Electromagnetic relay

Abstract

Electromagnetic relay comprising: a control circuit (41) designed to control a current in a winding (32), characterized by a fixed connection (11, 12); a fixed contact (14, 15) connected to the fixed terminal (11, 12); a movable contact piece (13) configured to move in an opening direction (Z2) and a closing direction (Z1) with respect to the fixed terminal (11, 12); a movable contact (16, 17) connected to the movable contact piece (13) and arranged to face the fixed contact (14, 15); wherein the winding (32) is designed to generate an electromagnetic force to move the movable contact piece (13); wherein the drive circuit (41) is designed to increase the current at a first increase rate in a first period (T1 to T2), comprising a period from a start time when the current in the winding (32) begins to flow until before a contact time at which the movable contact (16, 17) comes into contact with the fixed contact (14, 15), and with a second increase rate that is greater than the first increase rate, in a second period (T2 to T3) that includes a period after the time of contact.

Description

Area

[0001] The present invention relates to an electromagnetic relay. background

[0002] An electromagnetic relay is known that reduces power consumption during contact holding by reducing the current in the winding after the contact makes contact. For example, in the electromagnetic relay disclosed in JP H01-132108A, the winding voltage is controlled by a PWM (pulse width modulation) controller. More specifically, the duty cycle of the winding voltage is set to 100% from the start of contact driving until the contact makes contact. The duty cycle is reduced during contact holding. This reduces the current in the winding during contact holding. Furthermore, JP S53-120751U discloses an electromagnetic relay comprising a coil, a power supply, and a power supply for driving. Summary

[0003] In the electromagnetic relay described above, a large current flows in the coil before the contact makes contact. Therefore, the impact energy of the contact becomes large, and the impact at the time the contact makes contact becomes large. An object of the present disclosure is to reduce the impact at the time the contact makes contact in the electromagnetic relay.

[0004] An electromagnetic relay according to one aspect includes a fixed terminal, a fixed contact, a movable contact piece, a movable contact, a winding, and a drive circuit. The fixed contact is connected to the fixed terminal. The movable contact piece is configured to move in an opening direction and a closing direction with respect to the fixed terminal. The movable contact is connected to the movable contact piece and is arranged to oppose the fixed contact. The winding generates an electromagnetic force to move the movable contact piece. The drive circuit controls a current in the winding. The drive circuit increases the current at a first increase rate in a first period of time.The first period includes a period from a starting time when the current begins to flow in the winding until before a contact time at which the movable contact comes into contact with the fixed contact. The drive circuit increases the current in a second period at a second increase rate that is greater than the first increase rate. The second period includes a period after the contact time.

[0005] In the electromagnetic relay according to this aspect, the current in the winding flows at a smaller increase rate in the first period than in the second period. Therefore, the impact energy of the contact is reduced. This reduces contact impact. Furthermore, the current in the winding flows at a larger increase rate in the second period than in the first period. Therefore, the pressing force of the movable contact against the fixed contact increases. This further reduces contact impact.

[0006] The drive circuit can maintain the current in the winding at a higher current value in the third period after the second period than the current value during the first period. In this case, the contact impact can be quickly converged, and the contacts can be brought into stable contact with each other.

[0007] In the fourth period after the third period, the control circuit can reduce the current in the winding to a value lower than the current value in the third period. In this case, the power consumption is reduced while the contact is maintained.

[0008] The first period may be longer than the second period. In this case, the impact energy of the contact may be reduced because the current in the winding is increased slowly.

[0009] The electromagnetic relay may further include a contact voltage detection unit. The contact voltage detection unit can detect a voltage across the movable contact and the fixed contact. The control circuit can detect the contact timing based on the voltage detected by the contact voltage detection unit. In this case, the contact opening of the contact can be accurately detected based on the voltage across the movable contact.

[0010] The drive circuit can start the second period based on the voltage detected by the contact voltage detection unit. In this case, it is possible to start the second period appropriately according to the contact timing of the contact.

