Machine tool

Abstract

To provide a machine tool which has a structure to eliminate deviation of a temperature of a bed.SOLUTION: A machine tool includes a plurality of machining devices each of which is independently movable along a plurality of parallel rails provided in an assembling section of a bed. In the machine tool, a coolant flow passage for making coolant flow passes through the bed in a direction in parallel with the rails and is formed in the vicinity of a center of the plurality of rails arranged in parallel with each other. For instance, the coolant flow passage is provided in the vicinity of the center so that the plurality of parallel rails is symmetrically positioned. For instance, the bed is a slant type inclined forward, and the plurality of rails is fixed in a front side inclined portion in a horizontal direction and is arranged in a vertical direction. For instance, the bed has a hollow rib structure and a side groove for receiving coolant leaking out from a hole opened in the coolant flow passage is formed along and in parallel with the coolant flow passage.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a machine tool having a structure for eliminating unevenness in the temperature of a bed and achieving uniformity. [Background technology]

[0002] In machine tools, for example, in a lathe, a tool on a tool post moves relative to a workpiece held by a spindle to perform a specific machining operation such as turning. Since such machine tools require machining accuracy in the micron range, the positioning of the tool during machining is required to be accurate as the tool moves. However, the bed on which the spindle device and tool post are mounted may be affected by temperature changes, which may reduce machining accuracy. This is because such beds are made of cast iron, and changes in temperature cause thermal deformation, which reduces the positioning accuracy of the tool. Factors that cause changes in the temperature of the bed include, for example, temperature changes in the factory due to the outside air and heat generated by the machine tool itself. In addition, the bed is a base on which other elements of the machine tool are attached, and is required to have damping properties.

[0003] The following Patent Document 1 discloses a machine tool equipped with a thermal stabilization device that reduces thermal displacement on the back side, addressing the issue that the machining dimensional accuracy of the tool rest of the slant bed is unstable due to thermal displacement. Such a conventional machine tool has a saddle that can slide in the width direction of the machine body on the front side of the slant bed, and a turret device is mounted so as to slide in the front-rear direction of the machine body. A water jacket is provided on the back side of such a slant bed as a thermal stabilization device. Since the thermal expansion of the slant bed is larger in proportion to the length of the back side than the front side due to its shape, a U-shaped water jacket is provided along the back side to allow cooling water to circulate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 6-642 Summary of the Invention [Problem to be solved by the invention]

[0005] The machine tool has a spindle mounted on a headstock fixed to the front side of the legs, a slant bed fixed to the rear side of the legs, and a turret device movably mounted thereon as described above. In this conventional example, the spindle and the turret device are mounted on separate stands, and although the temperature of the slant bed side on which the turret device is mounted is controlled, no measures are taken for the spindle side, which may be affected by heat generated by the spindle motor. In order to obtain high machining accuracy in a machine tool, it is preferable that the relationship between the spindle that grips the workpiece and the turret device that applies a tool to the workpiece is constant, and it is considered necessary to consider thermal deformation of the entire machine tool. In this respect, the conventional example has not taken sufficient measures.

[0006] SUMMARY OF THE PRESENT EMBODIMENT In order to solve the above problem, an object of the present invention is to provide a machine tool having a structure for eliminating temperature deviation of the bed. [Means for solving the problem]

[0007] The machine tool of the present invention has a plurality of processing devices, each of which can move independently along a plurality of parallel rails provided in an assembly portion of a bed, and a coolant flow path for flowing coolant penetrates the bed in a direction parallel to the rails and is formed near the center of the plurality of parallel rails. Effect of the Invention

