JP4916906B2 - Liquid pool simulation method and simulation program - Google Patents

Description

  The present invention relates to a liquid pool simulation method and a simulation program for simulating a liquid pool of immersion liquid remaining on a workpiece subjected to immersion treatment.

  In the work dipping process in electrodeposition coating, plating, or the like, when the work is lifted from the dipping tank, the dipping solution may remain in the bag portion of the work and become a liquid pool. If the immersion liquid in this liquid pool is not completely drained before entering the next process, processing defects due to residual liquid on the workpiece surface, mixing into the processing liquid in the next process, deterioration in appearance quality due to heating / drying of the residual liquid, Furthermore, the cost is increased due to an increase in the amount of immersion liquid used by taking out the immersion liquid.

  For this reason, generally, a discharge hole for discharging the liquid is provided in advance in a portion where the liquid of the workpiece is expected to be accumulated. It is necessary to keep the drainage holes of the liquid pool to the minimum necessary. If a large number of drainage holes are provided without thorough examination, not only will the structural strength be reduced, but the This increases the number of processing steps and time, and enormous costs are required.

In order to cope with this, for example, Patent Document 1 proposes a technique for forming a discharge hole that does not require a grommet when the discharge hole is processed in the dipping process of the automobile body. Further, in Patent Document 2, in an automobile body formed by joining other members to a hollow extruded member, at least one part of the joining parts of each member is provided with a passage leading to the outside of the body, so that There has been proposed a technique for quickly and reliably removing the processing liquid and the like accumulated inside each member.
JP-A-7-81640 JP 2004-34855 A

  The liquid pool generated in the workpiece can be predicted by fluid analysis simulation using a computer. This computer simulation can be used to calculate the location of the liquid pool and the time for discharging the liquid from the liquid pool, etc., and determine the suitability of the work discharge hole and the work transfer speed. It is extremely effective in improving.

  However, in general, fluid analysis simulation requires enormous time for creation and processing of calculation data, requires a high-speed and large-scale computer system, and increases the cost and man-hour required for simulation. Furthermore, it is difficult to flexibly cope with a design change or the like by quickly changing an analysis model and executing a re-simulation.

  The present invention has been made in view of the above circumstances, and it is possible to determine whether a liquid pool generated in a work to be dipped and the suitability of a drain hole of the liquid pool can be determined without requiring a complicated fluid analysis. An object is to provide a simulation method and a simulation program.

In order to achieve the above object, according to the method for simulating a liquid pool according to the present invention, a computer models a work to be dipped with data of a plurality of elements, and the attribute of each element is gas based on the positional relationship in the direction of gravity. In a liquid pool simulation method in which a computer determines whether the liquid is liquid or not and simulates a liquid pool of immersion liquid, the liquid pool volume of the liquid stored in the liquid pool is an element and attribute whose attributes are determined to be gas. A liquid volume calculation step for calculating based on the area of the horizontal liquid surface formed by correcting the boundary between the liquid and the determined element and the height of the liquid surface in the gravitational direction, and the liquid pool from the liquid discharge time at which the volume fraction of the liquid is discharged from the immersion bath the workpiece is immersed lifted is the work bottom of the liquid reservoir is above the dip bath of the liquid surface on the Time until position, liquid discharge time the bottom of the liquid reservoir is calculated as a time obtained by adding the time at which the volume fraction of the liquid is discharged from the reservoir the liquid state located on the liquid surface of the dipping bath And a calculation step.

The liquid pool simulation program according to the present invention models a workpiece to be dipped with data of a plurality of elements, and determines whether the attribute of each element is gas or liquid based on the positional relationship in the direction of gravity. In a liquid pool simulation program that can be executed by a computer that simulates a liquid pool of immersion liquid, the liquid pool volume of the liquid stored in the liquid pool is determined as an element whose attribute is determined to be gas and an attribute is determined as liquid A liquid volume calculation step for calculating based on the area of the horizontal liquid level formed by correcting the boundary with the element and the height of the liquid surface in the direction of gravity, and a liquid corresponding to the volume from the liquid pool liquid discharge time but discharged from the immersion bath the workpiece is immersed lifted is the work bottom of the liquid sump until the position above the liquid surface of the dipping bath And between the bottom of the liquid reservoir is a liquid discharge time calculating step of calculating a time obtained by adding the time at which the volume fraction of the liquid is discharged from the liquid reservoir while positioned above the liquid level of the immersion bath It is characterized by providing.

  According to the present invention, as a simulation that can be applied to a relatively small-scale system without requiring complicated fluid analysis, it is determined whether or not the liquid pool generated in the work to be immersed and the discharge hole of the liquid pool are appropriate. In addition, it is possible to flexibly cope with model changes due to design changes.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 15 relate to an embodiment of the present invention, FIG. 1 is a basic configuration diagram of a simulation apparatus, FIG. 2 is a schematic explanatory diagram of a car body painting line, and FIG. 3 is an explanation showing a state of the car body in the painting line. FIG. 4, FIG. 4 is an explanatory view showing the liquid reservoir portion of the vehicle body, FIG. 5 is an explanatory view showing the liquid reservoir surface in the horizontal state, FIG. 6 is an explanatory diagram showing the liquid reservoir surface in the inclined state, and FIG. FIG. 8 is an explanatory view showing the mesh arrangement of the model, FIG. 8 is an explanatory view showing the relationship between the meshes of the data structure of the numerical calculation model, FIG. 9 is an explanatory view showing the node number and coordinate data of the data structure of the numerical calculation model, Is an explanatory diagram showing an example in which the liquid reservoir is expressed by a numerical calculation model, FIG. 11 is an explanatory diagram showing a method for calculating the volume of the liquid reservoir, FIG. 12 is an explanatory diagram showing a method for calculating the liquid level, and FIG. Explanatory drawing which shows the calculation method of the liquid discharge time from the liquid reservoir of the vehicle body Figure 14 is a flow chart of the liquid pool simulation program, Fig. 15 is a flowchart of the liquid discharge judging program.

