Rotation speed control method in centrifugal drum grinding and centrifugal drum grinding method

Abstract

Damage to a workpiece during acceleration of a drum groove is reduced. The rotational speed control method includes an acceleration control step in which a constant Ct based on a revolution rotational speed Nt (rpm) during polishing per minute, a rotation rotational speed nt (rpm) during polishing per minute, a revolution radius R (m) of a drum tank (12), and a gravitational acceleration g (9.8 m / s2) is calculated by formula (1): Ct = (2pi Nt / 60) 2 * R / (g * nt), the relative centrifugal acceleration F (G) based on the revolution speed N (rpm) per minute of the drum tank (12) during acceleration control, the revolution radius R (m) of the drum tank (12), and the gravitational acceleration g (9.8 m / s2) is defined by formula (2): F = (2pi N / 60) 2 * R / g. The revolution speed N (rpm) per minute of the drum tank (12) during acceleration control and the rotation speed n (rpm) per minute of the drum tank (12) during acceleration control are changed over time so as to satisfy formula (3): F / n > = Ct.

Description

Technical Field

[0001] This invention relates to a speed control method for centrifugal drum grinding and a centrifugal drum grinding method. Background Technology

[0002] Patent Document 1 discloses a centrifugal drum grinding apparatus comprising a turntable driven by a motor and a drum groove mounted at an eccentric position on the turntable. The drum groove revolves integrally with the turntable and rotates relative to itself, thereby performing planetary rotation. Within the planetarily rotating drum groove, the workpiece is ground by grinding stones.

[0003] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2010-005712 Summary of the Invention The problem the invention aims to solve In centrifugal drum grinding, if the centrifugal force acting on the drum groove is weaker than the drum groove's rotational speed, the workpiece will be damaged, i.e., suffer abnormal defects. Therefore, the revolution speed and rotational speed in drum grinding are set to take into account the speed of reducing damage. However, in conventional technology, the acceleration process from the grinding stop state to the drum groove reaching a grinding speed suitable for reducing damage does not consider the reduction of damage. Therefore, in the drum grinding apparatus described in Patent Document 1, etc., only a single drive motor rotates the turntable and the drum groove. During the acceleration process from the rotation stop state to the time when the revolution speed of the turntable and the rotation speed of the drum groove reach the target grinding speed, the rotational speed and revolution speed increase in the same proportion. Since the centrifugal force is proportional to the square of the revolution speed, the centrifugal force remains relatively small relative to the rotational speed during the acceleration process, and the workpiece may be damaged. After acceleration is completed and the target grinding speed is reached, the process directly transitions to the drum grinding process that maintains the target speed. Therefore, it is difficult to verify the state of workpiece damage during the acceleration process.

[0004] The present invention was made based on the above circumstances, and its purpose is to reduce the damage to the workpiece caused by acceleration in the roller groove.

[0005] means for solving problems The first disclosed method for controlling the rotational speed in centrifugal drum grinding is as follows: In centrifugal drum grinding, where grinding is performed by causing a drum containing a workpiece to rotate planetarily at a predetermined revolution speed and rotation speed during grinding, acceleration control is implemented in a manner that ensures the rotational speed of the drum reaches the specified revolution speed and rotation speed from a stopped state. The speed control method includes an acceleration control step, in which the revolution speed N during grinding is calculated based on the following formula (1). t (rpm), the rotational speed n during the grinding process. t (rpm), the revolution radius R (m) of the roller groove, and the gravitational acceleration g (9.8m / s²) 2 The constant C of ) t , C t =(2πN t / 60) 2 ×R / (g×n t ) (1), The revolution speed N (rpm), the revolution radius R (m), and the gravitational acceleration g (9.8 m / s²) of the roller trough in the acceleration control are calculated using the following formula (2). 2 The relative centrifugal acceleration F(G) is defined as follows: F = (2πN / 60) 2 ×R / g (2), The revolution speed N (rpm) of the roller trough in the acceleration control and the rotation speed n (rpm) of the roller trough in the acceleration control are made to change with time in a manner that satisfies the following formula (3). F / n≥C t (3).

[0006] The second disclosed centrifugal drum grinding method is as follows: Including the acceleration control process and constant speed grinding process described in the first disclosure, In the acceleration control process, the revolution direction and rotation direction of the roller groove are made to be opposite, and the rotation speed n during grinding is represented by a positive value. t (rpm), where a negative value represents the revolution speed N during grinding. t (rpm) In the constant-speed grinding process, the revolution speed N during grinding is set to the range of the following formula (4). t(rpm) and the rotational speed n during grinding t The grinding is performed by causing the roller groove to rotate planetarily at (rpm). -1≤n t / N t <0 (4).

[0007] The effects of the invention This configuration can reduce damage to the workpiece during acceleration in the roller groove. Attached Figure Description

[0008] Figure 1 This is a top view of the centrifugal drum mill as an example.

[0009] Figure 2 This is a cross-sectional view of a centrifugal drum mill.

