JP6136309B2 - Auxiliary power supply apparatus and electric power steering apparatus provided with the apparatus - Google Patents

Description

  The present invention relates to an auxiliary power supply apparatus having an auxiliary power supply, and an electric power steering apparatus including the auxiliary power supply apparatus.

  A conventional electric power steering apparatus has an auxiliary power source connected to a main power source and a control device for controlling the operation of the auxiliary power source. The control device discharges the auxiliary power supply when the ignition switch is off. As a result, the charged amount of the auxiliary power source cell is set to “0”. That is, the auxiliary power source cell is initialized. Patent Document 1 shows an example of the configuration of a conventional electric power steering apparatus.

JP 2009-78744 A

  In the conventional electric power steering apparatus, the auxiliary power source cell is initialized on condition that the ignition switch is in the OFF state. For this reason, the conventional electric power steering apparatus does not consider initialization of the auxiliary power source cell when the ignition switch is in the on state, that is, during the vehicle operation period. Therefore, there is room for improvement in this respect.

  The present invention was created in view of such a background, and provides an auxiliary power supply device capable of initializing cells of an auxiliary power supply at an appropriate timing, and an electric power steering device including the same. For the purpose.

This means “has a plurality of cells capable of discharging to an electric motor supplied with power from a main power source, and includes an auxiliary power source in which the plurality of cells are connected in series to drive the electric motor. And a discharge circuit that initializes the voltage of each of the plurality of cells to 0V, which is formed separately from the motor driving circuit, connected in series with the auxiliary power source, and grounded. And a plurality of cells are discharged to initialize the plurality of cells when a voltage difference between a cell having a high voltage and a cell having the lowest voltage is equal to or greater than a threshold value.

  In the auxiliary power device, a plurality of cells are initialized when the voltage difference between the cell having the highest voltage and the cell having the lowest voltage is equal to or greater than a threshold value even when the ignition switch is on. Therefore, the auxiliary power source cell is initialized at a more appropriate timing.

Further, in the auxiliary power supply device, when the plurality of cells are initialized, the plurality of cells are discharged to the discharge circuit, and thus the plurality of cells are not discharged to the motor drive circuit. Therefore, a sudden change in the output of the electric motor at the time of initialization of a plurality of cells is suppressed.

One mode of the above means includes an “auxiliary power supply device in which the plurality of cells are not discharged to the discharge circuit when the plurality of cells are discharged to the electric motor”.
In the auxiliary power supply device, it is possible to suppress a decrease in the ability of the plurality of cells to discharge to the electric motor due to the discharge of the plurality of cells to the discharge circuit.

  One mode of the above means includes an “electric power steering apparatus including the electric motor that generates an assist torque based on a steering torque, the auxiliary power supply device, and a control device that controls the operation of the auxiliary power supply device”.

  One form of the above means is that “the auxiliary power supply device has a discharge circuit that is formed separately from a motor drive circuit for driving the electric motor and initializes the plurality of cells, and the control device includes: An electric power steering apparatus that does not discharge the plurality of cells to the discharge circuit when the plurality of cells are predicted to discharge to the electric motor based on the operation of the electric power steering apparatus;

When the electric power consumption of the electric motor increases based on the operation of the electric power steering device, it is preferable from the viewpoint of reducing the load of the main power source that a plurality of cells are discharged to the electric motor.
On the other hand, when a plurality of cells are discharged to the discharge circuit when the plurality of cells are discharged to the electric motor, the ability of the plurality of cells to discharge to the electric motor is reduced. This makes it difficult to reduce the load on the main power supply.

  Therefore, in this electric power steering apparatus, when it is predicted that a plurality of cells are discharged to the electric motor based on the operation of the electric power steering apparatus, the plurality of cells are not discharged to the discharge circuit. For this reason, the ability of the auxiliary power source to discharge to the electric motor due to the discharge of the plurality of cells to the discharge circuit is suppressed. Therefore, it is suppressed that the effect which reduces the load of a main power supply falls.

  The electric power steering apparatus and the auxiliary power supply apparatus can initialize the cell of the auxiliary power supply at an appropriate timing.

The block diagram which shows the structure of the electric power steering apparatus of embodiment. The circuit diagram showing the circuit composition of the electric power steering device of an embodiment. It is a graph of the electric power steering device of an embodiment, and is a graph which shows transition of EPS demand power. The flowchart which shows the process sequence of the power supply control which the control apparatus of the electric power steering apparatus of embodiment performs. The flowchart which shows the process sequence of the cell initialization control which the control apparatus of the electric power steering apparatus of embodiment performs.

