JP5186856B2 - Tire model creation method and tire simulation method - Google Patents

Description

  The present invention relates to a tire model creation method for creating a tire model used for tire simulation calculation, and a tire simulation method using the creation method.

  Today, in order to analyze tire characteristics, simulation calculation is performed using a tire model, and various simulation calculations have been proposed along with the improvement of computer capability. For example, in order to calculate the cornering characteristics at a predetermined rolling speed, a method for calculating a cornering force has been proposed.

  These simulations are performed by creating a tire model in which the shape of the tire model matches the actual tire shape as much as possible in order to examine the tire characteristics. The reason why the shape of the tire model matches the actual tire shape as much as possible is that the influence of the outer shape of the tire on the tire characteristics is extremely large. If the outer shape of the tire is different, the contact shape and contact pressure distribution of the tire change, and the tire characteristics such as cornering characteristics change.

  On the other hand, in Patent Document 1 below, an outer cross-sectional shape of a tire to be analyzed is measured in advance at room temperature, and a tire basic model is set inside the outer cross-sectional shape based on the outer cross-sectional shape of the tire as a result of the measurement. A method for creating a tire model of a tire to be analyzed is described. Thereby, it is said that a tire model close to a use state can be constructed by analysis using a tire model.

However, in the above-mentioned Patent Document 1, since it is necessary to measure the outer cross-sectional shape of the tire to be analyzed in advance, the actually manufactured tire is set as the analysis target. Therefore, even if the tire model produced by this method can accurately reproduce the outer shape of the actual tire, the relationship with the inner surface shape of the vulcanization mold of the tire used to produce the tire is unknown, It is impossible to predict what tire shape the tire has from this vulcanizing mold and what tire characteristics the produced tire will exhibit. On the other hand, it is also well known to those skilled in the art that the outer shape of a tire produced using a vulcanizing mold does not match the inner shape of the vulcanizing mold used to produce the tire.
For this reason, it is impossible to predict the outer shape of the tire produced from the inner surface shape of the tire vulcanizing mold, and therefore, from the inner surface shape of the tire vulcanizing mold, The tire characteristics of the produced tire cannot be predicted or analyzed.

JP 2006-123644 A

  Therefore, the present invention predicts the tire characteristics of a tire produced by this vulcanizing mold from the inner surface shape of the tire vulcanizing mold when creating a tire model used for tire simulation calculation. It is an object of the present invention to provide a method for creating a possible tire model and to provide a tire simulation method using a tire model created by this method.

The present invention relates to a method of making a tire model to create a tire model used in the simulation calculation of the tire, the step of creating a first tire model with the vulcanizing mold of the inner surface shape of the tire as a predetermined outer shape And applying a thermal expansion coefficient of the tire tread member to at least a portion corresponding to the tire tread member of the first tire model, and for the first tire model to which the thermal expansion coefficient is applied, A step of performing a thermal deformation analysis by applying a predetermined temperature drop, an external shape of the deformed first tire model is set to an external shape , and distortion and stress generated in the deformed first tire model are provided. And a step of creating a second tire model that does not exist as an initial tire model.
In the second tire model, not only the shape of the outer peripheral surface but also the shape of the inner peripheral surface thereof is matched to the shape of the first tire model that has been thermally deformed. When the second tire model is a finite element model, the second tire model is different from the first tire model before being subjected to thermal deformation only in the outer shape, and within the finite element model. The configuration of each element is preferably the same.

At this time, in the step of performing the thermal deformation analysis, an internal pressure filling process is performed in addition to the thermal deformation analysis, and the external shape of the first tire model deformed by these processes is set as the external shape.
It is preferable to create the tire model as an initial tire model .
Moreover , it is preferable that the value of the thermal expansion coefficient set in the first tire model is set so that an absolute value of a product of the value and the temperature decrease is 0.001 to 0.1. .

  Furthermore, the present invention provides a tire simulation method, wherein a tire simulation is performed using the initial tire model created by the tire model creation method.

  In the present invention, after the thermal deformation analysis is performed by giving a predetermined temperature change, giving a thermal expansion coefficient to at least a portion corresponding to the tire tread member of the first tire model having the predetermined outer shape created. As a result, a second tire model having the outer shape of the deformed first tire model as an outer shape is created as an initial tire model. For this reason, the outer shape of the tire produced by this vulcanizing mold from the inner surface shape of the vulcanizing mold of the tire by setting the predetermined outer shape to the inner surface shape of the vulcanizing mold of the tire, for example. Can be predicted, and tire characteristics can be predicted and analyzed.

