JPH06336174A - Electric power steering device - Google Patents

Abstract

PURPOSE:To reduce the kickback generated when a vehicle passes through a step and improve the steering feeling. CONSTITUTION:This electric power steering device is provided with a motor 5 assisting the steering force, a torque sensor 4 detecting the steering torque, a vehicle speed sensor 12 detecting the vehicle speed, ultrasonic sensors 18, 19 emitting ultrasonic waves toward the road surface in front of a vehicle and outputting the step detection signals according to the received intensity of the ultrasonic waves reflected from the road surface, a step judging function judging whether a step or the like exists or not on the road surface in front of the vehicle based on the step detection signals outputted from the ultrasonic sensors 18, 19, and a controller 15 gradually increasing then decreasing the current value outputted to the motor 5 during the period before and after the vehicle passes through the step or the like when the step or the like is judged to exist.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering device mounted on a vehicle, and particularly to an electric power steering device suitable for reducing kickback caused by passing a step on a vehicle to improve a steering feeling. The present invention relates to a power steering device.

[0002]

2. Description of the Related Art Conventionally, an electric power for determining a drive current value of an assist motor for assisting a steering force of a steering is determined based on a steering torque amount of a steering detected by a torque sensor and a vehicle speed detected by a vehicle speed sensor. Steering devices are being developed ("Automotive Technology")
1990, Vol. 44, 1 "Current status and future of electric power steering").

[0003]

By the way, kickback (force exerted from the wheel to the steering wheel) occurs when the vehicle rides on a step on the road surface while the vehicle is traveling. , Kickback control was not implemented. Therefore, in the related art, when the steering torque increases due to kickback caused by the vehicle passing through a step, the current of the assisting motor rapidly increases after the kickback occurs, and the steering becomes lighter. There is a problem in that the rider feels kickback and the like, and the driving feeling deteriorates.

[0004]

An object of the present invention is to improve the inconvenience of the above-mentioned conventional example, and in particular, by detecting the step on the road surface in front of the vehicle in advance and controlling the current output to the assisting motor, the step of the vehicle can be controlled. An object of the present invention is to provide an electric power steering device capable of reducing kickback and the like associated with passage and improving the driving feeling.

[0005]

According to the present invention, there is provided a motor for assisting a steering force of a steering wheel mounted on a vehicle, and a torque detecting means for detecting a steering torque of the steering wheel.
An electric power steering apparatus including a vehicle speed detecting means for detecting a vehicle speed, and a control means for determining a current value output to the motor based on the steering torque detected by the torque detecting means and the vehicle speed detected by the vehicle speed detecting means. In the above, in the above, the control means is provided with a road surface state detecting means for emitting an ultrasonic wave toward a road surface in front of the vehicle and outputting a road surface state detection signal according to a reception intensity of the ultrasonic wave reflected from the road surface, A step determination function that determines whether or not there is a step on the road surface in front of the vehicle based on the road state detection signal output from the detection means, and if it is determined that there is a step, before and after passing the step During this period, a current value control function of gradually increasing and then decreasing the current value output to the motor is provided.
This is intended to achieve the above-mentioned object.

[0006]

According to the present invention, when there is a step or the like on the road surface in front of the vehicle when the road surface state detecting means emits ultrasonic waves toward the road surface in front of the vehicle while the vehicle is traveling,
A road surface state detection signal corresponding to the presence of a step or the like is output. Thereby, the control means determines that there is a step or the like on the road surface in front of the vehicle based on the road surface state detection signal output from the road surface state detection means, and the period before and after the vehicle passes through the step or the like, Control is performed to gradually increase the current value output to the motor and then decrease it. Therefore, it is possible to prevent the motor current from abruptly changing due to the torque change when the vehicle passes through the step, and as a result, it is possible to reduce kickback or the like to the vehicle driver due to passing through the step. Therefore, it becomes possible to improve the steering feeling when passing through a step as compared with the conventional one.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment to which the electric power steering device of the present invention is applied will be described below with reference to the drawings.

First, the structure of the main part of a vehicle equipped with the electric power steering apparatus of this embodiment will be described with reference to FIG. 2. The steering 2 is supported by the steering shaft 3 on the front side of the driver's seat of the vehicle 1. The steering shaft 3 is provided with a torque sensor 4 that detects a torque associated with steering of the steering 2 based on a twist of a torsion bar (not shown) mounted on the shaft 3. At the same time, a motor 5 for applying an assisting force to a rack and pinion mechanism 8 described later,
An electromagnetic clutch 6 and a speed reducer 7 are arranged.