[0010] Figure 3 The graph shows the changes in rotational speed and relative centrifugal acceleration over time in Experiment 1.

[0011] Figure 4 The graph shows the changes in rotational speed and relative centrifugal acceleration over time in Experiment 2.

[0012] Figure 5 The graph shows the changes in rotational speed and relative centrifugal acceleration over time in Experiment 3.

[0013] Figure 6 The graph shows the changes in rotational speed and relative centrifugal acceleration over time in Example 10 of Experiment 4.

[0014] Figure 7 The graph shows the changes in rotational speed and relative centrifugal acceleration over time in Example 11 of Experiment 4. Detailed Implementation

[0015] First, embodiments of this disclosure are listed and described. Without causing contradiction, any combination of the following embodiments is included in the manner of carrying out the invention.

[0016] The first disclosed method for controlling the rotational speed in centrifugal drum grinding is as follows: [1] A speed control method in centrifugal drum grinding, which grinds by causing a drum groove containing a workpiece to rotate planetarily at a predetermined grinding revolution speed and grinding spin speed, wherein the speed of the drum groove is accelerated from a state of rotational stop to the grinding revolution speed and grinding spin speed, wherein the speed control method includes an acceleration control step, in which the grinding revolution speed N per minute is calculated using formula (1). t (rpm), the rotational speed n during the grinding process. t (rpm), the revolution radius R (m) of the roller groove, and the gravitational acceleration g (9.8m / s²) 2 The constant C of ) t , C t =(2πN t / 60) 2 ×R / (g×n t ) (1), Formula (2) defines the revolution speed N (rpm) of the roller trough in acceleration control, the revolution radius R (m) of the roller trough, and the gravitational acceleration g (9.8 m / s²). 2 The relative centrifugal acceleration F(G) of ) F = (2πN / 60) 2 ×R / g (2), The revolution speed N (rpm) of the roller trough in the acceleration control and the rotation speed n (rpm) of the roller trough in the acceleration control are made to change with time in a manner that satisfies formula (3). F / n≥C t (3).

[0017] The centrifugal force acting on the drum groove is proportional to the relative centrifugal acceleration F. When the revolution speed N and rotation speed n are controlled as an equation (3), the ratio of the centrifugal force (relative centrifugal acceleration F) to the rotation speed n in acceleration control is maintained as the ratio of the centrifugal force (relative centrifugal acceleration F) to the rotation speed n during grinding. tThe ratio is the same. When the revolution speed N and rotation speed n are controlled in a manner that makes Equation (3) an inequality, the ratio of centrifugal force (relative centrifugal acceleration F) in acceleration control to rotation speed n is maintained to be greater than the ratio of centrifugal force (relative centrifugal acceleration F) to rotation speed n during grinding. t The ratio of the centrifugal force to the rotational speed n. According to this disclosure, in the acceleration control process that increases the revolution speed N and rotational speed n of the drum groove, the ratio of centrifugal force to rotational speed n during grinding is suppressed from being less than the ratio of centrifugal force to rotational speed n during grinding. t Damage caused by the ratio.

[0018] [2] The acceleration control process preferably includes a revolution-limited acceleration process, in which the revolution speed N (rpm) is increased without changing the rotation speed n (rpm) from the state where the rotation of the roller groove stops. According to this configuration, the ratio of centrifugal force (relative centrifugal acceleration F) to rotation speed n increases immediately after the acceleration control begins, thus achieving a high effect in suppressing damage.

[0019] [3] In [1] or [2], it is preferable that the rotation center axis of the roller groove is vertical. When the rotation center axis of the roller groove is horizontal, the direction and magnitude of the resultant force of centrifugal force and gravity acting on the roller groove vary depending on the position of the roller groove in its revolution path. Therefore, the flow state of the mixture (mass) in the roller groove also varies depending on the position of the roller groove in its revolution path, which may result in a state where the flow of the mixture becomes intense and easily damaged. In contrast, if the rotation center axis of the roller groove is vertical, the centrifugal force acting on the roller groove is always horizontal and is not affected by the gravitational acceleration acting in the vertical direction, thus maintaining a state that is difficult to damage.

[0020] The second disclosed centrifugal drum grinding method is as follows: [4] A centrifugal drum grinding method, comprising: the acceleration control steps described in [1] to [3], wherein the revolution direction of the drum groove is opposite to its rotation direction, and the rotation speed n during grinding is represented by a positive value. t (rpm), where a negative value represents the revolution speed N during grinding. t (rpm); and The constant-speed grinding process uses the revolution speed N during grinding, which is set to the range of formula (4). t (rpm) and the rotational speed n during grinding t The grinding is performed by causing the roller groove to rotate planetarily at (rpm). -1≤n t / N t <0 (4).

[0021] According to this configuration, damage to the workpiece is suppressed during the centrifugal drum grinding process in which the drum groove rotates planetarily at a specified speed. Therefore, damage can be suppressed continuously from the start of the acceleration control process to the end of the grinding process.

