JP3720979B2 - Electric power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric power steering device that generates a steering assist force by the rotational force of an electric motor.
[0002]
[Prior art]
In a conventional electric power steering device equipped in a four-wheel vehicle, generally, a steering assist force is determined according to a steering torque (a reaction force from the road surface) and a vehicle speed. Therefore, a relatively large steering assist force is applied to the steering mechanism when the steering resistance is large when the vehicle is stopped or traveling at low speed, and conversely, a relatively small steering assist force is applied to the steering mechanism because the steering resistance is small during high speed traveling. It is a mechanism to give.
[0003]
[Problems to be solved by the invention]
By the way, even if a steering assist force corresponding to the steering torque and the vehicle speed is applied to the steering mechanism, the steering assist force is too small (for example, the steering wheel is still heavy) when the driver is a woman or a man. May feel that the steering assist force is too large (the steering wheel is too light), and the optimum steering assist force for the driver is not necessarily given. Similarly, there is a difference between whether the driver is a young person or an elderly person who feels that the steering assist force is large or small.
[0004]
As described above, in the conventional apparatus, the steering assist force is determined without considering the human characteristics of the driver, more specifically, the driver's force characteristics. Depending on the driver, a comfortable steering feeling is provided depending on the driver. There was a problem that there were things that I did not feel.
[0005]
Therefore, an object of the present invention is to provide an electric power steering apparatus that solves the above-described problems and can provide a more comfortable steering feeling to all drivers regardless of age or sex.
[0006]
[Means for Solving the Problems]
According to the first aspect of the present invention, in the electric power steering apparatus that generates the steering assist force by the rotational force of the electric motor, the force characteristic detection means for detecting the driver's force characteristic, and the force characteristic detected by the force characteristic detection means based on, viewed contains a means for changing a steering assist force generated by an electric motor, wherein the force characteristic detection means, the electromyographic measurement, for detecting the force characteristic by measuring the load on the muscles of the driver And an electrode disposed on the steering wheel so that the driver can come into contact with the palm of the driver when holding the steering wheel, and an impedance converter connected to the electrode. To do.
[0008]
According to the above-described configuration, the driver's force characteristic is detected, and the steering assist force is changed based on the detected force characteristic. The force characteristic indicates whether the driver's force is weak, normal, or strong. For example, when the driver's force is strong, a relatively small steering assist force is given to the steering mechanism, and conversely, the driver When the force is weak, a relatively large steering assist force is applied to the steering mechanism. The force characteristic is a value unique to the driver, and when this is detected, the steering assist force is changed. Therefore, the optimum steering assist force is given to the driver to the steering mechanism, and the driver has a comfortable steering fee. Get the ring.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0010]
FIG. 1 is a block diagram showing an electrical configuration of an electric power steering apparatus according to an embodiment of the present invention together with a sectional structure of a steering mechanism. The steering mechanism 1 is coupled to a rack 11 disposed along the vehicle width direction, a pinion shaft 12 having a pinion portion engaged with the rack 11 in a gear box 17 at a tip, and both ends of the rack 11 to be rotatable. A tie rod 13 and a knuckle arm 14 rotatably coupled to the tip of the tie rod 13. The knuckle arm 14 is rotatably provided around the kingpin 15, and a steering wheel (usually a front wheel) 16 is attached to the knuckle arm 14. A base end portion of the pinion shaft 12 is coupled to a steering shaft via a universal joint, and a steering wheel is fixed to one end of the steering shaft (none of which is shown). With this configuration, by rotating the steering wheel, the rack 11 is displaced in the longitudinal direction thereof, the knuckle arm 14 is rotated around the kingpin 15, and the direction of the steering wheel 16 is changed.
[0011]
An electric power steering apparatus 2 for applying a steering assist force to the steering mechanism 1 includes a three-phase brushless motor M provided in association with a middle portion of the rack 11 and drive control of the motor M via a motor driver 21. And a controller 20 for performing the operation.
[0012]
The controller 20 includes a vehicle speed sensor 22 that detects the vehicle speed, a torque sensor 23 that detects the steering torque, a motor rotation angle sensor 24 that detects the rotation angle of the motor M, and a force characteristic detection sensor 25 that characterizes this embodiment. Each output signal is input. Based on the output signals of these sensors 22, 23, 24, 25, as will be described later, the controller 20 controls the drive current of the motor M, thereby increasing or decreasing the steering assist force applied to the steering mechanism 1.
