Grinding machine and grinding method using the same

Abstract

A grinding machine capable of improving grinding efficiency is provided. [Solution] The grinding machine 100 comprises a rotation support part 20 that can rotate a long rod-shaped workpiece W around an axis O while clamping it, a first grinding wheel 34 that can move in the axial direction (Z-axis direction) and X-axis direction of the workpiece W and grinds the outer peripheral surface of the workpiece W that it comes into contact with by rotating, and a second grinding wheel 34 that is provided on the opposite side of the first grinding wheel 34 across the workpiece W and can move in the Z-axis direction and X-axis direction and grinds the outer peripheral surface of the workpiece W that it comes into contact with by rotating. The grinding wheel 44 and the first grinding wheel 34 are spaced apart in the Z-axis direction, and are movable in the Z-axis and X-axis directions. The third grinding wheel 54 rotates to grind the outer surface of the workpiece W that it comes into contact with, and a control unit controls the first and second grinding wheels 34, 44 and the second and third grinding wheels 44, 54 to simultaneously grind the outer surface of the workpiece W, grinding the outer surface of the workpiece W at multiple locations to process it into circles with different cross-sectional shapes.

Description

[Technical Field]

[0001] The present invention relates to a grinding machine and a grinding method using the same. [Background technology]

[0002] To improve grinding efficiency, one long workpiece may be ground simultaneously with two rotating grinding wheels. For example, Patent Document 1 describes a double-head grinding machine in which a first grinding wheel (grinding wheel) and a second grinding wheel (grinding wheel) are rotatably arranged side by side and spaced apart in the axial direction of the workpiece for a crankshaft, and the two grinding wheels simultaneously come into contact with and grind the outer peripheral surface of the workpiece at two locations.

[0003] Patent document 2 also describes a grinding machine in which a primary grinding wheel and a secondary grinding wheel are rotatably arranged to sandwich a grinding object (workpiece) made of a small-diameter, long material, and rough grinding with the primary grinding wheel and finish grinding with the secondary grinding wheel are simultaneously performed on the outer peripheral surface of the same location of the grinding object. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-136379 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-000848 Summary of the Invention [Problem to be solved by the invention]

[0005] However, even with the grinding machines described in Patent Documents 1 and 2, the grinding efficiency cannot be said to be sufficiently high.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a grinding machine capable of improving grinding efficiency and a grinding method using the same. [Means for solving the problem]

[0007] The grinding machine of the present invention includes a rotation support unit that can rotate a long rod-shaped workpiece around an axis while clamping it in the longitudinal direction, a first grinding wheel that is movable in the axial direction of the workpiece and in a direction perpendicular to that direction and rotates to grind the outer peripheral surface of the workpiece that comes into contact with it, a second grinding wheel that is provided on the opposite side of the first grinding wheel across the workpiece and is movable in the axial direction of the workpiece and in a direction perpendicular to that direction and rotates to grind the outer peripheral surface of the workpiece that comes into contact with it, and The method is characterized in that it comprises a third grinding wheel that is spaced apart from the first grinding wheel in the axial direction of the workpiece, is movable in the axial direction of the workpiece and in a direction perpendicular to that direction, and rotates to grind the outer peripheral surface of the workpiece that it comes into contact with, and a control unit that controls the first grinding wheel and the second grinding wheel, and the second grinding wheel and the third grinding wheel so that they simultaneously grind the outer peripheral surface of the workpiece, and grinds the outer peripheral surface of the workpiece at multiple locations to process it into circles with different cross-sectional shapes.

[0008] According to the grinding machine of the present invention, the outer peripheral surface of the workpiece can be simultaneously ground with the first and second grinding wheels, and the outer peripheral surface of the workpiece can be simultaneously ground with the second and third grinding wheels, which makes it possible to improve grinding efficiency compared to the grinding machines described in the above-mentioned Patent Documents 1 and 2.

[0009] In the grinding machine of the present invention, it is preferable that the range of the outer peripheral surface of the workpiece that can be ground by the first grinding wheel and the third grinding wheel, or the range of the outer peripheral surface of the workpiece that can be ground by the second grinding wheel and the third grinding wheel, overlaps.

[0010] In this case, the overlapping grindable areas of the outer peripheral surface of the workpiece can be simultaneously ground with two grinding wheels, which allows the grinding load to be supported by both wheels, resulting in excellent grinding accuracy.

