JPS5917964B2 - resistor printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is suitable for use as a resistor printed wiring board in which a contact terminal slides on a resistor circuit surface and provides a predetermined resistance value, and more specifically, as a sensor for indicating the amount of gasoline in an automobile. This invention relates to a resistor printed wiring board.

Currently used as gasoline level display sensors for automobiles, a nickel-based resistance foil is attached to an alumite plate with adhesive and then etched to create a resistance circuit whose resistance value varies stepwise in the direction of the sliding force.This resistance value is used to display the meter. Types that display the amount of remaining oil are used.

However, when so-called gasohol, which is a mixture of gasoline and alcohol, came to be used to reduce dependence on petroleum from a resource standpoint, concerns arose about the gasohol resistance of the adhesive.

Therefore, when printing paste for thick film circuits was applied on enamel and fired to create a circuit, the glass value of the enamel and the glass quality of the paste melted and became one, and the problem of the decrease in adhesive strength mentioned above disappeared, but thick film printing paste The circuit created by this method is porous and has large irregularities due to its nature, and the sliding of the contact terminal causes wear from the surface, causing the resistance value to change and the meter reading to gradually become erroneous.

Further, even when a resistor paste with a glassy binder is not used, there is a drawback that when a contact terminal slides on the surface of a resistor, the resistor is worn out and the resistance value changes.

The present invention has been made in view of these points, and is a resistor printed wiring board in which a resistor circuit is formed on an enamel substrate, and a contact terminal slides on the resistor circuit surface to provide a predetermined resistance value. A resistor circuit is provided with a conductor arranged at a large number of predetermined intervals in the direction of movement of the contact terminal so that conduction and disconnection are repeated by the sliding of the contact terminal, and a resistor circuit connected to the conductor on both sides of the conductor. It is characterized by comprising a resistor that has a predetermined resistance value at a predetermined position in the length direction.

FIG. 1 shows an embodiment of the present invention, in which the present invention is applied to a resistor circuit board used in a sensor for displaying the amount of gasoline.

In Fig. 1, 1 is an enamel substrate, 2 is a resistor circuit, and 3 is a plurality of stages 4 arranged at predetermined intervals in the direction of movement of the contact terminals, and arranged so that conduction and interruption are repeated by sliding the contact terminals. A conductor, 5 is a resistor having a predetermined resistance value at a predetermined position in the length direction on both sides of the conductor 30, 6 is a grounding conductor, and 7 is a notch for fixing the board to the shelter. be.

Resistor binding or resistor paste with a vitreous or organic binder such as ruthenium oxide paste is preferred.

As the conductor, a conductor paste with a vitreous or organic binder, such as a conductor paste containing a mixture of silver thread, lead, and palladium, is preferable.

The resistor paste and the conductor paste are used to form a circuit on a substrate by a printing method or the like according to a conventional method.

The dimensions of the resistor are determined by the required resistance value, and the conductor is determined by the dimensions and shape of the tip of the sliding contact terminal.

The width of the non-circuit part to be made in the conductor is influenced by the size and shape of the contact terminal, but when the terminal is in 2H, it should be less than 2 mm; if it is too large, the terminal will get stuck and work will be poor.

If the conductor is made thinner than the resistor, that is, the surface of the conductor is lower (and concave) than the surface of the resistor, there will be fewer accidents in which the contact terminal comes off from the conductor due to shaking.

Example: In the gasoline amount display sensor, a conductor circuit for the sliding contact terminal to be formed in the center of the resistor circuit as shown in Fig. 1 (using conductor paste 7712 manufactured by DuPont), and the position from the origin increases as the terminal goes up and down. Resistor (Resistance element pace manufactured by Shoei Chemical Industry Co., Ltd.) R-60 so as to show a predetermined resistance value
1) was divided into two parts and provided on both sides of the sliding conductor.

Note that the thickness of the conductor was 10 μm, and the thickness of the resistor was 20 μm.

Comparative Example 1 In the example, the resistor was provided on one side of the sliding conductor as shown in FIG.

The sliding conductor was made of 3M and was the same as in the example.

Comparative Example 2 In the example shown in FIG. 3, the sliding terminal whose resistance circuit was entirely made of resistors moved up and down on the resistor.

Two types of 5.5' resistors with different sheet resistances were used to exhibit a predetermined change in resistance value in the length direction.

The resistance circuit boards for sensors obtained in the Examples and Comparative Examples were subjected to 150,000 times sliding tests in Galarin, and the rate of change from the initial value of the resistor and the operability of the contact terminals were examined.The results are as follows. Shown in the table.

*In order to prevent it from coming off, change the width of the example from 3 to 2.
It needed to be more than doubled.

The effects obtained with the resistor printed wiring board of the present invention described above are as follows.

(1) Compared to the conventional resistance value sliding type, the rate of change in resistance value due to sliding has been greatly reduced, improving the reliability of the sensor.

(2) Since the resistor is coupled to the conductor and arranged on both sides of the conductor on which the contact terminal slides, even if the contact terminal swings laterally, it is unlikely to come off from the resistance circuit.

(3) Contact terminals slide horizontally due to play due to dimensional changes during component manufacturing, but if the conductor is lower than the resistor, the lower conductor and the higher positions on both sides Because it is sandwiched between certain resistors, there is less vibration and stable operation.

For this reason, compared to a method in which the conductor is placed on one side, the amount of conductor in the sensor can be reduced, thereby preventing an increase in price due to an increase in the size of the sensor.

[Brief explanation of the drawing]

The drawings are surface views of a resistor circuit board of a sensor for displaying the amount of gasoline, and FIG. 1 shows one using the resistor printed wiring board of the present invention, and FIGS. 2 and 3 show conventional ones. Explanation of symbols 1... Enamel substrate, 2... Resistance circuit, 3
... Conductor, 4... Spacing, 5, 5'-... Resistor,
6... Grounding conductor, 7... Notch.

Claims (1)

[Claims] 1 In a resistor printed wiring board in which a resistor circuit is formed on an enamel substrate and a contact terminal slides on the resistor circuit surface to provide a predetermined resistance value, the resistor circuit is arranged at a predetermined interval in the direction of movement of the contact terminal. A conductor is provided with a large number of conductors and is arranged so that conduction and disconnection are repeated by sliding contact terminals, and a conductor is connected to the conductor on both sides of the conductor so that a predetermined position in the length direction has a predetermined resistance value. A resistive printed wiring board characterized by comprising a resistor made as shown in FIG.