With reference to FIG. 1, the configuration of an electric power steering apparatus (hereinafter referred to as “EPS1”) will be described.
The EPS 1 includes an EPS main body 10, an assist device 20, a control device 30, an auxiliary power supply device 40, and a torque sensor 50. In the EPS 1, the main power supply 4 and the vehicle speed sensor 5 are electrically connected to the control device 30. The EPS 1 has a configuration in which power is supplied to the assist device 20 from the battery serving as the main power source 4 and the auxiliary power device 40 via the control device 30. The EPS 1 assists the operation of the steering component 2 by the assist device 20. For example, a steering wheel is used as the steering component 2.

  The EPS main body 10 includes a column shaft 11, an intermediate shaft 12, a pinion shaft 13, a rack shaft 14, a rack and pinion mechanism 15, and two tie rods 16. The EPS main body 10 integrally rotates the column shaft 11, the intermediate shaft 12, and the pinion shaft 13 as the steering component 2 rotates. The EPS main body 10 changes the turning angle of the wheel 3 by reciprocating the rack shaft 14 by the rotation of the pinion shaft 13.

  The rack and pinion mechanism 15 has a configuration in which a pinion gear 13A of the pinion shaft 13 and a rack gear 14A of the rack shaft 14 are meshed with each other. The rack and pinion mechanism 15 converts the rotation of the pinion shaft 13 into the reciprocating movement of the rack shaft 14 by the engagement of the pinion gear 13A and the rack gear 14A.

  The assist device 20 includes an electric motor 21 as a three-phase brushless motor and a speed reduction mechanism 22 as a worm gear. The assist device 20 applies a force for rotating the column shaft 11 (hereinafter, “assist torque TA”) to the column shaft 11 by transmitting the rotation of the electric motor 21 to the column shaft 11 via the speed reduction mechanism 22. As described above, the EPS 1 has a column assist type configuration.

The torque sensor 50 transmits a torque signal to the control device 30 through the in-vehicle communication network.
The vehicle speed sensor 5 transmits a vehicle speed signal to the control device 30 through the in-vehicle communication network.

  Based on the torque signal from the torque sensor 50, the control device 30 twists the torsion bar 11A connected to the intermediate portion of the column shaft 11, that is, torque applied to the column shaft 11 as the steering component 2 is operated (hereinafter referred to as “ The magnitude and direction of the steering torque τ ”) are calculated. The control device 30 calculates the traveling speed of the vehicle (hereinafter “vehicle speed VS”) based on the vehicle speed signal of the vehicle speed sensor 5. The control device 30 controls the operation of the electric motor 21 to assist steering, and controls the operation of the auxiliary power supply 40 to control the power of the main power supply 4 and the power of the auxiliary power supply 40. Control and execute.

With reference to FIG. 2, configurations of the control device 30 and the auxiliary power supply device 40 will be described.
The control device 30 includes a microcomputer (hereinafter “microcomputer 31”), a motor drive circuit 34, a current sensor 35, and a voltage sensor 36. The control device 30 controls the voltage applied to the motor drive circuit 34 (hereinafter “motor drive voltage VMD”).

The current sensor 35 outputs a signal corresponding to the magnitude of the actual current (hereinafter “motor current IM”) supplied to the electric motor 21 to the motor control unit 33 of the microcomputer 31.
The voltage sensor 36 outputs a signal corresponding to the voltage between the auxiliary power supply device 40 and the motor drive circuit 34, that is, the magnitude of the motor drive voltage VMD, to the power management unit 32 of the microcomputer 31.

  The microcomputer 31 has a power management unit 32 and a motor control unit 33. The microcomputer 31 controls the charging / discharging operation of the auxiliary power supply device 40 in the power management unit 32. The microcomputer 31 controls the operation of the motor drive circuit 34 in the motor control unit 33.

  The power management unit 32 controls operations of the relay 41, the booster circuit 43, the charge / discharge circuit 44, and the discharge circuit 46 of the auxiliary power supply device 40. The power management unit 32 outputs a relay signal SR for controlling the operation of the relay 41 to the relay 41. The power management unit 32 outputs boost signals SB 1 and SB 2 for controlling the operation of the boost circuit 43 to the boost circuit 43. The power management unit 32 outputs charge / discharge signals SCD <b> 1 and SCD <b> 2 for controlling the operation of the charge / discharge circuit 44 to the charge / discharge circuit 44. The power management unit 32 outputs a discharge signal SD for controlling the operation of the discharge circuit 46 to the discharge circuit 46.

  The motor control unit 33 generates a motor control signal SM for executing assist control. Specifically, the motor control unit 33 calculates a target assist torque based on the steering torque τ and the vehicle speed VS. The motor control unit 33 generates the motor control signal SM by executing current feedback control so that the motor current IM matches the current command value corresponding to the target assist torque. The motor control unit 33 outputs a motor control signal SM to the motor drive circuit 34. The target assist torque increases as the absolute value of the steering torque τ increases or as the absolute value of the vehicle speed VS decreases.

