JP2006273187A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an electric power steering apparatus capable of performing steering assistance with high responsiveness by predicting a timing when steering assist force is required and boosting a power supply voltage by operating a booster circuit before that. Let it be an issue.
SOLUTION: A navigation device 23 that detects and notifies position information of a host vehicle and road information in a traveling direction is provided, and a control device 22 boosts the voltage when the navigation device 23 detects a curve in the traveling direction of the vehicle. The circuit 24 starts to increase the voltage of the battery 25.
[Selection] Figure 1

Description

  The present invention relates to an electric power steering apparatus, and more particularly to an electric power steering apparatus having a power boosting circuit.

  The electric power steering device detects the steering torque and vehicle speed generated in the steering shaft when steering the steering handle, and when a large steering force is required based on this detection signal, the motor is driven to assist the steering assist force. Is generated to reduce the steering force of the steering wheel. That is, when the steering handle is being steered, if the steering torque is large, a large steering force is required. Therefore, the target value of the motor current is set so as to supply a large steering assist force, and the motor The feedback control is performed so that the actual current value of the current value coincides with the target value. Further, when the steering torque is small, a large steering force is not required, so the target value of the motor current is set so as to supply a small steering assist force.

  FIG. 4 shows a configuration of a conventional electric power steering apparatus 10. When the steering handle 11 is rotated, the steering shaft 12 directly connected to the steering handle 11 rotates the pinion gear 13 constituting the rack and pinion mechanism 15 via the connected torque sensor 20. As a result, the rack shaft 14 is moved, and the direction of the front wheel 17 is changed and steered. At this time, in accordance with the torque signal T detected by the torque sensor 20 and the vehicle speed signal V detected by the vehicle speed sensor 21, the control device 22 controls the power supply from the battery 25 to the motor 19 so that the target motor current flows. To do. With this supplied electric power, the motor 19 rotates the pinion gear 13 via the power transmission mechanism 18 and operates to reduce the steering torque of the steering handle 11.

  By the way, in such a system, current does not always flow through the motor 19, and current does not flow through the motor 19 unless the steering handle 11 is steered. However, when the motor 19 requires a current, a large current needs to flow. When a stationary vehicle that requires the maximum steering assist force is required, the required power is about 600 watts to 800 watts for a normal 2000 cc class vehicle. Current may be required.

  By the way, in order to control such a large current, a semiconductor switching element corresponding to the large current is required. The size of the semiconductor switching element is determined by the magnitude of the current that can flow. Moreover, in order to actually perform chopper control of a large current, a semiconductor switching element having a peak current value of 1.5 to 2 times the maximum current passed through the motor 19 is required, which increases the circuit size, It is inevitable that it will be expensive. In order to pass a larger current, the wiring around the circuit is also required to be thick enough to pass the current, and the weight of the wiring becomes a problem. In addition, a phenomenon is also known in which the electromotive force from the motor 19 increases and current does not flow easily when the motor 19 rotates fast.

In order to solve such a problem, when the vehicle speed that requires a large steering force decreases and the steering speed increases, the power supply voltage supplied to the motor from the in-vehicle battery via the booster circuit is increased and required. An example in which the value of current for obtaining electric power is reduced has been reported (see Patent Document 1).
However, if the power supply voltage is simply boosted when the vehicle speed or steering speed exceeds a specific threshold, the motor boosts in the same way even when the motor does not require a particularly high voltage. There is a problem of inhibiting the energy saving effect. Furthermore, even when a situation where boosting is necessary is caused, there is a problem that a time lag due to an inability to respond instantaneously due to the delay of determination and the rise time of the boosting circuit itself having a large current capacity impairs the responsiveness of the motor.

In order to solve this responsiveness problem, an example has been reported in which the output voltage is reduced as the output current of the booster circuit increases (see Patent Document 2).
JP-A-7-76280 JP 2003-54430 A

However, in the example of Patent Document 2, since the reference for boosting is based on when the rotation speed of the steering handle exceeds a certain threshold, boosting is not performed for the predicted steering operation, and voltage The problem of delaying the rise of the motor and impairing the responsiveness of the motor still remains. If the threshold value is set low in order to accelerate the response, the booster circuit is frequently started and stopped, which may affect the life of the semiconductor switching element and may cause noise in the vehicle electrical system. . As described above, in the conventional electric steering apparatus having a booster circuit that boosts the output voltage of the battery serving as the power source of the motor that assists the steering assist force, the boosting timing is likely to be delayed, and the threshold value is set to prevent this. If it is set to a low value, there is a problem that efficiency is deteriorated and noise is easily generated in the electric system.
This invention solves this point, and makes it a subject to implement | achieve the electric power steering device which can perform steering assistance with sufficient responsiveness by estimating the timing which needs steering assistance force.

