JP2012202914A - Air-tightness evaluation method of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air-tightness evaluation method of a vehicle with which a ventilation part of a ventilation route in which a work load is low and unknown can be visualized using CAD data.SOLUTION: An air-tightness evaluation method includes steps S2, S3 and S4 of creating a fluid analysis model in which a number of particles are installed within an evaluation space, the particles being affected one another by momentum, a momentum application section preparation step S5 of creating a momentum application section capable of applying the momentum to the evaluation space, a condition setting step S6 of setting an application condition of the momentum, an arithmetic step S7 of arithmetically operating a momentum transfer route by iteratively searching for a route in which the momentum is transferred from at least partial particles to which the momentum is applied from the momentum application section, to nearby particles, respectively, by performing fluid analysis on the at least partial particles, and a display step S8 of displaying a gap of a ventilation route on a display device on the basis of a momentum transfer route which is communicated to the outside of the evaluation space, in the momentum transfer route.

Description

  The present invention relates to a vehicle airtightness evaluation method, and more particularly, to a vehicle airtightness evaluation method capable of displaying a ventilation portion of a ventilation path connected from the inside of a vehicle to the outside based on CAD data of a vehicle member.

Conventionally, the airtightness evaluation of a vehicle is performed by injecting pressurized air into the vehicle interior from the opened window part in a state where a part of the window part of the vehicle is opened and the remaining window parts are sealed, and from the sealed window part. Air leaks were detected based on the presence or absence of smoke swaying smoke or soapy water bubbles to evaluate the sealing performance of the vehicle.
An airtight inspection apparatus for a vehicle described in Patent Document 1 includes a gas injection means for injecting an inspection gas different from air into a vehicle interior, and a seal that covers a measurement point set in a window portion from the outside of the vehicle in an airtight state. Gas detection means comprising a gas detection unit capable of detecting a test gas existing inside the sealing unit, and a change in the pressure of the test gas detected by the gas detection unit Is used to detect the inspection gas leaked from the inside of the vehicle to the outside of the vehicle.

  In the vehicle airtight inspection device of Patent Document 1, a plurality of measurement points are set for a completed vehicle that has actually completed the assembly of vehicle parts, and the airtightness evaluation is performed at these measurement points. However, as computer computing power advances, simulations such as vehicle design, structural analysis, and performance evaluation are performed at the vehicle design stage using analysis tools such as CAD (Computer Aided Design) and CAE (Computer Aided Engineering). It is done virtually. One such simulation technique is CFD (Computational Fluid Dynamics), which solves equations related to fluid motion by a computer. With this CFD, the motion of a fluid that is a continuum can be numerically analyzed on a computer.

In general, in fluid simulation by CFD, a space to be evaluated is divided into grid-like analysis elements, and then a variable such as speed is given to a node of the grid, a finite difference method, a finite volume method, or the like. The analysis by the grid method is used, and it is performed according to the following procedure.
(I) Create a three-dimensional or two-dimensional shape model that reproduces the shape to be evaluated.
(Ii) A fluid analysis model that represents a shape model with a calculation grid (mesh or grid) composed of a plurality of nodes and grid lines is created.
(Iii) Discrete fluid equations such as Navier-Stokes for each calculation grid to calculate approximate solutions.
(Iv) Visualize analysis results such as flow velocity, pressure, and pressure distribution.
Thereby, the time series change is visually analyzed about the motion of the fluid which is a continuum.

  The air flow simulation method in the factory building described in Patent Document 2 is based on a three-dimensional model obtained by dividing the shape data of the factory building into a mesh, and a plurality of opening positions of the building, the air flow rate of these openings, and heat generation Source, the amount of heat released from the heat source, the dust generation source, and the dust generation amount from the dust generation source, respectively, and the thermal fluid equation of this three-dimensional model is discretized using the finite volume method, Time series changes are predicted for the absolute dust concentration distribution.

  In recent years, in the field of simulation, a particle method is known in which a fluid analysis model is created using a target object as a collection of particles, and a fluid equation is discretized based on the fluid analysis model. This particle method is typified by the MPS (Moving Particle Semi-implicit) method and the SPH (Smoothed Particle Hydrodynamics) method. A large number of particles are arranged in the evaluation target space, and each of these many particles has variables such as velocity. I have.

