JP2014102887A - Electromagnetic switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a contact point of an electromagnetic switch at a pre-stage of an electric starter motor (a motor) to be closed even in the case that a magnetic field generated by an electromagnetic solenoid is weak.SOLUTION: An electromagnetic switch comprises: a resistive element suppressing a current flowed from a battery to an electric starter motor for starting an engine; sub contact points including a fixed contact point and a movable contact point arranged in parallel to the resistive element; a solenoid coil generating a first magnetic field by energization from the battery; and a movable iron core surrounded by the solenoid coil. In the electromagnetic switch, the resistive element has a coil part arranged in a magnetic circuit of the solenoid coil and formed in a coil shape surrounding the movable iron core so as to generate a second magnetic field for making the movable contact point contact with the fixed contact point in the same direction as the first magnetic field, when a current flows.

Description

  The present invention relates to an electromagnetic switch having a built-in resistor for suppressing an energization current to a starting motor.

  In order to suppress the occurrence of an instantaneous power failure of an electrical component, an electromagnetic switch including a resistor for suppressing a current to be supplied when starting the starting motor is disclosed (for example, see Patent Document 1).

JP 2009-224315 A

  Due to the restriction of the heat generation amount or volume (the number of turns of the coil), the magnetic field generated by the electromagnetic solenoid is weak, and the contact of the electromagnetic switch disclosed in Patent Document 1 in the preceding stage of the starting motor (motor) may not be closed. .

  The electromagnetic switch according to claim 1 includes a resistor that suppresses a current flowing from a battery to a starting motor that starts an engine, a sub-contact that includes a fixed contact and a movable contact arranged in parallel to the resistor, and a battery. In an electromagnetic switch including a solenoid coil that generates a first magnetic field when energized from and a movable iron core surrounded by the solenoid coil, the resistor is disposed in the magnetic circuit of the solenoid coil, and when a current flows, a movable contact is formed. It has the coil part shape | molded by the coil shape surrounding a movable iron core so that the 2nd magnetic field for making it contact with a fixed contact may be produced in the same direction as a 1st magnetic field.

  According to the present invention, even when the magnetic field generated by the electromagnetic solenoid is weak, the contact of the electromagnetic switch in the previous stage of the starting motor (motor) can be closed.

It is sectional drawing of an electromagnetic switch. It is an electric circuit diagram of a starting motor system to which an electromagnetic switch is connected. It is a figure which shows the shape of the resistor of an electromagnetic switch. It is a time chart at the time of operation | movement of the starting motor system to which the electromagnetic switch in this Embodiment was connected. It is a figure which shows the relationship between the attractive force at the time of operation | movement of the sub contact of an electromagnetic switch, and a spring reaction force. It is a figure which shows the shape of the resistor of an electromagnetic switch. It is a figure which shows the shape of the resistor of an electromagnetic switch.

  Hereinafter, an electromagnetic switch according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of an electromagnetic switch 10 according to the present embodiment, and FIG. 2 is an electric circuit diagram of a starting motor system 1. As shown in FIG. 2, the starting motor system 1 includes a motor (starting motor) 2, a pinion 4, a shift lever 5, a main contact 7, a magnet switch 3, and the like. The motor 2 generates the rotational force necessary to start the engine. The pinion 4 transmits its rotational force to the engine side ring gear 6. The shift lever 5 pushes the pinion 4 toward the ring gear 6 so that the pinion 4 meshes with the ring gear 6. The main contact 7 controls energization to the motor 2 and the operation of the shift lever 5. The magnet switch 3 opens and closes the main contact 7 by energization.

  The electromagnetic switch 10 is inserted into a circuit from the battery 9 to the main contact 7 of the starter motor system 1 and includes a resistor 30, a sub contact 20, an electromagnetic solenoid 11, and the like. The resistor 30 suppresses the current flowing from the battery 9 to the motor 2. The sub-contact 20 includes fixed contacts 22a and 22b arranged in parallel to the resistor 30 and the movable contact 21. When the sub-contact 20 is in a closed state, the resistor 30 is short-circuited and the motor 2 is directly energized. . The electromagnetic solenoid 11 performs opening / closing control of the sub-contact 20.