[0008] According to the above configuration, although heat generated by a motor or the like in a machine tool during workpiece machining is transferred to the bed, the coolant flows through a coolant flow passage formed near the center of multiple parallel rails, thereby removing the heat, thereby suppressing localized temperature increases and eliminating temperature bias in the bed. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view showing an internal structure of a machine body in one embodiment of a machine tool. [Diagram 2] FIG. 2 is a perspective view showing a bed of a machine tool. [Diagram 3] FIG. 2 is a side view showing the bed of the machine tool. [Figure 4] FIG. 2 is a perspective view showing a cross section of a bed of a machine tool as viewed in a width direction. [Diagram 5] FIG. 11 is a perspective view showing a second example of a bed. [Figure 6] FIG. 11 is a side view showing the bed of the second example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 a machine tool of this embodiment, and is a perspective view showing the internal structure of the machine body in particular. The machine tool 1 of this embodiment is an NC lathe, and various processing devices for processing a workpiece are mounted on a slant-type bed 6. The machine tool 1 is provided with a first workpiece spindle device 3 that rotatably holds a workpiece, a second workpiece spindle device 4 disposed opposite the first workpiece spindle device 3, and a turret device 5 having a plurality of tools T, as processing devices for executing processing of the workpiece.

[0011] 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, and the second work spindle device 4 is arranged so that its spindle is coaxial with that of the first work spindle device 3. In this embodiment, the direction parallel to the spindle of the first work spindle device 3 (the width direction of the bed 6) is described as the Z axis. The second work spindle device 4, which is coaxial with the first work spindle device 3, is mounted on the bed 6 so as to move in the left-right direction parallel to the Z axis.

[0012] The first work spindle device 3 has a rotatable spindle mounted on a headstock 11, and a chuck mechanism 12 attached thereto is rotated by a spindle motor to rotate the gripped workpiece. Similarly, the second work spindle device 4 has a rotatable spindle mounted on a headstock 15, and a chuck mechanism 16 attached thereto is rotated by a spindle motor. In the first work spindle device 3, the headstock 11 is integrated with a pedestal 13, and the pedestal 13 is fixed to the bed 6, but the second work spindle device 4 is mounted on a spindle slide 14 and configured to move in the Z-axis direction.

[0013] Two guide rails 18 parallel to the Z-axis are fixed to the front inclined portion of the bed 6, and a guide block fixed to the underside of the main spindle slide 14 slidably engages with them. A screw shaft 19 parallel to the Z-axis is journaled between the two guide rails 18, and the rotating shaft of a Z-axis servo motor 20 is connected to the screw shaft 19. A nut member through which the screw shaft 19 passes is fixed to the main spindle slide 14, and a ball screw mechanism is configured so that the rotation output of the Z-axis servo motor 20 causes the main spindle slide 14 to move linearly in the Z-axis direction.

[0014] A turret device 5 is disposed behind the second workpiece spindle device 4, and its tool rest 21 is configured to move in the Z-axis direction, and in the Y-axis and X-axis directions perpendicular to the Z-axis. In the turret device 5, a guide block fixed to the underside of a turret Z-axis slide 24 slidably engages with two guide rails 23 fixed to the front inclined portion of the bed 6. A screw shaft 25 parallel to the Z-axis is supported between the two guide rails 23 via bearings, and the screw shaft 25 passes through a nut member fixed to the turret Z-axis slide 24. A rotating shaft of a Z-axis servo motor 26 is connected to the screw shaft 25, and a ball screw mechanism is configured so that the turret Z-axis slide 24 moves linearly in the Z-axis direction by the rotation output of the screw shaft 25.

[0015] A turret X-axis slide 27 is attached to the turret Z-axis slide 24 so as to slide on an X-axis guide rail formed on the top surface, and a turret body 28 including the tool rest 21 and the indexing servo motor 22 is attached to the turret X-axis slide 27 so as to slide on a Y-axis guide rail formed on the front surface of the turret X-axis slide 27. A ball screw mechanism is configured so that the turret Z-axis slide 24 and the turret body 28 are both moved in the respective axial directions by the rotational output of an X-axis servo motor 29 and a Y-axis servo motor 30.

[0016] Next, in the workpiece machining in the machine tool 1, the tool T attached to the tool rest 21 is turned and indexed, and the tool T is controlled to move to a machining position. The turret body 28 moves the corresponding tool T to a machining portion of a workpiece held by the first or second workpiece spindle device 3, 4 to be machined, by moving in the Z-axis direction by drive control of the Z-axis servo motor 26 and by combining the X-axis and Y-axis by drive control of the X-axis servo motor 29 and the Y-axis servo motor 30. There, for example, an external diameter turning process is performed by abutting the cutting edge of the tool T, which is a cutting tool, against the rotating workpiece. In the machine tool 1, the second workpiece spindle device 4 moves to the first workpiece spindle device 3 side according to drive control of the Z-axis servo motor 20, and the workpiece is transferred between the chuck mechanisms 12, 16, and the back side of the workpiece can also be machined as desired.