  The motor drive circuit 34 has a known configuration in which two switching elements (MOSFETs) are connected in series to each phase of the electric motor 21. In the motor drive circuit 34, the on state and the off state of the two switching elements of each phase of the motor drive circuit 34 are alternately switched based on the motor control signal SM of the motor control unit 33. The motor drive circuit 34 applies the motor drive voltage VMD to the electric motor 21 as PWM drive by switching the ON state and the OFF state of each switching element.

  The auxiliary power supply 40 is formed separately from the main power supply 4. The auxiliary power supply 40 is connected in series with the main power supply 4. The auxiliary power supply device 40 includes a relay 41, a current sensor 42, a booster circuit 43, a charge / discharge circuit 44, a capacitor 45 as an auxiliary power supply, and a discharge circuit 46. The auxiliary power supply device 40 is discharged to the electric motor 21 via the control device 30 by the capacitor 45.

  The relay 41 is disposed between the main power supply 4 and the booster circuit 43. The relay 41 switches between an on state in which power is supplied to the motor drive circuit 34 from the main power supply 4 and an off state in which power is not supplied to the motor drive circuit 34 from the main power supply 4.

  The current sensor 42 is disposed between the relay 41 and the booster circuit 43. The current sensor 42 outputs a signal corresponding to the magnitude of the output current of the main power supply 4 (hereinafter “battery current IB”) to the power management unit 32.

  The booster circuit 43 boosts the output voltage based on the voltage of the main power supply 4 (battery voltage), that is, the output voltage at the connection point P1 between the main power supply 4 and the auxiliary power supply device 40 (hereinafter referred to as “output voltage VB”) to increase the capacitance. The capacitor 45 can be charged by being applied to a connection point P2 which is an output terminal of 45.

  The booster circuit 43 has a pair of switching elements 43A and 43B and a booster coil 43C. The booster circuit 43 has a configuration in which one end of a booster coil 43C is connected to a connection point P3 of a pair of switching elements 43A and 43B connected in series. The booster circuit 43 is applied with the output voltage VB at the other end of the booster coil 43C.

  MOSFETs are used for the pair of switching elements 43A and 43B. The switching element 43A on the upper stage side is connected to the output terminal (connection point P2) of the capacitor 45 at one end. The switching element 43A is connected to the lower switching element 43B at the other end. The lower switching element 43B is grounded at one end. Each of the switching elements 43A and 43B switches between an on state and an off state based on the boost signals SB1 and SB2 of the power management unit 32.

  The charge / discharge circuit 44 is connected in series with the booster circuit 43. The charge / discharge circuit 44 has a configuration in which a pair of switching elements 44A and 44B are connected in series. The charge / discharge circuit 44 is connected to the motor drive circuit 34 at a connection point P4 between the switching elements 44A and 44B.

  MOSFETs are used for the pair of switching elements 44A and 44B. The switching element 44A on the upper stage side is connected to the output terminal (connection point P2) of the capacitor 45 at one end. The other end of the switching element 44A is connected to the lower switching element 44B. The lower switching element 44B is electrically connected to the main power supply 4 via the current sensor 42 and the relay 41 at one end.

  Each of the switching elements 44A and 44B periodically switches between an on state that is a conducting state and an off state that is a non-conducting state based on the charge / discharge signals SCD1 and SCD2 of the power management unit 32. When the switching element 44A is in the ON state, the switching element 44A can discharge from the capacitor 45 to the motor drive circuit 34 (electric motor 21). When the switching element 44A is in the OFF state, the capacitor 45A cannot discharge from the capacitor 45 to the motor drive circuit 34 (electric motor 21). When the switching element 44B is in the ON state, the power can be supplied from the main power supply 4 to the motor drive circuit 34 (electric motor 21) via the switching element 44B. When the switching element 44B is in the OFF state, power cannot be supplied from the main power supply 4 to the motor drive circuit 34 (electric motor 21) via the switching element 44B.

  The capacitor 45 is connected in parallel with the booster circuit 43 and the charge / discharge circuit 44 between the booster circuit 43 and the charge / discharge circuit 44. The capacitor 45 is connected at one end to the connection point P2. The capacitor 45 is connected at the other end to a connection point P5 between the current sensor 42 and the switching element 44B. As the capacitor 45, an electric double layer capacitor is used.

  The capacitor 45 has a configuration in which four cells 45A to 45D are connected to each other in series. Cells 45A, 45B, 45C, and 45D are connected to capacitor 45 in order from the upper side to the lower side. In the capacitor 45, the difference between the voltage at the upper terminal of the cell 45A and the voltage at the lower terminal of the cell 45D is indicated as the voltage across the terminals of the capacitor 45 (hereinafter, “capacitor voltage VCT”).