  As shown in FIG. 1, the simulation apparatus 1 according to the present embodiment is an immersion liquid that remains without being discharged from a workpiece when a workpiece such as a body shell of an automobile is subjected to immersion treatment such as electrodeposition coating or plating. This is a simulation of the liquid pool. The simulation apparatus 1 is configured using a single computer such as a microcomputer or a personal computer, or a plurality of computers connected to each other via a network.

  Below, the example which comprises the simulation apparatus 1 with a single computer for convenience is demonstrated. The simulation apparatus 1 includes an arithmetic device 10, an input device 11 such as a keyboard and a mouse, a display device 12 such as a CRT and a liquid crystal display, an external storage device 13 such as a magnetic disk and an optical disk, and the like.

  The arithmetic device 10 includes an internal memory such as a CPU, a ROM and a RAM, an input / output interface, and the like, and includes a simulation program stored in an internal ROM, an external storage device 13 and an external storage medium, or a network (not shown) A simulation program loaded from the outside via the communication device is executed by the CPU, and the workpiece (object) to be analyzed instructed via the input device 11 is immersed in the immersion bath in a pseudo manner, and the object is obtained by the immersion. Simulates the pool of immersion liquid generated in

  For example, as an application example of the simulation according to the present invention, there is a simulation in which the distribution of the immersion liquid and the air in the electrodeposition coating line of the vehicle body is numerically analyzed to predict the occurrence of the immersion liquid pool in the object to be coated. Here, the painting line of the vehicle body will be briefly described with reference to FIG.

  As shown in FIG. 2, a vehicle body body 20 of an automobile configured by joining a plurality of vehicle body panels to each other by welding or the like is conveyed in a substantially horizontal direction on a painting line while being mounted on a hanger of a conveying device 21. The The coating line is configured by continuously arranging a plurality of immersion tanks 22 (in FIG. 2, a single immersion tank is shown as a representative). As a pretreatment for electrodeposition coating, the body panel is degreased, Treatments such as washing with water, surface conditioning, film formation, washing with water are performed.

  After these processes, the vehicle body 20 descends toward the immersion tank (electrodeposition tank) 22 filled with the electrodeposition liquid 23 and moves substantially horizontally while being immersed in the electrodeposition liquid 23. In this state, paint is deposited on the vehicle body panel by applying a voltage to the vehicle body 20 and electrodes (not shown) in the immersion bath 22. Thereafter, the vehicle body 20 is pulled up from the immersion tank 22 by the transfer device 21, and the electrodeposition liquid 23 adhering to the vehicle body panel without being electrodeposited is removed by washing with water.

  In such a coating line, since the vehicle body 20 is continuously immersed in the plurality of immersion tanks 22, the immersion liquid is completely discharged before being pulled up from one immersion tank and entering the next process, It must be recovered in the original immersion tank. However, in the case of a workpiece having a complicated shape, there is a possibility that the immersion liquid is not completely discharged until it is lifted from one immersion tank and enters the next step, and remains as a liquid pool.

  When such a liquid pool occurs, it may be mixed into the immersion liquid in the next process, resulting in a processing failure, or the residual liquid may be heated and boiled in the drying process to impair the appearance of the product. The quality will be degraded. Furthermore, since the immersion liquid is taken out from the immersion tank, the amount of the immersion liquid used is increased, resulting in a cost increase.

  Therefore, the arithmetic unit 10 executes a liquid pool simulation program in order to predict the occurrence of the liquid pool of the workpiece in the immersion process in advance and take countermeasures, and based on the shape of the workpiece and the moving state in the immersion processing line, The presence or absence of is determined. And when there exists a liquid pool, the discharge time of the residual liquid from the discharge hole drilled beforehand or the discharge hole set on simulation is calculated. The liquid pool simulation by the arithmetic unit 10 can be performed at a relatively high speed without requiring complicated fluid analysis, and can determine whether the liquid pool generated in the work to be dipped and the discharge hole are appropriate. Also, it is possible to flexibly cope with model changes due to design changes.

  Hereinafter, the liquid pool simulation by the arithmetic unit 10 will be described by taking an example in which the vehicle body 20 is immersed in the immersion tank 22 as shown in FIG. In this embodiment, the immersion tank 22 has a shape having a side wall 22b having an inclination angle θ with respect to the bottom surface 22a, and is connected to the side wall of the subsequent immersion tank 22 via a substantially horizontal conveyance path 22c. It shall be. The body body 20 that is a workpiece is immersed in the immersion liquid having a liquid level height of LiqH from the bottom surface in the immersion tank 22, moves substantially horizontally on the bottom surface, is lifted from the immersion tank 22 at an inclination angle θ, and then transported. It moves substantially horizontally along the path 22c and descends into the next immersion tank 22.

