JP2018081728A - Cable deformation prediction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cable deformation prediction method.SOLUTION: A cable deformation prediction method includes: a stress distribution calculation process for calculating a stress distribution in a cable by linearly deforming the cable using an analysis model prepared by reproducing a shape of a bent habit of the cable using a curvature radius of the bent habit in the cable that intends to draw an arc at least under no stress load circumstances in the cable deformation prediction method in the cable having the bent habit; a rotation angle setting process of setting a rotation angle around the axis of the cable for determining a setting direction of a bent habit; and a cable deformation state calculation process for calculating a deformation state of the cable by deforming the cable according to the load conditions with the calculated stress distribution and the set rotation angle as an initial state.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a cable deformation prediction method.

  In response to recent strong demands for global environmental protection and energy saving, electric vehicles (EV) and fuel cell vehicles (FCEV) in which an electric motor is used as a main power source have been vigorously researched and developed. As a drive mechanism for these automobiles, a system in which a conventional engine (internal combustion engine) is simply replaced with an electric motor and an in-wheel motor system in which an electric motor is arranged in a wheel and directly driven are proposed. The in-wheel motor system is attracting attention as a very unique drive mechanism, such as the fact that a conventional engine room is not required and that each wheel can be driven independently.

  In the in-wheel motor system, power is supplied from the outside to a motor built in the wheel via a power cable. The power cable is subjected to repeated bending motions accompanying the movement of the suspension when the vehicle is running. At this time, it is extremely important that the power cable is routed so that excessive tensile stress is not applied to the power cable and it does not come into contact with surrounding structural members or rotating wheels.

  On the other hand, a method for visualizing the bent state of a plurality of conductor wires constituting a stranded wire cable is disclosed for a stranded wire cable routed in a bending movable part such as a door portion of an automobile (see Patent Document 1). ).

JP 2009-266775 A

  In an in-wheel motor type electric vehicle, the power cable of the in-wheel motor may unexpectedly come into contact with surrounding structural members. This means that when the power cable is subjected to repeated bending motion accompanying the movement of the suspension, the power cable is deformed in a direction away from the in-plane bending motion (referred to as out-of-plane deformation).

  Patent Document 1 describes a method for visually grasping a bending state of a conductor wire constituting a cable when the cable is bent with a certain curvature, and a visualization system. The bending state of the conductor wire calculated at this time is obtained by a geometrical calculation formula and does not consider the stress distribution inside the cable. Since the prediction of the out-of-plane deformation is caused by the stress distribution inside the cable, Patent Document 1 cannot deal with the out-of-plane deformation that is the subject of the present application.

  Sufficient elucidation is necessary because unexpected contact between the power cable and peripheral structural members leads to damage of the power cable over time.

  The present invention is an invention for solving the above-described problems, and provides a cable deformation prediction method capable of predicting the deformation of a cable in advance at the design stage on the premise that a cable having a bending rod is used. The purpose is to do.

  In order to achieve the above object, a cable deformation prediction method according to the present invention is a cable deformation prediction method for a cable having a bending rod, using at least a curvature radius of the bending rod in a cable to be drawn in an arc under a stress-free load environment. In order to determine the stress distribution calculation process for calculating the stress distribution in the cable by deforming the cable in a straight line using the analytical model created by reproducing the shape of the cable bending cage and the installation direction of the bending cage Rotation angle setting process to set the rotation angle around the cable axis of the cable, the calculated stress distribution and the set rotation angle as the initial state, the cable is deformed according to the load condition, and the deformation state of the cable is calculated A cable deformation state calculation step. Other aspects of the present invention will be described in the embodiments described later.

  According to the present invention, it is possible to predict the deformation of the cable in advance at the design stage on the assumption that a cable having a bending rod is used.