[0011] The electromagnetic relay may further include a movable device and a movable iron core. The movable device may be connected to the movable contact piece. The movable iron core may be connected to the movable device and may be moved by the electromagnetic force generated by the winding. The first period may comprise a period from the start time to a time when the movable iron core begins to move. In this case, the impact energy of the contact may be reduced by gradually increasing the current in the winding until the movable iron core begins to move. Short description of the drawing Fig. 1 is a side sectional view showing the electromagnetic relay according to an embodiment in an open state. Fig. 2 is a side sectional view showing the electromagnetic relay in a closed state. Fig. 3 is a schematic diagram showing the structure of a control circuit. Fig. 4A to 4D show a timing chart explaining the control of the electromagnetic relay by the drive circuit. Fig. 5 is a side sectional view showing the electromagnetic relay according to a modification. Detailed description

[0012] An electromagnetic relay 1 according to an embodiment will be described below with reference to the drawings. Fig. 1 is a side sectional view showing the electromagnetic relay 1 according to an embodiment. As shown in Fig. 1, the electromagnetic relay 1 includes a contact device 2, a housing 3 and a drive device 4.

[0013] In the following description, the directions up, down, left and right mean the directions up, down, left and right in Fig. 1. More specifically, the direction from the drive device 4 to the contact device 2 is defined as the upward direction. The direction from the contact device 2 to the drive device 4 is defined as the downward direction. Fig. 1, the direction that intersects the up-down direction is defined as the left-right direction. The direction that intersects the up-down direction and the left-right direction is defined as the front-back direction. The front-back direction is a direction perpendicular to the paper surface of Fig. 1. However, these directions are defined only for the sake of simplicity of description and do not limit the arrangement direction of the electromagnetic relay 1.

[0014] The contact device 2 is arranged in the housing 3. The contact device 2 includes a movable device 10, a first fixed terminal 11, a second fixed terminal 12, a movable contact piece 13, a first fixed contact 14, a second fixed contact 15, a first movable contact 16, and a second movable contact 17. The first fixed terminal 11 and the second fixed terminal 12 are made of a conductive material such as copper or a copper alloy. The first fixed contact 14 is connected to the first fixed terminal 11. The second fixed contact 15 is connected to the second fixed terminal 12. The first fixed contact 14 and the second fixed contact 15 are arranged apart from each other in the left-right direction.

[0015] The first fixed terminal 11 includes a first contact support part 21 and a first external connection part 22. The first contact support part 21 faces the movable contact piece 13. The first fixed contact 14 is connected to the first contact support part 21. The first external connection part 22 is connected to the first contact support part 21. The first external connection part 22 protrudes outward from the housing 3.

[0016] The second fixed terminal 12 includes a second contact support portion 23 and a second external connection portion 24. The second contact support portion 23 faces the movable contact piece 13. The second fixed contact 15 is connected to the second contact support portion 23. The second external connection portion 24 is connected to the second contact support portion 23. The second external connection portion 24 protrudes outward from the housing 3. More specifically, the first external connection portion 22 and the second external connection portion 24 protrude upward from the housing 3.

[0017] The movable contact piece 13 extends in the left-right direction. The movable contact piece 13 is arranged to face the first contact support part 21 of the first fixed terminal 11 and the second contact support part 23 of the second fixed terminal 12 in the up-down direction. The movable contact piece 13 is arranged to be movable in the closing direction Z1 and the opening direction Z2. The closing direction Z1 is a direction in which the movable contact piece 13 approaches the first fixed terminal 11 and the second fixed terminal 12. The closing direction Z1 is in Fig. 1 upwards. The opening direction Z2 is a direction in which the movable contact piece 13 is separated from the first fixed terminal 11 and the second fixed terminal 12. The opening direction Z2 is in Fig. 1 down

[0018] The first movable contact 16 and the second movable contact 17 are connected to the movable contact piece 13. The first movable contact 16 and the second movable contact 17 are spaced apart from each other in the left-right direction. The first movable contact 16 faces the first fixed contact 14 in the up-down direction. The second movable contact 17 faces the second fixed contact 15 in the up-down direction.

