Grinder and grinding method using the same

Abstract

This grinder 100 is equipped with: a rotation support part 20 capable of rotating a long, rod-like workpiece W around an axis O while holding said workpiece W; a first grinding wheel 34 which is capable of moving in the axial direction (Z-axis direction) of the workpiece W and in the X-axis direction, and grinds an outer-peripheral surface of the rotating, contacted workpiece W; a second grinding wheel 44 which is provided on the opposite side relative to the first grinding wheel 34 with the workpiece W interposed therebetween, is capable of moving in the Z-axis direction and the X-axis direction, and grinds an outer-peripheral surface of the rotating, contacted workpiece W; a third grinding wheel 54 which is provided at an interval from the first grinding wheel 34 in the Z-axis direction, is capable of moving in the Z-axis direction and the X-axis direction, and grinds the outer-peripheral surface of the rotating, contacted workpiece W; and a control unit that controls in a manner such that the first and second grinding wheels 34, 44 and the second and third grinding wheels 44, 54 simultaneously grind the outer-peripheral surface of the workpiece W. Therein, the outer-peripheral surface of the workpiece W is ground at a plurality of locations, and the workpiece W is machined into a circular shape having different cross-sectional shapes.

Description

Grinding machine and grinding method using the same

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

[0002] In order to improve the grinding efficiency, a long workpiece may be simultaneously ground by two rotating grinding wheels. For example, in Patent Document 1, a first grinding wheel (grinding wheel) and a second grinding wheel (grinding wheel) are arranged side by side rotatably at a distance in the axial direction of the workpiece for a workpiece serving as a crankshaft, and a double-end grinding machine in which the two grinding wheels simultaneously contact and grind the outer peripheral surfaces of two locations of the workpiece is described.

[0003] Further, in Patent Document 2, a primary grinding wheel and a secondary grinding wheel are provided rotatably with a grinding object (workpiece) made of a small-diameter long material sandwiched therebetween, and a grinding machine that simultaneously performs rough grinding by the primary grinding wheel and finish grinding by the secondary grinding wheel on the outer peripheral surface of the same location of the grinding object is described.

[0004] Japanese Patent Application Laid-Open No. 2003-136379, Japanese Patent Application Laid-Open No. 2013-000848

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

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

[0007] The grinding machine of the present invention includes a rotating support unit capable of rotating a long, rod-shaped workpiece around its 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 grinds the outer circumferential surface of the workpiece that it rotates and makes contact with, and a second grinding wheel provided on the opposite side of the workpiece from the first grinding wheel, with the workpiece in between, and that is movable in the axial direction of the workpiece and in a direction perpendicular to that direction, and grinds the outer circumferential surface of the workpiece that it rotates and makes contact with, and the The first grinding wheel is provided at intervals 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 circumferential surface of the workpiece it contacts, and comprises a control unit that controls the first grinding wheel, the second grinding wheel, and the second grinding wheel and the third grinding wheel to grind the outer circumferential surface of the workpiece simultaneously, characterized in that the outer circumferential surface of the workpiece at multiple locations is ground to process it into a circular shape with different cross-sectional shapes.

[0008] According to the grinding machine of the present invention, it is possible to simultaneously grind the outer surface of a workpiece using the first and second grinding wheels, and also to simultaneously grind the outer surface of a workpiece using the second and third grinding wheels. As a result, it is 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 surface of the workpiece that can be ground by the first grinding wheel and the third grinding wheel, or the range of the outer surface of the workpiece that can be ground by the second grinding wheel and the third grinding wheel, overlap.

[0010] In this case, it becomes possible to simultaneously grind the outer surface of the workpiece, where the grindable areas overlap, using two grinding wheels. This allows the grinding loads to be mutually supported, resulting in good grinding accuracy.

[0011] Furthermore, in the grinding machine of the present invention, it is preferable that the rotating support portion is movable in the vertical direction while holding the workpiece.

[0012] In this case, the workpiece can be positioned in a location where good grinding can be performed by the first to third grinding wheels.