It is a schematic diagram which shows the example of the structure around an in-wheel motor when looking at the inner side of a wheel from the side surface direction of a vehicle body, and a cable layout. FIG. 2 is a schematic diagram illustrating an example of a structure and a cable layout when the inside of a wheel is viewed from the upper surface direction of the vehicle body of FIG. 1. It is a cross-sectional schematic diagram which shows an example of the cable used for a power cable. It is a block diagram which shows the prediction apparatus for estimating an out-of-plane deformation | transformation and its dispersion | variation. It is a flowchart which shows the prediction method of a cable out-of-plane deformation | transformation and its dispersion | variation. It is explanatory drawing which shows the example of modeling. It is explanatory drawing which shows the installation direction with respect to the winding hook of a cable.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. First, a structural example around the in-wheel motor and a cable layout will be described with reference to FIGS. 1 and 2.

(Cable layout)
FIG. 1 is a schematic diagram showing an example of a structure and a cable layout around an in-wheel motor when the inside of a wheel is viewed from the side of the vehicle body. FIG. 2 is a schematic diagram showing an example of the structure and cable layout when the inside of the wheel is viewed from the top surface direction of the vehicle body of FIG. The in-wheel motor 30 is fixed to the suspension arm 31 together with the suspension 32, and is arranged so that the motor rotation axis becomes the rotation axis of the wheel 35.

  Since the in-wheel motor 30 is required to be downsized to be disposed in a space constrained by the wheel 35 and to have a high output for driving the vehicle at the same time, a three-phase AC motor is usually used. . Therefore, a plurality of power cables 20 (for example, power cables 20 a to 20 c) are connected to the in-wheel motor 30 via the connection terminals 21 and the terminal block 33. Under such circumstances, the power cable 20 that supplies power to the in-wheel motor 30 is inevitably routed in a narrow space.

  Furthermore, the power cable 20 undergoes repeated bending motions as the suspension 32 moves during traveling of the vehicle. For example, the bending motion is received in the operating direction of the suspension 32 in FIG. At this time, the power supply cable 20 is routed so that excessive tensile stress is not applied to the power supply cable 20 and the surrounding structural member (for example, the suspension 32) and the rotating wheel 35 (including tires) are not contacted. It is very important to be done.

  As described above in the problem to be solved, in the electric vehicle based on the in-wheel motor system, the power cable 20 of the in-wheel motor 30 may unexpectedly come into contact with surrounding structural members. This is because when the power cable 20 is subjected to repeated bending motion accompanying the movement of the suspension 32, the power cable 20 is deformed in a direction away from the in-plane bending motion (in the xy plane in FIG. 1). Means that For example, an out-of-plane deformation that is a deformation in a direction indicated by an arrow in FIG. 2 occurs.

  As a result of various investigations while replacing the power cable 20, the state and extent of out-of-plane deformation differed for each power cable 20, and a consistent tendency was not found at the beginning. In other words, since the factors of the out-of-plane deformation and the variation of the power cable 20 are not understood, it was considered difficult to predict them, but the problem was solved based on the following basic idea.

(Basic idea of the present invention)
The present inventors configure the power cable 20 in order to elucidate the factors that cause the power cable 20 to vary greatly in the state and degree of out-of-plane deformation when the power cable 20 is bent. The survey was traced back to the production of electric wires.

  Generally, since the cable is manufactured in a long length, it is usually stored in a state where it is wound around a bobbin / drum until just before becoming a final product. When the cable is cut out from the bobbin / drum to a predetermined length in order to manufacture the power supply cable 20 by performing terminal processing, a curl may remain in the cut out cable. Such cable curl is said to be caused by the viscoelasticity of the insulating material / sheath material made of resin. In addition, the cable curl is considered to depend on the material of the insulating material / sheath material, the shelf life of the manufactured cable, and the diameter of the bobbin / drum on which the cable is wound.

  Accordingly, the present inventors have investigated and studied in more detail the relationship between the curl and the state and extent of out-of-plane deformation of the power cable 20 on the premise that a cable having curl is used. As a result, it has been found that the state and degree of out-of-plane deformation of the power cable 20 is strongly influenced by the relationship between the direction of winding of the cable used and the direction of bending motion imposed on the power cable 20. The present invention is based on this finding.

