Specification
Background of the Invention
Field of the Invention
The present invention relates to a gas refuelling interlock sensor and more specifically to a Non contact type (magnetic) CNG refuelling interlock sensor with Hall IC and disc shape magnets.
Description of the Related Art
Conventional technology uses a contact type switch with inbuilt spring and contact plate, coil spring having a first free end and second end soldered at a point to an electrically conductive plate. From the solder point, a signal wire extends through a strain relief ring terminal and a flexible rubber casing. The distal end of the extension has opening which can be mounted around neck of the fill opening, prior to mounting of the cover, to prevent loss of the cover during fuelling. When the cover is placed fully onto metallic fill opening, the free end of the spring comes in contact with the top of the fill opening. When contact is made the starter Interrupt module permits the engine to start. When there is no contact between Free end of spring and top of fill opening (i.e., the cover is not placed on fill opening). The interrupt module does not permit engine to start.
The conventional technology has the following disadvantages. The contact type switch has a limited life span as it has to make and break contact which results in wear
and tear. Furthermore, due to the wear and tear, the spring burns resulting in the reduction of the life of the switch. The spring set also causes flickering problems. Over a period of time there is lot of wear at the contact points. The spring is retained in the cover by welding or riveting operation. The joints are loosened due to vibrations created by the
wear and tear and thereby results in intermittent operation of the switch. As the contact switch is used to provide starter interlock, due to safety reasons it is not reliable to use contact type switch for such applications in the alternative fuel vehicle.
Objects of the invention
Accordingly, it is a principal object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.
It is another object of the present invention to provide a non contact type (magnetic) CNG refuelling interlock sensor that can be easily and efficiently manufactured and is of durable and solid construction.
It is another object of the present invention to provide a non contact type (magnetic) CNG refuelling interlock sensor in which the life span of the sensor is enhanced considerably.
It is another object of the present invention to provide a non contact type (magnetic) CNG refuelling interlock sensor that has no problems of wear and tear and hence more reliable and safe.
It is another object of the present invention to provide a non contact type (magnetic) CNG refuelling interlock sensor which has self diagnosis features built in it which further enhances the safety.
It is another object of the present invention to provide a non contact type (magnetic) CNG refuelling interlock sensor that uses disc shaped magnets which are readily available in the market and easier to magnetize in bulk quantities.
Yet another object of this invention is to provide a non contact type (magnetic) CNG refuelling interlock sensor that can be operated by a person of ordinary skill.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the accompanying drawings.
Summary of the Invention
The present invention is directed to a non contact type magnetic sensor used to sense presence or absence of CNG Refuelling cap, which substantially obviates one or more problems due to limitations and disadvantages of the related art. It provides ignition interlock as a safety feature to prevent starting of engine, when the gas is being filled and the cap is removed from refuelling valve. Once the filling is complete and the plug is inserted in the normal position on the valve and refuelling cap is closed and the engine can be started.
Accordingly, the present invention provides a gas refueling cap interlock non contact type magnetic sensor comprising: a plurality of disc magnets; at least one ferrous shunt ring; an upper cap; a lower cap having a plurality of circular slots around its
circumference that holds said disc magnets rigidly; a collar being provided on the circumference of said lower cap which supports said ferrous shunt ring; wherein a magnetic circuit alongwith said upper cap and said lower cap is insert moulded to form a refueling cap.
Brief Description of the Accompanying Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the accompanying drawings:
Figure 1, illustrates the exploded view of sensor assembly, according to an embodiment of the present invention;
Figure 2, illustrates the location of the sensor assembly, according to an embodiment of the present invention;
Figure 3, illustrates the cross-sectional view of sensor assembly, according to an embodiment of the present invention;
Figure 4, illustrates the fitting of the shunt ring over the disc magnet surface, according to an embodiment of the present invention;
Figure 5, illustrates the cross sectional view of the refuelling cap, according to an embodiment of the present invention;
Figure 6, illustrates the magnetic flux lines flow from North pole to South pole, according to an embodiment of the present invention.
Detailed Description of the preferred embodiment
Reference will now be made in detail to the preferred embodiment of the present invention, examples of which are illustrated in the accompanying drawings.
Referring to Fig. 1, the sensor assembly of the present invention comprises of a plurality of disc magnets (4), ferrous shunt ring (3), upper cap (2) and lower cap (5). The lower cap (5) has a plurality of circular slots around its circumference which holds the disc magnets (4) rigidly. A collar is provided on the circumference of the lower cap (5) which supports the ferrous shunt ring (3). The inner diameter of the shunt ring (3) fits tightly over each disc magnet surface. The lower cap (5) further has a plurality of holes on its face in which the mating projections in upper cap (2) fix to hold the magnetic circuit securely. The magnetic circuit along with upper cap (2) and lower cap (5) is insert moulded to from a CNG Refuelling cap (1).
The CNG Refuelling cap (1) is mounted on metal bracket by thread joint. The bracket is attached to the vehicle chassis by fasteners. The sensor body is precisely located on bracket with the help of a pip provided on sensor body which fits tightly in hole provided in bracket. Precise Location of sensor body is required to maintain a functional air gap between sensor body and refuelling cap in range of 2.0 ±1.0 mm as shown in fig 2.