  In order to solve the above-mentioned problem, the present invention calculates a target current based on at least an output signal from the steering input detecting means, and drives the motor with the target current, and is controlled by the control means, An electric power steering apparatus including a boosting unit that boosts an output voltage and supplies the boosted voltage to the motor includes road information detection unit that detects position information of the host vehicle and road information in a traveling direction, and the control unit The boosting by the boosting means is controlled by the information output from the road information detecting means. According to this, the voltage applied to the motor that outputs the steering assist force is controlled based on the position information of the host vehicle output from the road information detection means and the road information in the traveling direction. According to this, it is possible to predict the timing at which the power supply needs to be boosted based on the position information and the road information.

  In the electric power steering apparatus, the control unit starts boosting by the boosting unit when the road information detection unit detects a curve in the traveling direction of the host vehicle. According to this configuration, when a curve is detected in the traveling direction of the host vehicle, the voltage applied to the motor can be boosted, so that steering assistance with good responsiveness can be performed.

  In the electric power steering apparatus configured to start boosting by the boosting means when a curve is detected in the traveling direction of the host vehicle, the boosted voltage by the boosting means increases as the curvature of the curve increases. Thereby, the steering force increases as the curvature of the curve detected by the road information detection means increases, and the steering force decreases as the curvature decreases.

  The electric power steering apparatus includes vehicle speed detecting means for detecting the vehicle speed of the host vehicle, and the control means reduces the boosted voltage by the boosting means as the vehicle speed detected by the vehicle speed detecting means increases. Features. As a result, the steering force decreases as the vehicle speed increases, and the steering force increases as the vehicle speed decreases.

  ADVANTAGE OF THE INVENTION According to this invention, the electric power steering apparatus which can estimate the timing which needs pressure | voltage rise, and can perform steering assistance with sufficient responsiveness with minimum necessary electric power is implement | achieved.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a configuration of an electric power steering apparatus according to an embodiment of the present invention, and FIG. 2 is an operation flowchart of the electric power steering apparatus.
In FIG. 1, reference numeral 10 denotes an electric power steering apparatus, reference numeral 11 denotes a steering handle, reference numeral 12 denotes a steering shaft, reference numeral 13 denotes a pinion gear, reference numeral 14 denotes a rack shaft, reference numeral 14a denotes a rack gear, reference numeral 15 denotes a rack and pinion mechanism, Reference numeral 16 is a tie rod, reference numeral 17 is a front wheel, reference numeral 18 is a power transmission mechanism, reference numeral 19 is a motor, reference numeral 20 is a torque sensor (steering input detection means), reference numeral 22 is a control device (control means), reference numeral 23 is a navigation device ( Road information detecting means), 24 is a booster circuit (boosting means), and 25 is a battery.

  An electric power steering apparatus 10 mounted on a vehicle is configured to give auxiliary steering force (steering torque) to a steering shaft 12 or the like connected to a steering handle 11. An upper end of the steering shaft 12 is connected to the steering handle 11, and a pinion gear 13 is attached to the lower end. A rack shaft 14 provided with a rack gear 14a meshing with the pinion gear 13 is disposed. A rack and pinion mechanism 15 is formed by the pinion gear 13 and the rack gear 14a. Tie rods 16 are provided at both ends of the rack shaft 14, and front wheels 17 are attached to the outer ends of the tie rods 16. A motor 19 is provided for the steering shaft 12 via a power transmission mechanism 18. The motor 19 outputs a rotational force (torque) that assists the steering torque, and applies this rotational force to the steering shaft 12 via the power transmission mechanism 18. The steering shaft 12 is provided with a torque sensor 20. The torque sensor 20 detects the steering torque when a steering torque generated by the driver operating the steering handle 11 is applied to the steering shaft 12. A vehicle speed sensor 21 (vehicle speed detection means) detects the vehicle speed of the vehicle. The control device 22 takes in the steering torque signal T output from the torque sensor 20, the vehicle speed signal V output from the vehicle speed sensor 21, and the navigation information N from the navigation device 23, and based on these information, the motor In addition to outputting a drive control signal for controlling the rotation operation 19, the boost control information is output to control the booster circuit 24 to boost the output voltage of the battery 25, and the electric power steering device 10 is operated with a small current and steered. Auxiliary power is output to assist steering.

With this configuration, the operation of the electric power steering apparatus 10 will be described with reference to the operation flowchart of FIG. During the driving operation of the vehicle, the control device 22 performs control so as to assist steering in accordance with this operation flow.
When the vehicle starts to travel, in step 1, the control device 22 acquires navigation information such as the position information of the host vehicle and road information from the navigation device 23. In step 2, the control device 22 has a predetermined curvature or more in the traveling direction of the host vehicle. Determine if there is a curve. If there is a curve with a predetermined curvature or more (YES in S2), the process proceeds to step 3 and the current vehicle speed is taken in from the vehicle speed sensor 21. Next, in step 4, it is determined whether or not the captured vehicle speed is slower than a predetermined threshold value. If the vehicle speed is slower than a predetermined value (YES in S4), the process proceeds to step 5. A technique for detecting the presence of a curve in advance is already known (see Japanese Patent Application Laid-Open No. 2003-308600).

