JP2004130902A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device for satisfying a requirement for reducing uncomfortable feeling by a relay off noise in turning-off a system having an adjustable fade means. <P>SOLUTION: The electric power steering device comprises a motor 110 for applying auxiliary torque to a steering system, a steering torque detection means 112 for detecting the steering torque of the steering system, a target current determining means 115 for determining a target current to be supplied to the motor based on at least a steering torque signal, a current detecting section 120 for detecting current flowing through the motor, a motor operation control section 118 for outputting a motor drive control signal for controlling the motor, and a gradual decrease section 30 for gradually decreasing the motor drive control signal. When an assist to the steering system is not required in turning off an ignition switch, the gradual decrease section 30 is turned off and then the relay is turned off. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric power steering device, and more particularly to an electric power steering device that reduces the steering force of a driver by applying the power of a motor to a steering system.
[0002]
[Prior art]
The electric power steering device includes a motor in a steering system, and controls the power supplied from the motor by using a control device to reduce the steering force of the driver.
[0003]
FIG. 5 is a schematic structural diagram of the electric power steering device. In the electric power steering apparatus 100, a steering shaft 102 provided integrally with a steering wheel (handle) 101 is connected to a pinion 105a of a rack and pinion mechanism 105 via a connection shaft 103 having universal joints 103a and 103b. Thus, the manual steering torque generating mechanism 106 is configured.
[0004]
The rack shaft 107 which has rack teeth 107a meshing with the pinion 105a and is reciprocated by being axially converted by the meshing is connected to the left and right front wheels 109 as rolling shafts at both ends via tie rods 108. I have. By operating the steering wheel 101, the driver can change the direction of the vehicle by swinging the front wheels via the manual steering torque generating mechanism 106 and a normal rack and pinion type steering device.
[0005]
In order to reduce the steering torque generated by the manual steering torque generating mechanism 106, a motor 110 for supplying an assist torque (steering assist torque) is disposed coaxially with the rack shaft 107, for example, and is substantially parallel to the rack shaft 107. The assist torque supplied by the rotational movement from the motor 110 via the provided ball screw mechanism 111 is converted into a force for the linear movement and acts on the rack shaft 107.
[0006]
The rotor of the motor 110 is integrally provided with a drive-side helical gear 110a. The helical gear 110a meshes with a helical gear 111b provided integrally with the shaft end of the screw shaft 111a of the ball screw mechanism 111. The nut of the ball screw mechanism 111 is connected to the rack shaft 107.
[0007]
FIG. 6 is a diagram illustrating a control device of the electric power steering device. In FIG. 5, a manual steering torque detector 112 for detecting a manual steering torque T acting on the pinion 105a is provided in a steering gear box (not shown). The manual steering torque detector 112 converts the detected manual steering torque T into a manual steering torque detection signal Td, and inputs the converted manual steering torque detection signal Td to the control device 114. The control device 114 operates the motor 110 using the manual steering torque detection signal Td as a main signal, and controls the power (steering assist torque) output by the motor 110.
[0008]
The control device 114 includes a target current determination unit 115 and a control unit 116. The target current determination unit 115 determines a target assist torque based on the manual steering torque detection signal Td, and outputs a target current signal IT required to supply the target assist torque from the motor 110.
[0009]
FIG. 7 is a block diagram of the control device 114. The control device 114 includes a target current determination unit 115 and a control unit 116, and the control unit 116 includes a deviation calculation unit 117, a motor operation control unit 118, a motor drive unit 119, and a current detection unit 120. The deviation calculator 117 obtains a deviation between the target current signal IT output from the target current determiner 115 and the motor current signal IM from the current detector 120, and outputs the value as a deviation signal 117a.
[0010]
The motor operation control unit 118 includes a deviation current control unit 121, a gradual decrease unit 130, and a PWM signal generation unit 122. The deviation current control unit 121 performs processing such as proportionality, integration, and differentiation on the input deviation signal 117a to control the motor current supplied to the motor 110 so that the value of the deviation signal 117a approaches zero. Of the drive current signal 121a is generated and output.
[0011]
The gradual decrease unit 130 is a device configured to gradually decrease the drive current signal 121a with the passage of time when the ignition switch is turned off. That is, the device is a device that performs a process of multiplying the input drive current signal 121a by a multiplication coefficient k and outputs the multiplication coefficient k, and at this time, the multiplication coefficient k gradually decreases with time.