  Each terminal of each of the cells 45A to 45D is connected to the microcomputer 31. The voltage between terminals of each of the cells 45 </ b> A to 45 </ b> D is measured using A / D conversion of the microcomputer 31. Hereinafter, the inter-terminal voltage of the cell 45A is indicated as “cell voltage VC1”. The voltage between the terminals of the cell 45B is indicated as “cell voltage VC2”. The voltage between the terminals of the cell 45C is shown as “cell voltage VC3”. The voltage between the terminals of the cell 45D is indicated as “cell voltage VC4”.

  Discharge circuit 46 is connected to capacitor 45 and charge / discharge circuit 44 at connection point P6. The discharge circuit 46 is connected in series with the capacitor 45. The discharge circuit 46 includes a switching element 46A and a resistor 46B. The discharge circuit 46 has a configuration in which a switching element 46A and a resistor 46B are connected in series with each other. The discharge circuit 46 has a configuration in which the switching element 46A is connected to one end of the resistor 46B and is grounded to the other end of the resistor 46B. The switching operation of the switching element 46A is controlled based on the discharge signal SD.

The operation of the relay 41 will be described.
The relay 41 is switched between an on state and an off state based on the relay signal SR of the power management unit 32. The relay 41 is switched from the off state to the on state when an ignition switch (not shown) of the vehicle is turned on. The relay 41 is switched from the on state to the off state when the ignition switch is turned off.

The operation of the booster circuit 43 will be described.
The booster circuit 43 applies a boosted voltage VR generated by switching the lower switching element 43B from the on state to the off state to the output terminal (connection point P2) of the capacitor 45. Specifically, in the booster circuit 43, the switching element 43B is turned on when it is turned on, and one end of the booster coil 43C is grounded. Then, the booster circuit 43 superimposes an induced voltage generated in the booster coil 43C when the switching element 43B is switched from the off state to the on state, and outputs the superimposed voltage on the output voltage VB. Note that the switching element 43A on the upper stage side has a function of preventing current wraparound (backflow) from the capacitor 45 side to the booster circuit 43 side.

The operation of the charge / discharge circuit 44 will be described.
The charging / discharging circuit 44 includes a first power supply configuration that supplies power from the main power supply 4 to the motor drive circuit 34 based on a combination of the on state and the off state of the switching elements 44A and 44B, and the main power supply 4 and the capacitor 45. The second power supply mode for supplying power to the motor drive circuit 34 is switched. The operations of the switching elements 44A and 44B are controlled by the power management unit 32 so that they are not simultaneously turned on.

  In the first power supply mode, the upper switching element 44A is turned off and the lower switching element 43B is turned on. In the first power supply mode, the battery current IB of the main power supply 4 is supplied to the capacitor 45 and supplied to the motor drive circuit 34 via the lower switching element 44B. In the first power supply mode, since the upper switching element 44A is in the OFF state, the capacitor 45 does not discharge to the motor drive circuit 34.

  In the second power supply mode, the upper switching element 44A is turned on and the lower switching element 44B is turned off. In the second power supply mode, the main power supply 4 and the capacitor 45 are connected in series. In the second power supply mode, the capacitor 45 is discharged to the motor drive circuit 34 in addition to the power supply to the motor drive circuit 34 by the main power supply 4.

  Further, in the second power supply configuration, the DUTY ratio that is the ratio of the ON state in one cycle of the switching element 44A and the DUTY ratio that is the ratio of the ON state in one cycle of the switching element 44B are other than 0% and 100%, respectively. Value is also adopted. The motor drive voltage VMD is changed by changing the DUTY ratio of each switching element 44A, 44B. Specifically, the motor drive voltage VMD increases as the DUTY ratio of the switching element 44A increases. When the DUTY ratio of the switching element 44A is 100%, the motor drive voltage VMD becomes the maximum value. When the DUTY ratio of the switching element 44A is 50%, the motor drive voltage VMD is half the maximum value. Further, the DUTY ratio of the switching element 44B decreases as the DUTY ratio of the switching element 44A increases.

The operation of the discharge circuit 46 will be described.
In the discharge circuit 46, the discharge of each of the cells 45A to 45D is started when the switching element 46A is switched from the off state to the on state. The discharge circuit 46 maintains the discharge until the voltage of each of the cells 45A to 45D becomes “0V”. In the discharge circuit 46, when the voltage of each of the cells 45A to 45D becomes “0 V”, the switching element 46A is switched from the on state to the off state. Note that the switching element 44 </ b> A of the charge / discharge circuit 44 is maintained in the OFF state over the period of discharge of the cells 45 </ b> A to 45 </ b> D by the discharge circuit 46. Thereby, it is suppressed that a voltage is applied to the motor drive circuit 34 by discharge of each cell 45A-45D.

  With reference to FIG. 3 and FIG. 4, the detailed content of power supply control is demonstrated. In the following description referring to FIG. 3 and FIG. 4, each constituent element related to the EPS 1 to which a reference numeral is attached indicates each constituent element described in FIG. 1 or FIG. 2.