[0017] However, even with this machine tool 1, in order to maintain machining accuracy, measures against thermal deformation of the bed 6 are necessary, as in the conventional example. In this regard, the machine tool 1 of this embodiment has the first and second work spindle devices 3, 4 and the turret device 5 mounted on a single bed 6, and is configured to eliminate temperature bias in the bed 6 and achieve overall uniformity. In particular, since the various machining devices are mounted on the front inclined portion (assembly section) 65, the machine tool 1 is configured to mainly reduce temperature changes in the assembly section 65.

[0018] Possible causes of the temperature change include heat generated by the Z-axis servo motors 20, 26 when they are driven, and frictional heat in the sliding parts and ball screw mechanisms that transmit drive when the spindle slide 14 and the turret Z-axis slide 24 are moved. Therefore, in the machine tool 1, the assembly part 65 is susceptible to the effects of such heat generation, causing an uneven temperature distribution in the bed 6. This is thought to cause distortion that disrupts the straightness of the spindle slide 14 and the turret Z-axis slide 24 that move on the guide rails 18, 23, resulting in a decrease in the machining accuracy of the machine tool 1.

[0019] Therefore, it is possible to control the thermal deformation of the bed as in the conventional example, but it is difficult to suppress uneven thermal deformation with a water jacket provided on the back, and the water jacket is a new component added to the machine tool, which hinders miniaturization and increases costs. Therefore, in this embodiment, a machine tool 1 is proposed that eliminates local temperature unevenness and eliminates temperature unevenness in the entire bed 6 or the assembly part 65, which has a large effect on processing accuracy, to achieve uniformity. This is because, even if there is a temperature change, if the entire bed 6 or the assembly part 65 is uniform, the movement of the tool T can maintain processing accuracy even if thermal deformation occurs by performing correction control processing.

[0020] Here, FIG. 2 is a perspective view showing the bed 6, and FIG. 3 is a side view showing the bed 6. In this embodiment, in order to eliminate temperature bias in the entire bed 6 or mainly in the assembly part 65, a coolant used for cleaning chips and cooling the processing part flows inside the bed 6. The bed 6, which is a casting, is formed in a hollow shape, and a rib structure is provided inside to ensure the rigidity of the entire bed. A coolant flow path 31 is formed in the bed 6, penetrating the bed 6 in the machine body width direction. The coolant flow path 31 is formed to be located between the guide rails 18 and 23 and to be parallel to each of the guide rails 18 and 23, taking into consideration the effect on the processing control of the workpiece by the tool T.

[0021] The bed 6 shown in Figs. 2 and 3 has rail bases 35, 36 for fixing the guide rails 18, 23 to the mounting portion 65. The coolant flow passage 31 is disposed so as to be located near the center of the four rail bases 35, 35, 36, 36 arranged in parallel. That is, it is disposed between the second rail base 35 and the third rail base 36 from the bottom among the four rail bases. When the bed 6 shown in Fig. 3 is viewed from the side, the coolant flow passage 31 is formed at a position where the center line 37 perpendicular to the front angle (45 degrees) of the bed 6 indicating the center is symmetrical with the multiple rails 33, 34. Note that the shape of the coolant flow passage 31 is affected by the rib structure of the bed 6, so the center line 37 does not indicate the strict center position.

[0022] Next, in this embodiment, a supply port 33 of the coolant flow passage 31 is formed on the left side surface of the bed 6 shown in Fig. 2, and a discharge port 34 is formed on the opposite right side surface. Coolant piping is connected to the supply port 33 and the discharge port 34, which are closed, and the coolant flow passage 31 becomes part of the coolant device provided in the machine tool 1. The coolant device allows the coolant sprayed during machining to be collected in a coolant tank under the bed 6 and filtered through a filter, etc., to be used repeatedly. That is, the coolant pumped up from the coolant tank is sent to the machining section through the coolant flow passage 31 and sprayed repeatedly.

