JP2015217855A - Power supply relay controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply controller and an electric power steering device, capable of preventing imperfect contact of a relay appropriately.SOLUTION: When abnormal conduction occurs between relay contacts, a power supply controller switches a power supply relay circuit, keeping a predetermined potential difference between the relay contacts. During the above operation, the power supply controller switches a relay contact 121 to ON, while restricting a charge of an electrolytic capacitor 151 by a precharge circuit 150. In this way, a coating of ice existing between the relay contacts is removed by thermal energy of the inter-contact arc due to the potential difference between the relay contacts.

Description

  The present invention relates to a power supply relay control device that controls a relay disposed between a power supply and an actuator circuit that supplies electric power from the power supply.

In an electric power steering apparatus, generally, a mechanical relay is mounted on a power supply line and a motor line for the purpose of fail-safe. As such a relay, a hermetic sealing type relay is widely used in order to cut off the intrusion of moisture that causes contact freezing in a low temperature environment as much as possible.
In recent years, relays have been further downsized due to demands for system miniaturization and high output, and the internal volume of relays is decreasing. On the other hand, the case material used for relays is generally made of resin, and if this relay is left in a high temperature and high humidity environment for a long time, even if it is a relay that ensures airtightness, In particular, in a relay with a small internal volume, the internal relative humidity is greatly increased. As a result, condensation tends to occur at the relay contact.

Furthermore, for the purpose of improving heat dissipation, a system is employed in which a relay is directly mounted on a metal substrate and soldered with a reflow layer. As described above, when mounted on a metal substrate, the cooling rate is high, and moisture in the relay freezes in a low temperature environment, and there is a possibility that contact failure of the relay contact due to freezing of the contact may occur.
In order to prevent this, there is a technique described in Patent Document 1, for example. This technology removes foreign matters such as ice adhering to the relay contact by repeating ON / OFF operation of the relay. In addition, there is a technique described in Patent Document 2, for example. In this technique, a vibration is generated at a freezing occurrence location, and the freezing is released by this vibration.

JP 2007-276552 A JP 2007-165406 A

However, in the techniques described in Patent Documents 1 and 2, the ice generated at the relay contact is to be removed simply by repeating the ON / OFF operation of the relay or applying vibration. The ice may not be reliably removed.
Then, this invention makes it the subject to provide the power supply relay control apparatus which can prevent the contact failure of a relay appropriately.

In order to solve the above-mentioned problem, a first aspect of a power relay control device according to the present invention controls a power relay circuit interposed between a battery and an actuator circuit to which power is supplied from the battery. A relay control unit; an abnormality detection unit that detects a conduction abnormality between the relay contacts in a state in which a relay-on command for closing the relay contact of the power relay circuit is output from the relay control unit; and the abnormality detection unit And an abnormality processing unit that opens and closes the relay contact in a state where a predetermined potential difference is provided between the relay contacts when a conduction abnormality between the relay contacts is detected.
As a result, even if the contacts are close by the relay ON operation, even if an ice film exists between the relay contacts, the ice film is generated by the thermal energy of the arc between the contacts due to the potential difference between the relay contacts. Can be removed. Therefore, it is possible to easily ensure conduction between the relay contacts.

  Further, a capacitor connected between the actuator circuit side contact of the power relay circuit and the ground, and a precharge circuit for charging the capacitor before closing the relay contact, the abnormality processing unit When the abnormality detection unit detects a continuity abnormality between the relay contacts, the amount of charge to the capacitor in the precharge circuit is determined as normal when the abnormality detection unit does not detect a continuity abnormality between the relay contacts. The relay contact is opened and closed in a state of being limited to a small amount as compared with the above.

  In this way, the amount of charge by the precharge circuit is limited to be smaller than usual, so that a desired potential difference can be provided between the relay contacts. In addition, since a potential difference is usually provided between relay contacts by using charging and discharging of a precharge circuit used for a precharge operation that is always performed before turning on a power supply relay, special parts and devices are added. Without having to do so with an existing part structure.

Further, according to a second aspect, the abnormality detection unit is based on the amount of charge charged in the capacitor when the actuator circuit is driven in a state where the relay on command is output from the relay control unit. It is characterized by detecting a continuity abnormality between relay contacts.
As described above, when the actuator circuit is driven in a state where the relay contact is not conducted, the fact that the charge of the capacitor is lost is utilized, and therefore, the conduction abnormality between the relay contacts can be detected appropriately.