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

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

[0015] Furthermore, 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 to grind the outer surface of the workpiece simultaneously.

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

[0017] Furthermore, 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 to the workpiece, making it possible to perform end-face machining on the corners of the workpiece.

[0019] The grinding method of the present invention comprises: a rotating support unit capable of rotating a long, rod-shaped workpiece around its 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 grinds the outer circumferential surface of the workpiece that it rotates and makes contact with; and a second grinding wheel provided on the opposite side of the workpiece from the first grinding wheel, separated by the workpiece, and movable in the axial direction of the workpiece and in a direction perpendicular to that direction, and grinds the outer circumferential surface of the workpiece that it rotates and makes contact with. The invention is characterized by using a grinding machine that includes a third grinding wheel, which 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 circumferential surface of the workpiece in contact with it, and in which the first grinding wheel and the second grinding wheel, and the first grinding wheel and the third grinding wheel simultaneously grind the outer circumferential surface of the workpiece, thereby processing the outer circumferential surface of the workpiece at multiple locations so that the cross-sectional shapes of the outer circumferential surface of the workpiece are circular.

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

[0021] A schematic top view showing a grinding machine according to an embodiment of the present invention. A conceptual diagram illustrating simultaneous grinding by first and second grinding wheels in a grinding method according to the first embodiment of the present invention. A conceptual diagram illustrating simultaneous grinding by second and third grinding wheels in a grinding method according to the first embodiment of the present invention. A conceptual diagram illustrating simultaneous grinding by first to third grinding wheels in a grinding method according to the second embodiment of the present invention. A conceptual diagram illustrating simultaneous grinding by first to third grinding wheels in a grinding method according to the third embodiment of the present invention.

[0022] A grinding machine 100 according to an embodiment of the present invention will be described with reference to Figure 1. The grinding machine 100 grinds the outer surface of a long, rod-shaped workpiece W.

[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 forged product. By grinding the outer surface of this workpiece W, a finished product with circular cross-sections is obtained. This finished product has a round bar-shaped portion with the same circular cross-section, an intermediate portion W2 having an enlarged flange portion Wa at one end, a multi-step first stepped portion W1 that extends from the side of the intermediate portion W2 opposite to the side with the flange portion Wa and decreases in diameter towards the tip, and a multi-step second stepped portion W3 that extends from the side of the intermediate portion W2 with the flange portion Wa and decreases in diameter in a stepwise manner towards the other tip.

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

[0025] An upper and lower sliding base 11 is fixed to the upper surface of the base 10, and a rotating support unit 20 is provided on this upper and lower sliding base 11. As a result, the rotating support unit 20 is movable in the Y-axis direction (vertical direction) relative to the base 10.

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

[0027] Chucks 24A and 24B are fixed to the opposing ends of each spindle 22A and 22B, respectively. These chucks 24A and 24B clamp the workpiece W by supporting both ends of the workpiece W. The workpiece W, clamped in this way by the chucks 24A and 24B, rotates around its axis O as the spindles 22A and 22B rotate.

[0028] Furthermore, dressers 25A and 25B are also fixed to each of the main spindles 22A and 22B, respectively. As a result, when the rotating support unit 20 is not holding a workpiece W, the rotating main spindles 22A and 22B can be rotated, and the dressers 25A and 25B, which rotate in conjunction with this rotation, can dress the grinding wheels 34, 44, and 54, which will be described later.

[0029] Furthermore, three movable tables 12, 13, and 14 are fixed to the upper surface of the base 10, and grinding wheel bases 31, 41, and 51 of the grinding devices 30, 40, and 50 are arranged on these movable tables 12, 13, and 14, respectively. As a result, each grinding device 30, 40, and 50 can move independently relative to the base 10 in the Z-axis direction and the X-axis direction (horizontal front-back direction which is perpendicular to both the Y-axis and Z-axis directions). The movable tables 12, 13, and 14 can be configured, for example, using guide rails or feed screws, and are equipped with electric motors, also not shown, to move the grinding wheel bases 31, 41, and 51.