[0022] <Implementation Method 1> The following is for reference Figures 1-7 The following describes embodiment 1, which embodies the present invention. Figure 1 , 2 A centrifugal tumbler grinding machine 10 is shown for performing the centrifugal tumbler grinding method of Embodiment 1. The centrifugal tumbler grinding method is a method of grinding a workpiece (not shown) within the tumbler groove 12 by causing the tumbler groove 12 mounted on the turret 11 to rotate planetarily. The centrifugal tumbler grinding method is a method of sequentially performing an acceleration control process, a constant speed grinding process, and a deceleration control process.

[0023] like Figure 1 , 2 As shown, the centrifugal drum mill 10 has a revolution shaft 13 that rotates vertically and integrally with a turret 11, and a revolution motor 15 that transmits rotational force to the revolution shaft 13 via a revolution belt 14. The revolution motor 15 is a motor whose output speed can be changed by an inverter control. The revolution shaft 13 and the turret 11 are driven to rotate by the revolution motor 15.

[0024] A plurality of roller slots 12 (four in this embodiment) are installed on the turret 11. The roller slots 12 are arranged at equal angular intervals in the circumferential direction at a position eccentrically outward from the rotation center (center of the revolution axis 13) of the turret 11. Each roller slot 12 is capable of rotating integrally with the rotation axis 16, whose axis is oriented vertically. The rotational force of the rotation motor 18 is transmitted to the rotation axis 16 via the rotation belt 17. The rotation motor 18 is a motor whose speed can be varied by an inverter control. The roller slots 12 and the rotation axis 16 are driven by the rotation of the rotation motor 18. Each roller slot 12 is capable of relative rotation with respect to the turret 11. In a top view parallel to the revolution axis 13 and the rotation axis 16, the inner surface of the roller slot 12 (not shown) is a regular polygon.

[0025] The rotational speeds of the revolution motor 15 and the rotational speeds of the self-rotation motor 18 are individually controlled by the control device 19. By independently driving the revolution motor 15 and the self-rotation motor 18, the roller groove 12 revolves together with the turret 11 while simultaneously rotating relative to the turret 11 (relative rotation), thus performing planetary rotation. From a top-down view, the revolution direction of the roller groove 12 (the rotation direction of the turret 11) and the rotation direction of the roller groove 12 are opposite.

[0026] Within the planetary rotating drum groove 12, a flow layer on the surface of a mixture (not shown) comprising the workpiece and grinding stones (not shown) flows in an avalanche-like manner, and the workpiece is ground by the grinding stones. If the flow layer of the mixture is thick, the workpiece is easily damaged; if the flow layer is thin, the generation of damage in the workpiece is suppressed. Therefore, in a constant-speed grinding process in which the drum groove 12 rotates planetarily at a specified speed, the revolution speed (hereinafter referred to as "revolution speed N during grinding") is set considering the suppression of damage generation. t (rpm)” and rotational speed (hereinafter referred to as “rotational speed n during grinding”). t (rpm)”). Specifically, the revolution speed N during grinding. t And the rotation speed n during grinding t It is set to satisfy formula (4). -1≤n t / N t <0 (4).

[0027] The revolution direction and rotation direction of the roller groove 12 are opposite. Therefore, the rotation speed n during grinding is represented by a positive value. t The negative value N represents the revolution speed during grinding. t Therefore, n t / N t It is a negative value.

[0028] The inventors of this application propose an acceleration control method, which controls the rotational speed N from the point where the roller groove 12 stops rotating until the roller groove 12 reaches the grinding speed. t And the rotation speed n during grinding t In the accelerated process described above, damage can be suppressed. This acceleration control method is based on the following insight and experiments, which is that if the centrifugal force acting on the roller groove 12 is weaker than the rotational speed of the roller groove 12, the flow layer of the mixture becomes thicker, making the workpiece more susceptible to damage.

[0029] [Experiment 1] In Experiment 1, a centrifugal drum grinder 10 with a revolution radius R of 0.18 m was used. Grinding stones HS-3 (not shown), manufactured by Tipton Co., Ltd., shaped into spheres with a diameter of 3 mm, were placed into the drum 12. A magnetic workpiece (not shown), shaped as a rectangle of 10 mm × 5 mm × 2 mm, was also placed into the drum 12. The amount of grinding stones, including the volume of the gaps between the grinding stones, was 50% of the volume of the drum 12.

[0030] In Experiment 1, the revolution speed N of the roller groove 12 was made to reach the revolution speed N during grinding within 30 seconds from the state of rotation stop. t The speed increases (accelerates) at a predetermined rate (446 rpm). The revolution speed N during grinding... t The target rotational speed N (rpm) in the acceleration control process of Examples 1-4 is to be achieved. In the following description, "increasing the rotational speed of the roller groove 12" and "accelerating the rotational speed of the roller groove 12" are used to mean the same thing. Formula (2) represents the rotational speed N per minute of the roller groove 12, the rotational radius R (m) of the roller groove 12, and the gravitational acceleration g (9.8 m / s²). 2 The relative centrifugal acceleration F(G) of ) F = (2πN / 60) 2 ×R / g (2).

