GB2141238A - Positioning a geomagnetic field sensor on a vehicle - Google Patents

Abstract

A method of positioning a geomagnetic field sensor on a vehicle comprises mounting the sensor 2 on the vehicle in a position in which the main sensing axis B of the sensor is directed to be substantially perpendicular to the direction A of a magnetic field as developed by the crossing magnetization of the vehicle body. <IMAGE>

Description

SPECIFICATION Application method for geomagnetic field sensors The present invention relates to an application method for geomagnetic field sensors, and more particularly, to an application method for a geomagnetic field sensor for vehicles such as automobiles.

The geomagnetic field sensorforvehicles is generally made use of, mounting on a vehicle, as a sensor such as for a bearing meter which measures, by detecting the geomagnetic field, e.g. the traveling direction of such vehicle. As a typical one available for such application, there may be employed a geomagnetic field sensor of a flux gate type of a toroidal core design for example.

Incidentally, vehicles such as automobiles have a magnetizing characteristic whereby, such as when going over the crossing of any electric railroad, a floor portion of the vehicle body and the like are magnetized by any magnetic field developed by any transmission line the vehicle is crossing, which phenomenon is generally called "crossing magnetization" of such vehicle. Therefore, for any geomagnetic field sensor mounted on the body of such vehicle, there is needed to be provided a consideration which permits the sensor to be sensitive to the geomagnetic field without influences from the crossing magnetization.

In this respect, conventionally, such sensor has been arranged, with a horizontal position, in the vicinity of a mascot piece on a bonnet of such vehicle. According to an example of such conventional application method, as illustrated in the prior art drawing Figure 3, a geomagnetic field sensor 32 is horizontally arranged in the vicinity of a mascot piece disposed near the front end of an automobile 30, of which vehicle body has a floor portion 30a magnetized due to the crossing magnetization into a longitudinal magnet 31 developing a magnetic field around the automobile 30. The magnetic field is directed in an ascending direction nearthe front end of the automobile 30, thus crossing the main sensing axis of the sensor 32 substantially at right angles, thereby keeping the sensor 32 non-sensitive to the magnetic field.Accordingly, no error due to the crossing magnetization is detected by the sensor 32.

However, for the bonnet of the automobile 30 has therein accommodated various electrical equipments and apparatus such as engine related electrical implements, a battery, an alternating-current generator, and an air-conditioning clutch, the sensor 32 disposed in the vicinity of the mascot piece is subjected to a leaked magnetic flux of such equipments, thus requiring a certain countermeasure against the leaked magnetic flux, needing an additional production cost.

Moreover, as shown in Figure 3, a geomagnetic field sensor32 may be horizontally arranged near the rear end of the automobile 30, where the magnetic field due to the crossing magnetization has a descending direction. However, such sensor location is still subjected to unexpected influences of luggages in a trunk room, thus causing undesirable errors.

The present invention has been achieved to over come such problems in conventional application methods for geomagnetic field sensors.

An object of the present invention is to provide an application method for a geomagnetic field sensor for vehicles such as automobiles, which method permits the geomagnetic field sensor to be applied to such vehicle, without influences from the crossing magnetization, but with a relatively large freedom in the selection of sensor location.

According to the present invention, there is provided an application method for a geomagnetic field sensor fora vehicle with a vehicle body, comprising the step of applying the sensor to the vehicle, having the the main sensing axis of the sensor directed to be substantially perpendicular to the direction of a magnetic field developable by the crossing magnetization of the vehicle body.

The above and further features, objects and advantages of the present invention will more fully appear from the following detailed description of the preferred embodiment of the invention when the same is read in conjunction with the accompanying drawings, in which: Figure 1 is a side view of an essential front part of a vehicle to which a geomagnetic field sensor is applied according to the present invention; Figure 2 is a graph showing the output characteristic for various application angles of the geomagnetic field sensor of Figure 1; Figure 3 is a side view of a vehicle to which a geomagnetic field sensor is applied according to a prior application method; and Figure 4 is a detailed longitudinal left side view of a mounting implement for mounting the geomagnetic field sensor of Figure 1.

First, there will be described below the constitution and function of a flux gate type geomagnetic field sensor to which the present invention is favorably applicable. As well-known in the art, the flux gate type geomagnetic field sensor is composed of a toroidal core and three windings wound thereon, i.e., a single exciting winding for exciting the core and a pair of output windings for detecting to output the density of magnetic flux tubes linking with the core, the output windings being directed to be spatially perpendicular of the axis with respect to each other.Accordingly, relative to the direction of the magnetic field to be detected, i.e., to the tangential direction of the magnetic force line, the geomagnetic field sensor has a most-sensitive position thereof most sensitive in the detection of the magnetic field and a non-sensitive position thereof perpendicular to the most-sensitive position and non-sensitive to the magnetic field. In other words, when given a fixed spatial position, the geomagnetic field sensor has fixed a main sensing axis thereof and a characteristic non-sensitive plane therearound perpendicular to the main sensing axis, such that any sufficiently strong magnetic field developed in parallel with the main sensing axis is detectable by the sensor at a highest sensitivity while any magnetic field in parallel with the non-sensitive plane is substantially unable to be detected to be output by the sensor.