[0013]
The vehicle speed sensor 22 is realized, for example, by a wheel speed sensor that is provided in association with a wheel and outputs a pulse signal at a cycle corresponding to the rotation speed of the wheel. In this case, the vehicle speed, which is the speed of the vehicle, can be obtained by measuring the period or frequency of the pulse signal.
[0014]
The torque sensor 23 divides the steering shaft into an input shaft on the steering wheel side and an output shaft on the pinion shaft 12 side, and connects the input shaft and the output shaft with a torsion bar. This is realized by a configuration for detecting the amount of twist. That is, since the torque applied to the steering wheel and the twist amount of the torsion bar correspond one-to-one, the steering torque can be detected by detecting the twist amount with an appropriate detection mechanism such as a potentiometer.
[0015]
The motor rotation angle sensor 24 is composed of a rotary encoder or the like, and detects the position or displacement amount of the rack 11 in the vehicle width direction through detection of the rotation angle of the motor M, thereby detecting the steering angle or the steering angle change amount. Be able to.
[0016]
The force characteristic detection sensor 25 is a sensor that detects a driver's force characteristic. For example, as shown in FIG. 2, the sensor 25 includes an electrode 51 disposed on the steering wheel 50 and an impedance converter 52 connected to the electrode 51. The electrode 51 is disposed at a position of the steering wheel 50 that is normally gripped by the driver (so-called 8:20 position, etc.). The electrode 51 is disposed flush with the surface of the steering wheel 50 so that the driver 51 can touch the palm of the driver without feeling uncomfortable when the driver grips the steering wheel 50.
[0017]
In addition, an impedance converter 52 is connected to the electrode 51 so that the influence of environmental noise picked up by the electrode 51 can be removed. More specifically, the palm of the driver contacts the electrode 51 when the driver holds the steering wheel 50. The body potential of the driver detected by the electrode 51 varies depending on the contact ratio, the contact pressure, and the like. Therefore, by passing the potential detected by the electrode 51 through the impedance converter 52, for example, an output of about μV is obtained, and the difference in the situation where the palm of the driver is in contact with the electrode 51, that is, the influence of environmental noise is removed. Has been. In other words, the detection capability of the electrode 51 is improved by using the electrode 51 as an active electrode.
[0018]
Returning to FIG. 1, the configuration related to the motor M will be outlined. A screw shaft portion 31 is formed in the middle of the rack 11, and a ball nut is inserted into the screw shaft portion 31 via a plurality of balls. 32 is screwed to form a ball screw mechanism 30. The rack 11 passes through the center of the motor M. A rotor 41 of the motor M is disposed so as to surround the rack 11, and a stator 42 of the motor M is disposed so as to surround the rotor 41. And the rotor 41 and the ball nut 32 are connected.
[0019]
Bearings 35 and 36 are interposed between the case 40 and the ball nut 32 of the motor M, and a bearing 37 is interposed between the case 40 and one end portion of the rotor 41. . A motor rotation angle sensor 24 is disposed at the one end of the rotor 41.
[0020]
With this configuration, when the motor M is energized to give torque to the rotor 41, the torque is transmitted to the ball nut 32 connected to the rotor 41. This torque is converted into a driving force of the rack 11 in the vehicle width direction by the ball screw mechanism 30. Thus, a steering assist force using the motor M as a drive source is applied to the steering mechanism 1.
[0021]
FIG. 3 is a flowchart for explaining processing for controlling the motor M by the controller 20. The controller 20 first fetches the output signal of the torque sensor 23 and vehicle speed sensor 22, to collect data about the steering torque T _V and the vehicle speed V (step S1, S2).
[0022]
Steering torque T _V, since in certain relation between the twist angle occurs in the torsion bar, is determined by detecting the twist angle.
[0023]
Figure 4 shows the torque voltage (steering torque) T _V outputted from the torque sensor 23, an example of the relationship between the twist angle generated on the torsion bar.
[0024]
As shown in FIG. 4, when the torque voltage TV output from the torque sensor 23 is 2.5 _V , the steering wheel is at the middle point, and neither left steering nor right steering is performed. When the steering wheel is steered to the right, the input shaft is rotated to the right, but the output shaft cannot follow the rotation of the input shaft due to a load, and the torsion bar is twisted. The torque voltage T _V of the torque sensor 23 changes corresponding to the twist of the torsion bar. When the steering wheel is steered to the right, the torque voltage T _V increases as the twist increases. Conversely, when the steering wheel is steered to the left, the torque voltage T _V of the torque sensor 23 decreases in proportion to the amount of twist. When the torque voltage T _V from the torque sensor 23 is in the range of 2.3 ≦ T _V ≦ 2.7, centering on 2.5 _V where the steering wheel is exactly at the middle point, the steering wheel is in the state of returning to the middle point. It can be said. Further, the range of the torque voltage T _V of 1.9 ≦ T _V ≦ 3.1 is a so-called play range of the steering wheel.
