JP2010172049A - Cable protection circuit and cable protection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cable protection circuit which is possible of reduction of cable cost and cable weight by minimizing the tolerable current value of a cable used for a motor driving circuit as much as possible. <P>SOLUTION: A motor driving circuit, in which a power source 12 and a motor 14 are connected with each other by a cable 18, is provided with a circuit breaking means 16, and the circuit breaking means 16 is equipped with a return type circuit breaker 161, which can return to the previous state even if it operates once, and the minimum operation current Ib of the return type circuit breaker is set to be larger than the rated current value Ir of the motor 14, and the time taken for the return type circuit breaker 26 to operate in case that a current larger than the minimum operating current value Ib flows to the motor driving circuit is set to be shorter than the time taken for the cable 18 to burn, and the tolerable current value Ic of the cable 18 is set to be smaller than a motor lock current value If which flows to the motor driving circuit in case that the motor 14 is locked. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric wire protection circuit and an electric wire protection method, and more particularly, in order to prevent the electric wire constituting the motor drive circuit due to energization of an overcurrent from being burned, a circuit interruption means for interrupting the circuit in the event of an abnormality is provided in the motor drive circuit. The present invention relates to an electric wire protection circuit provided and a method for protecting electric wires in a motor drive circuit by means of circuit interruption means.

  For example, as described in Patent Document 1, a drive circuit that drives a device such as a motor includes a circuit breaker having a fuse in order to prevent burnout of an electric wire due to energization of an overcurrent. Specifically, like the electric wire protection circuit 100 shown in FIG. 7, the power source 102 and the motor 104 are connected by the electric wire 108 via the fuse 106 using a molten metal that melts at a predetermined temperature.

  In a vehicle power window device, a wiper drive device, or the like having such a motor drive circuit, the motor 104 that drives the window glass or the wiper may be locked due to icing or foreign object pinching. At this time, a current several times the rated current value Ir of the motor flows through the electric wire 108 constituting the drive circuit. Therefore, the fuse 106 as the circuit breaker generally has characteristics as shown in FIG.

  FIG. 8 is a curve Cf showing the time relationship until the fuse 106 is activated (blown), the magnitude of the current flowing through the electric wire 108 (motor drive circuit), and the electric wire 108 burned out (the coating material is melted due to the heat generation of the core wire). The curve Cc showing the relationship between the time until smoked) is referred to as the rated current value Ir of the motor 14 used, and the current value flowing through the wire when the motor 104 is locked (the motor lock current value If. The same applies hereinafter). ). As can be seen from FIG. 8, the fuse 106 operates every time the motor lock occurs and cannot be bothered if the fuse 106 needs to be replaced. Therefore, when a current greater than the motor lock current value If is applied It is set to blow only.

JP-A-7-130277

  However, this motor drive circuit has a problem that the diameter of the electric wire 108 constituting the motor drive circuit is increased by selecting the fuse 106 that operates at the motor lock current value If or higher.

  That is, since the electric wire 108 used in the motor drive circuit is an object protected by the fuse 106, as shown in FIG. 8, the allowable current value Ic of the electric wire 108 (the electric wire is burned out due to a temperature rise). The current value with no current (refer to the Japan Electric Wire Industry Association Standard (JCS)) must be at least larger than the minimum operating current value Ib of the fuse 106 (minimum current value at which the fuse 106 blows). That is, in a device that needs to be designed in consideration of the motor lock current value If such as the power window device as described above, the diameter of the electric wire 108 used is larger than necessary (the rated current Ir of the motor 104 used is larger than necessary). It will be bigger). As a result, there has been a problem that the material cost of the electric wire 108 is increased, and an increase in the weight of the electric wire 108 causes an increase in the weight of the entire apparatus including the motor drive circuit.

  The problem to be solved by the present invention is to provide an electric wire protection circuit and an electric wire protection method capable of reducing electric wire cost and electric wire weight by minimizing the allowable current value of electric wires used in a motor drive circuit. It is in.

  In order to solve the above problems, an electric wire protection circuit according to the present invention is an electric wire protection circuit in which a circuit interruption unit is provided in a motor drive circuit in which a power source and a motor are connected by electric wires, and the circuit interruption unit includes: A return-type circuit breaker that can be restored even if it is once operated; a minimum operating current value of the reset-type circuit breaker is set to be larger than a rated current value of the motor; When a current larger than the minimum operating current value flows in the circuit, the time until the return-type circuit breaker is activated is set to be shorter than the time until the wire burns out, and the wire The gist of the allowable current value is set to be smaller than the motor lock current value flowing in the motor drive circuit when the motor is locked.

