A dipstick for an internal combustion engine of an automobile
Field of the invention
The present invention relates to "A dipstick for an internal combustion engine of an automobile" and more particularly to a device for detecting the oil level in an internal combustion engine of a vehicle.
Background of the invention
Internal Combustion Engines require lubrication for reducing the friction between various sliding parts like bearings, gears and shafts. Insufficient lubrication can lead to increased transmission losses, wear and tear of sliding parts and abnormal noise during operation of the engine. Engine oil is used to lubricate the sliding parts and maintain the engine in correct operating condition. For an automobile, insufficient engine oil causes reduced fuel mileage and reduced life of sliding parts. Hence, it is important to maintain sufficient lubricating oil in the engine.
A conventional dipstick has a head that is removeably connected with the engine. Generally the dipstick is removeably connected with a clutch cover of the engine or with the crankcase of the engine. The head is connected to stem that can be inserted into a hole in the clutch cover of crankcase. The stem has visual marks at its lower end indicating the maximum and minimum engine oil level permissible. The user or service personnel remove the dipstick to fill lubricating oil into the engine. The graduated marks in the stem of the dipstick are used to identify the engine oil level. In order to check the engine oil level, the dipstick has to be removed and the oil mark is identified. The position of the oil mark with respect to the visual marks in the stem determines the level of oil in the engine.
Due to negligence on the part of the user or service personnel, there may be conditions wherein the engine oil decreases below the minimum permissible level and still the user continues to operate the engine. Such conditions lead

to reduced fuel mileage, damages to gears and shafts and even engine seizure.
Various types of oil level detection apparatuses for detecting the level of oil
pooled in the crankcase has been disclosed such as those in Japanese Laid -
Open Utility model application no.58-163826, Japanese Laid Open
Application (Kokai) NO.60-331 and Japanese Patent Publication (Kokou) No.
55-45733. These inventions have a magnetic float switch comprising of a
float with a permanent magnet. Whenever the oil level in the crankcase drops
to a pre-determined low level, the float moves downward accordingly and the
reed switch therefore senses the magnetic force of the permanent magnet,
whereby the level drop is detected and an alarm is issued. But mounting
these devices to automobile engines poses several obstacles. Primarily, the
oil level detection apparatus must not interfere with the operation of the
engine. It should be located in a position that is not occupied by other engine
parts. The oil level detection apparatus should be easy to assemble and
service. The length of the magnetic float switch should be sufficient to detect
low engine oil level condition. ■•
Hence it is the main objective of the present invention to provide a low cost 'low engine oil level' signalling device that is easy to manufacture, assemble and service and located in a position that does not affect the operation of the engine will satisfy a much required need of warning the user when the engine oil level decreases below a minimum permissible level.
Brief description of the engine
According to one aspect of the present invention, a dip-stick engine oil level signaling device for an internal combustion engine of an automobile provided with a head removeably connected with the engine, a stem having two ends, first end connected with the said head and the second end inserted into an oil filling opening mounted in the said engine which is characterized in that at least one magnetic proximity sensor is housed with the stem and a float with a permanent magnet located around the stem in such a manner that it rises and falls during changes in oil level with a stopper at the end of the stem opposite

to the head to restrict the movement of the float within the longitudinal length of the stem.
Brief description of the drawings
Figure 1 illustrates an engine assembly for a motorcycle.
Figure 2 is an illustration of the cover clutch along with the dipstick according to the present invention.
Figure 3 is an illustration view of the dipstick according to the present
invention
Figure 4 is an electric circuit to explain the working of the dipstick as an oil level-signaling device in a first condition.
Figure 5 is an electric circuit to explain the working of the dipstick as an oil level-signaling device in a second condition.
Detailed description of the invention
A selected illustrative embodiment of the present invention will be now described with respect to the accompanying figures.
Figure 1 illustrates the principal portion of the engine 102 of the present invention. As shown in this figure, the engine includes a crankcase 201, a cylinder block 202 connected to the crankcase 201, a cylinder head 203 to be connected to the cylinder block 202 and a cylinder head cover. These are clamped and fixed together via stud bolts and the like, thereby constituting the main structure of the engine 102.
The crankcase has a structure in which tfie half cases 204 & 205 are integrally connected to each other. The halves cases and are formed by dividing the crankcase into right 205 and left portions 204. In the crankcase, formed of the combined half cases and, a crankshaft is rotatable bearing (not shown in the figure) supported. A connecting rod (not shown in the figure) is rotatable attached to a crankpin of the crankshaft (not shown in the figure) via a bearing located at the large-end thereof. A piston (not shown in the figure) is pivotally attached to the small-end of the connecting rod via a piston pin (not

