JP7099066B2 - Auxiliary power supply and electric power steering - Google Patents

Description

The present invention relates to an auxiliary power supply device and an electric power steering device provided with the auxiliary power supply device.

As an electric power steering device that assists the driver in steering, there is one provided with an auxiliary power supply device as seen in Patent Document 1. The auxiliary power supply device is provided to temporarily increase the amount of power supplied to the steering assisting motor when a large steering assisting force is required, such as during stationary steering.

FIG. 5 shows the configuration of the electric circuit of the conventional auxiliary power supply device 100. As shown in the figure, the auxiliary power supply device 100 includes an input port 102 connected to the main power supply 101 and an output port 104 connected to the motor 103 to be fed. The auxiliary power supply device 100 is provided with a capacitor 105 capable of charging an electric charge between the two electrode plates 105A and 105B, and a chopper coil 106 which is a step-up coil.

One of the two plates of the capacitor 105 (plate 105A) is connected to the low potential line 108, which is the wiring connected to the input port 102 via the relay 107. One end of the chopper coil 106 is connected to the low potential line 108, the other end is connected to the ground via the first switching element 109, and the electrode plate of the capacitor 105 is connected to the ground via the second switching element 110. It is provided in the auxiliary power supply device 100 in a state of being connected to the 105B.

The high potential line 111, which is a wiring connecting the second switching element 110 and the electrode plate 105B of the capacitor 105, is connected to the output port 104 via the third switching element 112. Further, the low potential line 108 is connected to the output port 104 via the fourth switching element 113.

In the auxiliary power supply device 100 as described above, when the first to third switching elements 109, 110, 112 are in the open state (off) and the relay 107 and the fourth switching element 113 are in the closed state (on), it is mainly The output power of the power supply 101 is directly supplied to the motor 103. From this state, when the first and second switching elements 109 and 110 are alternately PWM-driven so as to be in the closed state (ON), the potential of the high potential line 111 is boosted and between the plates 105A and 105B of the capacitor 105. Is charged with electric charge. After the PWM drive of the first and second switching elements 109 and 110 is stopped, the fourth switching element 113 is opened (off) and the third switching element 112 is closed (on). The electric charge charged in 105 is discharged and supplied to the motor 103.

JP-A-2015-157519

In the conventional auxiliary power supply device 100, if the first switching element 109 is in a short-circuited state when the relay 107 is closed (on) in order to start power supply, both terminals of the main power supply 101 are connected. Are both connected to the ground, and as shown by the broken line arrow in FIG. 5, a current flows from the terminal on the positive electrode side of the main power supply 101 to the ground reference point. It is desirable to confirm the failure of the first switching element 109 that causes such a short circuit between the terminals of the main power supply 101 before the start of power supply of the auxiliary power supply device 100 (before closing the relay 107). After the start of power supply, the failure of the first switching element 109 can be diagnosed from the potentials and current values of the chopper coil 106 and the connection points of the first and second switching elements 109 and 110. However, when the relay 107 is in the open state (off), the potentials of the connection points of the chopper coil 106 and the first and second switching elements 109 and 110 are indefinite, so that the current and potential determination thresholds related to the diagnosis are set. Since it cannot be determined, it is difficult to diagnose the failure of the first switching element 109 before the start of feeding.

The auxiliary power supply device for solving the above problems includes an input port connected to the main power supply, an output port connected to the power supply target, a charge / discharge circuit interposed between the input port and the output port, and a charge / discharge circuit. In an auxiliary power supply device comprising, the charge / discharge circuit can charge a charge between a low potential line, which is a wiring connected to the input port via a relay, and a first plate and a second plate. In the capacitor, the low potential line is connected to the first electrode plate, one end is connected to the low potential line, and the other end is connected to the ground via the first switching element. When the chopper coil whose other end is connected to the second electrode plate via the second switching element and the wiring connecting the second switching element and the second electrode plate are defined as a high potential line. A pull-up resistor having one end connected to the input port without the relay and the other end connected to the high-potential line, a connection point of the pull-up resistor in the high-potential line, and the second pole. It has a third switching element installed in a portion between the plate and a switch for discharging interposed between the high potential line and the output port.