[0011] In the grinding machine of the present invention, it is preferable that the rotation support part is movable in the up and down direction while clamping the workpiece.

[0012] In this case, it is possible to position the workpiece at a position where good grinding can be performed by the first to third grinding wheels.

[0013] In the grinding machine of the present invention, it is preferable that the directions in which the first grinding wheel, the second grinding wheel and the third grinding wheel can move, which are perpendicular to the axial direction of the workpiece, are the same direction.

[0014] In this case, when the first and second grinding wheels, or the second and third grinding wheels, simultaneously grind the workpiece, the grinding load acts from opposite directions, making it possible to obtain good grinding accuracy.

[0015] In addition, in the grinding machine of the present invention, it is preferable that the control unit controls the first grinding wheel, the second grinding wheel, and the third grinding wheel so that they simultaneously grind the outer peripheral surface of the workpiece.

[0016] In this case, it is possible to further improve the grinding efficiency.

[0017] In addition, in the grinding machine of the present invention, it is preferable that the control unit is capable of controlling at least one of the first grinding wheel, the second grinding wheel, and the third grinding wheel to move simultaneously in the axial direction of the workpiece and in a direction perpendicular to that direction.

[0018] In this case, the grinding wheel can be rotated to make oblique cuts into the workpiece, making it possible to perform end face machining on the corners of the workpiece.

[0019] The grinding method of the present invention includes a rotary support unit capable of rotating a long rod-shaped workpiece around an axis while clamping the workpiece in the longitudinal direction, a first grinding wheel movable in the axial direction of the workpiece and in a direction perpendicular to the axial direction, and rotating to grind the outer peripheral surface of the workpiece that comes into contact with the workpiece, and a second grinding wheel disposed on the opposite side of the first grinding wheel across the workpiece, movable in the axial direction of the workpiece and in a direction perpendicular to the axial direction, and rotating to grind the outer peripheral surface of the workpiece that comes into contact with the workpiece. and a third grinding wheel that is spaced apart from the first grinding wheel in the axial direction of the workpiece, is movable in the axial direction of the workpiece and in a direction perpendicular to that direction, and rotates to grind the outer peripheral surface of the workpiece that it comes into contact with, and the second grinding wheel and the second grinding wheel, and the first grinding wheel and the third grinding wheel simultaneously grind the outer peripheral surface of the workpiece, thereby processing the outer peripheral surface of the workpiece at multiple locations into circles with different cross-sectional shapes.

[0020] According to the grinding method of the present invention, it is possible to obtain the same effects as those of the grinding machine of the present invention described above. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a schematic top view showing a grinding machine according to an embodiment of the present invention; [Figure 2] 1 is a conceptual diagram illustrating simultaneous grinding by a first grinding wheel and a second grinding wheel of a grinding machine in a grinding method according to a first embodiment of the present invention. [Figure 3] FIG. 3 is a conceptual diagram illustrating simultaneous grinding by the second and third grinding wheels in the grinding method according to the first embodiment of the present invention. [Figure 4] FIG. 10 is a conceptual diagram illustrating simultaneous grinding by first to third grinding wheels in a grinding method according to a second embodiment of the present invention. [Figure 5] FIG. 10 is a conceptual diagram illustrating simultaneous grinding by first to third grinding wheels in a grinding method according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] A grinding machine 100 according to an embodiment of the present invention will be described with reference to Fig. 1. The grinding machine 100 grinds the outer peripheral surface of a workpiece W having a long rod shape.

[0023] The workpiece W is made of a hard material such as steel or a non-ferrous alloy, and is, for example, a solid, roughly round bar-shaped forging. The outer periphery of the workpiece W is then ground to obtain a finished product with circular cross sections. The finished product has a round bar-shaped portion with the same circular cross section, an intermediate portion W2 having an expanded-diameter flange portion Wa at one end thereof, a multi-step first stepped portion W1 whose diameter decreases continuously from the side opposite the flange portion Wa of the intermediate portion W2 toward its tip, and a multi-step second stepped portion W3 whose diameter decreases stepwise continuously from the side where the flange portion Wa of the intermediate portion W2 is provided toward its other tip.