shown in the figure). In this embodiment, there is provided one piston and the engine of the present invention is a single cylinder 4-cycle engine. A dipstick 301 for the said internal combustion engine 102 of an automobile comprises of a head 302 removeably connected with the engine 102, a stem 303 for inserting into an oil filling opening 304 in the engine 102 which is characterized in that at least one magnetic proximity sensor is housed within the stem 303 and a float 306 with a permanent magnet 307 is located around the stem 303 such that the It rises and falls during the rising and falling of the engine oil level. There is also provided a stopper 308 at the end of the stem 303 opposite to the head 302 restricts the movement of the float 306 within the longitudinal length of the stem 303.
Referring to Figures 1, Figure 2 and Figure 3, all-inclusive, the dipstick 301 is located in the cover clutch 206 side of the motorcycle engine 102. There is an opening 304 in the cover clutch 206 through which the dipstick 301 is removeably connected. The dipstick 301 has a head 302 that has threads at its outer surface for fastening to the cover clutch 206. The head 302 is connected to a hollow cylindrical stem 303 at the lower end. There^is a float 306 in the shape of an annular cylinder that can move along the longitudinal length of the stem 303. The float 306 is made of foam nylon and a permanent magnet 307 in the form of an annular cylinder is housed coaxially within it. There is also a stopper 308 In the form of a circular plate that restricts the movement of the float 306 within the longitudinal length of the stem 303. There is also provided a wiring harness 315 and connector 314 for connecting the dipstick 301 to an electric circuit.
Referring to Figure 4, a reed switch is housed within the stem 303. The reed switch 310 has electrical contacts that close when a magnetic field of sufficient intensity is placed nearby. In the preferred embodiment, a reed switch 310 that requires 20-60 AT magnetic intensity to close contacts is used. The reed switch 310 is normally open so that the bulb 311 does not glow when a battery 312 is connected as per the electric circuit 313. When the dipstick 301 is connected with the cover clutch 206 in the engine 102, the float 306 moves along the longitudinal length of the stem 303 to reach the engine oil level.

Referring to Figure 5, wlien the lubricating oil level in the engine 102 decreases, the float 306 moves downward along the longitudinal length of the stem 303. The reed switch 310 is positioned at a pre - determined height from the stopper 308 such that the float 306 comes in close proximity to the reed switch 310 when the engine oil level decreases to a pre - determined low level. At this level, the reed switch 310 contacts close and the bulb 311 glows when a battery 312 is connected as per the electric circuit 313. Thus the dipstick 301 that can be used to warn the user provides a low engine oil level.
In the place of reed switch 310, other magnetic proximity sensing devices like hall sensors can also be used. A plurality of magnetic proximity sensors can be embedded at different heights with respect to the stopper to signal different engine oil levels. The reed switch 310 can also be a normally closed type wherein the reed switch contacts are initially closed and when brought in close proximity to a magnetic field, the contacts open. An electric circuit 313 to provide warning signals to the user and to control the operation of the engine 102 accordingly can detect the change of state.
The cross section of the stem 303 can also be rectangular or trapezoidal in shape and the float can also have similar cross sections.
For engines 102 in which the hole for filling oil is provided in the crankcase 201, the dipstick can be connected to the crankcase 201 also.
The head 302 can also be in the shape of a knob to enable a user to remove and fit the dipstick 301 to the engine 102 comfortably.
Foam nylon is used herq as a float material which can withstand high, temperatures of up to 150 degree Celsius.
Strontium Ferrite magnet is used here as the permanent magnet inside the float 306 which can withstand high temperatures of up to 300 degree Celsius, and has high residual flux density and is relatively inexpensive.
The dipstick 301 can be used to perform the functions of enabling the user to fill lubricating oil for the engine 102 and signal a predetermined low engine oil level condition. The signal can also be used by a system to control the

operating parameters of the engine 102 like ignition timing (in the case of spark ignition), fuel injection timing (in the case of fuel injection) etc. Moreover, the present invention enables the user to determine the condition of the engine oil level without disturbing the operation of the engine and easy to assemble and service at a less costs.
Although the subject matter has been described In considerable detail with respect to certain preferred embodiments thereof, other embodiments are possible. As such, the spirit and scope of the appended claims should not be limited to the description of the preferred embodiment contained therein.


Claims: We claim:
1. A dipstick for an internal combustion engine of an automobile,
comprising:
a head removeably connected to the engine;
a stem having two ends, first end connected with the said head and the second end inserted into an oil filling opening mounted in the said engine which is characterized in that at least one magnetic proximity sensor is housed with the stem and a float with a permanent magnet located around the stem in such a manner that it rises and falls during changes in oil level with a stopper at the end of the stem opposite to the head to restrict the movement of the float within the longitudinal length of the stem.
2. A dipstick as claimed in claim 1, wherein the said head is connected with a cover clutch of the said engine.
3. A dipstick as claimed in claim 1, wherein the said magnetic proximity sensor is a reed switch.
4. A dipstick as claimed in claim 1, wherein the said head is a knob for closing or opening the said dip-stick during engine oil filling.
5. A dipstick as claimed in claim 1, wherein the said float is an annular cylinder.
6. A dipstick as claimed in claim 1, wherein the said stem is cylindrical in shape.
7. A dipstick as claimed in claim 1, wherein the said float is made of foam nylon.
8. A dipstick as claimed in claim 1, wherein the said stem is made of a polymer resin.

9. A dipstick as claimed in claim 1, wherein tiie said pemianent magnet is
a ferrite magnet.
10. A dipstick as lierein substantially described and illustrated with
reference to the accompanying drawings.