In the above auxiliary power supply device, the potential of the connection point of the pull-up resistor in the high potential line when all of the relay, the switch for discharging, and the first, second, and third switching elements are in the open state is a fixed value. It becomes. When the second switching element is closed from this state, the potential on the chopper coil side of the first switching element becomes the same as the potential at the connection point. As a result, since the potentials at both ends of the first switching element are fixed, it becomes possible to perform a failure diagnosis of the first switching element based on the current and the potential before starting the power supply with the relay closed.

If the first switching element is closed for failure diagnosis before the start of power supply in a state where the relay is short-circuited, both terminals of the main power supply are short-circuited through the first switching element. Therefore, it is desirable to confirm in advance that there is no short-circuit failure of the relay before diagnosing the failure of the first switching element. However, if both ends of the relay are connected via a pull-up resistor, a short-circuit failure of the relay cannot be diagnosed. In that respect, in the above configuration, a second switching element is interposed between the relay and the pull-up resistor, and by keeping the second switching element in the open state, it is possible to diagnose a short-circuit failure of the relay. Become.

The failure diagnosis in the auxiliary power supply device is performed by short-circuiting the relay in a fully open command state in which an open command is output to all of the relay, the discharge switch, and the first, second, and third switching elements. The first step of diagnosing the presence or absence of a failure, the second step of diagnosing the presence or absence of a short-circuit failure of the second switching element while maintaining the fully open command state after the execution of the first step, and the second step. After performing the step, an open command is output to the relay, the discharge switch, and the first and third switching elements, respectively, and a close command is output to the second switching element. After performing the third step of diagnosing the presence or absence of a short-circuit failure of the first switching element and the third step, an open command is output to the relay, the discharge switch, and the third switching element, respectively. It is desirable that the closing command be output to the first and second switching elements, respectively, and then the fourth step of diagnosing the presence or absence of a normally open failure of the first switching element.

Further, if the auxiliary power supply device is provided with a bypass circuit that bypasses the charge / discharge circuit and allows current to flow from the input port to the output port, power can be supplied through the bypass circuit even when the charge / discharge circuit fails. It will be possible.

The charging / discharging circuit in the auxiliary power supply device may be configured to include a charging switch interposed between the low potential line and the output port. In such a configuration, when the failure diagnosis of the auxiliary power supply device is performed through the first to fourth stages, it is preferable that the open command is output to the charging switch at any stage.

The auxiliary power supply device is provided with, for example, a motor for steering assistance, and the motor can be applied to an electric power steering device to which the auxiliary power supply device is to be fed.

According to the present invention, a failure of a switching element that causes a short circuit between terminals of a main power supply can be diagnosed before the start of power supply.

The schematic which shows the structure of the electric power steering apparatus of embodiment schematically. The circuit diagram which shows the structure of the electric circuit of the electric power steering apparatus. A table showing the operating state of the switching element and the potential monitor position in each of the first to fourth stages of the failure diagnosis performed in the auxiliary power supply device of the embodiment. A table showing the operating state of the switching element in each operating state of the auxiliary power supply device of the embodiment. The circuit diagram which shows the structure of the electric circuit of the conventional auxiliary power supply device.

Hereinafter, an embodiment of the auxiliary power supply device and the electric power steering device will be described in detail with reference to FIGS. 1 to 4.
As shown in FIG. 1, the electric power steering device (hereinafter referred to as EPS1) of the present embodiment includes a steering shaft 4 in which a steering wheel 2 is fixed at one end and a pinion gear 3 is fixed at the other end. .. The pinion gear 3 is meshed with a rack gear 6 formed on the rack shaft 5. These pinion gears 3 and rack gears 6 form a rack and pinion mechanism that converts the rotational motion of the steering shaft 4 into a linear motion in the longitudinal direction of the rack shaft 5. When the electric power steering device 1 is assembled to the vehicle, the rack shaft 5 is attached to the vehicle body so that its longitudinal direction is the vehicle width direction, and both ends of the rack shaft 5 are left and right steering wheels. Each is connected to 7 via a tie rod 8.

The steering shaft 4 is equipped with a torque sensor 9 for measuring the steering torque TR applied to the steering shaft 4 by operating the steering wheel 2. In the present embodiment, as the torque sensor 9, a sensor having a configuration in which the twist amount of the torsion bar constituting a part of the steering shaft 4 is detected and the steering torque TR is measured based on the twist amount is adopted. There is.

