tools require high workpiece machining precision, they must also suppress the effects of machining vibrations that occur during machining. Therefore, increasing the rigidity of a machine tool bed by increasing its mass is considered possible, but simply increasing the mass not only increases costs but also increases the workload for transportation and installation. Therefore, beds, which are typically cast metal, are formed hollow and have a ribbed structure inside to ensure overall rigidity.

[0003] The conventional example disclosed in Patent Document 1 below is a machine tool having a bed formed in a generally T-shape, with a work table mounted on a sliding surface provided on the top surface of the bed in the Z-axis direction and configured to move by driving a feeder. The tool rest is mounted on a movable base on a sliding surface provided on the top surface of the bed in the X-axis direction and configured to move by driving a feeder. The rib structure of the bed of this machine tool is such that the top plate is supported at three points by three plate-like support columns and three cylindrical support columns. The cylindrical support columns, which are spaced apart, are connected by reinforcing ribs, ensuring sufficient rigidity for the bed.

[0004] Japanese Patent Application Laid-Open No. 2005-131768

[0005] To achieve high machining accuracy, machine tools are required to suppress vibrations that occur during machining on the bed on which the various processing devices are mounted. Therefore, the above-mentioned conventional example also discloses a rib structure for increasing the rigidity of the bed. However, simply increasing the rigidity of the bed may result in undesirable phenomena. This is because the various processing devices that make up a machine tool may have different mounting structures on the bed. That is, in some cases, the processing devices are firmly fixed to the bed, and in other cases, the processing devices are mounted in a state where they can move along a guide rail. If each processing device with such different mounting structures were supported with the same high rigidity, it would be impossible to suppress vibrations that occur in the processing devices on the guide rail during machining.

[0006] SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to provide a machine tool having a bed rib structure that corresponds to the mounting state of a processing device.

[0007] In one aspect of the present invention, a machine tool is composed of a plurality of processing devices for processing a workpiece, the processing devices comprising a fixed device fixed to a hollow bed and a movable device movably attached to the bed, the bed having a plurality of support parts that come into contact with the floor surface, the rib structure of the support parts on which the fixed devices are mounted being a first rib structure with increased rigidity, and the rib structure of the support parts on which the movable devices are mounted being a second rib structure with reduced rigidity compared to the first rib structure.

[0008] According to the above configuration, when a workpiece is processed using a fixed device, the vibrations associated with the processing are suppressed because the fixed device is fixed at the support portion of the first rib structure, and when a workpiece is processed using a movable device, the vibrations associated with the processing are transmitted to and absorbed by the support portion of the second rib structure on which the movable device is mounted.

[0009] FIG. 1 is a perspective view of an internal structure of a machine body showing one embodiment of a machine tool; FIG. 2 is a perspective view showing a bed from above with a processing device removed; FIG. 3 is a perspective view of a front cross section showing the bed; FIG. 4 is a perspective view of the underside of the bed; and FIG. 5 is a bottom view showing the bed.

[0010] An embodiment of a machine tool according to the present invention will be described below with reference to the drawings. Fig. 1 is a diagram showing the machine tool of this embodiment, and is a perspective view showing the internal structure of the machine body. The machine tool 1 of this embodiment is an NC lathe, and various processing devices for processing a workpiece are mounted on a bed 7. The machine tool 1 is provided with, as processing devices for processing the workpiece, a first workpiece spindle unit 3 that rotatably grips the workpiece, a second workpiece spindle unit 4 disposed opposite the first workpiece spindle unit 3, and a turret unit 5 that has a plurality of tools.

[0011] As shown in Fig. 2, the bed 7 of the machine tool 1 is a slant-type bed inclined so that the front side is lower, and the first work spindle unit 3 is disposed on the left side of the inclined front surface when viewed from the front of the machine body, and the second work spindle unit 4 and turret unit 5 are disposed on the right side. Fig. 2 is a perspective view showing the bed 7 from above with the first work spindle unit 3 and other processing devices removed. Furthermore, the first work spindle unit 3 is a fixed device that is firmly fixed to the bed 7, while the second work spindle unit 4 and turret unit 5 are movable devices that are assembled so as to be movable on the bed 7. Note that "left and right" described in this embodiment refer to the width direction of the machine body when viewed from the front of the machine body.

