JP2006062616A - Vehicle steering assist device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a driver's burden by avoiding a sudden change in steering force by a driver even when a power supply system is abnormal in a vehicle steering assist device using an electric motor.
A steering assist electronic control unit 31 detects an abnormality in a power supply system. When this abnormality is detected, the electronic control unit 31 controls the operation control circuit 32 to switch the electric motor 15 to the regenerative braking operation. Thereby, when the assist force by the output torque of the electric motor 15 cannot be obtained, the regenerative braking force by the electric motor 15 is applied to the reverse input from the road surface to return the steering handle 11 to the neutral position. . In this regenerative braking operation, the pulse width of the pulse signal for switching the operation control circuit 32 is gradually reduced to gradually reduce the regenerative braking force. Further, when the steering direction of the steering handle 11 is reversed, the regenerative braking operation of the electric motor 15 is promptly released.
[Selection] Figure 2

Description

  The present invention relates to a vehicle steering assist device that assists a steering operation of a steering wheel by an output torque of an electric motor.

Conventionally, for example, as shown in Patent Document 1 below, by transmitting the output torque of an electric motor to a steering shaft, a rack bar, etc., an assisting force is given to the turning of the steered wheels, and the driver A vehicle steering assist device that assists the steering operation of the steering wheel is well known.
JP 2003-314654 A

  In this type of conventional steering assist device, the assist control is stopped when the power supply system is abnormal. However, if the assist control stops, the driver needs to suddenly increase the steering force of the steering wheel in order to compensate for the decrease in the assist force. In particular, when the vehicle is turning, the reverse input from the road surface is large, and when a large assist force is applied by the electric motor before the assist is stopped, the burden on the driver is very large.

  The present invention has been made to address the above problems, and an object of the present invention is to provide a vehicle steering assist device that reduces a driver's burden by avoiding a sudden change in steering force by the driver even when the power supply system is abnormal. It is to provide.

  In order to achieve the above object, the present invention is characterized by an output torque of an electric motor having an electric motor and an operation control circuit for controlling the operation of the electric motor, the drive control of which is controlled in the drive control state of the operation control circuit. In the vehicle steering assist device for assisting the steering operation of the steering wheel, the abnormality detection means for detecting abnormality of the power supply system, and when the abnormality is detected, the operation control circuit is switched from the drive control state to the regenerative braking control state. Regenerative braking control means for regenerative braking operation of the motor is provided.

  According to this, when an abnormality occurs in the power supply system and the steering assist force due to the output torque of the electric motor cannot be obtained, the electric motor is switched to the regenerative braking operation, so that the steered steering handle is moved to the neutral position. The regenerative braking force by the electric motor acts on the reverse input from the road surface to return to. Therefore, even if the assist control by the electric motor is stopped due to an abnormality in the power supply system, the driver does not need to suddenly increase the steering force of the steering wheel, and the burden on the driver can be reduced.

  Another feature of the present invention is that the regenerative braking control means sets the operation control circuit on condition that the steering force required for the steering operation of the steering wheel by the driver is larger than a predetermined value when the abnormality is detected. The drive control state is switched to the regenerative braking control state. According to this, even if the assist control by the electric motor is stopped due to an abnormality in the power supply system, the electric motor is switched to the regenerative braking operation when it is not necessary to suddenly increase the steering force of the steering wheel by the driver. Therefore, unnecessary switching control can be omitted.

  Another feature of the present invention is that the regenerative braking control means changes the operation control circuit so that the regenerative braking force by the electric motor gradually decreases after switching the operation control circuit from the drive control state to the regenerative braking control state. It is something to control. According to this, when the assist control by the electric motor is stopped due to an abnormality in the power supply system, the regenerative braking force against the reverse input from the road surface gradually decreases. The transition can be performed smoothly, and a sudden change in the steering force applied to the steering wheel by the driver can be avoided.

  Another feature of the present invention is that, in addition to the configuration described above, a reversal detecting means for detecting reversal of the steering direction of the steering wheel during regenerative braking operation of the electric motor, and when the reversal is detected, There is provided braking force control means for controlling the regenerative braking control means so that the regenerative braking force by the electric motor is rapidly reduced. In this case, for example, the braking force control unit immediately cancels the regenerative braking control state of the operation control circuit when the reversal is detected, or the regenerative braking force is faster than the decrease rate of the regenerative braking force by the regenerative braking control unit. The regenerative braking control means is controlled so as to decrease. According to this, when the driver reverses the steering operation of the steering wheel, the regenerative braking force acting as a reaction force against the reverse steering is quickly released. As a result, the driver can quickly return the steering wheel to the neutral position.