[0024] The grinding machine 100 has a base 10, on which a rotation support part 20, a first grinding device 30, a second grinding device 40, and a third grinding device 50 are mainly arranged.

[0025] A vertical slide base 11 is fixed to the upper surface of the base 10, and a rotation support part 20 is disposed on this vertical slide base 11. This allows the rotation support part 20 to move in the Y-axis direction (up and down direction) relative to the base 10.

[0026] The rotation support unit 20 has a pair of headstocks 21A, 21B spaced apart in the Z-axis direction (the horizontal direction, which is the axial direction of the workpiece W) on the upper surface of the vertical slide base 11 and configured to be movable in the Z-axis direction via guide rails (not shown). Spindles 22A, 22B are rotatably supported on the headstocks 21A, 21B, respectively. These spindles 22A, 22B are configured to be rotated by rotary motors 23A, 23B, respectively.

[0027] Chucks 24A, 24B are fixed to the opposing ends of the spindles 22A, 22B, respectively. These chucks 24A, 24B support both ends of the workpiece W, thereby clamping the workpiece W. The workpiece W thus clamped between the chucks 24A, 24B rotates about its axis O as the spindles 22A, 22B rotate.

[0028] Furthermore, dressers 25A and 25B are fixed to the spindles 22A and 22B, respectively. As a result, when the rotation support part 20 is not clamping the workpiece W, by rotating the spindles 22A and 22B, the dressers 25A and 25B that rotate in association with the rotation can dress the grinding wheels 34, 44, and 54, which will be described later.

[0029] Additionally, three movable tables 12, 13, and 14 are fixed to the upper surface of the base 10, and wheel heads 31, 41, and 51 of the grinding devices 30, 40, and 50 are respectively disposed on these movable tables 12, 13, and 14. This allows each of the grinding devices 30, 40, and 50 to move independently in the Z-axis direction and the X-axis direction (horizontal front-rear direction that is perpendicular to both the Y-axis direction and the Z-axis direction) relative to the base 10. Although not shown, the movable tables 12, 13, and 14 may be configured using, for example, guide rails and feed screws, and are equipped with electric motors, not shown, for moving the wheel heads 31, 41, and 51.

[0030] In each grinding machine 30, 40, 50, a processing head 32, 42, 52 is disposed on a wheel head 31, 41, 51. A rotary shaft 33, 43, 53 is rotatably supported on each processing head 32, 42, 52, and a short cylindrical grinding wheel 34, 44, 54 is attached to the tip of each rotary shaft 33, 43, 53, respectively.

[0031] Furthermore, rotary motors 35, 45, 55 are arranged on each grinding wheel head 31, 41, 51 as drive units, and when these rotary motors 35, 45, 55 rotate, each grinding wheel 34, 44, 54 rotates via pulleys and belts (both not shown).

[0032] 2, the first grinding device 30 is disposed so that its first grinding wheel 34 can grind the entire outer peripheral surface of the first step portion W1 of the workpiece W. Specifically, the position and movement distance L1 of the first moving table 12 on which the first grinding device 30 is disposed are determined so that the first grinding wheel 34 can come into contact with the outer peripheral surface of the workpiece W over the entire range of the first step portion W1. It is preferable that the rotation direction of the first grinding wheel 34 is the same as the rotation direction of the workpiece W.

[0033] 2 and 3, the second grinding device 40 is disposed on the opposite side of the first grinding device 30 across the workpiece W so that its second grinding wheel 44 can grind the entire outer peripheral surface of the first step portion W1 and the middle portion W2 of the workpiece W. Specifically, the position and movement distance (L1+L2) of the second moving table 13 on which the second grinding device 40 is disposed are determined so that the second grinding wheel 44 can come into contact with the outer peripheral surface of the workpiece W over the entire range of the first step portion W1 and the middle portion W2. Note that the rotation direction of the second grinding wheel 44 is preferably opposite to the rotation direction of the workpiece W.

[0034] 3, the third grinding device 50 is disposed at a distance in the Z-axis direction from the first grinding device 30 so that its third grinding wheel 54 can grind the entire outer peripheral surface of the second stepped portion W3 of the workpiece W. Specifically, the position and movement distance L3 of the third moving table 14 on which the third grinding device 50 is disposed are determined so that the third grinding wheel 54 can come into contact with the outer peripheral surface of the workpiece W over the entire second stepped portion W3. It is preferable that the rotation direction of the third grinding wheel 54 be the same as the rotation direction of the workpiece W.