JP 2006-153803 A JP 11-63622 A

  In the airtightness inspection apparatus for a vehicle disclosed in Patent Literature 1, after a completed vehicle is arranged at an experimental site, an experimental staff predicts in advance a vehicle portion that may have a poor sealing performance based on experience, and measures the predicted vehicle portion. Airtight inspection is performed as a part. Therefore, the vehicle portion that is not predicted by the experimental staff is not subjected to the airtight inspection itself, and there is a possibility that no countermeasure is taken against the poor sealing performance. In addition, even if a poor sealability of the vehicle part, which is the measurement location, is detected by inspection, there is a concern that the vehicle development period will be prolonged and the development cost will increase because it involves a change in the design of the body structure and parts structure of the completed vehicle. Is done.

  As in the air flow simulation method of Patent Document 2, it is possible to create a vehicle shape model by combining three-dimensional data of vehicle members at the vehicle design stage, and create a fluid analysis model from this shape model. However, even if any of the finite element method, the finite difference method, and the finite volume method is used, a calculation grid formed by a plurality of nodes and grid lines connecting the nodes is used as the evaluation target space. Since it is necessary to divide the shape model into meshes, there is a possibility that the work load for creating the optimum calculation grid may be enormous in order to obtain an appropriate analysis result.

  In addition, when the evaluation target is divided by the calculation grid, the evaluation target to be analyzed needs to form a closed space closed to the outside, and thus the evaluation target is subjected to wrapping processing. In other words, when airtightness evaluation is performed such as a poor sealing performance of a vehicle, the vehicle interior space to be evaluated is simulated by lapping even though it is for the purpose of inspecting the leakage of air from the vehicle interior space to the outside. Therefore, the ventilation path communicating between the inside and outside of the vehicle is eliminated from the fluid analysis model. In other words, when performing airtightness evaluation using the lattice method, the air flow path can be evaluated only in an evaluation space in which an operator intentionally sets an opening as an air leak location in the fluid analysis model, and the shape at the design stage It is difficult to detect a ventilation path that the operator is not aware of using the model.

  An object of the present invention is to provide a vehicle airtightness evaluation method that uses a CAD data to visualize a ventilation portion of an unknown ventilation path with a low work load.

  The vehicle airtightness evaluation method according to claim 1 is the vehicle airtightness evaluation method, wherein a shape model including an evaluation space that is a target space for airtightness confirmation is created by combining CAD data of vehicle members, A model creation step for creating a fluid analysis model in which a large number of particles that influence each other in the evaluation space are installed, and a momentum grant creation step for creating a momentum grant unit that can impart momentum to the evaluation space; A condition setting step for setting the momentum application condition, and fluid analysis of at least some of the particles to which the momentum is applied from the momentum imparting unit, whereby the momentum is transmitted from the at least some particles to neighboring particles, respectively. Calculating a momentum transmission path by repeatedly searching for a path to be performed, and out of the evaluation space of the momentum transmission path Based on the momentum transfer path leading is characterized by comprising a display step of displaying a vent of the vent path, the.

  In this vehicle airtightness evaluation method, the fluid analysis model is created by installing a large number of particles that affect each other due to momentum in the evaluation space of the shape model combining the CAD data of the vehicle members. The evaluation space wrapping process and calculation grid creation can be omitted in the previous stage.

The invention of claim 2 is characterized in that, in the invention of claim 1, the display step displays the gas flow rate moving through the ventilation path on the display unit.
According to a third aspect of the invention, in the first or second aspect of the invention, the display step visualizes the ventilation path and displays it on the display unit.
According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, after the display step, CAD data of a vehicle member provided with the ventilation portion is corrected.

According to the first aspect of the present invention, since the evaluation space wrapping process and calculation grid creation are omitted in the previous stage of the arithmetic processing, the work load in the airtightness evaluation can be reduced.
In addition, since many particles that affect each other due to momentum are installed in the evaluation space, the momentum is transmitted from at least some of the particles to neighboring particles even in unknown ventilation passages and evaluation target spaces that the operator is not aware of. The momentum transmission path to be performed can be calculated. Moreover, the ventilation portion of the ventilation path can be displayed based on the calculated momentum transmission path based on the momentum transmission path connected to the outside of the evaluation space. Therefore, it is possible to visualize the ventilation portion of the unknown ventilation path at the design stage, and to recognize the gap between the vehicle members.

