JP3483098B2 - Overcurrent protection device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overcurrent protection device used to protect a circuit and equipment by cutting off the current when a current larger than a designed value flows in a circuit to which a load is connected. .

[0002]

2. Description of the Related Art As a protection circuit using a PTC element having a positive temperature resistance coefficient for protecting a circuit against an overcurrent, as shown in FIG. 4, a series of circuits consisting of a power supply a, a switch b and a load c. On the other hand, the PTC element d is arranged in series, and when an abnormal state occurs in the circuit or the load and an overcurrent occurs, the circuit is cut off by utilizing the increase in resistance value due to the heat generation of the PTC element d. It is known how to do it.

However, the PT used in the above protection circuit
The C element d needs to set the current capacity of the PTC element d according to the capacity of the load, and when the current value is large (for example, 10 A or more) as in the power supply circuit of an automobile, P
The TC element d is also required to have a large capacity, and the PTC element d itself must be upsized or a plurality of elements must be connected in parallel, which causes problems such as an increase in cost and an increase in accommodation space. ing.

[0004]

The present invention has been made in view of the above problems, and it is not necessary to increase the capacity of the PTC element itself even in a load circuit that requires a large current, and it is small and lightweight. An object of the present invention is to provide an overcurrent protection device that can reliably shut off overcurrent.

[0005]

In order to solve the above-mentioned problems, in the invention of claim 1, in the overcurrent protection device in which the current supplied to the load is performed by opening and closing a relay, A bus bar formed of a thin metal plate that supplies an electric current, a narrowed portion provided on the bus bar, a temperature detection element that changes characteristics in accordance with the temperature of the narrowed portion, the narrowed portion and the temperature detection element. And an insulating layer provided between the relay and a control unit that controls an exciting current of a coil that opens and closes the relay based on a characteristic change of the temperature detecting element. In the invention of claim 2, the temperature detecting element is a PTC element whose resistance value changes with temperature. The bus bar is provided with a constriction portion, the temperature rise due to the heat generated in the constriction portion is detected by the temperature detection element such as the PTC element through the insulating layer, and the exciting current of the coil is controlled based on the detected characteristic change to relay. Since the opening and closing are controlled, the overcurrent can be surely cut off with a small size and a light weight. In addition, since an insulating layer is provided between the constriction and the temperature detection element, current does not flow from the constriction through the electrodes of the temperature detection element, and heat generation in the constriction is designed without considering other factors. You can do it on the street.

According to the third aspect of the present invention, the bus bar including the narrowed portion or only the narrowed portion is insulation-coated with the temperature detecting element. Since the temperature detecting element and the bus bar are both insulated-coated, the temperature detecting element can be easily attached to the bus bar.

According to the invention of claim 4, an insulating layer provided between the narrowed portion and the temperature detecting element is provided.
The insulating coating is used to form the insulating coating. Since the insulating layer is formed by the insulating coating when the insulating layer is applied, the insulating layer can be easily formed.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIGS. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is a mounting view of a temperature detecting element on a bus bar, (A) is a plan view, and (B) is a sectional view. In FIG. 1, A is an overcurrent protection device, and bus bars 1A and 1
B, a relay 2, a temperature detection element 3 and a control unit 4. One ends of the bus bars 1A and 1B are connected to the load 5 via contacts 2A and 2A 'of the relay 2, and the other ends are connected to a power source such as a battery (not shown) via a fuse 6.

The control unit 4, which will be described later with reference to FIG. 3, changes the characteristics of the temperature detecting element 3 depending on the temperature of the connecting line 3A.
And 3B to control the current flowing through the coil 2B of the intake relay 2 to control the opening and closing of the contacts 2A and 2A '.

As shown in FIGS. 2A and 2B, the temperature detecting element 3 is mounted on the bus bar 1B by mounting the PTC element 31 as a temperature detecting element on the narrowed portion 1B 'provided on the bus bar 1B. Do it. The length and width of the narrowed portion 1B 'are determined by the amount of heat generated based on the overcurrent value that protects the load 5. That is, by forming the narrowed portion 1B ', the electric resistance value of the bus bar 1B in the portion of the narrowed portion 1B' becomes high, and heat is generated to raise the temperature. The amount of heat generation is based on the design value, and the length and width of the narrowed portion 1B 'are determined so that the design value heat is generated.