[0035] Furthermore, although not shown, the grinding machine 100 is equipped with a control unit (not shown) that controls the movement of the vertical slide table 11 in the Y-axis direction, the movement of the moving tables 12, 13, and 14 in the Z-axis direction and X-axis direction, the rotation of the rotary motors 23A and 23B of the rotary support unit 20, and the rotation of the rotary motors 35, 45, and 55 of each grinding device 30, 40, and 50.

[0036] The control unit is configured with an arithmetic processing unit (e.g., a CPU, a processor, a processor core) and a storage device (e.g., a memory such as a ROM or RAM). The control unit is configured to execute tasks by reading necessary data and programs (software) from the storage device and executing arithmetic processing according to the programs on or based on the data.

[0037] Hereinafter, a grinding method according to a first embodiment of the present invention using the grinding machine 100 described above will be described.

[0038] First, the workpiece W is clamped using the chucks 24A and 24B. Then, in this clamped state, the control unit described above rotates the rotation motors 23A and 23B of the rotation support unit 20. As a result, the workpiece W continues to rotate thereafter.

[0039] On the other hand, as shown in FIG. 2, the control unit controls the Z-axis position of the first grinding wheel 34, and therefore the Z-axis position of the first moving table 12, as well as the feed speed of the first grinding wheel 34 and therefore the movement speed of the first moving table 12 in the X-axis direction, using the above-mentioned electric motor provided on the first moving table 12 so that the first grinding wheel 34 contacts the outer peripheral surface of the end of the first stepped portion W1 of the workpiece W.

[0040] In addition, the control unit controls the Z-axis position of the second grinding wheel 44, and therefore the Z-axis position of the second moving table 13, as well as the feed speed of the second grinding wheel 44 and therefore the movement speed of the second moving table 13 in the X-axis direction, using the above-mentioned electric motor provided on the second moving table 13, so that the second grinding wheel 44 contacts the outer peripheral surface of the end of the first stepped portion W1 of the workpiece W.

[0041] Then, while maintaining the above-described states of the first and second grinding wheels 34, 44, the control unit controls the rotational speed of the first grinding wheel 34, and therefore the rotational speed of the rotary motor 35 of the first grinding device 30, and the rotational speed of the second grinding wheel 44, and therefore the rotational speed of the rotary motor 45 of the second grinding device 40. As a result, the first and second grinding wheels 34, 44 simultaneously start grinding the outer peripheral surface of the first stepped portion W1.

[0042] The control unit controls the feed speeds of the first and second grinding wheels 34, 44 in this grinding state according to the cross-sectional shape of the first step portion W1, while also controlling the movement amounts in the Z-axis direction of the first and second grinding wheels 34, 44. This allows the first and second grinding wheels 34, 44 to simultaneously grind the outer circumferential surface of the first step portion W1.

[0043] At this time, the movement distance in the Z-axis direction of the first and second grinding wheels 34, 44 is L1. In this way, the first step portion W1 is ground by the first and second grinding wheels 34, 44 from opposite directions, and therefore the grinding load can be supported by each other, making it possible to obtain good grinding accuracy.

[0044] At this time, it is preferable that the first grinding wheel 34 and the second grinding wheel 44 are positioned at the same position in the Z-axis direction with the workpiece W sandwiched therebetween, but this is not limited to this. It is also preferable that the grinding processes by the first and second grinding wheels 34, 44 start and end at the same time, but this is not limited to this. For example, one may start grinding first, and then the other may finish grinding first.

[0045] The feed rate and rotation rate of the first and second grinding wheels 34, 44 may be the same or different. For example, if the feed rate is reduced and the rotation rate is increased, the resulting ground surface will have less roughness. Therefore, the feed rate of the first grinding wheel 34 may be reduced and the rotation rate may be increased to perform finish grinding, and the feed rate of the second grinding wheel 44 may be increased and the rotation rate may be decreased to perform rough grinding.

[0046] When the grinding of the first stepped portion W1 is completed, the control unit moves the first moving table 12 so that the first grinding wheel 34 does not come into contact with the outer peripheral surface of the workpiece W.

