JP2009227041A - Method of setting alarming threshold value in detection method for tire air pressure drop detecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of setting an alarming threshold value for detecting the drop of tire air pressure while avoiding or reducing test using an actual vehicle. <P>SOLUTION: The method of setting the alarming threshold value is provided for detecting the drop of tire air pressure in accordance with the wheel rotating speeds of tires mounted on a four-wheel vehicle. The method includes: a step of creating a vehicle model including a suspension member; a step of creating tire models representing the property of longitudinal force of the tires during regular inner pressure and reduced pressure; a step of inputting a friction coefficient between the tire and a road surface; a step of inputting data including the front face projection area of the vehicle, a position where aerodynamic reaction operates, an air drag coefficient and an air lift coefficient, representing air resistance generated on the vehicle during travel; and a step of performing travel simulation of the vehicle model. In accordance with the wheel rotating speed of the tires of the four wheels obtained in the simulation step, the alarming threshold value is set for determining whether air pressure in each driving wheel tire drops or not. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for setting an alarm threshold in a method for detecting a decrease in tire air pressure. More specifically, the present invention relates to a method for setting an alarm threshold in a method for detecting a decrease in tire air pressure, in which an alarm threshold is set as a reference value when determining decompression of a tire by motion analysis simulation of a traveling vehicle.

  There is a method of indirectly detecting whether or not the tire air pressure has decreased using the rotational speed of the wheel mounted on the vehicle (see, for example, Patent Documents 1 and 2). Conventionally, when such a detection method is put into practical use, an actual vehicle test is performed to perform a work called a calibration operation including verification of logic and optimization of variables (parameters) used in the detection method. It was. In other words, by obtaining a development vehicle that will be equipped with an air pressure drop detection device and conducting an actual vehicle test that runs on a test course etc., the wheel rotation speed, lateral G, yaw rate, steering angle, wheel torque of each of the four wheels Information such as various sensor information (information necessary for air pressure drop detection) was obtained. And the adaptation work for every vehicle was performed by analyzing the obtained test data. In particular, the setting of an alarm threshold value for determining whether or not to issue a decompression alarm to the driver is obtained from test data obtained by performing linear travel at a constant speed at a plurality of speed levels.

Japanese Patent Laid-Open No. 2005-1419 JP 2006-1298 A

  However, since the actual vehicle test requires the development vehicle itself, it is necessary to wait for the development vehicle to be completed, and there are restrictions such as the number of test vehicles and the duration of the test being limited. In addition, since testing is actually performed by a test driver, labor costs, vehicle management costs, fuel costs, and other costs are incurred, as well as a vast amount of man-hours and long development periods such as measurement preparation and data analysis. There is also a problem that it takes. In addition, if a development vehicle that has already undergone the adaptation work has undergone a minor change, it is necessary to carry out a new actual vehicle test with the development vehicle that has undergone this minor change, and until the adaptation work for one type of development vehicle is completed, It took a lot of cost and time.

  The present invention has been made in view of such circumstances, and in setting the alarm threshold used in the air pressure decrease detection method, the alarm threshold in the tire air pressure decrease detection method capable of eliminating or reducing the test by the actual vehicle. It aims to provide a setting method.

In the tire pressure drop detection method of the present invention, the alarm threshold setting method (hereinafter also simply referred to as “setting method”) is a tire that detects a drop in tire air pressure based on the wheel rotation speed obtained from a tire mounted on a wheeled vehicle. A method for setting an alarm threshold in a method for detecting a decrease in air pressure,
A vehicle model creation step for creating a vehicle model including a suspension member;
Creating a tire model that can represent the characteristics of the longitudinal force of the tire at least at the time of normal internal pressure and reduced pressure;
Inputting a coefficient of friction between the tire and the road surface;
A step of inputting data including a front projected area of the vehicle, a position where an aerodynamic reaction force acts, an air drag coefficient and an air lift coefficient expressing air resistance generated in the vehicle during traveling;
A simulation step of performing a running simulation of the vehicle model on which the created tire model is mounted, and the air pressure of the drive wheel tire is determined based on the wheel rotational speed of the tire of each of the four wheels obtained in the simulation step. It is characterized by setting an alarm threshold value for determining whether or not it is lowered.

  In the setting method of the present invention, the wheel rotation speed of the tire of each of the four wheels is obtained by performing a running simulation of the vehicle model equipped with the tire. Then, based on this wheel rotation speed, an alarm threshold for determining whether or not the tire air pressure has decreased is set, so that a value necessary for tire decompression determination can be obtained without performing an actual vehicle test. Can do. Therefore, the cost and time required for the actual vehicle test can be greatly reduced.

