JPH05321631A - Oil shortage warning device - Google Patents

Abstract

PURPOSE:To stabilize the detection of an oil level by eliminating a specific constant voltage circuit. CONSTITUTION:A circuit comprising a thermistor 1, a temperature sensing switch 2 and a warning lamp 3 which are connected in series, is connected at one end to a plus terminal of a battery and at the other end to the ground. The thermistor 1 is arranged retractable and extendable from and into oil, and varies its resistance in accordance with an atmospheric temperature. The temperature sensing switch 2 is turned on for energization when the atmospheric temperature exceeds a predetermined value. The warning lamp 3 is turned on by a current fed through the thermistor 1 and the temperature sensing switch 2 when the resistance of the thermistor 1 becomes lower than a predetermined value so as to warn shortage of oil. Accordingly, the energization of the thermistor 1 is not made in a temperature range where the temperature sensing switch 2 is not turned-on. Accordingly, a battery voltage and variation in the battery voltage does not affect the turn-on of the warning lamp 3 in this temperature range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oil shortage warning device which is used in an internal combustion engine or the like and detects an oil shortage of engine oil or the like and performs a warning operation.

[0002]

2. Description of the Related Art Conventionally, an oil level detecting device disclosed in, for example, Japanese Patent Application Laid-Open No. 56-158915 is known as this type of technique.

In this oil level detecting device, a thermistor which is energized by a power source is housed in an oil tank. This thermistor generates heat when energized and changes its resistance value. However, when it is immersed in oil, the amount of heat radiation is large, so the temperature becomes relatively low and the resistance value becomes high. On the other hand, when the thermistor is exposed to the outside of oil (in the air), the amount of heat radiation is small, so the temperature becomes relatively high and the resistance value becomes low. Therefore, by comparing the change in the resistance value of the thermistor with a predetermined resistance value, it is determined whether the thermistor is buried in oil or exposed in the air, that is, whether the oil level is sufficient. Is detected.

When an oil detecting device using such a thermistor is attached to an oil pan of an internal combustion engine of an automobile or the like and used to detect the level of the engine oil level, a battery is used as a power source. The voltage of the on-vehicle battery varies greatly depending on the usage state of the vehicle. Further, the temperature of the engine oil itself also varies widely depending on the usage condition of the automobile. Therefore, the change in the battery voltage or the change in the oil temperature may cause a malfunction in the oil level detection, which may result in an incorrect oil level detection.

Therefore, the above oil level detecting device is provided with a constant voltage circuit, and the thermistor is energized from the battery through the constant voltage circuit to stabilize the level detecting operation regarding the oil level. Was there.

[0006]

Therefore, in the above-mentioned prior art, a constant voltage circuit must be additionally provided in order to stabilize the level detection operation relating to the oil level, and the circuit of the entire apparatus is correspondingly provided. The structure was complicated, and the cost was increased.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is an oil shortage warning capable of stabilizing the oil level detection operation by omitting a special constant voltage circuit. To provide a device.

[0008]

In order to achieve the above object, in the present invention, there are provided a thermistor which is arranged so as to be able to project and retract with respect to oil, and which changes a resistance value in response to an ambient temperature, and the thermistor. When the resistance value of the thermistor, which is connected in series and connected in series with the thermistor and the temperature-sensitive switch and the thermistor and the temperature-sensitive switch that are turned on and can be energized when the ambient temperature is above the specified value, falls below the specified value. And warning means for warning the oil shortage by operating with the current supplied through the thermistor and the temperature sensitive switch.

[0009]

According to the above construction, the sensing operation is performed only when the ambient temperature exceeds a predetermined value in a state where a series circuit including a thermistor, a temperature sensitive switch and a warning means connected in series to each other is connected to the power source. The temperature switch is turned on and the thermistor is energized. At this time, when the thermistor is submerged in oil, the amount of heat released by the thermistor is large, so that the thermistor itself has a relatively low temperature and a high resistance value. On the other hand, when the thermistor is exposed to the outside of oil (in the air), the amount of heat released by the thermistor is small, so that the thermistor itself has a relatively high temperature and a low resistance value. Then, when the resistance value of the thermistor becomes equal to or less than a predetermined value, a current is supplied to the warning means through the thermistor and the temperature sensitive switch, and the warning means operates to give a warning of oil shortage.