Further, a steering assisting motor (hereinafter referred to as an assist motor 10) is connected to the steering shaft 4 via a speed reducer 11 that decelerates the rotation of the assist motor 10 and transmits the rotation to the steering shaft 4. There is. In this embodiment, a three-phase brushless motor is used as the assist motor 10. Further, in the present embodiment, the worm gear mechanism is adopted as the speed reducer 11.

Further, the electric power steering device 1 includes a motor drive circuit 12, an auxiliary power supply device 13, and an electronic control unit 14. As the motor drive circuit 12, a known circuit having two switching elements in each phase of the assist motor 10 is adopted. Further, when the electric power steering device 1 is assembled to the vehicle, the auxiliary power supply device 13 and the electronic control unit 14 are connected to the vehicle-mounted battery 15 as the main power source, respectively.

The electronic control unit 14 includes an arithmetic processing circuit 16 that executes arithmetic processing related to the control of the electric power steering device 1, and a memory 17 in which control programs and data are regulated. Further, the above-mentioned torque sensor 9 is connected to the electronic control unit 14. Further, when the electric power steering device 1 is assembled to the vehicle, the electronic control unit 14 is connected to the vehicle speed sensor 18 which is installed in the vehicle and detects the traveling speed VS of the vehicle.

The electronic control unit 14 controls the steering assist force applied by the assist motor 10 in the electric power steering device 1 in a state of being assembled to the vehicle. When controlling the steering assist force, the electronic control unit 14 first determines a target assist force, which is a target value of the steering assist force based on the steering torque TR and the traveling speed VS. Then, the electronic control unit 14 controls the motor drive circuit 12 and the auxiliary power supply device 13 in order to generate a steering assist force corresponding to the target assist force.

As shown in FIG. 2, the auxiliary power supply device 13 includes an input port 20 and an output port 21. The input port 20 is connected to the vehicle-mounted battery 15 when the electric power steering device 1 is assembled to the vehicle. Further, the output port 21 is connected to the assist motor 10 to be fed via the motor drive circuit 12 when the auxiliary power supply device 13 is assembled to the electric power steering device 1. The auxiliary power supply device 13 includes two circuits, a charge / discharge circuit C1 and a bypass circuit C2, which are interposed between the input port 20 and the output port 21, respectively.

The charge / discharge circuit C1 includes a low potential line 23 which is a wiring connected to the input port 20 via a relay for connecting / disconnecting the power supply from the vehicle-mounted battery 15. In the following description, the relay of the charge / discharge circuit C1 will be referred to as a main relay 22. In the present embodiment, as the main relay 22, a non-contact relay composed of two switching elements (hereinafter, referred to as FET 5 and FET 6) is adopted.

Further, the charge / discharge circuit C1 includes a capacitor 24 capable of charging / discharging electric charges. In the present embodiment, the capacitor 24 is composed of two capacitors 24A and 24B connected in series. In this embodiment, lithium ion capacitors are used as these capacitors 24A and 24B, and both capacitors 24A and 24B have two plates having positive and negative polarities, respectively. The storage device 24 is filled with the negative side electrode plate 24C of the capacitor 24A connected to the low potential line 23 and the positive side electrode plate 24D of the capacitor 24B connected to the high potential line 26 described later. It is installed in the discharge circuit C1.

When the storage device 24 is viewed as a whole, the electric charge in the storage device 24 is charged between the negative side electrode plate 24C of the capacitor 24A and the positive side electrode plate 24D of the capacitor 24B. In such an embodiment, the negative electrode plate 24C of the capacitor 24A is connected to the first electrode plate connected to the low potential line 23 in the capacitor 24, and the positive electrode plate 24D of the capacitor 24B is the high potential line 26 in the capacitor 24. It corresponds to each of the second electrode plates connected to.

Further, the charge / discharge circuit C1 includes a chopper coil 25 which is a coil for boosting. One end of the chopper coil 25 is connected to the low potential line 23, and the other end is connected to the ground via the first switching element (hereinafter referred to as FET1) and the second switching element (hereinafter referred to as FET1). It is connected to the plate 24D, which is the second plate of the capacitor 24, via (referred to as FET 2). The above-mentioned high-potential line 26 is a wiring connecting the FET 2 and the electrode plate 24D.

In addition, the charge / discharge circuit C1 is between the discharge switch (hereinafter referred to as FET 3) interposed between the high potential line 26 and the output port 21 and the low potential line 23 and the output port 21. It has a charging switch (hereinafter referred to as FET 4), which is interposed in the above.