[0030] In each grinding device 30, 40, and 50, a processing head 32, 42, and 52 are mounted on a grinding wheel base 31, 41, and 51, respectively. Each processing head 32, 42, and 52 is rotatably supported by a rotating shaft 33, 43, and 53, respectively, and a short cylindrical grinding wheel 34, 44, and 54 are attached to the tip of each rotating shaft 33, 43, and 53, respectively.

[0031] Furthermore, each grinding wheel holder 31, 41, and 51 is equipped with a rotary motor 35, 45, and 55 as a drive unit, and the rotation of these rotary motors 35, 45, and 55 causes each grinding wheel 34, 44, and 54 to rotate via pulleys and belts (neither of which are shown).

[0032] Here, the first grinding device 30 is positioned such that its first grinding wheel 34 can grind the entire outer surface of the first stepped portion W1 of the workpiece W, as also shown in Figure 2. Specifically, the position and travel distance L1 of the first movable table 12 on which the first grinding device 30 is mounted are determined so that the first grinding wheel 34 can contact the outer surface of the workpiece W over the entire area of ​​the first stepped 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] The second grinding device 40, also referring to Figures 2 and 3, is positioned on the opposite side of the workpiece W from the first grinding device 30, with the workpiece W in between, so that its second grinding wheel 44 can grind the entire outer surface of the first stepped portion W1 and the intermediate portion W2 of the workpiece W. Specifically, the position and travel distance (L1 + L2) of the second movable table 13 on which the second grinding device 40 is installed are determined so that the second grinding wheel 44 can contact the outer surface of the workpiece W over the entire area of ​​the first stepped portion W1 and the intermediate portion W2. It is preferable that the rotation direction of the second grinding wheel 44 is opposite to the rotation direction of the workpiece W.

[0034] Furthermore, the third grinding device 50 is positioned at a distance in the Z-axis direction from the first grinding device 30, as also shown in Figure 3, so that the third grinding wheel 54 can grind the entire outer surface of the second stepped portion W3 of the workpiece W. Specifically, the position and travel distance L3 of the third movable table 14 on which the third grinding device 50 is mounted are determined so that the third grinding wheel 54 can contact the outer surface of the workpiece W over the entire area of ​​the second stepped portion W3. It is preferable that the rotation direction of the third grinding wheel 54 is the same as the rotation direction of the workpiece W.

[0035] Furthermore, although not shown, the grinding machine 100 includes a control unit (not shown) that controls the movement of the upper and lower sliding tables 11 in the Y-axis direction, the movement of the moving tables 12, 13, and 14 in the Z-axis and X-axis directions, the rotation of the rotary motors 23A and 23B of the rotation 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 consists of an arithmetic processing unit (e.g., CPU, processor, processor core) and a memory device (e.g., ROM, RAM, etc.). The control unit is configured to execute tasks by reading necessary data and programs (software) from the memory device and performing arithmetic processing on or based on the data according to the program.

[0037] The following describes a grinding method according to the first embodiment of the present invention, using the grinding machine 100 described above.

[0038] First, the workpiece W is clamped using the chucks 24A and 24B. Then, while the workpiece W is clamped, the control unit described above rotates the rotary motors 23A and 23B of the rotary support unit 20. This causes the workpiece W to continue rotating thereafter.

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

[0040] Furthermore, the control unit controls the position of the second grinding wheel 44 in the Z-axis direction, and consequently the position of the second movable table 13 in the Z-axis direction, as well as the feed rate of the second grinding wheel 44, and consequently the movement rate of the second movable table 13 in the X-axis direction, using the electric motor provided on the second movable table 13, so that the second grinding wheel 44 contacts the outer circumferential surface of the end of the first stepped portion W1 of the workpiece W.

