JP2006264617A - Steering device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering device for a vehicle capable of enhancing operability of the vehicle. <P>SOLUTION: The steering device for the vehicle provided with a steering auxiliary means for giving steering auxiliary torque to steering torque generated by steering of a driver so as to assist the steering is provided with a deflection state determination means for determining whether or not the vehicle is in the deflection state; and a deflection suppression torque calculation means for calculating deflection suppression torque for suppressing the deflection state of the vehicle. When it is determined by the deflection state determination means that the vehicle is in the deflection state, the steering auxiliary means gives the steering auxiliary torque based on the deflection suppression torque calculated by the deflection suppression torque calculation means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle steering apparatus with improved operability.

2. Description of the Related Art Conventionally, there is known an electric power steering device that increases a target value for driving a motor when a steering torque detected in a straight traveling state is a predetermined value or more (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 2002-274406

  However, in the above-described conventional electric power steering device, the assist torque of the electric power steering is increased so that the steering assist is more accurately performed when the steering torque during the straight traveling of the vehicle exceeds a predetermined value. Yes. Therefore, when the steering torque exceeds a predetermined value, only the driver's operating force is reduced, the vehicle's deflection state that occurs during normal vehicle travel is always suppressed, and the driver's operating burden is reduced. It does not reduce.

  The present invention has been made to solve such problems, and its main object is to improve the operability of the vehicle.

  One aspect of the present invention for achieving the above object is a vehicle steering apparatus including a steering assist means for adding a steering assist torque so as to assist the steering with respect to a steering torque generated by a driver's steering. And a deflection state determination means for determining whether or not the vehicle is in a deflection state, and a deflection suppression torque calculation means for calculating a deflection suppression torque that suppresses the deflection state of the vehicle. When the determination means determines that the vehicle is in the deflection state, the steering assist means adds the steering assist torque based on the deflection suppression torque calculated by the deflection suppression torque calculation means. This is a vehicle steering device.

  In this aspect, the vehicle is in a deflected state, for example, a state in which the vehicle swings in the left-right direction (a state in which the vehicle does not go straight) when the steering is in a neutral position.

  According to this aspect, when the deflection state determination means determines that the vehicle is in the deflection state, the steering assist means is based on the deflection suppression torque calculated by the deflection suppression torque calculation means. The steering assist torque is added. As a result, when the vehicle is in a deflected state, the steering assist means adds a steering assist torque that suppresses the deflected state of the vehicle to the steering shaft or the like. Therefore, since the steering force by the driver for suppressing the deflection state of the vehicle is always reduced, the operability of the vehicle is improved.

  In this aspect, the deflection suppression torque calculating unit may calculate the deflection suppression torque so that the steering torque in a straight traveling state of the vehicle becomes zero. Thereby, the deflection state of the vehicle is automatically suppressed without applying the steering force by the driver. Therefore, since the driver does not feel the vehicle deflection state, the operability of the vehicle is greatly improved.

  Furthermore, in this one aspect, a steering torque is generated by adding the steering assist torque to the steering torque by the steering assisting means, and the deflection suppression torque calculating means is generated in a straight traveling state of the vehicle. The deflection suppression torque may be calculated based on the turning torque.

  In this aspect, when the vehicle is not in a straight traveling state, the steering assist means may add the steering assist torque based on the deflection suppression torque and the steering torque calculated by the deflection suppression torque calculation means. Good. As a result, even when the vehicle is not in a straight traveling state such as a turning state, the steering assist means adds a steering assist torque that suppresses the deflection state of the vehicle to the steering shaft or the like. Therefore, even when the vehicle is not in a straight traveling state, the steering force when the driver suppresses the deflection state of the vehicle is always reduced.

  In this aspect, the steering assist means is an electric motor that adds the steering assist torque based on a steering assist torque command value, and the deflection suppression torque calculation means includes the steering torque in the vehicle straight traveling state and the vehicle straight traveling state. The correction command value may be calculated based on the steering assist torque command value. Thereby, the electric motor can always suppress the deflection state of the vehicle in the straight traveling state by adding the steering assist torque based on the correction command value calculated by the deflection suppression torque calculating means.