Therefore, the thermistor is no longer energized for the range of the ambient temperature at which the temperature sensitive switch is not turned on, and the change of the power supply voltage or the change of the oil temperature causes the operation of the warning means for the range of the temperature. It has no effect.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the oil shortage warning device of the present invention applied to an oil pan of an automobile will be described below with reference to FIGS.
This will be described in detail with reference to FIG.

FIG. 1 is an electric circuit diagram showing the construction of an oil shortage warning device in this embodiment. This oil shortage warning device has a series circuit configuration in which an NTC type thermistor 1, a temperature sensitive switch 2, and a warning lamp 3 constituting a warning means are connected in series. One end of the series circuit is connected to the plus terminal (B +) of the battery, and the other end is grounded (GND).

The thermistor 1 is arranged so as to be able to project and retract with respect to oil, as will be described later, and is adapted to change its own resistance value in response to the ambient temperature. As will be described later, the temperature sensitive switch 2 is "ON" and can be energized when the ambient atmospheric temperature is equal to or higher than a predetermined value.

Here, the characteristics of the thermistor 1 will be described in detail. The graph of FIG. 3 shows the relationship between the power supply voltage and the energizing current experimentally confirmed by a test circuit in which the thermistor 1 and a predetermined lamp are connected in series,
It shows a case where the thermistor 1 is located in oil and a case where it is located in air. The graph of FIG. 4 also shows the relationship between the test circuit, the voltage V, VT, and VB between the terminals of the thermistor 1 and the lamp, which is experimentally confirmed by the test circuit of the thermistor 1 and a predetermined lamp. ing.

In the above test circuit, by applying a power supply voltage to heat the thermistor 1, the heat generated by the thermistor 1 itself and the amount of heat lost from the thermistor 1 due to the heat dissipation are balanced, and the temperature of the thermistor 1 itself is constant. Trying to become. As can be seen from the graph of FIG. 3, the required power supply voltage gradually increases as the energization current increases, but at a certain energization current value, the necessary power supply voltage gradually decreases after reaching the maximum value. To fall. When the energizing current further increases, the power supply voltage required at a certain energizing current value takes a minimum value and then gradually increases. This is the thermistor 1 as is clear from the graph of FIG.
This is due to the fact that the resistance value of the lamp abruptly decreases at a certain current value due to the thermal runaway effect of the thermistor 1 and that the resistance value of the lamp increases in proportion to the square of the current value. is doing. Further, when the power supply voltage is kept constant, the amount of heat lost from the thermistor 1 is large in oil, so the temperature of the thermistor 1 itself becomes relatively low. Therefore, the resistance value of the thermistor 1 becomes large, and the energizing current value Ioil at this time becomes less than the extinguishing current Ioff of the lamp (“50 mA” in FIGS. 5 and 7 described later), and the lamp cannot obtain a sufficient current. Will turn off. On the other hand, in the air, since the amount of heat lost from the thermistor 1 is small, the temperature of the thermistor 1 itself becomes relatively high. Therefore, the resistance value of the thermistor 1 becomes small, and the energizing current Iair at this time becomes equal to or higher than the lighting current Ion of the lamp (“115 mA” in FIGS. 5 and 7), and the lamp should be lit with sufficient current. become.

The graph of FIG. 5 shows the relationship between the power supply voltage of the thermistor 1 and the energizing current with respect to the ambient temperature, which has been experimentally confirmed by a test circuit in which the thermistor 1 and a predetermined lamp are connected in series. Shows the case where is located in the oil and the case where it is located in the air.

As can be seen from this graph, a large amount of heat is lost from the thermistor 1 in oil,
Even if the ambient temperature rises, the temperature of the thermistor 1 itself is relatively low, so the resistance value of the thermistor 1 increases and the energizing current decreases. This will turn off the lamp. On the other hand, since the amount of heat lost from the thermistor 1 is small in the air, the thermistor 1 starts thermal runaway when the ambient temperature rises above a predetermined value, and the resistance value of the thermistor 1 decreases and the energizing current increases. This will turn on the lamp. In the air, the power supply voltage increases even in the range of relatively low atmospheric temperature, so that the thermistor 1 starts thermal runaway. Therefore, the lamp will be lit regardless of the magnitude of the power supply voltage.

