JP6256092B2 - Steering device and its control device - Google Patents

Description

  The present invention relates to a steering device having an auxiliary power source and a control device therefor.

  A conventional steering device includes an assist motor that applies torque to the steering shaft, a power that is supplied from the main power source to the assist motor, and a control device that controls the output of the assist motor.

  The control device calculates a required output, which is an output required for the assist motor, based on a torque acting on the steering wheel, and calculates a required power, which is an electric power required for the main power source, based on the required output. Based on this required power, the power supply power that is the power supplied from the main power supply to the assist motor is controlled. As the required output of the assist motor increases, the power supply power also increases. For example, when a large load is applied to the steering device that constitutes the steering device, the main power source discharge amount increases excessively. The remaining capacity of the battery may be reduced to a level that reduces the life of the main power supply.

  In order to solve such problems, the improved conventional steering apparatus further includes an auxiliary power source that boosts the power of the main power source and supplies it to the assist motor, and the electric power of the assist motor, the main power source, and the auxiliary power source. A circuit for switching the general connection relationship.

  The control device of the steering device selects a power supply form to the assist motor as follows based on the relationship between the power source power and the charge / discharge threshold. When the power supply power is less than the charge / discharge threshold, the control device sets the circuit so that only the main power supply of the main power supply and the auxiliary power supply is supplied to the motor, and the auxiliary power supply is charged by the power of the main power supply. Set. On the other hand, when the power source power is equal to or higher than the charge / discharge threshold, the control device sets the circuit so that the power of the main power source is boosted by the auxiliary power source and the boosted power is supplied to the motor.

  When the auxiliary power supply boosts the power of the main power supply and supplies it to the assist motor, the discharge amount of the main power supply becomes smaller than when only the main power supply supplies power to the assist motor. Therefore, even if the power supply mode is switched as described above, the power source power is equal to or higher than the charge / discharge threshold, that is, the discharge amount of the main power source may become excessively large. The amount of discharge is suppressed. For this reason, it is difficult for the lifetime to decrease due to the decrease in the remaining capacity of the main power source. Patent Document 1 discloses an example of a steering device having the main power source and the auxiliary power source as described above.

JP 2008-265381 A

  For example, when a large load is applied to the steering device, such as when the steering wheel is stationary, the required power of the main power supply becomes particularly large. In such a case, when the auxiliary power source boosts the power of the main power source and supplies it to the assist motor, the discharge amount of the auxiliary power source increases. When the internal resistance of the auxiliary power supply is high, the discharge amount that the auxiliary power supply actually discharges becomes larger than the required discharge amount of the auxiliary power supply due to the loss due to the resistance. For this reason, there is a possibility that the remaining capacity of the auxiliary power source may be reduced to a level that reduces the life of the auxiliary power source.

  An object of the present invention is to provide a steering device in which the life of an auxiliary power source is unlikely to decrease, and a control device for the steering device.

  [1] According to an independent form of the control device of the present steering device, an assist motor that applies torque to the steering shaft, an auxiliary power source that is charged by power of a main power source that supplies power to the assist motor, A control device that controls a steering device having a power source, the auxiliary power source, and a circuit that switches an electrical connection relationship of the assist motor, wherein the main power source is power supplied to the steering device. Based on being less than the charge / discharge threshold, the circuit is set so that the power of the main power supply is supplied to the assist motor without being boosted by the auxiliary power supply, and the power supply power is equal to or higher than the charge / discharge threshold. On the other hand, the power of the main power source is boosted by the auxiliary power source, and the boosted power is boosted by the assist power source. Setting the circuit to be supplied to the over data, the charging and discharging threshold when the temperature of the auxiliary power supply is low, the set larger than the charge-discharge threshold value when the temperature of the auxiliary power supply is high.

  The internal resistance of the auxiliary power supply varies depending on various factors, and the internal resistance increases mainly as the temperature of the auxiliary power supply decreases. The internal resistance of the auxiliary power supply when the temperature of the auxiliary power supply is low is larger than the internal resistance of the auxiliary power supply when the temperature of the auxiliary power supply is high. For this reason, when the temperature of the auxiliary power supply is low, the discharge amount of the auxiliary power supply may become excessively large.

  On the other hand, since the present control device has the configuration [1], when the temperature of the auxiliary power supply is low and the internal resistance of the auxiliary power supply is estimated to be large, the charge / discharge threshold is set large. For this reason, compared with the case where a charging / discharging threshold value is not set like that, the situation where power supply electric power has a magnitude | size beyond a charging / discharging threshold value becomes difficult to arise. For this reason, when there is a possibility that the discharge amount of the auxiliary power source becomes excessively large due to the large internal resistance of the auxiliary power source, the opportunity for the auxiliary power source to discharge is reduced. For this reason, it becomes difficult for the lifetime of an auxiliary power supply to fall.