[0012]
The PWM signal generation unit 122 generates a PWM (pulse width modulation) signal for performing the PWM operation of the motor 110 based on the drive current signal 121a, and outputs the generated PWM signal as a motor drive control signal 122a. When the drive current signal 121a is gradually decreased by the gradually decreasing section 130, the motor drive control signal 122a output from the PWM signal generation section 122 is also gradually decreased accordingly.
[0013]
The motor drive section 119 includes a gate drive circuit section 123 and a motor drive circuit 124 in which four power field effect transistors are connected in an H-bridge circuit configuration. The gate drive circuit unit 123 selects two field effect transistors according to the steering direction of the steering wheel 101 based on the motor drive control signal (PWM signal) 122a, and drives the gates of the selected two field effect transistors. These field effect transistors are switched.
[0014]
The current detection unit 120 detects a motor current (armature current) flowing through the motor 110 and outputs a motor current signal IM.
[0015]
As described above, the control device 114 PWM-controls the current supplied from the battery power source 126 to the motor 110 based on the manual steering torque T detected by the manual steering torque detection unit 112, and outputs the power (the steering assist torque) ) Control.
[0016]
As shown in FIG. 7, the control device 114 detects the motor current actually flowing to the motor 110 as a motor current signal IM in the control unit 116 and performs feedback control based on the motor current signal IM, thereby controlling the motor 110. The control characteristics have been improved.
[0017]
As described above, the manual steering torque T of the driver is detected by the manual steering torque detecting unit 112 of the manual steering torque generating mechanism 106, and the output of the motor 110 is controlled by the control device 114 to drive the steering gear box. Assists the force for the rack shaft 107 to move straight. Several such electric power steering devices have been disclosed (for example, see Patent Document 1).
[0018]
[Patent Document 1]
JP-A-11-34892
[Problems to be solved by the invention]
The control device has a microcomputer that controls the electric power steering device, and the microcomputer performs current feedback so that the motor current matches the target current signal IT corresponding to the manual steering torque. At the beginning and end of the control, there is known a function of fading in / out the assist amount so as not to give a sense of incongruity (abrupt force change or the like) to the steering. Further, the control device has a power drive circuit (H-type bridge circuit) for controlling a large current, and shuts off power supply to the H-type bridge circuit between the H-type bridge circuit and the power supply when a system failure occurs. A power relay for interrupting dark current is provided. In performing the above-described fade processing, it is assumed that the power relay is on as a condition for performing the fade-in / out. Therefore, at the time of fade-out, the fade process starts after the ignition switch is turned off (at the time of power-down), and the power relay is turned off after a predetermined time. An event of remaining occurs.
[0020]
SUMMARY OF THE INVENTION An object of the present invention is to provide an electric power steering device that satisfies a demand for reducing a sense of discomfort due to a relay-off sound when a system is turned off in a system having variable fade means in order to solve the above-mentioned problem.
[0021]
Means and action for solving the problem
The electric power steering apparatus according to the present invention is configured as follows to achieve the above object.
[0022]
An electric power steering apparatus according to the present invention (corresponding to claim 1) includes a motor for applying an auxiliary torque to a steering system, a steering torque detecting unit for detecting a steering torque of the steering system, and a motor based on at least a steering torque signal. A target current determining unit that determines a target current to be supplied to the motor, a current detecting unit that detects a current flowing through the motor, a motor operation control unit that outputs a motor drive control signal for driving the motor, and gradually outputs the motor drive control signal. An electric power steering device having a gradually decreasing portion that gradually reduces the target current signal output from the target current determining portion when the ignition switch is turned off, and a fade-out processing portion that outputs a no-fade-out command signal to the gradually decreasing portion when the target current signal is equal to or less than a predetermined value. Prepared, gradually decreased by receiving no fade-out command signal by the fade-out processing unit It is characterized by zero without decreasing the motor driving control signal.
[0023]
According to the electric power steering apparatus according to the present invention, a motor that applies an auxiliary torque to a steering system, a steering torque detector that detects a steering torque of the steering system, and a target to be supplied to the motor based at least on the steering torque signal A target current determination unit for determining a current, a current detection unit for detecting a current flowing through the motor, a motor operation control unit for outputting a motor drive control signal for driving the motor, and a gradually decreasing unit for gradually decreasing the motor drive control signal An electric power steering device having a fade-out processing unit that outputs a no-fade-out command signal to a gradually decreasing unit when a target current signal output from a target current determination unit when an ignition switch is turned off is equal to or less than a predetermined value; The gradually decreasing part that receives the no-fade-out command signal Since the control signal is reduced to zero without decreasing gradually, when no torque is applied or no fade is required, the power relay can be turned off immediately without performing fade processing, so the relay off sound is turned off by the ignition switch The sound can be covered, and the feeling of strangeness can be reduced.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
[0025]
The structure of the electric power steering device is basically the same as that shown in FIG. 5, and the structure and operation are as described above.