  Another feature of the present invention is that the reversal detection means detects reversal of the steering direction of the steering wheel when the reversal of the steering direction of the steering wheel continues for a predetermined time or more. According to this, even if the steering direction of the steering wheel is reversed only for a short time due to a road surface disturbance, the reversal due to the road surface disturbance is not detected as a reversal of the steering direction of the steering wheel, and an erroneous regenerative braking of the electric motor is performed. Release of operation can be avoided.

  Another feature of the present invention is that the above-described configuration is further provided with an absorption circuit that absorbs regenerative power from the electric motor during regenerative braking operation of the electric motor. According to this, even if the regenerative power from the electric motor increases, the regenerative power is consumed, and it is possible to prevent the operation control circuit and the booster circuit that supplies power to the operation control circuit from being destroyed. .

  Another feature of the present invention resides in that a voltage rise prevention circuit for preventing the voltage due to the regenerative braking operation of the electric motor from rising above a predetermined voltage is provided in the configuration as described above. According to this, it is possible to prevent the voltage due to the regenerative braking operation of the electric motor from becoming abnormally high, and it is possible to prevent the operation control circuit and the booster circuit that supplies power to the operation control circuit from being destroyed.

  Another feature of the present invention resides in that the regenerative braking control means controls the operation control circuit so that the regenerative current from the electric motor circulates to the electric motor via the operation control circuit. According to this, the effect by the regenerative braking of the electric motor can be enjoyed without affecting the power supply system side.

  Another feature of the present invention is that the regenerative braking control means switches the operation control circuit when the voltage between the terminals of the electric motor by the regenerative braking operation rises to a predetermined voltage or more, so that the regenerative current by the electric motor is It is intended to include a switching means for allowing flow to the power supply system side. According to this, when the voltage between the terminals of the electric motor rises during the regenerative braking operation of the electric motor due to the circulation of the regenerative current, switching is performed so that the regenerative power of the electric motor is returned to the power supply system side. The electric motor and the operation control circuit can be well protected.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall schematic diagram of a vehicle steering apparatus to which a steering assist apparatus according to the present invention is applied.

  The vehicle steering apparatus includes a steering shaft 12 connected to a steering handle 11 so that an upper end thereof is integrally rotated. A pinion gear 13 is connected to a lower end of the shaft 12 so as to be integrally rotated. The pinion gear 13 meshes with rack teeth formed on the rack bar 14 to constitute a rack and pinion mechanism. The left and right front wheels FW1, FW2 are steerably connected to both ends of the rack bar 14, and the left and right front wheels FW1, FW2 are moved to the left and right according to the axial displacement of the rack bar 14 as the steering shaft 12 rotates about the axis. Steered.

  An electric motor 15 is assembled to the lower part of the steering shaft 12. The electric motor 15 rotationally drives the steering shaft 12 around the axis line via the speed reduction mechanism 16 when rotating. As shown in FIG. 2, the electric motor 15 includes a three-phase motor including three-phase coils CL1, CL2, and CL3.

  The vehicle steering apparatus also includes a steering torque sensor 21, a vehicle speed sensor 22, a battery 23, and an electric control circuit 30. The steering torque sensor 21 is assembled to the steering shaft 12 and detects the steering torque TR applied to the steering handle 11. The steering torque TR indicates the direction of the torque by its positive and negative, and indicates the magnitude of the torque by its absolute value. The vehicle speed sensor 22 detects the vehicle speed V. The battery 23 supplies direct-current power to the electric control circuit 30 via a control unit drive power supply line L2 provided with a motor drive power supply line L1 and an ignition switch 24.

  The electric control circuit 30 includes a steering assist electronic control unit 31 (hereinafter simply referred to as an electronic control unit 31), an operation control circuit 32, and a booster circuit 33. The electronic control unit 31 includes a microcomputer including a CPU, a ROM, a RAM, an A / D converter, and the like as main components, and a program to be described later that responds to supply of power from the control unit drive power line L2. By execution, the electric motor 15 is driven and controlled via the operation control circuit 32. The operation control circuit 32 is connected between the booster circuit 33 and the electric motor 15 and includes switching elements SW11, SW12, SW21, SW22, SW31, SW32 corresponding to the coils CL1, CL2, CL3 of the electric motor 15, respectively. Have. These switching elements SW11, SW12, SW21, SW22, SW31, SW32 are ON / OFF controlled by the electronic control unit 31. Between the operation control circuit 32 and the electric motor 15, motor switch circuits 34a and 34b for interrupting the gap are interposed.

  The booster circuit 33 boosts the DC voltage supplied from the battery 23 via the motor drive power line L1 to a predetermined voltage and supplies the boosted voltage to the operation control circuit 32. A power supply switch circuit 35 for interrupting the connection between the battery 23 and the booster circuit 33 is interposed in the motor drive power line L1. An electrolytic capacitor 36 for removing noise is connected to a connection line connecting the booster circuit 33 and the operation control circuit 32. The booster circuit 33 is also connected to the electronic control unit 31, and supplies information such as an input voltage (battery voltage) and an output voltage for determining an abnormality of the booster circuit 33 to the electronic control unit 31.