  The “power supply power PS” indicates the actual power supplied from the main power supply 4 to the auxiliary power supply device 40 by the assist control of EPS1. The power source power PS is calculated based on the battery current IB. “Charge / discharge threshold KE” indicates a reference value for switching between charging from the main power supply 4 to the capacitor 45 and discharging from the capacitor 45 to the motor drive circuit 34 (electric motor 21). The charge / discharge threshold KE is set in advance by a test or the like.

  In FIG. 3, the power required for the main power supply 4 by the assist control of the EPS 1 (hereinafter referred to as “EPS required power”) is a period (hereinafter referred to as “discharge period”) that is greater than or equal to the charge / discharge threshold KE and less than the charge / discharge threshold KE. It is divided into periods.

  The power supply power PS is less than the charge / discharge threshold KE in a period where the EPS required power is less than the charge / discharge threshold KE. The power source power PS becomes equal to or higher than the charge / discharge threshold KE during the discharge period. The power supply power PS becomes larger than the charge / discharge threshold value KE in a period from the time t11, t12, t13 until the charge / discharge circuit 44 is switched from the first power supply mode to the second power supply mode, for example. An example of the case where the power source power PS is equal to or higher than the charge / discharge threshold value KE is that the driver performs the stationary steering of the steering component 2 when the vehicle is put in the garage or when the vehicle is parked.

  The power supply control controls the operation of the capacitor 45 based on the comparison between the power supply power PS and the charge / discharge threshold KE. The capacitor 45 discharges to the motor drive circuit 34 during the discharge period. Capacitor 45 is charged by main power supply 4 in a period less than charging / discharging threshold KE and in a period in which capacitor 45 is not fully charged (hereinafter referred to as “charging period”).

In the power control, the process shown in FIG. 4 is repeatedly executed at predetermined time intervals.
In step S11, control device 30 determines whether or not power supply power PS is equal to or higher than charge / discharge threshold KE. When the determination is affirmative in step S11, control device 30 sets charge / discharge circuit 44 to the second power supply configuration in step S12. And control device 30 performs discharge control which controls discharge of capacitor 45 in Step S13. Therefore, the EPS required power is supplemented by the discharge of the capacitor 45 with the amount of the EPS required power exceeding the charge / discharge threshold KE in addition to the power source power PS. Therefore, when power supply power PS is equal to or higher than charge / discharge threshold KE, power supply power PS (battery current IB) is peak-cut at charge / discharge threshold KE by discharge control. For this reason, the load of the main power supply 4 becomes small.

  On the other hand, when negative determination is made in step S11, control device 30 sets charge / discharge circuit 44 to the first power supply configuration in step S14. For this reason, the EPS required power is supplied by the power source power PS.

  Then, control device 30 determines whether or not capacitor 45 is fully charged in step S15. When the determination is affirmative in step S15, control device 30 determines that capacitor 45 need not be charged. And the control apparatus 30 once complete | finishes a process. On the other hand, control device 30 determines that capacitor 45 needs to be charged when a negative determination is made in step S15. And control device 30 performs charge control for charging capacitor 45 in Step S16.

The detailed contents of the discharge control will be described.
In the discharge control, the control device 30 performs the discharge of the capacitor 45 for the purpose of suppressing the capacity of the capacitor 45 from becoming insufficient when the charge / discharge circuit 44 is changed from the first power supply form to the second power supply form. Control like this.

  Control device 30 increases motor drive voltage VMD as the difference between power supply PS and charge / discharge threshold KE increases. Specifically, control device 30 increases the DUTY ratio of switching element 44A as the difference between power supply power PS and charge / discharge threshold KE increases.

  In addition, when changing the charge / discharge circuit 44 from the first power supply form to the second power supply form in the discharge control, the control device 30 suppresses a sudden change in the assist torque TA caused by a sudden change in the motor drive voltage VMD. For this purpose, the discharge of the capacitor 45 is controlled as follows.

  The control device 30 gradually increases the DUTY ratio of the switching element 44A with a predetermined increase width from the state where the DUTY ratio of the switching element 44A is 0%. Accordingly, the control device 30 gradually decreases the DUTY ratio of the switching element 44B from the state where the DUTY ratio of the switching element 44B is 100% by a predetermined decrease width. As a result, the motor drive voltage VMD gradually increases.

  The increase width of the DUTY ratio of the switching element 44A is determined based on the time constant of the transfer function in the power feedback control that is the PID control. The increase width of the DUTY ratio of the switching element 44A decreases as the time constant increases. The time constant is set in advance. The power feedback control indicates control for changing the motor drive voltage VMD so that the power supply power PS matches the charge / discharge threshold KE when the power supply power PS is larger than the charge / discharge threshold KE.