(Cable structure)
FIG. 3 is a schematic cross-sectional view showing an example of a cable used for a power cable. The cable 10 includes a cable 10 in which an insulating layer 13, a reinforcing braided layer 14, and a resin sheath 15 are sequentially formed on the outer periphery of a central conductor 12 (conductor), and connection terminals 21 ( 1). The cable 10 has a curl intended to draw an arc under a stress-unloaded environment.

  The cross-sectional structure of the cable 10 is not limited to that shown in FIG. 3, and there is no limitation on other configurations as long as it has at least the central conductor 12 and the outermost resin sheath 15. Further, in the present embodiment, the stress-free environment refers to a plate whose surface friction is as small as possible (for example, a surface-finished polytetrafluoroethylene (PTFE) plate or a surface-finished ice plate). ), An environment where the cable 10 is quietly placed.

  In the present embodiment, the center conductor 12 is preferably a stranded wire in which a plurality of strands 11 are twisted together. In general, a stranded wire conductor has an advantage of high bending resistance because uniform stress is applied to each strand during bending motion. In FIG. 3, a 29-core stranded wire is drawn, but it is of course not limited thereto. Moreover, the strand 11 itself may be made of a twisted structure of an even thinner strand.

  The materials and thicknesses of the insulating layer 13, the reinforcing braided layer 14, and the resin sheath 15 are not particularly limited, and the electrical equipment (for example, the in-wheel motor 30) to be connected to the power cable 20 (see FIG. 1). It may be selected appropriately according to the specifications. For example, as the cable 10, a polyethylene (PE) layer (thickness 0.5 mm) is used as the insulating layer 13 with respect to the central conductor 12 (diameter 3.4 mm), and a polyethylene terephthalate (PET) fiber braid as the reinforcing braid layer 14. A layer (thickness: 1.0 mm) can be used, and an ethylene propylene diene rubber (EPDM) layer (thickness: 0.8 mm) can be used as the resin sheath 15.

(Configuration of prediction device)
FIG. 4 is a block diagram showing a prediction device for predicting out-of-plane deformation and its variation. As shown in FIG. 4, the prediction device 100 includes an input device 41 composed of a keyboard, a mouse, and the like, an output device 42 composed of a display, a printer, and the like, a storage unit 43 composed of a hard disk for storing various information, A process for predicting out-of-plane deformation and variations of the cable 10 based on various data input by the cable stiffness measuring unit 44 for measuring the stiffness of the cable 10 and the input device 41 and the cable stiffness measuring unit 44. And a data processing unit 50.

  The input device 41 receives shape information of the cable 10 and parameters necessary for calculation. The output device 42 outputs the calculation result by the data processing unit 50.

  The data processing unit 50 includes a control unit 51 that comprehensively controls each function of the data processing unit 50 and an equivalent material property for calculating an equivalent material property from the stress-strain curve obtained by the cable stiffness measurement unit 44. A derivation unit 52, an analysis model creation unit 53 that creates an input file for finite element analysis of the cable 10 from various parameters input by the input device 41, a finite element analysis using the created input file, and a cable 10, a deformation state calculation unit 54 that calculates ten deformation states, and an output calculation unit 55 that calculates calculation results such as the deformation state, out-of-plane deformation variation, and stress of the cable 10 and outputs them to the output device 42.

(Prediction method)
Next, specific processing contents performed by the prediction device 100 will be described with reference to FIGS. 5 and 6. FIG. 5 is a flowchart showing an out-of-plane deformation and its variation prediction method. FIG. 6 is an explanatory diagram showing an example of modeling. 3 and 4 will be referred to as appropriate.

(S101): The data processing unit 50 receives input of various input parameters necessary for derivation of equivalent material properties of the cable 10 and prediction of variation in out-of-plane deformation. The input is performed by the input device 41 and recorded in the storage unit 43. The input parameters are the length of the cable 10, the radius of the cable 10, the stranding method of the strands 11, the radius of the strands 11, the number of the strands 11, the twisting pitch of the strands 11, the radius of curvature of the bending rod of the cable 10, installation It consists of direction step size (rotation step Δθ) and load conditions. As the load condition, selection of the type of load (whether it is L-shaped bending or S-shaped bending, etc.) and the magnitude of the load (curvature radius, geometric positional relationship, etc.) at that time are input. The installation direction will be described in S105.