  In addition, the hanger which conveys the vehicle body 20 is set to L1 the conveyance distance which raises the vehicle body 20 by the inclination angle (theta) along the side wall 22b from the horizontal movement in the immersion tank 22, and after this conveyance distance L1 The distance from the horizontal movement of the transport path 22c to the deadline DL is set to L2. As will be described later, the deadline DL is a line capable of collecting the immersion liquid discharged from the liquid reservoir of the vehicle body 20 without taking it to the next stage side.

  FIG. 4 shows a three-dimensional image of a liquid reservoir portion expected inside the vehicle body 20, and a box-shaped bag portion 24 on the front side floor portion and a box-shaped bag portion on the rear side floor portion. 25 is expected to be a liquid reservoir where the immersion liquid remains and is stored after being pulled up from the immersion tank 22. Thus, in order to discharge the stored liquid, it is common to provide a hole for draining in advance at a place where it is expected to be a liquid reservoir in advance, as shown in FIG. The bag portions 24 and 25 are respectively provided with drain holes 24a and 25a on the bottom surface side.

  In this case, in the determination of the liquid pool portion in the present simulation, the liquid drain holes 24a and 25a of the bag portions 24 and 25 are intentionally blocked on the analysis model, and the liquid pool determination is performed. In addition, since the body body 20 is inclined at the inclination angle θ when the vehicle body 20 is pulled up from the immersion tank 22, the body body 20 is inclined at the inclination angle θ as shown in FIG. This is executed for the state, and the heights of the liquid surfaces 24b and 25b of the bag portions 24 and 25 and the volume of the remaining liquid (liquid pool volume) are calculated.

  As for the time for discharging the immersion liquid from the liquid reservoir (bag parts 24, 25), the vehicle body 20 is pulled up from the immersion tank 22, and the drain holes 24a, 25a of the bag parts 24, 25 are exposed on the liquid surface. Is calculated as a time obtained by adding the time until the liquid drainage holes 24a and 25a and the time required for discharging the liquid for each liquid storage volume. This discharge time is a unit determined in advance based on the inclination angle θ of the immersion tank 22, the pitch speed (conveying speed of the vehicle body 20), the liquid reservoir volume, the hole diameters of the liquid drain holes 24a and 25a, the viscosity of the immersion liquid, and the like. Calculated from the discharge flow rate per hour.

  As described above with reference to FIG. 3, the vehicle body 20 is lifted from the predetermined immersion tank 22, and then horizontally moved along the conveyance path 22 c and lowered into the next immersion tank 22. As shown in FIG. 3, a deadline DL is set in the conveyance path 22c at a position of a length L2 from the starting point of the horizontal conveyance path 22c, and liquid is collected until the vehicle body 20 reaches the deadline DL. If the part of the immersion liquid is discharged, the discharged immersion liquid can be collected in the previous immersion tank 22.

  Therefore, in this simulation, if the calculated liquid discharge time from the liquid reservoir is shorter than the time required for the vehicle body 20 to reach the deadline DL calculated from the pitch speed, there is no particular problem and “OK”. It can be judged that there is. On the other hand, if the liquid discharge time calculated by this simulation is longer than the time to reach the deadline DL, the previous stage immersion liquid stored in the liquid reservoir will be taken out to the next stage, causing a problem. Therefore, “NG” can be determined.

  As will be described later, in this embodiment, instead of comparing the liquid discharge time during which all the liquid stored in the liquid reservoir is discharged with the time until the deadline DL is reached, the time until the deadline DL is reached. By comparing the volume discharged until this time with the liquid pool volume of the liquid stored in the liquid pool, it is determined whether it is “OK” or “NG”.

  The function of the arithmetic unit 10 that executes the above liquid pool simulation can be expressed by the model construction unit 10a, the liquid pool determination unit 10b, the liquid pool volume calculation unit 10c, the liquid discharge time calculation unit 10d, and the post processing unit 10e. . The arithmetic device 10 simulates the occurrence of a liquid pool using a geometric technique based on an analysis model in which the shape of the workpiece is modeled with data of a plurality of elements, and outputs the simulation result to the display device 12 for display. The display device 12 may display not only the simulation result but also the simulation process.

  The model construction unit 10a constructs an analysis model by dividing the shape data of the object into a plurality of elements. As a method for constructing the analysis model, a method using a mesh that represents a surface shape of an object divided into a plurality of predetermined shapes, a method of arranging a plurality of nodes (nodes) on the surface of the object, or the like is used. be able to. In the following, an example of constructing an analysis model by using an analysis model in which the surface shape of an object is represented by a polygonal mesh as shown in FIG. 7 and arranging the mesh data of the analysis model in a three-dimensional space will be described. However, the process is the same when a node is used as an element of the analysis model.

  FIG. 7 shows an arrangement of meshes forming an analysis model. A mesh A having nodes a, d, e, and h is combined with a mesh B having nodes a, b, c, and d, and nodes d, c, and d. An example is shown in which a mesh C having f, g, a mesh D having nodes e, g, h, and a mesh F having nodes a, h,. An adjacent mesh is a mesh that shares nodes or sides with a certain mesh. When attention is paid to other than mesh A, mesh E is adjacent to mesh F and mesh B, mesh G is adjacent to mesh D, mesh Meshes H and I are adjacent to C.

