JP2018118342A - Crank shaft manufacturing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crank shaft manufacturing apparatus which corrects deformation of a rotating workpiece caused by centrifugal force by pressing force to conduct lathe turning of the workpiece.SOLUTION: A chuck device 3 holds a workpiece 20 in an axial direction and applies pressing force to the workpiece 20. A rotary mechanism 1 rotates the workpiece 20. A tool 2 is configured to move in the axial direction of the workpiece 20 and turns the workpiece 20 on a lathe. A rotation speed detection part 4 detects a rotation speed of the rotary mechanism 1. A rotation number calculation part 5 calculates a rotation number of the workpiece 20 from a diameter of a non-processing part of the workpiece 20 and the detected rotation speed of the rotary mechanism 1. A deformation volume calculation part 6 calculates a deformation volume of the workpiece 20 caused by centrifugal force on the basis of rigidity of the workpiece 20, a centroid position of the workpiece 20, and the calculated rotation number of the workpiece 20. A pressing force control part 7 controls the pressing force applied to the workpiece 20 on the basis of the calculated deformation volume.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a crankshaft manufacturing apparatus.

   Generally, a crankshaft is manufactured by cutting or grinding while rotating a workpiece before processing. As a method for manufacturing such a crankshaft, an example of a turning and broaching machine has been proposed (Patent Document 1). The turning and broaching machine has first and second encoders, first and second vibration sensors, and a control unit. The first and second encoders detect the phase of the material crankshaft centered on the rotation axis during rotation of the material crankshaft, and output phase data indicating the detected phase. The first and second vibration sensors detect vibration of the material crankshaft in the radial direction during rotation of the material crankshaft, and output vibration data indicating the detected vibration. The control unit calculates a rotation unbalance amount of the material crankshaft based on the phase data and the vibration data. As a result, by feeding back the amount of unbalance during processing, processing can be performed with correction, and the number of defective products can be reduced.

JP 2015-44249 A

  However, even if the unbalance amount is corrected as in the crankshaft manufacturing method described above, the center of gravity of the workpiece on the crankshaft is displaced from the central axis. For this reason, if turning is performed as it is, the rotating workpiece is deformed by centrifugal force due to the deviation of the center of gravity, and the processing portion is inclined with respect to the central axis. As a result, the shaft runout accuracy at the time of workpiece turning deteriorates.

  A crankshaft manufacturing apparatus according to an aspect of the present invention includes a chuck device that holds a workpiece in the axial direction of the workpiece, applies a pressing force to the workpiece, a rotation mechanism that rotates the workpiece, and an axial direction of the workpiece. A tool for turning the workpiece, a rotation speed detection unit for detecting the rotation speed of the rotation mechanism, a diameter of a non-working part of the workpiece, and a detected rotation speed of the rotation mechanism, Based on the rotational speed calculation unit that calculates the rotational speed of the workpiece, the rigidity of the workpiece, the gravity center position of the workpiece, and the calculated rotational speed of the workpiece, the deformation amount of the workpiece due to centrifugal force is calculated. A deformation amount calculating unit; and a pressing force control unit that controls a pressing force applied to the workpiece based on the calculated deformation amount.

  ADVANTAGE OF THE INVENTION According to this invention, the crankshaft manufacturing apparatus which corrects the deformation | transformation by the centrifugal force of the rotating workpiece | work with a pressing force, and performs the turning process of a workpiece | work can be provided.

It is a figure which shows an example of a crankshaft. It is a figure which shows the machining peripheral speed dependence of the surface precision at the time of manufacturing a crankshaft by turning. It is a figure which shows the weight balance in a L3 crank. It is a figure which shows the weight balance in a L4 crank. It is a figure which shows an example of a deformation | transformation of the workpiece | work by centrifugal force. It is a figure which shows an example of a deformation | transformation of the workpiece | work by pressing force. It is a figure which shows an example of the workpiece | work in which the deformation | transformation by centrifugal force was canceled by controlling pressing force. It is a figure which shows typically the structure of the crankshaft manufacturing apparatus concerning Embodiment 1. FIG. It is a figure which shows the pressing force control operation | movement of the crankshaft manufacturing apparatus concerning Embodiment 1. FIG. It is a figure which shows the deformation | transformation by the centrifugal force of a simple support beam.