  Hereinafter, a tire model creation method and a tire simulation method according to the present invention will be described in detail based on embodiments shown in the accompanying drawings.

  An outline of the simulation apparatus 10 shown in FIG. 1 is as follows. First, a first tire model having an inner shape of a tire vulcanization mold as an outer shape is created, and at least a portion of the created first tire model corresponding to the tire tread member is made of a tire tread member material. A coefficient of thermal expansion is given as a physical property value. Next, thermal deformation analysis is performed on the first tire model to which the thermal expansion coefficient is given by applying a predetermined temperature change, for example, a temperature change from the vulcanization temperature to about room temperature. A second tire model having the outer shape of the first tire model deformed by the thermal deformation analysis as an outer shape is created as an initial tire model, and the created initial tire model is used for simulation calculation and a simulation result is output. .

The simulation apparatus 10 is configured by a computer including a CPU 12, a memory 14, and an input / output unit 16. An input operation system 26 such as a mouse and a keyboard, a display 28 and a printer 30 are connected to the computer via an input / output unit 16.
By reading the program stored in the memory 14 and executing the program, the program module groups of the condition creation module 18, the thermal deformation analysis module 20, the tire model creation module 22, and the simulation calculation module 24 are formed.
The CPU 12 controls and manages the operation of each program module, and is also a part that substantially calculates the processing contents of each program module.

The condition creating module 18 sets model conditions for creating a tire model using a finite element method, and further sets simulation conditions for reproducing the ground contact state or rolling state of the tire by simulation. is there. For example, information for determining the configuration of the model such as the number of elements and the number of nodes of the tire model, and the value of the material parameter of the tire member are set. In addition, simulation conditions such as internal pressure applied to the tire model, contact load, and traveling speed are set.
These setting contents are created in accordance with an operator instruction from the input operation system 26 and are stored and held in the memory 14. The operator's instruction is given while looking at the input setting screen displayed on the display 28 by the operator. When a simulation is performed, the stored contents are called by the condition creation module 18 to set model creation conditions and simulation conditions.

The thermal deformation analysis module 20 is a part that performs thermal deformation analysis on the first tire model created by the tire model creation module 22 described later. Specifically, the first tire model is a finite element model having an inner shape of a tire vulcanization mold as an outer shape, and the material property value represents a mechanical characteristic such as Young's modulus and shear rigidity. In addition to the material property values, at least a thermal expansion coefficient is included. In the present invention, these values are called material parameters. Therefore, for the first tire model, the temperature change is set to −150 ° C. so as to reproduce the decrease in the atmospheric temperature from the vulcanization temperature 170 ° C. to 20 ° C., based on the temperature change. Thus, the strain distribution, stress distribution and thermal deformation appearing in the tire model can be calculated. The coefficient of thermal expansion refers to the rate of change in length or volume when the temperature rises by 1 ° C. Here, it is preferable to give a thermal expansion coefficient to at least a portion corresponding to the tread rubber member in the first tire model. The tread rubber member has a larger volume ratio than other constituent members of the tire, such as side rubber members, bead filler rubber members, rim cushion rubber members, inner liner rubber members, cord rubber members used for belt members, etc. The heat shrinkage is larger than that of the constituent members. For this reason, it is preferable to give a thermal expansion coefficient at least to a portion corresponding to the tread rubber member.
The data of the first tire model after the thermal deformation analysis calculated by the thermal deformation analysis module 20 is stored in the memory 14.

The tire model creation module 22 calls and sets the model conditions for creating the tire model created by the condition creation module 18 and stored in the memory 14, or the tire model creation module 22 stores the first tire model stored in the memory 14. This is the part that calls up the data after thermal deformation analysis and creates a tire model based on the called conditions and data. The tire model includes a first tire model and a second tire model. The first tire model is a model composed of a finite element model for performing thermal deformation analysis, and includes an inner surface shape of a tire vulcanization mold as an outer shape. The first tire model is provided with material property values indicating mechanical properties such as Young's modulus, shear rigidity, Poisson's ratio, etc. In addition, as described above, at least the portion corresponding to the tread member is subjected to thermal deformation. A thermal expansion coefficient is given so that the deformation | transformation by analysis arises. The second tire model is a model composed of a finite element model in which the outer shape of the first tire model after thermal deformation is the outer shape using the data of the first tire model after thermal deformation analysis.
A material property value necessary for performing a simulation calculation described later is given to the second tire model. The data of the created second tire model is stored in the memory 14.