[0047] Next, the control unit controls the Z-axis position of the second grinding wheel 44, and therefore the Z-axis position of the second moving table 13, as well as the feed speed of the second grinding wheel 44, and therefore the movement speed of the second moving table 13 in the X-axis direction, using the above-mentioned electric motor provided on the second moving table 13, so that the second grinding wheel 44 contacts the outer peripheral surface of the end of the middle portion W2 of the workpiece W.

[0048] In addition, the control unit controls the Z-axis position of the third grinding wheel 54, and therefore the Z-axis position of the third moving table 14, as well as the feed speed of the third grinding wheel 54 and therefore the movement speed of the third moving table 14 in the X-axis direction, using the above-mentioned electric motor provided on the third moving table 14 so that the third grinding wheel 54 contacts the outer peripheral surface of the end of the second stepped portion W3 of the workpiece W.

[0049] Then, while maintaining the above-described states of the second and third grinding wheels 44, 54, the control unit controls the rotational speed of the second grinding wheel 44, and therefore the rotational speed of the rotary motor 45 of the second grinding device 40, and the rotational speed of the third grinding wheel 54, and therefore the rotational speed of the rotary motor 55 of the third grinding device 50. As a result, grinding of the outer peripheral surface of the intermediate portion W2 by the second grinding wheel 44 and grinding of the outer peripheral surface of the second stepped portion W3 by the third grinding wheel 54 are started simultaneously.

[0050] The control unit controls the feed speed of the second and third grinding wheels 44, 54 in this grinding state according to the cross-sectional shapes of the intermediate portion W2 and the second stepped portion W3, while also controlling the movement amount in the Z-axis direction of the second and third grinding wheels 44, 54. As a result, the grinding process on the outer peripheral surface of the intermediate portion W2 by the second grinding wheel 44 and the grinding process on the outer peripheral surface of the second stepped portion W3 by the third grinding wheel 54 proceed simultaneously.

[0051] At this time, the movement distance of the second grinding wheel 44 in the Z-axis direction is L2, and the movement distance of the third grinding wheel 54 in the Z-axis direction is L3. In this way, the workpiece W is ground by the second and third grinding wheels 44, 54 from opposite directions, and therefore the grinding load can be supported by each other, making it possible to obtain good grinding accuracy.

[0052] At this time, it is preferable that the grinding processes by the second and third grinding wheels 44, 54 start and end simultaneously, but this is not limitative. For example, one may start grinding first, and then either one may finish grinding first.

[0053] Furthermore, the feed rate, rotation rate, and movement rate in the Z-axis direction of the second and third grinding wheels 44, 54 may be the same or different. For example, if the feed rate is reduced and the rotation rate is increased, the resulting ground surface will have less roughness. Therefore, the feed rate of the second grinding wheel 44 may be increased, its rotation rate may be decreased, and its movement rate in the Z-axis direction may be increased to perform rough grinding, and the feed rate of the third grinding wheel 54 may be decreased, its rotation rate may be increased, and its movement rate in the Z-axis direction may be decreased to perform finish grinding.

[0054] As described above, according to the first embodiment of the present invention, the first step portion W1 can be simultaneously ground by the first and second grinding wheels 34, 44, and the intermediate portion W2 can be simultaneously ground by the second grinding wheel 44 and the second step portion W2 can be simultaneously ground by the third grinding wheel 54. This makes it possible to improve grinding efficiency compared to the grinding machines described in Patent Documents 1 and 2 mentioned above.

[0055] A grinding method according to a second embodiment of the present invention using the grinding machine 100 described above will be described below.

[0056] First, similarly to the first embodiment described above, the workpiece W is rotated while being clamped between the chucks 24A and 24B.

[0057] On the other hand, as shown in Figure 4, the control unit controls the first grinding wheel 34 to contact the outer peripheral surface of the end of the first step portion W1 of the workpiece W, the second grinding wheel 44 to contact the outer peripheral surface of the end of the intermediate portion W2, and the third grinding wheel 54 to contact the outer peripheral surface of the end of the second step portion W2 of the workpiece W.

[0058] Then, while maintaining the above states of the first to third grinding wheels 34, 44, 54, the control unit controls the rotational speeds of the first to third grinding wheels 34, 44, 54. As a result, grinding of the outer peripheral surface of the first stepped portion W1 by the first grinding wheel 34, grinding of the outer peripheral surface of the middle portion W2 by the second grinding wheel 54, and grinding of the outer peripheral surface of the second stepped portion W3 by the third grinding wheel 54 are started simultaneously.