(S102): The equivalent material property derivation unit 52 derives an equivalent material property value including all of the constituent materials such as the central conductor 12 and the resin sheath 15 shown in FIG. Replace with. Further, it is preferable that the conductor portion is modeled as a truss element that handles only the axial force and embedded in the analysis model that is a homogeneous body. The equivalent material properties of the homogeneous body portion are derived from the stress-strain curve obtained by the cable stiffness measurement unit 44. The stress-strain curve of the cable 10 can be obtained by a bending test such as a three-point bending.

  The equivalent material property derivation unit 52 creates a finite element analysis model of the cable 10 to be measured by the cable stiffness measurement unit 44 by the analysis model creation unit 53, and generates a stress-strain curve using the virtual property values. calculate. Evaluate the difference between the stress-strain curve obtained by the measurement and the stress-strain curve obtained by the calculation, and search for the material property with the smallest difference in the specified physical property range and the number of repetitions. Calculate material properties. As a search algorithm, an exhaustive search, a minimum gradient method, a genetic algorithm method, or the like can be used.

  As a material model, for example, a region excluding the conductor portion of the cable 10 can be an elasto-plastic body, and the conductor portion can be approximated as an elastic body.

(S103): The analysis model creation unit 53 converts the input cable radius, the length of the cable 10, the curvature radius of the bending rod, and the stranding method of the strand 11 into the finite element analysis model of the cable 10 having the bending rod. , The radius of the strand 11, the number of the strands 11, and the twist pitch of the strands 11. A finite element analysis model of the cable 10 having a bending rod can be created by the following procedure.

  First, the analysis model creation unit 53 creates a finite element analysis model of the linear cable 10 in accordance with the input parameters (FIG. 6 (a) linear shape creation). Next, the linear finite element analysis model is deformed according to the curvature radius of the bending rod input by the deformation state calculation unit 54 (FIG. 6B, deformation corresponding to the curvature radius of the bending rod). Next, only the shape information obtained at this time (excluding information such as stress) is transferred to the next step as a finite element analysis model (only the shape is transferred in FIG. 6C).

(S104): The deformation state calculation unit 54 linearly deforms the finite element analysis model created in S103, and calculates the stress distribution inside the cable (FIG. 6 (d) deforms into a linear shape and calculates the stress distribution).

(S105): The deformation state calculation unit 54 sets the rotation angle around the axis of the cable 10 in order to determine the installation direction of the bending rod, and sets the cable model (finite element analysis model) deformed linearly. The rotation angle (initial value is installation angle θ = 0 °) is set (FIG. 6 (e) installation at installation angle θ).

  In the present embodiment, the cable 10 including the conductor and the resin sheath 15 covering the conductor is disposed horizontally, the vertical plane along the axis of the cable 10 is used as a reference plane, and the cable 10 is bent in the vertical direction. . The rotation angle around the axis of the cable 10 with respect to the reference plane is set. Although the installation angle θ is set to 0 ° as an initial value, the calculation of S106 may be started from an arbitrary installation angle.

(S106): The deformation state calculation unit 54 deforms the cable 10 according to the input load condition and calculates the deformation state and the out-of-plane deformation amount of the cable 10 (FIG. 6 (f), deformation under the specified load condition, FIG. 6 (g) calculates out-of-plane deformation amount and cable deformation state).

(S107): The deformation state calculation unit 54 determines whether or not the installation angle θ indicating the installation direction has reached the upper limit value θmax (= 360 °). When the upper limit value θmax has not been reached (S107, No), the process proceeds to S108, and when it has reached (S107, Yes), the process proceeds to S109. The upper limit value θmax may be a predetermined value for evaluating out-of-plane deformation.

(S108): The deformation state calculation unit 54 updates the value by increasing the installation angle θ by the designated step size Δθ, and returns to S105.