  Next, the operation of the embodiment configured as described above will be described. When the ignition switch 24 is turned on, the voltage from the battery 23 is supplied to the electronic control unit 31 via the control unit drive power supply line L2. The power supply switch circuit 35 and the motor switch circuits 34a and 34b are set to the on state by the initial setting by the electronic control unit 31, and the DC power from the battery 23 is supplied to the booster circuit 33 via the motor drive power line L1. Is supplied. In response to the voltage supply, the electronic control unit 31 predetermines a mode determination program shown in FIG. 3, a steering direction determination program shown in FIG. 4, and a motor control program shown in FIG. 5 (including the regenerative braking control routine shown in FIG. 6). Start running repeatedly every short time. The booster circuit 33 boosts the voltage from the battery 23 to a predetermined voltage and supplies it to the operation control circuit 32.

  Execution of the mode determination program is started in step S10 in FIG. 3, and in step S11, the battery voltage decreases, the motor drive power supply line L1 is broken or short-circuited, the motor drive power supply system is abnormal, the electric motor 15 Abnormality and other abnormalities are detected. In the detection of these abnormalities, the electronic control unit 31 inputs signals related to the input / output voltage of the booster circuit 33, an abnormality detection circuit of the electric motor 15 (not shown), etc., and performs abnormality detection processing based on the input signals. Execute. Then, it is determined whether an abnormality has been detected. If no abnormality is detected, “No” is determined in step S12, the mode flag MD is set to “0” in step S16, and the mode determination program is temporarily terminated in step S21. The mode flag MD indicates a steering assist mode (normal state) in which steering assist by the electric motor 15 is performed by “0”, and indicates a cutoff mode in which the operation of the electric motor 15 is stopped by “1”. Represents a regenerative braking mode in which the electric motor 15 is regeneratively braked.

  On the other hand, the electronic control unit 31 repeatedly executes the steering direction determination program of FIG. 4 every predetermined short time in parallel with the mode determination program. Execution of the steering direction determination program is started in step S30, and it is determined in step S31 whether the mode flag MD is not "2", that is, whether the regenerative braking mode is not set. If the mode flag MD is “0” as described above, “Yes” is determined in step S31, and the steering torque memory value TRM is detected by the steering torque sensor 21 in step S32. Set to TR.

  In step S33, it is determined whether the steering torque memory value TRM and the current detected steering torque value TR have the same sign (TRM <0 and TR <0, or TRM ≧ 0 and TR ≧ 0). In this case, since the steering torque memory value TRM is equal to the current detected steering torque value TR by the process of step S32, “Yes” is determined in step S33. In step S34, a steering reversal count value SCT for measuring the reversal continuation time of the steering handle 11 is initially set to “0”, and in step S39, the execution of the steering direction determination program is temporarily terminated. The steering torque memory value TRM and the steering reversal count value SCT are used to detect the reversal of the steering wheel 11 when entering a regenerative braking mode (MD = “2”), which will be described in detail later.

  Further, the electronic control unit 31 repeatedly executes the motor control program of FIG. 5 every predetermined short time in parallel with the mode determination program and the steering direction determination program. The execution of the motor control program is started in step S40, and it is determined whether the mode flag MD is “2” or “1” in steps S41 and S42. Now, since the mode flag MD is set to “0”, it is determined as “No” in steps S41 and S42, and the process proceeds to step S43.

  In step S43, the steering torque TR detected by the steering torque sensor 21 and the vehicle speed V detected by the vehicle speed sensor 22 are input. In step S43, the assist torque ASTR corresponding to the input steering torque TM and vehicle speed V is calculated with reference to the assist torque table. The assist torque table is provided in the ROM of the electronic control unit 31, and, as shown in FIG. 7, the absolute value | ASTR | of the assist torque ASTR that increases as the absolute value | TR | of the steering torque TR increases. I remember it. Further, the absolute value | ASTR | of the assist torque ASTR shows a larger value as the vehicle speed V becomes lower than the steering torque TR having the same absolute value.

  Therefore, in step S43, the absolute value | TR | of the steering torque TR and the absolute value | ASTR | of the assist torque ASTR corresponding to the vehicle speed V are read from the assist table, and the absolute value | ASTR | A sign equal to the sign of positive and negative is given as assist torque ASTR. Instead of using the assist torque table, the assist torque ASTR that changes according to the steering torque TR and the vehicle speed V is stored in advance as a function, and the steering torque TR and the vehicle speed are calculated by executing the calculation using this function. The assist torque ASTR corresponding to V may be calculated.