  The analysis model formed by such a mesh has, for example, a data structure as shown in FIGS. 8 and 9, and each mesh has a mesh number for identifying itself, a node number, an adjacent mesh. , Node coordinate values (coordinate values in an XYZ orthogonal coordinate system in a three-dimensional space), mesh attributes, and other data. Various data necessary for these simulation processes are stored in the external storage device 13. For example, the external storage device 13 has a database composed of attribute record groups to which individual identification numbers (record numbers) are assigned for each object, and each attribute record includes a mesh number and a node point. Coordinate values, attribute data, and the like are described in association with each other.

  Note that the XYZ orthogonal coordinate system in the data structure of the analysis model is a coordinate system fixed to the analysis target, and the Z-axis is in the direction of gravity (the direction opposite to gravity) when the body 20 to be analyzed is horizontal. Set in advance.

  The liquid pool determination unit 10b has an attribute of a gas corresponding to a location where the immersion liquid is discharged and exposed directly or indirectly (via an adhesion film or the like) to the individual meshes forming the analysis model. And the attribute of the liquid corresponding to the location where the immersion liquid remains and is stored are determined. As for the attribute of this mesh, all meshes are initially set to the liquid attribute (immersion state), and then the mesh attribute becomes gas or liquid by comparing the height in the gravity direction with the adjacent mesh including the boundary mesh. Whether or not it is a liquid pool is determined, and when it is determined to be gas, the attribute of the mesh is changed to gas and the attribute data is rewritten.

  The boundary mesh is used as an initial condition for separating and determining the attributes of all meshes of the analysis model into liquid and gas. Prior to the process of determining the attributes of each mesh, the boundary mesh is determined in advance. Element. In this embodiment, the boundary mesh searches for a mesh having a free edge from all meshes forming the analysis model, and sets the mesh having the free edge as a boundary mesh.

  Free edge means the edge part of the workpiece, that is, the edge part of the workpiece or the edge of the hole formed in the workpiece, and the part where liquid is discharged unconditionally when the workpiece is pulled up from the immersion state. is there. In other words, a free edge is an edge (side) belonging to only a single element (mesh) that is not shared by a plurality of elements, and is a discontinuous portion in which elements are not connected to each other, It is the part that is open to the space (that is, the part where the immersion liquid is always discharged). In the example shown in FIG. 7, since the nodes b and c of the mesh B are not shared by any other mesh, the edge (bc) is a free edge, and the mesh B having this free edge is a boundary mesh. Is initialized as

  When determining the liquid pool in the work immersion process, as described above, the opening serving as the discharge hole from the liquid pool is previously covered with a mesh corresponding to the hole on the analysis model. Alternatively, the holes are closed by, for example, creating an analysis model using drawing data without liquid discharge holes from the beginning.

  The determination of the liquid pool basically assumes that the specific gravity of the immersion liquid is larger than the specific gravity of air. That is, when determining the attribute of a certain mesh, the determination target mesh and the comparison target mesh are compared with each other in the height opposite to the gravity. If the comparison target mesh has a gas attribute lower than that of the determination target mesh, it is determined that the immersion liquid is discharged without staying in the relatively high determination target mesh, and the determination target mesh The attribute data is gas.

  On the other hand, if the attribute of the relatively low comparison target mesh is liquid, the attribute data of the determination target mesh is not changed, and the comparison is changed and the determination is repeated. Then, this determination is repeated and the attributes of all meshes are separated and determined into liquid and gas, and the gas-liquid boundary line of the liquid reservoir indicated by the presence of the mesh whose attribute is determined as liquid is derived.

  In addition, when determining the liquid pool and calculating the liquid volume, assuming that the body 20 to be analyzed is pulled up from the immersion tank 22 at an inclination angle θ, the Z axis of the XYZ orthogonal coordinate system is centered on the Y axis. The coordinates are rotated by an inclination angle θ.

The liquid volume calculation unit 10c is formed by correcting the function of the liquid volume calculation step in the liquid pool simulation of the present invention, that is, by modifying the boundary between the element whose attribute is determined to be gas and the element whose attribute is determined to be liquid. The liquid pool volume is calculated based on the horizontal liquid surface area and the height of the liquid surface in the direction of gravity. Specifically, with respect to the mesh forming the liquid reservoir, a horizontal plane passing through the node having the lowest height in the direction opposite to the gravity in the boundary line of the liquid reservoir is set, as shown in the following formula (1): Then, the projected area Smi and the height hmi of each mesh on the horizontal plane are obtained to calculate the volume Vmi, and the volume Vmi for each mesh is summed to calculate the volume V of the entire liquid reservoir.
V = ΣVmi = Σ (Smi × hmi) (1)

  That is, as shown in FIG. 10, the liquid reservoir formed by the mesh MSHLq whose attribute is determined as liquid is detected as a boundary between the liquid level line and the mesh MSHa of the gas attribute, It becomes a jagged boundary line. Therefore, in the calculation of the volume of the liquid reservoir, a horizontal plane that passes through the node having the lowest height in the direction opposite to the gravity is set, and the mesh whose all nodes are higher than the horizontal plane is changed from gas reservoir to its attribute by changing its attribute to gas. The volume for each mesh is calculated by determining the height (liquid level height) hmi to the horizontal plane of each mesh as shown in FIG.

