JPH02242128A - Water temperature detecting display device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a water temperature detection and display device for detecting and displaying the temperature of, for example, automobile engine cooling water.

BACKGROUND OF THE INVENTION Conventionally, this type of water temperature detection and display device has had a configuration as shown in FIG. In FIG. 6, the meter 1 is mainly of a bimetal type or a crossed coil type. A water temperature detection section 2 constituted by a negative characteristic thermistor is installed in the engine cooling water section, and converts a resistance change of the water temperature detection section 2 according to the water temperature into a current change. A meter 1 is connected in series to this water temperature detection section 2, and the needle of the meter 1 displays the temperature. 7th
The figure shows the resistance temperature curve of the water temperature detection section 2, and FIG. 8 shows the current temperature curve.

FIG. 9 shows a configuration wiring diagram when the meter 1 in FIG. 6 is a bimetallic meter. In FIG. 9, the water temperature detection section 2 is attached to the engine cooling holder wall 3, and the resistance wire 5 connected to the water temperature detection section 2 is wound around the circumferential surface of the bimetal 6 and then connected to the power source 4. . A temperature display pointer 7 engaged with the tip of the bimetal 6 swings in response to the displacement of the bimetal 6, and displays the temperature of the engine cooling water.

In FIGS. 7 and 8, T1 is the temperature at which the engine cooling water begins to warm, which is approximately 50° C., and corresponds to "low" on the meter display in FIG. 9.

T4 is the temperature at which the engine is overheated, which is approximately 120°C.
This corresponds to "high" on the meter display section in FIG.

If the pointer 7 goes higher than this, it is dangerous and it is necessary to stop the car and inspect it. Temperatures T2 and T3 are T1.
T4 is approximately 80°C and 100°C, respectively, indicating the engine's favorable temperature range, and the "
Located between the “low” and “high” indications.

Problems to be Solved by the Invention However, in such a conventional configuration, even when the water temperature is appropriate, due to tolerances of the engine and cooling system, as well as the detector and indicator meter, the cooling water temperature does not reach the normal mIfT2~T.
! However, there are cases where the indicator 7 rises to an overheated state of temperature T4 or close to temperature T4, which poses a problem of giving an unnecessary sense of anxiety to the driver of the vehicle.

To solve this problem, there is a water temperature detection and display circuit as shown in FIG. In FIG. 10, a negative characteristic thermistor 8 and a series circuit of a negative characteristic thermistor 9 and a positive characteristic thermistor 10 are connected in parallel, and this parallel circuit is connected in series to a meter 11.

FIG. 11 is a diagram showing the resistance temperature characteristics of FIG. 10.

In FIG. 11, curve A is the characteristic of the negative characteristic thermistor 8, curve 1laB is the composite characteristic of the series circuit of the negative characteristic thermistor 9 and positive characteristic thermistor 10, and curve C is the overall characteristic of the thermistor of the entire parallel circuit. In this case, the temperature T2~T
3, the resistance temperature change is small, and T2 to T3
Between T3 and T3, the indication is almost constant regardless of the temperature, which has the effect of absorbing the tolerance of the above problem, but when the temperature exceeds T3, the same problem as before remains. Also, the temperature T
Even if the resistance value fiiR1 at temperature T4 is combined, the resistance value at temperature T4 is R6, which is considerably higher than the resistance value R4 in FIG. 7, which is not preferable because it is not compatible with meter 1 in FIG. Further, in order to match the resistance value R4 at the temperature T4, the 8 constants of the negative characteristic thermistor 9 must be set to 7000° or more, which poses a problem that this cannot be used as a thermistor material.

The present invention solves the above-mentioned conventional problems, and is compatible with conventional meters.Furthermore, due to various tolerances, the present invention can indicate that the engine is overheating even though the engine coolant temperature is normal. It is an object of the present invention to provide a water temperature detection and display circuit that can prevent such problems.