  [2] According to an embodiment dependent on the control device of the steering device, the charge / discharge threshold value when the temperature of the auxiliary power source is included in a low temperature range that is lower than the first temperature is set to the auxiliary power source. Is set to be larger than the charge / discharge threshold when the temperature is included in a high temperature range that is a temperature range equal to or higher than a second temperature higher than the first temperature, and the temperature of the auxiliary power source is equal to or higher than the first temperature and the The charge / discharge threshold when included in the intermediate temperature range that is a temperature range lower than the second temperature is set to the charge / discharge threshold when the temperature of the auxiliary power source is included in the high temperature range as the temperature of the auxiliary power source decreases. The temperature of the auxiliary power source is increased from the discharge threshold toward the charge / discharge threshold when the temperature is included in the low temperature range.

  The relationship between the internal resistance of the auxiliary power supply and the temperature of the auxiliary power supply includes a region where the internal resistance of the auxiliary power supply increases with a large inclination as the temperature of the auxiliary power supply decreases. On the other hand, the setting form of the charge / discharge threshold by the control device of [1] is, for example, that the charge / discharge threshold is set large when the temperature of the auxiliary power source is lower than the second temperature, and the temperature of the auxiliary power source is equal to or higher than the second temperature. In some cases, the charging / discharging threshold is reduced.

  According to this setting mode, since the relationship between the internal resistance of the auxiliary power supply and the temperature of the auxiliary power supply is not sufficiently reflected, the charging / discharging threshold is set large despite the small internal resistance of the auxiliary power supply. May be. For this reason, when it is preferable to boost the power of the main power supply by the auxiliary power supply, the power of the main power supply is not boosted as such, and the burden on the main power supply increases.

  On the other hand, since the present control device has the configuration of [2] above, the intermediate temperature range is associated with a region where the internal resistance of the auxiliary power source increases with a large slope as the temperature of the auxiliary power source decreases, thereby charging / discharging threshold value. The relationship between the internal resistance of the auxiliary power supply and the temperature of the auxiliary power supply is appropriately reflected in the relationship between the temperature of the auxiliary power supply and the auxiliary power supply. For this reason, it is suppressed that the burden of the main power supply becomes large.

  [3] According to an embodiment dependent on the control device of the steering device, the charge / discharge threshold is changed according to the remaining capacity of the auxiliary power supply in addition to the temperature of the auxiliary power supply, and the remaining capacity of the auxiliary power supply is changed. When the remaining capacity of the auxiliary power source is less than a predetermined remaining amount, the charging / discharging threshold value is set larger than when the remaining capacity of the auxiliary power source is greater than or equal to the predetermined remaining amount.

  The smaller the remaining capacity of the auxiliary power source, the higher the risk that the remaining capacity will decrease to a level that reduces its life as the auxiliary power source is discharged. On the other hand, since the present control device has the configuration of [3] above, the power supply power has a magnitude equal to or greater than the charge / discharge threshold as compared with the case where the charge / discharge threshold is not set according to the remaining capacity of the auxiliary power supply. Is less likely to occur. For this reason, when there is a possibility that the remaining capacity of the auxiliary power source may be excessively reduced, the chance of the auxiliary power source being discharged is reduced. For this reason, it becomes difficult for the lifetime of an auxiliary power supply to fall.

  [4] According to an embodiment dependent on the control device of the steering device, when the remaining capacity of the auxiliary power source is equal to or lower than a lower limit value of the remaining capacity of the auxiliary power source, the power source power is equal to or higher than the charge / discharge threshold value. Based on the above, the circuit is set so that the power of the main power is supplied to the assist motor in a state where the power of the main power is not boosted by the auxiliary power, and the power is less than the charge / discharge threshold. Based on the fact, the circuit is set so that the auxiliary power supply is charged by the power of the main power supply.

  [5] According to an independent form of the present steering device, the control device is included.

  According to the present control device and the present steering device, it is difficult for the life of the auxiliary power source to decrease.

The block diagram of the steering device of embodiment. The block diagram which shows the circuit structure of the steering apparatus of embodiment. The table | surface which shows the operation state of each switching element of embodiment. It is a circuit diagram which shows operation | movement of each switching element of embodiment, and the flow of electric power, (a) is a circuit diagram of a 1st output state, (b) is a circuit diagram of a 2nd output state, (c) is a 3rd output. The circuit diagram of a state. The graph which shows transition of the request | requirement electric power and power supply power of embodiment. The graph which shows the relationship between the temperature of a capacitor, and the internal resistance of a capacitor. The map which shows the relationship between the charging / discharging threshold value of embodiment, and the temperature of a capacitor. The graph which shows the relationship between the remaining capacity of the capacitor of embodiment, and the number of stationary steerings. The flowchart which shows the process sequence of the power supply control of embodiment.