[0059] The control unit controls the feed rate of the first grinding wheel 34 in accordance with the cross-sectional shape of the first step portion W1, while also controlling the amount of movement of the first grinding wheel 34 in the Z-axis direction, depending on the cross-sectional shape of the intermediate portion W2. The control unit controls the feed rate of the second grinding wheel 44 in accordance with the cross-sectional shape of the intermediate portion W2, while also controlling the amount of movement of the second grinding wheel 44 in the Z-axis direction, depending on the cross-sectional shape of the second step portion W3. The control unit controls the feed rate of the third grinding wheel 54 in accordance with the cross-sectional shape of the second step portion W3, while also controlling the amount of movement of the third grinding wheel 54 in the Z-axis direction, depending on the cross-sectional shape of the second step portion W3. As a result, grinding of the outer peripheral surface of the first step portion W1 by the first grinding wheel 34, grinding of the outer peripheral surface of the intermediate portion W2 by the second grinding wheel 44, and grinding of the outer peripheral surface of the second step portion W3 by the third grinding wheel 54 proceed simultaneously.

[0060] When the grinding of the first step portion W1 by the first grinding wheel 34 is completed, the first grinding wheel 34 is removed from the outer peripheral surface of the workpiece W. When the grinding of the intermediate portion W2 by the second grinding wheel 44 is completed, the fourth grinding wheel 44 is removed from the outer peripheral surface of the workpiece W. Furthermore, when the grinding of the second step portion W3 by the third grinding wheel 54 is completed, the third grinding wheel 54 is removed from the outer peripheral surface of the workpiece W.

[0061] In this way, the movement distance of the first grinding wheel 34 in the Z-axis direction is L1, the movement distance of the second grinding wheel 44 in the Z-axis direction is L2, and the movement distance of the third grinding wheel 54 in the Z-axis direction is L3.

[0062] As described above, according to the second embodiment of the present invention, the workpiece W can be ground simultaneously using the first to third grinding wheels 34, 44, 54. This makes it possible to improve grinding efficiency compared to the grinding machines described in the above-mentioned Patent Documents 1 and 2. Furthermore, when the first and third grinding wheels 34, 54 and the second grinding wheel 44 simultaneously grind the workpiece W, grinding loads act from opposite directions, making it possible to obtain good grinding accuracy.

[0063] Hereinafter, a grinding method according to a third embodiment of the present invention using the grinding machine 100 described above will be described.

[0064] First, similarly to the first embodiment described above, the workpiece W is rotated while being clamped between the chucks 24A and 24B.

[0065] On the other hand, as shown in Figure 5, the control unit controls the first grinding wheel 34 to contact the outer peripheral surface of the end of the first step portion W1 of the workpiece W, the second grinding wheel 44 to contact the outer peripheral surface of the end of the first step portion W1 of the workpiece W, and the third grinding wheel 54 to contact the outer peripheral surface of the end of the second step portion W2 of the workpiece W.

[0066] Then, while maintaining the above states of the first to third grinding wheels 34, 44, 54, the control unit controls the rotational speeds of the first to third grinding wheels 34, 44, 54. As a result, grinding of the outer peripheral surface of the first stepped portion W1 by the first and second grinding wheels 34, 44, and grinding of the outer peripheral surface of the second stepped portion W3 by the third grinding wheel 54 are started simultaneously.

[0067] The control unit controls the feed speeds of the first and second grinding wheels 34, 44 in this grinding state in accordance with the cross-sectional shape of the first step portion W1, while also controlling the amount of movement of the first and second grinding wheels 34, 44 in the Z-axis direction. The control unit also controls the feed speed of the third grinding wheel 54 in accordance with the cross-sectional shape of the second step portion W3, while also controlling the amount of movement of the third grinding wheel 54 in the Z-axis direction. This allows the first and second grinding wheels 34, 44 to grind the outer peripheral surface of the first step portion W1, and the third grinding wheel 54 to grind the outer peripheral surface of the second step portion W3, to proceed simultaneously.