In the simulation calculation module 24, the internal pressure filling process and the ground contact process are performed on the second tire model in accordance with the set simulation conditions, and the rolling process is performed as necessary to reproduce the rolling of the tire. Perform a simulation. For example, a rolling process is performed at a rolling speed of 50 (km / hour), and then a simulation is performed in which cornering traveling is reproduced by giving a slip angle of 1 degree.
The simulation result data is stored in the memory 14 and the simulation result is displayed on the display 28 or output to the printer 30 via the input / output unit 16.
The tire simulation method executed by the simulation apparatus 10 having the above configuration will be described in more detail.

FIG. 2 is a flowchart showing a processing flow of an embodiment of the tire simulation method of the present invention.
First, a model condition for creating a tire model and a simulation condition for performing a simulation calculation are created (step S10). The model condition and the simulation condition are created when the operator inputs through the input operation system 26 while looking at the screen. The created model conditions and simulation conditions are stored in the memory 14.
The model conditions include information on the arrangement of each element of the finite element model, the number of elements and the number of nodes, and the value of a material parameter to be given to each element. Simulation conditions include running conditions such as internal pressure, contact load, rolling speed, road surface unevenness, slip angle, camber angle, toe angle, slip ratio, coefficient of friction with the road surface, etc. applied to the tire model. .

Next, the tire model creation module 22 creates a first tire model according to the model conditions of the tire model that are called from the memory 14 and set (step S20). Further, when it is set to perform a simulation for grounding on the road surface under the simulation conditions, a road surface model is created according to the simulation conditions.
Next, the tire model creation module 22 assigns a thermal expansion coefficient to the first tire model in accordance with the model conditions set for the created first tire model (step S30). Of course, the material physical property value which shows a mechanical characteristic is also provided.
FIG. 3 shows a cross-sectional shape of the created first tire model T. The external shape of the tire model T is a shape that matches the internal shape of the tire vulcanization mold. Specifically, the creation of the tire model T includes the coordinate position data of the numbered nodes in each element of the tire model T, the number data of the nodes constituting each element, and the simulation condition data. It means to be compiled as a tire model file. Furthermore, in addition to the material property values of Young's modulus, shear rigidity, and Poisson's ratio, the value of the thermal expansion coefficient is given to the data of the first tire model. The thermal strain due to temperature change is determined by the product of the thermal expansion coefficient and the temperature change, and the same thermal strain occurs if the product value is the same. The thermal expansion coefficient of the rubber member is 10 ^{−5 to} 5 × 10 ⁻⁴ , and the temperature change from the vulcanization temperature to room temperature is approximately 150 ° C. In the present embodiment, the absolute value of the product of the thermal expansion coefficient and the temperature change may be in the range of 0.001 to 0.1. Furthermore, if the product of the thermal expansion coefficient and the temperature change is the same value and the absolute value of the product is in the range of 0.001 to 0.1, how can the value of the thermal expansion coefficient and the temperature change be set? It may be given. For example, if the temperature change is 10 times, even if the thermal expansion coefficient is set to 1/10, the result of the thermal deformation analysis does not change.

  Next, the thermal deformation analysis module 20 performs the thermal deformation analysis by giving the above-described temperature change to the created first tire model (step S40). In the thermal deformation analysis, a coefficient of thermal expansion is given to at least the element corresponding to the tread member, and the temperature decreases by 150 ° C., so the element is thermally contracted by this coefficient of thermal expansion. And the position of each node of the element is displaced, and the first tire model is deformed. In the thermal deformation analysis, for example, the displacement is fixed at the node position of the first tire model corresponding to the portion where the tire contacts the rim.

Next, the tire model creation module 22 creates a second tire model in which the outer shape of the first tire model that has undergone thermal deformation is the outer shape (step S50). The first tire model that has undergone thermal deformation is distorted or stressed, but the second tire model that is created does not have this distortion or stress and is the first tire model that has undergone thermal deformation. It has the same outer shape as the outer shape. Here, in the second tire model, not only the shape of the toroidal outer peripheral surface of the tire model but also the shape of the inner peripheral surface matches the shape of the thermally deformed first tire model.
Therefore, the second tire model is different from the first tire model before undergoing thermal deformation only in the outer shape, and the configuration of each element in the model is the same. On the other hand, the position coordinates of the nodes of each element change as the outer shape changes. The data of the created second tire model is stored in the memory 14 as an initial tire model.

  The simulation calculation module 24 calls the data of the initial tire model created in this way, and performs an internal pressure filling process, a ground contact process, and a rolling process on the initial tire model in accordance with the simulation conditions created in step S10. The simulation calculation is performed (step S60).