Means for Solving the Problems In order to solve the above problems, the water temperature detection and display device of the present invention has a negative temperature thermistor temperature detection section and a temperature display meter connected in series, and a positive temperature display meter connected in parallel with the temperature display meter. A characteristic thermistor temperature detection section is connected.

Furthermore, the water temperature detection and display device of the present invention, as described above,
Negative characteristic thermistor connected in series to a temperature display meter Instead of the temperature detecting section, a temperature detecting section or negative characteristic thermistor in which a negative characteristic thermistor is connected in parallel to a series circuit in which a negative characteristic thermistor and a positive characteristic thermistor are connected in series. A temperature sensing section, which has a negative characteristic thermistor connected in series to a parallel circuit in which a negative characteristic thermistor and a positive characteristic thermistor are connected in parallel, is connected in series to a temperature display meter.

Effect: With the above configuration, the temperature T1. The current 11■4 at T4 is set to the same value as before, and the rate of change of the current is made gradual as the temperature rises from T1 to T2 and from T2 to T3, and the rate of change is made rapid from T3 to T4. This allows compatibility with conventional meters.

For example, if you use a positive temperature coefficient thermistor with a sudden change in resistance temperature around ■3 and set the current [1 at T1 to the conventional value, the current up to T2 and Tt will be shunted to the positive coefficient thermistor, so The current change will be gradual. Furthermore, since the resistance value of the positive temperature coefficient thermistor increases rapidly when the value is 11 or more, the shunt current caused by the positive coefficient thermistor decreases, and the current between T3 and T4 increases rapidly due to the temperature rise. By providing such a current change, the current values at the starting temperature T1 and the final temperature T4 can be made the same as in the conventional meter, and compatibility with the conventional meter is made possible.

Furthermore, due to the above current change, the fluctuation of the temperature display meter becomes smaller in the normal temperature range, and the sensitivity of the meter becomes better in the range from high temperatures to abnormal overheating. This prevents false indications that the engine is overheating even though the engine coolant temperature is normal.

Example Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a circuit diagram of a water temperature detection and display circuit showing one embodiment of the present invention. In Figure 1, bimetallic meter 2
1 and the negative characteristic thermistor 22 are connected in series, and the meter 2
A positive characteristic thermistor 23 is connected in parallel with 1. The negative characteristic and positive characteristic thermistors 22 and 23 are housed in the case 24 and installed to detect the temperature of the engine coolant. Here, the negative characteristic thermistor 22 has a diameter of 5u1, a thickness of 1.0, a room temperature resistance of 280Ω, and a B constant of 41.
As the positive characteristic thermistor 23, a one having the same dimensions as the negative characteristic thermistor 22, a room temperature resistance value of 100 Ω, and a switching temperature of 90° C. was used, and a test product as shown in FIG. 2 was prepared. The case 24 is made of brass with an inner diameter of 8 mm and a thickness of 0.5 mm.The lead wires 25 and 26 are m wires with a diameter of 0.511 #I, and the negative characteristics built into the case 24 are used. and positive temperature coefficient thermistors 22 and 23, respectively, by soldering.

Figure 3 shows a power supply of 7V and a meter resistance of 55Ω.
It is a resistance-temperature characteristic diagram measured using the following. Third
In the figure, the curved line is for the conventional example shown in FIG. 4, which is for only a series circuit of a negative characteristic thermistor and a meter, and the curved line E is for this embodiment. Here, the temperature is 50℃, 1
The current at 20°C is the same as the conventional one, but the increase in current from temperature 50°C to 90°C and 100°C is
It is gentler than the conventional one, and conversely, the temperature is 100%
The current increases extremely rapidly between 120°C and 120°C.

Therefore, the fluctuation of the meter 21 is small between the temperature of 50°C and 100°C, and the sensitivity of the meter 21 is good between the temperature of 100°C and 120°C. It is possible to prevent false indications that the cooling water is overheating even though the temperature is normal. Furthermore, at a temperature of 50°C and a temperature of 120°C, the current flowing is the same as the conventional song #! It can be seen that the case D and the case of this embodiment are the same, making it possible to provide compatibility with conventional meters.