  In this aspect, a nonvolatile storage unit that stores the correction command value may be further included. Thus, for example, even when the power source is turned off, such as when an IG (ignition) switch is turned off, the correction command value is held in the storage unit. Therefore, immediately after the IG switch is turned off and then turned on, the electric motor can apply the steering assist torque based on the correction command value held in the storage means, and can always suppress the deflection state of the vehicle.

  In this aspect, the vehicle further includes: an operation state detection unit that detects an operation state of the steering of the vehicle; and a traveling state detection unit that detects a traveling state of the vehicle, and the vehicle state is detected by the traveling state detection unit. In addition, when the operation state detection unit detects that the steering is not in the neutral position, the deflection state determination unit may determine that the vehicle is in a deflection state. When the vehicle is deflected, the driver performs a steering operation to maintain the vehicle straight traveling state, so that it can be determined that the neutral position of the steering is shifted.

  In this aspect, the apparatus further comprises torque detection means for detecting the steering torque or the steering torque, and traveling state detection means for detecting the traveling state of the vehicle, and the steering torque or the turning torque is detected by the torque detection means. When the steering torque is detected and the straight traveling state of the vehicle is detected by the traveling state detection unit, the deflection state determination unit may determine that the vehicle is in a deflection state. When the vehicle is deflected, the driver performs a steering operation in order to maintain the vehicle straight traveling state. Therefore, it can be determined that steering torque or steering torque is generated.

  In this aspect, the steering torque detected by the torque detection means is further provided with torque detection means for detecting the steering torque or the steering torque, and travel state detection means for detecting the travel state of the vehicle. Alternatively, when the turning torque becomes a minimum value and the traveling state detected by the traveling state detection unit is not a straight traveling state, the deflection state determination unit may determine that the vehicle is in a deflection state. Thereby, the deflection state determination means can determine the deflection state of the vehicle when the traveling state is not the straight traveling state.

  In this one aspect, for example, the traveling state detection means may include a yaw angular velocity sensor and / or a vehicle speed sensor.

  According to the present invention, the operability of the vehicle can be improved.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the accompanying drawings. Note that the basic concept, main hardware configuration, operating principle, basic control method, and the like of the vehicle steering apparatus are known to those skilled in the art, and thus detailed description thereof is omitted.

  FIG. 1 is a schematic diagram showing a system configuration of a vehicle steering apparatus according to an embodiment of the present invention. The vehicle steering apparatus 1 according to the present embodiment is provided in a steering mechanism 3 that steers wheels by steering a steering hole 3a by a driver, and applies a steering assist torque to the steering torque input to the steering wheel 3a by the driver. It has a function to add.

  The steering mechanism 3 has a steering wheel 3a operated by a driver, and a steering shaft 3b connected to the steering wheel 3a. A pinion 3c is connected to the tip of the steering shaft 3b, and a rack shaft 3d extending in the vehicle width direction meshes with the pinion 3c. Tie rods 3e are coupled to both ends of the rack shaft 3d, and knuckle arms 3f that support left and right front wheels as steered wheels are coupled to each tie rod 3e.

  In such a steering mechanism 3, when the steering wheel 3a is operated and the steering shaft 3b and the pinion 3c rotate, the linear movement of the rack shaft 3d in the vehicle width direction is converted via the so-called rack and pinion 3c and 3d. This linear motion is converted into a rotational motion around the kingpin axis of the knuckle arm 3f, and the left and right front wheels are steered.

  The steering shaft 3b has an input shaft connected to the steering wheel 3a, and an output shaft having one end connected to the input shaft and the other end connected to the pinion 3c. The input shaft and the output shaft are connected via a torsion bar 3g that causes torsion according to the direction and magnitude of the steering torque applied to the steering wheel 3a. The torsion bar 3g is provided with a torque sensor 5 that detects the direction and magnitude of the steering torque by detecting the relative angular displacement between the input shaft and the output shaft.