[0012] The first work spindle device 3 is designed so that its center line is in the width direction of the machine body and is horizontal, while the second work spindle device 4 and the first work spindle device 3 have their spindles arranged coaxially. In this embodiment, the direction parallel to the spindle of the first work spindle device 3 (the width direction of the bed 7) will be described as the Z axis. Therefore, the second work spindle device 4, which is coaxial with the first work spindle device 3, is mounted on the bed 7 so as to move in a direction parallel to the Z axis. The second work spindle device 4 is arranged in front on the right front part of the bed 7, and the turret device 5 is arranged at a higher position behind it.

[0013] The first workpiece spindle device 3 has a spindle rotatably mounted on a cylindrical headstock 11, to which is attached a chuck mechanism 12 for gripping and releasing a workpiece. The chuck mechanism 12 has three chuck jaws arranged radially, and grips and releases the workpiece by converting the extension and contraction movement of the cylinder into opening and closing movement in the radial direction. The spindle is configured so that the rotation shaft of a motor is transmitted to the spindle, so that the workpiece gripped by the chuck mechanism 12 can be phased during machining and rotated at a predetermined speed. The first workpiece spindle device 3 has a pedestal 13 attached integrally to the headstock 11, and the pedestal 13 is firmly fixed to a fixed portion 15 of the bed 7 with bolts.

[0014] On the other hand, the second work spindle device 4, like the first work spindle device 3, has a rotatable spindle mounted on a headstock 21, and a coaxial chuck mechanism 22 opposed to the chuck mechanism 12 is mounted on the headstock 21. Like the chuck mechanism 12, the chuck mechanism 22 has three radially arranged chuck jaws that convert the extension and retraction movement of a cylinder into opening and closing movement in the radial direction, thereby gripping and releasing the workpiece. The spindle is configured so that the rotation shaft of a motor can be transmitted, so that the workpiece gripped by the chuck mechanism 22 can be phased during machining and rotated at a predetermined speed.

[0015] The second workpiece spindle device 4 is mounted on a spindle slide 23 and configured to move in the Z-axis direction on the front inclined surface of the bed 7. As shown in FIG. 2 , two guide rails 25 parallel to the Z-axis are fixed to the front inclined surface of the bed 7, and a guide block fixed to the underside of the spindle slide 23 is slidably engaged with them. The second workpiece spindle device 4 is movable in the Z-axis direction by a ball screw mechanism, and a screw shaft 26 parallel to the Z-axis is supported via bearings between the two guide rails 25. A Z-axis servo motor 27 is provided on the outer side in the width direction of the machine body, and its rotation shaft is connected to the screw shaft 26. Meanwhile, a nut member through which the screw shaft 26 passes is fixed to the spindle slide 23, and the rotation output of the Z-axis servo motor 27 causes linear movement of the spindle slide 23 in the Z-axis direction.

[0016] Next, the turret device 5 selects a suitable tool T from a plurality of tools T by rotating and indexing, and performs predetermined machining such as turning or drilling on the workpiece. The turret device 5 is configured such that a plurality of tools T are attached to a disk-shaped tool rest 31 at equal intervals in the circumferential direction, and any tool T can be positioned at a machining position on the circumference by controlling the rotation of an indexing servo motor 32. This makes it possible to perform predetermined machining using the tool T on a workpiece held by the first or second workpiece spindle device 3, 4.

[0017] The turret device 5 is configured to move the tool rest 31 in the Z-axis direction, as well as in the Y-axis and X-axis directions perpendicular to the Z-axis, in order to move the tool T to the workpiece held by the first workpiece spindle device 3. The turret device 5 is mounted on a Z-axis slide that can move in the Z-axis direction on the bed 7. A guide rail 33 parallel to the guide rail 25 of the second workpiece spindle device 4 is provided on the upper part of the front inclined surface of the bed 7, and a guide block fixed to the underside of the turret Z-axis slide 34 slidably engages with the guide rail 33. The turret device 5 is configured to be movable in the Z-axis direction by a ball screw mechanism.