[0031] The relative centrifugal acceleration F is proportional to the square of the revolution speed N. In Experiment 1, 30 seconds after the rotation stopped, the relative centrifugal acceleration F was 40G.

[0032] In Experiment 1, four examples of acceleration control were conducted, each with a different method of increasing the rotational speed n of the drum groove 12, while ensuring that the upward pattern of the revolution speed N was consistent. In all four examples, the rotational speed n required for grinding was reached within 30 seconds from the point of rotational stop. t The rotational speed n (rpm) is increased by 300 rpm. The rotational speed n during grinding... t To achieve the target rotational speed n in the acceleration control process of Examples 1-4. Table 1 and Figure 3 The results of Experiment 1 are shown.

[0033] [Table 1]

[0034] In Example 1, the rotational speed n is increased from the stationary state with a specified acceleration, just like the revolution speed N.

[0035] In Examples 1-3, the revolution speed N during grinding was set... t The rotational speed n during grinding is 446 rpm, making the revolution radius of the roller groove 12 0.18 m, and the rotational speed n during grinding. t Based on 300 rpm, the relative centrifugal acceleration F during grinding is calculated using formulas (2-1) and (3'). t Divide by the rotational speed n during grinding t The constant C obtained t The constant C is obtained. t =0.1334, F t =(2πN t / 60) 2 ×R / g (2-1) C t =F t / n t (3').

[0036] The revolution speed N and rotation speed n in the acceleration control process are made to change with time in a manner that satisfies the following formulas (2) and (3-1). F = (2πN / 60) 2 ×R / g (2) F / n≥0.1334 (3-1).

[0037] In Example 1, the rotational speed n is varied at each elapsed time in a manner that satisfies formula (5-1). n=F / 0.1334 (5-1).

[0038] In Example 2, from the start of the rotation stop state until 22.5 seconds, the rotation of the roller groove 12 is stopped (the rotation speed n is not increased). During the 7.5-second period from 22.5 seconds to 30 seconds, the rotation speed n is increased from 0 rpm to 300 rpm at a predetermined ratio (predetermined acceleration). In Example 3, the rotation speed n for each elapsed time is set to a value calculated by the exponential function exp(0.1901 × each elapsed time).

[0039] In each example, the experiment of stopping the revolution and rotation of the roller groove 12 after 30 seconds of acceleration control as described above was repeated 40 times to evaluate the damage rate of the workpiece. Of the four examples, Existing Example 1 had the highest damage rate, followed by Example 1 with a lower damage rate. Example 2 and Example 3 had damage rates of the same degree, lower than Example 1. The damage rates of Existing Example 1, Example 1, Example 2, and Example 3 were evaluated as "B: Moderate," "A: Low," and "AA: Very Low," respectively.

[0040] The reason why the damage rate in Examples 1-3 is lower than that in Existing Example 1 can be inferred as follows. In Existing Example 1, the rotational speed n and the revolution speed N are increased at the same predetermined ratio (acceleration), therefore, the centrifugal force is smaller than the rotational speed n, resulting in more damage. In contrast, in Examples 1-3, the relative centrifugal acceleration F, which is proportional to the square of the revolution speed N, is calculated based on the revolution speed N during grinding. t The rotational speed n during grinding t And the constant C of the orbital radius R t To satisfy formula (3), the revolution speed N (relative centrifugal acceleration F) and the rotation speed n in the acceleration control process are changed. Formula (3) is F / C t ≥n. In Figure 3 In the graph, the region on and above the straight line representing Example 1 represents the revolution speed N and rotation speed n, satisfying the constant C mentioned above. t The formula for changing the way damage is generated reduces the area. Figure 3 In the graph, the more the revolution speed N and rotation speed n bulge towards the upper left, the less damage to the workpiece.

[0041] [Experiment 2] The centrifugal drum grinder 10, grinding stones, workpiece, and the rising pattern of the revolution speed N used in Experiment 2 were the same as in Experiment 1. In Experiment 2, based on the common rising pattern of the revolution speed N, four examples of acceleration control were implemented using different methods to increase the rotational speed n of the drum groove 12. In all four examples, the rotational speed n was increased to 100 rpm within 30 seconds from the starting point of rotational stop. Table 2 and... Figure 4 The results of Experiment 2 are shown.

[0042] [Table 2]

[0043] In Example 2, the rotational speed n is increased with a specified acceleration from the state of rotational stop, just like the revolution speed N.

[0044] In Examples 4-6, the revolution speed N during grinding was set... t The rotational speed n during grinding is 446 rpm, making the revolution radius of the roller groove 12 0.18 m, and the rotational speed n during grinding. t Based on 100 rpm, the relative centrifugal acceleration F during grinding is calculated using formulas (2-1) and (3'). t Divide by the rotational speed n during grinding t The constant C t The constant C is obtained. t =0.40003, F t =(2πN t / 60) 2 ×R / g (2-1) C t =F t / n t (3'). To satisfy the following formulas (2) and (3-2), the revolution speed N and rotation speed n in the acceleration control process are made to change with time. F = (2πN / 60) 2 ×R / g (2) F / n≥0.4003 (3-2).