In the third aspect, the abnormality detection unit detects the voltage value at both ends of the capacitor as the amount of charge charged in the capacitor, and outputs the relay-on command from the relay control unit. When the voltage value when the actuator circuit is driven is equal to or less than an abnormal voltage threshold value, it is determined that a continuity abnormality has occurred between the relay contacts.
As described above, the voltage value at both ends of the capacitor when the actuator circuit is driven with the relay contact ON is compared with the preset abnormal voltage threshold value. Abnormalities can be detected.

Furthermore, the fourth aspect includes a temperature detection unit that detects a temperature in the vicinity of the relay contact, and the abnormality detection unit has a temperature detected by the temperature detection unit within the preset power relay circuit. When the temperature is equal to or lower than a low temperature environment determination temperature that is a temperature at which the possibility of icing is increased, a process for determining whether or not a conduction abnormality between the relay contacts has occurred is started.
As described above, when the power relay circuit is exposed to a low-temperature environment, it is determined whether or not there is a continuity abnormality between the relay contacts, thus preventing unnecessary continuity abnormality check of the relay contacts. be able to.

According to a first aspect of the electric power steering apparatus of the present invention, an electric motor for applying a steering assist force for reducing a steering burden on a driver to a steering system, a battery, and electric power are supplied from the battery. An actuator circuit as a motor drive circuit for driving and controlling an electric motor, a power relay circuit interposed between the battery and the actuator circuit, and any one of the power relay control devices Yes.
Thus, since the power supply relay that operates reliably in a low temperature environment can be used, an electric power steering device that performs stable steering assist control can be obtained.

  In the power supply relay control device of the present invention, the relay contact is opened and closed with a predetermined potential difference between the relay contacts, so that the arc attached to the relay contact can be melted by inducing arc discharge of the relay contact. Thus, the operation of the power supply relay in a low temperature environment can be ensured without using a special device.

1 is an overall configuration diagram showing an electric power steering apparatus according to the present invention. It is a block diagram which shows the specific structure of a control apparatus. It is a flowchart which shows the process sequence at the time of the low temperature environment performed by MCU. It is a time chart explaining operation | movement of the process at the time of a low temperature environment. It is a figure for demonstrating the effect of this embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is an overall configuration diagram showing an electric power steering apparatus according to the present invention.
In the figure, reference numeral 1 denotes a steering wheel, and a steering force applied to the steering wheel 1 from a driver is transmitted to a steering shaft 2 having an input shaft 2a and an output shaft 2b. The steering shaft 2 has one end of the input shaft 2a connected to the steering wheel 1 and the other end connected to one end of the output shaft 2b via a steering torque sensor 3 as steering torque detecting means.

  The steering force transmitted to the output shaft 2 b is transmitted to the intermediate shaft 5 via the universal joint 4 and further transmitted to the pinion shaft 7 via the universal joint 6. The steering force transmitted to the pinion shaft 7 is transmitted to the tie rod 9 via the steering gear 8 and steers steered wheels (not shown). Here, the steering gear 8 is configured in a rack and pinion type having a pinion 8a connected to the pinion shaft 7 and a rack 8b meshing with the pinion 8a, and the rotational motion transmitted to the pinion 8a is linearly moved by the rack 8b. It has been converted to movement.

A steering assist mechanism 10 for transmitting a steering assist force to the output shaft 2b is connected to the output shaft 2b of the steering shaft 2. The steering assist mechanism 10 includes a reduction gear 11 connected to the output shaft 2b, and an electric motor 13 formed of a brush motor that is connected to the reduction gear 11 and generates an auxiliary steering force for the steering system. Yes.
The steering torque sensor 3 detects the steering torque applied to the steering wheel 1 and transmitted to the input shaft 2a. For example, the steering torque sensor 3 is a torsion bar (not shown) in which the steering torque is interposed between the input shaft 2a and the output shaft 2b. It is configured to convert to a torsional angular displacement, detect this torsional angular displacement with a magnetic signal, and convert it into an electrical signal.

  The steering torque sensor 3 is for detecting a steering torque applied to the steering wheel 1 and transmitted to the input shaft 2a, and is a relative force between the input shaft 2a and the output shaft 2b connected by a torsion bar (not shown). The displacement (rotational displacement) is detected in correspondence with the change in the impedance of the coil pair. The detected torque value T output from the steering torque sensor 3 is input to the control device 14.