[0019] The movable device 10 supports the movable contact piece 13. The movable device 10 is arranged so that it is movable together with the movable contact piece 13 in the closing direction Z1 and the opening direction Z2. The movable device 10 includes a drive shaft 19, a first holding member 25, a second holding member 26, and a contact spring 27. The drive shaft 19 extends in the up-down direction. The drive shaft 19 is connected to the movable contact piece 13. The drive shaft 19 extends downward from the movable contact piece 13. A hole 13a is provided in the movable contact piece 13. The drive shaft 19 is inserted into the hole 13a. The movable contact piece 13 is movable relative to the drive shaft 19 in the closing direction Z1 and the opening direction Z2.

[0020] The drive shaft 19 is provided so that it is movable between a closed position and an open position. Fig. 1 shows the drive shaft 19 in the open position. As in Fig. 1, when the drive shaft 19 is in the open position, the movable contacts 16 and 17 are separated from the fixed contacts 14 and 15. Fig. 2 shows the drive shaft 19 in the closed position. As in Fig. 2, when the drive shaft 19 is in the closed position, the movable contacts 16 and 17 are in contact with the fixed contacts 14 and 15.

[0021] The first retaining element 25 is attached to the drive shaft 19. The contact spring 27 is arranged between the movable contact piece 13 and the first retaining element 25. The contact spring 27 biases the movable contact piece 13 in the closing direction Z1 while the movable contacts 16 and 17 are in contact with the fixed contacts 14 and 15. The second retaining element 26 is attached to the drive shaft 19. The movable contact piece 13 is located between the second retaining element 26 and the contact spring 27.

[0022] The drive device 4 actuates the movable contact piece 13 by an electromagnetic force. The drive device 4 moves the movable device 10 in the closing direction Z1 and the opening direction Z2. As a result, the drive device 4 moves the movable contact piece 13 in the closing direction Z1 and the opening direction Z2. The drive device 4 includes a movable iron core 31, a winding 32, a fixed iron core 33, a yoke 34, and a return spring 35.

[0023] The movable iron core 31 is connected to the drive shaft 19. The movable iron core 31 is provided so that it can move in the closing direction Z1 and the opening direction Z2. Current flows through the winding 32 to generate an electromagnetic force that moves the movable iron core 31 in the closing direction Z1. The fixed iron core 33 is arranged so that it opposes the movable iron core 31. The return spring 35 is arranged between the movable iron core 31 and the fixed iron core 33. The return spring 35 biases the movable iron core 31 in the opening direction Z2.

[0024] The yoke 34 is arranged to surround the winding 32. The yoke 34 is arranged in the magnetic circuit formed by the winding 32. The yoke 34 is arranged above the winding 32, to the side of the winding 32, and below the winding 32.

[0025] Next, the operation of the electromagnetic relay 1 is described. When the coil 32 is not energized, the drive device 4 is not energized. In this case, the drive shaft 19 is pressed in the opening direction Z2 by the elastic force of the return spring 35 together with the movable iron core 31. Therefore, the drive shaft 19 is located at the position shown in Fig. 1. In this state, the movable contact piece 13 is also pushed in the opening direction Z2 via the movable device 10. Therefore, when the drive shaft 19 is in the open position, the first movable contact 16 and the second movable contact 17 are separated from the first fixed contact 14 and the second fixed contact 15.

[0026] When current flows through the winding 32, the drive device 4 is energized. In this case, the electromagnetic force of the winding 32 causes the movable iron core 31 to move in the closing direction Z1 against the elastic force of the return spring 35. Accordingly, both the drive shaft 19 and the movable contact piece 13 move in the closing direction Z1. Therefore, as shown in Fig. 2, the drive shaft 19 to the closed position. As a result, as shown in Fig. 2, when the drive shaft 19 is in the closed position, the first movable contact 16 and the second movable contact 17 are in contact with the first fixed contact 14 and the second fixed contact 15, respectively.

