JP2006199149A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device capable of smoothly starting a vehicle for steering wheel operation. <P>SOLUTION: This is an electric power steering device which performs steering assistance by driving a motor 10 in accordance with the steering wheel operation. It is constituted by providing a torque sensor 11 for detecting a steering torque of the steering wheel 2 and a steering angle sensor 12 for detecting the steering angle of the steering wheel 2. The steering assistance amount is set based on the steering torque when the steering angle of the steering wheel 2 is not within a steering torque dead zone, and the steering assistance amount is set based on the steering wheel angle when the steering angle of the steering wheel 2 is within the steering torque dead zone, thus performing assistance control. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electric power steering device mounted on a vehicle.

Conventionally, as an electric power steering device mounted on a vehicle, as described in Japanese Patent Application Laid-Open No. 2003-191856, a driving force of an electric motor is transmitted to a steering mechanism to assist steering, and steering torque There is known a motor that drives an electric motor in a direction opposite to the steering torque when is less than a predetermined value. This electric power steering apparatus is intended to improve the steering feeling in the dead zone near the steering angle midpoint by driving the electric motor in the direction opposite to the steering torque.
JP 2003-191856 A

  However, even with such a device, since the steering force is not sufficiently transmitted in the dead zone near the steering angle midpoint, the start of movement of the vehicle at the initial stage of steering cannot be accelerated. In particular, when the steering force transmission mechanism from the steering wheel to the electric motor has a backlash or a low-rigidity part, the start of movement of the vehicle is further delayed with respect to the steering wheel.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an electric power steering device that makes a vehicle move smoothly in response to a steering operation.

  That is, the electric power steering apparatus according to the present invention detects a steering torque input to the steering force transmission mechanism by the steering operation of the steering wheel in the electric power steering apparatus that performs the steering assist by driving the motor according to the steering wheel operation. Steering torque detection means, steering angle detection means for detecting the steering angle of the steering wheel, and whether or not the steering angle of the steering wheel is in a steering torque insensitive region based on the steering angle detected by the steering angle detection means When the steering angle of the steering wheel is not in the steering torque insensitive region, the steering assist amount is set based on at least the steering torque, and the steering angle of the steering wheel is in the steering torque insensitive region. In this case, the steering assist amount is set based on at least the steering angle of the steering wheel, and assist control is performed. It is constituted by a Cormorant assist control means.

  According to the present invention, when the steering angle of the steering wheel is in the steering torque insensitive region, the steering assist amount is set based on the steering angle of the steering wheel and the assist control is performed, so that the operation position of the steering wheel is in the steering torque insensitive region. But steering assist can be done. For this reason, it is possible to smoothly start the vehicle in response to the steering operation. Further, discontinuous control due to the steering torque insensitive region can be avoided, continuity of control can be ensured, and smooth assist control can be performed.

  According to the present invention, it is possible to smoothly start the vehicle with respect to the steering wheel.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a schematic configuration diagram of an electric power steering apparatus according to the first embodiment.

  As shown in FIG. 1, the electric power steering apparatus 1 according to the present embodiment is an apparatus that performs steering assist by driving a motor 10 in accordance with the steering force of the handle 2. The electric power steering device 1 is mounted on a vehicle and performs steering assist by applying an assist force to a steering force transmission mechanism of the vehicle. The vehicle steering force transmission mechanism is a mechanism for transmitting a steering force and rotational displacement applied to the steering wheel 2 to the steered wheels 7, and includes, for example, a steering shaft 3, a gear portion 5, and a tie rod 6 as main components. The steering shaft 3 is connected to the handle 2 and transmits the steering force and rotational displacement of the handle 2 to the gear unit 5 side.

  The gear unit 5 converts the steering torque transmitted from the steering shaft 3 into a horizontal force. As the gear mechanism of the gear unit 5, for example, a rack and pinion type is used. In the gear portion 5, the pinion 51 is rotated by the steering torque transmitted through the steering shaft 3, the rack 52 that meshes with the pinion 51 is moved, and the steering force is transmitted to the tie rod 6 by the movement of the rack 52. The steered wheel 7 is steered by the movement of the tie rod 6.

  The gear unit 5 is provided with a motor 10. The motor 10 is an actuator for applying an assist force to the steering force transmission mechanism, and for example, applies an assist force to the rack 52. The gear unit 5 is provided with a torque sensor 11. The torque sensor 11 functions as steering torque detection means for detecting steering torque, and is installed between the steering shaft 3 and the pinion 51, for example.