Assuming that the Z-axis of the XYZ Cartesian coordinate system is oriented in the direction of gravity (the direction opposite to gravity) for convenience, the liquid level height hmi of each mesh is the Z-coordinate value of the horizontal plane as shown in the following equation (2). A value obtained by averaging the differences between Zh and the Z coordinate values Z1, Z2,... Of n nodes, or a representative point (center of gravity, inner center, centroid, etc.) of the target mesh from Pi to the horizontal plane Given.
hmi = ((Z1-Zh) + (Z2-Zh) + ...) / n (2)

  In this case, for a mesh in which only some of the nodes are higher than the horizontal plane, an intermediate node that crosses the horizontal plane is added between a node above the horizontal plane and a node below the horizontal plane, and the liquid level is divided. Calculate the volume of the part below the divided liquid level. For example, as shown in FIG. 12, when a mesh having four nodes N1 to N4 is on the boundary line, an additional position of the intermediate node is determined according to the number of certain nodes above the horizontal plane, The volume below the liquid level is determined from the area of the region formed by the nodes below the horizontal plane and the height from the center of gravity of the region to the liquid level.

  In the example shown in FIG. 12A, the nodes N1 and N2 are higher than the horizontal plane, and the node N4 connected to the node N1 and the node N3 connected to the node N2 are below the horizontal plane. In this case, an intermediate node Ad1 crossing the horizontal plane is added between the node N1 and the node N4, and an intermediate node Ad2 crossing the horizontal plane is added between the node N2 and the node N3. Then, the volume under the liquid surface is calculated based on the area of the region formed by the nodes N3, N4, Ad1, and Ad2 and the height from the center of gravity of the region to the liquid surface.

Note that the coordinate values (xa1, ya1, za1) and (xa2, ya2, za2) of newly added intermediate nodes Ad1, Ad2 are the coordinate values (x1, y1, z1), (x2) of the existing nodes. , y2, z2), (x3, y3, z3), (x4, y4, z4) can be obtained by the following equations (3) and (4).
(Xa1, ya1, za1) = ((z1−za1) × (x4−x1) / (z1−z4) + x1, (z1−za1) × (y4−y1) / (z1−z4) + y1, Zh) (3)
(Xa2, ya2, za2) = ((z2−za2) × (x3−x2) / (z2−z3) + x2, (z2−za2) × (y3−y2) / (z2−z3) + y2, Zh) (4)

  On the other hand, in the example shown in FIG. 12B, the node N2 is higher than the horizontal plane, the node N1 connected to the node N2, the node N3 connected to the node N2, and the node N4 connected to the node N1 and the node N3 Below the horizontal plane. In this case, an intermediate node Ad1 is added between the node N2 and the node N1, and an intermediate node Ad2 is added between the node N2 and the node N3. These nodes N1, Ad1, Ad2, N3, N4 By calculating the area of the region formed by the above, the volume under the liquid level is calculated.

In this case, the coordinate value of one intermediate node Ad2 can be given by the same equation (4) as described above, but the coordinate value of the other intermediate node Ad1 is given by the following equation (5).
(Xa1, ya1, za1) = ((z2−za1) × (x1−x2) / (z2−z1) + x1, (z2−za1) × (y1−y2) / (z2−z1) + y1, Zh) (5)

Furthermore, in the example shown in FIG. 12C, only the node N4 is below the horizontal plane. In this case, an intermediate node Ad1 is added between the node N1 and the node N4, and the nodes N3 and N4 The intermediate node Ad2 is added between the two, and the area of the region formed by these nodes Ad1, Ad2, and N4 is obtained to calculate the volume under the liquid level. In this case, the coordinate value of the intermediate node Ad1 is given by the aforementioned equation (3), and the coordinate value of the intermediate node Ad2 is given by the following equation (6).
(Xa2, ya2, za2) = ((z3−za2) × (x3−x4) / (z2−z3) + x4, (z3−za2) × (y3−y4) / (z2−z3) + y4, Zh) (6)

  The liquid discharge time calculation unit 10d determines the function of the liquid discharge time calculation step in the liquid pool simulation of the present invention, that is, the liquid discharge time during which the liquid corresponding to the liquid volume is discharged from the liquid pool, based on the workpiece transport conditions. It has a function to calculate. Specifically, as a simulation of liquid discharge when the workpiece is lifted from the immersion tank, the time until the bottom (discharge hole) of the liquid reservoir is exposed on the surface of the immersion liquid, and the bottom of the liquid reservoir Calculate the time for the residual liquid to be exposed on the surface of the immersion liquid and discharged from the discharge hole based on the posture of the workpiece, the conveyance speed, the volume of the liquid pool, the discharge flow rate per unit time from the discharge hole, etc. .

