Friction coefficient measuring device, friction coefficient measuring method

Abstract

To provide a friction coefficient measuring device and friction coefficient measuring method that can measure the friction coefficient during workpiece molding. [Solution] The friction coefficient measuring device 1 comprises a pair of dies 10 that support a workpiece, a punch 20 that shapes the workpiece by inserting and removing it in the Z-axis direction into the gap S1 between the pair of dies 10, a first sensor 30 that measures the Z-axis direction load applied to the punch 20, a slider 40 that supports each of the pair of dies 10 so as to be slidable in the X-axis direction opposite to each other, a pair of fixed walls 50 arranged on the outside of the pair of dies 10, a second sensor 60 arranged between the pair of fixed walls 50 and the pair of dies 10 and measures the X-axis direction load applied to the pair of dies 10, and a calculation unit 70 that calculates the friction coefficient of the workpiece based on the measurement results of the first sensor 30 and the second sensor 60.

Description

Technical Field

[0001] The present invention relates to a friction coefficient measuring device and a friction coefficient measuring method.

Background Art

[0002] The following Patent Document 1 discloses a press die that continuously performs piercing and flanging on a metal plate. This press die is characterized in that an inner wall surface having a dynamic friction coefficient of 0.15 or less with respect to the metal plate is provided in a shaft hole for discharging the piercing scrap of the flanging punch.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, during press forming such as the above flanging process, since the workpiece (metal plate) is deformed while being squeezed, in order to improve the simulation accuracy of the forming, it is necessary to measure the friction coefficient (dynamic friction coefficient and static friction coefficient) during workpiece forming. In the above prior art, the friction coefficient of the workpiece is measured with a Boudouard friction coefficient measuring device (see paragraph

[0006] ). As is well known, the Boudouard friction coefficient measuring device measures the friction coefficient by setting the workpiece on a testing machine and sliding it horizontally in a straight line back and forth, and it does not measure the friction coefficient during workpiece forming.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a friction coefficient measuring device and a friction coefficient measuring method capable of measuring the friction coefficient during workpiece forming.

Means for Solving the Problems

[0006] (1) A friction coefficient measuring device according to one aspect of the present invention comprises: a pair of dies that face each other with a gap between them and support a workpiece; a punch that shapes the workpiece by being inserted into and removed in a first direction from the gap between the pair of dies; a first sensor that measures the load applied to the punch in the first direction; a slider that supports each of the pair of dies so as to be slidable in a second direction opposite to each other; a pair of fixed walls arranged on the outside of the pair of dies; a second sensor arranged between the pair of fixed walls and the pair of dies and measuring the load applied to the pair of dies in the second direction; and a calculation unit that calculates the friction coefficient of the workpiece based on the measurement results of the first sensor and the second sensor.

[0007] (2): In the friction coefficient measuring device according to (1), the calculation unit may calculate the dynamic friction coefficient of the workpiece based on the measurement results of the first sensor and the second sensor, measured between the time the punch deforms the workpiece and the time it is withdrawn from the gap between the pair of dies.

[0008] (3) A friction coefficient measuring device according to (1) or (2) may include a plate that moves in the first direction together with the punch, and a pair of restricting walls that are perpendicularly mounted from the plate in the first direction and restrict the outward tilt of the pair of fixed walls in the second direction.

[0009] (4): In the friction coefficient measuring device according to (3), the pair of restricting walls may be formed in the range including the punch in the first direction.

[0010] (5) In the friction coefficient measuring device according to (3) or (4), the pair of restricting walls may be formed in the first direction in a range including the second sensor when the punch deforms the workpiece.

[0011] (6): A friction coefficient measurement method according to one aspect of the present invention comprises: a friction force measurement step of measuring a first load applied to a punch during the process of forming a workpiece as a friction force; a normal force measurement step of measuring a second load applied to a pair of dies that support the workpiece and form a gap into which the punch can be inserted, which attempts to widen the gap, as a normal force; and a friction coefficient calculation step of calculating the friction coefficient of the workpiece based on the friction force and the normal force.