[0045] In Example 4, the rotational speed n is varied at each elapsed time in a manner that satisfies formula (5-2). n=F / 0.4003 (5-2).

[0046] The acceleration control process in Example 5 includes a revolution-limited acceleration process that increases the revolution speed N without changing the rotational speed n. In Example 5, from the start of the rotational stop state until 20 seconds, the rotation of the roller groove 12 is stopped (the rotational speed n is not increased). During the 10-second period from 20 seconds to 30 seconds, the rotational speed n increases from 0 rpm to 100 rpm at a predetermined ratio (predetermined acceleration). In Example 6, the rotational speed n at each elapsed time is set to a value calculated by the exponential function exp(0.1535 × each elapsed time).

[0047] In each example, the experiment of stopping the revolution and rotation of the roller groove 12 after 30 seconds of acceleration control as described above was repeated 40 times to evaluate the damage rate of the workpiece. Of the four examples, Existing Example 2 had the highest damage rate, to the same extent as Example 1 of Experiment 1. Following Existing Example 2, Example 4 had the lowest damage rate, to the same extent as Examples 2 and 3. Examples 5 and 6 had the same damage rate, lower than Example 4. The damage rates of Existing Example 2, Example 4, Example 5, and 6 were evaluated as "A: Low", "AA: Very Low", and "AAA: Extremely Low", respectively.

[0048] Compared with Existing Example 1 and Examples 1-3 in Experiment 1, the damage incidence rate of Existing Example 2 and Examples 4-6 in Experiment 2 was lower. The reason is that the revolution speed N in Experiment 1 and Experiment 2 was the same, while the rotation speed n during grinding in Experiment 1 was different. t (100 rpm) is the rotational speed n during grinding in Experiment 2. t The low 300 rpm speed results in a more stable flow of the mixture, which is the main reason for this. Additionally, at... Figure 4 In the graph, the region on and above the straight line representing Example 4 represents the revolution speed N and rotation speed n, satisfying the constant C mentioned above. t The damage generated by the change in the manner of formula (3-2) reduces the area.

[0049] [Experiment 3] The centrifugal drum grinder 10, grinding stones, and workpiece used in Experiment 3 were the same as in Experiments 1 and 2. The rate of increase of the revolution speed N differed from that in Experiments 1 and 2; instead, it increased at a predetermined rate (acceleration) by reaching 300 rpm within 30 seconds from a standstill. In Experiment 3, the relative centrifugal acceleration F was 18G 30 seconds after the start of rotation.

[0050] In Experiment 3, based on the common increase pattern of the revolution speed N, four examples of acceleration control were conducted with different methods for increasing the rotation speed n of the roller groove 12. In all four examples, the rotation speed n was increased to 300 rpm within 30 seconds from the starting point of rotational stop. Table 3 and... Figure 5 The results of Experiment 3 are shown.

[0051] [Table 3]

[0052] In Example 3, the rotational speed n is increased at a predetermined acceleration from the state of rotational cessation, just like the revolution speed N.

[0053] In Examples 7-9, the revolution speed N during grinding was set... t The rotational speed n during grinding is set to 300 rpm, making the revolution radius of the roller groove 12 0.18 m, and the rotational speed n during grinding. t Based on 300 rpm, the relative centrifugal acceleration F during grinding is calculated using formulas (2-1) and (3'). t Divide by the rotational speed n during grinding t The constant C obtained t The constant C is obtained. t =0.0604, F t =(2πN t / 60) 2 ×R / g (2-1) C t =F t / n t (3').

[0054] The revolution speed N and rotation speed n in the acceleration control process are made to change with time in a manner that satisfies the following formulas (2) and (3-3). F = (2πN / 60)2 ×R / g (2) F / n≥0.0604 (3-3).

[0055] In Example 7, the rotational speed n is varied at each elapsed time in a manner that satisfies formula (5-3). n=F / 0.0604 (5-3).

[0056] The acceleration control process in Example 10 includes a revolution-limited acceleration process that increases the revolution speed N without changing the rotational speed n. In Example 8, from the start of the rotational stop state until 22.5 seconds, the rotation of the roller groove 12 is stopped (in a state where the rotational speed n does not increase). From 22.5 seconds to 30 seconds, within 7.5 seconds, the rotational speed n increases from 0 rpm to 300 rpm at a predetermined ratio (predetermined acceleration). In Example 9, the rotational speed n for each elapsed time is set to a value calculated by the exponential function exp(0.1901 × each elapsed time).