Referring now to Figure 1, designated at reference numeral 1 is an ordinary automobile having a vehicle body defining a passenger room provided with front and rear passenger seats. Any magnetic field developed by the crossing magnetization is generally representable by a vector field consisting of a set of magnetic force vectors which are directed nearthe front seat in a rearwardly ascending direction A. Near the front seat, on an instrument panel 5, there is arranged a geomagnetic field sensor 2 with the main sensing axis thereof directed in a direction B substantially perpendicular to the vector direction A, so that the sensor 2 is substantially non-sensitive to the magnetic field developed by the crossing magnetization.Namely, to be non-sensitive to the crossing magnetization, the geomagnetic field sensor 2 has declined the main sensing axis, favorably by approximately 45 degrees for instance, from the reference horizontal plane of the automobile.

The geomagnetic sensor 2 may be favorably located in the instrument panel 5 or in the space between a room mirror 3 and a front windshield 4 or accommodated in a casing 6 of an instrument such as a bearing meter placed on the instrument panel 5, provided that the main sensing axis of such sensor is declined from the reference horizontal plane of the automobile.

In this respect, the location into the space between the room mirror 3 and the front windshield 4 may favorably hide the geomagnetic field sensor 2 from the sight of driver, and that onto the instrument panel 5 may effectively eliminate or reduce undesirable projections and contribute to the interior design, while achieving an easy and simple mounting method. Also the accommodation into the casing 6 may favorably save the trouble for mounting, while partially omitting the step of wiring harness installation, thus contributing the realization of an inexpensive production cost.

Referring now to Figure 4, on the instrument panel 5, there is provided a mounting instrument for mounting thereon the geomagnetic field sensor 2, which instrument comprises a holder 8 for holding in position the sensor 2, the holder 8 ascending rearwardly from the horizontal top surface of the instrument panel 5, and a detachable cover plate 7 for covering from above the sensor 2, the cover plate being screwed to the holder 8.

Referring now to Figure 2, when the automobile equipped with the geomagnetic field sensor 2 having the main sensing axis thereof declined by approximately 45 degrees from the reference horizontal plane traces a circle on a geographic plane stretched east, west, north, and south, the geomagnetic field as detected to be output by the sensor 2 will draw an ellipse C when represented by way of a radius vector.

In this respect, in case such sensor is mounted with a horizontal position or put in parallel with the reference horizontal plane of the automobile, the detected geomagnetic field will give a true circle D which is preferable as an output characteristic in comparison with the sensor 2 mounted with the declination of approximately 45 degrees that has drawn the ellipse C with the center deviated from the original point. Therefore, by way of a well-known correction method, the magnetic field as output in the form of the ellipse C may be properly converted into a set of useful output signals representing a true circle, taking into consideration the deviation of the center as well as respective lengths of the major and minor axes of the ellipse C.

In Figure 2, designated at reference numeral E is an elliptic representation of the geomagnetic field as detected by a similar sensor declined to be substantially perpendicular to the reference horizontal plane of the automobile. As will be comprehended from the ellipse E, the sensor 2 may be favorably applied by restricting the declination angle thereof which, when set steep, may render difficult the necessary exact measurements such as of the major and minor axes of such ellipse.

In the foregoing embodiment, the geomagnetic field sensor 2 is disposed near the front seat in the passenger room of the automobile. In this respect, such seansor may be favorably installed behind the rear seat of the automobile, where the magnetic force vectors by the crossing magnetization generally have a rearwardly descending direction.

As will be understood from the foregoing description, according to the present invention, commercially available geomagnetic field sensors can be favorably installed in a vehicle such as an automobile, without influences from the crossing magnetization nor of leaked magnetic flux of electrical apparatus, but with a relatively large freedom in the selection of sensor location, while contributing to the betterment of the appearance associated with the sensor application as well as to the achievement of an inexpensive production cost of the vehicle.

Although there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that the present invention may be embodiment in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrective. The scope of the invention is indicated by the appended claims rather than by the foregoing description.

Claims (7)

1. An application method for a geomagneticfield sensor for a vehicle with a vehicle body, comprising: a step of applying said sensor to said vehicle, having the main sensing axis of said sensor directed to be substantially perpendicular to the direction of a magnetic field developable by the crossing magnetization of said vehicle body.

2. An application method according to claim 1, wherein: said applying step has a step of locating said sensor between a room mirror of said vehicle and a front windshield thereof.

3. An application method according to claim 1, wherein: said applying step has a step of locating said sensor on an instrument panel of said vehicle.

4. An application method according to claim 1, wherein: said applying step has a step of locating said sensor in an instrument casing disposed in an instrument panel of said vehicle.

5. An application method according to claim 1, wherein: said applying method has a step of locating said sensor near a rear seat of said vehicle.

6. An application method according to claim 1, wherein: said applying step has a step of declining said sensor by approximately 45 degrees from the reference horizontal plane of said vehicle.

7. An application method for a geomagnetic field sensor for a vehicle with a vehicle body, substantially as hereinbefore described, with reference to the accompanying drawings.