JPH06307913A - Oil level sensor - Google Patents

Abstract

PURPOSE:To allow the positive detection of engine oil level in an oil pan using a simple and inexpensive structure. CONSTITUTION:The oil level sensor 21 is arranged in an oil pan and a detection part 27 touches the engine oil when it is higher than a predetermined level. A positive characteristic thermister 28 is disposed at the detection part 27 while being covered with a cover 29. The cover 29 has a bottom part provided with a hole part 29c and a side wall part provided with a vent 29d. The cover 29 prevents the engine oil, scattered by the rotation of engine, from touching the positive characteristic thermister 28 positively and delays the variation of the engine oil within the cover 29 due to an abrupt variation of engine oil level thus eliminating the need at delay circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oil level sensor adapted to detect the level of engine oil in an oil pan.

[0002]

2. Description of the Related Art As an oil level sensor of this type,
For example, if a float with a magnet attached is placed on the engine oil in an oil pan so that it floats and moves along with the engine oil level, and the float drops below a certain level, the magnet attached to the float will lead There has been one configured to detect a decrease in the engine oil level by operating a switch.

However, since the viscosity of the engine oil is high immediately after the engine is started or when the temperature of the engine oil is low, such as in a cold region,
The float may not follow the liquid level of engine oil. In this case, if the float remains stopped at a high position even if the engine oil level is lower than the predetermined level, it may cause an erroneous determination that the engine oil level is above a predetermined level and is in a normal state. there were.

Therefore, conventionally, in order to avoid the above-mentioned inconvenience, the structure shown in FIGS. 11 and 12 is adopted. That is, in FIG. 11, the annular float 1 is the engine oil 2 in the oil pan (not shown).
Support 4 of arm 3 so as to move following the liquid surface of
Is arranged so that it can move up and down within a predetermined range. A magnet 5 is attached to the upper portion of the inner surface of the float 1.

The reed switch 6 provided inside the support body 4 is provided so as to be turned on and off by the magnetic force received from the magnet 5 as the float 1 moves.
The reed switch 6 is turned off when the level of the engine oil 2 drops below a predetermined level. The thermoswitch 7 is arranged inside the support 8 of the arm 3 so that the detection part thereof is immersed in the engine oil 2. The thermoswitch 7 is made of a temperature sensitive ferrite, and is turned off when the temperature of the detection unit exceeds a predetermined temperature. Therefore, for example, it is possible to detect a state in which the temperature of the engine oil 2 becomes equal to or higher than a predetermined temperature after the engine is started and the viscosity thereof decreases.

In FIG. 12 showing the electrical configuration, the positive terminal of the battery 9 is connected to the delay circuit 11 via the ignition switch 10 and is also grounded via the series circuit of the warning lamp 12 and the transistor 13. . The signal input terminal of the delay circuit 11 is grounded via the parallel circuit of the reed switch 6 and the thermoswitch 7, and the output terminal is connected to the base of the transistor 13. When the reed switch 6 and the thermo switch 7 are both turned off, that is, when the temperature of the engine oil 2 is equal to or higher than a predetermined temperature (for example, 55 ° C. or higher) and equal to or lower than a predetermined level, the delay circuit 11 is provided. A timer operation is started and a predetermined delay time (for example, 20
If the OFF state of the switches 6 and 7 continues after the lapse of (seconds), the transistor 13 is turned on and the warning lamp 12 is energized and lit.

According to the above configuration, when the temperature of the engine oil 2 is low, the detection operation is not output by the thermoswitch 7, so that the viscosity of the engine oil 2 is high as described above. Float 1
It is possible to prevent erroneous detection due to the stop of the movement of the. It should be noted that the delay circuit 11 causes the shortage of the engine oil 2 during the period when the liquid level of the engine oil 2 temporarily fluctuates and drops below a predetermined level, or when the level immediately returns to above the predetermined level. The warning lamp 12 is provided so as not to detect the flicker when the warning lamp 12 is turned on.

[0008]

However, the conventional structure as described above has the following problems.
That is, first, because the float 1 is used for detection, it is difficult to reduce the size of the entire device, and for the above reason, the thermoswitch 7 is provided so that the detection operation is not performed when the engine oil 2 is at a low temperature. Since it is configured to prevent erroneous detection, the detection operation cannot be performed at low temperature in principle. Also, the reed switch 6
In addition to this, since the thermoswitch 7 for preventing erroneous detection is provided, the structure becomes complicated, and further, it is necessary to provide the delay circuit 11 so as to prevent so-called chattering. is there.