[0041] Then, while maintaining the states of the above-described first and second grinding wheels 34 and 44, the control unit controls the rotational speed of the first grinding wheel 34, and thus the rotational speed of the rotation motor 35 of the first grinding device 30, and the rotational speed of the second grinding wheel 44, and thus the rotational speed of the rotation motor 45 of the second grinding device 40. Thereby, the grinding process on the outer peripheral surface of the first stepped portion W1 by the first and second grinding wheels 34 and 44 is simultaneously started.

[0042] Then, while controlling the feed rates of the first and second grinding wheels 34 and 44 by the control unit according to the cross-sectional shape of the first stepped portion W1 in this grinding state, the control unit also controls the movement amounts of the first and second grinding wheels 34 and 44 in the Z-axis direction. Thereby, the grinding process on the outer peripheral surface of the first stepped portion W1 by the first and second grinding wheels 34 and 44 proceeds simultaneously.

[0043] At this time, the movement distances of the first and second grinding wheels 34 and 44 in the Z-axis direction are L1. Thus, since the first stepped portion W1 is ground from opposite directions by the first and second grinding wheels 34 and 44, the grinding loads can support each other, so that good grinding accuracy can be obtained.

[0044] At this time, it is preferable that the first grinding wheel 34 and the second grinding wheel 44 are located at the same position in the Z-axis direction with the workpiece W sandwiched therebetween, but it is not limited thereto. Further, it is preferable that the grinding processes by the first and second grinding wheels 34 and 44 start simultaneously and end simultaneously, but it is not limited thereto. For example, one of them may start the grinding process first, and then one of them may end the grinding process first.

[0045] Also, the feed rates and rotational speeds of the first and second grinding wheels 34 and 44 may be the same or different from each other. For example, if the feed rate is decreased and the rotational speed is increased, the obtained grinding surface will have a smaller roughness. Thus, the feed rate of the first grinding wheel 34 may be decreased and the rotational speed may be increased to perform finish grinding, and the feed rate of the second grinding wheel 44 may be increased and the rotational speed 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 contact the outer peripheral surface of the workpiece W.

[0047] Next, the control unit controls the position of the second grinding wheel 44 in the Z-axis direction, and thus the position of the second moving table 13 in the Z-axis direction, and the feed rate of the second grinding wheel 44, and thus the moving speed of the second moving table 13 in the X-axis direction, by the above-described electric motor provided in the second moving table 13 so that the second grinding wheel 44 contacts the outer peripheral surface of the end portion of the intermediate portion W2 of the workpiece W.

[0048] Further, the control unit controls the position of the third grinding wheel 54 in the Z-axis direction, and thus the position of the third moving table 14 in the Z-axis direction, and the feed rate of the third grinding wheel 54, and thus the moving speed of the third moving table 14 in the X-axis direction, by the above-described electric motor provided in the third moving table 14 so that the third grinding wheel 54 contacts the outer peripheral surface of the end portion 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 and 54, the control unit controls the rotational speed of the second grinding wheel 44, and thus the rotational speed of the rotation motor 45 of the second grinding device 40, and the rotational speed of the third grinding wheel 54, and thus the rotational speed of the rotation motor 55 of the third grinding device 50. Thereby, the grinding of the outer peripheral surface of the intermediate portion W2 by the second grinding wheel 44 and the grinding of the outer peripheral surface of the second stepped portion W3 by the third grinding wheel 54 are simultaneously started.

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

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

[0052] In this case, it is preferable, but not limited to, that the grinding operations using the second and third grinding wheels 44 and 54 start and end simultaneously.

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

[0054] As described above, according to the first embodiment of the present invention, the first stepped portion W1 can be simultaneously ground by the first and second grinding wheels 34 and 44, and the intermediate portion W2 can be ground by the second grinding wheel 44 and the second stepped portion W3 can be ground by the third grinding wheel 54 simultaneously. This makes it possible to improve grinding efficiency compared to the grinding machines described in the above-mentioned Patent Documents 1 and 2.

[0055] The following describes a grinding method according to a second embodiment of the present invention, using the grinding machine 100 described above.