[0068] Then, after grinding of the outer peripheral surface of the first step portion W1 by the second grinding wheel 44 is completed, the control unit controls the second grinding wheel 44 to come into contact with the outer peripheral surface of the end of the first step portion W1 of the workpiece W. Thereafter, the control unit controls the amount of movement of the second grinding wheel 44 in the Z-axis direction while controlling the feed speed of the second grinding wheel 44 according to the cross-sectional shape of the intermediate portion W2.

[0069] When the grinding of the first step portion W1 by the first grinding wheel 34 is completed, the first grinding wheel 34 is removed from the outer peripheral surface of the workpiece W. When the grinding of the middle portion W2 by the second grinding wheel 34 is completed, the second grinding wheel 44 is removed from the outer peripheral surface of the workpiece W. Furthermore, when the grinding of the second step portion W3 by the third grinding wheel 54 is completed, the third grinding wheel 54 is removed from the outer peripheral surface of the workpiece W.

[0070] In this way, the movement distance of the first grinding wheel 34 in the Z-axis direction is L1, the movement distance of the third grinding wheel 54 in the Z-axis direction is L3, and the movement distance of the second grinding wheel 44 in the Z-axis direction is (L1 + L2).

[0071] As described above, according to the second embodiment of the present invention, the workpiece W can be ground simultaneously using the first to third grinding wheels 34, 44, 54. This makes it possible to improve grinding efficiency compared to the grinding machines described in the above-mentioned Patent Documents 1 and 2. Furthermore, when the first and third grinding wheels 34, 54 and the second grinding wheel 44 simultaneously grind the workpiece W, grinding loads act from opposite directions, making it possible to obtain good grinding accuracy.

[0072] The present invention is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the claims. For example, in the first embodiment, the first step portion W1 is simultaneously ground by the first and second grinding devices 30, 40, and then the intermediate portion W2 and the second step portion W3 are simultaneously ground by the second and third grinding devices 40, 50. However, the grinding order is not limited to this, and may be reversed.

[0073] In addition, although the first to third grinding wheels 34, 44, 54 are all movable in the X-axis direction in the above description, the present invention is not limited to this. The movement directions of the first to third grinding wheels 34, 44, 54 may be perpendicular to the Z-axis direction, and the directions in which each grinding wheel can move may be different.

[0074] Although the first to third grinding wheels 34, 44, 54 are controlled to move independently in the X-axis direction and the Z-axis direction in the above description, the present invention is not limited to this. For example, at least one of the first to third grinding wheels 34, 44, 54 may be controlled to move simultaneously in the X-axis direction and the Z-axis direction.

[0075] For example, although not shown, a two-axis NC control may be performed simultaneously on a servo motor provided on the first moving table 12 for movement in the X-axis direction and a servo motor for movement in the Z-axis direction to perform interpolation to move linearly or circularly within the X-axis-Y-axis plane for grinding. This allows the first grinding wheel 34 to rotate and make oblique cuts into the workpiece W, thereby enabling edge processing of corners of the workpiece W. Such interpolation may be performed simultaneously with the grinding of the workpiece W by the other grinding wheels 44, 54, or may be performed independently. The grinding of the other grinding wheels 44, 54 may or may not be an interpolation operation.

[0076] Furthermore, the shape of the workpiece W described above is an example, and the positions at which the grinding devices 30, 40, 50 are disposed and the distances they move in the Z-axis direction may be determined appropriately in accordance with the shape of the workpiece W.

[0077] Furthermore, the grinding machine 100 has been described as having three grinding devices 30, 40, and 50, but it may also be further provided with grinding devices spaced apart in the Z-axis direction from the first and third grinding devices 30 and 50, or may also be further provided with a grinding device spaced apart in the Z-axis direction from the second grinding device 40. [Explanation of symbols]

[0078] DESCRIPTION OF SYMBOLS 10...base, 11...up-and-down slide table, 12...first moving table, 13...second moving table, 14...third moving table, 20...rotation support portion, 21A, 21B...headstock, 22A, 22B...spindle, 23A, 23B...rotation motor, 24A, 24B...chuck, 25A, 25B...dresser, 30...first grinding device, 31...first grinding wheel head, 32...first machining head, 33...first rotating shaft, 34...first grinding wheel, 35...first rotating motor, 40...second grinding device, 41...second grinding wheel head, 42...second machining head, 53...second rotating shaft, 44...second grinding wheel, 45...second rotating motor, 50...Third grinding device, 51...Third grinding wheel head, 52...Third processing head, 53...Third rotating shaft, 54...Third grinding wheel, 55...Third rotating motor, 100...Grinding machine, O...Axis center, W...Workpiece, W1...First stepped portion, W2...Intermediate portion, W3...Second stepped portion, Wa...Flange portion.