A rack and pinion mechanism 8 for converting the rotational movement of the steering wheel 2 into a reciprocating movement of the tie rod 9 is arranged on the lower end side of the steering shaft 3, and the tie rod 9 is connected to the rack and pinion mechanism 8. The front wheels 10 and 11 are mounted on both ends of the tie rod 9 via knuckle arms (not shown) and the like. The driving force of the motor 5 is transmitted as an assisting force to the rack and pinion mechanism 8 via the electromagnetic clutch 6, the speed reducer 7, and the steering shaft 3.

Inside the vehicle 1, a vehicle speed sensor 12 for detecting the vehicle speed, an engine rotation sensor 13 for detecting the rotation of an engine (not shown), a battery 14 for supplying power to a controller 15 and the like, which will be described later. A controller 1 for performing electric power steering control according to the flowchart of FIG.
5 (see FIG. 1). Further, inside the both ends of the front bumper of the vehicle 1, the road surface 16 on which the vehicle is running is
A pair of ultrasonic sensors 18 and 19 for detecting the step 17 and the like existing on the upper front are mounted.

The controller 15 determines the steering assist amount of the steering wheel 2 based on the torque associated with steering of the steering wheel 2 detected by the torque sensor 4 and the vehicle speed detected by the vehicle speed sensor 12. This will be described in detail in the description of FIG. Further, the ultrasonic sensors 18 and 19 emit ultrasonic pulses obliquely downward from the front bumper side toward the road surface in front of the vehicle when the vehicle 1 is traveling, and based on the reception intensity of the reflected wave from the road surface, the road surface 16
The upper step 17 is detected.

Next, the configuration of the electric power steering apparatus of this embodiment will be described with reference to FIG. 1. The controller 15 has a memory (20) and a microcomputer (CPU) 21 having a timer function, and a step detector. 22, a steering torque measuring unit 23, a vehicle speed measuring unit 24,
The engine rotation measurement unit 25, the clutch drive unit 26, the motor current output unit 27, and the motor current measurement unit 28 are provided. In this case, the memory 20 stores an output current value map storing current values to be output to the motor 5,
A correction coefficient (k, l, m) described later is stored in advance.

The step detector 22 includes an ultrasonic sensor 18,
19, the steering torque measuring unit 23 is connected to the torque sensor 4, and the vehicle speed measuring unit 24 is connected to the vehicle speed sensor 4.
The engine rotation sensor 13 is connected to the engine rotation measuring unit 25. The electromagnetic clutch 6 is connected to the clutch drive unit 26, and the motor 5 is connected to the motor current output unit 27.

The detection signals of the ultrasonic sensors 18 and 19 are input to the microcomputer 21 via the step detecting section 22, and the detection signals of the torque sensor 4 are input to the microcomputer 21 via the steering torque measuring section 23. It has become so. Further, the detection signal of the vehicle speed sensor 4 is input to the microcomputer 21 via the vehicle speed measurement unit 24, and the detection signal of the engine rotation sensor 13 is input to the microcomputer 21 via the engine rotation measurement unit 25. Has become.

The microcomputer 21 operates the ultrasonic sensors 18 and 19 by the step detecting unit 22 to detect the step on the road surface in front of the vehicle, and detects the step based on the detection signals of the ultrasonic sensors 18 and 19. The presence or absence is determined. Further, the microcomputer 21 reads the current value output from the memory 20 to the motor 5 based on the steering torque amount detected by the torque sensor 4 and the vehicle speed detected by the vehicle speed sensor 12. Further, the microcomputer 21 is adapted to calculate the correction amount of the current value output to the motor 5 and the correction value of the time for energizing the motor 5 based on the step detection signals of the ultrasonic sensors 18 and 19. .

Further, the microcomputer 21 compares the current value read from the memory 20 with the calculated correction current value, synthesizes them, determines the final output current value, and determines the final output current value. To drive the motor 5 (forward / reverse rotation). Further, the microcomputer 21 controls ON / OFF of the electromagnetic clutch 6 via the clutch drive unit 26, so that the motor 5
The (assist force of) and the speed reducer 7 are connected or disconnected.