  An actuator 7 such as an electric motor is connected to either the output shaft of the steering shaft 3b or the rack shaft 3d via a speed reduction mechanism, and the steering assist torque generated by the electric motor 7 is reduced to a predetermined speed reduction ratio by the speed reduction mechanism. Is transmitted to the steering shaft 3b of the steering mechanism 3 as steering assist torque.

  An EPS-ECU (electronic control unit for electric power steering) 9 is connected to the electric motor 7, and the electric motor 7 applies steering assist torque to the steering shaft 3b or the rack shaft 3d based on a control signal from the EPS-ECU 9. Append.

  An EPS-ECU (Electronic Control Unit) 9 is composed of a microcomputer, and executes various processes according to control and calculation programs, and controls each part of the apparatus (Central Processing Unit), an execution program for the CPU. ROM (Read Only Memory) for storing data, readable and writable EEPROM (Programmable Read-Only Memory) for storing operation results, and the like, nonvolatile memory 9a such as RAM (Random Access Memory), timer, counter, input interface, and the like Has an output interface.

  The EPS-ECU 9 is connected to a vehicle speed sensor 11 that detects the vehicle speed and a yaw rate sensor (yaw angular velocity sensor) 13 that detects the yaw rate (traveling direction) of the vehicle. As the yaw rate sensor 13, a vibration type late gyro, a mechanical late gyro, or the like is used.

  The EPS-ECU 9 has basic target current calculation means 9 b that calculates a basic target current value of the electric motor 7 based on the steering torque (current value) from the torque sensor 5. Note that the basic target current value is a current value of the electric motor 7 corresponding to a steering assist torque added in a normal steering operation. The relationship between the basic target current value and the steering assist torque is stored in advance in the ROM of the EPS-ECU 9.

  The EPS-ECU 9 includes a traveling state detection unit 9c that detects a traveling state such as a straight traveling state or a turning state of the vehicle based on the vehicle speed from the vehicle speed sensor 11 and the yaw rate from the yaw rate sensor 13.

  The torque sensor 5 and the traveling state detection means 9c are connected to a deflection state determination means 9d that determines whether or not the vehicle is in a deflection state. The deflection state determination unit 9d determines whether or not the vehicle is in a deflection state based on the steering torque from the torque sensor 5 and the traveling state of the vehicle detected by the traveling state detection unit 9c.

  For example, the deflection state determination unit 9d integrates the steering torque (current value) from the torque sensor 5 for a predetermined time while the vehicle straight traveling state is detected by the traveling state detection unit 9c, and calculates an average value of the integrated values. Calculate (FIG. 2). Further, the deflection state determination means 9d determines that the vehicle is in the deflection state when the average value of the steering torque is greater than or equal to a predetermined threshold value, and determines that an operation for correcting the deflection state is being performed by the driver.

  A deflection suppression torque calculator 9e for calculating a correction command value (current value) for calculating the steering assist torque is connected to the deflection state determination unit 9d.

  The deflection suppression torque calculation unit 9e calculates a corrected steering torque value based on the average value of the steering torque calculated by the deflection state determination unit 9d. Here, the corrected steering torque is a steering torque required when the driver tries to correct the deflection state of the vehicle.

  The deflection suppression torque calculator 9e calculates a steering assist torque command value based on the corrected steering torque value and a predetermined relationship (FIG. 3) between the corrected steering torque value and the steering assist torque command value (current value). The predetermined relationship between the corrected steering torque value by the driver and the steering assist torque command value is stored in advance in the ROM of the EPS-ECU 9.

  Further, the deflection suppression torque calculation means 9e calculates a correction command value (current value) by adding the correction steering torque value and the steering assist torque command value.

  A final target current calculation means 9f for calculating a final current value to be output to the electric motor 7 is connected to the basic target current calculation means 9b and the deflection suppression torque calculation means 9e.

  The final target current calculation means 9f calculates the final target current value by adding the correction command value calculated by the deflection suppression torque calculation means 9e to the basic target current value calculated by the basic target current calculation means 9b. .

  The final target current value calculated by the final target current calculation means 9f is sent to the electric motor 7 via the driver, and the electric motor 7 is driven based on this final target current value, and the steering assist torque is applied to the steering shaft 3b. Is added.

