Electricity: measuring and testing – Electrical speed measuring – Including speed-related frequency generator
Reexamination Certificate
2000-04-12
2001-06-12
Strecker, Gerard R. (Department: 2862)
Electricity: measuring and testing
Electrical speed measuring
Including speed-related frequency generator
C324S173000, C324S249000, C702S148000
Reexamination Certificate
active
06246226
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tire revolution detection method and apparatus for detecting the revolution of a tire and a tire revolution speed detection method and apparatus for measuring the speed, traveled distance, and the like of a vehicle such as an automobile or the like on the basis of the tire revolution per minute (rpm) of the vehicle and, more particularly, to a wheel revolution detection method and apparatus, a tire revolution detection method and apparatus, and a tire revolution speed detection method, which magnetically detect the revolution or revolution speed of a wheel or tire.
2. Description of the Related Art
Car navigation systems used for confirming the current position of a vehicle, navigating a vehicle, and so on have come into existence in about 1990, and have become popular.
A car navigation system has a function of detecting absolute position on the basis of radio waves from a satellite by GPS (GLOBAL POSITIONING SYSTEM) navigation. In recent years, systems using a hybrid system with a self-contained navigation that indicates the traveling condition of a vehicle on the basis of the angular deviation detected by a gyro sensor and vehicle speed data from the vehicle main body have increased and become dominant. The hybrid system can improve map matching precision.
However, in order to obtain the self-contained navigational function, vehicle speed data must be acquired from the vehicle main body. For this purpose, a user must ask an expert having the diagram of the vehicle main body for connecting the system. Such connections are hard to do by a normal user, and high cost and connections requiring an expert prevents wider user of car navigation systems in future.
SUMMARY OF THE INVENTION
The above-mentioned problems can be solved if a sensor that detects the revolution or revolution speed of a tire to measure the vehicle speed or traveled distance, and can be easily attached can be supplied. As an ideal method, it is most preferable to detect the revolution or revolution speed of the tire in a non-contact manner.
The present inventors considers the fact that steel radial tires have become popular, and such tire has a steel belt inside the outer circumferential portion. The present inventors postulated that the steel belt has residual magnetization albeit its weak strength, and this residual magnetization radiates a magnetic field outside the tire. In fact, when the magnetic field was measured by revolving the tire once, a magnetic field distribution shown in
FIG. 10
appeared. The measurement was done along the outer circumferential portion at a position about 15 cm from the tire. As shown in
FIG. 10
, a clear peak is present in correspondence with one revolution of the tire, and feasibility of magnetic detection of the revolution of the tire is suggested.
However, the peak-to-peak value of the magnetic field from the tire is 0.38 G, and is smaller than geomagnetism (about 0.5 G). In some cases, the magnetic field may become smaller than 0.1 G depending on the types of tires and the setting positions of the sensor.
In order to satisfactorily obtain magnetic detection of the revolution or revolution speed of such tire, the following conditions must be satisfied.
i) Sensor Arrangement
The sensitivity of a magnetic sensor requires several mG in consideration of resolution. On the other hand, A state of the sensor caused by magnetization does not change such as a flux gate sensor.
ii) Sensor Setting
The sensor must be easy to set in a vehicle. Also, the sensor must be set at a position suitable for magnetic field detection.
iii) Removal of Influences of Disturbances
The influences of magnetic fields that act as disturbances produced by residual magnetic fields of iron reinforcing rods, steel frames, and the like of bridges, tunnels, and the like must be removed.
It is an object of the present invention to provide a tire revolution detection method and apparatus, which can satisfy the above-mentioned conditions, and satisfactorily attain magnetic detection of the revolution of a tire, and a tire revolution speed detection method, which can satisfactorily attain magnetic detection of the revolution speed of the tire.
In order to achieve the above object, a wheel revolution detection method according to the present invention adopts a wheel revolution detection method for detecting a revolution of a wheel provided to a vehicle, comprising the steps of:
using the wheel provided with magnetic field generation means for generating a magnetic field;
setting magnetic field detection means inside the vehicle for detecting the magnetic field generated by the magnetic field generation means; and
detecting revolution of the wheel by detecting a change in magnetic field upon revolution of the wheel by the magnetic field detection means.
According to this method, since the magnetic field detection means can be easily attached to the vehicle to detect the revolution of the wheel, even an average user can easily attach the magnetic field detection means to detect the revolution of the wheel.
A wheel revolution detection apparatus according to the present invention adopts a wheel revolution detection apparatus for detecting a revolution of a wheel provided to a vehicle, comprising:
magnetic field generation means, provided to a member which rotates together with at least one wheel, for generating a magnetic field; and
magnetic field detection means for detecting the magnetic field generated by the magnetic field generation means,
wherein the magnetic field detection means is arranged inside the vehicle.
With this arrangement, since the magnetic field generation means is attached to the member which rotates together with at least one wheel, and the magnetic field detection means is attached inside the vehicle body, the wheel revolution detection apparatus can be easily arranged on the vehicle. Since the wheel revolution detection apparatus is additionally attached in this manner, when the user attaches a car navigation system, he or she can easily attach the car navigation system without specifying external terminals of a traveled distance sensor and the like, which are arranged in advance. Also, since the magnetic field detection means is arranged inside the vehicle body, it is hardly influenced by rainwater and the like, and can be also prevented from external damages.
A wheel revolution detection apparatus according to the present invention adopts a wheel revolution detection apparatus for detecting a revolution of a wheel provided to a vehicle, comprising:
magnetic field detection means for detecting a magnetic field generated by magnetic field generation means provided to a member which rotates together with at least one wheel,
wherein the magnetic field detection means is arranged inside the vehicle.
With this arrangement, since the magnetic field detection means for detecting the magnetic field generated by the magnetic field generation means attached to the member which rotates together with at least one wheel is attached inside the vehicle body, the wheel revolution detection apparatus can be easily arranged on the vehicle. In this manner, since the wheel revolution detection apparatus is additionally arranged, when the user himself or herself attaches a car navigation system, he or she can easily attach the car navigation system without specifying external terminals of a traveled distance sensor and the like, which are arranged in advance. Also, since the magnetic field detection means is arranged inside the vehicle body, it is hardly influenced by rainwater and the like, and can be also prevented from external damages.
According to the present invention, a tire revolution detection method for detecting revolution of a tire by detecting a magnetic field generated by the tire of a vehicle using a magnetic sensor, comprises the steps of:
using, as the tire, a tire which includes a steel belt in an outer circumferential portion thereof;
setting the magnetic sensor including a pair of magnetic detection elemen
Kaneko Hitoshi
Kawase Masahiro
Sato Hiroshi
Tazaki Shinichi
Urayama Norihisa
Canon Kabushiki Kaisha
Morgan & Finnegan L.L.P.
Strecker Gerard R.
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