Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
2001-04-03
2004-03-09
Chin, Gary (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
C073S105000, C073S146000
Reexamination Certificate
active
06704636
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tire parameter estimation device and a road surface judgment device. More particularly, the present invention relates to a tire parameter estimation device and a road surface judgment device suitable for controlling the running of a vehicle.
2. Description of Related Art
It has been known to estimate tire parameters of tires of a vehicle and to control the running of the vehicle by using the tire parameters. The tire parameters include tire wear amount and tire temperature, for example.
Japanese Patent Application Laid-Open (JP-A) No. 5-332762, for example, discloses a tire abnormal wear detector to estimate the tire wear amount. This tire abnormal wear detector detects abnormal wear of the tire on the basis of the change in the number of revolutions of the tire when a dynamic radius of the tire becomes small due to the wear of the tire. More specifically, the correlation between a resonance frequency (dependent on air pressure) determined on the basis of output of a wheel speed sensor and the number of revolutions of the tire is obtained in advance while taking the change in the dynamic radius due to the air pressure of the time into account, the detector judges that the tire is worn out when the number of revolutions of the tire falling outside this correlation is detected.
However, there has been a problem that this tire abnormal wear detector is only able to detect the tire wear when the dynamic radius becomes uniformly small as the tire is uniformly worn out. Grip force of the tire drops due to the wear of a tire shoulder, for example, but this detector cannot detect such a wear.
Also, to estimate the tire temperature, Japanese National Publication No. 11-504585, for example, discloses a device in which a temperature sensor is provided with a tire housing to transmit a temperature measurement value obtained by this temperature sensor into, or outside, a vehicle compartment. However, this device requires exclusive components such as a slip ring and the temperature sensor to measure the tire temperature, which results in an increase in costs, and there have been problem with durability and reliability.
In addition, tire parameters, which are effected by external environment, such as road surface friction, are effected, by both characteristics of the vehicle and characteristics of the road environment. Moreover, because it is difficult to strictly distinguish between vehicular factors and environmental factors, it is very difficult to estimate the tire parameters by only the behavior of the vehicle and the road state.
It is generally difficult to judge road surface state unless the state of the tire is somehow made close to a critical region (maximum friction region). If such a control is made, however, a change in the behavior of the vehicle occurs, whereby vibration and noise arise, and driving ease and maneuverability deteriorate.
Road surface state can also be grasped by directly measuring the road by sensor disposed on the road, but sensors cannot be installed on an entire road from the aspect of cost. Sensors may be installed partially on the road, but there is no point in installing sensors partially because wear characteristics vary greatly depending on place of the road.
SUMMARY OF THE INVENTION
The present invention is devised in order to eliminate the problems described above. It is an object of the present invention to provide a tire parameter estimation device that is economical and can accurately estimate tire parameters while taking into consideration both vehicular states road and environment states. It is another object of the present invention to provide a road surface judgment device that can easily judge road surface states without having to expend cost on facilities for the road.
According to a first aspect of the present invention, there is provided a tire parameter estimation device, the device comprising: a wheel speed detecting section for detecting a wheel speed; a road surface friction parameter generating section for generating a road surface friction parameter representing a friction state between a tire of a wheel and a road surface on the basis of the wheel speed detected by the wheel speed detecting section; a memory section for storing the road surface friction parameter generated by the road surface friction parameter generating section; and a tire parameter estimation section for estimating at least one tire parameter relating to the tire and the road surface on the basis of the road surface friction parameter stored by the memory section and the road surface friction parameter newly generated by the road surface friction parameter generating section.
According to the first aspect of the invention, the road surface friction parameter generating section generates the road surface friction parameter on the basis of the wheel speed. Here, the road surface friction parameter and the road surface have the correlation, and the road surface friction parameter at the time when the vehicle is running on a reference road surface serves as a reference value. The tire parameter that represents the relation between the road surface and the tire depends on the change of the road surface friction parameter. The road surface friction parameter as the reference value is stored. The tire parameter can thus be estimated on the basis of this road surface friction parameter and the road surface friction parameter that is newly estimated.
According to a second aspect of the present invention, the tire parameter estimation device of the first aspect of the present invention further comprises a reference running state detecting section for detecting a reference running state of a vehicle, wherein the memory section stores the road surface friction parameter at a time at which the reference running state detecting section detects the reference running state, as a reference parameter, and the tire parameter estimating section estimates, as the tire parameter, a tire temperature corresponding to the road surface friction parameter newly generated by the road surface friction parameter generating section by using the characteristics of the tire temperature and the road surface friction parameter with respect to the reference parameter.
According to the second aspect of the present invention described above, the road surface friction parameter at the time when the vehicle is under the reference running state is stored as the reference parameter. When the tire temperature changes, the road friction parameter also changes. The tire parameter estimating section utilizes such a characteristics and estimates the tire temperature on the basis of the road surface friction parameter newly estimated during the vehicle running.
According to a third aspect of the present invention, the tire parameter estimation device of the first aspect of the present invention described above further comprises a reference running state detecting section for detecting a reference running state of a vehicle; a running start detecting section for detecting a start of running of the vehicle on the basis of the wheel speed detected by the wheel speed detecting section; and a writing section for writing into the memory section the road surface friction parameter generated by the road surface friction parameter generating section each time the running start detecting section detects the start of running of the vehicle and the reference running state detecting section detects the reference running state of the vehicle, wherein the tire parameter estimating section estimates a wear amount of the tire as the tire parameter on the basis of a change in a plurality of the road surface friction parameters stored in the memory section.
According to the third aspect of the present invention, the road surface friction parameter generated by the road surface friction parameter generating section is written into the memory section each time the running start judgment section detects the start of running of the vehicle and th
Amano Yasushi
Miyashita Masanori
Sawada Mamoru
Tanaka Akira
Watanabe Yoshitoshi
Chin Gary
Kabushiki Kaisha Toyota Chuo Kenkyusho
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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