[0012] (7): In the friction coefficient measurement method relating to (6), the friction coefficient calculation step may calculate the dynamic friction coefficient of the workpiece based on the friction force and the normal force measured between the time the punch deforms the workpiece and the time it is withdrawn from the gap between the pair of dies. [Effects of the Invention]

[0013] According to one aspect of the present invention described above, a friction coefficient measuring device and a friction coefficient measuring method capable of measuring the friction coefficient during workpiece molding can be provided. [Brief explanation of the drawing]

[0014] [Figure 1] This is a front view showing a friction coefficient measuring device according to one embodiment. [Figure 2] Figure 1 is a front view showing a friction coefficient measuring device when the punch shown is raised. [Figure 3] This is a perspective view showing a friction coefficient measuring device according to one embodiment. [Figure 4] A front view showing a workpiece according to one embodiment. [Figure 5] This is a perspective view showing a workpiece according to one embodiment. [Figure 6] This is an explanatory diagram illustrating how to determine the coefficient of dynamic friction during the downward stroke of a punch while the thickness of the workpiece is decreasing, according to one embodiment. [Figure 7] This is an explanatory diagram illustrating how to determine the coefficient of dynamic friction after the thickness of the workpiece decreases during the downward stroke of a punch according to one embodiment. [Figure 8]It is an explanatory diagram for explaining a method for obtaining the coefficient of kinetic friction of a workpiece during the upward stroke of a punch according to an embodiment.

Embodiment for Carrying Out the Invention

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] FIG. 1 is a front view showing a friction coefficient measuring device 1 according to an embodiment. FIG. 2 is a front view showing the friction coefficient measuring device 1 when the punch 20 shown in FIG. 1 is raised. As shown in FIG. 1, the friction coefficient measuring device 1 includes a pair of dies 10, a punch 20, a first sensor 30, a slider 40, a pair of fixed walls 50, a second sensor 60, and a calculation unit 70.

[0017] The pair of dies 10 are opposed to each other with a gap S1 therebetween. In the following description, an XYZ orthogonal coordinate system may be set, and the positional relationship of each member may be described while referring to this XYZ orthogonal coordinate system. The X-axis direction is the first horizontal direction in which the pair of dies 10 face each other, the Y-axis direction is the second horizontal direction orthogonal to the first horizontal direction, and the Z-axis direction is the vertical direction. In the present embodiment, for convenience of explanation, the Z-axis direction is made to coincide with the vertical direction, but the Z-axis direction does not have to coincide with the vertical direction. Similarly, the X-axis direction and the Y-axis direction do not have to coincide with the horizontal direction.

[0018] The pair of dies 10 are formed in a substantially L shape when viewed from the front. A workpiece support portion 11 for supporting the workpiece is attached to the upper surface of the die 10. Although not shown, the die 10 and the workpiece support portion 11 can be provided with a mechanism for preventing the inflow of the workpiece 100 during molding. The punch 20 forms the workpiece by being inserted into and removed from the gap S1 between the pair of dies 10 in the Z-axis direction (the first direction).

[0019] The first sensor 30 measures the load applied to the punch 20 in the Z-axis direction. While a load cell can be an example of the first sensor 30, it is not limited to a load cell; any sensor capable of measuring the load applied to the punch 20 in the Z-axis direction is acceptable. The slider 40 supports each of the pair of dies 10 so that they can slide in the X-axis direction (second direction) opposite to each other.

[0020] The slider 40 comprises a rail 41 extending in the X-axis direction and a slider block 42 that moves in the X-axis direction along the rail 41. The rail 41 is fixed to the base 2, which is the bottom plate of the friction coefficient measuring device 1. The slider block 42 is engaged with the rail 41 via rolling elements such as balls.

[0021] A die mounting portion 43 for attaching the die 10 is provided on the upper surface of the slider block 42. The slider blocks 42 are provided in pairs, corresponding to a pair of dies 10. In other words, two slider blocks 42 engage with one rail 41. If the accuracy of the movement of the two slider blocks 42 in the X-axis direction can be ensured, the rail 41 may be divided into two or more sections, and a slider block 42 may be provided on each rail 41.

[0022] The pair of fixed walls 50 are positioned outside the pair of dies 10 in the X-axis direction. The pair of fixed walls 50 are erected in the Z-axis direction relative to the base 2 and extend above the pair of dies 10. The pair of dies 10 and the slider 40 are positioned inside the pair of fixed walls 50.

[0023] The second sensor 60 is positioned between the pair of fixed walls 50 and the pair of dies 10. The second sensor 60 measures the load applied to the pair of dies 10 in the X-axis direction. A load cell can be an example of the second sensor 60, but it is not limited to a load cell as long as it is a sensor capable of measuring the load applied to the pair of dies 10 in the X-axis direction.

[0024] The second sensor 60 is attached to a sensor mounting portion 51 provided on the inward-facing surface of a pair of fixed walls 50. Multiple second sensors 60 (two in this embodiment) are mounted on the sensor mounting portion 51 at intervals in the Z-axis direction. Note that there may be only one second sensor 60. Incidentally, having multiple second sensors 60 allows for the calculation of the sum of the loads applied to the pair of dies 10 in the X-axis direction, thereby enabling the calculation of a larger coefficient of friction. Furthermore, it is possible to determine whether the measured values ​​of each sensor are normal or abnormal.