In this embodiment, a description will be given assuming that one discharge hole is provided in one liquid reservoir. As shown in FIG. 13, the time T1 until the bottom (discharge hole) of the liquid reservoir is exposed on the liquid surface of the immersion liquid is set to hH1 from the bottom of the immersion tank 22 to the discharge hole of each liquid reservoir. , HH2 (represented as hHi as a representative), it can be obtained by the following (7) from the liquid level height LiqH of the immersion liquid, the pitch speed VL and the inclination angle θ in the conveyance of the vehicle body 20.
T1 = (LiqH−hHi) / sin θ / VL (7)

Moreover, the liquid discharge time T2 after the bottom part (discharge hole) of the liquid reservoir part is exposed on the surface of the immersion liquid is the liquid reservoir volume of each liquid reservoir part as V1, V2 (typically described as Vi). Assuming that the discharge flow rate per unit time from the discharge hole of each liquid reservoir is LiqV1 and LiqV2 (typically described as LiqVi), the following equation (8) can be obtained.
T2 = Vi / LiqVi (8)

  The sum of the above times T1 and T2 is obtained as the liquid discharge time, but strictly speaking, the liquid volume Vi when calculating the liquid discharge time T2 changes (decreases) over time. In this embodiment, the liquid reservoir volume Vi is approximately constant at an initial value in the transport state in which the vehicle body 20 is pulled up at the inclination angle θ, and in the transport state in which the body 20 moves horizontally along the transport path 22c, It is assumed that the value is decreased from the initial value by the amount discharged in the conveying state at the inclination angle θ.

  Furthermore, the liquid discharge time calculation unit 10d is based on the time during which the work is lifted from the immersion tank in which the work is immersed and transported to the set position and the liquid discharge time of the liquid pool in the liquid pool simulation of the present invention. It has a function of a determination step for determining whether or not the liquid can be stored, and determines whether the liquid discharge state from the liquid pool is “OK” or “NG”. In this determination, first, the entire body volume Vi is discharged before the vehicle body 20 is lifted at the inclination angle θ and shifted to the horizontal movement along the conveyance path 22c, that is, during the conveyance time at the inclination angle θ. Check whether or not. When all of the liquid volume Vi is discharged before the horizontal movement, the discharge time calculated by the above equations (7) and (8) is notified together with “OK” determination.

  On the other hand, if the liquid pool volume Vi cannot be completely discharged before the horizontal movement, it is further determined whether or not the liquid pool volume Vi is discharged before reaching the deadline DL of the transport path 22c. When the liquid volume Vi is discharged before reaching the deadline DL, the discharge time is notified together with “OK” determination, and when the liquid volume Vi is not discharged until the deadline DL is reached, “NG”. The discharge time is notified together with the determination.

  In addition, when there are a plurality of discharge holes in one liquid reservoir, an identification number is assigned to each discharge hole, and the above processing is sequentially performed from, for example, the discharge hole at the highest position.

  The post processing unit 10e performs visualization processing for enabling easy understanding of the simulation result and data output of the simulation result. In the visualization process of simulation results, the mesh determined as the liquid attribute, the mesh determined as the gas attribute, and the boundary lines of these are classified by hue, shade, etc., and the location and size of the liquid pool are clearly indicated And a determination result for the liquid discharge state from the liquid reservoir is notified.

  Next, a liquid pool simulation process executed by the CPU of the arithmetic unit 10 will be described with reference to the flowcharts of FIGS. Note that this simulation process assumes that the vehicle body 20 is immersed in the immersion tank 22 described above.

  The simulation program of FIG. 14 is a program for determining the presence or absence of a liquid pool. First, in step S1, the surface shape of the object is modeled with data of a plurality of surface elements, and an analysis model for numerical calculation is constructed. . This analysis model is constructed by, for example, a model obtained by dividing the surface shape of a workpiece with a plurality of triangular meshes.

  Next, it progresses to step S2, and as a simulation of the state where the target object was immersed in the electrodeposition liquid etc., all the meshes of an analysis model are once set to the attribute of a liquid. In step S3, a mesh having a free edge is searched as an initial mesh for separating the attributes of all meshes into liquid and gas, and in step S4, the attribute of the mesh having a free edge is changed from liquid to gas. .

  Next, proceeding to step S5, the direction of gravity with respect to the workpiece and the line angle θ (inclination angle along the side wall of the immersion bath 22) when lifting the workpiece from the immersion bath 22 are specified. As a simulation of tilting up by an angle θ, the three-dimensional coordinate system fixed to the vehicle body 20 is rotated by an angle θ about the Y axis so that the Z axis is inclined by an angle θ with respect to the direction of gravity.

  After step S7, a liquid pool determination calculation process corresponding to the determination step of the present invention is performed. This liquid pool determination calculation process is a process for determining the occurrence of a liquid pool by determining the respective attributes by comparing the height of each mesh in the direction opposite to the gravity, and a conventional method can be used.

  That is, in step S7, the height in the direction opposite to the gravity is compared between a mesh (air mesh) whose attribute is gas and a mesh (liquid mesh) whose attribute is adjacent to this air mesh. The comparison of the height of each mesh is, for example, the position in the opposite direction of gravity, such as the center of gravity, inner center, outer center, and centroid of each mesh, and the highest vertex among the vertices of each mesh. This is done by comparing feature points such as.

  The height in the direction opposite to gravity is a value obtained by correcting the Z coordinate value of each mesh with the tilt angle θ. However, since the tilt angle θ is constant, here, the height is compared with the Z coordinate value, and in step S8 It is checked whether the Z coordinate value of the air mesh is equal to or less than the Z coordinate value of the adjacent liquid mesh. As a result, if the liquid mesh is located below the air mesh, the process jumps from step S8 to step S10 without changing the attribute of the liquid mesh, and if the liquid mesh is located above the air mesh, In step S9, the attribute of the liquid mesh is changed from liquid to gas to form an air mesh, and the process proceeds to step S10.

