JP2013215853A - Method for improving dynamic rigidity and damping capacity while maintaining and improving static rigidity of coupled structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for improving a dynamic rigidity and a damping capacity while maintaining or improving the static rigidity of a coupled portion.SOLUTION: There is provided a method including the steps of: preparing a coupled structure with a first member, a second member, an elastic member, and a fastening member; regulating an interference between the first member and the second member; and arranging the elastic member between the first member and the second member to fasten the first and second members using the fastening member so that a first abutting surface and a second abutting surface abut against each other at given coupling contact pressure. At this time, the interference and the given coupling contact pressure are regulated so that the equivalent rigidity of a coupling portion is equal to or more than that obtained when the elastic member is not interposed therebetween and an equivalent viscous damping coefficient increases.

Description

  The present invention relates to a method for improving dynamic rigidity and damping capacity while maintaining or improving static rigidity in a joint structure in a machine tool or the like.

  A wide variety of industrial products such as food, medicine, clothing, and buildings are manufactured by a so-called industrial machine. In recent years, the processing accuracy required for these industrial products has become very high, and in order to satisfy such a requirement, it is a matter of course that the industrial machine itself is configured to realize high processing accuracy. In addition, it is necessary that machine parts constituting the industrial machine are also manufactured with high processing accuracy.

  Here, the machine which manufactures the machine parts which comprise machines, such as an industrial machine, is generally called a machine tool. A machine tool is a machine that processes a processed material into machine parts, and is also called a mother machine because it is a machine that makes a machine. As described above, in order to improve the processing accuracy of the final product, not only to improve the processing accuracy of the industrial machine used to manufacture the product, but also to manufacture machine parts constituting the industrial machine. There is a need to improve the processing accuracy of machine tools.

Japan Machine Tool Manufacturers Association: Machine Tool Design (Basic), Japan Machine Tool Manufacturers Association (1998) 90-91

  A machine tool has a large number of coupling parts (for example, bolt coupling parts fastened by bolts) because of the necessity for function, production, and transportation. Conventionally, it has been known that the presence of such a coupling part improves the damping capacity of the coupling structure coupled by the coupling part. Improving the damping capacity of the coupled structure means vibrations generated in machine tools (for example, vibrations associated with rotation of main shafts, bearings, gears, etc., various vibrations associated with machining, vibrations associated with linear motion of tables, etc.) This is effective in reducing the machining accuracy, and is useful for improving the machining accuracy of the machine tool. On the other hand, it is also known that the static rigidity of the joint portion generally decreases due to the presence of the joint portion, which leads to a decrease in machining accuracy of the machine tool.

  In this way, the presence of the coupling portion improves the damping capacity of the coupling structure, thereby contributing to improving the machining accuracy of the machine tool, while reducing the static rigidity of the coupling portion, thereby reducing the machining accuracy of the machine tool. It leads to lowering. Therefore, in order to improve the machining accuracy of the machine tool, it is necessary to achieve a good balance between not reducing the static rigidity and improving the damping capacity in the joint part, in other words, while maintaining the static rigidity of the joint part. Therefore, it is required to increase dynamic rigidity (see, for example, Non-Patent Document 1).

  As a result of intensive studies, the present inventors have found a method for increasing dynamic rigidity and damping capacity while maintaining or improving the static rigidity of the joint, and have experimentally verified this to arrive at the present invention. .

  An object of the present invention is to provide a method for increasing dynamic rigidity and damping capacity while maintaining or improving the static rigidity of a joint.

According to the present invention, a method for improving dynamic rigidity and damping capacity while maintaining or improving the static rigidity of a combined structure,
Fastening the first member having the first contact surface, the second member having the second contact surface, the elastic member disposed between the first member and the second member, and the first member and the second member Providing a coupling structure having a fastening member to be
Adjusting a tightening margin between the first member and the second member;
The elastic member is disposed between the first member and the second member, and is fastened using the fastening member so that the first contact surface and the second contact surface are in contact with each other with a predetermined coupling surface pressure. And
The tightening margin and the predetermined coupling surface pressure are adjusted so that the equivalent rigidity of the coupling portion is equal to or greater than that in the case where the elastic member is not interposed, and the equivalent viscous damping coefficient is increased. There is provided a method characterized in that

  In this case, the tightening allowance and the coupling surface pressure are adjusted so that the equivalent stiffness of the coupling portion is equal to or higher than that in the case where no elastic member is interposed, so that the static stiffness of the coupling portion is maintained or improved. Can be made. Furthermore, since the tightening allowance and the coupling surface pressure are adjusted so that the equivalent viscous damping coefficient of the coupling portion is increased as compared with the case where no elastic member is interposed, the dynamic rigidity and damping characteristics of the coupling portion are improved. Can do. Here, the tightening allowance corresponds to a gap when the first member and the second member are arranged without being tightened with an elastic member interposed therebetween. When the fastening member is tightened, the elastic member is elastically deformed by the amount of the fastening allowance. The elastic deformation force at this time contributes to lower the coupling surface pressure. Therefore, by adjusting the tightening allowance, the elastic deformation force, that is, the magnitude of the load supported by the elastic member can be adjusted, and the coupling surface pressure can be adjusted.