According to the invention of claim 2, since the gas flow rate is displayed, the soundproof performance and the seal performance of the vehicle can be evaluated.
According to the invention of claim 3, it is possible to accurately grasp the ventilation path that leads to the outside of the evaluation space.
According to the invention of claim 4, the noise and water leakage of the vehicle can be improved at the design stage.

It is a hardware block diagram of the vehicle airtightness evaluation method which concerns on Example 1 of this invention. It is a functional block diagram of the airtightness evaluation method of vehicles. It is a flowchart which shows the procedure of the airtightness evaluation method of a vehicle. It is a figure which shows the display screen of a shape model creation step. It is a figure which shows the display screen of an evaluation space creation step. It is the figure which abbreviate | omitted a part of partition wall of FIG. It is a figure which shows the display screen of a fluid analysis model creation step. It is a schematic diagram which shows the momentum transmission path | route between particle | grains. It is a figure which shows the display screen of a condition setting step. It is a figure which shows the display screen which looked at the evaluation space from the side. It is a figure which shows another display screen which looked at the evaluation space from the side. It is a figure which shows the display screen which looked at evaluation space from diagonally back.

  Hereinafter, modes for carrying out the present invention will be described based on examples.

Hereinafter, Example 1 of the present invention will be described with reference to FIGS.
As shown in FIGS. 1 and 2, the vehicle airtightness evaluation method according to the present embodiment includes a computer main body 1, an input device such as a keyboard 2 and a mouse 3, and a display device 4 such as a liquid crystal display (LCD) panel ( Display unit), auxiliary storage device 5 such as a hard disk (HDD), and hardware such as a storage device 6 that stores three-dimensional CAD data (hereinafter referred to as CAD data) of various vehicle members such as side doors and frames. It is realized by. Peripheral devices 2 to 6 are electrically connected to the computer main body 1.

  As shown in FIG. 2, the computer main body 1 includes a CPU that executes arithmetic processing, a ROM that stores a program for executing processing steps to be described later, a RAM as a work area that temporarily holds various data, An I / O circuit for exchanging data with the devices 2 to 6 is provided. The computer main body 1 writes the CAD data collected by the operator's operation input into the RAM and executes each processing step. By connecting a printer to the computer main body 1, CAD data and evaluation results can be printed out.

Based on the flowchart of FIG. 3 and FIGS. 4 to 12, the processing procedure of this evaluation method will be described.
First, CAD data of vehicle members constituting the evaluation object is collected (S1).
CAD data of a plurality of vehicle members is created using CAD software. These CAD data are collected by the operator from the storage device 6 via the input devices 2 and 3 and the display device 4 and stored in the auxiliary storage device 5. The computer main body 1 writes the CAD data of the vehicle member collected by the operator's operation input in the RAM.

Next, the shape model 10 is created by combining the collected CAD data (S2).
As shown in FIG. 4, the operator creates a shape model 10 having a space to be evaluated such as a front part of the vehicle and a side door by combining the collected CAD data with reference to the display screen of the display device 4. To do. In the present embodiment, in order to describe an example of airtightness evaluation using the left front portion of a vehicle formed by a plurality of vehicle members as an evaluation space 11, a shape model 10 including the evaluation space 11 as an evaluation target space is created. ing.

After creating the shape model 10, a simulation space 12 for executing a simulation is created from the shape model 10 including the evaluation space 11 (S3).
As shown in FIGS. 5 and 6, the shape model 10 is partitioned by six virtual partition walls 13 to 18 formed in the vertical and horizontal directions, thereby forming a cubic simulation space 12. The simulation space 12 includes an evaluation space 11 therein and forms a closed space that is blocked from outside the partition walls 13 to 18. This shortens the calculation time and reduces the work load.

  Next, as shown in FIG. 7, a fluid analysis model 20 in which a large number, for example, 2 million to 5 million virtual particles P are installed in the simulation space 12 is created (S4). In the fluid analysis model 20 of the present embodiment, the air in the simulation space 12 is modeled without performing a wrapping process using a particle method that discretizes the dynamics of the fluid into the motion of the particles P. S2, S3, and S4 correspond to the model creation step of the present invention.