[0057] In each example, the experiment of stopping the revolution and rotation of the roller groove 12 after 30 seconds of acceleration control as described above was repeated 40 times to evaluate the damage rate of the workpiece. Of the four examples, Existing Example 3 had the highest damage rate. Following Existing Example 3, Example 7 had a low damage rate, to the same extent as Existing Example 1. Examples 8 and 9 had damage rates to the same extent as Example 7, lower than Example 7, and to the same extent as Example 1 and Existing Example 2. The damage rates of Existing Example 3, Example 7, Example 8, and Example 9 were evaluated as "C: High", "B: Moderate", and "A: Low", respectively.

[0058] The damage rates of Existing Example 3 and Examples 7-9 in Experiment 3 were generally higher than those of Existing Example 1 and Examples 1-3 in Experiment 1. The reason for this is that the revolution speed N during grinding in Experiment 3 was higher. t (300 rpm) is the same as the revolution speed N during grinding in Experiment 1. t The relative centrifugal acceleration F (18.1G) in Experiment 3 was lower than that in Experiment 1 (40G), so the main reason is that the flow of the mixture is unstable.

[0059] exist Figure 5 In the graph, the region above the straight line representing Example 7 and the straight line representing Example 4 represents the revolution speed N and the rotation speed n, satisfying the constant C mentioned above. t The damage generation reduction region is obtained by varying the method of formula (3-3). In Examples 7-9, since the revolution speed N and rotation speed n have been varied to this damage generation reduction region, the damage generation rate is lower than that in Example 3.

[0060] [Experiment 4] The centrifugal drum grinder 10, grinding stones, and workpieces used in Experiment 4 were the same as in Experiments 1-3. The rate of increase of the revolution speed N differed from that in Experiments 1-3, reaching the grinding revolution speed N within 15 seconds from the point of rotational stop. t The revolution speed N is increased (accelerated) at a specified rate in a manner of (446 rpm), and then maintained at the revolution speed N during grinding for 15 to 30 seconds. t .

[0061] In Experiment 4, two acceleration control examples were conducted, each with a similar pattern of increasing the revolution speed N, but with different methods of increasing the rotation speed n of the roller groove 12. In both examples, the rotation speed n was increased to 300 rpm within 30 seconds from a stop position. Table 4 and... Figure 6 , Figure 7 The results of Experiment 4 are shown.

[0062] [Table 4]

[0063] The acceleration control process in Example 10 includes a revolution-limited acceleration process that increases the revolution speed N without changing the rotation speed n. In Example 10, the revolution speed N is increased from the rotation stop state until the revolution speed N reaches the grinding speed. t During the 15-second period up to 15 seconds, the rotation of the roller groove 12 is stopped (the rotation speed n is not increased). During the 15-second period from 15 seconds to 30 seconds, the rotation speed n is increased from 0 rpm to 300 rpm at a specified ratio (specified acceleration). Figure 6 The variations in revolution speed N and rotation speed n in Example 10 are shown. The damage incidence rate of Example 10 is "AA: Very Low".

[0064] In Example 11, from the point where rotation stops until the revolution speed N reaches the grinding speed, the revolution speed N is... t During the 15-second period up to (446 rpm), the constant C used was greater than that in Example 1. tThe large constant Ca (0.1334) in formula (3-4) causes the revolution speed N and rotation speed n to vary. F / n=Ca (3-4).

[0065] During the period from 15 seconds to 30 seconds, the revolution speed N during grinding was maintained. t Under these conditions, the rotational speed n increases. Figure 7 The variations in revolution speed N and rotation speed n in Example 11 are shown. The damage incidence rate in Example 11 is "AA: Very Low".

[0066] [Experiment 5] Experiment 5 used the same centrifugal drum grinder 10 as Experiments 1-4 for drum grinding. In the drum grinding, 50 vol% of the same grinding stone HS-3 as in Experiments 1-4 was added to the drum trough 12, along with 10 magnetic workpieces identical to those in Experiments 1-4.

[0067] In Example 12, after accelerating the revolution speed N and rotation speed n of the roller groove 12 in the same configuration as in Existing Example 1, the revolution speed N during grinding is the same as in Existing Example 1. t And the rotation speed n during grinding t Grinding was performed for 5 minutes. In Example 13, after accelerating the revolution speed N and rotation speed n of the roller groove 12 in the same manner as in Existing Example 2, the revolution speed N during grinding was the same as in Existing Example 2. t And the rotation speed n during grinding t Grinding was performed for 5 minutes. In Example 14, after accelerating the revolution speed N and rotation speed n of the roller groove 12 in the same manner as in Existing Example 3, the revolution speed N during grinding was the same as in Existing Example 3. t And the rotation speed n during grinding t Grind for 5 minutes.

[0068] In each of Examples 12-14, the damage generation rate and edge rounding amount were measured 10 times after 5 minutes of grinding. The edge rounding amount is the radius at the center of the corner edge with a length of 10 mm on the outer surface of the magnetic workpiece. The damage generation rate and corner edge rounding amount values ​​shown in Table 5 are the average values ​​of 10 × 10 = 100.