The charge / discharge circuit C1 is provided with a pull-up resistor 27. One end of the pull-up resistor 27 is connected to the input port 20 without going through the main relay 22, and the other end is connected to the high potential line 26. Further, a third switching element is located between the connection point of the pull-up resistor 27 in the high potential line 26 (hereinafter referred to as the charging upper point P1) and the electrode plate 24D which is the second pole of the capacitor 24. FET 9 is installed.

On the other hand, the bypass circuit C2 has a bypass line 28 which is a wiring connecting the input port 20 and the output port 21 by bypassing the charge / discharge circuit C1 and a relay provided on the bypass line 28 (hereinafter, bypass relay). 29) and. In the present embodiment, as the bypass relay 29, a non-contact relay composed of two switching elements (hereinafter, referred to as FET7 and FET8) is adopted.

Incidentally, in the present embodiment, the main relay 22, the bypass relay 29, the first to third switching elements, and the FETs 1 to FET 9 constituting the charging and discharging switches are all MOSFETs. The FETs 1 to 9 are switched between a closed state (on) and an open state (off) according to a drive signal output from the electronic control unit 14 to each gate.

The electronic control unit 14 acquires the potential of the above-mentioned charging upper point P1 as the charging upper point potential E1. Further, the electronic control unit 14 acquires the potential of the portion (relay rear stage point P2) between the FET 5 and the FET 6 in the main relay 22 as the relay rear stage potential E2. Further, the electronic control unit 14 acquires the potential of the output port 21 as the output port potential E3 and the potential of the charging midpoint P4 which is the connection point of the FET 1, the FET 2 and the chopper coil 25 as the charging midpoint potential E4.

Subsequently, the power supply control of the auxiliary power supply device 13 executed by the electronic control unit 14 will be described. The electronic control unit 14 performs a failure diagnosis of the auxiliary power supply device 13 after the vehicle is started (IG is turned on) and before the main relay 22 is closed (on) and power supply by the auxiliary power supply device 13 is started. Failure diagnosis is performed through four stages, the first to the fourth stages. Such a failure diagnosis before the start of power supply is started in a state where all FETs 1 to 9 are in an open state (off).

FIG. 3 shows the target of diagnosis at each stage of failure diagnosis, the operating state of each switching element (FET1 to FET9), and the potential (monitor potential) used for each diagnosis.
In the first stage of failure diagnosis before the start of power supply, short-circuit failure diagnosis of the main relay 22 (FET5, FET6) based on the relay post-stage potential E2 and short-circuit failure of the bypass relay 29 (FET7, FET8) based on the output port potential E3. Is diagnosed. In such a first stage diagnosis, the electronic control unit 14 outputs a drive signal for commanding an open state (off) to all of FETs 1 to 9, that is, a fully open command state for outputting an open command to all of FETs 1 to FET9. Will be done. Then, when the potential E2 in the subsequent stage of the relay is equal to or higher than the short circuit determination value α, it is diagnosed that the main relay 22 (FET5, FET6) has a short circuit failure. Further, when the output port potential E3 is equal to or higher than the short circuit determination value α, it is diagnosed that there is a short circuit failure of the bypass relays (FET7, FET8).

If a short-circuit failure has occurred in the main relay 22 (FET5, FET6) at this time, the relay subsequent stage potential E2 becomes a value close to the positive electrode potential (hereinafter, battery potential E0) of the vehicle-mounted battery 15. Further, if a short-circuit failure has occurred in the bypass relays 29 (FET7, FET8) at this time, the output port potential E3 becomes a value close to the battery potential E0. Therefore, as the short-circuit determination value α, a potential lower than the battery potential E0 and higher than the potential of the ground reference point (hereinafter referred to as the reference potential) is set in advance as the value.

When it is confirmed that a short-circuit failure has occurred in at least one of the main relay 22 and the bypass relay 29 in the first stage of such failure diagnosis, the electronic control unit 14 shifts to the fail-safe process, and so on. If not, move to the second stage of failure diagnosis. Upon transition from the first stage to the second stage, the electronic control unit 14 continues the fully open command state.