The motor current measuring unit 28 measures the actual current value output from the motor current output unit 27 to the motor 5 and sends it to the microcomputer 21. The microcomputer 21 compares the measured current value with the instructed current value, and performs feedback control in which the measured current value follows the instructed current value, and abnormal current value detection.

Next, the difference in motor current control between this embodiment and the conventional example will be described with reference to FIG. 3. When a step is detected by the ultrasonic sensors 18 and 19, a time T1 is passed from the step measurement point. The step detection signal S1 (amplitude H, pulse width T2) is output (see). When the detection signal S2 is output from the torque sensor 4 as the vehicle climbs over a step (see), the motor current has a waveform S in the conventional control.
As shown in 3, the kickback is amplified and transmitted to the vehicle driver (see).

On the other hand, in the control of this embodiment, from the measurement point of the step by the ultrasonic sensors 18 and 19 (T1-t
1) After time (t1 hours before the output of the step detection signal S1)
Then, after the motor current is increased by the correction amount h as shown by the waveform S4, the correction amount h is canceled t2 hours after the vehicle has passed the step (see). Then, the motor current indicated by the microcomputer 21 and the motor current indicated by are compared, and the motor current obtained by combining the two motor currents is output as a waveform S5 (the period before and after passing the step of the vehicle is gradually increased and then decreased). (See).

That is, by controlling the motor current to gradually increase and then decrease during the period before and after the vehicle passes the step, the motor current is changed in accordance with the torque change when the vehicle passes the step as in the conventional case. It is designed to eliminate sudden changes and reduce kickback and the like for the vehicle driver. In this case, the microcomputer 21 calculates t1, t2, h based on a calculation formula of t1 = k · T1 t2 = l · T2 h = m · H (where k, l, m: correction coefficient). It has become. In addition, the microcomputer 21 measures each of the above-mentioned times by a built-in timer.

Next, the operation of this embodiment constructed as described above will be described with reference to FIG.

When the vehicle driver turns the engine key to turn on an ignition switch (not shown), a detection signal is input from the engine rotation sensor 13 to the microcomputer 21 of the controller 15 via the engine rotation measuring unit 25. Therefore, the microcomputer 21
Along with this, becomes a reset state and initializes (step S1). The microcomputer 21 reads the steering torque based on the detection signal input from the torque sensor 4 via the steering torque measurement unit 23 (step S
2) The vehicle speed is read based on the detection signal input from the vehicle speed sensor 12 via the vehicle speed measuring unit 24 (step S3).

Further, the microcomputer 21 uses the motor output current value map previously stored in the built-in memory 20 based on the read steering torque and vehicle speed to read the motor 5
The current value output to is read (step S4), and the step detection signal is read from the ultrasonic sensors 18 and 19 via the step detection unit 22 (step S5). Next, the microcomputer 21 determines whether or not there is a step on the road surface in front of the vehicle based on the step detection signal (step S6). If there is a step, the processing from step S7 onward is performed, and the step is detected. If it does not exist, the processing from step S9 is performed.

When there is a step ahead of the road surface of the vehicle, the microcomputer 21 detects the ultrasonic sensor 18,
The correction current for the motor 5 based on the time T1 from the step measurement point by 19 to the step, the pulse width T2 and the amplitude H of the step detection signal, and the correction coefficient (k, l, m) previously stored in the built-in memory 20. The value and the times t1 and t2 during which the correction current value is applied are calculated (step S7).

Further, the microcomputer 21 compares the current value read from the memory 20 based on the steering torque and the vehicle speed with the corrected current value calculated based on the step detection signal, and finally outputs the current value to the motor 5. Is determined (step S8), and the determined current value is output to the motor 5 via the motor current output unit 27 (step S9). That is, the microcomputer 21 performs control to gradually increase and then decrease the motor current value before and after the vehicle passes the step. Next, the microcomputer 21
When the motor current measuring unit 28 measures the current value output to the motor 5 via the motor current output unit 27 and sends the measured current value to the microcomputer 21, the measured current value is read (step S10). .

Then, the microcomputer 21 compares the measured current value with the instruction current value (step S11),
If the measured current value and the designated current value match, the processing from step S2 onward is repeated, and if the measured current value and the designated current value do not match, the processing from step S9 onward is repeated. The above is the flow of control of the present embodiment.