The control device 14 operates by being supplied with power from a battery 15 (for example, 13 V) as a DC power source. The negative electrode of the battery 15 is grounded, and the positive electrode thereof is connected to the control device 14 via an ignition switch 16 that starts the engine, and is directly connected to the control device 14 without passing through the ignition switch 16.
In addition to the torque detection value T, the vehicle speed detection value Vs detected by the vehicle speed sensor 17 is input to the control device 14, and steering assist control is performed to apply a steering assist force corresponding to these to the steering system. Specifically, a steering assist torque command value for generating the steering assist force by the electric motor 13 is calculated according to a known procedure, and the electric motor 13 is supplied with the calculated steering assist torque command value and the motor current detection value. The drive current to be supplied is feedback controlled.

  As shown in FIG. 2, the control device 14 performs a predetermined calculation based on the torque detection value T and the vehicle speed detection value Vs and outputs a motor drive signal Ir and a motor rotation direction signal Ds (hereinafter, referred to as a “micro control unit”). (Referred to as MCU) 101. The control device 14 is interposed between the motor drive circuit 110 that drives the electric motor 13 based on the motor drive signal Ir and the motor rotation direction signal Ds output from the MCU 101, and the battery 15 and the motor drive circuit 110. And a power relay circuit 120 that controls power supply from the battery 15 to the motor drive circuit 110.

Here, the power relay circuit 120 is directly mounted on a metal substrate and soldered with a reflow layer for the purpose of improving heat dissipation. Further, the power relay circuit 120 is arranged in a resin case in which airtightness is ensured.
Further, the control device 14 determines the motor angular velocity ω based on the motor current detection circuit 130 that detects the motor current I, the motor terminal voltage Vm, and the motor drive current (current detection value) Im detected by the motor current detection circuit 130. A motor angular velocity estimation circuit 140 for estimation.

  The control device 14 is connected in parallel with the power supply relay circuit 120, and supplies a precharge circuit 150 for supplying a precharge voltage to the motor drive circuit 110 side at the relay contact 121 of the power supply relay circuit 120, and the ignition switch 16. A power supply circuit 160 that is connected to the battery 15 and forms control power in the control device 14 at startup, and a contact voltage detection circuit 170 that detects the contact voltage VR on the motor drive circuit 110 side at the relay contact 121 of the power supply relay circuit 120. I have.

  Here, as shown in FIG. 2, the motor drive circuit 110 includes four NPN transistors Q1 to Q4 to which the battery voltage Vb of the battery 15 is input via the relay contact 121 of the power supply relay circuit 120. An H bridge circuit 111 for supplying a motor current I for forward / reverse driving to the electric motor 13 and a gate drive circuit 112 for driving and controlling the transistors Q1 to Q4 of the H bridge circuit 111 are provided.

The gate drive circuit 112 receives a motor current command value Ir and a motor rotation direction signal Ds output from the MCU 101, which will be described later, and controls driving of the diagonal transistors Q1 and Q3 or Q2 and Q4 based on them. The electric motor 13 is rotationally driven according to the steering torque detection value T and the vehicle speed detection value Vs.
The power supply relay circuit 120 includes a normally-open relay contact 121 connected to the battery 15 and a relay coil 122 that opens and closes the relay contact 121. A surge absorbing diode 123 is connected to the relay coil 122 in parallel. One end of the relay coil 122 is connected to the battery 15 via an NPN transistor 124 as a switching element, and the other end is grounded.

Further, the precharge circuit 150 includes an electrolytic capacitor 151 interposed between a relay contact on the motor drive circuit 110 side of the power supply relay circuit 120 and the ground, a connection point between the electrolytic capacitor 151 and the relay contact 121, and a battery. It is composed of an NPN transistor 152 as a switching element connected between the relay contact on the 15th side, a reverse current blocking diode 153, and a series circuit composed of a precharge resistor 154.
The transistor 124 of the power supply relay circuit 120 is driven and controlled by a relay drive signal (relay on command / relay off command) SR formed by the MCU 101. The transistor 152 of the precharge circuit 150 is driven and controlled by a pulse width modulation signal SP formed by the MCU 101.

Next, the configuration of the MCU 101 will be described.
The MCU 101 includes a watch dog timer (WDT) 102 that monitors its own program runaway. Further, the MCU 101 generates a motor drive signal Ir based on the detected steering torque value T, the detected vehicle speed value Vs, and the detected current value Im, and inputs the motor drive signal Ir to the motor drive circuit 110.