With reference to FIG. 1, the structure of the steering apparatus 1 comprised as a column assist type electric power steering apparatus is demonstrated.
The steering device 1 includes a steering mechanism 10 to which a steering wheel 2 is connected, a steering mechanism 20 that is connected to the steering mechanism 10 and steers the steered wheels 3, an assist mechanism 30 that assists the operation of the steering wheel 2, and an assist. An auxiliary power supply device 50 for applying a voltage to the assist motor 31 of the mechanism 30 is provided. The steering device 1 is connected to a main power supply 4 that supplies power to the assist mechanism 30 and the auxiliary power supply device 50 and a vehicle speed sensor 5 that outputs a signal corresponding to the rotational speed of the steered wheels 3.

  The steering mechanism 10 has a steering shaft 11 that serves as a rotating shaft of the steering wheel 2. The steering shaft 11 has a column shaft 12 to which the steering wheel 2 is connected, an intermediate shaft 13 connected to the lower end portion of the column shaft 12, and a pinion shaft 14 connected to the lower end portion of the intermediate shaft 13. ing. The column shaft 12 has a torsion bar 12A. A torque sensor 15 that outputs a signal corresponding to the torsion amount of the torsion bar 12A is attached to the column shaft 12. Teeth 14 </ b> A are formed in the lower part of the pinion shaft 14.

  The steered mechanism 20 has a rack shaft 21. Both end portions of the rack shaft 21 are connected to the steered wheels 3 via tie rods 23 and the like. A tooth 21 </ b> A is formed on a part of the rack shaft 21. The teeth 14 </ b> A of the pinion shaft 14 and the teeth 21 </ b> A of the rack shaft 21 constitute a rack and pinion mechanism 22 by being meshed with each other.

  According to the steering mechanism 10 and the steering mechanism 20, when the steering wheel 2 is operated, the column shaft 12, the intermediate shaft 13, and the pinion shaft 14 rotate integrally. The rotational movement of the pinion shaft 14 is converted into movement in the longitudinal direction of the rack shaft 21 via the rack and pinion mechanism 22. As the rack shaft 21 moves, the steered wheels 3 are steered through the tie rods 23 and the like.

  The assist mechanism 30 is attached to the column shaft 12. The assist mechanism 30 includes an assist motor 31 that generates assist torque that assists the operation of the steering wheel 2, a speed reducer 32 that decelerates rotation of the output shaft of the assist motor 31, and a control device 40 that controls the assist motor 31. doing. An example of the assist motor 31 is a three-phase brushless motor. An example of the speed reducer 32 is a worm gear including a worm shaft and a worm wheel that mesh with each other. The output shaft of the assist motor 31 is connected to the worm shaft. The worm wheel is connected to the column shaft 12. The control device 40 is electrically connected to the main power supply 4, the vehicle speed sensor 5, the auxiliary power supply device 50, the torque sensor 15, and the assist motor 31. The control device 40 calculates a steering torque (hereinafter, “steering torque τ”) according to the driver's steering based on the signal from the torque sensor 15, and calculates the vehicle speed VS based on the signal from the vehicle speed sensor 5. . The control device 40 executes assist control for controlling driving of the assist motor 31 and power control for controlling the charging / discharging operation of the auxiliary power device 50.

  According to the assist mechanism 30, assist torque is applied to the column shaft 12 as follows. That is, the control device 40 calculates the assist torque according to the driver's steering based on the steering torque τ and the vehicle speed VS by the assist control. The control device 40 controls driving of the assist motor 31 based on the assist torque. When the assist motor 31 is driven, the output shaft of the assist motor 31 rotates. The rotational torque of the output shaft of the assist motor 31 is applied to the column shaft 12 via the speed reducer 32.

With reference to FIG. 2, the structure of the control apparatus 40 and the auxiliary power supply apparatus 50 is demonstrated.
The control device 40 includes a microcomputer 41 for controlling the assist motor 31 and the auxiliary power supply device 50, and a motor drive circuit 44 for controlling electric power supplied to the assist motor 31.

  The microcomputer 41 supplies to the motor drive circuit 44 a power management unit 42 that controls the charging / discharging operation of the auxiliary power supply 50 as power control and a motor control signal SM for generating assist torque of the assist motor 31 as assist control. A motor control unit 43 for outputting is provided. The motor control unit 43 is input with the vehicle speed VS and the steering torque τ.

The motor drive circuit 44 has a known configuration in which two switching elements are connected in series for each phase of the assist motor 31.
The auxiliary power supply device 50 is connected in series with the main power supply 4. The auxiliary power supply 50 includes a capacitor 51 as an auxiliary power supply, a booster circuit 52 that boosts the voltage of the main power supply 4 (hereinafter, “battery voltage VB”) and applies the boosted voltage to the capacitor 51, and the main power supply 4, the capacitor 51, and The charging / discharging circuit 53 is a circuit for switching the electrical connection relationship of the motor drive circuit 44. The charge / discharge circuit 53 switches charging from the main power supply 4 to the capacitor 51 and discharging from the capacitor 51 to the motor drive circuit 44.