  A non-volatile EEPROM 9a is connected to the deflection suppression torque calculation means 9e, and a correction command value calculated by the deflection suppression torque calculation means 9e is stored in the EEPROM 9a.

  Since the correction command value is stored and held in the nonvolatile EEPROM 9a, the correction command value is not erased even when, for example, the IG (ignition) switch is turned off and the EPS-ECU 9 is turned off. It is held in the EEPROM 9a. Therefore, immediately after the IG switch is turned from the OFF state to the ON state, the EPS-ECU 9 can execute deflection control described later based on the correction command value held in the EEPROM 9a.

  The correction command value is always calculated by the deflection suppression torque calculation means 9e, and the correction command value stored in the EEPROM 9a is constantly rewritten and updated to the latest state.

  The basic target current calculation means 9b, final target current calculation means 9f, travel state detection means 9c, deflection state determination means 9d, and deflection suppression torque calculation means 9e described above are realized by a program in the EPS-ECU 9.

  By the way, when the steering wheel 3a is held in the neutral position and the vehicle is maintained in a straight traveling state or the like, the difference in air pressure between the left and right tires, the difference in friction coefficient between the left and right in the steering mechanism 3, the zero point value or temperature of the torque sensor 5 The above-described vehicle deflection state may occur due to a left-right difference or the like due to a change.

  The EPS-ECU 9 configured as described above to suppress this vehicle deflection state is based on the vehicle speed from the vehicle speed sensor 11, the yaw rate from the yaw rate sensor 13, and the steering torque from the torque sensor 5. To control. A control processing flow of the vehicle steering apparatus 1 will be described below.

  FIG. 4 is a flowchart showing a flow of control processing of the vehicle steering apparatus 1.

  The control routine shown in FIG. 4 is repeatedly executed every predetermined minute time, for example, every 64 ms.

  Based on the vehicle speed from the vehicle speed sensor 11 and the yaw rate from the yaw rate sensor 13, the traveling state detection means 9c detects a vehicle traveling state such as a straight traveling state or a turning state (S100).

  Next, the deflection state determination unit 9d determines whether or not the vehicle is in a deflection state based on the average value of the steering torque from the torque sensor 5 and the vehicle traveling state detected by the traveling state detection unit 9c ( S110).

  When the deflection state determination means 9d determines that the vehicle is in a deflection state, the deflection suppression torque calculation means 9e calculates a correction command value, and the calculated correction command value is written to the EEPROM 9a (S120). On the other hand, when the deflection state determination means 9d determines that the vehicle is not in the deflection state, the routine by this control process is terminated.

  Thereafter, the final target current calculation means 9f calculates the final target current value by adding the correction command value calculated by the deflection suppression torque calculation means 9e to the basic target current value calculated by the basic target current calculation means 9b. (S130).

  The final target current calculated by the final target current calculation means 9f is supplied to the electric motor 7 through a driver, and the electric motor 7 is driven based on this final target current and adds steering assist torque to the steering shaft 3b. (S140). Thereby, the deflection of the vehicle is suppressed.

  As described above, when the deflection state determination unit 9d determines that the vehicle is in the deflection state, the deflection suppression torque calculation unit 9e calculates a correction command value, and the final target current calculation unit 9f is based on the calculated correction command value. The final target current value is calculated. Furthermore, the electric motor 7 is driven based on the final target current, and adds a steering assist torque to the steering shaft 3b. As a result, when the vehicle is in a deflected state, a steering assist torque substantially the same as the corrected steering torque by the driver is applied to the steering shaft 3b. Therefore, the steering force by the driver is reduced, and the operability of the vehicle is improved.

  As mentioned above, although the best mode for carrying out the present invention has been described using one embodiment, the present invention is not limited to such one embodiment, and within the scope not departing from the gist of the present invention, Various modifications and substitutions can be made to the above-described embodiment.

  The present invention can be used for a vehicle steering apparatus. The appearance, weight, size, running performance, etc. of the vehicle to be mounted are not limited.