  The internal pressure filling process is a process that reproduces the process of filling the tire with the rim and filling the internal pressure. The internal pressure filling process refers to a process of applying a pressure corresponding to the tire internal pressure to the inner peripheral surface of the tire model. Specifically, an equation using a matrix expressed for the internal pressure filling process is created from the data of the second tire model, and the above-mentioned predetermined pressure is applied as an external force to this equation to displace the node. The tire model data after the internal pressure filling process is calculated by calculating the strain and the like. The calculated tire model data is stored in the memory 14.

  The grounding process is a process of grounding the tire model that has been subjected to the internal pressure filling process on the generated road surface model. Specifically, gradually reduce the distance between the tire initial model and the road surface model, calculate the state where the initial tire model touches the road surface model, and calculate the reaction force that acts on the initial tire model. To do. The distance between the initial tire model and the road surface model is decreased until the reaction force reaches a target value (contact load), and the process is repeated until the reaction force reaches a target value. In such a grounding process, data of the initial tire model subjected to the internal pressure filling process is called from the memory 14, and the grounding process is calculated from the data using a matrix expressed for the grounding process. Data of the initial tire model after the contact processing obtained by the calculation is stored in the memory 14.

  The rolling process is a process for causing the initial tire model to travel at a set traveling speed with respect to the road surface model. This process is performed by sequentially calculating the analysis time at predetermined time steps. In the rolling process, specifically, translational motion and rotational motion around the tire rotation axis are separately given to the initial tire model. For translational motion, a translation displacement corresponding to the time step size of the time step is applied to each node of the initial tire model so that the initial tire model translates at the set traveling speed. On the other hand, for the rotational motion, a displacement corresponding to a predetermined angular velocity is applied so as to rotate around the tire rotation axis. The free rolling process reproduces the state where the rotational torque around the tire rotation axis is substantially zero, but the initial tire model is deformed by the ground load, so the value obtained by dividing the running speed by the radius of the initial tire model. Even if the angular velocity is used, the rotational torque does not become substantially zero, and the initial tire model is not in a free rolling state. For this reason, in order to search for a free rolling state (a state in which the rotational torque is substantially 0), in this embodiment, the free rolling state is set while sequentially changing the angular velocity applied to the initial tire model. Alternatively, the rotation of the initial tire model can be freely rolled by setting the rotation axis of the initial tire model to a rotation-free state in which the degree of freedom of rotation is not constrained and by giving displacement so that the initial tire model moves at a predetermined traveling speed. Processing may be performed.

In this way, according to the simulation conditions for the initial tire model in the free-rolling state, if necessary, the slip angle, camber angle, road surface unevenness conditions, etc. are changed to affect the physical quantity acting on the initial tire model, for example, the rotating shaft. Calculate lateral force, longitudinal force, etc.
The calculated physical quantity is stored in the memory 14 together with the rolling initial tire model data as a simulation result, and is output to the display 28 and the printer 30 via the input / output unit 16 (step S70).

In the above embodiment, the second tire model having the outer shape of the first tire model subjected to the thermal deformation analysis by giving a temperature change of 150 ° C. from the vulcanization temperature of 170 ° C. to the room temperature of 20 ° C. An initial tire model was used. In the present invention, as another embodiment, the external shape of the first tire model deformed by applying a predetermined internal pressure filling process to the created first tire model in addition to thermal deformation analysis is described. The tire model may be an initial tire model. In the actual tire manufacturing process, a predetermined internal pressure filling process is performed on the first tire model. In the actual tire manufacturing process, the tire taken out from the vulcanization mold is subjected to an internal pressure applying process called a PCI (Post Curing Inflation) process. This is done to stabilize the tire shape and to reproduce this process. The outer shape of the tire after the PCI process is larger than the outer shape of the tire taken out from the vulcanization mold.
The internal pressure filling process that reproduces the PCI process may be performed as a pre-process of the thermal deformation analysis, or may be performed simultaneously with the thermal deformation analysis, as a post-process of the thermal deformation analysis.