  In step S10, the mesh attribute information is recorded, and in step S11, it is checked whether or not the attribute change determination for all the liquid meshes has been completed and no further attribute change is possible. If the determination process for all the liquid meshes has not been completed yet and there is room for changing the attribute, the process returns from step S11 to step S7 and the above determination process is continued, and the attribute change is impossible any more. If there is, the process proceeds from step S11 to step S12 to check whether the liquid mesh is zero.

  As a result, when the liquid mesh is zero, the process proceeds from step S12 to step S13, it is determined that there is no liquid accumulation, and a simulation result is displayed on the display device 12 to notify that there is no liquid accumulation. In addition, if necessary, the simulation result data is output to a file. On the other hand, if the liquid mesh is not zero, the process proceeds from step S12 to step S14, where it is determined that there is a liquid reservoir, and notification is made via the display device 12 and the volume Vi of each liquid reservoir is calculated.

  When it is determined that there is a liquid pool in the above program, the state of liquid discharge from the liquid pool is checked to determine whether it is “OK” or “NG”. Next, a liquid pool discharge determination program for performing this determination will be described with reference to the flowchart of FIG.

  In the liquid pool discharge determination program of FIG. 15, first, in the first step S21, the liquid pool number i, the liquid pool volume Vi, the liquid level height LiqH of the immersion tank 22, and the discharge holes of the respective liquid storage sections from the bottom of the immersion tank 22 The liquid accumulation data such as the height hHi is input.

Next, the process proceeds to step S22, and the following equation (9) indicates whether or not the liquid pool volume Vi is completely discharged in the stroke in which the vehicle body 20 is pulled up along the side wall of the immersion tank 22 at the inclination angle θ. Judgment is made based on whether or not the condition is satisfied. The condition of the formula (9) is a condition in which the volume of the liquid discharged with the discharge hole exposed on the immersion liquid surface is equal to or larger than the liquid pool volume Vi. Specifically, the conveyance start position at the inclination angle θ. In the time L1 / VL required to move the conveyance distance L1 with zero as the zero point, the vertical height of the vehicle body in the vertical direction (L1 × sin θ) and the total upward distance (L1 × sin θ) indicate that the discharge hole is on the immersion liquid surface. Is a condition in which the amount of liquid discharged in a time multiplied by the ratio of the distance excluding the ascending distance (LiqH-hHi) until it is exposed to is equal to or greater than the liquid pool volume Vi.
L1 / VL × (L1 × sin θ− (LiqH−hHi)) / (L1 × sin θ) × LiqVi ≧ Vi (9)

  As a result, when the condition of the expression (9) is satisfied, the process proceeds from step S22 to step S28, the liquid discharge time T for completing the discharge of the liquid pool volume Vi is calculated, and discharged together with the “OK” determination in step S29. Announce time. The liquid discharge time T is exposed to the time T1 when the discharge hole is below the liquid level as shown in the above equation (7), and the discharge hole is exposed on the liquid surface of the immersion liquid as shown in the equation (8). This is the time obtained by adding the discharge time T2 from the beginning.

On the other hand, if the condition of the formula (9) is not satisfied, the process proceeds from step S22 to step S23, and as shown in the following formula (10), the liquid pool volume Vi corresponding to the amount discharged in the transport stroke at the inclination angle θ. Decrease / update The decrease in the liquid pool volume Vi is the value on the left side of the equation (9), that is, the volume of the liquid discharged with the discharge holes exposed on the immersion liquid surface. Hereinafter, the liquid pool volume Vi whose decrease has been updated is referred to as a remaining volume Vi for the sake of convenience and is distinguished from the initial value.
Vi = Vi−L1 / VL × (L1 × sin θ− (LiqH−hHi)) / (L1 × sin θ) × LiqVi (10)

Next, proceeding to step S24, whether or not the amount of discharged liquid until the deadline DL is reached by the horizontal movement of the vehicle body 20 is greater than or equal to the remaining volume Vi, whether or not the condition of the following equation (11) is satisfied. to decide.
L2 / VL × LiqVi ≧ Vi (11)

Then, when the condition of the expression (11) is satisfied, the process proceeds from step S24 to step S25, and as shown in the following expression (12), the remaining volume Vi is obtained by horizontal movement during the conveyance time L1 / VL at the inclination angle θ. The liquid discharge time T is calculated by adding the discharge time Vi / LiqVi, and the discharge time is notified together with the “OK” determination in step S29 described above. On the other hand, if the condition of the expression (11) is not satisfied, the process proceeds from step S24 to step S26. Similarly, the liquid discharge time T is calculated by the expression (12), and the liquid discharge time is determined together with the “NG” determination in step S27. Is notified.
T = L1 / VL + Vi / LiqVi (12)

  As described above, according to the present embodiment, using an analysis model obtained by dividing a work to be dipped with a plurality of element data, whether or not there is a liquid pool from the attribute of each element determined based on the positional relationship in the direction of gravity Determine. If there is a liquid pool, the volume of the liquid pool is defined by the area of the horizontal liquid surface formed by correcting the boundary between the element whose attribute is determined to be gas and the element whose attribute is determined to be liquid, and After calculating based on the height of the liquid surface in the direction of gravity, the discharge time of the liquid pool volume is calculated based on the workpiece transfer condition to determine whether it is “OK” or “NG”.