  In addition, the auxiliary power supply 50 responds to the temperature of the capacitor 51 and the current sensor 54 that outputs a signal corresponding to the output current of the main power supply 4 (hereinafter, “battery current IB”) to the power management unit 42. A temperature sensor 55 for outputting the received signal to the power management unit 42. An example of the temperature sensor 55 is a thermistor. The temperature sensor 55 is disposed in a portion adjacent to the capacitor 51 in the auxiliary power supply device 50.

An example of the capacitor 51 is a lithium ion capacitor. Capacitor 51 is connected in parallel with booster circuit 52 and charge / discharge circuit 53.
The booster circuit 52 has switching elements 52A and 52B and a booster coil 52C. An example of the switching elements 52A and 52B is a MOSFET. The upper switching element 52A is connected to each of the capacitor 51 and the lower switching element 52B. The lower switching element 52B is connected to the ground. One end of the step-up coil 52C is connected to a connection point between the switching element 52A and the switching element 52B. The other end of the booster coil 52C is connected to the main power supply 4.

  The boost signal SB1 of the power management unit 42 is input to the gate portion of the switching element 52A. The boost signal SB2 of the power management unit 42 is input to the gate portion of the switching element 52B. The switching elements 52A and 52B are PWM driven based on the boost signals SB1 and SB2.

  The charge / discharge circuit 53 is connected in series with the booster circuit 52. The charge / discharge circuit 53 includes switching elements 53A and 53B. An example of the switching elements 53A and 53B is a MOSFET. The upper switching element 53A is connected to each of the capacitor 51 and the lower switching element 53B. The lower switching element 53 </ b> B is connected to the main power supply 4. The charge / discharge circuit 53 is connected to the motor drive circuit 44 at a connection point between the switching element 53A and the switching element 53B.

  The charge / discharge signal SCD1 of the power management unit 42 is input to the gate portion of the switching element 53A. The charge / discharge signal SCD2 of the power management unit 42 is input to the gate portion of the switching element 53B. Switching elements 53A and 53B perform an operation of changing the on state and the off state based on charge / discharge signals SCD1 and SCD2.

With reference to FIG. 3 and FIG. 4, the output state by charging / discharging of the main power supply 4 and the auxiliary power supply device 50 is demonstrated.
The main power supply 4 and the auxiliary power supply device 50 operate in the first output state, the second output state, and the third output by the operations of the switching elements 52A and 52B of the booster circuit 52 and the switching elements 53A and 53B of the charge / discharge circuit 53, respectively. Form an output state.

  As shown in FIG. 3, in the first output state, the switching element 52A is turned off, the switching element 52B is turned off, the switching element 53A is turned off, and the switching element 53B is turned on. Therefore, as shown in FIG. 4A, in the first output state, the main power supply 4 supplies power to the capacitor 51 and the motor drive circuit 44, and the capacitor 51 supplies power to the motor drive circuit 44. Do not supply.

  As shown in FIG. 3, in the second output state, the switching element 52A is turned off, the switching element 52B is turned off, the switching element 53A is turned on, and the switching element 53B is turned off. Therefore, as shown in FIG. 4B, in the second output state, power is supplied to the motor drive circuit 44 with the battery voltage VB of the main power supply 4 boosted by the capacitor 51.

  As shown in FIG. 3, in the third output state, the switching elements 52A and 52B are PWM driven, the switching element 53A is turned off, and the switching element 53B is turned on. Therefore, as shown in FIG. 4C, in the third output state, the capacitor 51 is rapidly charged with the battery voltage VB of the main power supply 4 boosted by the booster circuit 52.

  With reference to FIG. 5, switching from the first output state to the third output state based on the operation of the steering device 1 in power supply control will be described. The graph G1 shows the transition of the required power. The graph G2 is indicated by a thick line and shows the transition of the power supply power PS. Further, in the following description with reference to FIG. 5, each component related to the steering device 1 to which a reference numeral is attached indicates each component of the steering device 1 described in FIG. 1 or FIG. 2.

  The “required power” indicates the power required for the main power supply 4 by the assist control. The ESP required power changes based on changes in the vehicle speed VS and the steering state. Further, “power supply power PS” indicates power supplied from the main power supply 4 to the auxiliary power supply device 50 by assist control. The power source power PS is calculated based on the battery current IB and the battery voltage VB. The “charge / discharge threshold KE” indicates a reference value for switching between the first output state (third output state) and the second output state. The charge / discharge threshold KE is set in advance by a test or the like.

  When power supply power PS is less than charge / discharge threshold KE, control device 40 sets the output state to the first output state by power supply control. As a result, the required power is supplemented by the power of the main power supply 4, so that the power supply power PS and the required power are equal. Therefore, as shown by the graphs G1 and G2 in FIG. 5, the power source power PS is less than the charge / discharge threshold KE and equal to the required power in a period in which the required power is less than the charge / discharge threshold KE.