The graph of FIG. 6 shows the switching characteristics with respect to the ambient temperature of the temperature sensitive switch 2 which has been experimentally confirmed. As can be seen from this graph, the temperature-sensitive switch 2 is "on" at an ambient temperature of "60 ° C" or higher, and is "off" at an ambient temperature of lower than "60 ° C".

In this embodiment, the thermistor 1 and the temperature sensitive switch 2 having the above-mentioned characteristics constitute a sensor circuit 5 incorporated in an oil level sensor 4 described later.

On the other hand, the warning lamp 3 is arranged in the combination meter in the driver's seat. The warning lamp 3 is provided with the thermistor 1 and the temperature sensitive switch 2 when the resistance value of the thermistor 1 becomes equal to or lower than a predetermined value.
Lights up by the electric current supplied through. This alerts the driver of the lack of oil.

FIG. 2 is a sectional view showing the structure of the oil level sensor 4. The oil level sensor 4 includes a terminal housing 6 made of a conductive metal, and a connector 7 made of an insulating material is assembled on the upper side of the housing 6. A terminal 8 for external output is fixed to the connector 7. The terminal 8 is connected to a battery (not shown) via the warning lamp 3 described above. On the other hand, on the lower side of the terminal housing 6, a base end portion of a protective pipe 9 made of a conductive metal is assembled. A pipe-shaped protection cover 10 is attached to the tip of the protection pipe 9. An insulator 11 is provided inside the joint between the protective pipe 9 and the protective cover 10. And the protection pipe 9
The temperature-sensitive switch 2 is fixed to the inside of the tip of the via an insulator 11. Further, the thermistor 1 is fixed inside the protective cover 10 via an insulator 11. The terminal 8 and one terminal of the temperature sensitive switch 2 are connected by a lead wire 12. The other terminal of the temperature sensitive switch 2 and one terminal of the thermistor 1 are connected to each other. Further, the other terminal of the thermistor 1 is connected to the protective cover 10 and is grounded.

The oil level sensor 4 thus constructed is attached to the oil pan 13 or the engine block (not shown) at the terminal housing 6, and the protective pipe 9 and the protective cover 10 thereof are immersed in the engine oil. It is embedded. In this state, if the engine oil amount is sufficient, the thermistor 1 will be submerged in the engine oil. On the other hand, when the engine oil amount decreases below the specified level, the thermistor 1 is exposed in the air above the oil level OS. ..

Next, the operation of the oil shortage warning device constructed as described above will be described. The graph of FIG. 7 shows the power supply voltage (battery voltage) of the thermistor 1 experimentally confirmed by using the oil shortage warning device of this embodiment, and the relationship between the energizing current and the ambient temperature. The case is shown and the case is shown in the air.

When the engine oil amount is sufficient and the oil level is high, the thermistor 1 is buried in the engine oil, so that the operation of the thermistor 1 exhibits the characteristics of oil in the graph of FIG. That is, since the temperature sensitive switch 2 is turned on and energized only when the ambient temperature is “60 ° C.” or higher, the thermistor 1 outputs “6”.
It is energized only at an ambient temperature of "0 ° C" or higher. here,
Since the thermistor 1 is buried in oil, the amount of heat released by the thermistor 1 is large, so that the resistance value of the thermistor 1 becomes relatively high. Therefore, the ambient temperature is "60 ° C"
Therefore, even if the battery voltage slightly increases or the battery voltage fluctuates to some extent, sufficient current is not supplied to the warning lamp 3 from the battery through the thermistor 1 and the temperature sensitive switch 2. Therefore, the warning lamp 3 remains off.