[0056] First, similar to the first embodiment described above, the workpiece W is rotated while being held in place by 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 circumferential surface of the end of the first stepped portion W1 of the workpiece W, the second grinding wheel 44 to contact the outer circumferential surface of the end of the intermediate portion W2, and the third grinding wheel 54 to contact the outer circumferential surface of the end of the second stepped portion W3 of the workpiece W.

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

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

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

[0061] In this way, the distance traveled by the first grinding wheel 34 in the Z-axis direction is L1, the distance traveled by the second grinding wheel 44 in the Z-axis direction is L2, and the distance traveled by 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 simultaneously ground by the first to third grinding wheels 34, 44, and 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 grind the workpiece W simultaneously, the grinding load acts from opposite directions, making it possible to obtain good grinding accuracy.

[0063] The following describes a grinding method according to a third embodiment of the present invention, using the grinding machine 100 described above.

[0064] First, similar to the first embodiment described above, the workpiece W is rotated while being held in place by 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 circumferential surface of the end of the first stepped portion W1 of the workpiece W, the second grinding wheel 44 to contact the outer circumferential surface of the end of the first stepped portion W1 of the workpiece W, and the third grinding wheel 54 to contact the outer circumferential surface of the end of the second stepped portion W3 of the workpiece W.

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

[0067] Then, in accordance with the cross-sectional shape of the first stepped portion W1, the feed rate of the first and second grinding wheels 34, 44 is controlled by the control unit, and the amount of movement of the first and second grinding wheels 34, 44 in the Z-axis direction is also controlled by the control unit. Furthermore, in accordance with the cross-sectional shape of the second stepped portion W3, the feed rate of the third grinding wheel 54 is controlled by the control unit, and the amount of movement of the third grinding wheel 54 in the Z-axis direction is also controlled by the control unit. As a result, grinding of the outer circumferential surface of the first stepped portion W1 by the first and second grinding wheels 34, 44 and grinding of the outer circumferential surface of the second stepped portion W3 by the third grinding wheel 54 proceed simultaneously.

[0068] Then, after grinding of the outer circumferential surface of the first stepped portion W1 by the second grinding wheel 44 is completed, the control unit controls the second grinding wheel 44 so that it contacts the outer circumferential surface of the end of the first stepped portion W1 of the workpiece W. Subsequently, the control unit controls the amount of movement of the second grinding wheel 44 in the Z-axis direction, while controlling the feed rate of the second grinding wheel 44 according to the cross-sectional shape of the intermediate portion W2.

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

[0070] In this way, the distance traveled by the first grinding wheel 34 in the Z-axis direction is L1, and the distance traveled by the third grinding wheel 54 in the Z-axis direction is L3. The distance traveled by 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 simultaneously ground by the first to third grinding wheels 34, 44, and 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 grind the workpiece W simultaneously, the grinding load acts from opposite directions, making it possible to obtain good grinding accuracy.

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

[0073] Furthermore, although the case in which the first to third grinding wheels 34, 44, and 54 are all movable in the X-axis direction has been described, the case is not limited to this. The direction of movement of the first to third grinding wheels 34, 44, and 54 is only required to be perpendicular to the Z-axis direction, and furthermore, the directions in which each of them can move may be different.

[0074] Furthermore, while we have described a case where the first to third grinding wheels 34, 44, and 54 are controlled to move independently in the X-axis and Z-axis directions, the case is not limited to this. For example, at least one of the first to third grinding wheels 34, 44, and 54 may be controlled to move simultaneously in the X-axis and Z-axis directions.

[0075] For example, although not shown in the diagram, the servo motors for movement in the X-axis direction and the servo motors for movement in the Z-axis direction of the first movable table 12 may be simultaneously controlled by two-axis NC to perform interpolation operations so that linear or arc movements occur within the X-axis-Y-axis plane for grinding. This allows the first grinding wheel 34 to rotate and perform oblique cuts on the workpiece W, making it possible to perform end face machining on the corners of the workpiece W. This interpolation operation may be performed simultaneously with the grinding operation of the other grinding wheels 44 and 54 on the workpiece W, or independently. Furthermore, this grinding operation of the other grinding wheels 44 and 54 may or may not be an interpolation operation.