[0027] When the current in the winding 32 is interrupted and the winding 32 is demagnetized, the movable iron core 31 is pressed in the opening direction Z2 by the elastic force of the return spring 35. Accordingly, both the drive shaft 19 and the movable contact piece 13 move in the opening direction Z2. Therefore, as shown in Fig. 1, the movable device 10 moves to the open position. As a result, when the movable device 10 is in the open position, the first movable contact 16 and the second movable contact 17 are separated from the first fixed contact 14 and the second fixed contact 15.

[0028] The control of the current in the winding 32 as described above is carried out by the Fig. 3. The electromagnetic relay 1 includes a drive circuit 41. The drive circuit 41 switches the electromagnetic relay 1 between an open state and a closed state according to an external control signal. The drive circuit 41 controls the winding current and the winding voltage supplied to the winding 32. More specifically, the drive circuit 41 controls the winding voltage through PWM (pulse width modulation) control.

[0029] The drive circuit 41 includes a supply circuit 42, a control circuit 43, a switch circuit 44, a return circuit 45, a winding voltage sensor 46, a winding current sensor 47, and a contact voltage detection unit 48. The supply circuit 42 is connected to an external power supply (not shown). The supply circuit 42 includes, for example, a switch. The supply circuit 42 is controlled by an external control signal and switches the supply to the drive circuit 41 on or off.

[0030] The control circuit 43 contains, for example, a processor. The control circuit 43 outputs a pulse signal to the switch circuit 44. The switch circuit 44 contains a semiconductor switching element, such as a MOS-FET (metal oxide semiconductor field-effect transistor). The switch circuit 44 switches the voltage applied by the supply circuit 42 to the winding 32 on and off according to the pulse signal from the control circuit 43.

[0031] The return circuit 45 is connected in parallel to the winding 32. The return circuit 45 includes, for example, a diode element. The winding voltage sensor 46 detects a winding voltage. The winding voltage sensor 46 inputs a signal indicative of the winding voltage to the control circuit 43. The winding current sensor 47 detects a winding current. The winding current sensor 47 inputs a signal indicative of the winding current to the control circuit 43. The contact voltage detection unit 48 detects a contact voltage. The contact voltage is the voltage between the contacts 14 to 17. The contact voltage detection unit 48 is, for example, a voltage sensor. However, the contact voltage detection unit 48 may be another detection unit, such as an optocoupler. The contact voltage detection unit 48 inputs a signal indicative of the contact voltage to the control circuit 43.

[0032] Fig. 4A to 4D show a timing chart explaining the control of the electromagnetic relay 1 by the drive circuit 41. Fig. Figure 4A shows the external control signal. When the control signal indicates "Off," electromagnetic relay 1 is in the open state. When the control signal indicates "On," electromagnetic relay 1 is in the closed state. Fig. Figure 4B shows the winding voltage signal. The winding voltage signal indicates the winding voltage. Fig. 4C shows the winding current. Fig. 4D shows a contact signal. The contact signal indicates the contact voltage. When electromagnetic relay 1 is open, the contact signal indicates "off." When electromagnetic relay 1 is closed, the contact signal indicates "on."

[0033] At time T0, the control signal is "off." Therefore, the control circuit 41 does not apply voltage to the winding 32, and no current flows in the winding 32. Therefore, the electromagnetic relay 1 is in the open state, and the contact signal indicates "off."

[0034] When the control signal is switched on at time T1, the control circuit 41 applies the winding voltage signal with the voltage value V1 and the duty cycle A1 to the winding 32 in the first period T1 to T2. The duty cycle A1 is less than 100%. Accordingly, from time T1, a current begins to flow in the winding 32, and the winding current increases in the first period T1 to T2 at the first increase rate. The increase rate of the winding current indicates the amount of current increase per unit time. Therefore, the first increase rate indicates the increase of the winding current in the first period T1 to T2 in Fig. 4C.

