JPH06237521A - Detection circuit of operating defect of relay - Google Patents

Abstract

PURPOSE:To limit a contract for a relay which is likely to be welded and to limit a welding detection means to one part by a method wherein the continuity and the cutoff of contacts for two relays which are connected in series are prioritized. CONSTITUTION:A circuit is formed in such a way that a first relay 1, a second relay 2 and a motor 3 which have been connected in series are connected in series with a power supply E1 and that the motor 3 is driven by the make-and- break of the relays. A contact 2a for the second relay 2 is cut off by an ECU 5 when a contact 1a for the first relay 1 is operated. Thereby, most of the possibility that the contact 1a for the first relay 1 is welded is eliminated, and the welding which is detected by a sensor 4 is limited to only the contact 2a for the second relay 2. When the welding is detected, the contact 1a for the first relay 1 is cut off, and a continuous energized state to the motor 3 is released.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relay malfunction detection circuit. More specifically, the present invention relates to a malfunction detection circuit for a relay that prevents continuous energization of a motor during welding of the relay.

[0002]

2. Description of the Related Art The conventional general structure of a circuit for preventing continuous energization of a motor due to welding of a relay is described in Japanese Utility Model Publication No. 3-83.
This is disclosed in Japanese Patent No. 440 as prior art. Figure 3
FIG. 3 is a block diagram of a circuit for preventing continuous energization of a load when welding a relay in the related art. The overall configuration is a power supply E2,
It is composed of a drive circuit, a first operating circuit, and a second operating circuit. The drive circuit is connected in series with the power supply E2,
The contact 10a of the relay 10, the contact 11a of the relay 11, and the load 12 are connected in series. The first operating circuit is
The coil 10b of the relay 10 that drives the contact 10a of the relay 10 is connected in parallel to the drive circuit. The second operation circuit is a relay 11 that drives a contact 11 a of the relay 11.
The coil 11b is connected to the drive circuit in parallel. The switch SW3 is connected upstream of the coil 10b of the relay 10 of the first operating circuit, and the relay 11 of the second operating circuit is connected.
A switch SW4 is connected upstream of the coil 11b. If the contact 10a of the relay 10 is welded and is in a continuous energization state, the switch SW4 is cut off to cut off the second operation circuit and forcibly cut off the contact 11a of the relay 11 to the load 12. It is possible to prevent the continuous energization state of. Also, the contact 1 of the relay 11
When 1a is welded and becomes a continuous energization state, the switch SW3 is cut off to cut off the first operation circuit and forcibly cut off the contact 10a of the relay 10 to prevent the continuous energization state to the load 12. can do.

[0003]

However, in this prior art, since there is no means for detecting the welding of the contact of the relay and the passenger cannot be notified, the contact 10a of the relay 10,
Alternatively, if the contact 11a of the relay 11 is welded, the occupant may not notice it, and cannot switch off the switch SW3 or the switch SW4. Therefore, the load 12 may fail due to the continuous energization of the load 12. There was a problem. In order to solve this problem, the inventor of the present invention has conceived that the circuit is provided with a detection means for detecting the welding of the contacts of the relay to forcibly shut off the relay. However, in the conventional circuit described above, the relay 10 and the relay 1
Since the connection and disconnection of No. 1 can be freely operated, there is a possibility that both the contacts 10a of the relay 10 and the contacts 11a of the relay 11 will be welded. Therefore, in order to determine which of the relay contacts has been welded, there is a problem in that welding detection means must be provided for both the relay contacts 10a and the relay 11 contacts 11a. Therefore, an object of the present invention is to pay attention to the fact that if the current does not flow during the operation of the contact of the relay, the contact of the relay has almost no possibility of welding, and the contact between the two relays connected in series is electrically connected. By prioritizing the interruption, the contacts of the relay that may be welded are limited and the welding detection means is limited to one place.

[0004]

In order to solve the above-mentioned problems, a malfunction detecting circuit for a relay according to the present invention comprises a power source, a contact of a first relay and a contact of a second relay connected in series. A drive circuit in which a motor is connected in series with the power supply, a first switch, a coil of the first relay, and a first switching element connected in series are connected in series to the power supply and in the drive circuit. A first operation circuit connected in parallel, a coil of the second relay and a second switching element connected in series, which are downstream of the first switch and the coil of the first relay; A second operation circuit connected in parallel with the first switching element, a sensor connected upstream of the motor for detecting a potential, and a first switch at a normal time at least when the first switch is conductive. To conduct ring element, together to conduct the second switching element based on the operating instruction to the motor when the conduction of the first switch, the first
Control means for cutting off the first switching element under the condition that the potential detected by the sensor is equal to or higher than a predetermined value when the switch is turned on and the second switching element is cut off.