  Further, the wire protection method according to the present invention is a wire protection method in a motor drive circuit in which a circuit breaker is provided in a motor drive circuit in which a power source and a motor are connected by a wire, and the circuit breaker includes: A reset circuit breaker that can be reset even if it is once operated, and a minimum operating current value of the reset circuit breaker is set to be larger than a rated current value of the motor; When the current greater than the minimum operating current value flows in the circuit, the time until the reset circuit breaker is activated is set to be shorter than the time until the wire is burnt out, and the wire The gist of the invention is to set the allowable current value to be smaller than the motor lock current value flowing in the motor drive circuit when the motor is locked.

  The minimum operating current value in the above configuration refers to the minimum current value at which the circuit breaker operates (the circuit breaker does not operate when current less than the minimum operating current value is energized). The allowable current value of the electric wire means a minimum electric current value at which the electric wire is not burned (the covering material of the electric wire is melted or smoked).

  According to the present invention having such a configuration, since the return type circuit breaker that does not need to be replaced every time the circuit breaker operates is provided, the circuit breaker is the same as the conventional motor drive circuit. In consideration of the troublesome replacement of the fuse, it is not necessary to set the minimum operating current value at which the circuit breaker operates to be equal to or higher than the motor lock current. In other words, the minimum operating current value of the return type circuit breaker provided in the circuit breaker may be set to be equal to or higher than the motor rated current value, and thereby the allowable current value of the wire can be set to be equal to or lower than the motor lock current value. Therefore, the diameter of the electric wire can be made smaller than before, and the electric wire cost and the electric wire weight can be greatly reduced.

  The circuit breaking means further includes a non-return type circuit breaker that cannot be restored once activated, and the non-return type when a current larger than the minimum operating current value flows through the motor drive circuit. It is preferable that the time until the circuit breaker is activated is set to be longer than the time until the return-type circuit breaker is activated and shorter than the time until the wire is burned out.

  In this way, when the circuit breaker is added to the return type circuit breaker and a current of a predetermined magnitude flows in the motor drive circuit, it takes a long time to operate from the return type circuit breaker. By providing a type circuit breaker, even if the reset circuit breaker does not operate due to a failure, etc., the circuit is interrupted by the non-return type circuit breaker operating, so the wires are securely connected. Protected.

  The return type circuit breaker includes a fixed contact piece and a movable contact piece that comes into contact with and separates from the fixed contact piece due to thermal influence, and the movable contact piece is formed of bimetal. Good. The non-return type circuit breaker may be a fuse.

  As described above, as the return type circuit breaker used in the wire protection circuit and the wire protection method according to the present invention, the movable contact piece made of bimetal can be illustrated as a non-return type circuit breaker. Can be exemplified by a fuse. By adopting such a circuit breaker, a motor drive circuit can be configured at a low cost with a simple configuration.

  According to the electric wire protection circuit and the electric wire protection method of the present invention, since the circuit breaker includes the reset circuit breaker, the minimum operating current value of the reset circuit breaker included in the circuit breaker is set to the motor rating. What is necessary is just to set more than an electric current value, and, thereby, the allowable electric current value of an electric wire can be set below in a motor lock electric current value. Therefore, it becomes possible to make the diameter of an electric wire smaller than before, and the electric wire cost and electric wire weight can be reduced more than before.

It is a circuit diagram of an electric wire protection circuit (motor drive circuit) concerning a first embodiment of the present invention. It is a figure for demonstrating the characteristic of the circuit breaker and electric wire with which the electric wire protection circuit which concerns on 1st embodiment of this invention shown in FIG. 1 is provided. It is the schematic for demonstrating the structure of the circuit breaker with which the electric wire protection circuit which concerns on 1st embodiment of this invention shown in FIG. 1 is provided. It is a circuit diagram of the electric wire protection circuit (motor drive circuit) which concerns on 2nd embodiment of this invention. It is a figure for demonstrating the characteristic of the circuit breaker, electric wire, and fuse which comprise the electric wire protection circuit which concerns on 2nd embodiment of this invention shown in FIG. It is an example of the circuit diagram which applied this invention to the power window apparatus for vehicles. It is a circuit diagram of the conventional electric wire protection circuit (motor drive circuit). It is a figure for demonstrating the characteristic of the fuse with which the conventional electric wire protection circuit shown in FIG. 7 is equipped, and an electric wire.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram of an electric wire protection circuit (motor drive circuit) 10 according to a first embodiment of the present invention. FIG. 2 is a diagram for explaining the characteristics of a circuit breaker 161 and an electric wire 18 which will be described later constituting the electric wire protection circuit 10. Specifically, the curve C1 showing the relationship between the magnitude of the current flowing through the circuit breaker 161 (motor driving circuit) and the time until the circuit breaker 161 operates, and the magnitude of the current flowing through the electric wire 18 (motor driving circuit) A curve C2 showing the relationship between the time until the electric wire 18 burns out (the coating material melts and smokes due to the heat generated by the core wire) is shown together with the rated current value Ir and the motor lock current value If of the motor 14 used. FIG.