  In the method of the present invention, the first contact surface of the first member may be formed with a recess in which the elastic member is disposed, and the adjustment of the tightening margin is performed by adjusting the depth of the recess. May be made. In this case, by adjusting the depth of the concave portion in which the elastic member is disposed in advance, a desired coupling surface pressure can be obtained when fastened with a predetermined torque. Note that “adjusting the depth of the recess” means not only by adjusting the length from the opening to the bottom of the recess, but also by inserting an adjusting member of an arbitrary shape into the bottom of the recess. It also includes adjusting the depth of the recess.

  In the method of the present invention, the elastic member may be at least one disc spring. The elastic member may include a plurality of disc spring sets having a plurality of disc springs stacked so that the front and back are in the same direction. It may be stacked. In any case, the tightening allowance can be adjusted relatively easily by using a disc spring.

  In the method of the present invention, the fastening member may be a bolt or a clamp mechanism. The elastic member may be disposed adjacent to the bolt or the clamp mechanism, and may have a ring shape, a rod shape, or a plate shape. In this case, the freedom degree of selection of a fastening member can be raised. Furthermore, the freedom degree of selection of the shape of an elastic member and the freedom degree of arrangement | positioning can be raised.

  For example, when the fastening member is a bolt and the elastic member has a ring shape, an opening having a slightly larger diameter is simultaneously formed when forming a hole for inserting the bolt. Thereby, the opening part which inserts an elastic member of a ring shape easily can be formed.

  The vibration generated in the machine tool while maintaining or improving the static rigidity of the machine tool by utilizing the method for increasing the dynamic rigidity and damping capacity while maintaining or improving the static rigidity of the coupling portion according to the present invention. Therefore, the machining accuracy of the machine tool can be improved.

FIG. 1 is a schematic configuration diagram of a horizontal boring and milling machine 1. FIG. 2 is an explanatory diagram illustrating a model of a joint portion of a mechanical structure. FIG. 3 is a diagram illustrating the relationship between the coupling surface pressure and the contact rigidity, and the relationship between the coupling surface pressure and the damping. FIG. 4 is a schematic view of the bolt coupling structure 200. 5A is a schematic diagram of the disc spring 114, and FIG. 5B is a schematic diagram of a disc spring set in which the disc spring 114 is combined. FIG. 6 is a diagram showing a setup for an experiment for examining the relationship between the size of the tightening allowance and the load supported by the disc spring 114. FIG. 7 is a graph showing the relationship between the load supported by the disc spring 114 and the amount of elastic deformation of the disc spring 114. FIG. 8 is a diagram showing a setup for this verification experiment. FIG. 9 is a graph in which the equivalent stiffness k _eq obtained by measurement under the condition of constant fastening force is plotted for each fastening allowance. FIG. 10 is a graph in which the equivalent viscosity damping coefficient c _eq obtained by measurement under the condition of a constant tightening force is plotted for each tightening allowance. FIG. 11 is a graph in which the equivalent viscous damping coefficient obtained by the measurement under the condition where the coupling surface pressure is constant is plotted for each interference. FIG. 12 is a graph plotting the value of the equivalent viscous damping coefficient when the tightening force of the bolt 115 is changed when the disc spring 114 is not inserted. FIG. 13 is a flowchart for explaining a procedure of a method for improving damping capacity (dynamic rigidity) while maintaining static rigidity according to the present invention. FIG. 14 is a layout view of intervening elements according to another example of the present invention.