  By the way, by repeating charging / discharging of the capacitor 45 in the power supply control, the leakage current of each of the cells 45A to 45D varies. For this reason, the cell voltages VC1 to VC4 vary. When it is assumed that the capacitor 45 is charged so that a cell having a small voltage among the cell voltages VC1 to VC4 is fully charged in the charge control, a cell having a large voltage among the cell voltages VC1 to VC4 is a rated voltage of the cell. Higher voltage may be applied. Thereby, there exists a possibility that the performance of a cell may deteriorate. On the other hand, when it is assumed that the capacitor 45 is charged so that a cell having a small voltage among the cell voltages VC1 to VC4 is fully charged in the charge control, a cell having a small voltage among the cell voltages VC1 to VC4 is not fully charged. There is a case. As a result, the capacitor voltage VCT in the charge control may be lower than the voltage when the capacitor 45 is fully charged.

  Therefore, the control device 30 executes cell initialization control for initializing the cells 45A to 45D. Thereby, the dispersion | variation in each cell voltage VC1-VC4 is reduced. Therefore, it is suppressed that a voltage higher than the rated voltage of the cell is applied to each of the cells 45A to 45D and that each of the cells 45A to 45D is not fully charged.

With reference to FIG. 5, the process procedure of cell initialization control is demonstrated. This process is repeatedly executed every predetermined time.
Control device 30 acquires cell maximum voltage VCmax in step S21. Then, control device 30 acquires cell minimum voltage VCmin in step S22. Specifically, control device 30 acquires the largest cell voltage among cell voltages VC1 to VC4 as cell maximum voltage VCmax. The control device 30 acquires the smallest cell voltage among the cell voltages VC1 to VC4 as the cell minimum voltage VCmin.

  In step S23, control device 30 determines whether or not the difference between cell maximum voltage VCmax and cell minimum voltage VCmin is greater than or equal to cell voltage threshold value VCK. The cell voltage threshold value VCK is the minimum value of the voltage difference between cells that causes a voltage higher than the rated voltage to be applied to the cell when the capacitor 45 is completely charged and that the cell does not become fully charged. is there. The cell voltage threshold value VCK is preset by a test or simulation.

  When the determination in step S23 is affirmative, the control device 30 determines in step S24 whether EPS1 is in the stationary operation. Specifically, the control device 30 determines whether or not the vehicle speed VS is equal to or less than the vehicle speed threshold value VSK. When the vehicle speed VS is equal to or lower than the vehicle speed threshold value VSK, the control device 30 determines that the EPS 1 is in the stationary operation. When the vehicle speed VS is higher than the vehicle speed threshold value VSK, the control device 30 determines that the EPS 1 is not in the stationary operation.

  When a negative determination is made in step S24, control device 30 initializes cells 45A to 45D in step S25. Specifically, the switching element 46A of the discharge circuit 46 is turned on. Thereby, each of the cells 45 </ b> A to 45 </ b> D is discharged to the discharge circuit 46. For this reason, the voltage of each of the cells 45A to 45D is “0V”.

  On the other hand, when the determination is affirmative in step S24, the control device 30 once ends the process. That is, the control device 30 does not initialize the cells 45A to 45D during the stationary operation.

The operation of the EPS 1 of this embodiment will be described. Note that “virtual EPS” initializes the cell when the ignition switch is in the OFF state, instead of the cell initialization control.
Virtual EPS does not initialize the cell when the ignition switch is on. For this reason, in the virtual EPS, charging / discharging of the cell is repeated in a state where the cell is not initialized over a period in which the ignition switch is on. Therefore, in virtual EPS, a voltage larger than the rated voltage may be applied to the cell. Thereby, the performance of the cell may deteriorate.

  On the other hand, the EPS 1 of the present embodiment performs initialization of each of the cells 45A to 45D when the difference between the cell maximum voltage VCmax and the cell minimum voltage VCmin is equal to or greater than the cell voltage threshold VCK in the cell initialization control. That is, the EPS 1 of the present embodiment can initialize each of the cells 45A to 45D even when the ignition switch is on. For this reason, it is suppressed that the voltage larger than the rated voltage of a cell is applied to each cell 45A-45D.

  However, when it is assumed that the control device 30 has initialized each of the cells 45A to 45D while the EPS 1 is in the stationary operation, the capacitor 45 cannot be discharged when the power supply power PS becomes equal to or higher than the charge / discharge threshold KE. For this reason, an appropriate steering assist cannot be executed while the EPS 1 is stationary.

  Therefore, the EPS 1 of the present embodiment does not initialize the cells 45A to 45D when the EPS 1 is in the stationary operation in the cell initialization control. Accordingly, appropriate steering assist is executed during the stationary operation of EPS1. On the other hand, the EPS1 stationary operation is almost always shorter than the period in which the ignition switch is on. For this reason, compared with virtual EPS, the control apparatus 30 becomes frequent the frequency which initializes each cell 45A-45D.