[0026]
FIG. 1 is a block diagram of a control device for an electric power steering device according to the present invention. The control device 1 shown in FIG. 1 is obtained by adding a fade-out processing unit 10 to the conventional control device 114 shown in FIGS. 6 and 7. Further, a function to be described later is added to the gradually decreasing portion.
[0027]
The fade-out processing unit 10 stops the gradual reduction processing of the multiplication coefficient k applied to the drive current signal when the steering torque is small and the target current IT becomes 0 A or less when the fade-out is performed. Then, after the specified time has elapsed, the multiplication coefficient k is set to 0.
[0028]
FIG. 2 is a configuration diagram of the fade-out processing unit 10. The fade-out processing unit 10 includes a CPU 11 and a memory 12, and the memory 12 stores a fade-out processing program 14. The fade-out processing unit 10 includes an input unit 15 and an output unit 16.
[0029]
The fade-out processing program 14 is a program for determining whether or not to perform the fade-out processing, and outputting a fade-out command signal for fading out to the gradually decreasing section 30 or a non-fade-out command signal for not fading out to the gradually decreasing section 30. As shown in FIG. When the ignition switch is turned off, an ignition switch-off signal is input to the fade-out processing unit 10. At this time, when the target current IT is input from the target current determination unit 115 (step ST10), the CPU 11 sets the target current IT to zero. It is determined whether or not the target current IT is not zero (step ST11). If the target current IT is not zero, a fade-out command signal is output to the gradually decreasing section (step ST12). If the target current IT is zero, it is determined whether or not a specified time has elapsed by a timer (step ST13). If the specified time has not elapsed, the process returns. A fade-out command signal is output to the gradually decreasing section 30 (step ST14).
[0030]
Next, the gradually decreasing section 30 will be described. The gradual decrease unit 30 includes a CPU, a memory, an input unit, and an output unit, not shown. A processing program is stored in the memory. The flowchart of the processing program in the gradually decreasing section 30 is as shown in FIG. When the ignition switch is turned off and an off signal is input, the program starts, and first, it is determined whether the signal from the fade-out processing unit 10 is a fade-out command signal or a no-fade-out command signal (step ST20). If the signal is a fade-out command signal, fade-out is performed (step ST21). That is, the multiplication coefficient k by which the drive current signal 121a output from the deviation current control unit 121 is multiplied by 1 until the preset time elapses after the fade-out command signal is supplied, and then the multiplication coefficient k is increased by 1 By gradually decreasing the value toward 0, a drive current gradual decrease signal is generated. Then, it is determined whether or not the multiplication coefficient k has become zero (step ST22). If the multiplication coefficient k is not zero, the process returns. When the multiplication coefficient k becomes zero, a power relay off signal is output (step ST23). The power relay 140 receiving the signal is turned off. On the other hand, when the signal from the fade-out processing unit 10 is a non-fade-out command signal, the multiplication coefficient k is set to 0 without fading out, so that the driving current signal becomes zero without fading out (step ST24). Then, the multiplication coefficient k is determined in step ST22, and since the multiplication coefficient k is zero, the power relay off signal is immediately output to the power relay 140 (step ST23). Thereby, power relay 140 is turned off.
[0031]
Next, a control method in the control device 1 shown in FIG. 1 will be described.
[0032]
The gradually decreasing section 30 starts operating when an off signal indicating that the ignition switch is turned off is input. Otherwise, it does not operate, and the motor drive signal passes as it is. When the gradually decreasing section 30 receives the OFF signal indicating that the ignition switch has been turned off, the gradually decreasing section 30 determines whether the drive current calculated by the deviation current control section 121 has been supplied when the fade-out command signal has been supplied from the fade-out processing section 10. The signal 121a is gradually reduced with the passage of time to generate a drive current gradually decreasing signal that is gradually reduced so that the drive current signal finally becomes 0, and the generated drive current gradually reduced signal is supplied to the PWM signal generation unit 122. I do.