[0025] As shown in Figure 2, the punch 20 is attached to the underside of the plate 21. The plate 21 is connected to a lifting device (not shown) and moves in the Z-axis direction together with the punch 20. A pair of restricting walls 22 are vertically installed at both ends of the plate 21 in the X-axis direction to restrict the outward tilting of the pair of fixed walls 50 in the X-axis direction.

[0026] A pair of restricting walls 22 are positioned on the outside of the pair of fixed walls 50 in the X-axis direction. The thickness of the restricting walls 22 in the X-axis direction is greater than that of the fixed walls 50, and they are block-shaped. The pair of restricting walls 22 slide against the outward-facing surfaces of the pair of fixed walls 50 in the X-axis direction. As shown in Figure 1, when the punch 20 descends and a load is applied that attempts to widen the gap S1 between the pair of dies 10, the pair of restricting walls 22 restrict the outward tilting of the pair of fixed walls 50 in the X-axis direction.

[0027] Specifically, the pair of fixed walls 50 attempt to deform such that their upper ends bend significantly outward in the X-axis direction, centered on the base 2 side. At this time, the pair of restricting walls 22 support the upper ends of the pair of fixed walls 50 at the base on the plate 21 side, where the bending is less, thereby restricting the tilting of the pair of fixed walls 50. As a result, fluctuations in the gap between the die 10 and the fixed walls 50 are suppressed, and the measurement value of the second sensor 60 becomes normal.

[0028] Figure 3 is a perspective view showing a friction coefficient measuring device 1 according to one embodiment. As shown in Figure 3, slide plates 52 are attached to the outward-facing surfaces of a pair of fixed walls 50. The slide plates 52 are, for example, oil-free slide plates, and a plurality of solid lubricants 52a are embedded in the sliding surface facing the regulating wall 22.

[0029] Shafts 3 are erected at the four corners of the base 2. Bushings 4 are attached to the four corners of the plate 21, which engage with the shafts 3 so as to be movable in the Z-axis direction. As a result, the plate 21 is guided in the Z-axis direction relative to the base 2.

[0030] Returning to Figure 1, the pair of restricting walls 22 extend downward from the punch 20 in the Z-axis direction. In other words, the pair of restricting walls 22 are formed in a first range A1 that includes the punch 20 in the Z-axis direction. The first range A1 is the range in which the punch 20 is inserted into the gap S1 between the pair of dies 10, and is also called the workpiece forming range.

[0031] Furthermore, the pair of restricting walls 22 are formed in a second range A2 including the second sensor 60 in the Z-axis direction when the punch 20 is in a lowered state (when the punch 20 deforms the workpiece). The second range A2 is the range in which the pair of restricting walls 22 maintain a constant gap between the die 10 and the fixed wall 50, and is also called the installation range of the second sensor 60.

[0032] Figure 4 is a front view showing a workpiece 100 according to one embodiment. Figure 5 is a perspective view showing a workpiece 100 according to one embodiment. As shown in these figures, the workpiece 100 is, for example, a metal plate bent into an L-shape that forms a curved portion 101 before measuring the coefficient of friction, and is attached to the die 10 shown in Figure 1. Since the workpiece 100 undergoes only deformation in which the thickness of the plate decreases due to shaping by the punch 20, it becomes a desirable shape for accurate measurement. Note that the workpiece 100 is not limited to this metal plate.

[0033] The calculation unit 70 shown in Figure 1 calculates the friction coefficient of the workpiece 100 based on the measurement results of the first sensor 30 and the second sensor 60. The calculation unit 70 is a calculation device that calculates the friction coefficient of the workpiece 100 according to a pre-stored program, and is equipped with input / output interfaces connected to the first sensor 30 and the second sensor 60, a display for displaying the calculation result of the friction coefficient, and the like.

[0034] The calculation unit 70 calculates the coefficient of friction (dynamic friction coefficient and static friction coefficient) of the workpiece 100 during molding. For example, when the measured value (frictional force) of the first sensor 30 is F and the measured value (normal force) of the second sensor 60 is N, the coefficient of friction μ of the workpiece 100 can be calculated using the following formula (1). μ = F / N …(1)

[0035] Figure 6 is an explanatory diagram illustrating how to determine the coefficient of dynamic friction of the workpiece 100 while its thickness is decreasing during the downward stroke of the punch 20 according to one embodiment. Figure 7 is an explanatory diagram illustrating how to determine the coefficient of dynamic friction of the workpiece 100 after its thickness has decreased during the downward stroke of the punch 20 according to one embodiment. Note that the reference numeral M1 indicates the direction of the downward movement of the punch. As shown in Figure 6, during the downward stroke of the punch 20, a first load F1 is applied to the punch 20 in the vertical direction. In addition, a second load N1 is applied to the die 10 in the horizontal direction.