  Moreover, the control apparatus 40 sets an output state to a 2nd output state by power supply control, when the power supply electric power PS is more than the charging / discharging threshold value KE. For this reason, as shown in the graph G2 of FIG. 5, the power source power PS becomes equal to the charge / discharge threshold KE in a period in which the required power is equal to or higher than the charge / discharge threshold KE. That is, the power source power PS is peak-cut in a period in which the required power is equal to or higher than the charge / discharge threshold KE. In a period in which the required power is equal to or higher than the charge / discharge threshold KE, the difference power between the required power and the charge / discharge threshold KE is supplemented by the capacitor 51. In addition, as a case where the power source power PS becomes equal to or higher than the charge / discharge threshold value KE, there is a case where the driver performs the steering steering of the steering wheel 2 when the vehicle is put into the garage or when the vehicle is parked.

  The control device 40 sets the output state to the second output state and discharges the capacitor 51 to the motor drive circuit 44, that is, when the power source power PS becomes less than the charge / discharge threshold value KE, the output state is controlled by the power source control. Is set to the third output state. Thereby, the capacitor 51 is rapidly charged. A section indicated by a dot in FIG. 5 indicates a charging period of the capacitor 51.

  When the remaining capacity of the capacitor 51 is equal to or lower than the lower limit value of the remaining capacity of the capacitor 51, if the power source power PS is less than the charge / discharge threshold KE, the third output state is set and the capacitor 51 is charged. On the other hand, when the power source power PS is equal to or higher than the charge / discharge threshold KE, the first output state is set. In this case, if the voltage of the capacitor 51 is lower than the battery voltage VB, the capacitor 51 is charged by the power of the main power supply 4. In addition, the lower limit value of the remaining capacity of the capacitor 51 is a lower limit value of the remaining capacity that suppresses a decrease in the life of the capacitor 51 or a decrease in the allowable amount of the capacitor 51 due to the discharge of the capacitor 51. The lower limit value of the remaining capacity of the capacitor 51 is set in advance by a test or the like.

  The setting of the charge / discharge threshold value KE will be described with reference to FIGS. Moreover, in the following description with reference to FIGS. 6-8, each component regarding the steering device 1 to which the code | symbol was attached | subjected shows each component of the steering device 1 described in FIG. 1 or FIG.

  FIG. 6 is a graph showing the relationship between the temperature of the capacitor 51 and the internal resistance of the capacitor 51. As shown in FIG. 6, the internal resistance of the capacitor 51 increases as the temperature of the capacitor 51 decreases. In particular, in the range where the temperature of the capacitor 51 is lower than the predetermined temperature T1, the amount of increase in the internal resistance of the capacitor 51 with respect to the decrease in the temperature of the capacitor 51 is significantly increased. When the capacitor 51 is discharged in a temperature range where the temperature of the capacitor 51 is lower than the temperature T1, the internal resistance of the capacitor 51 is large, so that the voltage of the capacitor 51 drops rapidly. That is, the remaining capacity of the capacitor 51 is rapidly reduced. This makes it easier for the remaining capacity (voltage) of the capacitor 51 to fall below the lower limit value of the remaining capacity of the capacitor 51.

  As an example, the graph G30 and the graph G31 in FIG. 8 are obtained when the temperature of the capacitor 51 is “25 ° C.” and “−30 ° C.” when the charge / discharge threshold KE is constant regardless of the temperature of the capacitor 51. The transition of the voltage (remaining capacity) of the capacitor 51 when continuously stationary steering is shown.

  As shown by the graph G30, when the temperature of the capacitor 51 is “25 ° C.”, the internal resistance of the capacitor 51 is small, so that the voltage drop due to the discharge of the capacitor 51 is small. For this reason, the voltage of the capacitor 51 does not fall below the voltage corresponding to the lower limit value of the remaining capacity of the capacitor 51 (hereinafter referred to as “lower limit voltage CL”) even if it is continuously stationary.

  On the other hand, as shown by the graph G31, when the temperature of the capacitor 51 is “−30 ° C.”, the internal resistance of the capacitor 51 is large, so that the voltage drop due to the discharge of the capacitor 51 is large. For this reason, the voltage of the capacitor 51 reaches the lower limit voltage CL in the first stationary steering, and the voltage of the capacitor 51 falls below the lower limit voltage CL in the second and subsequent stationary steering. That is, when the temperature of the capacitor 51 is “−30 ° C.”, the remaining capacity of the capacitor 51 reaches the lower limit of the remaining capacity of the capacitor 51 in the first stationary steering, and the capacitor 51 in the second and subsequent stationary steerings. The remaining capacity is below the lower limit value of the remaining capacity of the capacitor 51.

  As described above, when the temperature of the capacitor 51 is low, the voltage drop of the capacitor 51 due to the discharge of the capacitor 51 is large. Therefore, it is preferable that the capacitor 51 is difficult to discharge. Further, when the remaining capacity of the capacitor 51 is small, it is preferable that the capacitor 51 is difficult to discharge because the voltage of the capacitor 51 is likely to be lower than the lower limit voltage CL due to the discharge of the capacitor 51.