Here, the basic concept of the search mechanism of the present invention will be described with reference to FIG.
In the particle method, a large number of virtual particles are arranged in a so-called space whose coordinates change in the space, and variables such as velocity are secured as an array in these particles.
As shown in FIG. 8, by solving a fluid discretization governing equation for a predetermined particle, for example, the particle P1, a neighboring particle existing within the influence radius re, for example, the nearby particles P2, P3, etc., is between these particles. A relational expression of momentum transmission is created.
That is, in the particle P1, the particles P2, P3 and the like existing in the space having the influence radius re are affected, and the particle P4 separated from the influence radius re is not affected. Therefore, the momentum of the particle P1 is transmitted to the detected nearby particles P2, P3, etc., as a result of the nearby particle influence determination. In the figure, L1 to Ln and K1 to Km indicate paths through which the influence between particles is transmitted.

In the particle P2 affected by the particle P1, the particles P5, P6, etc. existing in the space of the influence radius re are assumed to be affected, and the particle P7 separated from the influence radius re is not affected. Is done. The momentum of the particle P2 is transmitted to the detected nearby particles P5, P6, and the like as a result of determining the influence of the nearby particles. The same neighboring particle influence determination is performed for the particles P3 other than the particles P2 that are the neighboring particles of the particle P1. In the particle P5 affected by the particle P2, the particle P8 and the like existing in the space having the influence radius re are neighboring particles affected by the particle P5. The momentum of the particle P5 is transmitted to the detected nearby particle P8 or the like as a result of the nearby particle influence determination. The same near particle influence determination is performed for the particles P6 other than the particle P5 that is the vicinity particle of the particle P2.
The above-described neighboring particle influence determination is performed for every particle for every minute time. The influence radius “re” is set in advance so that the momentum can be transmitted between the particles and can be stably calculated by the computer main body 1. Here, an example of modeling by the particle method in which each particle P moves in the evaluation space has been described. However, a modeling method capable of creating a discrete expression without using the coordinates of the particle P installed in the evaluation space. Any method can be applied.

The discretization method of the fluid dynamics governing equation (partial differential equation) forms a difference between particles and neighboring particles as proposed by the well-known MPS method, and the following equations (1), (2) A particle interaction model of a gradient operator at a predetermined particle position can be created using the weighting function f and the weighted average shown in FIG. 2, and a spatial differential discrete expression can be formed from the particle interaction model.
When 0 ≦ r <re,
f (r) = re / r−1 (1)
When re ≦ r,
f (r) = 0 (2)
Here, r is the interparticle distance, and re is the search radius.
Also, as proposed by the SPH method, a discrete expression of spatial differentiation may be created by multiplying the kernel function by a particle variable.

After the fluid analysis model 20 is created, a momentum imparting unit 19 that imparts a momentum M to some particles P installed in the simulation space 12 is created in the simulation space 12 (S5), and the particles P in the simulation space 12 are created. A condition for imparting the amount of exercise M is set (S6).
The operator sets and inputs the following conditions for the amount of exercise M to be given.
(1) Part (region) to which momentum M is applied
(2) The amount of momentum M
(3) Direction of momentum M (inflow direction or outflow direction)
(4) Momentum M Giving Time As shown in FIG. 9, in this embodiment, the rear partition wall 18 forming the simulation space 12 is used as the momentum imparting unit 19, and the rear partition wall 18 faces the rear partition wall 18. A predetermined momentum is imparted to a part of the particles P present in the part. This momentum M is given in the direction in which the particles P are pushed toward the front of the vehicle, the so-called inflow direction, until the evaluation end time. Thereby, the process which creates the momentum provision part 19 in the simulation space 12 can be abbreviate | omitted, and a workload can be reduced.

Next, a fluid analysis process is performed by calculation (S7).
In S <b> 7, the coordinates after the momentum are applied to all the particles P existing in the fluid analysis model 20 are calculated. The coordinates of the particle P after the minute time elapses are searched for the nearby particle affected by the momentum M from the predetermined particle P using the neighborhood particle influence determination function, and the velocity after the minute time elapses is calculated from the fluid momentum conservation law. The calculation is performed from the initial coordinates, the minute time, and the speed after the minute time has elapsed.