  A method for improving dynamic rigidity and damping capacity while maintaining or improving the static rigidity of the bonded structure according to the present invention will be described. The connection structure according to the method of the present invention is applied to a machine tool such as a horizontal boring mill 1 shown in FIG. Here, first, the structure of the horizontal boring mill 1 shown in FIG. 1 will be briefly described, and then the static rigidity of the coupling structure according to the present invention applied to the bolt coupling portion of the horizontal boring mill 1 will be described. A method for improving dynamic rigidity and damping capacity while maintaining or improving will be described. As shown in FIG. 1, the horizontal boring and milling machine 1 includes a table 10 on which a workpiece W as a workpiece is placed, and a saddle that is disposed below the table 10 and supports the table 10 so as to be movable in the Y-axis direction. 13, a table driving unit 15 that moves the table 10 with respect to the saddle 13 in the X-axis direction, a bed 20 that supports the saddle 13 so as to be movable in the Y-axis direction, and a saddle drive that moves the saddle 13 in the Y-axis direction A spindle having a portion 17, a column 40 disposed at one end in the Y direction of the bed 20 and standing in the Z direction, and a spindle 51 and a spindle motor 52 that rotates the spindle 51 around its axis (rotation axis). The head 50 and the spindle head drive unit 19 that moves the spindle head 50 in the Z direction along the column 40 are mainly provided. A tool holder to which a chuck portion such as a collet chuck is attached is attached to the tip of the main shaft 51, and a cutting tool 70 such as an end mill is fixed to the chuck portion of the holder.

  Here, the saddle driving unit 17 extends in the Y-axis direction, and is coupled to the first feed screw 17a inserted into the saddle 13 and one end of the first feed screw 17a, thereby connecting the first feed screw 17a. A first motor 17b that rotates. By driving the first motor 17b and rotating the first feed screw 17a, the saddle 13 into which the first feed screw 17a is inserted can be moved in the Y-axis direction. Similarly, the table drive unit 15 extends in the X-axis direction, and is coupled to the second feed screw 15a inserted into the table 10 and one end of the second feed screw 15a to connect the second feed screw 15a. And a second motor (not shown) that is driven to rotate. By driving the second motor to rotate the second feed screw 15a, the table 10 in which the second feed screw 15a is inserted can be moved in the X-axis direction. Further, the spindle head drive unit 19 extends in the Z-axis direction, and is coupled to a third feed screw 19a inserted into the spindle head 50 and one end of the third feed screw 19a to be connected to the third feed screw 19a. And a third motor (not shown) for rotationally driving the motor. By driving the third motor to rotate the third feed screw 19a, the spindle head 50 in which the third feed screw 19a is inserted can be moved in the Z-axis direction.

  The horizontal boring and milling machine 1 is provided with a table driving unit 15, a saddle driving unit 17, and a spindle head driving unit 19. The table 10 is rotated while rotating a cutting tool attached to the tip of the spindle 51 of the spindle head 50. The workpiece W fixed to the upper surface 10a can be independently moved in the X-axis direction, the Y-axis direction, and the Z-axis direction. In this way, the horizontal boring and milling machine 1 can cut the workpiece W by bringing the rotating cutting tool into contact with a desired position of the workpiece W.

  When vibration is generated in the horizontal boring and milling machine 1 when cutting the workpiece W, the machining accuracy of the workpiece W is reduced due to this. Here, in general, in a machine tool such as the horizontal boring and milling machine 1, it is conceivable that vibration is generated by a force caused by machining, a force caused by the machine, and a force caused by factors other than the machine. Examples of the force resulting from machining include forced vibration external force and self-excited vibration that are generated during intermittent cutting in milling and when turning an asymmetrical workpiece. Examples of the force caused by the machine include unbalance caused by a rotating element such as a main shaft, gear meshing vibration, bearing rolling vibration, and reversing impact force of a table. The force caused by factors other than the machine includes unbalanced vibration due to poor mounting accuracy of tools and workpieces, vibration transmitted from the floor, and the like.

  As shown in FIG. 2, a coupling portion in a machine structure such as a machine tool can be modeled by a combination of a damper element having a damping coefficient C and a spring element having a spring constant k. Here, the spring constant k is a parameter characterizing the contact rigidity, and the damping coefficient C is a parameter characterizing the damping characteristic. Since each coupling part is characterized by a damper element, it can be seen that the damping characteristics are improved when the number of coupling parts such as bolt coupling parts fastened by bolts is increased. When the damping characteristic is improved, the vibration generated in the machine tool can be effectively damped, so that the machining accuracy of the machine tool can be improved. Therefore, it can be said that increasing the number of coupling portions is preferable from the viewpoint of improving the machining accuracy by improving the damping capability of the machine tool. However, if there is a coupling portion, the static rigidity is inevitably lowered as compared with a case where the coupling portion is formed integrally without the coupling portion. On the contrary, this becomes a factor of reducing the machining accuracy of the machine tool.