On the other hand, when the engine oil amount is lower than the specified level and the oil level is low, that is, when the oil is insufficient, the thermistor 1 is exposed from the engine oil to the air. 7 shows the characteristics in air in the graph. That is, the temperature sensitive switch 2 is turned on and is energized only when the ambient temperature is “60 ° C.” or higher, so that the thermistor 1 is energized only at the ambient temperature of “60 ° C.” or higher. Here, since the thermistor 1 is exposed in the air, the amount of heat released by the thermistor 1 is small, so the resistance value of the thermistor 1 becomes relatively low. Then, when the resistance value of the thermistor 1 becomes equal to or less than a predetermined value, a sufficient current is supplied to the warning lamp 3 from the battery through the thermistor 1 and the temperature sensitive switch 2. Therefore, the warning lamp 3 is turned on, and the driver is warned that the oil is insufficient.

Therefore, in the atmosphere temperature range of less than "60 ° C" where the temperature sensitive switch 2 does not turn "ON", the thermistor 1 is not energized, and only in the atmosphere temperature range of "60 ° C" or more. Energization to 1 is performed.
Therefore, in this embodiment, even if the voltage of the battery greatly changes or the temperature of the engine oil changes depending on the usage state of the vehicle, the fact that the temperature of the thermistor 1 falls within the atmospheric temperature range of less than "60 ° C." It does not affect the operation, and eventually the lighting of the warning lamp 3. And
Thermistor 1 only in the ambient temperature range of "60 ° C" or higher
Will operate and the warning lamp 3 will be turned on reliably.

Therefore, in this embodiment, the oil shortage detection such that the warning lamp 3 is erroneously turned on even if there is a change in the battery voltage or a change in the engine oil temperature in the range of the ambient temperature lower than "60 ° C". The malfunction of does not occur. As a result, the level detection operation of the oil level OS can be stabilized. Moreover, in this embodiment, no special constant voltage circuit is provided in order to stabilize the level detecting operation as described above. That is, according to the oil shortage warning device of this embodiment, the operation of detecting the level of the oil level OS can be stabilized while omitting a special constant voltage circuit, and a highly reliable operation can be realized. You can Further, the circuit configuration of the entire device can be simplified by the amount that a special constant voltage circuit is not provided, and the cost increase of the device can be suppressed.

Furthermore, in this embodiment, the thermistor 1 does not operate and the warning lamp 3 does not light up in a state where the oil viscosity is high because of the low ambient temperature of less than "60 ° C.". Therefore, according to the oil shortage warning device, it is possible to prevent the oil shortage from being erroneously warned due to the decrease in the oil level OS when the oil is drastically rising to the engine at a low temperature. Therefore, also from this fact, highly reliable operation of the oil shortage warning device can be realized.

In addition, in this embodiment, it takes a certain amount of time from when the thermistor 1 is energized until its resistance value falls below a predetermined value due to thermal runaway. Therefore, the lighting of the warning lamp 3 is substantially delayed until the resistance value of the thermistor 1 becomes a predetermined value or less after the temperature sensitive switch 2 is turned on.

Therefore, in this embodiment, when the engine oil amount is sufficient, even if the thermistor 1 is exposed to the air due to the fluctuation / behavior of the oil level OS, the warning lamp 3 will be activated from the time of exposure. There is some delay before it starts to light. As a result, it is possible to avoid erroneous detection of oil shortage due to fluctuations and behavior of the oil level OS. In other words, according to the oil shortage warning device of this embodiment, it is possible to prevent erroneous detection due to the fluctuation / behavior of the oil level OS without providing a special delay circuit, and perform a highly reliable operation. Can be realized. In addition, the circuit configuration of the entire device can be simplified by the amount that no special delay circuit is provided, and the cost increase of the device can be suppressed.

In addition, in this embodiment, the oil shortage is determined by the action of the electric circuit as described above, and the warning lamp 3 is turned on / off.
Therefore, in this embodiment, it is not necessary to provide a special ECU circuit for determining the oil shortage. And that ECU
The circuit configuration can be further simplified by the number of circuits, which contributes to cost reduction of the device. Also, ECU
Since the circuit can be omitted, the mountability on the vehicle can be improved accordingly.

The present invention is not limited to the above-described embodiment, but can be implemented as follows with a part of the configuration appropriately changed without departing from the spirit of the invention. (1) In the above embodiment, the electric circuit is composed of a series circuit of the thermistor 1, the temperature sensitive switch 2 and the warning lamp 3. However, for the adjustment (tuning) of the current value, for example, as shown in FIG. The adjusting resistor 14 may be added and connected in series in the circuit, or, as shown in FIG. 9, the adjusting resistor 14 may be added and connected in parallel to the thermistor 1. In this case, it is naturally impossible to connect the adjusting resistor 14 to the temperature sensitive switch 2 in parallel.