As described above, according to this embodiment, a step on the road surface in front of the vehicle is detected in advance while the vehicle is traveling, and the motor current is gradually increased before and after the vehicle passes the step. Then, the control is performed so as to lower the motor current, which can eliminate the rapid change in the motor current due to the torque change when the vehicle passes the step, which results in a kick to the vehicle driver when the vehicle passes the step. It is possible to reduce the back and the like, and it is possible to improve the steering feeling when passing a step as compared with the conventional case.

Further, in this embodiment, the ultrasonic sensors 18 and 19 are added to the conventional electric power steering apparatus and the control function of the controller is simply changed (in other words, the steps S5 to S8 in FIG. 4 are performed). Since it is only necessary to add processing), there is an advantage that it is possible to realize control that can reduce kickback and the like when a vehicle passes a step without performing complicated control or burdening the cost. .

In this case, in this embodiment, the ultrasonic sensor 1
When a step ahead of the vehicle running road surface is detected by 8 and 19, the motor current is corrected to be increased. For example, in the case of a bad road where there are continuous steps on the road surface (the ultrasonic sensor 18 , 19 in the case where the step detection signal is continuously output), it is also possible to perform control to reduce the motor current. As a result, it is possible to reduce kickback and the like that continuously occur when the vehicle travels on a rough road with continuous steps, and it is also possible to improve steering stability.

[0030]

As described above, according to the electric power steering apparatus of the present invention, when it is determined that there is a step or the like on the road surface in front of the vehicle, it is output to the motor during the period before and after the vehicle passes the step or the like. The control is performed so that the current value gradually increases and then decreases, so it is possible to eliminate the conventional drastic change in motor current that accompanies the torque change when the vehicle passes a step. As a result, it is possible to reduce kickback and the like for the vehicle driver, and it is possible to improve the driving feeling when passing a step as compared with the conventional case, which is a remarkable effect.

In addition, the control means further determines, based on the road surface state detection signal output from the road surface state detection means, whether or not a step or the like continuously exists on the road surface in front of the vehicle. The function and the current value output to the motor are reduced when it is determined that the step and the like exist continuously.
With the current value control function, it is possible to reduce the continuous kickback that occurs when the vehicle runs on a continuous rough road such as a step, and it is possible to reduce the steering stability. It is also possible to improve.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an electric power steering apparatus of the present embodiment to which the present invention is applied.

FIG. 2 is a schematic diagram showing a configuration of a main part of a vehicle equipped with the electric power steering device of the present embodiment.

FIG. 3 is a time chart comparing the motor current control in the present embodiment with the motor current control in the conventional example.

FIG. 4 is a flowchart showing motor current control in this embodiment.

[Explanation of symbols]

 2 Steering 4 Torque sensor as torque detecting means 5 Motor 12 Vehicle speed sensor as vehicle speed detecting means 15 Controller as control means 17 Steps 18 and 19 Ultrasonic sensor as road surface state detecting means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location B62D 137: 00

Claims (2)

[Claims] 1. A motor for assisting a steering force of a steering wheel mounted on a vehicle, a torque detecting means for detecting a steering torque of the steering wheel, a vehicle speed detecting means for detecting a vehicle speed, and a steering wheel detected by the torque detecting means. In an electric power steering apparatus including a control unit that determines a current value to be output to the motor based on a torque and a vehicle speed detected by the vehicle speed detection unit, an ultrasonic wave is emitted toward a road surface in front of the vehicle and the road surface is emitted from the road surface. A road surface condition detecting means for outputting a road surface condition detecting signal according to a reception intensity of the reflected ultrasonic wave; and the control means, on the road surface in front of the vehicle based on the road surface condition detecting signal outputted from the road surface condition detecting means. A step determination function that determines whether there is a step, etc., and if it is determined that a step exists, before the vehicle passes the step The period electric power steering apparatus characterized by comprising a current control function is lowered and subsequently gradually increasing the current value to be output to the motor. 2. The second control means further determines whether or not a step or the like continuously exists on a road surface in front of the vehicle based on a road surface state detection signal output from the road surface state detecting means. 2. The method according to claim 1, further comprising a step determination function and a second current value control function of reducing a current value output to the motor when it is determined that steps or the like continuously exist. Electric power steering device.