In the second stage, a short-circuit failure of the FET 2 is diagnosed based on the charging midpoint potential E4. Specifically, when the charging midpoint potential E4 is equal to or higher than the short-circuit determination value β, it is diagnosed that the FET 2 has a short-circuit failure. If a short-circuit failure of the FET 2 connected to the charging upper point P1 has occurred, the charging midpoint potential E4 becomes a value close to the charging upper point potential E1. In the auxiliary power supply device 13 of the present embodiment, the charging upper point P1 is pulled up by the pull-up resistor 27, and the charging upper point potential E1 at this time is a fixed value (hereinafter, referred to as a pull-up potential EP). It has become. Therefore, as the short-circuit determination value β, a potential lower than the pull-up potential EP and higher than the reference potential is set in advance as the value.

If it is confirmed that a short-circuit failure of the FET 2 has occurred in the second stage of the failure diagnosis, the electronic control unit 14 shifts to the fail-safe process, and if not, the electronic control unit 14 moves to the third stage of the failure diagnosis. Transition. Upon transition from the second stage to the third stage, the electronic control unit 14 switches the drive signal of the FET 2 from the signal for instructing the open state to the signal for instructing the closed state. Therefore, in the diagnosis of the third stage, the drive signal for instructing the closed state is output to the FET 2, that is, the closed command is output, and the open command is output to the other FETs 1 and FET 3 to FET 9. It is done in the state of being.

In the third stage, a short-circuit failure of the FET 1 is diagnosed based on the charging midpoint potential E4. Specifically, when the charging midpoint potential E4 is a value equal to or less than the short-circuit determination value γ, it is diagnosed that the FET 1 has a short-circuit failure. The charging midpoint potential E4 at this time becomes equal to the charging top point potential E1, that is, the pull-up potential EP by closing (on) the FET 2. On the other hand, if a short-circuit failure occurs in the FET 1 at this time, the charging midpoint potential E4 becomes a value close to the reference potential. Therefore, the short-circuit determination value γ is preset with a potential lower than the pull-up potential EP and higher than the reference potential.

If it is confirmed that a short-circuit failure of the FET 1 has occurred in the third stage of the failure diagnosis, the electronic control unit 14 shifts to the fail-safe process, and if not, the electronic control unit 14 moves to the fourth stage of the failure diagnosis. Transition. At the time of transition from the third stage to the fourth stage, the electronic control unit 14 switches the drive signal of the FET 1 from the signal for instructing the open state to the signal for instructing the closed state. Therefore, the diagnosis of the fourth stage is performed in a state where the closing command is output to the FET 1 and the FET 2, and the opening command is output to the other FETs 3 to 9.

In the fourth stage, the presence or absence of a normally open failure (open failure) of the FET 1 based on the charging midpoint potential E4 is diagnosed. Specifically, when the charging midpoint potential E4 is equal to or higher than the normally open determination value ε, it is diagnosed that the FET 1 has a normally open failure. Here, when the FET 1 does not have a normally open failure and the FET 1 is closed (on) in response to the closing command, the charging midpoint P4 is connected to the ground and the charging midpoint potential E4 is a pull-up potential. The value changes from a value close to EP to a value close to the reference potential. On the other hand, if the FET 1 at this time continues to be in the open state (off) due to a normally open failure, the charging midpoint potential E4 remains at a value close to the pull-up potential EP. Therefore, the normally open determination value ε is preset to have a potential lower than the short circuit determination value β and higher than the reference potential.

If the electronic control unit 14 is not diagnosed as having a failure in any of the first to fourth stages, the electronic control unit 14 starts power supply control. Then, the electronic control unit 14 switches the operating state of the auxiliary power supply device 13 between the holding state, the charging state, and the discharging state according to the battery power PS, the required power EPS, and the charging upper point potential E1. On the other hand, when the electronic control unit 14 diagnoses that there is a failure at any stage of the failure diagnosis, the electronic control unit 14 shifts to the fail-safe process regardless of the presence or absence of the unfinished stage. In the fail-safe process, the operating state of the auxiliary power supply device 13 is set to the fail-safe state described later.

FIG. 4 shows the driving states of the FETs 1 to 9 in each operating state of the holding state, the charging state, the discharging state, and the fail-safe state.
At the time of power supply control, the electronic control unit 14 first determines a target assisting force, which is a target value of the steering assisting force, based on the steering torque TR and the traveling speed VS. Subsequently, the electronic control unit 14 calculates the required power EPS, which is the power required for the assist motor 10 to generate the steering assist force corresponding to the target assist force. Then, the electronic control unit 14 is in the charging state, the holding state, and the discharging state according to the power supplied from the vehicle-mounted battery 15 to the auxiliary power supply device 13 (battery power PS), the required power EPS, and the charging upper point potential E1. To switch the operating state of the auxiliary power supply device 13.