Further, as shown in FIG. 2, the MCU 101 includes a ROM (read only memory) 103 that stores a steering assist control processing program, an abnormality detection processing program, and the like, detection data such as a torque detection value T, a motor drive current Im, A RAM (Random Access Memory) 104 that stores data and processing results required in the steering assist control process and precharge drive process executed by the MCU 101 is incorporated.
Then, the MCU 101 executes a precharge drive process and a steering assist control process when the ignition switch 16 is turned on and the battery voltage Vb is supplied from the battery 15.

  In the precharge driving process, the precharge resistor 154 can be set to the minimum necessary resistance value with respect to the transistor 152 of the precharge circuit 150 when a predetermined time has elapsed since the process was started. Output of a pulse width modulation signal SP having a predetermined frequency is started. As a result, the transistor 152 is turned on / off, and the electrolytic capacitor 151 is charged with electric charge based on the battery voltage Vb. Thereafter, when a predetermined time further elapses, the MCU 101 outputs a high-level relay drive signal (relay-on command) SR to the switching element 124 of the power supply relay circuit 120 and the pulse width modulation signal SP to the precharge circuit 150. Stop the output of. As described above, the precharge driving process for charging the electrolytic capacitor 151 is performed before the relay contact 121 is closed. Then, the MCU 101 executes the steering assist control process after the precharge driving process is completed and the relay contact 121 is closed.

  Further, when the MCU 101 inputs the temperature in the vicinity of the power relay circuit 120 (temperature detection value Temp) detected by the temperature sensor 180 and determines that the power relay circuit 120 is exposed to a low temperature environment, the MCU 101 freezes the relay contact 121. Execute processing at low temperature environment for the purpose of prevention. Here, it is assumed that the temperature sensor 180 is disposed on a metal substrate on which the power relay circuit 120 is mounted.

FIG. 3 is a flowchart showing a low temperature environment processing procedure executed by the MCU 101 when a relay conduction abnormality is detected.
First, in step S1, the MCU 101 determines whether or not the temperature detection value Temp of the temperature sensor 180 is equal to or lower than a preset low temperature determination temperature. Here, the low temperature determination temperature is set to a temperature at which the possibility that water in the power relay circuit 120 freezes is increased. If the temperature detection value Temp is equal to or lower than the low temperature determination temperature, it is determined that the power supply relay circuit 120 is exposed to a low temperature environment, and the process proceeds to step S2, and the temperature detection value Temp exceeds the low temperature determination temperature. If it is, the relay contact 121 is judged not to have a conduction failure due to freezing, and the low temperature environment process is terminated.

In step S2, the MCU 101 discharges the electrolytic capacitor 151. That is, a relay drive signal (relay off command) SR for opening the relay contact 121 is output and the motor drive circuit 110 is driven.
Next, in step S3, the MCU 101 determines whether or not the retry operation number N in the process for abnormal conduction for ensuring the conduction of the relay contact 121 is equal to or greater than the preset number n, and N <n. If so, the process proceeds to step S4. If N ≧ n, the process proceeds to step S5 described later. Note that the initial value of the retry operation count N is 0.

In step S4, the MCU 101 starts the charging operation to the electrolytic capacitor 151 by the precharge circuit 150 and determines a predetermined voltage (for example, 3) from the charging voltage of the electrolytic capacitor 151 and the battery voltage Vb for determining the timing for closing the relay contact 121. .5 [V]) A low voltage VR1 is set, and the process proceeds to step S6. This voltage VR1 is referred to as a normal relay ON voltage in the following description.
In step S5, the MCU 101 starts the charging operation to the electrolytic capacitor 151 by the precharge circuit 150 and sets the charging voltage of the electrolytic capacitor 151 that determines the timing for closing the relay contact 121 to the voltage VR2 lower than the voltage VR1. And the process proceeds to step S6. This voltage VR2 is referred to as a limit relay ON voltage in the following description.

In step S6, the MCU 101 indicates the timing at which the voltage value (VR voltage) across the electrolytic capacitor 151 indicating the amount of charge of the electrolytic capacitor 151 reaches the relay ON voltage VR1 or VR2 set in step S4 or step S5. To close the relay contact 121.
Next, in step S7, the MCU 101 stops the output of the pulse width modulation signal SP, thereby ending the operation of charging the electrolytic capacitor 151 by the precharge circuit 150 and driving the motor drive circuit 110 (forced drive).