[0036] Here, as the punch 20 descends, the thickness of the workpiece 100 decreases from T1 to T2 due to the ironing deformation of the workpiece 100. Therefore, the first load F1 includes the frictional force f1 of the workpiece 100 plus the forming force f2 of the workpiece 100. In other words, the first load F1 = frictional force f1 + forming force f2.

[0037] In the downward stroke after the plate thickness of workpiece 100 decreases to T2, as shown in Figure 7, only the frictional force f1 of workpiece 100 remains. In other words, since the first load F1 = frictional force f1, the kinetic friction coefficient of workpiece 100 can be calculated more accurately.

[0038] Figure 8 is an explanatory diagram illustrating how to determine the coefficient of dynamic friction of the workpiece 100 during the upward stroke of the punch 20 according to one embodiment. Note that the reference numeral M2 indicates the direction in which the punch rises. As shown in Figure 8, during the upward stroke of the punch 20, a first load F2 is applied to the punch 20 in the vertical direction. In addition, a second load N2 is applied to the die 10 in the horizontal direction.

[0039] Here, as the punch 20 rises, the plate thickness of the workpiece 100 is T2, so the first load F2 is only the frictional force f1 of the workpiece 100. Therefore, in the upward stroke of the punch 20, the forming force f2 of the workpiece 100 (see Figure 6) does not need to be considered, and the dynamic friction coefficient of the workpiece 100 can be calculated more accurately.

[0040] As described above, the friction coefficient measuring device 1 according to this embodiment comprises: a pair of dies 10 facing each other with a gap S1 between them and supporting the workpiece 100; a punch 20 that forms the workpiece 100 by being inserted into and removed from the gap S1 between the pair of dies 10 in the Z-axis direction (first direction); a first sensor 30 that measures the load applied to the punch 20 in the Z-axis direction; a slider 40 that supports each of the pair of dies 10 so as to be slidable in the X-axis direction (second direction) opposite to each other; a pair of fixed walls 50 arranged on the outside of the pair of dies 10; a second sensor 60 arranged between the pair of fixed walls 50 and the pair of dies 10 and measuring the load applied to the pair of dies 10 in the X-axis direction; and a calculation unit 70 that calculates the friction coefficient of the workpiece 100 based on the measurement results of the first sensor 30 and the second sensor 60. With this configuration, the friction coefficient during workpiece forming can be measured while the workpiece 100 is being formed.

[0041] Furthermore, in this embodiment, as shown in Figures 7 and 8, the calculation unit 70 calculates the dynamic friction coefficient of the workpiece 100 based on the measurement results of the first sensor 30 and the second sensor 60, which are measured from the time the punch 20 deforms the workpiece 100 until it is removed from the gap S1 between the pair of dies 10 (from the downward stroke after the reduction in plate thickness to the upward stroke). With this configuration, it is not necessary to consider the forming force f2 (see Figure 6) due to the ironing deformation of the workpiece 100, so the dynamic friction coefficient of the workpiece 100 can be calculated more accurately.

[0042] Furthermore, in this embodiment, as shown in Figure 1, the system includes a plate 21 that moves in the Z-axis direction together with the punch 20, and a pair of restricting walls 22 that are vertically attached from the plate 21 in the Z-axis direction and restrict the outward tilting of the pair of fixed walls 50 in the X-axis direction. With this configuration, the pair of restricting walls 22 receive the upper ends of the pair of fixed walls 50 at the base on the plate 21 side where there is less deflection, thereby restricting the tilting of the pair of fixed walls 50. As a result, fluctuations in the gap between the die 10 and the fixed walls 50 are suppressed, and the measurement value of the second sensor 60 becomes normal.

[0043] Furthermore, in this embodiment, the pair of restricting walls 22 are formed in a first range A1 including the punch 20 in the Z-axis direction. With this configuration, it is possible to suppress gap fluctuations between the die 10 and the fixed wall 50 in the forming range of the workpiece 100 into which the punch 20 is inserted into the gap S1 between the pair of dies 10.