  As a result, the simulation can be applied to a relatively small system without requiring complicated fluid analysis, and whether or not the liquid pool generated in the work to be immersed and the discharge hole of the liquid pool is appropriate. It is possible to make a determination, and it is possible to flexibly cope with a model change due to a design change.

Basic configuration diagram of the simulation device Schematic illustration of the car body painting line Explanatory drawing showing the state of the car body in the painting line Explanatory drawing showing the liquid reservoir of the vehicle body Explanatory drawing showing the liquid pool surface in the horizontal state Explanatory drawing showing the liquid pool surface in an inclined state Explanatory drawing showing the mesh arrangement of the numerical calculation model Explanatory diagram showing the relationship between meshes in the data structure of the numerical calculation model Explanatory drawing showing the node number and coordinate data of the data structure of the numerical calculation model Explanatory drawing showing an example of expressing the liquid reservoir with a numerical calculation model Explanatory drawing showing the volume calculation method of the liquid reservoir Explanatory drawing showing the calculation method of liquid level height Explanatory drawing which shows the calculation method of the liquid discharge time from the liquid reservoir of the vehicle body Flowchart of pool simulation program Flow chart of liquid discharge judgment program

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Simulation apparatus 10 Arithmetic apparatus 10a Model construction part 10b Liquid pool determination part 10c Liquid pool volume calculation part 10d Liquid discharge | emission time calculation part

Claims (8)

The computer models the work to be dipped with data of multiple elements, and the computer determines whether the attribute of each element is gas or liquid based on the positional relationship in the direction of gravity, and the dipping liquid pool is determined. In the simulation method of the liquid pool to be simulated,
The liquid volume of the liquid stored in the liquid reservoir, the area of the horizontal liquid surface formed by correcting the boundary between the element whose attribute is determined to be gas and the element whose attribute is determined to be liquid, and A liquid volume calculation step for calculating based on the height of the liquid surface in the direction of gravity;
The liquid discharge time during which the volume of liquid is discharged from the liquid pool until the work is pulled up from the immersion tank in which the work is immersed and the bottom of the liquid pool is positioned on the liquid level of the immersion tank. And a liquid discharge time calculating step for calculating a time obtained by adding the time of the liquid pool and the time during which the volume of liquid is discharged from the liquid pool in a state where the bottom of the liquid pool is located on the liquid level of the immersion tank ; A method of simulating a liquid pool, comprising:   Furthermore, a determination step for determining whether or not the liquid pool is possible is provided based on a time during which the work is lifted from the immersion tank in which the work is immersed and conveyed to a set position, and a liquid discharge time of the liquid pool. The method for simulating a liquid pool according to claim 1. In the liquid volume calculation step,
For each element of the liquid attribute, calculate the volume based on the liquid level area of each element and the height from the representative point of each element to the liquid level, and add the calculated volume of each element to add the above liquid pool. 3. The liquid pool simulation method according to claim 1, wherein the volume is obtained.   The set position is set in the transfer path between the multiple immersion tanks corresponding to multiple immersion processes, and the immersion liquid stored in the previous immersion tank can be collected without mixing in the subsequent immersion tank. The liquid pool simulation method according to claim 2, wherein the deadline is used. A computer that models the work to be dipped with data of multiple elements and determines whether the attribute of each element is gas or liquid based on the positional relationship in the direction of gravity, and simulates a pool of dipping liquid In an executable liquid pool simulation program,
The liquid volume of the liquid stored in the liquid reservoir, the area of the horizontal liquid surface formed by correcting the boundary between the element whose attribute is determined to be gas and the element whose attribute is determined to be liquid, and A liquid volume calculation step for calculating based on the height of the liquid surface in the direction of gravity;
The liquid discharge time during which the volume of liquid is discharged from the liquid pool until the work is pulled up from the immersion tank in which the work is immersed and the bottom of the liquid pool is positioned on the liquid level of the immersion tank. And a liquid discharge time calculating step for calculating a time obtained by adding the time of the above and the time during which the volume of liquid is discharged from the liquid reservoir in a state where the bottom of the liquid reservoir is positioned on the liquid surface of the immersion tank ; A liquid pool simulation program characterized by comprising:   Furthermore, a determination step for determining whether or not the liquid pool is possible is provided based on a time during which the work is lifted from the immersion tank in which the work is immersed and conveyed to a set position, and a liquid discharge time of the liquid pool. The liquid pool simulation program according to claim 5. In the liquid volume calculation step,
For each element of the liquid attribute, calculate the volume based on the liquid level area of each element and the height from the representative point of each element to the liquid level, and add the calculated volume of each element to add the above liquid pool. The liquid pool simulation program according to claim 5 or 6, wherein the volume is obtained.   The set position is set in the transfer path between the multiple immersion tanks corresponding to multiple immersion processes, and the immersion liquid stored in the previous immersion tank can be collected without mixing in the subsequent immersion tank. The liquid pool simulation program according to claim 6, wherein a deadline is used.

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