  In the machine tool such as the horizontal boring and milling machine 1, it is essential to provide a plurality of coupling portions for functional, manufacturing, and transportation reasons. In other words, since it is practically impossible to reduce the number of coupling parts to zero, on the assumption that there are a plurality of coupling parts, in order to improve damping capacity while maintaining static rigidity in each coupling part New design approaches have been desired.

  Therefore, the present inventors have made extensive studies and further proceeded from the conventionally desired “new design method for improving damping capacity while maintaining static rigidity in the joint portion”. The inventors have found a “new design method for improving the dynamic rigidity and damping capacity while maintaining or improving the rigidity” and experimentally confirming this, thereby reaching the present invention. Hereinafter, a new method for improving the dynamic rigidity and damping capacity while maintaining or improving the static rigidity of the bonded structure, which has been found by the present inventors, will be described.

  FIG. 3 shows the relationship between the coupling surface pressure and the contact rigidity, and the relationship between the coupling surface pressure and the damping. The horizontal axis in FIG. 3 represents the magnitude of contact stiffness, and the left vertical axis and the right vertical axis represent the contact stiffness and the magnitude of attenuation, respectively. As shown in FIG. 3, the contact rigidity is substantially constant in a range of a certain bonding surface pressure or more. In contrast, the attenuation peaks at a certain bonding surface pressure. This is because a minute slip is likely to occur on the coupling surface at a coupling surface pressure near the coupling surface pressure at which the attenuation reaches a peak (hereinafter referred to as the first coupling surface pressure), thereby improving the damping capacity. It is understood that there is. Here, if the magnitude | size of a coupling surface pressure can be adjusted so that attenuation | damping may become large in the range which can maintain contact rigidity, we can improve damping capacity, maintaining contact rigidity. I thought that. Note that if the contact rigidity can be maintained, it is possible to suppress a decrease in the static rigidity of the combined structure, and thus it is not possible to improve the dynamic rigidity and the damping capacity while maintaining the static rigidity of the combined structure. I thought. Therefore, the present inventors conducted the following verification experiment in order to verify this.

  As shown in FIG. 4, it has a columnar base 110 and two columnar connecting portions 111 arranged at both ends in the central axis direction of the base 110, and the base 110 and the connecting portions 111 are two pieces. A columnar bolt coupling structure 200 fastened by a bolt 115 was prepared. Screw holes 110b are formed in the contact surfaces 110a that contact the connection portions 111 at both ends in the central axis direction of the base portion 110, respectively. In addition, each connection portion 111 is formed with a through hole 112 penetrating in the central axis direction, and the diameter of the through hole 112 of each connection portion 111 is partially increased on the contact surface 111 a that contacts the base portion 110. Thus, a circular opening 113 is formed. In the opening 113, intervening elements composed of 12 disc springs 114 are inserted. The two connecting portions 111 and the base portion 110 are fastened by two bolts 115 inserted through the through hole 112 and the disc spring 114 of the connecting portion 111.

  The disc spring is a disc-shaped spring in which a ring having a hole in the center of a disk is formed into a conical shape. The disc spring 114 used in this verification experiment is a ring-shaped plate material having a plate pressure of 1.5 mm and an outer diameter of 25 mm. A through hole having a diameter of 12.2 mm is formed in the central portion of the disc spring 114, and a bolt 115 is inserted into the through hole. As described above, the disc spring 114 is not a flat plate, but is formed in a conical shape so that the inner peripheral side is 0.55 mm higher than the outer peripheral side as shown in FIG. Therefore, the height when the disc spring 114 is placed on a flat surface is 2.05 mm. This height is called the effective height. In the following description, for the sake of convenience, the surface facing upward when the inner peripheral side of the disc spring 114 is placed high will be referred to as the front surface 114a, and the surface facing downward will be referred to as the back surface 114b.

  In this verification experiment, as shown in FIG. 5B, a set of three disc springs 114 are overlapped in parallel so that the front surface 114a and the back surface 114b overlap. Then, the four sets of disc springs configured in this way are overlapped in opposite directions so that the front surfaces 114a and the back surfaces 114a overlap. The effective height of the set of 12 disc springs 114 stacked in this manner is 20.2 mm.