Furthermore, in the above configuration, a newly used positive polarity thermistor can be housed together with the case of the conventionally used detector, resulting in an extremely simple configuration and low cost.

FIGS. 4 and 5 are circuit diagrams of water temperature detection and display devices showing other embodiments, respectively. In FIG. 4, a negative characteristic thermistor 2 is used instead of the negative characteristic thermistor 22 in FIG.
7 and a positive characteristic thermistor 28 are connected in series, and a negative characteristic thermistor 29 is connected in parallel to the temperature detection section 30.
is used, and in FIG. 5, a negative characteristic thermistor 31
A temperature detection unit 34 is used, which has a negative characteristic thermistor 33 connected in series to a parallel circuit in which a positive characteristic thermistor 32 and a positive characteristic thermistor 32 are connected in parallel. It can be changed in various ways.

Further, by incorporating all the negative characteristic thermistor and positive characteristic thermistors of the negative characteristic thermistor temperature detecting section and the positive characteristic thermistor temperature detecting section into the same case, it can be easily and inexpensively obtained.

Effects of the Invention As described above, according to the present invention, a positive temperature coefficient thermistor whose resistance value changes according to temperature and has a sudden change in resistance is used in the temperature detection section, and this positive coefficient thermistor temperature detection section is By connecting it in parallel with the display meter section, the fluctuation of the meter is kept small in the normal temperature range, and the sensitivity of the temperature display meter is improved from slightly higher than normal temperature to abnormal overheating. Since the deflection can be increased, it is possible to prevent erroneous indications that the engine cooling water is in an abnormally overheated state even though the engine cooling water is at a normal temperature due to tolerances of the detector, temperature detection meter, etc., can be prevented. Furthermore, it is possible to provide compatibility with conventional temperature display meters.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a water temperature detection and display device showing an embodiment of the present invention, Fig. 2 is a configuration diagram of a temperature detection section in the water temperature detection and display device, and Fig. 3 is a current temperature characteristic of the water temperature detection and display device. 4 and 5 are circuit diagrams of a water temperature detection and display device showing other embodiments of the present invention, FIG. 6 is a circuit diagram of a conventional water temperature detection and display device, and FIG. 7 is a circuit diagram of a conventional water temperature detection and display device. A resistance temperature characteristic diagram of the display device, FIG. 8 is a current temperature characteristic diagram of a conventional water temperature detection and display device, FIG. 9 is a configuration diagram of a conventional water temperature detection and display device, and FIG. 10 is a water temperature diagram showing another conventional example. A circuit diagram of the detection display device, and FIG. 11 is a resistance temperature characteristic diagram of the same water temperature detection and display device. 21...meter, 22.27.29.31.33...
・Negative characteristic thermistor, 23.29.32...Positive characteristic thermistor. Agent Yoshihiro Morimoto S+
N of N N 1ψ Fig. 4 Fig. S Fig. 4 Fig. 8 Fig. 7 Fig. 7 Fig. 1 O Fig. 11

Claims (2)

[Claims] 1. A water temperature detection and display device comprising: a negative characteristic thermistor temperature detecting section and a temperature display meter connected in series; and a positive characteristic thermistor temperature detecting section connected in parallel with the temperature display meter. 2. Negative characteristic thermistor connected in series to a temperature display meter Instead of the temperature detecting section, a temperature detecting section or negative characteristic thermistor in which a negative characteristic thermistor is connected in parallel to a series circuit in which a negative characteristic thermistor and a positive characteristic thermistor are connected in series. 2. The water temperature detection and display device according to claim 1, further comprising: a temperature sensing section having a negative characteristic thermistor connected in series to a parallel circuit comprising a positive characteristic thermistor and a positive characteristic thermistor connected in parallel and connected in series to the temperature display meter.