(2) In the above-mentioned embodiment, the oil shortage warning device is applied to the oil pan 13 of the automobile, and is embodied.
It can also be embodied by being applied to other oil tanks such as a gasoline tank. Further, in that case, the shape of the oil level sensor may be appropriately changed depending on the tank.

(3) In the above embodiment, the oil level sensor 4 having the sensor circuit 5 and the warning lamp 3 are separated from each other, but the oil level sensor having the sensor circuit and the warning lamp are integrally provided. You can also

(4) In the above embodiment, the ambient temperature at which the temperature sensitive switch 2 is turned "on" is set to "60 ° C".
The ambient temperature can be set to a temperature other than “60 ° C.”.

(5) In the above embodiment, the lighting current Ion of the warning lamp 3 is set to "115 mA" in FIG.
Although the turn-off current Ioff is set to "50 mA", it may be set to another current value as appropriate according to the specifications of the warning lamp 3, the thermistor 1 and the power supply.

[0037]

As described above in detail, according to the present invention, a thermistor which is arranged so as to be capable of appearing in and retracting from oil and which changes its resistance value in response to the ambient temperature, and when the ambient temperature is above a predetermined value. When the resistance value of the thermistor falls below a specified value, the temperature sensitive switch that is turned on and can be energized is connected in series with the warning means that operates by the current supplied through the thermistor and the temperature sensitive switch. Therefore, the thermistor will not be energized for the ambient temperature range where the temperature sensitive switch does not turn on.
The change of the power supply voltage and the change of the oil temperature do not affect the operation of the warning means by the temperature range, and the operation of detecting the level of the oil level is stabilized by omitting the special constant voltage circuit. It has the excellent effect of being able to

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing a configuration of an oil shortage warning device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the structure of an oil level sensor in one embodiment.

FIG. 3 is a graph showing the relationship between the power supply voltage and the energizing current experimentally confirmed by a test circuit in which a thermistor and a lamp are connected in series in one embodiment, showing the case where the thermistor is located in oil and the air. 6 is a graph showing a case where the position is located at.

FIG. 4 is a graph showing the relation between the voltage between the terminals of the test circuit, the thermistor and the lamp with respect to the applied current, which was experimentally confirmed by the test circuit of the thermistor and the lamp in one embodiment.

FIG. 5 shows the relationship between the power supply voltage of the thermistor experimentally confirmed by a test circuit in which a thermistor and a lamp are connected in series in one embodiment, and the relationship between the energizing current and the ambient temperature. The thermistor is located in oil. It is a graph which shows the case where it does, and the case where it is located in the air.

FIG. 6 is a graph showing switching characteristics with respect to ambient temperature of the temperature-sensitive switch experimentally confirmed in one example.

FIG. 7 is a thermistor battery voltage experimentally confirmed using an oil shortage warning device in one embodiment;
6 is a graph showing a relationship between an energization current and an ambient temperature, showing a case where the thermistor is located in oil and a case where the thermistor is located in air.

FIG. 8 is an electric circuit diagram showing a configuration of an oil shortage warning device in another embodiment embodying the present invention, in which an adjusting resistor is added and connected in series.

FIG. 9 is an electric circuit diagram showing a configuration of an oil shortage warning device according to another embodiment of the present invention, in which an adjustment resistor is added and the devices are connected in parallel.

[Explanation of symbols]

1 ... Thermistor, 2 ... Temperature switch, 3 ... Warning lamp as warning means.

Claims (1)

[Claims] 1. A thermistor, which is arranged so that it can appear and disappear with respect to oil, and which changes its resistance value in response to an ambient temperature, and is connected in series to the thermistor, and is turned on when the ambient temperature is equal to or higher than a predetermined value. A temperature switch that can be energized, is connected in series to the thermistor and the temperature switch, and when the resistance value of the thermistor becomes a predetermined value or less, by the current supplied through the thermistor and the temperature switch. An oil shortage warning device comprising: warning means for operating to warn of oil shortage.