[0076] Furthermore, the shape of the workpiece W described above is just one example, and the positions where each grinding device 30, 40, and 50 is installed and the distance of movement in the Z-axis direction should be determined as appropriate according to the shape of the workpiece W.

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

[0078] 10...Base, 11...Upper and lower sliding table, 12...First moving table, 13...Second moving table, 14...Third moving table, 20...Rotating support, 21A, 21B...Headstock, 22A, 22B...Spindle, 23A, 23B...Rotating motor, 24A, 24B...Chuck, 25A, 25B...Dresser, 30...First grinding device, 31...First grinding wheel holder, 32...First machining head, 33...First rotating shaft, 34...First grinding wheel, 35...First rotating motor, 40...Second grinding device, 41...Second grinding wheel holder, 42...Second machining head, 43...Second rotating shaft, 44...Second grinding wheel, 45...Second rotating motor, 50...Third grinding device, 51...Third grinding wheel holder, 52...Third machining head, 53...Third rotating shaft, 54...Third grinding wheel, 55...Third rotating motor, 100...Grinding machine, O...Axis, W...Workpiece, W1...First stepped section, W2...Intermediate section, W3...Second stepped section, Wa...Flange section.

Claims

1. A rotating support unit capable of rotating a long, rod-shaped workpiece around its 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 grinds the outer circumferential surface of the workpiece that it rotates and makes contact with; a second grinding wheel provided on the opposite side of the workpiece from the first grinding wheel, separated by the workpiece, and movable in the axial direction of the workpiece and in a direction perpendicular to that direction, and grinds the outer circumferential surface of the workpiece that it rotates and makes contact with; a third grinding wheel provided at a distance from the first grinding wheel in the axial direction of the workpiece, and movable in the axial direction of the workpiece and in a direction perpendicular to that direction, and grinds the outer circumferential surface of the workpiece that it rotates and makes contact with; and a control unit that controls the first grinding wheel, the second grinding wheel, and the second grinding wheel and the third grinding wheel to grind the outer circumferential surface of the workpiece simultaneously. A grinding machine characterized by grinding the outer circumferential surfaces of multiple locations on the aforementioned workpiece to process them into circular shapes with different cross-sectional shapes.

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

3. The grinding machine according to claim 1, characterized in that the rotating support portion is movable in the vertical direction while holding the workpiece.

4. The grinding machine according to claim 1, characterized in that the direction in which the first grinding wheel, the second grinding wheel, and the third grinding wheel can move is the same as the direction perpendicular to the axial direction of the workpiece.

5. The grinding machine according to claim 1, characterized in that the control unit controls the first grinding wheel, the second grinding wheel, and the third grinding wheel to grind the outer surface of the workpiece simultaneously.

6. The grinding machine according to claim 1, characterized in 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.

7. Using a grinding machine comprising: a rotating support unit capable of rotating a long, rod-shaped workpiece around its axis while clamping it in the longitudinal direction; a first grinding wheel movable in the axial direction of the workpiece and in a direction perpendicular to that direction, for grinding the outer circumferential surface of the workpiece that it rotates and makes contact with; a second grinding wheel provided on the opposite side of the workpiece from the first grinding wheel, separated by the workpiece, movable in the axial direction of the workpiece and in a direction perpendicular to that direction, for grinding the outer circumferential surface of the workpiece that it rotates and makes contact with; and a third grinding wheel provided at a distance from the first grinding wheel in the axial direction of the workpiece, movable in the axial direction of the workpiece and in a direction perpendicular to that direction, for grinding the outer circumferential surface of the workpiece that it rotates and makes contact with; 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 multiple locations on the workpiece so that they have circular cross-sectional shapes.

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