Therefore, in order to solve the above problems,
Conventionally, for example, it has been considered to use a thermistor whose resistance value changes according to temperature as a level detection element to detect the level of engine oil. This is because, for example, a thermistor having a positive characteristic is arranged at a position of a predetermined level to detect the thermistor, and when the thermistor is energized to generate Joule heat, the terminal voltage of the thermistor is detected and It is configured to judge whether the vehicle is in the air or in the air. This utilizes the fact that the amount of heat absorbed by the thermistor that is generating heat differs depending on whether the engine oil or air is in use, and the shared voltage corresponding to the resistance value of the thermistor at that time is compared with a specified reference voltage to make the engine oil It is intended to detect whether or not there is a predetermined level or more depending on the presence or absence of.

However, in such a structure, since the thermistor is soaked in the engine oil and the heat is transferred in the state of being in contact with the thermistor to detect the heat, the oil pan of the oil pan is rotated when the engine is rotated at a high speed. If engine oil splashes and drops from the upper engine side, the splash may adhere to the thermistor. Then, for example, even if the level of the engine oil level is below a predetermined level, heat is absorbed by the splash of engine oil adhering to the thermistor, and the engine oil is erroneously detected as above the predetermined level. There is a risk of being lost.

The present invention has been made in view of the above circumstances, and an object of the present invention is to make a simple and inexpensive structure using a positive temperature coefficient thermistor, and to detect an erroneous detection due to a droplet of engine oil adhering to the positive temperature coefficient thermistor. An object of the present invention is to provide an oil level sensor which can prevent the above and always detect the engine oil level in the oil pan.

[0012]

SUMMARY OF THE INVENTION The present invention is directed to an oil level sensor for detecting the level of engine oil in an oil pan. When the engine oil in the oil pan is at or above a predetermined level, it is immersed. And a positive temperature coefficient thermistor that is provided in the detection unit and generates Joule heat according to the energizing current when a predetermined voltage is applied via a resistor. A characteristic is that a cover provided so as to cover the upper portion of the characteristic thermistor and a detection means for detecting that the engine oil is present at a predetermined level or higher based on the shared voltage of the positive characteristic thermistor are provided. Have.

[0013]

According to the oil level sensor of the present invention, when the positive temperature coefficient thermistor is energized, the positive temperature coefficient thermistor generates Joule heat according to the energized current, and the comparing means operates the positive temperature coefficient thermistor at that time. By comparing the shared voltage and the reference voltage, it is possible to detect that the engine oil in the oil pan is above a predetermined level when a predetermined relationship is obtained. At this time, since the positive temperature coefficient thermistor is arranged with its upper portion covered by the cover, when performing the detection operation, for example, engine oil splashes generated by the rotation of the engine are scattered from above. In this case, the positive temperature coefficient thermistor does not directly adhere to the positive temperature coefficient thermistor, and in particular, it is possible to reliably prevent erroneous detection even when the level of the engine oil level in the oil pan is below a predetermined level. Become.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG.
It will be described with reference to FIGS. As shown in FIG. 2, the oil level sensor 21 is fixed to a side wall portion of an oil pan 22 arranged in the lower part of the engine. Engine oil 24 is stored in a lower oil sump 22a partitioned by a baffle plate 23 in the oil pan 22, and is pumped up by an oil pump via a strainer (not shown) provided in the oil sump 22a. Is supplied to the inside of the engine.

As shown in FIG. 1, the oil level sensor 21 has a crank-shaped arm 2 from a mounting and fixing portion 25.
6 is extended, and this arm 26 includes a baffle plate 23.
The oil reservoir 22a is inserted through the opening 23a, and the detector 27 is provided at the tip of the oil reservoir 22a. The detecting unit 27 is arranged so as to be immersed in the engine oil 24 when the engine oil 24 is at a normal level in the attached state shown in the drawing.

As shown in FIG. 4, a positive temperature coefficient thermistor 28 is disposed inside the detecting unit 27, and a cover 29 (FIG. 3) covers the positive temperature coefficient thermistor 28.
(See also). The cover 29 is composed of a case 29a integrally formed so that the lower surface is opened, and a flat plate-like lid 29b attached to the case 29a so as to close the opened bottom portion. Is fixed to the arm 26 by rivets 27a at two points.