  The depth of the opening 113 is formed to be shallower than the effective height of the set of twelve disc springs 114 interposed between the base 110 and the connecting portion 111. That is, when the bolt 115 is not tightened, the depth of the opening 113 is adjusted so that a gap G is formed between the base 110 and the connecting portion 111 as shown in FIG. Here, as the bolt 115 is tightened, the twelve disc springs 114 are elastically deformed until the gap G disappears. While the gap G exists, the contact surface 110a of the base portion 110 and the contact surface 111a of the connection portion 111 are not in contact with each other, and therefore the coupling surface pressure therebetween is zero. When the gap G disappears and the contact surface 110a of the base portion 110 and the contact surface 111a of the connection portion 111 contact each other, the coupling surface pressure between the contact surfaces 110a and 111a is caused by the tightening force applied by the bolt 115. To increase. In the following description, the gap G between the base portion 110 and the connection portion 111 when the bolt 115 is not tightened is also referred to as a tightening allowance.

  Here, a case where the bolt 115 is tightened with a predetermined torque is considered. When the pair of disc springs 114 is not interposed between the base part 110 and the connection part 111, the tightening force of the bolt 115 directly contributes to an increase in the coupling surface pressure between the contact surfaces 110a and 111a. Will do. However, when a set of disc springs 114 is interposed between the base portion 110 and the connecting portion 111, a part of the tightening force of the bolt 115 is required to elastically deform the set of disc springs 114. Therefore, not all of the tightening force of the bolt 115 contributes to an increase in the coupling surface pressure between the contact surfaces 110a and 111a. In other words, the set of disc springs 114 that are elastically deformed so as to be compressed presses the base 110 and the connecting portion 111 in directions away from each other, and thus acts in a direction that weakens the tightening force of the bolt 115. That is, the coupling surface pressure between the contact surfaces 110a and 111a is reduced by the amount of the load supported by the pair of disc springs 114 as compared with the case where the set of disc springs 114 is not interposed.

  As described above, the size of the tightening allowance is equal to the amount of elastic deformation of the disc spring 114 when the base portion 110 and the connecting portion 111 abut (hereinafter simply referred to as the amount of elastic deformation of the disc spring 114). Therefore, the elastic deformation amount of the disc spring 114 can be adjusted by adjusting the depth of the opening 113. That is, if the opening 113 is deepened, the size of the tightening margin can be reduced, and the elastic deformation amount of the disc spring 114 can be reduced. At this time, since the elastically deformed disc spring 114 presses the base portion 110 and the connecting portion 111 away from each other in a direction away from each other, the contact surfaces 110a and 111a when the bolt 115 is tightened with a predetermined torque are reduced. The bonding surface pressure between the two can be increased. Conversely, if the depth of the opening 113 is reduced, the amount of elastic deformation of the disc spring 114 can be increased. At this time, since the elastically deformed disc spring 114 presses the base portion 110 and the connection portion 111 in directions away from each other, the contact surfaces 110a and 111a when the bolt 115 is tightened with a predetermined torque are increased. The bonding surface pressure between the two can be reduced. Thus, by adjusting the depth of the opening 113, the magnitude of the coupling surface pressure between the contact surfaces 110a and 111a when the bolt 115 is tightened with a predetermined torque can be adjusted. . In this specification, the phrase “adjusting the depth of the opening 113” is not limited to adjusting the length from the opening of the opening 113 to the bottom of the hole. It is also included to insert an adjusting member (not shown). The shape of the adjusting member is not particularly limited, and a member having an arbitrary shape can be used as necessary. For example, a ring-shaped plate material (such as a washer) in which a through-hole through which the bolt 115 can be inserted is formed at the center may be disposed at the bottom of the opening 113. Thus, by arranging the adjustment member at the hole bottom of the opening, the same effect as that of adjusting the length from the opening of the opening 113 to the hole bottom can be obtained.

  Here, prior to this verification experiment, the inventors examined the relationship between the size of the tightening margin (that is, the amount of elastic deformation of the disc spring 114) and the load supported by the disc spring 114, as shown in FIG. The piezoelectric load cell 130 was inserted between the connecting portion 111 and the bolt 115, and the relationship between the magnitude of the load applied to the piezoelectric load cell 130 by the bolt 115 and the size of the fastening allowance was measured. The size of the tightening allowance was obtained by measuring the displacement amount of the connecting portion 111 when the bolt 115 was tightened with the electric micrometer 131. Specifically, connecting portions 111 having openings 113 with various depths are prepared, and the displacement amount of the connecting portion 111 when the bolt 115 is tightened with a predetermined torque for each connecting portion 111, and at that time The magnitude of the load applied to the piezoelectric load cell 130 was measured. Here, the difference from the magnitude of the load applied to the piezoelectric load cell 130 when the disc spring 114 is not interposed corresponds to the load supported by the disc spring 114. As shown in FIG. 7, it was found that the load supported by the disc spring 114 and the elastic deformation amount of the disc spring 114 have a linear relationship.