[0018] A screw shaft 35 parallel to the Z-axis is supported between the two guide rails 33 via bearings, and the screw shaft 35 passes through a nut member fixed to the turret Z-axis slide 34. A Z-axis servo motor 36 is provided on the front inclined surface of the bed 7 above the first workpiece spindle device 3, and its rotation shaft is connected to the screw shaft 35. Therefore, the rotation output of the Z-axis servo motor 36 is transmitted to the screw shaft 35, causing the turret Z-axis slide 34 to move linearly in the Z-axis direction.

[0019] The upper surface of the turret Z-axis slide 34 is inclined forward at 45 degrees, the same as the inclination of the bed 7, and this inclination is set as the X-axis. An X-axis guide rail is formed on the upper surface of the turret Z-axis slide 34, and the turret X-axis slide 37 is attached so as to slide along this guide rail. The front surface of the turret X-axis slide 37 is a vertical surface, and the direction parallel to this vertical surface is set as the Y-axis. Therefore, a Y-axis guide rail is formed on the front surface of the turret X-axis slide 37, and a turret main body 38, including the tool post 31 and the indexing servo motor 32, is attached so as to slide along this guide rail. The turret X-axis slide 37 and the turret main body 38 are also configured to be able to move linearly in the Z-axis direction by a ball screw mechanism.

[0020] A screw shaft (not shown) connected to an X-axis servomotor 41 is supported via a bearing on the turret Z-axis slide 34, and the screw shaft passes through a nut member fixed to the turret X-axis slide 37. Similarly, a screw shaft (not shown) connected to a Y-axis servomotor 42 is supported via a bearing on the turret X-axis slide 37, and the screw shaft passes through a nut member fixed to the turret main body 38. Therefore, the rotational outputs of the X-axis servomotor 41 and the Y-axis servomotor 42 cause the turret X-axis slide 37 to move linearly in the X-axis direction, and the turret main body 38 to move linearly in the Y-axis direction.

[0021] The machine tool 1 configured as described above is capable of first machining of a workpiece held by the first workpiece spindle device 3, and second machining of a workpiece held by the second workpiece spindle device 4. Specifically, a workpiece is held by the chuck mechanism 12 of the first workpiece spindle device 3, and predetermined machining is performed on the workpiece by the turret device 5. The turret device 5 controls the drive of the indexing servo motor 32, and a predetermined tool T to perform machining is swiveled and indexed from the plurality of tools T attached to the tool rest 31.

[0022] The turret device 5 controls movement in each axis direction to position the tool T at a machining position relative to the workpiece. That is, the turret body 38 moves from the right side to the left side of the bed 7 along the Z axis, which is the width direction of the machine body, by drive control of the Z axis servo motor 36, and further moves along the combined X and Y axes in the front-to-rear and up-to-down directions of the machine body by drive control of the X axis servo motor 41 and the Y axis servo motor 42. The tool T, which has been swiveled and indexed, is positioned by these movements, and the workpiece is subjected to external machining using a cutting tool or hole drilling using a drill.

[0023] Next, the machine tool 1 performs a second machining operation using the second workpiece spindle device 4. During the second machining operation, the second workpiece spindle device 4 is moved from the right side to the left side of the bed 7 along the Z axis, which is the width direction of the machine body, by drive control of the Z-axis servo motor 27. The chuck mechanism 22 of the second workpiece spindle device 4 then receives the workpiece held by the chuck mechanism 12 of the first workpiece spindle device 3. At this time, the workpiece is turned over, making it possible to machine the back side of the workpiece by the second machining operation. Having gripped the workpiece, the second workpiece spindle device 4 is again moved from the left side to the right side along the width direction of the machine body by drive control of the Z-axis servo motor 27, and returns to its original position.