The central portion of the lid 29b is shown in FIG.
As shown in, a hole 29c through which the engine oil 24 can flow is formed, and a side wall has a hole 29d for venting air downward. One terminal of the positive temperature coefficient thermistor 28 is connected to the arm 26 via the rivet 27a, and the other terminal is connected to the terminal portion 30a of the lead wire 30. The signal output of the positive temperature coefficient thermistor 28 is transferred via the lead wire 30. And is output to the terminal 25a of the mounting and fixing portion 25.

In the detection unit 27, the engine oil 24 in the oil pan 22 flows into the interior through the hole 29c in the lower surface of the cover 29 (see arrow A in the figure).
The positive temperature coefficient thermistor 28 is immersed, and at this time, the air inside the cover 29 escapes to the outside through the air vent hole 29d in the side wall portion (see arrow B in the figure). As a result, the liquid levels of the engine oil 24 inside and outside the cover 29 of the detection unit 27 are made the same.

Further, even when the liquid level of the engine oil 24 in the oil pan 22 is wavy due to vibration or the like, the cover 29 prevents the engine oil 2 inside the cover 29.
4 has a wave-dissipating function of reducing the fluctuation of the liquid surface to reduce the fluctuation of the liquid surface. Further, since the cover 29 is arranged so as to cover the upper side of the positive temperature coefficient thermistor 28, even when the engine oil 24 is scattered inside the oil pan 22 due to the rotation of the engine (not shown), the cover 2
Since the splash of the engine oil 24 is prevented from entering the inside of 9, the positive temperature coefficient thermistor 28 is prevented from directly contacting and coming into contact therewith.

FIG. 5 shows an electrical configuration. The output terminal of the positive temperature coefficient thermistor 28 is led out from the lead wire 30 described above and is connected to the on-vehicle battery 3 via the energizing resistor 31.
An energizing circuit 33 is formed by being connected to the positive electrode terminal of No. 2. A common connection point between the positive temperature coefficient thermistor 28 and the energization resistor 31 is connected to an inverting input terminal of a comparator 34 as a comparison means. Voltage generation circuit 35 for setting reference voltage
Is formed by connecting a series circuit of resistors 36 and 37 for generating a reference voltage between the positive terminal of the vehicle-mounted battery 32 and the ground, and its common connection point is connected to the non-inverting input terminal of the comparator 34. There is. The output terminal of the comparator 34 is connected to the output terminal P. Then, as described above, the detection circuit 3
8, the output terminal P is connected to a control circuit (not shown) to provide a detection output.

Next, the characteristics of the positive temperature coefficient thermistor 28 will be described in detail with reference to FIG. The positive temperature coefficient thermistor 28 in this embodiment is formed by using, for example, a barium titanate-based material, and should be improved by adjusting the composition of the barium titanate-based material and the content of additives. Therefore, as shown by the solid line in the figure, the negative temperature coefficient in the low temperature region is set to be larger than that of the conventional one, and the positive temperature coefficient in the high temperature region is made smaller than that of the conventional one. It is set. Further, the positive temperature coefficient thermistor 28 is formed so as to have the specific resistance as small as possible (for example, 20 to 30 Ωcm) while having the above characteristics.

The broken line in the figure shows the general characteristic of the conventional positive temperature coefficient thermistor shown for comparison.
The conventional positive characteristic thermistor has a weak negative characteristic in a low temperature region and a strong positive characteristic in a high temperature region. Further, the lowest resistance value in the conventional PTC thermistor is generally several hundred Ω. The characteristic curve in FIG. 6 is shown in a state where the minimum resistance value of the characteristic curve of the conventional positive characteristic thermistor matches the characteristic curve of the positive characteristic thermistor 28 in the present embodiment, but in reality, the characteristic curve in the present embodiment. The positive characteristic thermistor 28 has a lower absolute resistance value, so that the characteristic curve is also located below.

The conventional method of using the positive temperature coefficient thermistor is as shown in FIG.
It is generally used in the part corresponding to the middle and high temperature range, that is, in the part where the resistance value changes greatly, and in its usage method, the fact that the resistance value changes greatly is actively used. However, the portion having the negative characteristic in the low temperature region is not actually used.