[0005]

When the first switch is turned on by the above means, the control means turns on the first switching element and the first operating circuit so that a current flows through the coil of the first relay. , The contacts of the first relay are conductive. Then, when the operation of the motor is instructed, the second switching element is made conductive by the control means, the second operation circuit is made conductive, and a current flows through the coil of the second relay, whereby the contact of the second relay is made. Becomes conductive and current flows through the drive circuit to operate the motor. Next, when the stop of the motor is instructed, the control means shuts off the second switching element, shuts off the second operation circuit, and shuts off the contact of the second relay, thereby shutting off the drive circuit. The motor will stop. However, if the contact of the second relay is welded here, a sensor connected upstream of the motor of the drive circuit detects the potential of the drive circuit, and the control means determines that the potential of the drive circuit is equal to or higher than a predetermined value. Acknowledge that there is and shut off the first switching element. When the first switching element is cut off, the first operation circuit is cut off and the contact of the first relay is cut off, so that the drive circuit is cut off and the motor is stopped.

[0006]

Next, a first embodiment of the present invention will be described. FIG. 1 is a block diagram of a relay malfunction detection circuit according to the first embodiment of the present invention. The drive circuit is the power source E
1 is connected in series with the contact 1a of the first relay 1 and the second
The contact 2a of the relay 2 and the motor 3 are connected in series. A switch SW1 as a first switch, a coil 1b of the first relay 1 for driving a contact 1a of the first relay 1, and a coil 1b as a first switching element are connected in series to the power source E1 and in parallel with the drive circuit. It is connected to the transistor Tr1. This switch SW1
Is a switch which is interlocked with an ignition switch (not shown) of the vehicle and which is turned on by turning on the ignition switch. Also, the switch SW1
The coil 2b of the second relay 2 for driving the contact 2a of the second relay 2 in parallel with the coil 1b of the first relay 1 and the transistor Tr1 is connected to the transistor Tr2 as the second switching element. Has been done. A sensor 4 for detecting a potential is connected to a point A between the contact 2a of the second relay 2 of the drive circuit and the motor 3. The sensor 4 is connected to an ECU 5 as a control means for controlling the transistor Tr1 and the transistor Tr2, and an indicator 6 that lights up when welding is detected is connected to the ECU 5. The ECU 5 is connected to the power source E1 via the switch SW1 and also connected to the switch SW2 for driving the motor. The switch SW2 may be a manual switch or a switch that is automatically turned on and off under certain conditions. The transistor Tr1 is a switch SW
The first relay 1 conducts at the same time as the first conduction, and the coil 1b of the first relay 1
ECU 5 so that the contact 1a of the first relay 1 is cut off when the welding of the contact 2a of the second relay 2 is detected.
Controlled by. The transistor Tr2 is a switch S
The ECU 5 controls so that the contact 2a of the second relay 2 is turned on and off by turning on and off the coil 2b of the second relay 2 simultaneously with the turn-on of W2. Then, the ECU 5 uses the switch SW1
Is turned on and the transistor Tr2 is turned off, and the sensor 4
The transistor Tr1 is cut off under the condition that the potential detected by is equal to or higher than a predetermined value. Further, the sensor 4 has a switch SW1.
Is also conducted, and the transistor Tr2 is conducted, that is, when the current flows through the drive circuit and the motor 3 is being driven, the potential is detected and the overcurrent to the motor 3 is monitored.

Next, the operation of the first embodiment of the present invention will be described. FIG. 2 is a flowchart showing a flow of operations of the ECU 5 in the first embodiment of the present invention. Hereinafter, this flow chart will be described. In step (hereinafter referred to as S) 20, it is checked whether or not the switch SW1 which is interlocked with the ignition switch is turned on. S2 when switch SW1 is cut off
Go to 1 and turn off the transistor Tr1. When the switch SW1 is turned on, the process proceeds to S22 to turn on the transistor Tr1. When the transistor Tr1 becomes conductive, a current flows through the coil 1b of the first relay 1 and the contact 1a of the first relay 1 becomes conductive. Then S
At 23, it is checked whether or not the switch SW2 for operating the motor 3 is conducting. When the switch SW2 is conductive, the process proceeds to S24, and the transistor Tr2 is conductive. When the transistor Tr2 becomes conductive, a current flows through the coil 2b of the second relay 2, whereby the contact 2a of the second relay 2 becomes conductive and a current flows through the drive circuit to operate the motor 3. If the switch SW2 is cut off, the process proceeds to S25 to cut off the transistor Tr2. When the transistor Tr2 is cut off, the contact 2a of the second relay 2 is cut off, so that the drive circuit is cut off and the motor 3 is stopped. Next, in S26, it is checked whether or not the potential detected by the sensor 4 is equal to or higher than a predetermined value, that is, whether or not the motor 3 is energized. When it is determined that it is equal to or more than the predetermined value, it is determined that the contact 2a of the second relay 2 is welded, the process proceeds to S27, the transistor Tr1 is cut off, and the first relay is turned off. The motor 3 is stopped by disconnecting the contact 1a of 1 and the drive circuit. And
In S28, the indicator 6 is turned on. Also,
When the switch SW1 is turned on and the transistor Tr2 is turned on, the sensor 4 is looking at the potential upstream of the motor 3 and downstream of the contact 2a of the second relay 2. Then, when the sensor 4 detects that an overcurrent detected when an excessive load is applied to the motor 3 is flowing to the drive circuit, the ECU 5 turns off the transistor Tr1 and the transistor Tr2 at the same time, and the first By disconnecting the contact 1a of the relay 1 and the contact 2a of the second relay 2, the drive circuit is disconnected and the motor 3 is stopped.