  As the torque sensor 11, it is preferable to use a sensor that can detect the rotation angle of the pinion 51. For example, a torsion bar disposed between the steering shaft 3 and the pinion 51 is provided, and a first rotation sensor that detects the rotation angle on the steering shaft 3 side and a second rotation sensor that detects the rotation angle on the pinion 51 side are provided. And configured to detect the steering torque based on the difference in rotation angle between the first rotation sensor and the second rotation sensor.

  The electric power steering apparatus 1 is provided with a steering angle sensor 12. The steering angle sensor 12 functions as a steering angle detection unit that detects the steering angle of the handle 2. The steering angle sensor 12 is provided on the steering shaft 3, for example.

  Further, the electric power steering apparatus 1 is provided with an ECU (Electronic Control Unit) 20. The ECU 20 performs control processing for the entire apparatus, and includes, for example, a CPU, a ROM, a RAM, an input signal circuit, an output signal circuit, a power supply circuit, and the like. The ECU 20 functions as an assist control unit that sets a steering assist amount and drives the motor 10 in accordance with the steering assist amount.

  The ECU 20 is connected to the motor 10, outputs a drive signal to the motor 10, and inputs a rotation angle signal output from the motor 10. The ECU 20 is connected to the torque sensor 11 and receives a detection signal output from the torque sensor 11. The ECU 20 is connected to the steering angle sensor 12 and receives a detection signal output from the steering angle sensor 12. Further, the ECU 20 is connected to the vehicle speed sensor 21 and inputs a detection signal output from the vehicle speed sensor 21. The vehicle speed sensor 21 is a sensor that detects the traveling speed of the vehicle.

  Next, the operation of the electric power steering apparatus 1 according to this embodiment will be described.

  FIG. 2 is a flowchart regarding the operation of the electric power steering apparatus 1 according to the present embodiment. The control process in the flowchart of FIG. 2 is started, for example, when the vehicle ignition is turned on, and is repeatedly executed by the ECU 20 every predetermined time. First, as shown in S10 of FIG. 2, a sensor detection signal reading process is performed. That is, the steering torque is read based on the detection signal of the torque sensor 11, the vehicle speed is read based on the detection signal of the vehicle speed sensor 21, and the steering wheel steering angle is read based on the detection signal of the steering angle sensor 12.

  Then, the process proceeds to S12, and it is determined whether or not the steering angle of the handle 2 is in the steering torque insensitive region. That is, it is determined whether or not the steering wheel steering angle is in a steering torque insensitive region in the steering force transmission mechanism.

  Here, the steering torque insensitive region means a region of a steering angle where the steering force is not transmitted to the steered wheels 7 due to the backlash and low rigidity of the steering force transmission mechanism even when the steering wheel 2 is steered. Examples of the steering torque insensitive region include a region from the steering wheel neutral position to a predetermined steering angle and a region to a predetermined steering angle when the steering wheel 2 is turned back. Whether or not the steering angle of the steering wheel 2 is in the steering torque insensitive region may be determined based on the steering wheel steering angle.

  When it is determined in S12 that the steering angle of the steering wheel 2 is not in the steering torque insensitive region, normal assist control is performed. The normal assist control is, for example, control for steering assist by driving the motor 10 based on the assist amount determined by the steering torque and the vehicle speed.

  On the other hand, if it is determined in S12 that the steering angle of the steering wheel 2 is in the steering torque insensitive region, steering angle assist control is performed. The steering angle assist control is a control for setting a steering assist amount according to the steering angle of the steering wheel 2 and driving the motor 10 based on the assist amount to perform a steering assist.

  For example, as shown in FIG. 3, when the steering operation is turned from the neutral position, the motor 10 is driven based on the assist amount set according to the steering angle of the steering wheel 2 to perform the steering assist. In this case, the assist setting is performed so that the assist amount decreases as the steering angle moves away from the neutral position.

  As shown in FIG. 4, when the steering wheel operation is switched back, the motor 10 is driven based on the assist amount set according to the steering angle of the steering wheel 2 to perform the steering assist. In this case, the assist setting is performed so that the assist amount decreases as the steering angle moves away from the switchback position.