Unlike the conventional one, the positive temperature coefficient thermistor 28 in this embodiment positively uses a portion having a negative characteristic in a low temperature region and also uses a portion having a positive characteristic in a high temperature region. . Further, the positive characteristic in the high temperature region is set so that the resistance value changes as small as possible. Then, the temperature Tx at the point where the characteristics of the negative characteristic and the positive characteristic change is set to be substantially the center temperature of the temperature range used for level detection (for example, the range of 0 ° C. or lower to 100 ° C. or higher). There is.

Further, as described above, the positive temperature coefficient thermistor 28
By setting the characteristic of, the characteristic called the switching temperature Ts could be set to a much higher temperature than the conventional one. Here, the switching temperature Ts represents the temperature at which the resistance value becomes twice the resistance value at room temperature of 25 ° C., and in the positive temperature coefficient thermistor 28 in the present embodiment, the switching temperature Ts is 200 ° C.
It can be set within a value in the range of 300 ° C. (for example, 250 ° C.). This is the conventional one, but at most 50 ℃
This means that the value was set to be considerably larger than that within the range of 100 ° C.

That is, in the conventional positive temperature coefficient thermistor, in FIG. 6, the characteristic that the resistance value shifts from the low resistance region of R1 to R4 to the high resistance region of R4 to R5 is used, and the ratio of the resistance values is 100. In the positive temperature coefficient thermistor 28 in this embodiment, the temperature range from Ta (0 ° C. or lower) to Tb (100 ° C. or higher) set as the operating temperature range is used. The change width of the resistance value at that time is R in the figure with R1 as the minimum resistance
The characteristics of the region up to about 4 are used, and the variation range of the resistance value is small is the switching temperature Ts.
This is due to the high setting of.

Next, the operation of this embodiment will be described with reference to FIGS. 7 and 8. When the PTC thermistor 28 is energized from the vehicle-mounted battery 32 via the resistor 31 of the energization circuit 33, the PTC thermistor 28 is supplied with an energization current determined by the resistance value corresponding to the temperature at that time and the resistance value of the resistor 31. As a result, Joule heat proportional to the square of the current and the resistance value of the positive temperature coefficient thermistor 28 is generated.

At this time, since the positive temperature coefficient thermistor 28 of the detecting portion 27 is immersed in the engine oil 24 when the level of the liquid level of the engine oil 24 is equal to or higher than a predetermined level, the heat is generated by the positive temperature coefficient thermistor 28. Since the engine oil 24 in contact with the engine oil 24 is more absorbed, the temperature rise of the PTC thermistor 28 is reduced. Therefore, the resistance value of the positive temperature coefficient thermistor 28 according to the temperature is small, and the shared voltage is low. In the comparator 34, since the shared voltage applied to the inverting input terminal is smaller than the reference voltage applied from the voltage generating circuit 35, the "H" level signal is a detection signal indicating that the engine oil 24 is at a predetermined level or higher. Will be output as.

On the other hand, when the level of the liquid surface of the engine oil 24 is lower than the predetermined level, the PTC thermistor 28 is exposed to the air, and the heat generated by the PTC thermistor 28 is positive. Characteristic thermistor 28
The air in contact with the air will not be easily absorbed, and the temperature rise of the PTC thermistor 28 will increase. Therefore, the resistance value of the positive temperature coefficient thermistor 28 corresponding to the temperature increases, and the shared voltage also increases. In the comparator 34, since the shared voltage applied to the inverting input terminal is higher than the reference voltage applied from the voltage generating circuit 35, it is detected that the "L" level signal indicates that the engine oil 24 does not reach a predetermined level. It will be output as a signal.

The detection operation as described above can be performed in a wide temperature range of, for example, 0 ° C. or lower to 120 ° C. or higher. That is, the operating temperature range can be set in a wide range. This can be realized by setting the switching temperature Ts of the positive temperature coefficient thermistor 28 to a high temperature as described above, and the resistance value of the positive temperature coefficient thermistor 28 can be maintained even when the temperature of the engine oil 24 is high. This is because it is possible to keep the rise in the value low.