Claims

1. a rotation support unit that can rotate a long rod-shaped workpiece around an axis while clamping the workpiece in the longitudinal direction; a first grinding wheel that is movable in the axial direction of the workpiece and in a direction perpendicular to the axial direction, and that rotates while coming into contact with the outer peripheral surface of the workpiece rotated by the rotation support part to grind the outer peripheral surface of the workpiece; a second grinding wheel that is provided on the opposite side of the first grinding wheel with the workpiece interposed therebetween, that is movable in the axial direction of the workpiece and in a direction perpendicular to said axial direction, and that comes into contact with the outer peripheral surface of the workpiece that is rotated by the rotation support while rotating, thereby grinding the outer peripheral surface of the workpiece; a third grinding wheel that is provided at an interval from the first grinding wheel in the axial direction of the workpiece, that is movable in the axial direction of the workpiece and in a direction perpendicular to the axial direction, and that comes into contact with the outer peripheral surface of the workpiece that is rotated by the rotation support while rotating, thereby grinding the outer peripheral surface of the workpiece; a control unit that controls the first grinding wheel and the second grinding wheel, and the second grinding wheel and the third grinding wheel so that they simultaneously grind the outer peripheral surface of the workpiece, A grinding machine characterized by grinding the outer peripheral surface of the workpiece at multiple locations to process it into circles with different cross-sectional shapes.

2. 2. The grinding machine according to claim 1, wherein the range of the outer peripheral surface of the workpiece that can be ground by the first grinding wheel and the third grinding wheel, or the range of the outer peripheral surface of the workpiece that can be ground by the second grinding wheel and the third grinding wheel, overlaps.

3. 2. The grinding machine according to claim 1, wherein the rotation support part is movable in the vertical direction while clamping the workpiece.

4. 2. The grinding machine according to claim 1, wherein the first grinding wheel, the second grinding wheel, and the third grinding wheel are movable in the same direction perpendicular to the axial direction of the workpiece.

5. 2. The grinding machine according to claim 1, wherein the control unit controls the first grinding wheel, the second grinding wheel, and the third grinding wheel so that they simultaneously grind the outer peripheral surface of the workpiece.

6. 2. The grinding machine according to claim 1, wherein the control unit is capable of controlling at least one of the first grinding wheel, the second grinding wheel, and the third grinding wheel to simultaneously move in the axial direction of the workpiece and in a direction perpendicular to that direction.

7. A grinding machine as described in Claim 1, characterized in that the control unit is capable of controlling the first grinding wheel and the third grinding wheel to move independently.

8. a rotation support unit that can rotate a long rod-shaped workpiece around an axis while clamping the workpiece in the longitudinal direction; a first grinding wheel that is movable in the axial direction of the workpiece and in a direction perpendicular to the axial direction, and that rotates while coming into contact with the outer peripheral surface of the workpiece rotated by the rotation support part to grind the outer peripheral surface of the workpiece; a second grinding wheel that is provided on the opposite side of the first grinding wheel with the workpiece interposed therebetween, that is movable in the axial direction of the workpiece and in a direction perpendicular to said axial direction, and that comes into contact with the outer peripheral surface of the workpiece that is rotated by the rotation support while rotating, thereby grinding the outer peripheral surface of the workpiece; a third grinding wheel that is provided at an interval from the first grinding wheel in the axial direction of the workpiece, that is movable in the axial direction of the workpiece and in a direction perpendicular to the axial direction, and that comes into contact with the outer peripheral surface of the workpiece rotated by the rotation support while rotating to grind the outer peripheral surface of the workpiece, A grinding method characterized in that the first grinding wheel and the second grinding wheel, and the second grinding wheel and the third grinding wheel simultaneously grind the outer surface of the workpiece, thereby processing the outer surface of the workpiece at multiple locations into circles with different cross-sectional shapes.

9. A grinding method as described in Claim 8, characterized in that the first grinding wheel and the third grinding wheel can be controlled to move independently.

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