The FETs 7 and FETs 8 constituting the bypass relay 29 are set to the open state (off) in any of the three operating states of the charging state, the holding state, and the discharging state, which are switched in the power supply control, and the FET 5 constituting the main relay 22 is set. , FET 6 is closed (on). Further, in any of the above three operating states, the FET 9 is set to the closed state (on). Therefore, the auxiliary power supply device 13 under power supply control is in a state of supplying power through the charge / discharge circuit C1 after shutting off the bypass circuit C2.

In the power supply control, the electronic control unit 14 keeps the operating state of the auxiliary power supply device 13 when the required power EPS is equal to or less than the main power supply power PS and the charging upper point potential E1 is equal to or higher than the specified maximum charging potential MAX. .. In the holding state, FET1, FET2, and FET3 are set to the open state (off), and FET4 is set to the closed state (on). At this time, a current flows from the vehicle-mounted battery 15 to the motor drive circuit 12 through the low potential line 23. Therefore, the output port potential E3 of the auxiliary power supply device 13 at this time has a value substantially equal to the battery potential E0. At this time, since both the FET 2 and the FET 3 are in the open state (off), the charges charged in the capacitors 24A and 24B up to that point are retained.

Further, in the power supply control, when the required power EPS is equal to or less than the battery power PS and the charging upper point potential E1 is less than the maximum charging potential MAX, the electronic control unit 14 sets the operating state of the auxiliary power supply device 13 to the charging state. In the charged state, the FET 3 is opened (off) and the FET 4 is closed (on). On the other hand, the FET 1 and the FET 2 at this time are PWM-driven so as to be alternately closed. Also at this time, since the current flows from the vehicle-mounted battery 15 to the motor drive circuit 12 through the low potential line 23, the output port potential E3 of the auxiliary power supply device 13 has a value substantially equal to the battery potential E0. Further, at this time, the PWM drive of the FET 1 and the FET 2 as described above boosts the charging upper point potential E1 and charges the capacitors 24A and 24B of the storage device 24 with electric charges.

Further, in the power supply control, when the required power EPS exceeds the battery power PS, the electronic control unit 14 sets the operating state of the auxiliary power supply device 13 to the discharged state. In the discharged state, FET1, FET2, and FET4 are set to the open state (off), and FET3 is set to the closed state (on). At this time, a current flows from the vehicle-mounted battery 15 to the motor drive circuit 12 through the low potential line 23, the capacitor 24, and the high potential line 26. Therefore, the output port potential E3 of the auxiliary power supply device 13 at this time has a charging upper point potential E1 higher than the battery potential E0.

As described above, in the present embodiment, the capacitors 24A and 24B are charged with electric charges when the required power EPS is small. Then, when the required power EPS becomes large, such as during stationary steering, the charged charge is discharged to increase the amount of power supplied to the assist motor 10 without increasing the amount of power supplied to the in-vehicle battery 15. I am trying to do it. Therefore, it is possible to generate a large steering assist force while suppressing a sudden decrease in the charge amount and a temperature rise of the vehicle-mounted battery 15 due to rapid discharge.

On the other hand, in the fail-safe state, which is the operating state of the auxiliary power supply device 13 when the process shifts to the fail-safe process, the FETs 1 to 6 and the FET 9 are set to the open state (off), and the FETs 5 and 6, that is, The bypass relay 29 is closed (on). At this time, power is supplied to the assist motor 10 through the bypass circuit C2 instead of the charge / discharge circuit C1 whose failure has been confirmed.

Subsequently, the operation of the present embodiment configured as described above will be described.
The charge / discharge circuit C1 of the auxiliary power supply device 13 is connected to the ground via the FET 1. If the main relay 22 is closed (on) in a state where a short-circuit failure occurs in the FET 1, both terminals of the vehicle-mounted battery 15 are connected to the ground and the terminals are short-circuited. As a result, the charge amount of the vehicle-mounted battery 15 may drop sharply, or the temperature of the vehicle-mounted battery 15 may rise due to heat generated by the sudden discharge. It is desirable to confirm the presence or absence of a failure of the FET 1 that causes a short circuit between the terminals of the vehicle-mounted battery 15 before starting the power supply of the auxiliary power supply device 13. In the auxiliary power supply device 13 of the present embodiment, the pull-up resistor 27 and the FET 9 are provided in the charge / discharge circuit C1 in order to diagnose the failure of the FET 1 before the start of such power supply.