The EPS 1 of the present embodiment has the following effects.
(1) The control device 30 initializes each of the cells 45A to 45D when the difference between the cell maximum voltage VCmax and the cell minimum voltage VCmin is equal to or greater than the cell voltage threshold value VCK. According to this configuration, when the capacitor 45 is charged, it is suppressed that a voltage larger than the rated voltage of the cell is applied to each of the cells 45A to 45D. Further, when the capacitor 45 is charged, the cells 45A to 45D are prevented from being fully charged.

  (2) The auxiliary power supply device 40 includes a discharge circuit 46 formed separately from the motor drive circuit 34. According to this configuration, the cells 45A to 45D are prevented from being discharged to the motor drive circuit 34 when the cells 45A to 45D are initialized. For this reason, when the cells 45A to 45D are initialized, the assist torque TA is prevented from changing suddenly. Therefore, a decrease in steering feeling is suppressed.

  (3) The control device 30 does not initialize the cells 45A to 45D when the EPS 1 is in the stationary operation. According to this configuration, the ability of the capacitor 45 to discharge to the motor drive circuit 34 when the power supply power PS becomes equal to or higher than the charge / discharge threshold KE is suppressed. For this reason, it is suppressed that the effect of the peak cut of the main power supply 4 falls during EPS1 stationary operation.

  The electric power steering device and the auxiliary power supply device include an embodiment different from the above embodiment. Hereinafter, modifications of the above-described embodiment as other embodiments of the electric power steering device and the auxiliary power supply device will be described. The following modifications can be combined with each other.

  -The control apparatus 30 of embodiment determines whether charging control is performed based on whether the capacitor 45 is fully charged in power supply control (step S15). However, the determination of whether or not to execute the charging control is not limited to the content exemplified in the embodiment. For example, the control device 30 according to the modified example determines whether or not to execute the charge control based on whether or not the capacitor voltage VCT is equal to or higher than a predetermined voltage threshold lower than the full charge, instead of the content of step S15 in the power supply control. judge. The control device 30 according to the modification does not execute the charge control when the capacitor voltage VCT is equal to or higher than the voltage threshold. The control device 30 according to the modification executes charge control when the capacitor voltage VCT is less than the voltage threshold.

  The control device 30 of the embodiment determines that EPS1 is in the stationary operation when the vehicle speed VS is equal to or less than the vehicle speed threshold value VSK in step S23 of the cell initialization control. However, the determination whether the EPS 1 is in the stationary operation is not limited to the content exemplified in the embodiment. For example, when the vehicle speed VS is equal to or lower than the vehicle speed threshold value VSK and the steering torque τ is equal to or higher than the torque threshold value τK in step S23 of the cell initialization control, the control device 30 according to the modification determines that EPS1 is in the stationary operation. The torque threshold τK is the minimum value of the steering torque τ during the stationary operation. The torque threshold τK is preset by a test or simulation. Further, the control device 30 of another modified example determines that the EPS 1 is in the stationary operation when the steering torque τ is equal to or greater than the torque threshold value τK.

  -The control apparatus 30 of embodiment does not initialize each cell 45A-45D, when EPS1 is performing a stationary operation in cell initialization control. However, the conditions for not initializing the cells 45A to 45D are not limited to the contents exemplified in the embodiment. For example, instead of the content of step S24 of the cell initialization control, the control device 30 according to the modification determines whether the power source power PS is equal to or higher than the charge / discharge threshold KE. And the control apparatus 30 of a modification does not initialize each cell 45A-45D, when the power supply electric power PS is more than the charging / discharging threshold value KE, ie, when the capacitor 45 discharges to the motor drive circuit 34 (electric motor 20).

  In addition, the control device 30 of another modified example determines whether or not the power supply power PS is predicted to be equal to or higher than the charge / discharge threshold KE, instead of the content of step S24 of the cell initialization control. And control device 30 of another modification does not initialize each cell 45A-45D, when it is predicted that power supply electric power PS will become more than charging / discharging threshold value KE. Note that the prediction that the power supply power PS is equal to or higher than the charge / discharge threshold KE includes a case where the power increase speed, which is the increase speed of the power supply power PS, is equal to or higher than the increase speed threshold. The increase speed threshold value is the minimum value of the increase speed of the power source power PS during the stationary operation or the minimum value of the increase speed of the power source power PS when the vehicle travels in slalom. The increase speed threshold is preset by a test or simulation.

  In the control device 30 of the embodiment, the operation of the discharge circuit 46 is controlled by the power management unit 32. However, the configuration of the control device 30 is not limited to the content exemplified in the embodiment. For example, in the control device 30 of the modification, the operation of the discharge circuit 46 is controlled by a discharge control unit formed separately from the power management unit 32.

  The auxiliary power device 40 of the embodiment has one discharge circuit 46. However, the number of discharge circuits 46 is not limited to the content exemplified in the embodiment. For example, in the auxiliary power supply device 40 according to the modification, a discharge circuit 46 is connected to each of the cells 45A to 45D.