  Next, a verification experiment conducted by the present inventors will be described. As shown in FIG. 8, the base 110 and the connecting portion 111 are fastened with bolts 115 with a set of disc springs 114 interposed therebetween, thereby forming a cylindrical bolt coupling structure 200. An acceleration pickup 211 connected to the FFT analyzer 210 was attached to the bolt coupling structure 200, and the bolt coupling structure 200 was struck by an impulse hammer 212 to vibrate. The impulse excitation force and the acceleration response at that time were taken into the FFT analyzer 210 to obtain a transfer function.

In this verification experiment, focusing on the primary mode with the largest vibration amplitude, the modal parameters were calculated as follows. First, the natural frequency f _n (= ω _n / 2π) was calculated from the co-quad diagram of the transfer function. Then, the attenuation waveform of only the first-order mode component was extracted from the attenuation waveform by bandpass filtering, and the attenuation ratio ζ was calculated using the transient response method. Furthermore, the compliance was obtained from the Bode diagram obtained from the experiment, the peak error was corrected by the least square method using the natural frequency f _n and the damping ratio ζ, and the dynamic stiffness K _d was calculated by taking the reciprocal thereof. .

Here, in the one-degree-of-freedom model, the natural angular frequency ω _n , the damping ratio ζ, and the dynamic stiffness K _d are obtained by using an equivalent mass m _eq , an equivalent viscous damping coefficient c _eq , and an equivalent stiffness k _eq that are physical parameters, Each can be expressed as the following Formulas 1-3.

By using these relational expressions, an equivalent mass m _eq , an equivalent viscous damping coefficient c _eq , and an equivalent stiffness k _eq as physical parameters were identified from three modal parameters obtained by measurement.

First, the tightening force of the bolt 115 is adjusted to 9 kN, and the tightening margin is zero (that is, the disc spring 114 is not interposed), and the tightening margin is 60.9 μm, 255.7 μm, 435. For the case of 5 μm, the measurement as described above was performed. FIG. 9 is a graph in which the obtained equivalent stiffness k _eq is plotted for each tightening allowance, and FIG. 10 is a graph in which the obtained equivalent viscous damping coefficient c _eq is plotted for each tightening allowance.

  From FIG. 9, it can be seen that there is not much change in the equivalent rigidity at any tightening allowance. From this, it can be understood that the incorporation of the disc spring 114 does not significantly affect the static rigidity of the bolt coupling structure 200. From FIG. 10, the tightening margin of the disc spring 114 is increased, that is, the load supported by the disc spring 114 is increased, so that the coupling surface pressure between the contact surfaces 110a and 111a is decreased to reduce the damping. It can be seen that increases. From this, it can be seen that by interposing the disc spring 114, the coupling surface pressure between the contact surfaces 110a and 111a is appropriately adjusted, and the damping capacity is improved.

  Next, the same measurement was performed in a state where the coupling surface pressure between the contact surfaces 110a and 111a was adjusted to 6.2 MPa. The coupling surface pressure (6.2 MPa) in this measurement is the coupling surface between the contact surfaces 110a and 111a when the tightening force of the bolt 115 is set to 9 kN when the disc spring 114 is not interposed. It is almost the same as pressure. FIG. 11 is a graph in which the obtained equivalent viscosity damping coefficient is plotted for each interference. From FIG. 11, it can be seen that the attenuation is higher when the disc spring 114 is inserted than when the disc spring 114 is not inserted. In this measurement, the coupling surface pressure is adjusted to be constant. Nevertheless, the difference between the case where the disc spring 114 is inserted and the case where the disc spring 114 is not inserted is that the damping performance is increased due to the insertion of the disc spring 114. Conceivable. Further, it can be seen from FIG. 11 that the attenuation is different when the interference is different. In this measurement, it was found that the attenuation was the highest when the tightening allowance of the disc spring 114 was 255.7 μm, and the attenuation decreased when the tightening allowance was 435.5 μm. This is considered to indicate that if the load applied to the disc spring 114 is too large, the damping property of the disc spring 114 is hardly exhibited.