The above-described detection operation is performed by the positive temperature coefficient thermistor 28.
When expressed as a relationship of the shared voltage according to the temperature of, the result is as shown in FIG. In the figure, instead of the shared voltage of the positive temperature coefficient thermistor 28, the detected voltage Vd obtained by subtracting the shared voltage from the power supply voltage of the vehicle-mounted battery 32 is used to represent the voltage generation circuit 3.
The reference voltage of No. 5 is shown as the threshold voltage Vth correspondingly. As can be seen from this result, the decrease in the detection voltage Vd in the high temperature region is small, so that the difference ΔV in the detection voltage Vd depending on the presence or absence of the engine oil 24 can be obtained as a large value even in the high temperature region, and can be used. As described above, it is possible to set a wide temperature range (Ta to Tb) in a wide temperature range from 0 ° C. or lower to 120 ° C. or higher.

Further, the cover 29 provided on the detector 27 directly causes the positive temperature coefficient thermistor 28 even if the splash of the engine oil 24 splashing from the engine side hits the detector 27 when the engine is in a high rotation state. Therefore, even if the level of the liquid level of the engine oil 24 is below a predetermined level, it is possible to prevent erroneous detection that the droplets are above the predetermined level due to contact with the liquid. Will be done.

Then, while the above-described detection operation is being performed, the engine oil 24 in the oil pan 22 is
Even if the liquid level of the engine is drastically lowered, since the cover 29 is provided in the detection unit 27, the engine oil 24 remaining in the cover 29 is not immediately lost, and the hole 29a is formed.
It will start to decrease with time delay. Therefore, even if the liquid level of the engine oil 24 temporarily drops below a predetermined level due to vibration or inclination, if the liquid level of the engine oil 24 returns to the predetermined level or above in a short time, the engine oil 24 in the cover 29 will have the positive temperature coefficient thermistor. It does not fall below the position of 28 and the output of the detection signal does not cause so-called chattering. That is, since the engine oil 24 is configured to flow inside through the hole 29a of the cover 29, it has a function equivalent to the delay circuit in the conventional configuration.

FIG. 8 shows the state of the detection signal obtained corresponding to the engine speed when the level of the liquid surface is lowered by gradually reducing the amount of engine oil 24. Therefore, from this result, even when the engine speed becomes high and the splash of the engine oil 24 tends to be scattered to the detection unit 27, the liquid level of the engine oil 24 in the oil pan 22 reaches a predetermined level ( It was found that the level can be reliably detected in correspondence with the upper and lower sides of the "L" level position of the oil level gauge).

According to the present embodiment as described above, the detection unit 27
Since the cover 29 is provided on the positive temperature coefficient thermistor 28 to prevent splashing of the engine oil 24 due to the rotation of the engine from the engine side, the engine oil 24
If the amount of the engine oil 24 is insufficient below a predetermined level, the level of the engine oil 24 in the oil pan 22 can be reliably detected even if the engine oil 24 splashes from above due to engine rotation. This makes it possible to prevent erroneous detection.

Further, a cover 29 is provided on the detecting portion 27 to allow the engine oil 24 to flow into the inside through a hole 29a provided on the bottom surface of the cover 29, and a hole 29b provided on the side wall portion for the internal air. Since the structure is such that the engine oil 24 in contact with the positive temperature coefficient thermistor 28 can be changed with a time delay, even if the liquid level of the engine oil 24 changes temporarily, the engine oil 24 can be changed accordingly. The output does not change each time, and the function equivalent to that of the conventional delay circuit can be provided, so that it is not necessary to separately provide a delay circuit.

Further, according to the present embodiment, the characteristic of the positive characteristic thermistor 28 is changed from the negative characteristic region having the negative temperature coefficient of the resistance value to the positive characteristic region having the positive temperature coefficient as the temperature rises. And the temperature T at the area change point
Since x is set so as to be near the center temperature of the operating temperature range (Ta to Tb), the engine can be used in a wide operating temperature range while the PTC thermistor 28 and its detection circuit 38 are provided in a simple, compact and inexpensive structure. The level of oil 24 can be detected.

A wide operating temperature range can be realized as in this embodiment because the positive temperature coefficient thermistor 28 is used.
The use of the negative characteristic region also greatly contributes, and although the use of only the positive characteristic region is wider than the conventional detectable temperature range, the present inventors cannot cover the operating temperature range. Confirmed by experiments.

