JPH0378571B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a temperature detection unit, and particularly to a unit that detects the temperature of engine cooling water in order to optimize control of the amount of gasoline when starting an automobile engine. It is.

[Prior Art] When an automobile gasoline engine is started in the winter, the engine is cold, so the gasoline is difficult to vaporize, and therefore the explosive power of the air-fuel mixture is weak. For this reason, it is common practice to pull the engine switch to adjust the amount of air and increase the mixture ratio of gasoline to air to increase the explosive power of the mixture. When the time comes, there will be no need for that. The best way to detect engine temperature is to detect the temperature of the engine coolant.
When the water temperature rises above a certain temperature, the yoke switch is returned to its original position and the amount of air from the air cleaner is returned to its normal state. The operation timing for returning the check switch is indicated by a lamp lit by the water temperature detection unit.

In modern cars, this operation is automated. However, in inexpensive cars, a switch is provided as before to carry out this series of operations. Thermostats have been used to detect water temperature using conventional water temperature detection units.

[Problems to be Solved by the Invention] However, this thermostat has large variations in operating temperature. For this reason, in some cars, it takes a short time for the indicator lamp to turn on after starting, and if the engine is not warmed up, the engine may stall if the engine switch is returned to its original position too early.
On the other hand, the indicator lamp does not light up even though the engine temperature is too high, so if you return the check switch too late, it will take a long time to inhale excess gasoline, which will shorten the engine's durability. Ta. This is because thermostats have a wide operating temperature range due to variations in their manufacturing quality, and their thermal response is slow.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to obtain a temperature detection unit that is accurate and has quick thermal response.

[Means for Solving the Problems] A temperature detection unit according to the present invention includes a thick film substrate with good thermal conductivity housed in a metal case having a temperature detection surface on its outer surface, and a thick film substrate with good thermal conductivity. A thermistor is provided to detect the temperature of the metal case, and in order to transfer the temperature of the temperature detection surface of the metal case to the thick film substrate, the end surface perpendicular to the length direction of this substrate is pressed against the inner surface corresponding to the temperature detection surface of the metal case using a pressing means. It is designed so that it can be pressed.

[Function] The end face perpendicular to the longitudinal direction of the thick film substrate, which has good thermal conductivity, is pressed against the inner surface of the metal case that corresponds to the temperature detection surface, so the temperature of the temperature detection surface of the metal case is accurately measured against the thick film substrate. The temperature of this board is accurately detected by a thermistor.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of a water temperature detection unit and its peripheral parts when the water temperature detection unit is applied to an automobile, which is an embodiment of the present invention. First, these configurations will be explained. In the figure, 1 is a water temperature detection unit, and this unit employs an electronic circuit to improve the accuracy of operating temperature. The cathode of the battery 2 is grounded, and its anode is connected to the terminal B of the water temperature detection unit 1 via the indicator lamp 3 and the switch 4, and to the terminal A via the thermometer 5.
The indicator lamp 3 lights up when the temperature of the engine coolant reaches a predetermined temperature. A thermometer 5 indicates the temperature of engine cooling water, and is mounted on a panel board of the automobile. Engine overheating is confirmed by the thermometer 5. To explain the water temperature detection unit 1 in more detail, a terminal A is connected to a grounded terminal C via a thermistor 6. Terminal B is connected to the emitter of a pnp transistor 15 via a resistor 11 and also to the emitter of a pnp transistor 16. The collector of the pnp transistor 15 is connected to the terminal C via the resistor 14, and the collector of the pnp transistor 16 is connected to the terminal C. Also, terminal B has a resistance of 1
0 is connected to terminal C via thermistor 7, and the connection point between resistor 10 and thermistor 7 is connected to the base of pnp transistor 15. Furthermore, terminal B is connected to terminal C via resistors 12 and 13, and the connection point between resistors 12 and 13 is the pnp transistor 1.
Connected to the base of 6. Further, the terminal B is connected to the terminal C via the thyristor 8, and the connection point between the collector of the pnp transistor 15 and the resistor 14 is connected to the gate of the thyristor 8. Further, terminal B is connected to terminal C via capacitor 9. The thermistors 6 and 7 are of the NTC type whose resistance value decreases in proportion to the rise in temperature, and the temperature of the engine coolant is detected by the change in resistance value.
The current flowing through the thermometer 5 changes according to a change in the resistance value of the thermistor 6, and a change in the temperature of the engine cooling water appears as a change in the pointer of the thermometer 5. Resistor 11 limits the current flowing through pnp transistors 15 and 16. Resistors 10, 12, 13 and the resistance of thermistor 7 constitute a bridge circuit. Capacitor 9 suppresses surge voltage and protects thyristor 8.