Embodiment 1
In the present embodiment, a crankshaft manufacturing apparatus that corrects deformation of a workpiece caused by applying centrifugal force to the workpiece by rotation when the crankshaft is manufactured by turning while cutting the workpiece will be described. Hereinafter, the mechanism by which the workpiece 20 is deformed by centrifugal force will be described.

  FIG. 1 is a diagram illustrating an example of a crankshaft. In FIG. 1, the workpiece 20 is configured as a workpiece for manufacturing an L3 crank. In order to manufacture the crankshaft, it is necessary to set the peripheral speed at the cutting edge of the cutting tool to a predetermined speed or more in order to achieve the required surface accuracy. FIG. 2 shows the peripheral speed dependence of surface accuracy when a crankshaft is manufactured by turning. The surface accuracy is highly accurate and stable as the peripheral speed increases. In general, in a region where the surface accuracy is smaller than a standard value, the peripheral speed used for processing is determined in consideration of the durability of a tool for cutting the crankshaft. Further, in order to hold the workpiece 20, a pressing force PF along the axial direction is applied to the workpiece 20 from a chuck device described later.

  However, when the counterweight is arranged unbalanced as in the L3 crank, the weight balance is unbalanced. FIG. 3 shows the weight balance in the L3 crank. As shown in FIG. 3, in the L3 crank, the weight balance between the rear side 21 and the front side 22 is in an opposite phase.

  Here, an L4 crank will be described as a comparative example in which no imbalance occurs in the crankshaft. FIG. 4 shows the weight balance in the L4 crank 30. On both the rear side 31 and the front side 32, the weight balance position coincides with the central axis, that is, the rotation axis. In FIG. 4, the point indicating the weight balance is displayed as a white point near the center of the chart.

  When trying to manufacture a crankshaft in which an imbalance has occurred as described with reference to FIG. 3 by turning, deformation due to centrifugal force due to rotation occurs. FIG. 5 is a diagram illustrating an example of deformation of a workpiece due to centrifugal force. In FIG. 5, the solid line represents the shape of the workpiece 20 after deformation, and the two-dot chain line represents the shape of the workpiece 20 before deformation. As shown in FIG. 5, since a centrifugal force is applied to the counterweight provided on the workpiece 20 that is an L3 crank, the counterweight is set on the basis of the crankpin 25 that connects the two counterweights 23 and 24 arranged opposite to each other. It deform | transforms so that the distance between the weights 23 and 24 may spread. As a result, the shaft portion on the front side 22 that is the processing portion of the workpiece 20 is inclined with respect to the rotation axis, and the surface accuracy is lowered due to the turning processing. In FIG. 5, only representative counterweights and crankpins are provided with reference numerals, but it goes without saying that similar deformations may occur with other counterweights other than those with reference numerals.

  Next, the relationship between the deformation of the workpiece 20 and the pressing force will be examined. FIG. 6 is a diagram illustrating an example of deformation of a workpiece due to a pressing force. In FIG. 6, the solid line represents the shape of the workpiece 20 after deformation, and the two-dot chain line represents the shape of the workpiece 20 before deformation. As shown in FIG. 6, a pressing force is applied to the shaft portion of the workpiece 20 from both ends, and the workpiece 20 is deformed. At this time, the workpiece 20 is deformed so that the distance between the counterweights becomes narrower with the shaft portion connecting the two counterweights arranged opposite to each other as a base point. That is, it can be seen that the deformation of the workpiece 20 due to the pressing force is opposite to the deformation of the workpiece due to the centrifugal force. As a result, the shaft portion on the front side 22 that is the processing portion of the workpiece 20 is inclined in the opposite direction to the case of deformation due to centrifugal force with respect to the rotation shaft. In FIG. 6, only representative counterweights and crankpins are provided with reference numerals, but it goes without saying that similar deformations may occur with other counterweights other than those with reference numerals.