[0025]
When actually route of the vehicle steering wheel is steered is changed, in the case of right steering, the torque voltage T _V for example 3.1V or higher. In the case of left steering, the torque voltage TV is 1.9 _V or less.
[0026]
When data is collected for the steering torque T _V and the vehicle speed V, the then controller 20, based on the vehicle speed V, the determined vehicle speed coefficient Cv (step S3).
[0027]
The vehicle speed coefficient Cv is determined in advance according to the vehicle speed V, and decreases as the vehicle speed V increases. Actually, for example, the value of the vehicle speed coefficient Cv for the vehicle speed V = 5, 10, 30, 80 (km / h) is stored in the memory 20M (see FIG. 1) in the controller 20, and other than these values. The vehicle speed coefficient Cv with respect to the vehicle speed V is obtained by calculation such as linear interpolation processing.
[0028]
Next, the controller 20 takes in the force characteristic value P detected by the force characteristic detection sensor 25. This force characteristic value P is represented by −1 ≦ P ≦ + 1, for example. When the force characteristic value P is positive, that is, when 0 ≦ P ≦ + 1, it means that the driver's force is “weaker” than the average level. Further, when the force characteristic value P is negative, that is, when −1 ≦ P ≦ 0, it means that the driver's force is “stronger” than the average driver's force.
[0029]
Therefore, the relationship shown in FIG. 5 is set in advance between the detected force characteristic value P and the steering assist force T. As shown in FIG. 5, when the force characteristic value P is positive, α is added to the steering assist force T. Conversely, when the force characteristic value P is negative, α is subtracted from the steering assist force T. It is burned.
[0030]
Therefore, in step S5, the steering assist force is
Steering assist force T = Cv × steering torque T _V ± α
Is calculated as
[0031]
Then, a control signal is given to the motor driver 21 so that the obtained steering assist force T is obtained (step S6).
[0032]
The above processing is executed every minute time.
[0033]
Therefore, since the steering assist force according to the driver's force characteristic is generated, the driver can enjoy a more comfortable steering feeling.
[0034]
In the above description, the example in which the driver's force characteristic is detected by myoelectric measurement using the electrode 51 disposed on the steering wheel 50 has been described. However, the driver's force characteristic is detected by other sensors. Also good.
[0035]
In addition, the present invention can be variously modified within the scope of the claims.
[0036]
【The invention's effect】
According to the present invention, it is possible to provide an electric power steering apparatus having a favorable steering feeling that is suitable for the driver's force characteristics.
[0037]
In addition, according to the present invention, an electric power steering apparatus that does not generate excessive steering assist force can be provided, and an electric power steering apparatus that is excellent in energy saving effect without waste of energy can be obtained. it can.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an electrical configuration of an electric power steering apparatus according to an embodiment of the present invention together with a sectional structure of a steering mechanism.
FIG. 2 is an illustrative view showing one example of a force characteristic detection sensor according to one embodiment of the present invention;
FIG. 3 is a flowchart for explaining a steering assist force control operation;
[Figure 4] and the torque voltage T _V, is a graph showing the relationship between the twist angle.
FIG. 5 is a graph showing a relationship between a force characteristic value P and a steering assist force T.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steering mechanism 2 Electric power steering apparatus M Motor 20 Controller 22 Vehicle speed sensor 23 Torque sensor 25 Force characteristic detection sensor 51 Electrode 52 Impedance converter

Claims (1)

In the electric power steering device that generates the steering assist force by the rotational force of the electric motor,
Force characteristic detection means for detecting the driver's force characteristic;
Means for changing the steering assist force generated by the electric motor based on the force characteristic detected by the force characteristic detection means;
Only including,
The force characteristic detecting means is capable of contacting the driver's palm when the driver holds the steering wheel in order to detect the force characteristic by measuring the load on the driver's muscle by measuring the electromyogram. An electric power steering device comprising: an electrode disposed on a steering wheel; and an impedance converter connected to the electrode .

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