  The electric wire protection circuit 10 according to the present embodiment interrupts the circuit when an overcurrent is applied to the circuit in order to protect the electric wire 18 that connects the power source 12 and the motor 14 (regardless of type) and the electric wire 18. Circuit interrupting means 16 for performing the operation. The circuit breaker 16 includes a circuit breaker 161 that is a circuit breaker.

  The circuit breaker 161 is a return type circuit breaker that can return to the state before the operation even if it is once activated. The circuit breaker 161 has a characteristic represented by a curve C1 shown in FIG. Specifically, the minimum operating current value Ib of the circuit breaker 161 (refers to the minimum current value at which the circuit breaker operates). When a current less than this minimum operating current value is energized, the circuit breaker operates. The same applies hereinafter) is set to be larger than the rated current value Ir of the motor 14. Further, as can be seen from the relationship between the curve C1 and the curve C2, the time until the circuit breaker 161 is activated when a predetermined current (a current larger than the minimum operating current value Ib) flows in the motor drive circuit. The time until the electric wire 18 burns out is set to be shorter. That is, the circuit breaker 161 is set so as not to operate below the rated current value of the motor 14 and to prevent the electric current of a predetermined magnitude from being applied for a predetermined time in order to protect the electric wire 18. Yes.

  In this embodiment, since such a return type circuit breaker is used, it is not necessary to set the minimum operating current value Ib of the circuit breaker 161 to be equal to or higher than the motor lock current value If. This is because even if the motor 14 is locked for some reason, a motor lock current flows in the wire protection circuit 10 and the circuit breaker 161 is activated, it can be immediately restored without being replaced (circuit breaker). When a non-recoverable circuit breaker such as a fuse is used, replacement is required every time the motor 14 is locked. Therefore, the minimum operating current value of the circuit breaker must be greater than or equal to the motor lock current value. is there.).

  As the circuit breaker 161, for example, a bimetal circuit breaker as shown in FIG. 3 can be applied. That is, it consists of a fixed contact piece 161b housed in the case body 161a and a movable contact piece 161c made of bimetal. Examples of the material of the bimetal constituting the movable contact piece 161c include those using Cu—Ni on the high temperature expansion side and Ni—Fe on the low temperature expansion side, but are not particularly limited. Moreover, as a bimetal to apply, a direct-heating type bimetal may be sufficient and an indirectly heated bimetal may be sufficient.

  Since the electric wire 18 is protected by the circuit breaker 161, as described above, the time until the circuit breaker 161 is activated when a current of a predetermined magnitude flows in the motor drive circuit is activated. The allowable current value Ic (which means a current value that does not cause the wire to burn out due to a temperature rise (refer to the Japan Electric Wire Manufacturers Association Standard (JCS)). A value smaller than the lock current value If is selected.

  The reason why the electric wire 18 can be selected is that the circuit breaker 161 included in the circuit breaker 16 is a return type circuit breaker. In other words, as described above, if the return type circuit breaker is used, it is not necessary to replace the circuit breaker. Therefore, it is not necessary to set the minimum operating current value Ib of the circuit breaker 161 to be equal to or higher than the motor lock current If. . On the other hand, since it is sufficient for the electric wire 18 to be prevented from being burned out by the circuit breaker 161, if the current value at which the circuit breaker 161 operates can be reduced, the allowable current value Ic of the electric wire 18 can be reduced accordingly. Therefore, the allowable current value Ic of the electric wire 18 can be set to be equal to or less than the motor lock current value If.

  Therefore, for example, compared with a wire protection circuit where the minimum operating current value of the circuit breaker must be equal to or greater than the motor lock current value, as in the prior art using only a fuse that is a non-recoverable circuit breaker as a circuit breaker In addition, the allowable current value Ic of the electric wire 18 can be reduced, that is, the diameter of the electric wire 18 (the diameter of the core wire) can be reduced. Therefore, the electric wire protection circuit 10 according to the present embodiment leads to a reduction in the cost of the electric wire 18 and a reduction in the weight of the electric wire 18.