  Therefore, the power management unit 42 of the control device 40 stores a map MP of the charge / discharge threshold value KE shown in FIG. The map MP shows the relationship between the temperature of the capacitor 51 and the charge / discharge threshold KE. In the map MP, graphs G11 to G15 in FIG. 7 show the relationship between the remaining capacity of the capacitor 51 and the charge / discharge threshold KE. The graph G11 shows the charge / discharge threshold value KE when the capacitor 51 is fully charged. In the graphs G11 to G15, the remaining capacity of the capacitor 51 decreases in the order from the graph G11 to the graph G15. As shown in the graphs G11 to G15, the charge / discharge threshold value KE increases as the remaining capacity of the capacitor 51 decreases.

  The map MP divides the temperature of the capacitor 51 into a high temperature range RTH, an intermediate temperature range RTM, and a low temperature range RTL. The high temperature range RTH is a temperature range higher than the temperature T1. The temperature T1 corresponds to the temperature T1 in FIG. An example of the temperature T1 is “0 ° C.”. The intermediate temperature range RTM is a temperature range between the temperature T2 and the temperature T1. An example of the temperature T2 is “−15 ° C.”. The low temperature range RTL is a temperature range lower than the temperature T2. The temperature T1 corresponds to a “second temperature”. The temperature T2 corresponds to a “first temperature”.

  Hereinafter, as an example, the charge / discharge threshold KE when the capacitor 51 is fully charged (graph G11) will be described. The graphs G12 to G15 show the same relationship as the graph G11 except that the value of the charge / discharge threshold KE is larger than that of the graph G11.

  In the high temperature range RTH, the charge / discharge threshold value KE is the first threshold value K1. In the high temperature range RTH, the first threshold value K1 is maintained regardless of the temperature of the capacitor 51. The first threshold value K1 indicates a charging / discharging threshold value at which the voltage of the capacitor 51 is less likely to be lower than the lower limit voltage CL when the fully charged capacitor 51 included in the high temperature range RTH is discharged.

  In the low temperature range RTL, the charging / discharging threshold value KE is a second threshold value K2 (K2> K1) that is larger than the first threshold value K1. In the low temperature range RTL, the second threshold value K2 is maintained regardless of the temperature of the capacitor 51. The second threshold value K2 indicates a charge / discharge threshold value that is less likely to cause the voltage of the capacitor 51 to fall below the lower limit voltage CL when the fully charged capacitor 51 included in the low temperature range RTL is discharged.

  In the intermediate temperature range RTM, the charge / discharge threshold KE increases from the first threshold K1 as the temperature of the capacitor 51 decreases from the temperature T1. The charge / discharge threshold value KE matches the second threshold value K2 when the temperature of the capacitor 51 is the temperature T2.

  When such a map MP of the charge / discharge threshold KE is used, when the temperature of the capacitor 51 is “−30 ° C.”, the charge / discharge threshold KE increases, the capacitor 51 is difficult to discharge, and the capacitor 51 is discharged. However, the discharge amount of the capacitor 51 is reduced. For this reason, as shown by the graph G20 in FIG. 8, when the temperature of the capacitor 51 is “−30 ° C.”, the voltage of the capacitor 51 is prevented from falling below the lower limit voltage CL even if it is continuously stationary. The That is, when the map MP is used, when the temperature of the capacitor 51 is “−30 ° C.”, the remaining capacity of the capacitor 51 is prevented from falling below the lower limit value of the remaining capacity of the capacitor 51 even if the stationary steering is continuously performed. Is done.

  Next, with reference to FIG. 9, a processing procedure for power supply control will be described. Further, in the following description with reference to FIG. 9, each component related to the steering apparatus 1 to which a reference numeral is attached indicates each component of the steering apparatus 1 described in FIG. 1 or FIG. 2.

First, the control device 40 calculates the charge / discharge threshold value KE in the following steps S11 to S13.
(A1) The temperature of the capacitor 51 is acquired (step S11).
(A2) The remaining capacity of the capacitor 51 is acquired (step S12).
(A3) The charge / discharge threshold value KE is calculated based on the temperature of the capacitor 51 and the remaining capacity of the capacitor 51 (step S13).

  In step S <b> 11, the control device 40 acquires the temperature of the capacitor 51 based on the signal from the temperature sensor 55. In step S12, control device 40 acquires the remaining capacity of capacitor 51 based on battery voltage VB. In step S <b> 13, control device 40 calculates charge / discharge threshold value KE from the temperature of capacitor 51 and the remaining capacity of capacitor 51 using map MP shown in FIG. 7.

Next, the control device 40 sets the output state due to charging / discharging of the main power supply 4 and the auxiliary power supply device 50 to any one of the first output state to the third output state based on the determinations of the following step S14 and step S15.
(B1) Whether the power source power PS is equal to or higher than the charge / discharge threshold (step S14).
(B2) Whether or not the capacitor 51 is fully charged (step S15).

  When the determination is affirmative in step S14, the control device 40 sets the second output state in step S21. When the determination is negative in step S14 and the positive determination is in step S15, the control device 40 sets the first output state in step S22. When the determination is negative in step S14 and step S15, control device 40 sets the third output state in step S23.