  Then, the electronic control unit 31 performs inverter control of the electric motor 15 according to the assist torque ASTR in step S44, and ends the execution of this motor control program in step S48. Specifically, the electronic control unit 31 generates a three-phase pulse train signal having a pulse width substantially proportional to the magnitude of the assist torque ASTR, and performs switching in the operation control circuit 32 in the same manner as in known inverter control. The elements SW11, SW12, SW21, SW22, SW31, SW32 are sequentially switched. As a result, the three-phase drive current that generates the rotating magnetic field corresponding to the sign of the assist torque ASTR is supplied from the booster circuit 33 to the three-phase coil of the electric motor 15 via the operation control circuit 32 and the motor switch circuits 34a and 34b. It flows to CL1, CL2, CL3. In addition, the magnitude of the drive current at this time is proportional to the pulse width determined approximately in proportion to the determined assist torque ASTR. Therefore, the electric motor 15 rotates the steering shaft 12 around the axis with a driving torque corresponding to the assist torque ASTR via the speed reduction mechanism 16.

  The rotation of the steering shaft 12 drives the rack bar 14 in the axial direction via the pinion gear 13. By driving the rack bar 14 in the axial direction, the left and right front wheels FW1, FW2 are steered to the left and right by receiving an assist force corresponding to the assist torque ASTR. Therefore, when the driver steers the steering handle 11 to steer the left and right front wheels FW 1 and FW 2, the steering operation of the steering handle 11 by the driver is assisted by the output torque of the electric motor 15.

  Next, a case where an abnormality is detected by the abnormality detection process in step S11 of FIG. 3 described above will be described. In this case, the electronic control unit 31 determines “Yes” in step S12, and determines whether the mode flag MD is “0” in step S13. If no abnormality has occurred so far and the mode flag MD is “0”, it is determined as “Yes” in step S13, and the processing after step S14 is executed. However, once the mode flag MD is set to “1” by the process of step S17 described later or once set to “2” by the process of step S18 described later, it is determined as “No” in step S13. Even after that, the mode flag MD is maintained at the previous value “1” or “2”.

  In step S14, it is determined whether the type of abnormality detected by the process in step S11 is an abnormality in the motor drive power supply system (for example, a decrease in battery voltage, disconnection or short circuit of the motor drive power supply line L1, etc.). judge. In this case, if it is not an abnormality in the motor drive power supply system but an abnormality in the electric motor 15 or other abnormality, it is determined as “No” in step S14, and the mode flag MD is set to “1” in step S17. Set.

  On the other hand, also in this case, the electronic control unit 31 executes the steering direction determination program of FIG. 4 and the motor control program of FIG. In the steering direction determination program, the mode flag MD is not “2”, that is, does not represent the regenerative braking mode, so the same processes of steps S31 to S34 as when the mode flag MD is “0” are executed, In step S39, execution of the steering direction determination program is temporarily terminated.

  In the motor control program, since the mode flag MD is “1”, “No” is determined in step S41, “Yes” is determined in step S42, and the process proceeds to step S45. In step S45, the electronic control unit 31 switches the motor switch circuits 34a and 34b and the power supply switch circuit 35 to the off state. Thereby, the electric motor 15 is disconnected from the operation control circuit 32, and the booster circuit 33 is disconnected from the battery 23. Therefore, in this case, the operations of the electric motor 15 and the booster circuit 33 are completely stopped, and the steering assist by the electric motor 15 is immediately controlled to stop.

  After step S45, a regenerative braking control duty ratio BDu, which will be described later, is cleared to “0” in step S46, and the assist torque ASTR is also cleared to “0”. In step S48, the execution of the motor control program is temporarily terminated.

  On the other hand, if the type of abnormality is an abnormality in the motor drive power supply system, “Yes” is determined in step S14, and the process proceeds to step S15. In step S15, the steering torque TR detected by the steering torque sensor 21 is input, and the assist torque ASTR set immediately before in step S43 in FIG. It is determined whether or not the added value TR + ASTR is larger than a predetermined torque TR1. This added value TR + ASTR represents the steering torque required for the driver immediately after stopping the steering assist in step S44 of FIG. If this steering torque (that is, the added value TR + ASTR) is equal to or smaller than the predetermined torque TR1, “No” is determined in step S15, and the mode flag MD is set to “1” in step S17. Therefore, in this case, even if the type of abnormality is an abnormality of the motor drive power supply system, the steering assist by the electric motor 15 is immediately stopped.

  On the other hand, when the added value TR + ASTR, that is, the steering torque required for the driver immediately after stopping the steering assist is larger than the predetermined torque TR1, it is determined as “Yes” in step S15, and the mode flag is determined in step S18. MD is set to “2”, and the mode determination program is temporarily terminated in step S19.