  As shown in FIG. 8, in S <b> 7, each path L <b> 1 to Ln, K <b> 1 to Km through which the momentum M is transmitted from the particle P <b> 1 to which the momentum M is applied to the neighboring particles is repeatedly searched, and the outside of the evaluation space 11 is The paths L1 to Ln and K1 to Km are calculated up to predetermined particles Pn and Pm that are located at the boundary or do not have neighboring particles. Further, momentum transmission paths L and K in which the respective paths L1 to Ln and K1 to Km are continuously connected from the particle P1 to the predetermined particles Pn and Pm are calculated. In S7, the momentum transmission paths L and K are calculated for all of the partial particles P to which the momentum M is given. As a result, the coordinates and velocity after a lapse of a minute time are calculated for some of the particles P to which the momentum M is applied, and the momentum transmission paths L and K, that is, the paths through which air flows can be detected.

  A flow velocity vector V related to the traveling direction and velocity of each particle P is calculated from the coordinates and velocity of each particle P for each minute time and the momentum transmission paths L and K of each particle P. The flow velocity vector V corresponding to each particle P is assigned to the coordinates of each particle P in the shape model 10, and the direction of these flow velocity vectors V represents the flow direction of each particle P.

In S8, the analysis result obtained by the calculation is displayed on the display device 4.
As shown in FIG. 10, in S8, the flow velocity vector V corresponding to each particle P obtained in S7 is displayed on the shape model 10 in order to display the air flow on the screen. Further, in the display device 4, the flow velocity vector V based on the momentum transmission paths L and K has a red portion where the flow velocity or flow velocity distribution is large, a yellow portion where the flow velocity or flow velocity distribution is intermediate, and a blue portion where the flow velocity or flow velocity distribution is small. Are displayed in different colors. Thereby, a portion where the flow velocity vector V has a large flow velocity or flow velocity distribution, that is, a so-called vehicle member or a portion where gaps 21 and 22 (ventilation portions) are formed between the vehicle members can be displayed in red. A gap between the vehicle members can be visually recognized.

  The display device 4 is formed so as to be able to display the flow rate of air moving along the momentum transmission paths L and K connected to the gaps 21 and 22. Since the number of particles P installed in the simulation space 12 is defined in advance and the coordinates and speed of each particle P are calculated every minute time, the air flow rate that passes through the gap 21 and the gap 22 for each unit time. Can be calculated, and the flow rate of air flowing out for each of the gaps 21 and 22 can be displayed on the screen. (See Figure 11)

The display device 4 is configured to be able to switch the display pattern by an operator's operation.
As shown in FIG. 11, the display device 4 is configured to be able to display the flow velocity or flow velocity distribution of the shape model 10 and the flow velocity vector V by deleting the velocity vector V from the display screen. As shown in FIG. 12, the display device 4 is formed so that the evaluation space 11 can be rotated three-dimensionally on the screen when it is difficult for the operator to visually recognize the positions of the gaps 21 and 22. In addition, the display device 4 can extract and display only the momentum transmission paths L and K corresponding to the air passages connected to the gaps 21 and 22. Thereby, the visual recognition efficiency of the gaps 21 and 22 by the operator can be increased.

After the operator visually recognizes the gaps 21 and 22, the operator determines whether or not the gaps 21 and 22 need to be closed (S9).
If it is not necessary to close the gaps 21 and 22 as a result of the determination in S9, the airtightness evaluation for the evaluation space 11 is terminated. If it is necessary to close the gaps 21 and 22, the process proceeds to S10 and a correction step is performed.

  In S <b> 10, the design change of the CAD data of the front floor where the gap 21 exists, and a new seal member that closes the gap 21 is added. Further, in the case of a complicated shape such as the gap 22 where the ventilation path is continuous across a plurality of vehicle members, the design change of the CAD data of the front pillar where the gap 22 exists, or a new seal member that closes the gap 22 In addition to the addition, a design change can be made in which a node member capable of blocking the air flow is added to a vehicle member other than the front pillar that forms the middle portion of the ventilation path. In S10, after changing the CAD data design of the vehicle member, the process proceeds to S2, and a new shape model 10 after the design change is created and evaluated again.

Next, the operation and effect of the vehicle airtightness evaluation method will be described.
In this vehicle airtightness evaluation method, a large number of particles P that affect each other due to momentum are installed in an evaluation space 11 corresponding to an evaluation space of a shape model 10 in which a fluid analysis model 20 is combined with CAD data of vehicle members. Therefore, the wrapping process and calculation grid creation of the evaluation space 11 can be omitted in the previous stage of the calculation process, and the work load in the airtightness evaluation can be reduced.