  The vehicle model includes vehicle center position, vehicle moment of inertia, wheel base length, vehicle front and rear wheel widths, vehicle weight, suspension spring spring characteristics, damper damping characteristics, and roll center height. Can be created.

  According to the setting method of the present invention, it is possible to eliminate or reduce the test using an actual vehicle when setting the alarm threshold value used in the tire pressure drop detection method.

Hereinafter, embodiments of a setting method of the present invention will be described in detail with reference to the accompanying drawings.
A tire pressure drop detection device (DWS) that indirectly detects tire pressure reduction from the rotational angular velocity of a wheel executes a program stored in advance in a storage unit included in a control unit such as a control unit mounted on the vehicle. Thus, it is determined whether or not the tire is depressurized. However, an operation (adaptation operation) for determining various parameters used in the program is required depending on the type of the vehicle and the tire size. In the past, parameters to be determined in such conforming work were obtained by analyzing data obtained by actual vehicle tests. However, in the present invention, data is obtained by simulation, and the parameters are obtained by analyzing this data. Yes.

  For example, a method for setting an alarm threshold value for generating an alarm when pressure reduction occurs in one of the driving wheels of a two-wheel drive vehicle, or when pressure reduction occurs in one wheel of a four-wheel drive vehicle has hitherto been Although several proposals have been made, all of them have acquired data by repeating actual vehicle tests at a plurality of speed levels, and the alarm threshold value has been calculated from this data.

  In the present invention, it is possible to consider the influence of the air resistance on the traveling vehicle by using the specifications capable of calculating the air resistance generated when the vehicle travels, and this is generated depending on the speed. It becomes possible to calculate the slip amount of the drive wheel with high accuracy. Then, by considering the coefficient of friction with the road surface and the slip amount that depends on the longitudinal force of the tire, a warning threshold value for determining that the driving wheel tire has been depressurized can be obtained from the simulation.

There are two major performances required for DWS. One is the alarm performance that reliably alerts the decrease in air pressure that should be alarmed, and the other is when there is no decrease in air pressure that should be alarmed, that is, as described below, such as unbalanced load on the vehicle and sudden turn of the vehicle. This is a false alarm performance that does not give false alarms when the rotational speed of a wheel becomes faster than normal internal pressure for a reason.
In the present invention, by executing a virtual actual vehicle test by simulation, an alarm threshold value for determining that the driving wheel tire is decompressed among the parameters can be obtained in a short period of time and with a short man-hour.

FIG. 1 is a flowchart showing a setting method according to an embodiment of the present invention. First, in step S1, a program for an air pressure drop detection device for a developed vehicle is designed. The tire pressure drop detection (warning) device is based on the principle that when the tire is depressurized, the outer diameter (dynamic load radius of the tire) is smaller than the tire with normal internal pressure, so the rotational angular velocity increases compared to other normal tires. Used. Various judgment values or judgment formulas used to judge whether or not a tire is depressurized have been proposed. For example, DEL = {(F1 + F4) / 2− (F2 + F3) / 2} / {(F1 + F2 + F3 + F4) / 4} × 100 as a determination value (DEL) when detecting a reduced pressure from a relative difference in tire rotational angular velocity. %) ... (1)
Can be used. Here, F1 to F4 are rotational angular velocities of the front left tire, the front right tire, the rear left tire, and the rear right tire, respectively. In the air pressure decrease detection device, the obtained judgment value is compared with a predetermined alarm threshold value (for example, DEL when a certain tire is depressurized by 30%), and when the judgment value exceeds this threshold value, the tire Estimate that is depressurized and issue an alarm.

  In the present invention, it is detected whether one wheel of a two-wheel drive vehicle or one wheel of a four-wheel drive vehicle is depressurized, and the determination value (DEL) is, for example, the equation (1) ) Can be used.

  In the present invention, as described above, by considering the air resistance, the slip amount of the drive wheel generated depending on the speed is calculated, and this depends on the coefficient of friction with the road surface and the longitudinal force of the tire. By taking into account the amount of slip that occurs, the change in the rotational speed of the tire due to the reduced pressure can be calculated with high accuracy.

  In the present invention, the determination value, the program for obtaining the determination value, and the threshold value for pressure reduction determination are not particularly limited, and the pressure reduction of the tire is determined using the rotational angular velocity of the tire of each of the four wheels. As long as conventional logic or programs can be used as long as possible.