Electrodes 32 and 33 are attached to both surfaces of the PTC element 31, terminals 32A and 33A are provided at the respective ends, and connection lines 3A and 3B are connected.

The PTC element 31 is mounted by being insulation-coated between the one electrode 32 and the narrowed portion 1B 'via an electrically insulating insulating layer 1C. In the figure, 1D indicates an outer insulating coating layer. Insulating layer 1C is electrode 32
It is only for insulation between the bus bar 1B and the bus bar 1B, and one having good heat conduction is desirable. As described above, the insulating layer 1C covers the PTC element 31 in the narrowed portion 1.
A coating material may be used to form B ′ at the same time as the insulating coating.

By thus insulating between the electrode 32 of the PTC element 31 and the narrowed portion 1B ', the narrowed portion 1
Since no current flows from B ′ through the electrode 32, the amount of heat generated in the narrowed portion 1B ′ can be performed as designed without considering other factors.

FIG. 3 shows a configuration example of the control unit 4,
(A) shows the case where the control unit 4 is composed of only the battery 41. When the temperature of the constricted portion 1B 'is low (when a normal current is flowing through the load), the resistance value of the PTC element 31 is low, so that a large current flows through the coil 2B of the relay 2 and the contact point of the relay 2 is reached. 2A and 2A 'are closed. When the temperature of the narrowed portion 1B 'is high (when an overcurrent flows through the load), the resistance value of the PTC element 31 becomes high, so that the current flowing through the coil 2B of the relay 2 decreases and the contacts 2A and 2A of the relay 2 are reduced. ′ Is open, protecting the load 5 from overcurrent.

Further, in the configuration of FIG. 3B, the case where the amplifier 43 is used to increase the current flowing through the coil 2B is shown, and the current flowing from the battery 41 through the PTC element 31 and the resistor 42 is shown. Resistance 42 generated by
I am trying to amplify the voltage.

In the above embodiment, P is used as the temperature detecting element 3.
Although the TC element 31 is used, if the temperature detecting element 3 has characteristics that change with temperature,
Any element may be used, such as a thermistor or a thermocouple.

[0017]

As described above, according to the present invention, the following effects can be obtained. The bus bar is provided with a constriction portion, the temperature rise due to the heat generated in the constriction portion is detected by the temperature detection element such as the PTC element through the insulating layer, and the exciting current of the coil is controlled based on the detected characteristic change to relay. Since the opening and closing are controlled, the overcurrent can be surely cut off with a small size and a light weight. In addition, since an insulating layer is provided between the constriction and the temperature detection element, current does not flow from the constriction through the electrodes of the temperature detection element, and heat generation in the constriction is designed without considering other factors. You can do it on the street.

Since the temperature detecting element and the bus bar are both insulation-coated, the temperature detecting element can be easily attached to the bus bar. Further, since the insulating layer is formed by the insulating coating when the insulating layer is coated, the insulating layer can be easily formed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

2A and 2B are mounting views of the temperature detecting element of the embodiment on a bus bar, FIG. 2A is a plan view and FIG. 2B is a sectional view.

FIG. 3 is a specific example of a control unit of the same embodiment.

FIG. 4 is an explanatory diagram of a conventional example.

[Explanation of symbols]

A Overcurrent protection device 1A, 1B Busbar 1B 'stenosis 1C insulation layer 1D insulation coating layer 2 relay 2A, 2A 'contact 2B coil 3 Temperature detection element 31 PTC element 32, 33 electrodes

Claims (4)

(57) [Claims] 1. An overcurrent protection device in which a current supplied to a load is controlled by opening and closing a relay, and a bus bar formed of a thin metal plate for supplying a current to the load, and a constriction provided in the bus bar. Based on the characteristic change of the temperature detection element, an insulating layer provided between the narrowed portion and the temperature detection element An overcurrent protection device comprising: a control unit that controls an exciting current of a coil that opens and closes the relay. 2. The temperature detecting element is a PTC element whose resistance value changes with temperature.
The overcurrent protection device described. 3. The overcurrent protection device according to claim 1, wherein the bus bar including the narrowed portion or only the narrowed portion is insulation-coated with the temperature detecting element. 4. The insulating layer according to claim 3, wherein an insulating layer provided between the narrowed portion and the temperature detecting element is formed by the insulating coating when the insulating coating is performed. Current protection device.