FIG. 9 shows a second embodiment of the present invention. The difference from the first embodiment is that a cover 39 is provided in place of the cover 29 of the detecting section 27. That is, the cover 39 is composed of a cylindrical case 39a and a lid 39b attached so as to close the bottom surface of the case 39a. The case 39a is attached with the positive temperature coefficient thermistor 28 of the arm 26. It is fitted and fixed so as to fit into the convex portion 26a of the portion. One terminal of the positive temperature coefficient thermistor 28 is supported by the central portion of the lid 39b and is also electrically connected.
Then, a hole 39 of a predetermined size is provided around the lid 39b.
c and 39c are opened, and the engine oil 24 can flow inside the cover 39. Further, an air vent hole 39d is formed downward in the side wall of the cover 39a. Therefore, the same operation and effect as those of the first embodiment can be obtained by the second embodiment as well.

FIG. 10 shows a third embodiment of the present invention. The difference from the first embodiment is that the cover 29 of the detector 27 is replaced with a plate 40 and a case 41 for avoiding oil. By the way. That is, the plate 40 for avoiding oil is formed in an umbrella shape that is expanded downward as shown in FIG. 3B, and the hole 40a formed in the center is provided with a convex portion of the arm 26. It is attached to the portion 26a in a fitted state. The case 41 is shown in FIG.
As shown in FIG. 5, the upper surface portion is formed in an open state, and the upper surface portion is attached so as to cover the positive temperature coefficient thermistor 28 of the arm 26.

The case 41 has a hole 41a formed at the center of the bottom surface to allow the engine oil 24 to flow therein, and holes 41b, 41b for air release formed on both side walls. Air can be passed outside. Therefore, also in this embodiment, it is possible to obtain the same operation and effect as those of the first embodiment.

In each of the above-described embodiments, the hole 29c, 39c or 41 through which the engine oil 24 circulates.
The relationship between the size of a and the size of the air vent holes 29d, 39d or 41b is not described in detail, but these sizes are not limited to the engine oil to be used, its temperature or the cover 29, 39, 41. A desired delay time can be generated by appropriately setting it according to the volume or the like.

[0043]

As described above, according to the oil level sensor of the present invention, the detection portion is provided with the cover so as to cover the upper portion of the positive temperature coefficient thermistor. In addition, for example, even if engine oil splashes generated by the rotation of the engine are scattered from above, they will not be directly attached, and in particular, the level of the engine oil level in the oil pan is below a predetermined level. Even in the state, it is possible to reliably prevent erroneous detection, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is a side view of the overall configuration showing a first embodiment of the present invention.

FIG. 2 is a vertical cross-sectional side view showing an arrangement state in an oil pan.

FIG. 3 is an external perspective view of a detection unit.

4A is a vertical side view of the detection unit, and FIG. 4B is a bottom view of the detection unit.

FIG. 5 is an electrical configuration diagram of a detection circuit.

FIG. 6 is a characteristic diagram of the resistance value with respect to temperature of the positive temperature coefficient thermistor.

FIG. 7 is a characteristic diagram of the detected voltage in the operating temperature range.

FIG. 8 is detection data corresponding to engine speed and engine oil amount.

FIG. 9 is a view corresponding to FIG. 4 showing a second embodiment of the present invention.

10A is a vertical side view of a detection unit showing a third embodiment of the present invention, FIG. 10B is an external perspective view of the splash prevention cover, and FIG. 10C is an external perspective view of the cover.

FIG. 11 is a view corresponding to FIG. 1 showing a conventional example.

FIG. 12 is a view corresponding to FIG.

[Explanation of symbols]

21 is an oil level sensor, 22 is an oil pan, 24 is engine oil, 25 is a mounting and fixing part, 26 is an arm, 2
7 is a detector, 28 is a positive temperature coefficient thermistor, 29 is a cover,
29a is a hole, 29b is an air vent hole, 31 is an energizing resistor, 32 is an on-vehicle battery, 33 is an energizing circuit, 34 is a comparator (comparing means), 35 is a voltage generating circuit, 36 and 37 are resistors, 38 Is a detection circuit, 39 is a cover, 40 is a plate for avoiding oil, and 41 is a case.

Claims (1)

[Claims] 1. An oil level sensor for detecting the level of engine oil in an oil pan, wherein the detection unit is arranged so as to be immersed when the engine oil in the oil pan is above a predetermined level, and this detection unit. A positive temperature coefficient thermistor which is provided to the part and generates Joule heat according to the energized current when a current is applied, a cover which is provided in the detection part so as to cover an upper part of the positive temperature coefficient thermistor, and the positive temperature coefficient. An oil level sensor, comprising: a detection unit that detects that the engine oil is present at a predetermined level or higher based on the voltage shared by the thermistor.