[0069] [Table 5]

[0070] In Examples 12 and 14, the rotational speed n during grinding was...t The results are similar, but the damage rate in Example 12 is lower than that in Example 14. The amount of grinding in Example 12, i.e., the amount of edge rounding at the corners of the workpiece, is about 1.5 times greater than that in Example 14. The reason for this is that in Example 12, the relative centrifugal acceleration F is greater, so the mixture is pushed against the inner wall of the roller groove 12, the thickness of the flow layer becomes thinner, and the workpiece flows stably within the mixture.

[0071] In Examples 12 and 13, the revolution speed N during grinding was... t The results were similar, but the damage rate in Example 13 was lower than that in Example 12. Additionally, the edge rounding amount in Example 13 was less than that in Example 12, but the same as in Example 14. This is because the rotational speed n during grinding in Example 13 was higher. t Smaller than Example 12, therefore, in Example 13, compared to Example 12, the mixture is pushed towards the outer side of the inner wall of the roller groove 12, and the thickness of the flow layer is reduced due to the lower rotational speed n during grinding. t It becomes thinner, thus the workpiece flows very slowly and steadily within the mixture.

[0072] The rotational speed control method of this embodiment 1 is as follows: when the roller groove 12 containing the workpiece is ground at a predetermined rotational speed N per minute... t And the rotational speed n during grinding t In centrifugal drum grinding, where planetary rotation is used for grinding, the rotational speed of the drum groove 12 is increased from the stationary state to the revolution speed N during grinding. t And the rotational speed n during grinding t This refers to a method of acceleration control.

[0073] The acceleration control method includes the following acceleration control steps. In this acceleration control step, the revolution speed N during grinding per minute is calculated using formula (1). t The rotational speed n during grinding per minute t The revolution radius R of the roller groove 12 and the constant C of gravitational acceleration g. t , C t =(2πN t / 60) 2 ×R / (g×n t ) (1).

[0074] Furthermore, the revolution speed N per minute of the roller trough 12, the revolution radius R of the roller trough 12, and the relative centrifugal acceleration F of the gravitational acceleration g are defined by formula (2). F = (2πN / 60) 2 ×R / g (2).

[0075] Based on this, the revolution speed N per minute of the roller groove 12 in the acceleration control and the rotation speed n per minute of the roller groove 12 in the acceleration control are made to change with time in a manner that satisfies formula (3). F / n≥C t (3).

[0076] The centrifugal force acting on the drum groove 12 is proportional to the relative centrifugal acceleration F. When the revolution speed N and rotation speed n are controlled using equation (3), the ratio of the centrifugal force (relative centrifugal acceleration F) to the rotation speed n in the acceleration control is maintained at the same ratio as the ratio of the centrifugal force (relative centrifugal acceleration F) to the rotation speed n during grinding. t The ratios are the same. When the revolution speed N and rotation speed n are controlled by the inequality of formula (3), the ratio of centrifugal force (relative centrifugal acceleration F) to rotation speed n in acceleration control is maintained to be greater than the ratio of centrifugal force (relative centrifugal acceleration F) to rotation speed n during grinding. t The value of the ratio. According to Embodiment 1, in the acceleration control process that increases the revolution speed N and rotation speed n of the drum groove 12, the ratio of centrifugal force to rotation speed n is suppressed because it is less than the ratio of centrifugal force to rotation speed n during grinding. t The damage caused by the ratio.

[0077] In the acceleration control process of embodiments 2, 5, 8, and 10, a revolution-limited acceleration process is included, which increases the revolution speed N without changing the rotation speed n from the state where the rotation and revolution of the roller groove 12 have stopped. According to this control process, the ratio of centrifugal force (relative centrifugal acceleration F) to rotation speed n can be maintained at a high value immediately after the acceleration control begins, thus achieving a high effect in suppressing the generation of damage.

[0078] When the rotation center axis of the roller groove 12 is horizontal, the direction and magnitude of the resultant force of the centrifugal force and gravity acting on the roller groove 12 vary depending on its position in the revolution path of the roller groove 12. Therefore, the flow state of the mixture within the roller groove 12 also varies depending on its position in the revolution path of the roller groove 12, potentially leading to a state where the flow of the mixture becomes intense and prone to damage. In view of this, in this embodiment 1, the rotation center axis of the roller groove 12, i.e., the axis of revolution 13 and the axis of rotation 16, is set to the vertical direction. If the rotation center axis of the roller groove 12 is vertical, the centrifugal force acting on the roller groove 12 is always horizontal and is not affected by the gravitational acceleration acting in the vertical direction, thus maintaining a state where damage is less likely to occur.

[0079] In the centrifugal drum grinding method of Embodiment 1, Examples 12, 13, and 14 include the aforementioned acceleration control step and constant-speed grinding step. The revolution speed of the drum groove 12 during grinding is defined as the revolution speed N during grinding. t The rotational speed of the grinding drum 12 is defined as the rotational speed n during grinding. t In the constant-speed grinding process, the grinding revolution speed N is set within the range of formula (4). t And the rotation speed n during grinding t The roller groove 12 rotates planetarily. -1≤n t / N t <0 (4).