[0024] Then, in order to perform the second machining on the workpiece gripped by the second workpiece spindle device 4, the tool T in the turret device 5 is rotated and indexed and moved to the machining position. As in the first machining described above, the turret body 38 is moved to the right side of the bed 7 by drive control of the Z-axis servo motor 36, and is moved in the front-to-rear and up-to-down directions of the machine body by drive control of the X-axis servo motor 41 and the Y-axis servo motor 42. There, predetermined cutting machining, such as internal diameter machining, is performed on the workpiece.

[0025] Next, the machine tool 1 of this embodiment, which requires high machining accuracy, is characterized by the structure of the bed 7, which is designed to accommodate vibrations during machining. Figures 3 to 5 show the bed 7, with Figure 3 being a perspective view of the front cross section, Figure 4 being a perspective view of the underside, and Figure 5 being a bottom view. The bed 7 is made of cast iron and is configured to have a hollow interior. Ribs are integrally molded into the hollow interior, thereby ensuring a certain level of rigidity for the bed 7. In particular, the reinforcing rib structure of the bed 7 of this embodiment is not simply intended to increase rigidity, but is designed to provide rigidity in accordance with the mounting state of the machining devices, such as the first workpiece spindle unit 3, that are mounted on the bed.

[0026] In the machine tool 1, the first work spindle device 3 is firmly attached to the bed 7 by bolts, while the second work spindle device 4 and turret device 5 are attached so as to be movable relative to the bed 7 via guide rails 25, 33. Therefore, while the first work spindle device 3 is firmly fixed to the bed 7, the second work spindle device 4, which is not directly fixed to the bed 7, is prone to vibrations that reduce machining accuracy during the second machining operation. The bed 7 generates differences in the rigidity of the parts that support each of the machining devices that make up the machine tool 1, depending on how they are attached.

[0027] The bed 7 has a bottom that contacts the factory floor and is divided into multiple support sections. In this embodiment, support sections 45, 46 are separated into left and right sides of the bed 7 to correspond to the machining positions, with an intermediate section 47 provided in the center. The support sections 45, 46 are formed with square frames 51, 52 of the same size, each with a different rib structure provided therein. In particular, the support section 45 side, where the first workpiece spindle device 3 is located, has a first rib structure 55 with high rigidity, while the support section 46 side, where the second workpiece spindle device 4 and turret device 5 are located, has a second rib structure 57 designed to have relatively lower rigidity. The frames 51, 52 are surrounded by front, rear, left, and right walls, and grooves 511, 521 are formed in parts of the front and rear to accommodate the forks of a forklift.

[0028] The rib structures within the support parts 45, 46 each have central ribs 551, 571 extending in the front-rear direction, which are connected to the front and rear wall surfaces and top surfaces of the underframes 51, 52. The first rib structure 55 of the support part 45 is integrally formed with diagonal ribs 553 that extend diagonally forward on both the left and right sides from the central rib 551 and are also connected to the top surface. On the other hand, the low-rigidity rib structure 57 of the support part 46 has parallel ribs 573 that are symmetrically arranged on both the left and right sides of the central rib 571 at a certain distance, and are connected to the front-rear wall surfaces and top surface, just like the central rib 571. Therefore, the difference between the first rib structure 55 and the second rib structure 57 results in a difference in rigidity between the support parts 45, 46.

[0029] The first rib structure 55 of the support part 45 is reinforced by a central rib 551 and two diagonal ribs 553 that support each other, thereby increasing the rigidity of the fixed part 15 of the bed 7. The first rib structure 55 shown in this embodiment is just one example, and if higher rigidity is required, the number of ribs can be increased in the support part 45, and the positions and directions of the added ribs can also be designed based on analysis, etc. The first machining performed at the position of the support part 45 having such a first rib structure 55 generates resistance due to turning, etc., when the tool T contacts the rotating workpiece, but vibration is suppressed by the first workpiece spindle device 3, which is firmly supported.