As described above, in the normal operation, the relay malfunction detection circuit according to the first embodiment of the present invention is
When the contact 1a of the relay 1 is turned on and off, the contact 2a of the second relay 2 is always cut off. Therefore, the drive circuit is cut off, and the contact 1a of the first relay 1 is
No current flows in the drive circuit during the operation of turning on and off. When the contact 1a of the first relay 1 is turned on and off, a current flows in the drive circuit when the welding of the second relay 2 is detected and when an overcurrent flows in the motor 3 and the motor 3 is forced. Since it is only to stop at
There is almost no possibility of welding the contact 1a of the first relay 1. Therefore, only the contact 2a of the second relay 2 needs to be welded and detected, so that it is not necessary to provide a sensor other than the sensor 4. Further, the contact 1a of the first relay 1 is conducting in conjunction with the conduction of the switch SW1, and when the motor 3 is driven, only the second relay 2 is conducting, so that the operating noise of the relay does not overlap. The relay noise when the motor 3 is driven can be reduced. Furthermore, the first
Since the contact 1a of the relay 1 is previously conducted and only the contact 2a of the second relay 2 is conducted based on the switch input for driving the motor 3, the response of the drive of the motor 3 to the switch input is Is good. Further, the sensor 4 detects the potential even when the motor 3 receives some load and an overcurrent flows in the drive circuit, and the ECU 5 shuts off the transistor Tr1 and the transistor Tr2.
Since the drive circuit is cut off by cutting off the first relay 1 and the second relay 2, it is possible to stop the motor 3 and prevent the failure of the motor 3 in advance.

Further, a sounding device such as a buzzer may be used instead of the indicator 6.

[0010]

In the circuit for detecting malfunction of the relay according to the present invention, the contact of the second relay is always cut off when the contact of the first relay is turned on and off, so that the drive circuit is cut off. In other words, no current flows in the drive circuit during the operation in which the contact of the first relay is conducted and cut off, so that there is almost no possibility of welding the contact of the first relay. Therefore, only the contact of the second relay needs to be detected by welding, so that one sensor can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram of a relay malfunction detection circuit according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing a flow of operations of the ECU 5 in the first embodiment of the present invention.

FIG. 3 is a block diagram of a circuit for preventing continuous energization of a load when welding a relay according to a conventional technique.

[Explanation of symbols]

1, 10 ・ ・ ・ First relay 2, 11 ・ ・ ・ Second relay 3 ・ ・ ・ Motor 4 ・ ・ ・ Sensor 5 ・ ・ ・ ECU (control means) 6 ・ ・ ・ Indicator 12 ・ ・ ・ Load E1 , E2 ... Power source SW1 ... First switch SW2, SW3, SW4 ... Switch Tr1 ... Transistor (first switching element) Tr2 ... Transistor (second switching element)

Claims (1)

[Claims] 1. A power supply, a drive circuit in which a contact of a first relay, a contact of a second relay and a motor connected in series are connected in series to the power supply, and a first connected in series Switch, the coil of the first relay, and the first switching element are connected to the power source in series and in parallel to the drive circuit, and the second relay connected in series. Of the motor and the second switching element are connected downstream of the first switch and in parallel with the coil of the first relay and the first switching element; A sensor that is connected upstream and detects a potential, and that normally causes the first switching element to conduct when at least the first switch conducts, and based on an operation instruction to the motor when the first switch conducts. The first switching is performed under the condition that the potential detected by the sensor is equal to or more than a predetermined value when the second switching element is turned on and the first switch is turned on and the second switching element is turned off. A relay operation failure detection circuit comprising: a control unit that shuts off an element.