  The electromagnetic solenoid 11 includes a coil case 18, a solenoid coil 12, and a movable iron core 16 and a fixed iron core 17 that are surrounded by the solenoid coil 12. The coil case 18 has an opening only on a surface that intersects one of the axial directions. The solenoid coil 12 is disposed inside the coil case 18 while being supported by a resin bobbin 13. The coil case 18, the movable iron core 16 and the fixed iron core 17 constitute a magnetic circuit 19. One end of the solenoid coil 12 is connected to an external terminal 14 connected to the control device 8. The other end of the solenoid coil 12 is connected to the fixed iron core 17. The fixed iron core 17 is connected to the ground circuit 15 via the coil case 18.

  The sub-contact 20 is disposed on the opposite side of the magnetic circuit 19 with the fixed iron core 17 interposed therebetween, and includes a movable contact 21, fixed contacts 22 a and 22 b, and a contact case 23. The movable contact 21 moves in synchronization with the movable iron core 16. The contact case 23 holds the fixed contacts 22a and 22b. The movable contact 21 is held at an initial position in a direction away from the fixed iron core 17 by a contact pressing spring 24. The movable iron core 16 is held at an initial position in a direction away from the fixed iron core 17 by a return spring 25.

  A first magnetic field generated by energization from the battery 9 to the solenoid coil 12 and a second magnetic field generated by the current flowing from the battery 9 to the motor 2 flowing through the resistor 30 are generated in the same direction. The fixed magnetic core 17 and the movable iron core 16 are magnetized by the first magnetic field and the second magnetic field, and the attractive force that attracts the movable iron core 16 toward the fixed iron core 17 overcomes the spring reaction force of the return spring 25. Therefore, the movable iron core 16 is sucked toward the fixed iron core 17. When the movable contact 21 that moves in synchronization with the movable iron core 16 contacts the fixed contacts 22a and 22b, the sub-contact 20 is closed. When the sub contact 20 is closed, the current flowing from the battery 9 flowing through the resistor 30 to the motor 2 is short-circuited via the sub contact 20, so that the suppression of the current flowing from the battery 9 to the motor 2 by the resistor 30 is released. Is done. Thereafter, when the current flowing from the battery 9 to the motor 2 is stopped and the solenoid coil 12 is de-energized, the movable contact 21 is returned to the initial position by the reaction force of the contact pressing spring 24 and is movable by the reaction force of the return spring 25. The sub-contact 20 is opened by returning the iron core 16 to the initial position.

  FIG. 3 shows the shape of the resistor 30 of the electromagnetic switch 10 in the present embodiment. As shown in FIG. 1, the resistor 30 is disposed in an air gap (space) surrounded by the outer periphery of the solenoid coil 12 and the coil case 18 in the magnetic circuit 19 of the electromagnetic solenoid 11. The periphery of the resistor 30 is covered with a tubular insulating member. The air gap and the insulating member constitute an insulating layer. The resistor 30 has a coil portion 31 formed in a coil shape, and surrounds the solenoid coil 12 and the movable iron core 16 via the insulating layer. Both ends 32a and 32b of the resistor 30 are connected to fixed contacts 22a and 22b, respectively. The direction of the second magnetic field generated by the current flowing through the coil portion 31 of the resistor 30 when the resistor 30 is energized coincides with the direction of the first magnetic field generated by the energization of the solenoid coil 12.

In order to make the heat transfer amount from the resistor 30 to the coil case 18 larger than the heat transfer amount from the resistor 30 to the solenoid coil 12, the resistor 30 is disposed closer to the coil case 18 in the air gap. The By arranging in this way, the solenoid coil 12 and its peripheral parts (for example, the bobbin 13) are not easily damaged by heat. Further, when the sub-contact 20 cannot be closed and a large current for driving the motor 2 is continuously supplied to the resistor 30, the electromagnetic solenoid 11 may become inoperable due to the heat generated by the resistor 30. . In order to prevent this, the time T _R [s] from the start of energization of the resistor 30 to the fusing and the time during which any of the components of the electromagnetic solenoid 11 excluding the resistor 30 are subjected to thermal damage. The resistor 30 is set so that T _S [s] satisfies T _R <T _S. The electrical resistance ρ [Ωm], the volume specific heat c [J / (m ³ K)], the cross-sectional area A [m ² ], and the heat dissipation amount of the heat generation amount of the resistor 30 through which the average conduction current I [A] flows. The heat dissipation rate α indicating the ratio, the temperature θ ₀ [° C.] before energization, the fusing temperature θ _R [° C.], and the time T _R [s] from the start of energization of the resistor 30 to fusing are expressed as follows: Fulfill.
{Ρ × I ² × (1−α) / (c × A ² )} × T _R = θ _R −θ ₀ (1)