When the pull-up resistor 27 and the FET 9 are not provided, the charging midpoint potential E4 before the start of power supply, that is, when the main relay 22 is in the open state (off) is undefined, so that the determination threshold value (short circuit) for the failure diagnosis of the FET 1 is undefined. Judgment value γ, normal open judgment value ε) cannot be determined. On the other hand, in the present embodiment, the charging upper point P1 and the input port 20 are connected via the pull-up resistor 27, and the charging upper point P1 and the capacitor 24 are disconnected with the FET 9 open (off). As a result, the charging top point potential E1 before the start of power supply is determined. Then, after confirming that a short-circuit failure has not occurred in the FET 2, the charging midpoint potential E4 is determined by closing (on) the FET 2. Therefore, it is possible to perform a failure diagnosis of the FET 1 even before the start of power supply.

If the charging midpoint potential E4 is simply determined, the pull-up resistor 27 may be directly connected to the charging midpoint P4 instead of the charging upper point P1. However, in such a case, the following problems arise.

When a short-circuit failure occurs in the main relay 22 and the FET 1 is closed (on) for diagnosis of a normally open failure, both terminals of the vehicle-mounted battery 15 pass through the short-circuited main relay 22, the chopper coil 25, and the FET 1. Is short-circuited. Therefore, it is desirable to confirm that a short-circuit failure of the main relay 22 has not occurred before performing a failure diagnosis of the FET 1.

However, when the charge / discharge circuit C1 is configured so as to connect the pull-up resistor 27 to the charging midpoint P4, both ends of the main relay 22 are connected via the pull-up resistor 27, and the main relay 22 is short-circuited. Even if a failure occurs, no current will flow to the relay post-stage point P2. Therefore, in such a case, it becomes impossible to confirm that a short-circuit failure has not occurred in the main relay 22 before the failure diagnosis of the FET 1. Therefore, it is more preferable to connect the pull-up resistor 27 to the charging upper point P1 on the high potential line 26 as in the present embodiment, so that the failure diagnosis of the FET 1 before the start of feeding can be performed in a more preferable state.

According to this embodiment, the following effects can be obtained.
(1) Failure diagnosis of FET1 before the start of power feeding can be performed in a state where the charging midpoint potential E4 is confirmed.

(2) Since it is possible to perform a failure diagnosis of the FET 1 after confirming that a short-circuit failure of the main relay 22 has not occurred, the short-circuited main relay 22 is used when the FET 1 is closed for diagnosis. It is possible to avoid short-circuiting both terminals of the vehicle-mounted battery 15 through the vehicle.

(3) Even when a failure occurs in the charge / discharge circuit C1, the power supply to the assist motor 10 can be continued through the bypass circuit C2 provided in parallel with the charge / discharge circuit C1.
The embodiment may be modified as follows.

In the above embodiment, the failure diagnosis is performed based on the relay rear stage potential E2, the output port potential E3, and the charging midpoint potential E4, but the current values of the relay rear stage point P2, the output port 21, and the charging midpoint P4 are acquired. At the same time, the failure diagnosis may be performed based on the acquired current values.

-In the electric power steering device 1 of the above embodiment, the bypass circuit C2 is provided in the auxiliary power supply device 13, but the bypass circuit C2 may be provided outside the auxiliary power supply device 13. Further, when the steering assist is stopped when the charge / discharge circuit C1 fails, the bypass circuit C2 may be omitted.

-In the above embodiment, the bypass circuit C2 is provided as a circuit for supplying power at the time of fail-safe when a failure occurs in the charge / discharge circuit C1. The power supply to the assist motor 10 in the holding state and the charging state in the power supply control may be performed through the bypass circuit C2. In such a case, the charge / discharge circuit C1 may have a configuration in which the charging switch (FET4) interposed between the low potential line 23 and the output port 21 is omitted.

-In the above embodiment, the in-vehicle battery 15 is the main power source for supplying power to the auxiliary power supply device 13, but a power source other than the in-vehicle battery such as a generator, or a combination of the in-vehicle battery and other power sources can be used. It may be used as the main power source.

-A mechanical relay may be adopted as the main relay 22 or the bypass relay 29.
A motor other than the three-phase brushless motor may be adopted as the assist motor 10.
-A part or all of the switching elements (FET1 to FET9) may be configured by switching elements other than MOSFETs.