  Also in this case, the electronic control unit 31 executes the steering direction determination program of FIG. 4 and the motor control program of FIG. 5 every predetermined short time in parallel with the mode determination program. In the steering direction determination program, since the mode flag MD is set to “2”, it is determined “No” in step S31, and the process of step S32 is not executed. Thus, the steering torque memory value TRM is held at the steering torque value TR immediately before the mode flag MD is set to “2”. Specifically, the detected steering torque value TR when the steering assist control by the electric motor 15 is performed immediately before the mode flag MD is set to “2” is held.

  Therefore, when the driver does not reverse the steering direction of the steering wheel 11, the sign of the detected steering torque value TR input from the steering torque sensor 21 in step S33 is the sign of the steering torque memory value TRM. Is consistent with Accordingly, in the determination process in step S33, it is determined that “Yes”, that is, TRM <0 and TR <0, or TRM ≧ 0 and TR ≧ 0, and the steering reverse count value SCT is “0” by the process of step S34. Is maintained.

  On the other hand, in the motor control program of FIG. 5, the electronic control unit 31 determines “Yes” in step S41, and executes a regenerative braking control routine in step S47. Execution of the regenerative braking control routine is started in step S50 of FIG. 6, and after the assist torque ASTR is cleared to “0” in step S51, whether or not the steering reverse flag SFL is “1” in step S52. Determine. The steering reversal flag SFL represents a state in which the steering direction of the steering handle 11 is not reversed by “0” after entering the regenerative braking mode, and the steering direction of the steering handle 11 is changed to “1” after entering the regenerative braking mode. It represents the inverted state. The steering reversal flag SFL is initially set to “0”, and is set to “1” by the process of step S37 in FIG. 4 described later when the steering direction is reversed.

  Therefore, when the steering direction of the steering wheel 11 is not reversed, “No” is determined in step S52, and the processes of steps S53 and S54 are executed. In step S53, the initial state holding time BMTM is set to a predetermined time TM1 (for example, about 0.5 seconds). As shown in FIG. 8, this initial state holding time BMTM represents the time during which the switching elements SW11, SW22, SW32 of the operation control circuit 32 are on-controlled at a duty ratio of 100% in the regenerative braking operation of the electric motor 15 described later. . In step S54, the regenerative braking deceleration rate BDRT is set to a relatively small predetermined value RT1. The regenerative braking deceleration rate BDRT decreases the regenerative braking control duty ratio BDu relatively slowly as shown by the solid line in FIG.

  Next, in step S57, it is determined whether or not the initial state holding time count value BMCT is larger than the initial state holding time BMTM. Since the initial state holding time count value BMCT is initially set to “0”, it is determined as “No” in step S57, and the processes of steps S58 and S59 are executed. In step S58, a predetermined minute time value ΔT is added to the initial state holding time count value BMCT. This minute time value ΔT is obtained by the accumulation process at every execution time interval of the regenerative braking control routine from the start of the regenerative braking operation of the electric motor 15 so that the initial state holding time count value BMCT becomes the initial state holding time after the predetermined time TM1. It is set to exceed BMTM. In step S59, the regenerative braking control duty ratio BDu is set to 100%.

  Next, in step S60, the operation control circuit 32 is controlled so that the electric motor 15 performs a regenerative braking operation according to the regenerative braking control duty ratio BDu. Specifically, the switching elements SW11, SW22, SW32 in the operation control circuit 32 are simultaneously turned on with a pulse train signal having a pulse width equal to the regenerative braking control duty ratio BDu. However, in this case, since the regenerative braking control duty ratio BDu is set to 100%, the switching elements SW11, SW22, SW32 are kept on-controlled. During the process of step S60, the motor switch circuits 34a and 34b are kept in the on state, and at the same time, the switching elements SW12, SW21, and SW31 are kept in the off state.

  As a result, when the steering shaft 12 is rotated by the road surface reaction force and the electric motor 15 is driven, a current is applied to the coils CL1, CL2, CL3 and the switching elements SW11, SW22, SW32 in the direction of the arrow in FIG. Flowing. The electric motor 15 supplies power to the booster circuit 33 and the electrolytic capacitor 36 by regenerative braking operation. Further, the regenerative braking operation of the electric motor 15 acts as a braking force against the force by which the road surface reaction force rotates the steering shaft 12. That is, when the steering assist force due to the output torque of the electric motor 15 cannot be obtained due to the decrease in the battery voltage, the electric motor 15 applies the reverse input from the road surface to return the steered steering handle 11 to the neutral position. Regenerative braking force counters. Accordingly, the driver does not need to suddenly increase the steering force of the steering handle 11, and the burden on the driver is reduced.

  After the process of step S60, the electronic control unit 31 ends the execution of the regenerative braking control routine in step S65, returns to step S47 of the motor control program of FIG. 5, and executes the motor control program in step S48. Is temporarily terminated. When the motor control program is executed again, the mode flag MD is set to “2”, so that the regenerative braking control routine in step S47 is repeatedly executed. In the regenerative braking control routine, as long as the steering reversal flag SFL is set to “0”, it is determined as “No” in step S52, and the processes in steps S53 and S54 described above are repeatedly executed. Further, as long as the initial state holding time count value BMCT is equal to or less than the initial state holding time BMTM, it is determined as “No” in Step S57, and the processing of Steps S58 to S60 described above is repeatedly executed, so that SW22 and SW32 are kept on-controlled.