  Next, in step S2, a development vehicle model and a tire model for simulation are created. When executing a running simulation to be described later, it is necessary to create a vehicle model of the developed vehicle, but with the indirect tire pressure drop detection device that determines the decompression of the tire based on the rotation speed of the tire mounted on the four-wheel vehicle, Usually, the position of the center of gravity of the vehicle, the moment of inertia of the vehicle, the length of the wheel base, the width of each track of the front and rear wheels of the vehicle, the vehicle weight (the weight on the vehicle spring, the weight under the vehicle spring), the spring spring characteristics of the suspension, the damper damping characteristics, and the roll center A vehicle model can be created by inputting vehicle characteristic values including height. However, depending on the software used, it is possible to model the vehicle body shape and material properties and input these to perform a simulation. For example, in the case of a suspension, the shape of the suspension can be subdivided directly as a model by the finite element method, or a mechanism model that is exactly the same as the actual product can be expressed. That is, a model is created based on the shape information. Further, as a component material value used together with shape information, when a metal material is targeted using a finite element method, an elastic modulus, a Poisson's ratio, a density, and the like can be given.

  In addition to the suspension spring spring characteristics, damper damping characteristics, and roll center height, values for expressing the suspension dynamic characteristics in the vehicle motion analysis simulation include, for example, vehicle unsprung weight, tires and wheels. Axle moment of inertia, various changes related to the elastic properties of the bushing (changes in the longitudinal direction when the axle is moved in the vertical direction [mm / mm], up and down applied to the tire when the brake is applied) Direction force [N / N], toe angle variation [Deg / N] when lateral force is applied to the tire, steering angle variation [Deg / N] when lateral force is applied to the tire, tire Steering angle variation [Deg / N · m] when aligning torque is applied to the wheel, longitudinal variation at the wheel center when the longitudinal force is applied to the tire [mm N], camber angle change amount [Deg / N] when a longitudinal force is applied to the tire, inclination angle change amount [Deg / N · m] when the aligning torque is applied to the tire, and lateral force applied to the tire Wheel center lateral change amount [mm / N], toe angle and vertical displacement relationship [Deg / mm], camber angle and vertical displacement relationship [Deg / mm]). These values can be used as appropriate according to the software to be used.

  Then create a tire model. This tire model has a longitudinal force (front / rear force [N] with respect to front / rear slip [%]), lateral force (cornering force, lateral force [N] against slip angle [Deg]), A tire characteristic value consisting of a lining moment (SAT, moment with respect to a slip angle) and a camber thrust can be entered by inputting numerical values. As these characteristic values, for example, indoor test result data can be used. Also, as in the case of the vehicle model, the tire itself can be modeled in the shape with the internal structure (for example, modeling by the finite element method or modeling of the spring and mass) depending on the software used. Is possible.

  In step S2, the coefficient of friction between the tire and the road surface is input. In addition, the front projected area of the vehicle that expresses the air resistance generated in the vehicle during traveling, the reference point on which the aerodynamic force acts (in the spring mass point system model, the aerodynamic force is originally acting on the entire body body, Data that includes an aerodynamic drag coefficient and an air lift coefficient is input when the aerodynamic force acts on one representative point. From these data or specifications, the air resistance generated in the vehicle during traveling can be calculated. By taking this air resistance into consideration, the slip amount of the drive wheel generated depending on the speed can be accurately calculated.

  Next, in step S3, a simulation of running the vehicle model equipped with the tire model created in step S2 is executed. By this running simulation, it is possible to obtain the wheel rotation speed of each of the four wheels in consideration of tire slip. Based on the wheel rotation speed, a parameter (determination value) for determining whether or not the tire is depressurized can be calculated using, for example, the above-described equation (1). If there are characteristics that can be input with a simulation tool, such as engine torque characteristics or torque converter characteristics, it is preferable to input such characteristics in order to improve the accuracy of the simulation.

  Examples of simulation software that can perform vehicle motion analysis include “Adams” (product name), “veDYNA” (product name), “CarSim” (product name), “LS-DYNA” (product name), and the like. The present invention is not particularly limited as long as simulation software frequently used in the automobile industry can be used as appropriate and vehicle motion analysis is possible.

  Next, in step S4, a simulation is executed using another tire model to be mounted. Normally, there are multiple types of tires that are planned to be installed on one type of vehicle (developed vehicle). Even if an analysis is performed on one type of tire and parameters that match that type are set, But it is unclear whether it is a suitable parameter. For this reason, it is preferable to execute a simulation with other types of tires (other mounted tires) to determine whether the parameters already obtained are appropriate and whether the parameters need to be changed. The criterion is that when the tire is actually depressurized, it is possible to reliably warn this and prevent false alarms. With regard to FIG. 8 or Table 8 to be described later, the fixed volume state (maximum loading state) ), It is possible to alarm 25% decompression of the driving wheel in the speed range of 30 to 140 kph, and low decompression amount that does not need to be alarmed, such as 10% decompression in the light load state (equivalent to two-seater) You can ask whether or not to alarm.