[0035] In the first period T1 to T2, the drive device 4 is energized by a current flowing in the winding 32. As a result, in the first period T1 to T2, the movable iron core 31 begins to move in the closing direction Z1, and the movable contacts 16 and 17 move in the closing direction Z1. At time T2, the movable contacts 16 and 17 come into contact with the fixed contacts 14 and 15. The drive circuit 41 detects the contacting of the contacts 14 to 17 based on the contact voltage detected by the winding voltage sensor 46. At this time, the winding current has a current value I1.

[0036] When the control circuit 41 detects the contacting of the contacts 14 to 17, the control circuit 41 applies the winding voltage signal with the voltage value V2 and the duty cycle A2 to the winding 32 in the second time period T2 to T3. The duty cycle A2 is greater than the duty cycle A1. For example, the duty cycle A2 is 100%. However, the duty cycle A2 can be less than 100%. The voltage value V2 is greater than the voltage value V1. As a result, the winding current increases in the second time period T2 to T3 at the second increase rate. The second increase rate is greater than the first increase rate. The second time period T2 to T3 is shorter than the first time period T1 to T2. That is, the first time period T1 to T2 is longer than the second time period T2 to T3.

[0037] When the winding current reaches current value I2 at time T3, the control circuit 41 reduces the winding voltage to voltage value V1. The control circuit 41 maintains the winding voltage at voltage value V1 during the third period T3 to T4. During the third period T3 to T4, the control circuit V1 applies the winding voltage signal with voltage value V1 and duty cycle A3 to the winding 32. Duty cycle A3 is greater than duty cycle A1. Duty cycle A3 is, for example, 100%. However, duty cycle A3 can be less than 100%.

[0038] In the third period T3 to T4, the winding current is maintained at the current value I2. The current value I2 is greater than the current value I1. As described above, in the second period T2 to T3 and the third period T3 to T4, the winding current increases rapidly and is maintained at the large current value I2, so the pressing force of the moving contacts 16 and 17 against the fixed contacts 14 and 15 increases. This reduces the bouncing of the moving contacts 16 and 17 in the second period T2 to T3 and the third period T3 to T4.

[0039] When a predetermined time has elapsed since time T3, the control circuit 41 applies the winding voltage signal with voltage value V1 and duty cycle A4 to the winding 32 in the fourth period after time T4. The duty cycle A4 is less than 100%. The duty cycle A4 is less than the duty cycle A1. This reduces power consumption while keeping the contacts 14 to 17 closed.

[0040] In the electromagnetic relay 1 according to the present embodiment described above, the current in the winding 32 flows at a smaller increase rate in the first period T1 to T2 than that in the second period T2 to T3. Therefore, the impact energy of the contacts 14 to 17 is reduced. This reduces contact impact. Further, in the second period T2 to T3, the current in the winding 32 flows at a larger increase rate than that in the first period T1 to T2. Therefore, the pressing force of the movable contacts 16 and 17 against the fixed contacts 14 and 15 increases. This further reduces contact impact. In addition, the impact noise when the contact is made is reduced.

[0041] Although an embodiment of the present invention is described above, the present invention is not limited to the above embodiment, and various modifications may be made without departing from the scope of the invention.

[0042] In the above-described embodiment, the driving device 4 pushes the driving shaft 19 from the driving device 4 side, so that the movable contact piece 13 moves in the closing direction Z1. Further, when the driving device 4 pulls the driving shaft 19 toward the driving device 4 side, the movable contact piece 13 moves in the opening direction Z2. However, the operating directions of the driving shaft 19 for opening and closing the contact may be opposite to those in the above-described embodiment. That is, the movable contact piece 19 may move in the closing direction Z1 when the driving device 4 pulls the driving shaft 19 toward the driving device 4 side. The movable contact piece may be moved in the opening direction Z2 when the driving device 4 pushes the driving shaft 19 from the driving device 4 side.That is, the closing direction Z1 and the opening direction Z2 may be opposite to those in the above embodiment.