  In FIG. 6, an example in which a large pressing force is applied is shown for easy understanding of the deformation amount due to the pressing force. However, the pressing force applied when performing a normal turning process is the processing accuracy of the workpiece 20. Is set to such a size that does not deteriorate.

  As described above, in the present embodiment, when the workpiece 20 is turned, the deformation of the workpiece 20 is canceled by controlling the pressing force so that the deformation due to the centrifugal force is canceled. FIG. 7 is a diagram illustrating an example of a workpiece in which the deformation due to the centrifugal force is canceled by controlling the pressing force. In FIG. 7, the solid line represents the shape of the workpiece 20 after canceling the deformation, and the two-dot chain line represents the shape of the workpiece 20 before the deformation. As shown in FIG. 7, by controlling the pressing force to cancel the deformation due to the centrifugal force, the shaft portion that is the processing portion of the workpiece 20 is parallel to the rotation axis and rotates around the rotation axis. Become. Thereby, the axial runout accuracy at the time of turning of the workpiece 20 can be improved.

  Hereinafter, the crankshaft manufacturing apparatus 10 concerning Embodiment 1 is demonstrated. FIG. 8 is a diagram schematically illustrating the configuration of the crankshaft manufacturing apparatus according to the first embodiment. FIG. 9 is a diagram illustrating a pressing force control operation of the crankshaft manufacturing apparatus according to the first embodiment. The crankshaft manufacturing apparatus 10 includes a rotation mechanism 1, a tool 2, a chuck device 3, a rotation speed detection unit 4, a rotation speed calculation unit 5, a deformation amount calculation unit 6, and a pressing force control unit 7.

  The chuck device 3 is configured to chuck the workpiece 20 in the rotation axis direction. In FIG. 8, the chuck device 3 includes chucks 3 </ b> A and 3 </ b> B. The chuck 3 </ b> A chucks one end on the rear side 21 of the workpiece 20, and the chuck 3 </ b> B chucks one end on the front side 22 of the workpiece 20. In this example, the chuck 3 </ b> B may be configured to hold the workpiece 20 in a rotatable manner by inserting a protrusion into a hole provided at the end portion of the front side 22 of the workpiece 20, for example.

  The rotation mechanism 1 is configured to be able to rotate the workpiece 20 with the axial direction of the workpiece 20 as a rotation axis. In FIG. 1, the rotation mechanism 1 is constituted by a shaft member joined to a chuck 3A. The workpiece 20 is rotated by rotating the shaft member around the axis direction of the workpiece 20 by a driving device (not shown) such as a motor. In FIG. 8, the drive device is not shown, but the rotation mechanism here may be handled as including the drive device.

  The tool 2 is a cutting tool capable of moving in the axial direction and the radial direction of the workpiece 20, and the workpiece 20 is cut by pressing a blade provided at the tip against the surface of the workpiece 20.

  The rotation speed detection unit 4 is configured to be able to detect the rotation speed Vr of the rotation mechanism of the non-working part of the workpiece 20.

  The rotation speed calculation unit 5 calculates the rotation speed NR of the workpiece 20 from the diameter D of the shaft portion (shaft portion remaining after turning) that is a machining portion of the workpiece 20 and the rotation speed Vr detected by the rotation speed detection unit 4. To do.

  The deformation amount calculation unit 6 calculates the centrifugal force applied to the workpiece 20 from the specifications of the workpiece 20 and the rotational speed NR, and calculates the deformation amount of the workpiece 20 due to the calculated centrifugal force.

For simplification of description, calculation of deformation amount due to centrifugal force in an example of a simple support beam will be described. FIG. 10 is a diagram illustrating the deformation of the simple support beam due to the centrifugal force. In FIG. 10, it is assumed that a clamping force (that is, centrifugal force) F from the shear direction is applied to a simple support beam having a length L, a height H, and a depth B. When the Young's modulus of the simple support beam is E and the secondary moment of the simple support beam is I, the maximum value of the deformation amount σ is expressed by the following equation (1).