  3 and 4, it is preferable to add an assist gain according to the vehicle speed to the assist amount set based on the steering angle in the assist control in the steering torque insensitive region.

  For example, as shown in FIG. 5, the assist gain is set such that the assist gain is increased as the vehicle speed decreases, and the assist gain corresponding to the vehicle speed is added to the assist amount set based on the steering angle, and the assist control is performed. . In this case, appropriate assist control according to the vehicle speed is possible.

  In the assist control in the steering torque insensitive region of FIGS. 3 and 4, it is preferable to add an assist gain corresponding to the steering speed to the assist amount set based on the steering angle.

  For example, as shown in FIG. 6, the assist gain is set such that the assist gain is increased as the steering speed is decreased, and the assist gain corresponding to the steering speed is added to the assist amount set based on the steering angle. I do. In this case, it is possible to perform appropriate assist control according to the steering speed.

  Here, detection of the steering torque insensitive region will be described.

  First, as an initial setting of the electric power steering apparatus 1, the neutral point of the torque sensor 11 is detected by setting the handle 2 to the neutral position at the time of factory shipment. Then, the motor 10 is driven to move the rack 52, the pinion 51 is rotated, and the steering shaft 3 and the handle 2 are rotated.

  At this time, as shown in FIG. 7, the rotation angle θst of the handle 2 and the rotation angle θp of the pinion 51 cause a rotation difference with respect to the rotation angle of the motor 10. For example, even if the motor 10 is rotated, the pinion 51 and the handle 2 do not rotate at the beginning of the rotation due to the backlash and low rigidity of the steering force transmission mechanism. When the motor 10 rotates to some extent, the pinion 51 starts to rotate, and then the handle 2 starts to rotate. At this time, if the motor rotation angle at which the handle 2 starts to rotate is Δθ1, and the rotation angle of the pinion 51 when the handle 2 starts to rotate is Δθ0r (clockwise) and Δθ01 (counterclockwise), these Δθ1, Δθ0r, A steering torque insensitive region in the steering force transmission mechanism can be calculated based on a rotation angle difference such as Δθ01.

  As described above, according to the electric power steering apparatus 1 according to the present embodiment, when the steering angle of the handle 2 is in the steering torque insensitive region, the steering assist amount is set based on the steering angle and the assist control is performed. Thus, the steering assist can be performed even when the operation position of the handle 2 is in the steering torque insensitive region. For this reason, it is possible to smoothly start the vehicle in response to the steering operation. Further, discontinuous control due to the steering torque insensitive region can be avoided, continuity of control can be ensured, and smooth assist control can be performed.

  In the present embodiment, a rack assist type device has been described as the electric power steering device. However, the electric power steering device may be applied to other types of electric power steering devices such as a column assist type.

1 is a schematic configuration diagram of an electric power steering apparatus according to an embodiment of the present invention. It is a flowchart about operation | movement of the electric power steering apparatus of FIG. It is explanatory drawing of the steering angle assist control process in the electric power steering apparatus of FIG. It is explanatory drawing of the steering angle assist control process in the electric power steering apparatus of FIG. It is explanatory drawing of the steering angle assist control process in the electric power steering apparatus of FIG. It is explanatory drawing of the steering angle assist control process in the electric power steering apparatus of FIG. It is explanatory drawing of the steering torque insensitive area detection in the electric power steering apparatus of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus, 2 ... Handle, 3 ... Steering shaft, 5 ... Gear part, 6 ... Tie rod, 7 ... Steering wheel, 10 ... Motor, 11 ... Torque sensor, 12 ... Steering angle sensor, 20 ... ECU, 21 ... Vehicle speed sensor, 51 ... Pinion, 52 ... Rack.

Claims (1)

In an electric power steering device that performs steering assist by driving a motor according to a steering wheel operation,
Steering torque detection means for detecting a steering torque input to the steering force transmission mechanism by the steering operation of the steering wheel;
Steering angle detection means for detecting the steering angle of the steering wheel;
A dead area determining means for determining whether the steering angle of the steering wheel is in a steering torque insensitive area based on a steering angle detected by the steering angle detecting means;
When the steering angle of the steering wheel is not in the steering torque insensitive region, a steering assist amount is set based on at least the steering torque, and when the steering angle of the steering wheel is in the steering torque insensitive region, at least the steering wheel An assist control means for setting a steering assist amount based on the steering angle and performing assist control;
An electric power steering apparatus comprising:

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