(S109): The output calculation unit 55 calculates the variation width of the out-of-plane deformation amount with respect to the assumed load path and the deformation state, and displays them on the output device 42 (FIG. 6 (g)).

  The difference between the finite element analysis model created in S102 and the finite element analysis model shown in FIG. 6A in S103 will be described. Only the length of the cable 10 and the load condition are different. In the finite element analysis model created in S102, it is not necessary to model the bending wrinkle shown in FIG. As the load condition, for example, in the case of three-point bending, it is preferable to give a load, displacement time history, and the like. Therefore, the cable length of the finite element analysis model in FIG. 6A may be appropriately changed and used for the finite element analysis model created in S102.

(Confirmation of operation / effect of embodiment)
In order to confirm the effect of this embodiment, the power cable 20 shown below was produced, and the prediction accuracy was confirmed by measuring the amount of out-of-plane deformation.

(Power cable manufacturing method)
First, the cable 10 shown in FIG. 3 was produced. The produced power cable 20 has a PE layer (thickness 0.5 mm) as the insulating layer 13 and an EPDM layer (thickness 0) as the outermost resin sheath 15 on the outer periphery of the central conductor 12 (diameter 3.4 mm, 29 cores). Cable 10 (outer diameter 8.0 mm) in which 8.

  Next, in order to produce the power cable 20, the cable 10 was cut out from the bobbin with a length such that the distance between the connection terminals 21 was 160 mm. The cable 10 immediately after being cut out had a curl having a radius of curvature of about 100 mm due to the effect of being wound and stored on the bobbin. Finally, both ends of the cable 10 were processed to attach connection terminals 21 to produce a power cable 20.

(Out-of-plane deformation measurement method)
FIG. 7 is an explanatory view showing the installation direction with respect to the winding rod of the cable. FIG. 7 is an image diagram for understanding the relationship between the curl direction of the cable 10 and a plane (xy plane) that imposes L-shaped bending on the cable. A method for measuring the out-of-plane deformation amount of the power cable 20 will be described with reference to FIG.

  The power cable 20 is in a state where one end thereof (cable end A) is fixed to the origin O. In addition, the other end (cable end B) of the power cable 20 is in a free state (for example, not pinched by a chuck or the like), and the power cable 20 when it is assumed that the curl of the cable 10 appears clearly. (Specifically, the shape of the power cables 201 to 203) is shown.

  More specifically, the power cable 201 shows the case where the winding direction of the cable 10 is in the xy plane and the free cable end B is in the positive region of the y-axis (y ″ axis). (Hereinafter, this is defined as an installation direction of 0 °.) In the power cable 202, the winding direction of the cable 10 is in the xz plane, and the free cable end B is positive on the z axis (z ″ axis). (Hereinafter, this is defined as an installation direction of 90 °). The power cable 203 shows a case where the winding direction of the cable 10 is in the xz plane and the free cable end B is in the negative region of the z axis (z ″ axis) (hereinafter, this is installed) Defined as 270 °).

  In the measurement of the out-of-plane deformation amount, the cable end B is sandwiched between chucks and once moved on the x axis (on the xx ″ axis), then the cable end B is moved in the xy plane to move the power cable 201, L-shaped bending was imposed on 202 and 203. At this time, the maximum amount of deformation of the cable 10 of the power cables 201, 202, and 203 in the out-of-plane direction (z direction) was measured.

  7 assumes that the origin O corresponds to, for example, the connection terminal 21 in FIG. 1, and a cable 10 having a predetermined length therefrom. Actually, it is S-shaped bending as shown in FIG. 1, but in the present embodiment, L-shaped bending, which is a more basic deformation mode, is targeted. Since the S-shaped bending is a combination of the L-shaped bending, the same effect as the present embodiment can be obtained even in the S-shaped bending.

  Table 1 is a diagram showing the effect of the embodiment, and is a table showing prediction results and experimental results of out-of-plane deformation when bent in an L shape in the installation direction of 0 °, 90 °, and 270 °. is there. Table 1 shows a comparison result between the measured value and the predicted value according to the present invention (a comparison result between the measured value of the out-of-plane deformation amount and the predicted value).