Next, the operation of the water temperature detection unit and its surrounding parts will be explained. When you pull switch 4,
The circuit between the battery 2, the indicator lamp 3, the switch 4, and the terminals B and C is connected, and this circuit functions. When the engine starts, the resistance value of the thermistor 7 is high because the temperature of the engine coolant is low, and the base voltage of the PNP transistors 15 and 16 is determined by the bridge circuit described above, and the PNP transistor 15 is turned off and the PNP transistor 16 is turned on. There is. Therefore, no voltage appears across the resistor 14 and the thyristor 8 is turned off. When the resistance value of the thermistor 7 decreases as the temperature of the engine coolant increases, the pnp transistors 15, 1
The base voltage of 6 changes and pnp at the set temperature operating point.
Transistor 15 turns on, pnp transistor 1
6 is reverse biased between its emitter and base, and the pnp transistor 16 is turned off. For this reason, the resistor 14
A voltage appears, this voltage is applied to the gate of thyristor 8, turning on thyristor 8, a large current flows from battery 2 to thyristor 8 via indicator lamp 3 and switch 4, and indicator lamp 3 lights up. However, the driver is informed that the temperature of the engine coolant has reached a predetermined temperature.

FIG. 2 is a sectional structural view of the water temperature detection unit shown in FIG. 1, and FIG. 3 is an external view thereof. This water temperature detection unit has two functions as mentioned above: the function of displaying the temperature of the engine coolant on the thermometer, and the function of indicating to the driver when the temperature of the coolant has reached a predetermined temperature. With its built-in features and unique thermal structure,
It is designed to accurately transmit water temperature to the thermistor and to speed up the thermistor's thermal response to water temperature. In the figure, the terminal C in FIG. 1 is a threaded portion of the metal case 17. This water temperature detection unit is attached to the engine, and the screw portion C is tightened to the engine, and the metal case 17 is electrically connected to ground at the same time as the structural attachment. Further, at this time, the metal case 17 is attached in such a manner that the temperature detection surface 31 is in contact with the engine cooling water.
A and B in the figure are terminals corresponding to terminals A and B in FIG. 1. Terminals A and B are faston terminals, and these terminals are fixed to a terminal block 23 fixedly provided within the metal case 17. 22 is O for airtightness
It's a ring. Also, inside the metal case 17, an insulator 19 is attached and the diameter is normally 0.635 mm. 0.8mm
A thick film substrate 18 having a thickness of approximately 100 mL is stored. Ceramic, which has good thermal conductivity, is used as a material for this thick film substrate. The insulator 19 serves as a barrier to prevent the thick film substrate 18 from coming into contact with the inner wall of the metal case 17. Resistors 10 to 14 are printed on the thick film substrate 18, as well as a capacitor 9, a thyristor 8, and pnp transistors 15 and 1.
6. A thermistor 7 is mounted, and these components are connected by solder to form a water temperature detection circuit. The thermistor 6 is disk-shaped and has electrodes on the top and bottom, one of which is connected to the metal case 17.
The other electrode is in contact with the connecting electrode 27. One end of the spring holder 21 is in contact with the terminal block 23, and the spring holder 21
A coil spring 20 is provided between the other end of the insulator 19 and the convex portion 29 of the insulator 19 . The insulator 19 is connected to the metal case 1 by the coil spring 20.
An end surface 30 that is pushed toward the bottom surface 28 of the thick film substrate 19 and perpendicular to the longitudinal direction of the thick film substrate 18 mounted on the insulator 19 has a certain constant shape determined by the shapes and dimensions of the coil spring 20 and the spring retainer 21. It is pressed against the bottom surface 28 via the connecting electrode 27 and thermistor 6 by the spring force of. Therefore, the bottom 32 of the metal case 17, the thermistor 6, and the connection electrode 27 are electrically connected, and the bottom 32, the thermistor 6, the connection electrode 27, and the thick film substrate 18 are thermally conductively connected. Terminal A has a lead wire 25, a connecting electrode 27,
It is connected to the metal case 17 via the thermistor 6, and the terminal B is connected to the lead wire 26, the input terminal of the thick film board 18, the electronic circuit of the thick film board 18, and the thick film board 1.
The ground terminal 8 is connected to the metal case 17 via the ground ring 24. The thermistor 6 detects the temperature of engine cooling water in contact with the temperature detection surface 31 at a nearby position. Further, the temperature of the engine cooling water is conducted from the temperature detection surface 31 to the thick film substrate 18 through the bottom portion 32, the thermistor 6, and the connection electrode 27, and another thermistor 7 mounted near the end surface 30 of the thick film substrate 18 The temperature of the engine coolant is detected by detecting the temperature of the substrate. At this time, since the thick film substrate 18 is made of a ceramic material with good thermal conductivity, it has excellent thermal responsiveness, and the temperature of the thick film substrate 18 changes to follow the temperature change of the engine coolant without delay. Therefore, the thermistor 7 can accurately and quickly detect the temperature of the engine coolant.