  Table 1 shows the effect of attenuation when the coupling surface pressure between the contact surfaces 110a and 111a is adjusted so that the tightening force of the bolt 115 is constant, and when the coupling surface pressure is adjusted to be constant. It is for the comparison of the effect of attenuation in. The value of “damping coefficient” in Table 1 is the value of the equivalent viscous damping coefficient obtained when the disc spring 114 is not inserted from the value of the equivalent viscous damping coefficient obtained when the disc spring 114 is inserted. The value is subtracted. Here, as described above, when the coupling surface pressure is adjusted to be constant, the increase from the case where the disc spring 114 is not inserted is an improvement in the attenuation due to the disc spring 114 being inserted. It is thought to be due to. On the other hand, when the tightening force of the bolt 115 is adjusted to be constant, the increase from the case where the disc spring 114 is not inserted is combined with the effect of the disc spring 114 being inserted, It is considered that both of the effects due to the reduction of the contact pressure are included.

  Here, the column of “deformation of the disc spring” in Table 1 shows the elastic deformation force of the disc spring 114 at each tightening allowance. That is, the tightening force of the bolt 115 is weakened by the amount that the disc spring 114 is elastically deformed. Here, FIG. 12 is a graph plotting the value of the equivalent viscous damping coefficient when the tightening force of the bolt 115 is changed when the disc spring 114 is not inserted. From FIG. 12, it can be seen that when the tightening force is weakened, that is, when the coupling surface pressure is lowered, the equivalent viscous damping coefficient increases accordingly.

  As described above, when the adjustment is made so that the tightening force of the bolt 115 is constant, both the effect of inserting the disc spring 114 and the effect of reducing the coupling surface pressure are included. it is conceivable that. On the other hand, when the coupling surface pressure is adjusted to be constant, it is considered that only the effect of inserting the disc spring 114 is included. From this, the ratio of the damping effect due to the disc spring 114 to the damping effect when the bolt 115 was adjusted to be constant was calculated (see “Dampening due to the disc spring” in Table 1). Percentage "). According to this, when the tightening margin is 60.9 μm, since the tightening margin is small, the damping effect of the disc spring does not appear remarkably, and the ratio of the damping effect due to the disc spring is low. On the other hand, when the tightening margin is 255.7 μm, the damping effect due to the disc spring is high, and the load applied to the coupling surface at this time is 7.75 kN. It can be seen that the attenuation of the coupling surface does not change much. Therefore, the ratio of the damping effect due to the disc spring is increased. When the tightening margin is 435.5 μm, the load applied to the coupling surface is 6.75 kN, and according to FIG. 12, the attenuation of the coupling surface is greatly increased. For this reason, the ratio of the damping effect due to the disc spring is reduced compared to the case where the tightening margin is 255.7 μm.

  In this way, the disc spring is applied within the range where the static rigidity of the coupling surface can be maintained, and the load supported by the disc spring is adjusted so that the attenuation caused by the disc spring is maximized, while maintaining the static stiffness. It has been found that damping capacity and dynamic rigidity can be improved. Further, according to the knowledge of the inventors, it is considered that the static rigidity of the coupling portion can be increased by using an intervening element such as a disc spring having high damping property and rigidity. That is, according to the method of the present invention, it is possible not only to improve the damping capacity and the dynamic rigidity while maintaining the static rigidity, but also to improve the damping capacity and the dynamic rigidity while increasing the static rigidity. It becomes possible.

  To summarize the above, as shown in the flowchart of FIG. 13, the tightening margin is adjusted so that the intervening elements such as the disc springs can sufficiently exhibit the damping (S101), and the interposing elements such as the disc springs are arranged on the coupling surface ( S102) By tightening the bolt so as to have a predetermined coupling surface pressure (S103), it is possible to improve the damping capacity and the dynamic rigidity while maintaining or increasing the static rigidity of the coupling portion. More specifically, the tightening margin and the coupling surface pressure are adjusted so that the above-described equivalent rigidity is equal to or greater than that in the case where no disc spring is disposed and the equivalent viscosity damping coefficient is increased. be able to. By applying this method to a machine tool such as the horizontal boring and milling machine 1, vibrations generated in the machine tool can be suppressed while maintaining or improving the static rigidity of the machine tool. Therefore, the processing accuracy of the machine tool can be improved.

  In the above description, a combination of 12 disc springs is used as the intervening element, but the present invention is not limited to this. If necessary, a desired number of disc springs may be combined. Moreover, although the magnitude | size of the joint surface pressure was adjusted by adjusting the depth of an opening part, with the number of disk springs made constant, this invention is not limited to this. For example, instead of adjusting the depth of the opening, or in addition to adjusting the depth of the opening, by adjusting the number, material, size, thickness, shape, etc. of the disc spring You may adjust the magnitude | size of a joint surface pressure. In the above description, the opening portion is provided in the connection portion. However, in addition to or instead of this, the opening portion may be provided in the base portion. When adjusting the tightening allowance, the depth of the opening, the number of disc springs, etc. may be adjusted so that an appropriate coupling surface pressure can be obtained simply by tightening the bolt with a predetermined torque. desirable.