  If the initial state holding time count value BMCT becomes larger than the initial state holding time BMTM during the repeated processing as described above, it is determined as “Yes” in step S57, and the processing of step S61 is started. In step S61, the regenerative braking control duty ratio BDu is updated by subtracting the regenerative braking deceleration rate BDRT from the regenerative braking control duty ratio BDu in the previous process. As a result, as indicated by the solid line in FIG. 8, the regenerative braking control duty ratio BDu starts to gradually decrease from 100% set by the process of step S59. Then, as long as the regenerative braking control duty ratio BDu is equal to or greater than “0”, “No” is determined in step S62, and the electric motor 15 is regeneratively braked by the process of step S60 described above. In this case, however, the switching elements SW11, SW22, SW32 are turned on by a pulse train signal having a regenerative braking control duty ratio BDu smaller than 100%, and the regenerative braking control duty ratio BDu is gradually increased by the process of step S61. To decrease.

  When the regenerative braking control duty ratio BDu is smaller than “0”, it is determined as “Yes” in step S62, and the process proceeds to step S63. In step S63, the electronic control unit 31 turns off the motor switch circuits 34a and 34b and the power supply switch circuit 35. Thereby, the electric motor 15 is disconnected from the operation control circuit 32, and the booster circuit 33 is disconnected from the battery 23. Therefore, in this case, the operations of the electric motor 15 and the booster circuit 33 are completely stopped, and the regenerative braking operation of the electric motor 15 is controlled to stop.

  After step S63, the regenerative braking control duty ratio BDu is cleared to “0” and the mode flag MD is set to “1” in step S64. In step S65, the process returns to step S47 of the motor control routine of FIG. 5, and in step S48, the execution of the motor control program is temporarily terminated.

  By such processing of steps S60 to S63, the regenerative braking force by the electric motor 15 is gradually reduced, and the regenerative braking force against the reverse input from the road surface is gradually reduced. Finally, the regenerative braking force that opposes the reverse input from the road surface becomes “0”. As a result, the transition from the steering assist to the steering assist stop by the electric motor 15 can be performed smoothly, and a sudden change in the steering force applied to the steering wheel by the driver can be avoided.

  If the steering direction of the steering wheel 11 is reversed after the mode flag MD is set to “2”, “No” is determined in step S33 of FIG. 4 described above, and the process proceeds to step S35. In step S35, it is determined whether or not the steering reversal count value SCT is larger than a predetermined positive count value CT0. The steering reversal count value SCT was set to “0” by the process of step S34 while it was determined “Yes” in step S33, that is, the steering direction of the steering wheel 11 was not reversed. Therefore, at the start of reversal of the steering direction of the steering wheel 11, “No” is determined in step S35, and the process proceeds to step S36. In step S36, "1" is added to the steering reversal count value SCT, and the execution of this steering direction determination program is terminated in step S39.

  If the steering direction determination program is executed again and the steering direction of the steering wheel 11 continues to be reversed, it is determined “No” in step S33, so that the processing in steps S35 and S36 continues to be performed and the steering reversal is performed. The count value SCT continues to increase. When the steering reverse count value SCT becomes larger than the predetermined count value CT0, “Yes” is determined in step S35, and the steering reverse flag SFL is set to “1” in step S37. If the reversal of the steering direction of the steering wheel 11 is canceled before the steering reversal count value SCT becomes larger than the predetermined count value CT0, the steering reversal is performed based on the determination of “Yes” in step S33. The count value SCT is again cleared to “0” by the process of step S34. After the process of step S37, the steering reverse count value SCT is initially set to a predetermined count value CT0 in step S38, and the execution of the steering direction determination program is terminated in step S39. The predetermined count value CT0 is a value such that the steering reversal count value SCT becomes larger than the predetermined count value CT0 when the steering direction of the steering wheel 11 is continuously reversed for about 100 milliseconds. Is set to

  When the steering reversal flag SFL is set to “1” in this way, in the regenerative braking control routine of FIG. 6, “Yes” is determined in step S52, and the processes of steps S55 and S56 are executed. In step S55, the initial state holding time BMTM is set to “0”. In step S56, the regenerative braking deceleration rate BDRT is set to a predetermined value RT2 larger than the predetermined value RT1. The regenerative braking deceleration rate BDRT rapidly decreases the regenerative braking control duty ratio BDu, as shown by the broken line in FIG.