  In step S5, it is determined whether or not a satisfactory result regarding the alarm performance is obtained. If a satisfactory result is obtained (Yes), the process proceeds to step S6, and the air pressure drop detecting device for the developed vehicle is detected. If the program and various parameters are determined and no satisfactory result is obtained (No), the decompression determination logic and / or parameters are changed in step S7, and the process returns to step S3.

Examples of the present invention will be described below, but the present invention is not limited to such examples.
[Example]
As vehicle motion analysis simulation software, CarSim (registered trademark, vehicle motion simulation software of Virtual Mechanics Co., Ltd.) was used. Vehicle data shown in Tables 1 to 3 was input as necessary vehicle data regarding the implementation vehicle A (front wheel drive or rear wheel drive or four wheel drive?) (Refer to FIGS. 5 to 7 for data items). Moreover, 225 / 50R17 (made by Dunlop) was used as the tire B, and tire data shown in Tables 4 to 7 was input as tire data. In addition, the following data was entered as specifications regarding air resistance.

Data for calculating air resistance Front projected area: 1.8 m ²
Aerodynamic drag coefficient: 0.34
Aerodynamic lift coefficient: 0.16
Reference point where aerodynamics acts: 1.44m behind the front wheel axle center, center of vehicle width and ground
Then, a running simulation was performed, and a simulation for calculating an alarm threshold, which is a parameter related to alarm performance, was performed. The simulation results are shown in Table 8 and FIG.

[Comparative example]
An actual vehicle test was performed using the implementation vehicle A, and a depressurization judgment value (DEL) at the time of depressurization of one drive wheel was obtained. The result of the actual vehicle test is shown in FIG.
The decompression judgment value obtained by the simulation is calculated with an accuracy within 10% of the decompression judgment value obtained in the actual vehicle test, and the alarm threshold, which is one of the parameters in the air pressure drop detection method, is accurate. It turns out that it can be set well. By performing a vehicle motion analysis simulation, the alarm threshold value can be calculated without carrying out an actual vehicle test, and the man-hours and costs associated therewith can be reduced.

  In addition, as described above, the parameters necessary for the air pressure drop detection device have been acquired by carrying out an actual vehicle test in the present situation, but the OE (Origin Equipment) tire that is installed when the vehicle is purchased is There are often multiple. The parameters required for the air pressure drop detection device may vary depending on the tire to be mounted. For example, an alarm threshold value, a turn correction coefficient for correcting a pressure reduction determination value when the vehicle is turning, and the like. Therefore, at present, a value that can satisfy the performance approved by the automobile manufacturer is determined as the parameter value in all of the plurality of OE tires.

For this reason, when there are a plurality of OE tires, an optimal parameter value for a tire that is actually mounted may not be selected. Furthermore, the alarm performance and the like when the replacement tire is mounted are unknown.
On the other hand, as a method of using an optimum parameter value for each of a plurality of OE tires, since the number of the OE tires is limited, an optimum value for each OE tire is obtained in advance by an actual vehicle test, It is conceivable to input the optimum value obtained in this way into a pneumatic pressure drop detection device system (DWS system) mounted on the vehicle. However, since there are an infinite number of replacement tires, it is impractical to perform an actual vehicle test in advance in order to obtain an optimum value thereof.

  Therefore, it is conceivable to perform the calibration work including the alarm threshold setting described above not at the development stage but at the time of tire mounting after vehicle sales. In other words, in the setting method described above, a simulation is performed using a computer (computer) at the development site, and the optimum value that can be accessed by an on-board computer; It is performed in a personal computer or personal computer owned by a trader or individual, and the optimum value of each tire obtained as an output is input as a parameter value to the DWS system installed in the vehicle. Even with a replacement tire, it is possible to accurately detect a decrease in tire air pressure.

The following three modes are conceivable as modes for realizing the fitting work by such simulation.
[Aspect A]
In this aspect, the simulation is executed by a computer mounted on the vehicle.
First, vehicle information such as the position of the center of gravity of the vehicle and the moment of inertia of the vehicle is input to a computer mounted on the vehicle. As shown in FIG. 2, tire characteristic data (tire longitudinal force, aligning moment, etc.) is acquired from the outside of the vehicle through information communication means such as the Internet or as information built in the IC tag ( Step S10).