It is the schematic which shows the system configuration | structure of the vehicle steering apparatus which concerns on one Example of this invention. It is a figure which shows the steering torque value output from a torque sensor, the average value, and a predetermined threshold value. It is a figure which shows the relationship between a correction steering torque value and a steering assist torque command value. It is a flowchart which shows the flow of control processing of the steering device for vehicles.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle steering device 3 Steering mechanism 3a Steering wheel 3b Steering shaft 5 Torque sensor 7 Electric motor (steering assist means)
9 EPS-ECU
9a EEPROM (memory means)
9b Basic target current calculation means 9c Traveling state detection means 9d Deflection state determination means 9e Deflection suppression torque calculation means 9f Final target current calculation means 11 Vehicle speed sensor (traveling state detection means)
13 Yaw rate sensor (running state detection means)

Claims (10)

A vehicle steering apparatus comprising steering assist means for adding a steering assist torque so as to assist the steering with respect to a steering torque generated by a driver's steering,
Deflection state determination means for determining whether or not the vehicle is in a deflection state;
Deflection suppression torque calculation means for calculating a deflection suppression torque that suppresses the deflection state of the vehicle, and
When the deflection state determination unit determines that the vehicle is in the deflection state, the steering assist unit adds the steering assist torque based on the deflection suppression torque calculated by the deflection suppression torque calculation unit. A vehicle steering apparatus characterized by the above. The vehicle steering device according to claim 1,
The vehicle steering apparatus according to claim 1, wherein the deflection suppression torque calculating unit calculates the deflection suppression torque so that the steering torque is zero when the vehicle is traveling straight. The vehicle steering apparatus according to claim 1,
A steering torque is generated by adding the steering assist torque to the steering torque by the steering assist means,
The vehicle steering apparatus according to claim 1, wherein the deflection suppression torque calculating unit calculates the deflection suppression torque based on the steering torque generated in a straight traveling state of the vehicle. The vehicle steering apparatus according to any one of claims 1 to 3,
When the vehicle is not in a straight traveling state, the steering assist means adds the steering assist torque based on the deflection suppression torque and the steering torque calculated by the deflection suppression torque calculation means. Steering device. The vehicle steering device according to any one of claims 1 to 4,
The steering assist means is an electric motor that adds the steering assist torque based on a steering assist torque command value.
The vehicle steering apparatus according to claim 1, wherein the deflection suppression torque calculating unit calculates a correction command value based on the steering torque in a straight traveling state of the vehicle and the steering assist torque command value in a straight traveling state of the vehicle. The vehicle steering device according to claim 5,
A vehicle steering apparatus further comprising a non-volatile storage means for storing the correction command value. The vehicle steering apparatus according to any one of claims 1 to 6,
An operation state detecting means for detecting an operation state of the steering of the vehicle;
A traveling state detecting means for detecting a traveling state of the vehicle,
When the vehicle state is detected by the running state detecting unit and the steering state is not detected by the operation state detecting unit, the deflection state determining unit determines that the vehicle is in a deflected state. A vehicle steering apparatus characterized by the above. The vehicle steering apparatus according to any one of claims 1 to 6,
Torque detecting means for detecting the steering torque or the steering torque;
A traveling state detecting means for detecting a traveling state of the vehicle,
When the steering torque or the turning torque is detected by the torque detection means, and the straight traveling state of the vehicle is detected by the traveling state detection means, the deflection state determination means determines that the vehicle is in a deflection state. A vehicle steering apparatus characterized by the above. The vehicle steering apparatus according to any one of claims 1 to 6,
Torque detecting means for detecting the steering torque or the steering torque;
A traveling state detecting means for detecting a traveling state of the vehicle,
When the steering torque or the turning torque detected by the torque detecting means is a minimum value and the traveling state detected by the traveling state detecting means is not a straight traveling state, the deflection state determining means A vehicle steering apparatus characterized by determining that the vehicle is in a state. A vehicle steering apparatus according to any one of claims 7 to 9,
The vehicle steering apparatus according to claim 1, wherein the running state detecting means includes a yaw angular velocity sensor and / or a vehicle speed sensor.

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