In step S <b> 8, the MCU 101 increments the retry operation count N, proceeds to step S <b> 9, and determines whether a continuity abnormality has occurred in the relay contact 121. Here, the VR voltage is confirmed, and when the VR voltage is equal to or less than the preset abnormal voltage threshold, it is determined that the conduction abnormality of the relay contact 121 has occurred, and the process proceeds to step S10. On the other hand, if the VR voltage does not drop, it is determined that the relay contact 121 is normally conducting, and the low temperature environment process is terminated as it is (normal end).
In step S10, the MCU 101 determines whether or not the retry operation number N has reached a preset upper limit number Nmax. If N <Nmax, the process proceeds to step S2, and if N = Nmax. Shifts to step S11.

In step S11, the MCU 101 determines that the continuity abnormality of the relay contact 121 is not eliminated even if Nmax retry operations are performed, notifies the continuity abnormality of the relay contact 121, and ends the low temperature environment processing (abnormal termination). ).
The motor drive circuit 110 in FIG. 2 corresponds to the actuator circuit, the MCU 101 and the transistor 124 correspond to the relay control unit, and the temperature sensor 180 corresponds to the temperature detection unit. In FIG. 3, steps S5 and S6 correspond to the abnormality processing unit, and steps S7 and S9 correspond to the abnormality detection unit.

Next, the operation of this embodiment will be described.
When the driver turns on the ignition switch 16, control power is supplied from the power supply circuit 160 into the control device 14, and the MCU 101 is activated. At this time, the MCU 101 executes a precharge drive process and a steering assist control process.

  In the precharge driving process, first, output of a relatively low frequency pulse width modulation signal SP that minimizes the resistance value of the precharge resistor 154 is started with respect to the NTN transistor 152 of the precharge circuit 150. When this pulse width modulation signal SP is supplied to the gate of the NTN transistor 152 of the precharge circuit 150, the NTN transistor 152 is repeatedly turned on and off, so that the electrolytic capacitor 151 is charged based on the battery voltage Vb. Go.

As a result, the contact voltage VR on the motor drive circuit side of the power relay circuit 120 gradually increases and is slightly lower than the battery voltage Vb determined by the frequency of the pulse width modulation signal SP and the resistance value of the precharge resistor 154 with respect to the battery voltage Vb. Increases to the precharge voltage VP. After the motor drive circuit side contact voltage VR reaches the precharge voltage VP, the precharge voltage VP is maintained as it is.
Thereafter, when a high-level relay drive signal (relay-on command) SR is output to the NTN transistor 124 of the power supply relay circuit 120, the relay coil 122 is energized from the battery 15, whereby the relay coil 122 is energized. The relay contact 121 is closed.

Therefore, the battery voltage Vb is supplied to the motor drive circuit 110 via the relay contact 121 of the power supply relay circuit 120. As a result, the motor drive circuit 110 becomes operable. At this time, since the potential difference between the battery voltage Vb on the battery 15 side of the relay contact 121 and the precharge voltage VP on the motor drive circuit 110 side is small, the inrush current flowing to the electrolytic capacitor 151 through the relay contact 121 is a small value. Therefore, contact welding of the relay contact 121 can be reliably prevented.
Therefore, the potential difference between both ends of the relay contact 121 of the power relay circuit 120 can be reduced, and the inrush current through the relay contact 121 of the power relay circuit 120 can be reliably suppressed.

  Then, when the precharge driving process is completed, the MCU 101 executes a steering assist control process. In the steering assist control process, a steering assist torque command value for generating a steering assist force by the electric motor 13 is calculated based on the torque detection value T and the vehicle speed detection value Vs, and the calculated steering assist torque command value and motor current are calculated. The drive current supplied to the electric motor 13 is feedback-controlled based on the detected value. As a result, steering assist control that reduces the steering burden on the driver can be performed.

  By the way, the power supply relay circuit 120 of this embodiment is a hermetic sealing type relay, and is further mounted on a metal substrate in order to improve the heat dissipation of the electrical components due to high output. In addition, since the relay is miniaturized using a resin case, the resin absorbs moisture in a high temperature environment, and the humidity inside the relay is likely to increase. In addition, when mounted on a metal substrate, the cooling rate is fast, and when the temperature is below freezing, the water inside the relay is likely to freeze. If ice adheres to the relay contact, even if the relay contact 121 is turned on, the relay contact may not be conducted, and the motor drive circuit 110 may malfunction.