[0030] On the other hand, the second rib structure 57 of the support part 46 has a certain level of rigidity due to the configuration in which the central rib 571 and two parallel ribs 573 are arranged side by side, but is designed to have lower rigidity than the first rib structure 55 on the support part 45 side. This is because if the rigidity of the support part 46 were as high as that of the support part 45, the second work spindle device 4 itself would vibrate due to the low rigidity of the assembly part with the guide rail 25. Therefore, in this embodiment, the rigidity of the second rib structure 57 of the support part 46 is designed so that vibrations transmitted to the assembly part between the second work spindle device 4 and the guide rail 25 are transmitted to the bed 7.

[0031] As described above, the second machining of the machine tool 1 is performed on the support part 46 located on the right side of the bed 7. In this embodiment, even if vibrations occur in the second workpiece spindle device 4 during the second machining of the workpiece held by the chuck mechanism 22, the vibrations will be transmitted to the support part 46 of the second rib structure 57. Therefore, even with a movable mounting structure such as the second workpiece spindle device 4, the vibrations caused by machining are absorbed by the support part 46, and it is possible to prevent the vibrations of the second workpiece spindle device 4 from increasing.

[0032] Furthermore, the machine tool 1 of this embodiment is compactly constructed despite having opposed spindles capable of machining both sides of a workpiece through the first and second machining processes. Therefore, the first and second machining processes are performed in close proximity, but because the bottom of the bed 7 is separated by the supports 45, 46 and has rib structures with different rigidities (first rib structure 55 and second rib structure 57), appropriate vibration prevention effects are obtained for each machining process. Furthermore, the first rib structure 55 has a simple structure consisting of a central rib 551 and diagonal ribs 553 within a square frame 51, and the second rib structure 57 has a simple structure consisting of a central rib 571 and parallel ribs 573 within a square frame 52, making it suitable for manufacturing cast iron beds.

[0033] Although one embodiment of the present invention has been described, the present invention is not limited to this and various modifications are possible without departing from the spirit of the present invention. In the above embodiment, the machine tool 1 configured with a slant-type bed has been shown and described, but the present invention is not limited to this and can be applied to various types of machine tools.

[0034] REFERENCE SIGNS LIST 1 machine tool 3 first workpiece spindle device 4 second workpiece spindle device 5 turret device 7 bed 15 fixed portion 25, 33 guide rails 45, 46 support portion 47 intermediate portion 51, 52 frame 55 first rib structure 57 second rib structure 551 central rib 553 diagonal rib 571 central rib 573 parallel rib

Claims

1. A machine tool which is composed of a plurality of processing devices for processing a workpiece, the processing devices being fixed devices fixed to a hollow bed and movable devices movably attached to the bed, the bed having a plurality of support parts which come into contact with the floor surface, the support parts on which the fixed devices are mounted having a first rib structure with increased rigidity, and the support parts on which the movable devices are mounted having a second rib structure with reduced rigidity compared to the first rib structure.

2. A machine tool as described in claim 1, wherein the support portion has the first rib structure or the second rib structure provided inside a square frame formed at the bottom of the bed.

3. A machine tool as described in claim 2, wherein said first rib structure comprises a central rib extending in the front-to-rear direction inside said frame, said central rib being connected to the wall surface and the top surface, and diagonal ribs extending from said central rib to both the left and right sides being also connected to the top surface.

4. A machine tool as described in claim 3, wherein said second rib structure comprises a central rib extending in the front-to-rear direction inside said frame, connected to the wall surface and top surface, and parallel ribs arranged symmetrically at a fixed distance on both the left and right sides of said central rib, also connected to the top surface.

5. A machine tool as described in any one of claims 1 to 4, wherein a first work spindle device which rotates a work held in a first spindle chuck is provided as the fixed device, a second work spindle device which is arranged opposite to the first work spindle device and rotates a work held in a second spindle chuck, and a turret device equipped with a tool for machining a work held by the first work spindle device or the second work spindle device are provided as the movable device.

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