  In the auxiliary power device 40 according to the embodiment, the discharge circuit 46 can be omitted. In this case, the control device 30 discharges the cells 45A to 45D to the motor drive circuit 34 when initializing the cells 45A to 45D.

  The auxiliary power supply device 40 according to the embodiment includes a capacitor 45. However, the configuration of the auxiliary power supply device 40 is not limited to the content exemplified in the embodiment. For example, the auxiliary power supply device 40 according to the modified example has a secondary battery such as a lithium ion battery instead of the capacitor 45.

  In the embodiment, the capacitor 45 is an electric double layer capacitor. However, the type of the capacitor 45 is not limited to the content exemplified in the embodiment. For example, the capacitor 45 of the modified example is a lithium ion capacitor instead of an electric double layer capacitor.

  The electric motor 21 of the embodiment has a configuration of a three-phase brushless motor. However, the configuration of the electric motor 21 is not limited to the content exemplified in the embodiment. For example, the modified electric motor 21 has a configuration of a motor with a brush.

In the auxiliary power device 40 of the embodiment, a plurality of capacitors 45 may be included.
-The auxiliary power supply 40 of embodiment is applied to EPS1. However, the application range of the auxiliary power supply 40 is not limited to EPS1. For example, the auxiliary power supply device 40 according to the modification is applied to a machine tool.

  The EPS 1 of the embodiment has a column assist type configuration. However, the configuration of the EPS 1 is not limited to the content exemplified in the embodiment. For example, the modified EPS 1 has a pinion assist type, dual pinion assist type, rack coaxial type, or rack parallel type configuration. Another modified EPS 1 has a steer-by-wire configuration.

Next, technical ideas that can be grasped from the above-described embodiment will be described together with effects.
(B) The electric power steering apparatus according to claim 4 or 5, wherein the control device does not discharge the plurality of cells to the discharge circuit when the plurality of cells are predicted to be discharged to the electric motor.

  In the electric power steering apparatus, the plurality of cells are not actually being discharged to the electric motor, and the plurality of cells are not discharged to the discharge circuit when it is predicted that the plurality of cells are discharged. Thereby, when the auxiliary power source is discharged to the electric motor, the amount of power stored in the auxiliary power source is further suppressed.

  (B) The electric power steering device according to claim 4 or 5, wherein when the electric power steering device performs a stationary operation, the control device does not discharge the plurality of cells to the discharge circuit.

  When the electric power steering device performs the stationary operation, the electric power consumption of the electric motor increases, and the possibility that the auxiliary power source is discharged to the electric motor increases. In such a case, if a plurality of cells are initialized, the ability of the auxiliary power source to discharge to the electric motor is reduced.

  On the other hand, in the electric power steering apparatus, when the electric power steering apparatus is stationary, a plurality of cells are not discharged to the discharge circuit. Therefore, a decrease in the ability of the auxiliary power source to discharge to the electric motor is suppressed.

  DESCRIPTION OF SYMBOLS 1 ... EPS (electric power steering device), 4 ... Main power supply, 21 ... Electric motor, 30 ... Control device, 34 ... Motor drive circuit, 40 ... Auxiliary power supply device, 45 ... Capacitor (auxiliary power supply), 45A ... Cell, 45B ... cell, 45C ... cell, 45D ... cell, 46 ... discharge circuit, τ ... steering torque, TA ... assist torque, VCmax ... maximum cell voltage, VCmin ... minimum cell voltage, VCK ... cell voltage threshold (threshold).

Claims (4)

It has a plurality of cells that can be discharged to an electric motor supplied with power from a main power source, and includes an auxiliary power source in which the plurality of cells are connected in series with each other,
A motor driving circuit for driving the electric motor is formed separately, connected in series with the auxiliary power supply, grounded, and has a discharge circuit that initializes each voltage of the plurality of cells to 0V,
When the voltage difference between the cell having the highest voltage and the cell having the lowest voltage among the plurality of cells is equal to or greater than a threshold value, the plurality of cells are discharged and the plurality of cells are initialized. When said plurality of cells are discharged to the electric motor, the auxiliary power supply device according to claim 1, wherein the plurality of cells is not discharged to the discharge circuit. The electric motor for generating an assist torque based on the steering torque;
An auxiliary power supply device according to claim 1 or 2 ,
An electric power steering apparatus comprising: a control device that controls the operation of the auxiliary power supply device. The auxiliary power supply is formed separately from a motor drive circuit for driving the electric motor, and has a discharge circuit for initializing the plurality of cells,
The electric power according to claim 3 , wherein the control device does not discharge the plurality of cells to the discharge circuit when the plurality of cells are predicted to be discharged to the electric motor based on an operation of the electric power steering device. Steering device.