[0033]
The gradual decrease unit 30 sets the coefficient k by which the drive current signal calculated by the deviation current control unit 121 corresponding to the deviation is multiplied to 1 until a preset time elapses from the time when the fade-out command signal is supplied, and thereafter, The drive current gradually decreasing signal is generated by gradually decreasing the multiplication coefficient k from 1 to 0 over time. Thereafter, when the multiplication coefficient k becomes zero, a power relay off signal is sent to the power relay, and the power relay is turned off.
[0034]
On the other hand, when the non-fade-out command signal is supplied from the fade-out processing unit 10, the multiplication coefficient k is set to 0 without fading out, the multiplication coefficient k is multiplied to set the drive current signal to 0, and at the same time, the relay-off command signal is set. And the relay is also shut off. Further, when the target current IT becomes zero during the fade-out, the “fade-out command signal” can be switched to the “no-fade-out command signal”.
[0035]
As described above, in this electric power steering apparatus, when the ignition switch is turned off in a small torque state, the instantaneous multiplication coefficient k becomes 0 and the power relay is turned off at the same time, so the off sound of the power relay is the off sound of the ignition switch. , The discomfort can be reduced.
[0036]
In the present embodiment, the description has been given of the case where the gradual decrease section is provided in the next stage of the deviation current control section. However, the gradual decrease section is provided in the next stage of the target current determination section, thereby gradually reducing the target current signal. Alternatively, the motor drive control signal may be gradually reduced, or the motor drive control signal may be gradually reduced by inserting a gradually decreasing unit in the next stage of the PWM signal generating unit. Further, in the present embodiment, the CPU of the fade-out processing unit and the CPU of the gradually decreasing unit have been described separately. However, one CPU may be commonly used for the fade-out processing unit and the gradually decreasing unit.
[0037]
【The invention's effect】
As apparent from the above description, the present invention has the following effects.
[0038]
A motor that applies an auxiliary torque to the steering system, a steering torque detector that detects a steering torque of the steering system, a target current setting unit that determines a target current to be supplied to the motor based on at least the steering torque signal, In an electric power steering device having a current detection unit for detecting a flowing current, a motor operation control unit for outputting a motor drive control signal for driving a motor, and a gradually decreasing unit for gradually decreasing the motor drive control signal, when an ignition switch is turned off, When the target current signal output from the target current determination unit is zero, the fade-out processing unit that outputs a non-fade-out command signal is provided in the gradual reduction unit, and the gradual reduction unit that receives the no-fade-out command signal from the fade-out processing unit controls the motor drive. To reduce the signal to zero without decreasing, Not, when there is no need of a fade, it is possible to turn off the power relay immediately without fading process, it is possible to suffer off sound of the relay off sound of the ignition switch, can reduce the discomfort.
[Brief description of the drawings]
FIG. 1 is a block diagram of a control device of an electric power steering device according to the present invention.
FIG. 2 is a configuration diagram of a fade-out processing unit.
FIG. 3 is a flowchart of a fade-out process in a fade-out processing unit.
FIG. 4 is a processing flowchart in a gradually decreasing unit.
FIG. 5 is a schematic structural view of an electric power steering device.
FIG. 6 is a diagram showing a control mechanism of a conventional electric power steering device.
FIG. 7
It is a block configuration diagram of a conventional control device.
[Explanation of symbols]
10 Fade-out processing unit 11 CPU
12 Memory 14 Fade-out processing program 15 Input unit 16 Output unit 30 Gradual reduction unit 110 Motor 112 Manual steering torque detection unit 114 Control unit 115 Target current determination unit 116 Control unit 117 Deviation calculation unit 118 Motor operation control unit 119 Motor drive unit 120 Current detection Part 130 taper part

Claims (1)

A motor for applying an assist torque to the steering system;
A steering torque detector that detects a steering torque of the steering system;
A target current determination unit that determines a target current to be supplied to the motor based on at least the steering torque signal;
A current detection unit that detects a current flowing through the motor,
A motor operation control unit that outputs a motor drive control signal for driving the motor,
In an electric power steering apparatus having a gradually decreasing portion that gradually reduces the motor drive control signal,
When the target current signal output from the target current determination unit when the ignition switch is turned off is less than or equal to a predetermined value, the gradual decrease unit includes a fade-out processing unit that outputs a no-fade-out command signal, and the fade-out processing unit outputs a no-fade-out command signal. The electric power steering apparatus according to claim 1, wherein the gradual decrease unit that receives the signal does not gradually decrease the motor drive control signal to zero.

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