  The cable out-of-plane deformation prediction apparatus 100 according to the present embodiment horizontally arranges a cable 10 including a conductor and a resin sheath 15 that covers the conductor, and sets a vertical plane along the axis of the cable 10 as a reference plane. An input device 41 that receives input parameters necessary for predicting out-of-plane deformation when the cable 10 having a curl to be arced in an unloaded environment is bent in the vertical direction, and an equivalent material property of the entire cable 10 Based on the equivalent material property derivation unit 52 that derives the value from the measured stress-strain curve, and the derived equivalent material property value of the cable 10, the shape having the curvature radius of the bending rod input from the input device 41 is reproduced. The finite element analysis model is created (for example, S103, FIGS. 6A to 6C), the cable 10 is linearly deformed, and the stress distribution in the cable 10 is calculated. S104, FIG. 6D), setting the rotation angle around the axis of the cable 10 for determining the installation direction of the bending rod (S105, FIG. 6E), the analysis model creation unit 53, and the calculated stress The distribution and the set rotation angle are set to the initial state, the cable 10 is deformed according to the load condition input from the input device 41, and the deformation state and the out-of-plane deformation amount of the cable 10 are calculated (S106, FIG. )) A deformation state calculation unit 54 and an output calculation unit 55 that outputs the calculation result of the deformation state and the out-of-plane deformation amount of the cable 10 (S109, FIG. 6G) to the output device 42.

  As described above, the prediction device according to the present invention can predict the amount of out-of-plane deformation at the time of cable bending and the variation width thereof with high accuracy, which has been difficult to predict. As a result, it is possible to know in advance the clearance value required for cable routing, and therefore it is possible to minimize unexpected cable contact.

  The above-described embodiments have been specifically described in order to help understanding of the present invention, and the present invention is not limited to having all the configurations described. For example, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, a part of the configuration of each embodiment can be deleted, replaced with another configuration, or added with another configuration. The scope of application of the present invention is not particularly limited to cables for in-wheel motors, and can be applied to all cables for bending such as other bending cables for automobiles and cables for industrial robots.

10 Cable 11 Wire 12 Central conductor (conductor)
DESCRIPTION OF SYMBOLS 13 Insulation layer 14 Reinforcement braided layer 15 Resin sheath 20, 20a, 20b, 20c, 201, 202, 203 Power cable 21 Connection terminal 30 In-wheel motor 31 Suspension arm 32 Suspension 33 Terminal block 35 Wheel 41 Input device 42 Output device 43 Memory Unit 44 Cable rigidity measurement unit 50 Data processing unit 51 Control unit 52 Equivalent material property derivation unit 53 Analytical model creation unit 54 Deformation state calculation unit 55 Output calculation unit 100 Prediction device

Claims (4)

In a cable deformation prediction method for a cable having a bending flaw,
The cable is deformed into a straight line by using an analytical model created by reproducing the shape of the bending rod of the cable, using the radius of curvature of the bending rod in the cable which is going to draw an arc under at least a stress-free environment. And a stress distribution calculation step for calculating the stress distribution in the cable,
A rotation angle setting step for setting a rotation angle around the axis of the cable for determining an installation direction of the bending rod;
A cable deformation state calculating step of setting the calculated stress distribution and the set rotation angle as an initial state, deforming the cable according to a load condition, and calculating a deformation state of the cable. Cable deformation prediction method. The load condition is determined by the type of load and the magnitude of the load at that time.
The cable deformation prediction method according to claim 1, wherein: The analysis model is created from the radius, the length, the bending radius of the bending rod, the strand twisting method, the strand radius, the number of strands, the strand twist pitch of the strand,
The cable deformation prediction method according to claim 1 or 2, characterized in that: Stress distribution calculated by the stress distribution calculation step excludes stress information obtained before the cable is deformed linearly,
The cable deformation | transformation prediction method of any one of Claim 1 thru | or 3 characterized by the above-mentioned.

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