Therefore, in this embodiment, the relay ON / OFF operation is performed with a predetermined potential difference between the relay contacts for the purpose of removing the ice film existing between the relay contacts at the time of low temperature determination. The operation at this time will be described with reference to FIG.
First, the electrolytic capacitor 151 in the precharge circuit 150 is discharged, and then the precharge circuit 150 starts charging the electrolytic capacitor 151. When the VR voltage reaches the normal relay ON voltage VR1 at time t1, the relay contact 121 is turned on, and the charging of the electrolytic capacitor 151 by the precharge circuit 150 is terminated after the VR voltage reaches the precharge voltage VP. Next, at time t2, the motor drive circuit 110 is forcibly driven to check continuity. That is, a current necessary for power assist is supplied from the battery 15 to the H bridge circuit 111 via the power relay 120.

  At this time, if ice adheres to the relay contact 121, the relay contact 121 is not turned on even when the relay contact 121 is turned on, and the assist current cannot be supplied to the H bridge circuit 111. Therefore, in this case, the charge of the electrolytic capacitor 151 is lost at the time t2, and the VR voltage drops. As described above, the continuity abnormality of the relay contact 121 can be detected by checking the VR voltage corresponding to the charge amount of the electrolytic capacitor 151 when the motor drive circuit 110 is driven with the relay contact 121 turned ON. it can.

  When the conduction abnormality of the relay contact 121 is detected, the precharge circuit 150 starts charging the electrolytic capacitor 151 again at time t3. That is, at this time t3, the forced drive for checking the continuity is finished and the relay contact 121 is turned off. When the VR voltage reaches the normal relay ON voltage VR1 at time t4, the relay contact 121 is turned on. In this way, the first retry operation is performed.

  Thereafter, if the ice adhering to the relay contact 121 is not removed even after performing a plurality of (n-1) retry operations, the nth retry operation gives a predetermined potential difference between the relay contacts 121. In this state, the relay contact 121 is turned ON / OFF. Specifically, when the VR voltage reaches the limit relay ON voltage VR2 at time t5, the relay contact 121 is turned on. At this time, charging of the electrolytic capacitor 151 by the precharge circuit 150 is terminated at time t5.

In this way, by limiting the charging voltage of the electrolytic capacitor 151, the relay contact 121 can be turned on in a state where there is a potential difference of (Vb−VR2) between the relay contacts 121. At this time, an arc is generated between the relay contacts due to the potential difference, and ice can be easily removed by the thermal energy.
If the n-th retry operation does not completely remove the ice adhering to the relay contact, and if the VR voltage drops when the forced drive for continuity check is performed at time t6, the pre-charge is again performed at time t7. Charging of the electrolytic capacitor 151 by the charging circuit 150 is started, and at time t8 when the VR voltage reaches the limit relay ON voltage VR2, the (n + 1) -th retry operation is performed. This retry operation is repeated until the number of retry operations reaches the upper limit number Nmax.

Therefore, it is possible to reliably remove the ice adhering to the relay contact and ensure the conduction of the relay contact 121.
When normal precharge is performed to charge the electrolytic capacitor 151 to the precharge voltage VP as in the first retry operation (time t4) described above, the potential difference between the relay contacts is (Vb−VP) and a relatively small state. Become. Therefore, even if the relay contact 121 is turned on in this state, no arc is generated between the relay contacts, and the ice cannot be melted (FIG. 5A).

In the present embodiment, from the n-th retry operation (time t5), the charging of the electrolytic capacitor 151 is limited, and the relay contact 121 is turned on with a potential difference of (Vb−VR2) between the relay contacts. Therefore, when the relay contacts are close to each other, even if the relay contact 121 does not come into contact with the ice attached, the ice can be melted by the heat generated due to the generation of the arc (FIG. 5B).
As described above, using the charging and discharging of the electrolytic capacitor 151 of the precharge circuit 150, the arc discharge of the relay contact 121 is induced and the ice adhering to the contact is melted. Therefore, it is possible to ensure the operation in a low temperature environment even in the relay arranged on the metal substrate without adding any special parts or devices.

(Modification)
In the above-described embodiment, the case where the continuity check of the relay contact 121 and the processing at the time of continuity abnormality are performed when it is determined that the environment is a low temperature based on the detected temperature Temp of the temperature sensor 180 has been described. You may make it perform the conduction | electrical_connection check of the relay contact 121 each time, and the process at the time of continuity abnormality.