An example will be described. It is assumed that the average current I = 200 [A] flows through the resistor 30 and the components around the solenoid coil 12 are thermally damaged at T _S = 5 [s]. In this case, when the resistor 30 is formed of a steel wire, the resistor 30 is blown when the temperature of the resistor 30 reaches the fusing temperature θ _R = 1500 [° C.]. According to Formula (1), if the wire diameter of the steel wire constituting the resistor 30 is 3.1 [mm], the resistor 30 is blown before the electromagnetic solenoid 11 becomes inoperable during continuous energization, and therefore This means that the energization is cut off.

  In other words, even if the resistor 30 is energized for a long time, the material and disconnection of the resistor 30 are such that the resistor 30 is melted before the solenoid coil 12 and the components around the solenoid coil 12 are thermally damaged. The area is set. Even when the resistor 30 is melted by energizing the resistor 30 for a long time, the electromagnetic switch 10 holds a circuit other than the resistor 30, and the first generated by energization from the battery 9 to the solenoid coil 12. The movable contact 21 can be brought into contact with the fixed contacts 22a and 22b by the magnetic field. Therefore, since the current from the battery 9 flows to the motor 2 through the closed sub contact 20, the engine can be started.

  In the starting motor system 1 to which the electromagnetic switch 10 having the above configuration is connected, the operation of the motor 2 at the time of starting the engine will be described. When an engine start request is generated, the control device 8 energizes the magnet switch 3 and the main contact 7 is closed. By closing the main contact 7, the pinion 4 is pushed out and meshed with the ring gear 6, and energization from the battery 9 to the motor 2 via the resistor 30 is started. At this time, the energization current to the motor 2 is limited by the resistor 30, and the motor 2 starts cranking the engine while rotating at a low speed.

  After the motor 2 starts rotating by closing the main contact 7 at time T1, the control device 8 starts energization by the battery 9 to the solenoid coil 12 of the electromagnetic switch 10 at time T2 after a predetermined timing elapses. The contact 20 is closed. When the sub contact 20 is closed, a circuit in which the resistor 30 is short-circuited is formed, so that the voltage of the battery 9 is fully applied to the motor 2 and the motor 2 starts cranking the engine at high speed. FIG. 4 is a time chart showing temporal changes in the open / closed states of the main contact 7 and the sub contact 20, the voltage of the battery 9, and the current flowing through the motor 2 at this time.

  As shown in FIG. 4, the time T1 described above indicates the time when the main contact of the starting motor system 1 is closed, and the time T2 described above indicates the time when the sub contact 20 is closed. The voltage of the battery 9 at the time T1 when the engine is started due to the closing of the main contact of the starting motor system 1 remains at the voltage V1 by suppressing the current to the motor 2 by the resistor 30. That is, the current suppression to the motor 2 by the resistor 30 prevents the voltage drop of the battery 9 to a voltage lower than the voltage V1. At time T2, the motor 2 rotates at a low speed, and the voltage of the battery 9 remains at the voltage V2 by using the back electromotive voltage generated by the rotation of the motor 2. That is, the counter electromotive voltage generated by the rotation of the motor 2 prevents the voltage drop of the battery 9 to a voltage lower than the voltage V2. Therefore, it is possible to suppress the occurrence of an instantaneous power failure of the electrical component.

  FIG. 5 shows the attractive force acting in the direction toward the fixed iron core 17 with respect to the movable iron core 16 when a voltage is applied to the solenoid coil 12 of the electromagnetic switch 10 to operate the sub-contact 20, and the movable iron core 16. The relationship with the spring reaction force pressed in the direction away from the fixed iron core 17 is shown. The spring reaction force that presses the movable iron core 16 in the direction away from the fixed iron core 17 is the resultant force of the contact pushing spring 24 and the return spring 25. The return spring 25 always applies a reaction force to the movable iron core 16. The contact pressing spring 24 starts to bend when the movable contact 21 moving in synchronization with the movable iron core 16 contacts the fixed contacts 22a and 22b. Therefore, the contact pressing spring 24 acts as a spring that generates a spring reaction force after the sub-contact 20 is closed.