  In step 5, it is determined whether or not the booster circuit 24 is currently operating. If it is not operating (NO in S5), the process proceeds to step 6 and a predetermined time before the time when the vehicle reaches the curve at the current vehicle speed. Then, the booster circuit 24 is operated, and then the process proceeds to Step 7. If step-up circuit 24 is operating in step 5 (YES in S5), the process proceeds to step 7. In step 7, the control device 22 adjusts the boosted voltage of the booster circuit 24 to be increased as the curvature of the curve determined in step 2 is larger and the current vehicle speed is slower.

If there is no curve with a predetermined curvature or more in the traveling direction in step 2 (NO in S2) or if it is determined in step 4 that the vehicle speed is faster than the threshold (NO in S4), the process proceeds to step 8. It is determined whether or not the booster circuit 24 is currently operating. If the booster circuit 24 is operating (YES in S8), the process proceeds to step 9 to stop the operation of the booster circuit 24.
If the booster circuit 24 is not currently operating in step 8 (NO in S8), if the operation of the booster circuit 24 is stopped in step 9, and after adjusting the boosted voltage of the booster circuit 24 in step 7, Proceeding to step 10, steering assist is performed with the current power supply voltage. Thereafter, it is determined in step 11 whether or not the driving of the vehicle is continued. If so (YES in S11), the process returns to step 1 again. If not continued (NO in S11), the process ends.
FIG. 3 is an explanatory diagram showing the operation timing of boosting, where the curve is detected at point A before the start of the curve, and boosting is started at the start of the curve at point B. Then, the pressure increase ends at point C where the vehicle returns to the straight traveling state.

  According to the electric power steering apparatus 10 of this embodiment, the timing at which the power supply voltage needs to be boosted is predicted, and the booster circuit 24 is activated in advance so that a desired voltage is applied to the motor 19. Responsiveness does not become a problem, and a necessary steering assist force can be obtained with a minimum necessary current. Furthermore, the booster circuit 24 is not frequently started and stopped, so that the life of the semiconductor switching element is not affected, and no noise is generated in the electric system of the vehicle.

  Further, in the present invention, the pressure is increased by detecting the curve. However, for example, an area where there is a possibility of jumping out of the animal may be detected. If the curve continues through a predetermined straight line, the pressure is increased. Control may be performed so as to continue boosting without canceling. Furthermore, the present invention is also applicable to steer-by-wire (Steer_By_Wire) in which the steering wheel and the front wheels in the steering system S are mechanically separated.

  Since the electric power steering device of the present invention is configured as described above, it can be used effectively in a vehicle having a navigation device, and thus can be widely used for assisting steering of a vehicle or the like.

It is a block diagram which shows the structure of the electric power steering apparatus which is one Embodiment of this invention. It is an operation | movement flowchart of the electric power steering apparatus which is one Embodiment of this invention. It is explanatory drawing which shows the operation | movement timing of a pressure | voltage rise. It is a block diagram which shows the structure of the conventional electric power steering apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electric power steering apparatus 11 Steering handle 12 Steering shaft 13 Pinion gear 14 Rack shaft 14a Rack gear 15 Rack pinion mechanism 16 Tie rod 17 Front wheel 18 Power transmission mechanism 19 Motor 20 Torque sensor (steering input detection means)
21 Vehicle speed sensor (vehicle speed detection means)
22 Control device (control means)
23 Navigation device (road information detection means)
24 Booster circuit (Boosting means)
25 battery

Claims (4)

A target current is calculated based on at least an output signal from the steering input detection means, and a control means for driving the motor by the target current and controlled by the control means to boost the output voltage of the battery and supply it to the motor In an electric power steering apparatus having a boosting means,
Having road information detection means for detecting the position information of the own vehicle and road information in the traveling direction
The electric power steering apparatus, wherein the control means controls boosting by the boosting means based on information output from the road information detecting means.   2. The electric power steering apparatus according to claim 1, wherein the control unit starts boosting by the boosting unit when the road information detection unit detects a curve in the traveling direction of the host vehicle.   The electric power steering apparatus according to claim 2, wherein the control means increases the boosted voltage by the boosting means as the curvature of the curve increases.   2. The vehicle speed detecting means for detecting the vehicle speed of the host vehicle, wherein the control means decreases the boosted voltage by the boosting means as the vehicle speed detected by the vehicle speed detecting means increases. Item 4. The electric power steering device according to any one of Items 3.

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