FIG. 4 (a) shows an outer shape of a tire model when an inner shape of the tire vulcanization mold is used as an outer shape and a tire is produced using the vulcanization mold. By overwriting the measured outer shape of the tire, the difference in the outer shape is shown. The actually measured outer shape is indicated by a thick line A.
On the other hand, FIG. 4 (b) superimposes the outer shape of the initial tire model created by the processing flow shown in FIG. 2 and the measured outer shape of the tire when the tire is produced using the vulcanization mold. By writing, the difference in outer shape is shown. The actually measured outer shape is indicated by a thick line A. Each element corresponding to the tread member was given a thermal expansion coefficient of 1.4 × 10 ⁻⁴ . The tire model shown in FIGS. 4A and 4B is a three-dimensional model having about 59000 nodes and about 54000 elements.
4 (a) and 4 (b), the difference between the outer shape of the tire model shown in FIG. 4 (a) and the actually measured outer shape of the thick line A is larger in the shoulder region S. FIG. On the other hand, the difference between the outer shape of the initial tire model shown in FIG. 4B and the actually measured outer shape of the thick line A is generally smaller than the difference shown in FIG. The difference from A is small. From this, it can be seen that the initial tire model created by the processing flow shown in FIG. 2 has a shape close to the outer shape of the actually measured tire.

In FIG. 5A, the initial tire model created by the processing flow shown in FIG. 2 was subjected to the internal pressure filling process and the grounding process under the simulation conditions of the internal pressure 230 (kPa) and the grounding load 4.5 (kN). It is a figure which shows the grounding shape at the time. FIG. 5B is a diagram showing a contact shape when the tire model shown in FIG. 4A is subjected to the internal pressure filling process and the ground contact process under the internal pressure and ground load conditions similar to the simulation conditions described above. It is.
The thick line B shows the contour of the measured contact shape under the conditions of an internal pressure of 230 (kPa) and a contact load of 4.5 (kN) when an actual tire is manufactured using the vulcanization mold. Show.
It can be seen that the ground contact shape of the initial tire model shown in FIG. 4A is closer to the actually measured contact shape than the contact shape of the tire model shown in FIG. From this, it can be seen that the contact shape of the initial tire model created in the processing flow shown in FIG. 2 is close to the actual contact shape of the tire. Actually, since the tire characteristics are determined by being greatly influenced by the contact shape and contact pressure distribution formed in contact with the road surface, the tire model creation method of the present invention that can bring the contact shape closer to the actually measured tire. By using it, it becomes possible to predict tire characteristics with high accuracy.

  The tire model creation method and tire simulation method of the present invention have been described above in detail. However, the present invention is not limited to the above embodiment, and various improvements and modifications can be made without departing from the gist of the present invention. Of course.

It is a schematic block diagram of the simulation apparatus which implements the preparation method and simulation method of the tire model of this invention. It is a flowchart which shows the flow of a process of one Embodiment of the simulation method of the tire of this invention. It is sectional drawing which shows an example of the 1st tire model used with the preparation method of the tire model of this invention. (A) And (b) is a figure which shows the difference of the external shape of the produced tire model, and the external shape of an actual tire. (A) And (b) is a figure which shows the difference between the contact shape of the created tire model, and the actual contact shape of a tire.

Explanation of symbols

10 Simulation device 12 CPU
DESCRIPTION OF SYMBOLS 14 Memory 16 Input / output unit 18 Condition creation module 20 Thermal deformation analysis module 22 Tire model creation module 24 Simulation calculation module 26 Input operation system 28 Display 30 Display

Claims (5)

A tire model creation method for creating a tire model used for tire simulation calculation,
And creating a first tire model with the vulcanizing mold of the inner surface shape of the tire as a predetermined outer shape,
Providing a coefficient of thermal expansion of the tire tread member to at least a portion of the first tire model corresponding to the tire tread member;
Performing a thermal deformation analysis by giving a predetermined temperature drop to the first tire model to which the thermal expansion coefficient is given;
Creating an outer shape of the deformed first tire model as an outer shape , and creating a second tire model having no distortion or stress generated in the deformed first tire model as an initial tire model; A method for creating a tire model, comprising:   In the second tire model, not only the shape of the outer peripheral surface but also the shape of the inner peripheral surface thereof are matched to the shape of the first tire model that has been thermally deformed. When the tire model of No. 2 is a finite element model, the second tire model is different from the first tire model before being subjected to thermal deformation only in the outer shape, and each element in the finite element model The tire model creation method according to claim 1, wherein the configurations of the tire models are the same. In the step of performing the thermal deformation analysis, in addition to the thermal deformation analysis, an internal pressure filling process is performed, and a second tire model whose external shape is the external shape of the first tire model deformed by these processes is defined as an initial tire model. The method for creating a tire model according to claim 1 or 2 , wherein the tire model is created as follows. The value of the thermal expansion coefficient set for the first tire model is set so that the absolute value of the product of the value and the temperature drop is 0.001 to 0.1. The method for creating a tire model according to any one of the above.   A tire simulation method, wherein a tire simulation is performed using the initial tire model created by the tire model creation method according to any one of claims 1 to 4.

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