  The suction force with respect to the movable iron core 16 required for closing the sub-contact 20 as the movable iron core 16 is driven and moved is inversely proportional to the amount of gap between the movable iron core 16 and the fixed iron core 17. Therefore, the strength of the first magnetic field and the second magnetic field necessary for closing the sub contact 20 as the movable iron core 16 is driven and moved varies depending on the position of the movable iron core 16. Is largest when is in the initial position.

  Before the movable iron core 16 starts moving from the initial position, the current from the battery 9 to the motor 2 flows through the resistor 30, so that the movable iron core 16 that requires the greatest magnetic field strength is used. From the start of movement until the sub contact 20 is closed, the second magnetic field generated by the current flowing through the resistor 30 can be used to generate an attractive force with respect to the movable iron core 16. Until the sub contact 20 is closed, in the conventional electromagnetic switch, the movable iron core is driven only by the first magnetic field generated by the solenoid coil. In comparison with this, in the electromagnetic switch according to the present embodiment, the first magnetic field that generates an attractive force to the movable iron core 16 is generated by the solenoid coil 12 until the sub contact 20 is closed. The voltage can be lowered. Therefore, the range of the battery voltage at which the sub contact 20 operates can be expanded to the low voltage side, and the reliability of the starting motor system 1 can be improved.

  In the conventional electromagnetic solenoid, the sub-contact is closed by attracting the movable iron core toward the fixed iron core by a magnetic field generated when a current flows through the solenoid coil. The suction force for driving the movable iron core is inversely proportional to the amount of gap between the movable iron core and the fixed iron core. For this reason, the strength of the magnetic field required to drive the movable iron core in the initial state and close the sub-contact is greater than the strength of the magnetic field required to maintain the closed state of the sub-contact. The coil specifications of the electromagnetic solenoid are determined depending on the magnitude of the magnetic field that can be attracted by the movable iron core when the sub-contact is in the open state.

  In order to increase the reliability of the electromagnetic switch by operating a conventional electromagnetic solenoid at a low voltage, the magnetic field generated by the solenoid coil is increased by reducing the resistance value of the solenoid coil and increasing the current flowing through the solenoid coil. It is possible to do. When the current flowing through the solenoid coil increases, the amount of heat generation increases, causing problems such as an increase in cost for countermeasures against heat generation and an increase in power consumption. Increasing the number of turns of the solenoid coil can also increase the magnetic field generated by the solenoid coil. As the number of turns of the solenoid coil increases, problems such as an increase in cost due to an increase in the amount of material used for the solenoid coil and an increase in the size of the electromagnetic solenoid due to an increase in volume (weight increase) of the solenoid coil become a problem.

  In the conventional electromagnetic switch, the electromagnetic solenoid generates a magnetic field and opens / closes the sub-contact in a state where the voltage of the battery drops due to the current flowing from the battery to the motor via the resistor. If the voltage drop of the battery during energization of the motor is large due to deterioration of the battery or the like, the magnetic field generated by the electromagnetic solenoid may weaken and the sub-contact cannot be closed. In this case, if the state where the current flowing from the battery to the motor is continuously limited by the resistor continues, the engine start time becomes longer.

  In a state where the sub contact cannot be closed due to the deterioration of the battery, if a large current that drives the motor flows through the resistor of the conventional electromagnetic switch for a long time, the resistor may melt or Thermal damage may occur to parts such as electromagnetic solenoids or bobbins. In such a case, the energization path from the battery to the motor is lost, and there is a possibility that the engine cannot be started.