The steering device 1 has the following operations and effects.
(1) The control device 40 makes the charge / discharge threshold value KE when the temperature of the capacitor 51 is low larger than the charge / discharge threshold value KE when the temperature of the capacitor 51 is high according to the map MP. For this reason, when the temperature of the capacitor 51 is low, that is, when the discharge amount of the capacitor 51 may be excessively increased due to the large internal resistance of the capacitor 51, the chance of discharging the capacitor 51 is reduced. And even if the capacitor 51 is discharged, the amount of discharge is reduced. Moreover, since charging / discharging threshold value KE is large, possibility that power supply power PS will become less than charging / discharging threshold value KE becomes high. For this reason, the capacitor 51 is easily charged. Therefore, it is difficult for the remaining capacity of the capacitor 51 to fall below the lower limit value of the remaining capacity of the capacitor 51. For this reason, the lifetime of the capacitor 51 is unlikely to decrease.

  (2) The controller 40 increases the charge / discharge threshold value KE as the remaining capacity of the capacitor 51 decreases according to the map MP. For this reason, as the remaining capacity of the capacitor 51 decreases, the opportunity for the capacitor 51 to discharge decreases, and even if the capacitor 51 discharges, the amount of discharge decreases. Moreover, since the possibility that the power supply power PS will be less than the charge / discharge threshold KE increases, the capacitor 51 is easily charged. Therefore, it is difficult for the remaining capacity of the capacitor 51 to fall below the lower limit value of the remaining capacity of the capacitor 51.

  (3) As shown in FIG. 6, the relationship between the internal resistance of the capacitor 51 and the temperature of the capacitor 51 is such that when the temperature of the capacitor 51 is equal to or lower than the temperature T1, the internal resistance of the capacitor 51 decreases as the temperature of the capacitor 51 decreases. Includes areas that increase with a large slope.

  On the other hand, when the temperature of the capacitor 51 is lower than the temperature T1, the charge / discharge threshold KE is set to the second threshold K2, and when the temperature of the capacitor 51 is equal to or higher than the temperature T1, the charge / discharge threshold KE is set to the first threshold K1. In this case, the relationship between the internal resistance of the capacitor 51 and the temperature of the capacitor 51 is not sufficiently reflected. For this reason, the charging / discharging threshold value KE may be set large although the internal resistance of the capacitor 51 is small. For this reason, when it is preferable to boost the voltage of the main power supply 4 by the capacitor 51, the power of the main power supply 4 is not boosted in that way, and the opportunity for increasing the burden on the main power supply 4 increases.

  On the other hand, the control device 40 of the present embodiment associates the intermediate temperature range RTM with a region where the internal resistance of the capacitor 51 increases with a large inclination as the temperature of the capacitor 51 decreases. That is, control device 40 sets charging / discharging threshold value KE larger as the temperature of capacitor 51 becomes lower in intermediate temperature range RTM. Thereby, the relationship between the internal resistance of the capacitor 51 and the temperature of the capacitor 51 is appropriately reflected in the relationship between the charge / discharge threshold KE and the temperature of the capacitor 51. For this reason, the capacitor 51 is easily discharged in the high temperature range of the intermediate temperature range RTM where the internal resistance of the capacitor 51 is small, and the capacitor 51 is discharged in the low temperature range of the intermediate temperature range RTM where the internal resistance of the capacitor 51 is large. Hard to do. For this reason, in the range on the high temperature side of the intermediate temperature range RTM, the chance of discharging the capacitor 51 increases, so the burden on the main power supply 4 can be reduced. Further, in the high temperature range of the intermediate temperature range RTM, the voltage drop due to the discharge of the capacitor 51 is small, so that the remaining capacity of the capacitor 51 is less likely to fall below the lower limit value of the remaining capacity of the capacitor 51 due to the discharge of the capacitor 51.

  On the other hand, in the range on the low temperature side of the intermediate temperature range RTM, the internal resistance of the capacitor 51 becomes larger than that on the high temperature side of the intermediate temperature range RTM, so the chance of discharging the capacitor 51 is reduced. For this reason, it is difficult for the remaining capacity of the capacitor 51 to fall below the lower limit of the remaining capacity of the capacitor 51.

  (4) The case where the charge / discharge threshold KE when the temperature of the capacitor 51 belongs to the low temperature range RTL is set larger than the charge / discharge threshold KE when the temperature of the capacitor 51 does not belong to the low temperature range RTL. However, when the absolute value is small, there is a possibility that the chance of discharging the capacitor 51 is not sufficiently reduced when the internal resistance of the capacitor 51 is large.

  On the other hand, according to the control device 40, the charge / discharge threshold value KE when the temperature of the capacitor 51 belongs to the low temperature range RTL is equal to the lower limit voltage CL when the capacitor 51 belonging to the low temperature range RTL is discharged. The risk of falling below is set to a small value. For this reason, when the internal resistance of the capacitor 51 is large, the opportunity for the capacitor 51 to discharge becomes smaller.