[0044] Furthermore, in this embodiment, the pair of restricting walls 22 are formed in a second range A2 including the second sensor 60 in the Z-axis direction when the punch 20 deforms the workpiece 100. With this configuration, gap fluctuations between the die 10 and the fixed wall 50 can be suppressed within the installation range of the second sensor 60.

[0045] Furthermore, the friction coefficient measurement method of this embodiment includes a friction force measurement step of measuring the first loads F1 and F2 applied to the punch 20 during the process of forming the workpiece 100 as friction force, a normal force measurement step of measuring the second loads N1 and N2 applied to a pair of dies 10 that support the workpiece 100 and form a gap S1 into which the punch 20 can be inserted, and which attempt to widen the gap S1, as normal force, and a friction coefficient calculation step of calculating the friction coefficient of the workpiece 100 based on the friction force and normal force. With this configuration, the friction coefficient during workpiece forming can be measured while the workpiece 100 is being formed.

[0046] Furthermore, in this embodiment, in the friction coefficient calculation step, the dynamic friction coefficient of the workpiece 100 is calculated based on the friction force and normal force measured from the time the punch 20 deforms the workpiece 100 until it is withdrawn from the gap S1 between the pair of dies 10 (from the downward stroke after the reduction in plate thickness to the upward stroke). With this configuration, it is not necessary to consider the forming force f2 (see Figure 6) due to the ironing deformation of the workpiece 100, so the dynamic friction coefficient of the workpiece 100 can be calculated more accurately.

[0047] While preferred embodiments of the present invention have been described and explained above, it should be understood that these are illustrative and should not be considered limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the scope of the invention. Therefore, the present invention should not be considered limited by the foregoing description, but rather limited by the claims.

[0048] For example, in the above embodiment, the dynamic friction coefficient during workpiece forming was calculated, but the static friction coefficient during workpiece forming may also be calculated. [Explanation of Symbols]

[0049] 1... Friction coefficient measuring device, 2... Base, 3... Shaft, 4... Bushing, 10... Die, 11... Work support part, 20... Punch, 21... Plate, 22... Regulating wall, 30... First sensor, 40... Slider, 41... Rail, 42... Slider block, 43... Die mounting part, 50... Fixing wall, 51... Sensor mounting part, 52... Slide plate, 52a... Solid lubricant, 60... Second sensor, 70... Calculation unit, 100... Workpiece, 101... Curved part, A1... First range, A2... Second range, f1... Friction force, f2... Forming force, F1... First load, F2... First load, N1... Second load, N2... Second load, S1... Gap, T1... Plate thickness before reduction, T2... Plate thickness after reduction, M1... Punch downward direction, M2... Punch upward direction

Claims

1. A pair of dies that support the workpiece, with a gap between them, A punch that forms the workpiece by being inserted into the gap between the pair of dies in a first direction, A first sensor for measuring the load applied to the punch in the first direction, A slider that supports each of the pair of dies so as to be slidable in a second direction opposite to each other, A pair of fixed walls positioned on the outside of the pair of dies, A second sensor is positioned between the pair of fixed walls and the pair of dies to measure the load applied to the pair of dies in the second direction, The system includes a calculation unit that calculates the friction coefficient of the workpiece based on the measurement results of the first and second sensors, Friction coefficient measuring device.

2. The calculation unit calculates the dynamic friction coefficient of the workpiece based on the measurement results of the first and second sensors, which are measured between the time the punch deforms the workpiece and the time it is withdrawn from the gap between the pair of dies. The friction coefficient measuring device according to claim 1.

3. A plate that moves in the first direction together with the punch, The system comprises a pair of restricting walls that are suspended from the plate in the first direction and restrict the outward tilting of the pair of fixed walls in the second direction, The friction coefficient measuring device according to claim 1 or 2.

4. The pair of restricting walls are formed in a first range including the punch in the first direction. The friction coefficient measuring device according to claim 3.

5. The pair of restricting walls are formed in a second range including the second sensor in the first direction when the punch deforms the workpiece. The friction coefficient measuring device according to claim 3.

6. A friction force measurement process in which the first load applied to the punch during the workpiece forming process is measured as friction force, A normal force measurement step, in which a second load applied to a pair of dies that support the workpiece and form a gap into which the punch can be inserted, and which attempts to widen the gap, is measured as a normal force, A friction coefficient calculation step is included, which calculates the friction coefficient of the workpiece based on the frictional force and the normal force. Method for measuring the coefficient of friction.

7. In the friction coefficient calculation step, the dynamic friction coefficient of the workpiece is calculated based on the friction force and the normal force measured between the time the punch deforms the workpiece and the time it is withdrawn from the gap between the pair of dies. The method for measuring the coefficient of friction according to claim 6.

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