[0023] Even if the supply port 33 and the discharge port 34 of the coolant passage 31 are blocked, the side hole 41 is opened due to the hollow structure of the bed 6 as shown in the enlarged part of FIG. 4. This is because the bed 6 has a plurality of holes for convenience in casting, and the coolant passage 31 cannot be made into a sealed space. Here, FIG. 4 is a perspective view showing a cross section of the bed 6 as seen in the width direction. Therefore, as shown in the figure, the coolant cannot be filled in the entire cross section of the coolant passage 31, and the position of the side hole 41 is the upper limit of the liquid level. The coolant may exceed the upper limit. In that case, the coolant in the coolant passage 31 overflows from the side hole 41 and flows onto the factory floor.

[0024] Therefore, a weir 42 is formed outside the coolant flow path 31 and below the horizontal hole 41. The weir 42 is formed in a convex shape on the inclined wall surface located outside the coolant flow path 31, and continues in the width direction of the bed 6. This weir 42 forms a side gutter 43 that receives the coolant leaked from the horizontal hole 41 and runs parallel to the coolant flow path 31. The side gutter 43 is closed by the side surface of the bed 6, and a drain port 39 is formed there, as shown in FIG. 3. The drain port 39 is connected to the same secondary coolant piping as the drain port 34, so that the leaked coolant is returned.

[0025] Therefore, when the machine tool 1 is in operation, coolant flows through the coolant flow passage 31 as the coolant device is driven. When the machine tool 1 processes a workpiece as described above, the coolant is used to cool the machining portion where the tool T contacts the workpiece and to wash away chips generated during workpiece machining. The coolant sprayed onto the machining portion flows down the floor of the machining chamber and is stored in a coolant tank, and the chips are removed by driving the chip conveyor. The coolant is also filtered by passing through a cyclone filter, etc., and is pumped up by a coolant pump and supplied to the machining chamber again.

[0026] In the coolant device, a supply port 33 is connected to a primary coolant pipe, from which the coolant flows into a coolant flow passage 31, which becomes filled with a certain amount of coolant as shown in Figures 3 and 4. The coolant that flows through the coolant flow passage 31 is then sent from the discharge port 34 through the secondary coolant pipe to the machining chamber. At this time, since the coolant in the coolant flow passage 31 is not receiving the supply pressure of a coolant pump connected to the primary coolant pipe, a supply pump is provided on the secondary coolant pipe connected to the discharge port 34, and the coolant is sent and sprayed into the machining chamber by the discharge pressure of the supply pump.

[0027] In the machine tool 1 during machining of a workpiece, heat generated from the Z-axis servo motors 20, 26 and the ball screw is transferred to the bed 6. In the past, the heat caused a local temperature rise in the bed 6, but in this embodiment, the heat of the bed 6 is taken away by the coolant flowing through the coolant passage 31. Therefore, in the bed 6 during operation of the machine tool 1, the temperature difference in the assembly section 65 is reduced and the temperature is uniformed by suppressing a local temperature rise. Therefore, even if thermal deformation occurs in the bed 6, the straightness of the spindle slide 14 and the turret Z-axis slide 24 that move along the guide rails 18, 23 is maintained. In addition, the positioning of the tool T during machining can maintain the target machining accuracy by driving accompanied by a correction control process.

[0028] In the machine tool 1, the Z-axis servo motors 20, 26 and ball screws, which serve as heat sources, are disposed in relation to the guide rails 18, 23. In this embodiment, the coolant flow path 31 is formed near the center so as to be located between both guide rails 18, 23, so that it is possible to eliminate uneven absorption of heat generated at various locations, and it is possible to reduce the temperature difference at the assembly portion 65 of the bed 6 as described above.

[0029] Incidentally, the temperature change in the machine tool 1 is affected by the outside air temperature in the case of the machine body cover, and the temperature of the bed 6 is affected by heat generated by the motor and the like as described above. Furthermore, the temperature of the coolant also rises due to flowing through the coolant flow passage 31, flowing hot chips, and washing the floor of the machining room. In this way, the temperature of the machine tool 1 changes in various ways depending on the season, time of day, duration of machining, and the like. In regard to this point, the machine tool 1 has a configuration in which a temperature control device is connected to the coolant piping of the coolant device, and is capable of cooling the coolant. Therefore, it is possible to eliminate temperature bias in the bed 6 while controlling the temperature of the coolant according to various conditions.