  In addition, the specific form which this steering apparatus can take is not limited to the content shown by the said embodiment. This steering apparatus can take the form of the modification of the said embodiment shown below, for example.

  The map MP of the modified example does not have the intermediate temperature range RTM. The modified map MP is divided into two ranges, a high temperature range RTH and a low temperature range RTL. In the map MP of the modification, the high temperature range RTH is a temperature range that is equal to or higher than the temperature T2, or the low temperature range RTL is a temperature range that is lower than the temperature T1.

In the map MP of the modification, the charge / discharge threshold KE increases as the temperature of the capacitor 51 decreases in the high temperature range RTH.
In the map MP of the modification, the charge / discharge threshold value KE increases as the temperature of the capacitor 51 decreases in the low temperature range RTL.

  The map MP of the modified example does not have the low temperature range RTL, the intermediate temperature range RTM, and the high temperature range RTH, and the charge / discharge threshold value KE increases as the temperature of the capacitor 51 decreases.

The modified temperature sensor 55 detects the temperature of a cell (not shown) of the capacitor 51.
The auxiliary power supply device 50 according to the modification has a plurality of capacitors 51.
-The auxiliary power supply device 50 of a modification has secondary batteries, such as a lithium ion battery, as an auxiliary power supply.

The capacitor 51 according to the modification is an electric double layer capacitor.
-Each switching element 52A, 52B of the booster circuit 52 of a modification, and each switching element 53A, 53B of the charging / discharging circuit 53 are electromagnetic switches, such as IBGT or a relay.

The steering device 1 according to the modification is configured as a pinion assist type or rack assist type electric power steering device.
The steering device 1 according to the modification has an electrohydraulic assist device including an electric pump or a hydraulic assist device.

  DESCRIPTION OF SYMBOLS 1 ... Steering device, 4 ... Main power supply, 11 ... Steering shaft, 31 ... Assist motor, 40 ... Control device, 51 ... Capacitor (auxiliary power supply), 53 ... Charging / discharging circuit (main power supply, auxiliary power supply, and assist motor Τ ... steering torque, KE ... charge / discharge threshold, PS ... power supply power, RTH ... high temperature range, RTM ... intermediate temperature range, RTL ... low temperature range, T1 ... temperature (second) Temperature), T2 ... temperature (first temperature).

Claims (5)

An assist motor that applies torque to the steering shaft, an auxiliary power source that is charged by power of a main power source that supplies power to the assist motor, and an electrical connection relationship between the main power source, the auxiliary power source, and the assist motor. A control device for controlling a steering device having a switching circuit;
Based on the fact that the power supply power, which is the power supplied by the main power supply to the steering device, is less than the charge / discharge threshold, the power of the main power supply is supplied to the assist motor without being boosted by the auxiliary power supply. Set up the circuit,
Based on the power supply power being equal to or higher than the charge / discharge threshold, the power of the main power supply is boosted by the auxiliary power supply, and the circuit is set so that the boosted power is supplied to the assist motor,
A control device for a steering device, wherein the charge / discharge threshold value when the temperature of the auxiliary power source is low is set to be larger than the charge / discharge threshold value when the temperature of the auxiliary power source is high. The charging / discharging threshold when the temperature of the auxiliary power source is included in a low temperature range that is a temperature range lower than the first temperature is a temperature range equal to or higher than a second temperature where the temperature of the auxiliary power source is higher than the first temperature. Set larger than the charge / discharge threshold when included in a certain high temperature range,
The charging / discharging threshold when the temperature of the auxiliary power source is included in an intermediate temperature range that is equal to or higher than the first temperature and lower than the second temperature is set as the temperature of the auxiliary power source decreases. The control of the steering device according to claim 1, wherein the temperature of the auxiliary power source is increased from the charge / discharge threshold when the temperature is included in the high temperature range toward the charge / discharge threshold when the temperature is included in the low temperature range. apparatus. In addition to the temperature of the auxiliary power supply, the charge / discharge threshold is changed in accordance with the remaining capacity of the auxiliary power supply. In the relationship between the remaining capacity of the auxiliary power supply and the charge / discharge threshold, the remaining capacity of the auxiliary power supply is predetermined. The control device for a steering device according to claim 1 or 2, wherein when the remaining capacity is less than the remaining amount, the charge / discharge threshold is set larger than when the remaining capacity of the auxiliary power source is equal to or more than the predetermined remaining amount. A state in which the power of the main power source is not boosted by the auxiliary power source based on the fact that the power source power is greater than or equal to the charge / discharge threshold when the remaining capacity of the auxiliary power source is less than or equal to the lower limit value of the remaining capacity of the auxiliary power source The circuit is set so that the power of the main power source is supplied to the assist motor, and the auxiliary power source is charged by the power of the main power source based on the power source power being less than the charge / discharge threshold. The control device for a steering apparatus according to any one of claims 1 to 3, wherein the circuit is set to   A steering device including the control device according to claim 1.