[0043] The shape or arrangement of the first fixed terminal 11, the second fixed terminal 12, or the movable contact piece 13 may be changed. For example, as shown in Fig. 5, the first external terminal part 22 and the second external terminal part 24 protrude from the housing 3 in the left-right direction. Alternatively, the first external terminal part 22 and the second external terminal part 24 may protrude from the housing 3 in the front-back direction. The shape or arrangement of the movable iron core 31, the winding 32, the fixed iron core 33, or the yoke 34 may be changed. The shape or arrangement of the first fixed contact 14, the second fixed contact 15, the first movable contact 16, and the second movable contact 17 may be changed.

[0044] The first fixed contact 14 may be separate from the first fixed terminal 11 or may be an integral part with the first fixed terminal 11. The second fixed contact 15 may be separate from the second fixed terminal 12 or may be an integral part with the second fixed terminal 12. The first movable contact 16 may be separate from the movable contact piece 13 or may be an integral part with the movable contact piece 13. The second movable contact 17 may be a separate part from the movable contact piece 13 or may be an integral part with the movable contact piece 13.

[0045] The configuration of the drive circuit 41 is not limited to that of the above embodiment and may be changed. The drive circuit 41 may be a known circuit for performing PWM control. The contact voltage detection unit 48 may be omitted. In the above embodiment, the drive circuit 41 changes the increase rate of the winding current from the first increase rate to the second increase rate when the contacting of the contacts 14 to 17 is detected. However, the drive circuit 41 may measure the elapsed time from time T1 and change the increase rate of the winding current from the first increase rate to the second increase rate when a predetermined time has elapsed from time T1. In this case, the first period may be a period from time T1 to before the contacting time of the contacts 14 to 17. List of reference symbols 10 Movable device 11 First fixed connection 13 Movable contact piece 14 First solid contact 16 First moving contact 31 Movable iron core 32 windings 41 Control circuit 48 Contact voltage detection unit

Claims

[1] Electromagnetic relay comprising: a control circuit (41) designed to control a current in a winding (32), characterized by a fixed connection (11, 12); a fixed contact (14, 15) connected to the fixed terminal (11, 12); a movable contact piece (13) configured to move in an opening direction (Z2) and a closing direction (Z1) with respect to the fixed terminal (11, 12); a movable contact (16, 17) connected to the movable contact piece (13) and arranged to face the fixed contact (14, 15); wherein the winding (32) is designed to generate an electromagnetic force to move the movable contact piece (13); wherein the drive circuit (41) is designed to increase the current at a first increase rate in a first period (T1 to T2), comprising a period from a start time when the current in the winding (32) begins to flow until before a contact time at which the movable contact (16, 17) comes into contact with the fixed contact (14, 15), and with a second increase rate that is greater than the first increase rate, in a second period (T2 to T3) that includes a period after the time of contact. [2] Electromagnetic relay according to claim 1, wherein the drive circuit (41) is designed to maintain the current in the winding (32) at a greater current value (I2) than a current value (I1) during the first period in a third period (T3 to T4) after the second period (T2 to T3). [3] Electromagnetic relay according to claim 2, wherein the drive circuit (41) is designed to reduce the current in the winding (32) to a smaller current value (I1) in a fourth period after the third period (T3 to T4) than the current value (I2) in the third period (T3 to T4). [4] An electromagnetic relay according to any one of claims 1 to 3, wherein the first period (T1 to T2) is longer than the second period (T2 to T3). [5] Electromagnetic relay according to one of claims 1 to 4, further comprising a contact voltage detection unit (48) configured to detect a voltage (V) at the movable contact (16, 17) and the fixed contact (14, 15), wherein the drive circuit (41) is configured to detect the contact timing based on the voltage (V) detected by the contact voltage detection unit (48). [6] An electromagnetic relay according to claim 5, wherein the drive circuit (41) starts the second period (T2 to T3) based on the voltage (V) detected by the contact voltage detection unit (48). [7] Electromagnetic relay according to one of claims 1 to 6, further comprising: a movable device (10) connected to the movable contact piece (13); and a movable iron core (31) connected to the movable device (10) and designed to be moved by the electromagnetic force generated by the winding (32), wherein the first period (T1 to T2) comprises a period from the start time to a time when the movable iron core (31) starts to move.

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