  In addition, since a large number of particles P that affect each other due to momentum are installed in the evaluation space 11, at least some of the particles P are not fixed to each other as the nodes of the lattice method are fixed to each other. Momentum transmission paths L and K through which momentum M is transmitted from each to the neighboring particles can be calculated. Moreover, the ventilation portions 21 and 22 of the ventilation path can be displayed based on the momentum transmission paths L and K connected to the outside of the evaluation space 11 among the calculated momentum transmission paths L and K. Therefore, the ventilation part of an unknown ventilation path can be visualized at the design stage, and the gaps 21 and 22 between the vehicle members can be recognized.

Since the display step S8 displays the gas flow rate moving through the ventilation path on the display device 4, the soundproof performance and the seal performance of the vehicle can be evaluated.
Since the display step S8 visualizes the ventilation path and displays it on the display device 4, it is possible to accurately grasp the ventilation path that leads from the gaps 21 and 22 of the evaluation space 11 to the outside.
After the display step S8, since the CAD data of the vehicle member having the gaps 21 and 22 is corrected, the noise and water leakage of the vehicle can be improved at the design stage.

Next, a modification in which the above embodiment is partially changed will be described.
1) In the above-described embodiment, an example in which a shape model of the entire vehicle is created has been described. However, it is sufficient that at least the shape model includes an evaluation space that is an evaluation target space. For example, when the evaluation space is a side door, A side door shape model can be created by combining CAD data of members forming the door with each other.

2] In the above-described embodiment, the example in which the momentum imparting portion is also used as the rear partition wall has been described. However, it is also possible to form the momentum imparting portion separately from the partition wall. In this case, you may set a momentum provision part in the boundary part of simulation space. Moreover, although the example which flows in momentum from the momentum provision part into evaluation space was demonstrated, the same effect can be show | played by flowing out momentum from the evaluation space to momentum provision part.

3] In the above embodiment, an example of the fluid analysis model using the particle method in which each particle can move in the evaluation space has been described. However, if at least the momentum imparted to the particles can be transmitted between the particles, For example, a fluid analysis model using the voxel method can be applied. When the voxel method is used, a fluid analysis model in which an evaluation space is divided by a plurality of voxels (orthogonal lattices) and particles are placed at any one of the divided spaces that are not occupied by members, for example, at the center of gravity of the divided spaces. It may be used.

4) In addition, those skilled in the art can implement the present invention in various forms added with various modifications without departing from the spirit of the present invention, and the present invention includes such modifications. is there.

  The present invention relates to a vehicle airtightness evaluation method capable of displaying a ventilation path on the basis of CAD data of a vehicle member, and creates a fluid analysis model in which a large number of particles that influence each other due to momentum are installed in an evaluation space. By repeatedly searching for a path through which momentum is transmitted from each particle to neighboring particles and calculating the momentum transmission path, it is possible to visualize an unknown ventilation path.

4 Display device 10 Shape model 11 Evaluation space 12 Simulation space 19 Momentum imparting unit 20 Fluid analysis model 21, 22 Gap P, P1-P8 Particles Pn, Pm
M Momentum L, K Momentum transmission pathway

Claims (4)

In the vehicle airtightness evaluation method,
A shape model having an evaluation space, which is a target space for airtightness confirmation, is created by combining CAD data of vehicle members, and a large number of them are included in the evaluation space so as to influence each other by the momentum in the evaluation space of this shape model. A model creation step to create a fluid analysis model with particles of
A momentum giving unit creating step for creating a momentum giving unit capable of giving a momentum to the evaluation space;
A condition setting step for setting a condition for giving the momentum;
By performing fluid analysis on at least some particles to which momentum is imparted from the momentum imparting unit, a path through which momentum is transmitted from the at least some particles to neighboring particles is repeatedly searched to calculate a momentum transmission path. A calculation step;
A display step of displaying a ventilation part of the ventilation path on the display unit based on the momentum transmission path connected to the outside of the evaluation space among the momentum transmission path;
An airtightness evaluation method for a vehicle, comprising:   2. The vehicle airtightness evaluation method according to claim 1, wherein the display step displays a flow rate of the gas moving along the ventilation path on the display unit.   The vehicle airtightness evaluation method according to claim 1, wherein the display step visualizes the ventilation path and displays the ventilation path on the display unit. 4. The vehicle airtightness evaluation method according to claim 1, wherein after the display step, CAD data of a vehicle member including the ventilation portion is corrected. 5.