  Next, whether or not the initial state holding time count value BMCT is larger than the initial state holding time BMTM is determined by the process of step S57 described above. However, in this case, since the initial state holding time BMTM is set to “0”, it is immediately determined as “Yes” in Step S57, and the processing of Steps S61, S62, and S60 is started. Since the regenerative braking deceleration rate BDRT is also set to a large value, the regenerative braking control duty ratio BDu is rapidly changed from 100% to 0% (see the broken line in FIG. 8). When the regenerative braking control duty ratio BDu becomes “0”, the regenerative braking operation by the electric motor 15 is controlled to be stopped by the processing of steps S62 and S63 described above.

  After the mode flag MD is set to “2”, that is, after the control of the electric motor 15 is switched to the regenerative braking operation, when the reversal of the steering direction of the steering handle 11 is detected, the electric motor 15 The regenerative braking force is controlled so as to decrease rapidly. Therefore, the driver can easily and quickly return the steering handle 11 to the neutral position without countering the regenerative braking force of the electric motor 15.

  4, when the reversal of the steering direction of the steering handle 11 continues for a predetermined time or more, the reversal of the steering direction of the steering handle 11 is detected. Therefore, even if the steering direction of the steering handle 11 is reversed only for a short time due to a road surface disturbance, the reversal due to the road surface disturbance is not detected as a reversal of the steering direction of the steering handle 11, and the erroneous regenerative braking of the electric motor 15 is performed. Release of operation can be avoided.

  Furthermore, the present invention is not limited to the above-described embodiment and its modifications, and various modifications can be employed within the scope of the present invention.

  In the above embodiment, during regenerative braking control of the electric motor 15 (with the mode flag MD being “2”), when reversal of the steering direction of the steering handle 11 is detected, the regenerative braking force by the electric motor 15 is increased. It is released immediately, but not immediately. However, instead of this, when reversal of the steering direction of the steering handle 11 is detected during regenerative braking control of the electric motor 15, the regenerative braking control by the electric motor 15 may be stopped immediately. In this case, when it is determined that “Yes”, that is, the steering reverse count value SCT exceeds the predetermined count value CT0 in Step S35 of FIG. 4, or “Yes”, that is, the steering reverse flag SFL is “1” in Step S52 of FIG. When it is determined that the motor switch circuits 34a and 34b and the power supply switch circuit 35 are turned off as in the process of step S63 in FIG.

  In addition to the configuration of the above embodiment, as indicated by a broken line in FIG. 2, the switch circuit 41 that is always in an OFF state between the connection line connecting the booster circuit 33 and the operation control circuit 32 and the ground, and You may make it provide the absorption circuit which absorbs the regenerative electric power which consists of resistance 42. FIG. Then, while the mode flag MD is set to “2”, that is, while the electric motor 15 is performing the regenerative braking operation, the switch circuit 41 is switched to the ON state. According to this, during the regenerative braking operation of the electric motor 15, the regenerative power from the electric motor 15 is absorbed by the resistor 42, and even if the regenerative power from the electric motor 15 increases, the regenerative power is consumed by the resistor 42. As a result, it is possible to prevent the operation control circuit 32 and the booster circuit 33 from being destroyed.

  In addition to the configuration of the above embodiment, as indicated by a broken line in FIG. 2, one or more Zener diodes are connected between the connection line connecting the booster circuit 33 and the operation control circuit 32 and the ground. A voltage limit circuit 43 (voltage rise prevention circuit) may be provided so that the voltage of the connection line is always limited to less than a predetermined voltage. According to this, it is possible to prevent the voltage due to the regenerative braking operation of the electric motor 15 from becoming abnormally high, and to prevent the operation control circuit 32, the booster circuit 33 and the like from being destroyed.

  In the above embodiment, the switching elements SW11, SW22, SW32 in the operation control circuit 32 are set to the on state by the regenerative braking control process in step S60. However, instead of this, as shown in FIG. 9, the switching elements SW11, SW21, SW31 in the operation control circuit 32 may be set to the on state. According to this, at the time of regenerative braking control, current flows through a closed loop composed of the switching elements SW21 and SW31, the coils CL2 and CL3, the coil CL1 and the switching element SW11, that is, the regenerative current of the electric motor 15 passes through the operation control circuit 32. The regenerative braking by the electric motor 15 is realized by circulating to the electric motor 15. According to this, the effect equivalent to the effect by the said embodiment by the regenerative braking of the electric motor 15 can be anticipated, without affecting a power supply system.