-As the capacitors 24A and 24B of the auxiliary power supply device 13, a capacitor other than a lithium ion capacitor such as an electric double layer capacitor may be adopted.
The number of capacitors constituting the capacitor 24 of the auxiliary power supply device 13 can be appropriately changed, and the capacitor 24 may be configured by a single capacitor or three or more capacitors.

The electric power steering device 1 of the above embodiment is configured as a so-called column assist type electric power steering device in which an assist motor 10 is connected to a steering shaft 4 via a speed reducer 11. The electric power steering device 1 may be configured as a rack assist type device in which the assist motor 10 is connected to the rack shaft 5 via the speed reducer 11.

-The auxiliary power supply device 13 of the above embodiment may be applied to an electric device other than the electric power steering device 1.

1 ... Electric power steering device, 2 ... Steering wheel, 3 ... Pinion gear, 4 ... Steering shaft, 5 ... Rack shaft, 6 ... Rack gear, 7 ... Steering wheel, 8 ... Tie rod, 9 ... Torque sensor, 10 ... Assist motor ( Steering assistance motor), 11 ... Reducer, 12 ... Motor drive circuit, 13 ... Auxiliary power supply, 14 ... Electronic control unit, 15 ... In-vehicle battery (main power supply), 16 ... Arithmetic processing circuit, 17 ... Memory, 18 ... Vehicle speed sensor, 20 ... Input port, 21 ... Output port, 22 ... Main relay (relay), 23 ... Low potential line, 24 ... Storage unit, 24A, 24B ... Capacitor, 25 ... Chopper coil, 26 ... High potential line, 27 ... Pull-up resistance, FET1 to FET9 ... Switching element (FET1: 1st switching element, FET2: 2nd switching element, FET9: 3rd switching element), P1 ... Charging upper point (pull-up resistance in high potential line) Connection point), P2 ... Relay post-stage point, P4 ... Charging midpoint, E1 ... Charging upper point potential, E2 ... Relay post-stage potential, E3 ... Output port potential, E4 ... Charging midpoint potential, E5 ... Battery potential.

Claims (5)

In an auxiliary power supply device including an input port connected to a main power supply, an output port connected to a power supply target, and a charge / discharge circuit interposed between the input port and the output port.
The charge / discharge circuit is
A low-potential line, which is a wiring connected to the input port via a relay,
A capacitor capable of charging an electric charge between the first plate and the second plate, wherein the low potential line is connected to the first plate.
One end is connected to the low potential line, the other end is connected to the ground via the first switching element, and the other end is connected to the second electrode plate via the second switching element. With chopper coil,
When the wiring connecting the second switching element and the second electrode plate is a high potential line, one end is connected to the input port without the relay and the other end is connected to the high potential line. With the pull-up resistor
A third switching element installed in a portion between the connection point of the pull-up resistor and the second electrode plate in the high potential line, and
A discharge switch interposed between the high potential line and the output port,
Has an auxiliary power supply. The first step of diagnosing the presence or absence of a short-circuit failure of the relay in the fully open command state in which the open command is output to all of the relay, the discharge switch, and the first, second, and third switching elements.
After the implementation of the first step, the second step of diagnosing the presence or absence of a short-circuit failure of the second switching element while maintaining the fully open command state, and
After the execution of the second step, an open command is output to the relay, the discharge switch, and the first and third switching elements, respectively, and a close command is output to the second switching element. After that, the third step of diagnosing the presence or absence of a short-circuit failure of the first switching element, and
After the third step is performed, an open command is output to the relay, the discharge switch, and the third switching element, and a close command is output to the first and second switching elements, respectively. Then, the fourth step of diagnosing the presence or absence of a normally open failure of the first switching element, and
The auxiliary power supply device according to claim 1, wherein a failure diagnosis of the auxiliary power supply device is performed through the system. The auxiliary power supply device according to claim 1 or 2, further comprising a bypass circuit for passing a current from the input port to the output port by bypassing the charge / discharge circuit. The auxiliary power supply device according to any one of claims 1 to 3, wherein the charging / discharging circuit has a charging switch interposed between the low potential line and the output port. An electric power steering device comprising the auxiliary power supply device according to any one of claims 1 to 4 and a motor for steering assistance, and the motor is a power supply target of the auxiliary power supply device.

Images