  In order to calculate the deformation amount of the workpiece 20 specifically, the deformation amount of the workpiece 20 is estimated by performing deformation analysis of the workpiece 20 by CAE (Computer Aided Engineering) analysis using the above equation (1). Can do. In other words, the deformation amount of the workpiece 20 due to the centrifugal force can be calculated from the rotation speed, the rigidity (Young's modulus) of the workpiece 20 and the weight unbalance of the workpiece 20. The weight unbalance of the workpiece 20 can be obtained by calculating the position of the center of gravity from the shape of the workpiece 20 and the material characteristics (for example, density) of the workpiece 20.

  In turning, a pressing force for holding the workpiece 20 is applied via the chuck device 3. As described with reference to FIG. 6, since the workpiece 20 is deformed also by the pressing force, the deformation amount calculation unit 6 calculates the deformation amount due to the pressing force as in the case of the centrifugal force.

  Then, the deformation amount calculation unit 6 adds the deformation amount due to the centrifugal force and the deformation amount due to the pressing force, and calculates the deformation amount due to the turning process. However, since the deformation amount due to the pressing force is usually smaller than the deformation amount due to the centrifugal force, the deformation amount of the workpiece 20 calculated here may be handled as being substantially the deformation amount due to the centrifugal force.

  The pressing force control unit 7 determines a pressing force for canceling the deformation based on the calculated deformation amount. Then, the pressing force control unit 7 controls the pressing force PF applied to the workpiece 20 from the chuck device 3 so that the calculated pressing force is applied to the workpiece 20. Thereby, the deformation | transformation of the workpiece | work 20 by centrifugal force is canceled.

  As described above, according to this configuration, it is possible to realize a crankshaft manufacturing apparatus capable of offsetting deformation caused by centrifugal force during turning of a workpiece by controlling the amount of pressing applied to the workpiece and improving machining accuracy. it can. In addition, since it is only necessary to control the pressing force, the deformation of the workpiece due to the centrifugal force can be canceled without adding a special mechanism or the like to the crankshaft manufacturing apparatus.

  In addition, according to this configuration, the crankshaft can be manufactured by turning, which is advantageous in that the crankshaft can be manufactured at a lower cost compared to grinding.

Other Embodiments The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit of the present invention. For example, in the above-described embodiment, the peripheral speed has been described. However, for example, by reducing the toughness of the tool, the peripheral speed at the time of turning can be reduced. Thereby, you may make small the pressing force for canceling the deformation | transformation of the workpiece | work by centrifugal force.

  Further, in order to apply a necessary pressing force to the work so that the chuck device can securely hold the work, the rigidity of the work material may be appropriately selected.

DESCRIPTION OF SYMBOLS 1 Rotation mechanism 2 Tool 3 Chuck apparatus 3A Chuck 3B Chuck 4 Rotation speed detection part 5 Rotational speed calculation part 6 Deformation amount calculation part 7 Pressing force control part 10 Crankshaft manufacturing apparatus 20 Work 21 Rear side 22 Front side 23, 24 Counterweight 25 Crankpin 30 L4 crank 31 Rear side 32 Front side

Claims (1)

A chuck device that holds the workpiece in the axial direction of the workpiece and applies a pressing force to the workpiece;
A rotation mechanism for rotating the workpiece;
A tool configured to be movable in the axial direction of the workpiece, and turning the workpiece;
A rotation speed detector for detecting the rotation speed of the rotation mechanism;
A rotation speed calculation unit that calculates the rotation speed of the workpiece from the diameter of the non-working portion of the workpiece and the detected rotation speed of the rotation mechanism;
A deformation amount calculation unit that calculates the deformation amount of the work due to centrifugal force based on the rigidity of the work, the gravity center position of the work, and the calculated rotation speed of the work,
A pressing force control unit that controls the pressing force applied to the workpiece based on the calculated deformation amount,
Crankshaft manufacturing equipment.

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