In step S11, the acquired tire characteristic data is input to the in-vehicle computer. Next, in Step S12, a simulation is performed by an in-vehicle computer in which vehicle information unique to the vehicle is pre-installed, and parameters necessary for the DWS system (for example, an alarm threshold value and a turning correction for correcting an alarm judgment value at the time of turning) Coefficient, a parameter for determining an unbalanced load state, a threshold value for setting a data rejection condition, etc.).
Next, in step S13, when the optimum parameter value obtained in step S12 is input to the in-vehicle DWS system, the DWS system can be operated with the optimum parameter value for the mounted tire (step S14).

[Aspect B]
In this aspect, the simulation is executed at a site or server outside the vehicle. Parameters necessary for the DWS system are analyzed and calculated by means such as ASP (Application Service Provider) on the Internet, and a site or server that can output the result is accessed (step S20). Next, information (vehicle name, installed tire brand, tire size) necessary for the simulation is input from the input means equipped on the in-vehicle computer (step S21).

In the site or server, vehicle data and tire characteristic data are managed, and analysis calculation of optimum parameter values is performed using these data, and the obtained parameter values are transmitted via information communication means such as the Internet. To the input person (step S22).
When the input person inputs the transmitted optimal parameter value to the DWS system mounted on the vehicle (step S23), the input person can operate the DWS system with the optimal parameter value for the mounted tire (step S24).

[Aspect C]
In this aspect, the simulation is executed by software installed in a personal computer owned by a trader or an individual.
First, in step S30, software for analyzing and calculating the optimum parameter value for a vehicle equipped with a DWS system and a tire mounted on the vehicle is installed in a personal computer of a vendor or an individual.

Next, information (vehicle name, installed tire brand, tire size) necessary for the simulation is input from the input means equipped on the in-vehicle computer (step S21). Next, using the vehicle data managed in the analysis software and the tire characteristic data obtained from the tire manufacturer, an analysis calculation of the optimum parameter value is executed on a personal computer owned by the trader or individual (step S32). .
Next, when the optimum parameter value obtained as an output is input to the DWS system (step S33), the DWS system can be operated with the optimum parameter value for the mounted tire (step S34).

The vehicle information may include factors related to the vehicle's motion performance, and since it is considered very unlikely that the vehicle information will be disclosed to the general public by the vehicle company, a third party cannot browse the vehicle-mounted computer in advance. So that only managers (site or server operators (Aspect B), software manufacturers or administrators (Aspect C)) who have specific confidentiality obligations can obtain such information. Can be considered.
In addition, the tire characteristics required as tire information are not publicly disclosed, but these characteristic values are not obtained from the tire manufacturer's specific internal structure or material composition information, but are obtained by obtaining the tire and measuring the tire alone. It is information that can be.

It is a flowchart which shows one Embodiment of the setting method of this invention. It is a flowchart which shows an example of the parameter setting method in a tire pressure fall detection method. It is a flowchart which shows the other example of the parameter setting method in the tire pressure fall detection method. 10 is a flowchart showing still another example of a parameter setting method in the tire pressure drop detection method. It is a figure explaining the input item for creating a vehicle model. It is a figure explaining the input item for creating a vehicle model. It is a figure explaining the input item for creating a vehicle model. It is a figure which shows the relationship between the decompression determination value DEL and vehicle speed by simulation and a real vehicle test.

Claims (2)

A method for setting an alarm threshold in a tire air pressure decrease detection method for detecting a decrease in tire air pressure based on a wheel rotation speed obtained from a tire mounted on a four-wheel vehicle,
A vehicle model creation step for creating a vehicle model including a suspension member;
Creating a tire model that can represent the characteristics of the longitudinal force of the tire at least at the time of normal internal pressure and reduced pressure;
Inputting a coefficient of friction between the tire and the road surface;
Inputting data including a front projected area of the vehicle, a reference point on which aerodynamics acts, an air drag coefficient, and an air lift coefficient that express air resistance generated in the vehicle during traveling;
A simulation step of performing a running simulation of the vehicle model on which the created tire model is mounted, and the air pressure of the drive wheel tire is determined based on the wheel rotational speed of the tire of each of the four wheels obtained in the simulation step. A method for setting an alarm threshold in a method for detecting a decrease in tire air pressure, wherein an alarm threshold for determining whether or not the tire pressure has decreased is set.   The vehicle model includes vehicle characteristic values including vehicle gravity center position, vehicle moment of inertia, wheelbase length, vehicle front and rear wheel track width, vehicle weight, suspension spring spring characteristics, damper damping characteristics, and roll center height. The alarm threshold value setting method in the tire pressure drop detecting method according to claim 1, which is created by

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