Since the chip component mounting surface of the thick film substrate 18 or its backing surface has a large surface area, these surfaces are normally used as heat conduction surfaces. A major feature is that the cross section is used as a heat conduction surface. Furthermore, since the metal case 17 is attached to the engine, there is a dimensional restriction in that it must be elongated, and the inner diameter of the metal case 17 is approximately 9 mm or less, and its length is approximately 30 mm. As a result of our pursuit of a device that could house the necessary temperature detection circuit and other components in a metal case with such an internal volume and that also satisfied the required functions, we decided to connect the end surface 30 of the thick film substrate 18 as described above to the connecting electrode 27, Thermistor 6
A water temperature detection unit has been realized which is configured to press against the bottom surface 28 of the metal case 17 through the temperature detection surface 31 and detect the temperature of the engine cooling water by receiving heat conduction from the temperature detection surface 31. In addition, in this invention, the water temperature detection circuit is electronic, which improves the accuracy of detecting the engine coolant temperature, and furthermore, this temperature detection utilizes the good thermal conductivity of the metal case and ceramic substrate. , has accurate and fast thermal response temperature detection characteristics. Therefore, this water temperature detection unit is extremely excellent as a unit for displaying the temperature of the engine cooling water of an automobile. Also,
This water temperature detection unit is fully applicable as an electronics unit to replace the conventional cylindrical temperature detector.

[Effects of the Invention] As described above, according to the present invention, a thick film substrate with good thermal conductivity is housed in a metal case having a temperature detection surface on its outer surface, and the temperature of this substrate is detected by the thick film substrate. A thermistor is provided, and in order to transmit the temperature of the temperature detection surface of the metal case to the thick film substrate, the end surface perpendicular to the length direction of this substrate is pressed by the pressing means against the inner surface of the metal case corresponding to the temperature detection surface. Therefore, the temperature of the temperature detection surface is accurately and quickly transmitted to the thick film substrate, and the thermistor can accurately detect the temperature of the temperature detection surface by detecting the temperature of this substrate. Therefore, it is possible to obtain a temperature detection unit that is accurate and has quick thermal response.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a water temperature detection unit and its peripheral parts when the water temperature detection unit is applied to an automobile, which is an embodiment of the present invention. Figure 2 shows the cross-sectional structure of the water temperature detection unit in Figure 1, and the third
The figure shows its outline. In the figure, 1 is a water temperature detection unit, 2 is a battery, 3 is a display lamp, 4 is a switch,
5 is a thermometer, 6, 7 is a thermistor, 8 is a thyristor, 9 is a capacitor, 10, 11, 12, 13,
14 is a resistor, 15, 16 pnp transistor, 17
18 is a metal case, 18 is a thick film substrate, 19 is an insulator, 20 is a coil spring, 21 is a spring holder, 2
2 is an O-ring, 23 is a terminal block, 24 is a ground ring, 25 and 26 are lead wires, 27 is a connection electrode, 2
8 is a bottom surface, 29 is a convex portion, 30 is an end surface, 31 is a temperature detection surface, and 32 is a bottom portion. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A metal case having a temperature detection surface on its outer surface; a thick film substrate with good thermal conductivity housed in the metal case; and a thick film substrate provided on the thick film substrate. a thermistor that detects the temperature of the metal case; and an end face perpendicular to the length direction of the thick film substrate is arranged within the inner surface corresponding to the temperature detection surface of the metal case so that the temperature of the temperature detection surface of the metal case is transmitted to the thick film substrate. A temperature detection unit equipped with a pressing means for pressing the surface. 2. The temperature detection unit according to claim 1, wherein the thick film substrate is a ceramic substrate.