The sensor body comprises of a hall sensor soldered on PCB and related electronic circuitry, at the opposite end of PCB wiring harness is soldered.
Magnetic Circuit: More specifically the invention relates to innovative magnetic circuit embedded inside CNG refuelling cap (1). The magnetic circuit comprises of a plurality of NDFEB N40UH Grade magnets. UH grade magnets are selected to withstand higher temperatures during insert moulding. These magnets are axially magnetized, with North and South poles formed on opposite face of disc magnet. The magnetic flux density on surface varies from 3800G - 4000G (Gauss).
Referring particularly to Fig. 5, the plurality of magnets are placed with South pole facing outwards and North pole facing inward. A soft magnetic material ring with ID 40.40 mm, OD 43.40 mm and Thickness 3.0mm is placed over the plurality of magnets such that inner Diameter of ring is in physical contact with each magnets. The complete Inner Diameter of shunt ring acts as North pole and the Outer Diameter and South pole, magnetic flux lines flow from North to South pole. This circuit is similar to a ring magnet with North pole on Inner Diameter and South pole on Outer Diameter.
The cost of magnetization and the overall product cost is reduced by approximately 40% compared to the magnetic circuit with ring magnet.
Referring to Fig. 2 the cross-sectional view of CNG interlock sensor is shown. The hall IC is packaged inside sensor body with operational air gap of 2.0 ±1.0 mm. Hall IC's centre axis is aligned with the magnetic circuit centre axis. When CNG refuelling cap is placed on fill valve, the magnetic flux lines activate hall IC and ground signal is sent to the Starter relay unit and engine is cranked.
Whenever there is no CNG refuelling cap placed on the fill valve, the Hall IC is deactivated, hence no ground signal and no engine crank possible.
As the sensor is non contact type it is highly reliable and safe compared to the contact type design.
Advantages over the prior art
Due to non contact type design, the life cycle of the sensor is greatly enhanced. There are no problems of wear and tear, as it is a non contact type sensor, and hence it is more reliable and safe. Self diagnosis features can be inbuilt with the sensor which further enhances safety. The Low cost magnetic circuit makes it more economically viable as it does not require special ring magnets. It uses disc shape magnets which are readily available in the market, making it easier to magnetize in bulk quantities and makes manufacturing of the sensor easier.
It will be understood from the forgoing that the present invention provides an Non contact type (magnetic) CNG refuelling interlock sensor. More important, this feature of the invention has been achieved in a relatively simple and in a cost effective manner.
As those skilled in the art will understand, there are many variations or alterations of the device that can be made using the principles and devices discovered by the inventor. Therefore, the above description is not intended to be limiting but, instead, illustrative. Accordingly, it is the intention of the inventor to embrace all such variations and alterations as fall within the spirit and broad scope of the invention.
WE CLAIM;
1. A gas refueling cap interlock non contact type magnetic sensor comprising:
a plurality of disc magnets;
at least one ferrous shunt ring;
an upper cap;
a lower cap having a plurality of circular slots around its circumference that holds said disc magnets rigidly;
a collar being provided on the circumference of said lower cap which supports said ferrous shunt ring;
wherein a magnetic circuit alongwith said upper cap and said lower cap is insert moulded to form a refueling cap.
2. The sensor as claimed in claim 1, wherein the inner diameter of said shunt ring fits tightly over each disc magnet surface.
3. The sensor as claimed in claim 1, wherein said lower cap has a plurality of holes on its face in which the mating projections in upper cap fix to hold the magnetic circuit securely.
4. The sensor as claimed in claim 1, wherein said refueling cap is mounted on a metal bracket with the help of a thread joint.
5. The sensor as claimed in claim 4, wherein said bracket is attached to the vehicle chassis with the help of fasteners.
6. The sensor as claimed in claims 4 or 5, wherein a sensor body is precisely located on said bracket with the help of a pip provided on said sensor body which fits tightly in hole provided in said bracket.
7. The sensor as claimed in claim 6, wherein precise location of said sensor
body is required to maintain a functional air gap between said sensor body and said
refueling cap in the range 2.0 ± 1.0mm.
8. The sensor as claimed in claims 6 and 7, wherein said sensor body comprises
a hall element soldered on printed circuit boards and related electronic circuitry, at the
opposite end of said printed circuit boards wiring harness is soldered.
9. The sensor as claimed in claim 1, wherein said magnetic circuit comprises of
a plurality of NdFeb, high temperature grade magnets which are axially magnetized, with
North and South poles formed on opposite face of disc magnet and the magnetic flux
density on the surface varies from 3800G to 4000G (Gauss).
10. The sensor as claimed in claim 1, wherein wherenever there is no CNG
refueling cap is placed on the fill valve, said hall element is deactivated leading to no
ground signal and with no possibility of engine crank.
11. An automobile comprising a gas refueling cap interlock sensor, as claimed in
any of the preceding claims.
12. The gas refueling cap interlock non contact type magnetic sensor, substantially as herein described, particularly with reference to the accompanying drawings.