  The electromagnetic switch 10 in the present embodiment includes a resistor 30, a sub contact 20, a solenoid coil 12, and a movable iron core 16. The resistor 30 suppresses the current flowing from the battery 9 to the motor 2 that starts the engine. The sub-contact 20 includes fixed contacts 22 a and 22 b and a movable contact 21 arranged in parallel with the resistor 30. The solenoid coil 12 generates a first magnetic field when energized from the battery 9. The movable iron core 16 is surrounded by the solenoid coil 12. The resistor 30 has a coil portion 31 and is disposed in the magnetic circuit 19 of the solenoid coil 12. The coil portion 31 of the resistor 30 surrounds the movable iron core 16 so as to generate a second magnetic field for bringing the movable contact 21 into contact with the fixed contacts 22a and 22b in the same direction as the first magnetic field when a current flows. Molded into a coil.

  Since the electromagnetic switch 10 according to the present embodiment has the above-described configuration, the resistor 30 built in the electromagnetic switch 10 is started when the sub-contact 20 that requires the largest magnetic field because the electromagnetic solenoid 11 is in the initial position starts closing. The second magnetic field generated by the motor current flowing through can be used as an attractive force for the movable iron core 16. Since the first magnetic field that needs to be generated by the solenoid coil 12 can be small, the minimum operating voltage of the electromagnetic solenoid 11 can be lowered without increasing the weight and cost, and the reliability of the electromagnetic switch 11 when starting the engine and Safety can be improved.

(Modification)
(1) The attractive force generated with respect to the movable iron core 16 by the second magnetic field generated by the motor current flowing through the resistor 30 does not exceed the spring reaction force, which is the resultant force of the contact pressing spring 25 and the return spring 24, and the movable contact. It is preferable that 21 is smaller than the suction force required to contact the fixed contacts 22a and 22b and the sub-contact 20 is closed. That is, when the main contact 7 closes at time T1 and current begins to flow through the resistor 30, the sub contact 20 does not close immediately, but, as shown in FIG. 4, the sub contact 20 opens at time T2 after time T1. Close is preferred. In order to close the sub contact 20, the resistor 30 is set so that energization control from the battery 9 to the solenoid coil 12 by the control device 8 is required. Thereby, the time from the time T1 when the energization to the starting motor system 1 from the battery 9 is started to the time T2 when the energization to the resistor 30 is short-circuited can be arbitrarily set without being influenced by the specification of the resistor 30. It becomes.

(2) FIG. 6 shows a modification of the resistor 30. The coil portion 31 of the resistor 30 generates an attractive force with respect to the movable contact 16, and a single circular coil together with the boundary portions 34 a and 34 b between the both ends 32 a and 32 b of the resistor 30 and the coil portion 31. It is formed into a shape. The single annular shape of the coil portion 31 is less than 360 degrees by the thickness of the tubular end portions 32 a and 32 b of the resistor 30. The resistor 30 is based on the electrical resistivity ρ [Ωm] of the resistor 30 determined by the material of the resistor 30, the total length L [m] of the resistor 30, and the cross-sectional area A [m ² ] of the resistor 30. The required resistance value R [Ω] of the resistor 30 is set by the equation (2).
R = ρ × (L / A) (2)

For example, the required resistance value R of the resistor 30 is R = 10 [mΩ], and the electrical resistivity ρ = 15.4 × 10 ⁻⁷ [Ωm] when the resistor 30 is formed of a steel wire. At this time, the total length L [m] of the resistor 30 and the cross-sectional area A [m ² ] of the resistor 30 are determined by the equation (2). In this way, the material and the cross-sectional area of the resistor 30 are set so that a necessary resistance value can be obtained in the resistor 30.

  In the resistor 30 shown in FIG. 3, in order to connect both ends 32 a and 32 b of the resistor 30 and the sub-contact 20, the end portion 32 b of the resistor 30 is multiplexed with the coil portion 31 of the resistor 30. Out of the annular ring, the annular part including the boundary part 34a between the end 32a of the resistor 30 and the coil part 31 protrudes outside. That is, the ring including the boundary portion 34b between the end 32b of the resistor 30 and the coil portion 31 is different from the ring including the boundary portion 34a. In the resistor 30 shown in FIG. 6, since the annular shape of the coil portion 31 of the resistor 30 is single, a circular shape in which the coil portion 31 of the resistor 30 has one of both end portions 32 a and 32 b of the resistor 30. There is no need to pass through the outside or inside of the ring shape. Therefore, the outer diameter of the resistor 30 can be reduced, and as a result, the size of the electromagnetic switch 10 can be reduced.