  However, in this case, the voltage between the terminals of the electric motor 15 is input to the electronic control unit 32. Specifically, for example, a voltage between the coil CL2 and the coil CL3 is input to the electronic control unit 32 as an inter-terminal voltage. The electronic control unit 32 sets and controls the switching elements SW11, SW22, and SW32 in the operation control circuit 32 to be in an ON state when the voltage between the terminals becomes equal to or higher than a predetermined voltage value, as in the case of the above embodiment. Switch to Thereby, when the voltage between the terminals of the electric motor 15 rises, regenerative braking control is realized such that power is returned to the power system. As a result, even if the voltage between the terminals of the electric motor 15 rises during regenerative braking in which current flows through a closed loop composed of the switching elements SW21, SW31, coils CL2, CL3, coil CL1, and switching element SW11, the regeneration by the electric motor 15 occurs. The current is returned to the power supply system as in the above embodiment, and the electric motor 15 is well protected.

  Further, in the above embodiment, the steering assist electric motor 15 is assembled to the steering shaft 12. However, instead of or in addition to the electric motor 15, the electric motor 45 may be assembled to the rack bar 14 as indicated by a broken line in FIG. 1. In this case, when the electric motor 45 rotates, the rack bar 14 may be linearly driven in the axial direction via the screw feed mechanism.

1 is an overall schematic diagram of a vehicle steering apparatus according to an embodiment of the present invention. It is a block diagram which shows the electric control circuit of FIG. 1 in detail. It is a flowchart of the mode determination program performed by the electronic control unit of FIG. 4 is a flowchart of a steering direction determination program executed by the electronic control unit. It is a flowchart of the motor control program executed by the electronic control unit. It is a flowchart which shows the detail of the regenerative braking control routine of FIG. It is a graph which shows the relationship between the steering torque memorize | stored in the assist torque table provided in the said electronic control unit, a vehicle speed, and assist torque. It is a graph which shows the time change of regenerative braking control duty ratio at the time of regenerative braking operation of an electric motor. It is an operation explanatory view of an operation control circuit and an electric motor concerning a modification of the above-mentioned embodiment.

Explanation of symbols

FW1, FW2 ... left and right front wheels, 11 ... steering handle, 12 ... steering shaft, 15, 45 ... electric motor, 21 ... steering torque sensor, 22 ... vehicle speed sensor, 23 ... battery, 30 ... electric control circuit, 31 ... steering assist electronics Control unit (electronic control unit), 32 ... operation control circuit, 33 ... boost circuit, 34a, 34b ... motor switch circuit, 35 ... power supply switch circuit, 41 ... switch circuit, 42 ... resistor, 43 ... voltage limiting circuit (voltage) Rise prevention circuit).

Claims (9)

The vehicle has an electric motor and an operation control circuit for controlling the operation of the electric motor, and assists the steering operation of the steering wheel by the output torque of the electric motor that is drive-controlled in the drive control state of the operation control circuit. In the assist device,
An abnormality detection means for detecting an abnormality in the power supply system;
A vehicle steering assist device, comprising: regenerative braking control means for switching the operation control circuit from a drive control state to a regenerative braking control state and performing a regenerative braking operation of the electric motor when the abnormality is detected.   The regenerative braking control means changes the operation control circuit from the drive control state to the regenerative braking control state on condition that a steering force necessary for a steering operation of the steering wheel by the driver is larger than a predetermined value when the abnormality is detected. The vehicle steering assist device according to claim 1, wherein   The regenerative braking control means controls the operation control circuit so that the regenerative braking force by the electric motor gradually decreases after switching the operation control circuit from the drive control state to the regenerative braking control state. The vehicle steering assist device according to claim 1, wherein the vehicle steering assist device is a vehicle steering assist device. The vehicle steering assist device according to any one of claims 1 to 3, further comprising:
Reversal detecting means for detecting reversal of the steering direction of the steering wheel during regenerative braking operation of the electric motor;
A vehicle steering assist device, comprising: braking force control means for controlling the regenerative braking control means so that the regenerative braking force by the electric motor is rapidly reduced when the reversal is detected.   5. The vehicle according to claim 4, wherein the reversal detection unit detects reversal of the steering direction of the steering handle when the reversal of the steering direction of the steering handle continues for a predetermined time or more. Steering assist device. The steering assist device for a vehicle according to any one of claims 1 to 5, further comprising:
A vehicle steering assist device, comprising: an absorption circuit that absorbs regenerative electric power from the electric motor during regenerative braking operation of the electric motor. The vehicle steering assist device according to any one of claims 1 to 6, further comprising:
A vehicle steering assist device comprising a voltage rise prevention circuit for preventing a voltage due to a regenerative braking operation of the electric motor from rising to a predetermined voltage or more.   The regenerative braking control means controls the operation control circuit so that a regenerative current generated by the electric motor circulates to the electric motor via the operation control circuit. A vehicle steering assist device according to any one of the above. The regenerative braking control means switches and controls the operation control circuit when the voltage between the terminals of the electric motor by the regenerative braking operation rises to a predetermined voltage or higher so that the regenerative current by the electric motor flows to the power system side. The vehicle steering assist device according to claim 8, further comprising a switching unit configured to turn on the vehicle.

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