[0080] The revolution direction and rotation direction of the roller groove 12 are opposite. The rotation speed n during grinding is... t A positive value indicates the revolution speed N during grinding. t The value is negative. Therefore, n t / N t It is a negative value. As shown in Table 5, n in Examples 12, 13, and 14 t / N t The values ​​all satisfy the above formula. According to the drum grinding method of this embodiment 1, in the constant-speed grinding process of centrifugal drum grinding by rotating the drum groove 12 at a predetermined speed, the occurrence of workpiece damage is suppressed. Therefore, the occurrence of damage can be suppressed from the start of the acceleration control process of the drum groove 12 until the end of the grinding process.

[0081] <Other Implementation Methods> The present invention is not limited to the embodiment 1 described above and illustrated in the accompanying drawings. For example, the following embodiments are also included within the technical scope of the present invention.

[0082] In the drum grinding machine of Embodiment 1, the rotation axis of the drum groove is vertical, but the axial direction of the rotation axis (revolution axis and rotation axis) of the drum groove can be horizontal. When the rotation axis of the drum groove is made horizontal, the damage generation rate can be lower than that of conventional acceleration methods according to the acceleration control method of this disclosure.

[0083] In the acceleration control process of experiments 1-4 above, the revolution speed N is increased until the relative centrifugal acceleration F reaches the target value of 18G or 40G. However, the target value of the relative centrifugal acceleration F in the acceleration control process can be around 5G to 15G, which is the conventional centrifugal drum grinding range. In this case, in the grinding process, it is preferable to set the value obtained by dividing the rotation speed n by the revolution speed N to satisfy -1≤n / N<0.

[0084] In the existing examples 1-3 and examples 1-14 of Embodiment 1 described above, a workpiece and a grinding stone are placed into the drum groove, and the workpiece is ground by the grinding stone. However, it is also possible to place only the workpiece into the drum groove, and the workpieces grind each other by contact, i.e., "mutual friction grinding". In this case, the acceleration control method of this disclosure can suppress the generation of damage in the workpiece.

[0085] In the deceleration process following the constant-speed grinding process, the revolution speed N during grinding is... t The relative centrifugal acceleration obtained by substituting into formula (2) is denoted as F. t Based on this, the rotational speed n of the roller groove per minute is varied with time in a manner that satisfies formula (5), thereby achieving deceleration control and suppressing damage during the deceleration process. F≥F t -C t ×n (5).

[0086] Explanation of reference numerals in the attached figures 10: Centrifugal drum mill 12: Roller groove, 13: Revolution axis (center of rotation) 16: Rotation axis (center axis of rotation).

Claims

1. A method for controlling the rotational speed in centrifugal drum grinding, wherein in centrifugal drum grinding, which involves planetary rotation of a drum containing a workpiece at a predetermined revolution speed and rotational speed during grinding, the method accelerates the rotational speed of the drum from a stopped state to the predetermined revolution speed and rotational speed during grinding, wherein... The speed control method includes an acceleration control step, in which the revolution speed N during grinding is calculated based on the following formula (1). t (rpm), the rotational speed n during the grinding process. t (rpm), the revolution radius R (m) of the roller groove, and the gravitational acceleration g (9.8m / s²) 2 The constant C of ) t , C t =(2πN t / 60) 2 ×R / (g×n t ) (1), The revolution speed N (rpm) of the roller trough, the revolution radius R (m) of the roller trough, and the gravitational acceleration g (9.8 m / s²) in the acceleration control are given by the following formula (2). 2 The relative centrifugal acceleration F(G) is defined as follows: F=(2πN / 60) 2 ×R / g (2), The revolution speed N (rpm) of the roller trough in the acceleration control and the rotation speed n (rpm) of the roller trough in the acceleration control are made to vary with time in a manner that satisfies the following formula (3). F / n≥C t (3)。 2. The speed control method in centrifugal drum grinding according to claim 1, wherein, The acceleration control process includes a revolution-limited acceleration process, in which, starting from the stop state of the rotation of the roller groove, the rotation speed n (rpm) is not changed, but the revolution speed N (rpm) is increased.

3. The speed control method in centrifugal drum grinding according to claim 1 or 2, wherein, The rotation center axis of the roller groove is in the vertical direction.

4. A centrifugal drum grinding method, wherein, Includes a constant-speed grinding process and an acceleration control process as described in claim 1 or 2. In the acceleration control process, the revolution direction and rotation direction of the roller groove are made to be opposite, and the rotation speed n during grinding is represented by a positive value. t (rpm), where a negative value represents the revolution speed N during grinding. t (rpm) In the constant-speed grinding process, the revolution speed N during grinding is set to the range of the following formula (4). t (rpm) and the rotational speed n during grinding t The grinding is performed by causing the roller groove to rotate planetarily at (rpm). -1≤n t / N t <0 (4)。

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