  The attractive force acting on the movable iron core 16 is determined by the product nI of the number of coil turns n and the current I. For example, when the number of turns n of the solenoid coil 12 is 200 and the current I energized to the solenoid coil 12 is 10 [A], the attractive force acting on the movable iron core 16 overcomes the spring reaction force of the return spring 25 to move the movable iron core 16. Is moved toward the fixed iron core 17. That is, the movable iron core 16 moves toward the fixed iron core 17 when the product nI = 2000 of the number of turns n = 200 of the solenoid coil 12 and the current I = 10 [A]. It is assumed that a large current I = 500 [A] necessary for driving the motor 2 flows through the resistor 30. Even when the number of turns n of the resistor 30 is 1, the product nI = 500 of the number of turns n = 1 of the resistor 30 and the current I = 500 [A]. 25% of the product nI = 2000 of the number of coil turns n required to move toward the fixed core 17 and the current I can be generated.

(3) FIG. 7 shows another modification of the resistor 30. The coil portion 31 of the resistor 30 has a folded portion 33 and two partial coils before and after the folded portion 33. The directions in which the two partial coils are wound are opposite to each other, and the number of turns of the two partial coils is different. When current flows through the coil portion 31 of the resistor 30 when the motor is energized, the strength of the magnetic field generated by each of the two partial coils is proportional to the number of turns of each of the two partial coils. Since the direction of the magnetic field generated by one of the two partial coils is opposite to the direction of the magnetic field generated by the other of the two partial coils, the strength of the magnetic field generated by each of the two partial coils. Cancel each other. By changing the difference in the number of turns of the two partial coils, the strength of the second magnetic field can be adjusted without changing the resistance value.

  The above-described embodiments and modifications may be combined.

1: Starter motor system 2: Motor 3: Magnet switch 4: Pinion 5: Shift lever 6: Ring gear 7: Main contact 8: Controller 9: Battery 10: Electromagnetic switch 11: Electromagnetic solenoid 12: Solenoid coil 13: Bobbin 14: External terminal 15: Earth circuit 16: Movable iron core 17: Fixed iron core 18: Coil case 19: Magnetic circuit 20: Sub contact 21: Movable contact 22: Fixed contact 23: Contact case 24: Contact push spring 25: Return spring 30: Resistance Body 31: Coil part 32: End part 33: Folding part 34: Boundary part

Claims (6)

A resistor that suppresses the current flowing from the battery to the starting motor that starts the engine;
A sub-contact including a fixed contact and a movable contact arranged in parallel to the resistor;
A solenoid coil that generates a first magnetic field by energization from the battery;
In an electromagnetic switch comprising a movable iron core surrounded by the solenoid coil,
The resistor is disposed in a magnetic circuit of the solenoid coil, and generates a second magnetic field for bringing the movable contact into contact with the fixed contact in the same direction as the first magnetic field when the current flows. Thus, the electromagnetic switch characterized by having the coil part shape | molded by the coil shape surrounding the said movable iron core. The electromagnetic switch according to claim 1,
An electromagnetic switch characterized in that an attractive force generated with respect to the movable iron core by the second magnetic field is smaller than an attractive force required for the movable contact to contact the fixed contact. The electromagnetic switch according to claim 2,
Further comprising an insulating layer formed of an insulating member and an air gap on the outer periphery of the solenoid coil;
The electromagnetic switch according to claim 1, wherein the resistor surrounds the solenoid coil via the insulating layer. The electromagnetic switch according to claim 3,
The electromagnetic switch is characterized in that a material and a cross-sectional area of the resistor are set so that, when energized, the solenoid coil and parts around the solenoid coil are blown before thermal damage occurs. The electromagnetic switch according to any one of claims 1 to 4,
The resistor includes the coil part and an end part,
The electromagnetic switch according to claim 1, wherein the coil portion is formed into a single annular coil shape together with a boundary portion between the end portion and the coil portion. The electromagnetic switch according to any one of claims 1 to 4,
The resistor has two partial coils,
The directions in which the two partial coils are wound are opposite to each other,
The electromagnetic switch according to claim 1, wherein the strength of the second magnetic field is determined according to a difference in the number of turns of the two partial coils.

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