[0030] Furthermore, in the machine tool 1 of this embodiment, a large amount of coolant is stored inside the bed 6. Thus, in the machine tool 1, the vibrations generated during machining of a workpiece are absorbed by the coolant, and the coolant flow path 31 containing the coolant exhibits a vibration suppression effect.

[0031] Next, a bed of a different machine tool will be described as a second example. Fig. 5 is a perspective view showing the bed of the second example, and Fig. 6 is a side view showing the bed of the second example. Although the specific configuration of the machine tool is not shown, the turret device 5 shown in Fig. 1 is arranged on the lower side, sandwiching the first and second work spindle devices 3, 4, forming an upper and lower turret structure. Therefore, in the slant-type bed 50, two rail bases 53 of the upper turret device, two rail bases 54 of the work spindle device, and two rail bases 55 of the lower turret device are horizontally arranged in parallel on the front inclined surface (assembly section) 67 on which various devices are mounted, in order from above.

[0032] A coolant flow path 51 is formed in the bed 50, penetrating in the width direction of the machine body and parallel to the rail bases 53, 54, and 55. The coolant flow path 51 is also disposed so as to be located near the center with respect to the rails (rail bases 53, 54, and 55) related to various devices. That is, when the bed 50 shown in Fig. 6 is viewed from the side, the coolant flow path 51 is formed so that a center line 58 perpendicular to the front angle (45 degrees) of the bed 50, which indicates the center, passes between the two rail bases 54 located in the middle, so that the multiple rail bases 53, 54, and 55 are symmetrical.

[0033] The coolant flow passage 51 has a depth direction along the center line 58 and a width direction perpendicular to the depth direction (inclined direction). The bed 50 has a large area for the mounting portion 67, and the coolant flow passage 51 is formed with a large width dimension so as to efficiently absorb heat generated from devices corresponding to the rail bases 53, 55. On the other hand, the depth dimension along the center line 58 is limited by the hollow structure of the bed 50. Note that the shape of the coolant flow passage 51 is also affected by the rib structure of the bed 50, so the center line 58 does not indicate the exact center position.

[0034] Therefore, in this example as well, when the machine tool is in operation, coolant flows into the coolant passage 51 as the coolant device is driven, filling it. Therefore, heat generated from the servo motors and ball screws of the various processing devices is transmitted to the bed 50, but the heat is absorbed by the coolant flowing through the coolant passage 51. As a result, when the machine tool is in operation, the bed 50 suppresses local temperature increases, thereby reducing and equalizing the temperature difference in the assembly section 67. Even if thermal deformation occurs in the bed 50, the straightness of the spindle slide and turret Z-axis slide that move along the guide rails can be maintained.

[0035] Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and various modifications are possible without departing from the spirit of the present invention. For example, in the above embodiment, the slant-type bed 6 formed in a hollow shape has been shown and described, but the bed is not limited to such a shape or structure. [Explanation of symbols]

[0036] 1...machine tool 3...first work spindle device 4...second work spindle device 5...turret device 6...bed 18,23...guide rail 20,26...Z-axis servo motor 31...coolant flow path 35,36...rail base 41...side hole 42...dam 43...side gutter 65...assembly section

Claims

1. The bed has a plurality of processing devices each of which is independently movable along a plurality of parallel rails provided in an assembly portion of the bed, A coolant flow path for flowing coolant penetrates the bed in a direction parallel to the rails and is formed near the center of the multiple rails arranged in parallel.

2. 2. The machine tool according to claim 1, wherein the coolant passage is provided near a center of the plurality of parallel rails such that the rails are symmetrical with each other.

3. 3. The machine tool according to claim 1, wherein the bed is of a forwardly inclined slant type, and the plurality of rails are fixed horizontally to a front inclined portion of the bed and aligned vertically.

4. 4. The machine tool according to claim 3, wherein the bed has a hollow rib structure, and a side groove for receiving coolant leaking from holes formed in the coolant flow path is formed parallel to the coolant flow path.

Images