  Next, a second embodiment of the present invention will be described. The wire protection circuit 20 according to the second embodiment is different from the first embodiment in that the circuit breaker means 26 includes a fuse 261 in addition to the circuit breaker 161, as shown in the circuit diagram of FIG. Therefore, about the same structure as 1st embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted. FIG. 5 is a diagram for explaining the characteristics of the fuse 261 in addition to the characteristics (curve C1 and curve C2) of the circuit breaker 161 and the electric wire 18 constituting the electric wire protection circuit 20. Specifically, a curve showing the relationship between the magnitude of the current flowing through the fuse 261 (motor drive circuit) and the time until the fuse 261 is activated (blown) is shown as the characteristics of the circuit breaker 161 and the electric wire 18, and the motor used. It is the figure shown together with the rated current value Ir of 14 and the motor lock current value If. It should be noted that the characteristics of fuses vary greatly depending on the temperature of the environment in which they are used, so it is necessary to take into account changes in characteristics in environments where fusing is most likely to occur and environments where fusing is most difficult. Therefore, in FIG. 5, the characteristic in the environment that is most likely to be blown is indicated by a curve C3min, and the characteristic in an environment that is most likely to be blown is indicated by a curve C3max.

  The circuit breaker means 26 is provided with a fuse 261 which is a non-recoverable circuit breaker that cannot be restored once activated (fused) on the upstream side of the circuit breaker 161 which is the above-described reset circuit breaker. The fuse 261 plays a role of interrupting the circuit in place of the circuit breaker 161 when the circuit breaker 161 breaks down (for example, malfunction due to the fixed contact piece 161b and the movable contact piece 161c being fixed).

  Therefore, as shown in FIG. 5, the fuse 261 needs to have the following characteristics. That is, when a current of a predetermined magnitude flows in the motor drive circuit, the time until the fuse 261 operates is such that when the circuit breaker 161 can operate normally, the circuit breaker 161 should be operated with priority. The time until the circuit breaker 161 is activated (curve C1) is set to be longer. This may be set in consideration of the characteristic (curve C3min) when the fuse 261 is most easily blown. Further, when a current of a predetermined magnitude flows in the motor drive circuit, the time until the fuse 261 operates is the time until the wire 18 is burned out in order to protect the wire 18 when the circuit breaker 161 breaks down. It is set to be shorter than the time (curve C2). This may be set in consideration of the characteristic (curve C3max) when the fuse 261 is most difficult to blow.

  As described above, in the second embodiment, the circuit breaker 26 is added to the circuit breaker 161 serving as the reset circuit breaker, and the fuse 261 serving as the non-return circuit breaker that preferentially operates the circuit breaker 161 is provided. It has been. For this reason, the circuit breaker 161 that can be immediately restored in normal operation is preferentially activated. On the other hand, when the circuit breaker 161 is not activated due to a failure or the like, the circuit is interrupted by the operation of the fuse 261. Therefore, the electric wire 18 is surely protected.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

  For example, in the above-described embodiment, the use of the bimetal circuit breaker 161 as the reset circuit breaker has been described. However, other circuit breakers may be used as long as they are circuit breakers that do not need to be replaced once they are activated. It may be used. For example, an electromagnetic circuit breaker, a PTC, or a semiconductor switch may be configured to detect and control a circuit current. Similarly, although it has been described that the fuse 261 is used as a non-return type circuit breaker, other non-return type circuit breakers may be used.

  Further, in the above embodiment, it has been described that only the fuse 261 having a particularly large change in characteristics due to a change in use environment is selected in consideration of the change in characteristics in the use environment. However, other components such as a circuit breaker are used. If 161 or the like is selected in consideration of changes in characteristics due to changes in the use environment, the reliability of the wire protection circuits 10 and 20 can be further improved.

  Hereinafter, the present invention will be described using examples. FIG. 6 is an example of a circuit diagram in which the present invention is applied to a power window device 30 for a vehicle.

  As shown in FIG. 6, the power window device 30 includes a control unit 32 that controls the moving direction (opening direction or closing direction) of the window glass, and an electric wire protection unit 34 for protecting the electric wires 18 constituting the circuit. Prepare.

  The control unit 32 is a unit that switches between forward rotation (rotation that moves the window glass in the opening direction) and reverse rotation (rotation that moves the window glass in the closing direction) of the motor 14 that drives the window glass (not shown). And a forward relay 32a and a reverse relay 32b. When the switch 38 is operated in the direction to open the window glass, the forward relay 32a is turned on by the microcomputer 321, and the current flows in the direction of the arrow in the figure. As a result, the motor 14 rotates forward, and the window glass moves in the opening direction. On the other hand, when the switch 38 is operated in the direction in which the window glass is closed, the reverse relay 32b is turned on by the microcomputer 321, and the current flows in the direction opposite to the arrow in the figure. As a result, the motor 14 reverses and the window glass moves in the closing direction.