Moreover, in the said embodiment, although the case where a brush motor was used as the electric motor 13 was demonstrated, a brushless motor can also be used.
Furthermore, in the above embodiment, the case where the present invention is applied to the power relay circuit 120 interposed between the battery 15 and the motor drive circuit 110 has been described. The circuit 110 is not limited to this. That is, the present invention can be applied to devices other than the electric power steering device.

Furthermore, the temperature history to which the ECU has been exposed is held for a predetermined period, and the maximum number of times to repeat the ice-breaking operation is set based on the temperature history. This eliminates the need for wasteful arc discharge.

If continuity does not occur even after the maximum number of retries has been reached, display is displayed in some form (display, etc.), and a decision is made as to whether to retry again after a predetermined time has elapsed or to operate without assistance You may ask the person.

In addition, for preventive maintenance of the relay contacts, when the number of times of processing at the low temperature exceeds a predetermined value, the driver may be notified to promote maintenance for prevention.

  DESCRIPTION OF SYMBOLS 1 ... Steering wheel, 2 ... Steering shaft, 3 ... Steering torque sensor, 8 ... Steering gear, 10 ... Steering assist mechanism, 13 ... Electric motor, 14 ... Control device, 15 ... Battery, 16 ... Ignition switch, 17 ... Vehicle speed sensor , 101 ... MCU, 110 ... motor drive circuit, 111 ... H bridge circuit, 112 ... gate drive circuit, 120 ... power relay circuit, 121 ... relay contact, 122 ... relay coil, 124 ... transistor, 130 ... motor current detection circuit, DESCRIPTION OF SYMBOLS 140 ... Motor angular velocity estimation circuit, 150 ... Precharge circuit, 151 ... Electrolytic capacitor, 152 ... Transistor, 154 ... Precharge resistor, 155 ... Series circuit, 160 ... Power supply circuit, 170 ... Contact voltage detection circuit, 180 ... Temperature sensor

Claims (7)

A relay controller for controlling a power relay circuit interposed between the battery and an actuator circuit to which power is supplied from the battery;
In a state in which a relay on command for closing the relay contact of the power relay circuit is output from the relay control unit, an abnormality detection unit that detects a conduction abnormality between the relay contacts;
When the abnormality detection unit detects a conduction abnormality between the relay contacts, an abnormality processing unit that opens and closes the relay contact with a predetermined potential difference between the relay contacts;
A capacitor connected between the actuator circuit side contact of the power relay circuit and ground;
A precharge circuit that charges the capacitor before closing the relay contact, and the abnormality processing unit detects the conduction abnormality between the relay contacts by the abnormality detection unit, the precharge circuit in the precharge circuit A power relay control device that opens and closes the relay contact in a state in which the amount of charge to a capacitor is limited by the abnormality detection unit to be less than that in a normal state where a conduction abnormality between the relay contacts is not detected. .   The abnormality detection unit detects a conduction abnormality between the relay contacts based on a charge amount charged in the capacitor when the actuator circuit is driven in a state where the relay on command is output from the relay control unit. The power supply relay control device according to claim 1, wherein   The abnormality detection unit detects the voltage value at both ends of the capacitor as the amount of charge charged in the capacitor, and drives the actuator circuit in a state where the relay control unit outputs the relay on command. 3. The power relay control device according to claim 1, wherein when the voltage value is equal to or less than an abnormal voltage threshold, it is determined that a continuity abnormality has occurred between the relay contacts. A temperature detector for detecting the temperature in the vicinity of the relay contact;
When the temperature detected by the temperature detection unit is equal to or lower than a preset low temperature environment determination temperature, which is a temperature at which the moisture inside the power relay circuit is likely to freeze, The power relay control device according to any one of claims 1, 2, and 3, wherein processing for determining whether or not a continuity abnormality is occurring is started. 5. The power relay control device according to claim 1, further comprising: a storage unit that stores a temperature detected by the temperature detection unit, wherein the maximum number of retries is set based on a temperature history thereof. 6. The power relay control device according to claim 1, wherein when the continuity is not established even at the maximum number of retries, the driver is notified. 6. The power supply relay control device according to claim 1, wherein when the number of low-temperature treatments exceeds a predetermined number, the driver is notified for preventive maintenance.

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