  In addition, as an interposition element, it is not restricted to a disc spring, For example, other elastic deformation bodies, such as hard rubber and a metal ring, can be used. Moreover, a liquid substance can also be used as an intervening element. Further, in the above-described verification experiment, an intervening element such as a disc spring is inserted so as to surround the bolt. However, the present invention is not limited to this, and the intervening element is disposed at an arbitrary position on the coupling surface as necessary. Can be arranged. For example, as shown in FIG. 14, rod-shaped hard rubber interposing elements 314 may be arranged in parallel to the rows of bolts 315. Further, the shape of the intervening element is not limited to the ring shape or the rod shape, and any shape can be used. For example, instead of the rod-shaped interposition element 314 shown in FIG. 14, a plate-shaped interposition element may be used.

  In the above description, as an example of the coupling portion in the mechanical structure, the bolt coupling portion fastened by the bolt has been described as an example. However, the present invention is not limited to this, and can be applied to any coupling mechanism. Can do. For example, an arbitrary clamping mechanism can be used instead of or in addition to the bolt. In addition, also when using a clamp mechanism instead of a volt | bolt, interposition elements, such as a disc spring 114 and the interposition element 314, as mentioned above can be used similarly.

  In the above description, the method for improving the damping capacity and the dynamic rigidity while maintaining or improving the static rigidity according to the present invention will be described as an example applied to a machine tool such as the horizontal boring milling machine 1. However, the present invention is not limited to this, and can be applied to a connecting portion of any machine.

  Finally, conventionally, an elastic material such as rubber has been sandwiched so as to cover the entire coupling surface for the purpose of simply improving the damping capacity. In this case, although the damping capacity can be improved, the bonding surface pressure of the bonding surface is remarkably lowered, and the static rigidity cannot be maintained. In addition, a sealing member such as a so-called O-ring may be sandwiched between the coupling surfaces for the purpose of maintaining airtightness. In this case, since the purpose is to ensure airtightness at the bonding surface, there is no intention to lower the bonding surface pressure applied to the bonding surface so as to improve the damping capacity as in the present invention. It was adjusted to increase the surface pressure as much as possible. In any case, the point that the elastic member is sandwiched between the coupling surfaces is consistent with the method for improving the damping capacity and the dynamic rigidity while maintaining or improving the static rigidity according to the present invention. However, it should be noted that in any case, as in the present invention, there is no intention of lowering the bonding surface pressure applied to the bonding surface so as to improve the damping capacity.

  By applying the method for improving damping capacity and dynamic rigidity to a machine tool while maintaining or improving the static rigidity according to the present invention, machining accuracy is improved and machine parts with small errors can be manufactured. It can use for manufacture.

DESCRIPTION OF SYMBOLS 1 Side boring milling machine 110 Base part 111 Connection part 114 Belleville spring 130 Piezoelectric load cell 131 Electric micrometer

Claims (5)

A method of improving dynamic rigidity and damping capacity while maintaining or improving the static rigidity of a coupled structure,
Fastening the first member having the first contact surface, the second member having the second contact surface, the elastic member disposed between the first member and the second member, and the first member and the second member Providing a coupling structure having a fastening member to be
Adjusting a tightening margin between the first member and the second member;
The elastic member is disposed between the first member and the second member, and is fastened using the fastening member so that the first contact surface and the second contact surface are in contact with each other with a predetermined coupling surface pressure. And
The tightening margin and the predetermined coupling surface pressure are adjusted so that the equivalent rigidity of the coupling portion is equal to or greater than that in the case where the elastic member is not interposed, and the equivalent viscous damping coefficient is increased. A method characterized by being. The first contact surface of the first member is formed with a recess for arranging the elastic member,
The method according to claim 1, wherein the tightening margin is adjusted by adjusting a depth of the recess.   The method according to claim 1, wherein the elastic member is at least one disc spring.   The elastic member includes a plurality of disc spring sets having a plurality of disc springs stacked so that the front and back are in the same direction, and the plurality of disc spring sets are stacked so that the front and back are reversed. The method according to claim 1 or 2, characterized in that: The fastening member is a bolt or a clamp mechanism,
The method according to claim 1, wherein the elastic member is disposed adjacent to the bolt or the clamp mechanism and has a ring shape, a rod shape, or a plate shape.

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