  The electric wire protection unit 34 has a configuration corresponding to the circuit breaker means 16 and 26 in the above embodiment, and includes a circuit breaker 161 and a fuse 261.

  As described in the first and second embodiments, the circuit breaker 161 is set such that the minimum operating current value is larger than the rated current value of the motor 14. Further, when a predetermined current flows through the motor drive circuit, the time until the circuit breaker 161 operates is set to be shorter than the time until the wire 18 burns out.

  As described in the second embodiment, the fuse 261 has a time until the fuse 261 is activated when a current of a predetermined magnitude flows in the motor drive circuit from the time until the circuit breaker 161 is activated. It is set to be longer and shorter than the time until the electric wire 18 burns out.

  If the power window device 30 is configured in this way, since the circuit breaker 161 that is a return type circuit breaker is used, the allowable current value of the electric wire 18 is smaller than the motor lock current that flows when the motor 14 is locked, That is, the diameter of the electric wire 18 can be reduced, leading to cost reduction and weight reduction of the electric wire 18.

  In addition, when a current of a magnitude that may cause the electric wire 18 to burn is energized, the circuit breaker 161 that can be immediately restored in normal operation is preferentially activated, but the circuit breaker 161 is activated due to a failure or the like. If not, the fuse 261 is activated. That is, the circuit breaker 161, which is a return type circuit breaker, is preferentially operated to maintain good maintainability, and in the unlikely event, the fuse 261 is activated, so that the protection circuit for the electric wire 18 is high. Reliable.

10. Electric wire protection circuit (first embodiment)
12 power supply 14 motor 16 circuit interruption means 161 circuit breaker 161b fixed contact piece 161c movable contact piece 18 electric wire 20 electric wire protection circuit (second embodiment)
26 Circuit breaker 261 Fuse Ir Rated current value of motor If Motor lock current value Ic Allowable current value of wire Ib Minimum operating current value of circuit breaker

Claims (8)

  In a wire protection circuit in which a circuit breaker is provided in a motor drive circuit in which a power source and a motor are connected by an electric wire, the circuit breaker includes a reset circuit breaker that can be restored even if it is once activated. The minimum operating current value of the reset type circuit breaker is set to be larger than the rated current value of the motor, and the reset type when a current larger than the minimum operating current value flows in the motor drive circuit. The time until the circuit breaker is activated is set to be shorter than the time until the wire is burned out, and the allowable current value of the wire is set in the motor drive circuit when the motor is locked. An electric wire protection circuit which is set to be smaller than a flowing motor lock current value.   The circuit interruption means further includes a non-reset type circuit breaker that cannot be reset once activated, and the non-reset type circuit cutoff when a current larger than the minimum operating current value flows in the motor drive circuit. The time until the breaker is activated is set to be longer than the time until the return-type circuit breaker is activated and shorter than the time until the wire burns out. The electric wire protection circuit according to 1.   The return-type circuit breaker includes a fixed contact piece and a movable contact piece that comes into contact with and separates from the fixed contact piece due to thermal influence, and the movable contact piece is formed of bimetal. The electric wire protection circuit according to claim 1 or 2.   The electric wire protection circuit according to any one of claims 1 to 3, wherein the non-return type circuit breaker is a fuse.   A method of protecting a wire in a motor drive circuit in which a circuit drive means is provided in a motor drive circuit in which a power source and a motor are connected by an electric wire, wherein the circuit cut-off means can be returned even if it is once activated. The minimum operating current value of the reset circuit breaker is set to be larger than the rated current value of the motor, and a current larger than the minimum operating current value flows in the motor drive circuit. In this case, the time until the reset circuit breaker is activated is set to be shorter than the time until the wire burns out, and the allowable current value of the wire is set when the motor is locked. An electric wire protection method, wherein the electric wire is set to be smaller than a motor lock current value flowing through the motor drive circuit.   The circuit interruption means further includes a non-reset type circuit breaker that cannot be reset once activated, and the non-reset type circuit cutoff when a current larger than the minimum operating current value flows in the motor drive circuit. The time until the breaker is activated is set to be longer than the time until the return type circuit breaker is activated and shorter than the time until the wire is burned out. The electric wire protection method described.   The return-type circuit breaker includes a fixed contact piece and a movable contact piece that comes into contact with and separates from the fixed contact piece due to thermal influence, and the movable contact piece is formed of bimetal. The method for protecting an electric wire according to claim 6 or 7, wherein: The electric wire protection method according to claim 5, wherein the non-return type circuit breaker is a fuse.

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