JP3018808B2 - Electric motor driven four-wheel steering system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric motor driven four-wheel steering system for controlling a rear wheel steering angle by an electric motor.

[0002]

2. Description of the Related Art Conventionally, as an electric motor-driven four-wheel steering device that controls a rear wheel steering angle by an electric motor, for example,
Japanese Patent Application Laid-Open No. 4-321470 and the like are known.

[0003]

In the above-described electric motor-driven four-wheel steering system, when the electric motor power is obtained by driving a motor power relay interposed between the electric motor and the ignition power, a failure occurs. It is necessary to detect ON-side welding of the motor power relay in order to secure the output cutoff during safe operation.

As a well-known method for detecting the welding of the motor power supply relay, a method is known in which the relay is turned off once, and in this state, whether or not there is energization is detected.

[0005] However, in the conventional method for detecting relay welding, it takes time to detect relay welding for the following reasons.
There is a problem that the start of the rear wheel steering angle control must be delayed or the rear wheel steering angle control must be temporarily stopped.

That is, in a system having a relay,
When the power is switched from ON to OFF to ON, the terminal voltage of the relay does not immediately decrease due to the time constant of the circuit, so that it takes time to detect welding.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a motor-powered four-wheel steering system in which a rear wheel steering angle is controlled by an electric motor. An object of the present invention is to achieve both detection assurance and earlier start timing of rear wheel steering angle control.

[0008]

In order to solve the above-mentioned problems, in the electric motor-driven four-wheel steering apparatus of the present invention, welding of the motor power supply relay is checked before starting the rear wheel steering angle control, and the relay is welded. If not, control is started early. If welding of the relay is suspected, a check is performed again, and after confirming that there is no welding, control is started.

That is, as shown in the claim correspondence diagram of FIG. 1, an electric motor a for controlling a rear wheel steering angle by driving by application of a motor control current, and an interposition between the electric motor a and an ignition power supply b. A motor power supply relay c for supplying a motor power by driving the electric motor a;
Motor power supply voltage detecting means d for detecting the power supply voltage of the motor
If, when the ignition power b is Ru is turned on from the power supply is turned on
Is measured and the ignition time is turned on.
A first motor power supply voltage value determining means e for determining whether the motor power supply voltage value is less than a predetermined value when a short first set time immediately thereafter has passed, and the first motor power supply voltage value determining means
e, if the motor power supply voltage value is determined to be equal to or higher than the predetermined value,
Second motor power supply voltage value determining means f the motor supply voltage value to determine whether less than a predetermined value when the measured time has exceeded the second set time due to a long time setting than the first set time
And when the first motor power supply voltage value determining means e determines that the motor power supply voltage value is less than the predetermined value, and when the second motor power supply voltage value determining means f determines that the motor power supply voltage value is less than the predetermined value. When it is determined that the motor power supply voltage is greater than the predetermined value, a drive command is output to the motor power supply relay c and the rear wheel steering angle control is started. A rear wheel steering angle control means g for prohibiting the output of the drive command to the motor power supply relay c and prohibiting the rear wheel steering angle control when it is determined that there is any.

[0010]

[Action] when you switch to ON the ignition switch from OFF, when the ignition power b is Ru is turned on power
Time from injection is measured, measurement time is ignition
When a short first set time has elapsed immediately after power- on, the first motor power supply voltage value determining means e determines whether the motor power supply voltage value from the motor power supply voltage value detecting means d is less than a predetermined value. Also, the first motor power supply voltage value judgment
If the means e determines that the motor power supply voltage value is equal to or higher than the predetermined value,
If, in the second motor power supply voltage value determining means f, ignition
Measurement time after turning on the power supply is longer than the first set time
When the second set time by have set time has elapsed, the motor supply voltage value from the motor supply voltage value detection unit d whether less than the predetermined value.

In the rear wheel steering angle control means g, when the first motor power supply voltage value determining means e determines that the motor power supply voltage value is less than a predetermined value, a drive command is output to the motor power supply relay c. When the second motor power supply voltage value determining means f determines that the motor power supply voltage value is less than the predetermined value, a drive command is output to the motor power supply relay c and the rear wheel steering angle control is started. . Further, when both motor power supply voltage value determining means e and f determine that the motor power supply voltage value is equal to or more than the predetermined value, the output of the drive command to the motor power supply relay c is prohibited and the rear wheel steering angle control is prohibited. Is done.

Therefore, when the ignition is switched from OFF to ON after a sufficient ignition OFF time when the motor power relay c is not welded, the motor power supply voltage value is zero, and the first motor The power supply voltage value determination means e determines that the motor power supply voltage value is less than the predetermined value, and immediately outputs a drive command to the motor power supply relay c, thereby starting the rear wheel steering angle control system early. be able to.

When the motor power relay c is not welded,
When the ignition is switched from OFF to ON after a short ignition OFF time, the motor power supply voltage value remains high due to the time constant of the circuit, and the motor power supply voltage value exceeds a predetermined value at the time of the first set time. However, at the time of the second set time thereafter, the second motor power supply voltage value determining means f determines that the motor power supply voltage value is less than the predetermined value. Is output. In this case, although the start timing of the rear wheel steering angle control is delayed, the non-welding of the motor power supply relay c is reliably detected by the recheck.

Further, at the time of welding the motor power relay c, the motor power voltage value is determined to be equal to or higher than the predetermined value both at the first set time and at the second set time, and the output of the drive command to the motor power relay c is prohibited. Being done, 2
A fail-safe system can be entered based on the detection of welding of the motor power supply relay c by checking the degree.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

First, the configuration will be described.

FIG. 2 is an overall system diagram showing a vehicle to which the electric motor-driven four-wheel steering device according to the embodiment of the present invention is applied. FIG. 3 is an electric rear wheel steering of the electric motor-driven four-wheel steering device according to the embodiment. FIG. 4 shows the mechanism, and FIG.
FIG. 2 is an electronic control system diagram centered on an S control unit.

In FIG. 2, reference numerals 1 and 2 denote front wheels, 3 and 4 denote rear wheels, 5 denotes a mechanical front wheel steering mechanism, and 6 denotes an electric rear wheel steering mechanism.

The mechanical front wheel steering mechanism 5 increases a steering force input from a steering wheel 7 steered by a driver via a steering shaft 8 by a power steering (not shown), and increases the increased steering force to a rack shaft 9. Through the side rods 10 and 11 and the knuckle arms 12 and 13 to provide a steering angle to the front wheels 1 and 2.

The electric rear wheel steering mechanism 6 includes four
The rotational force of the high cas motor 15 (corresponding to the electric motor a) controlled by the motor output from the WS control unit 14 is transmitted to the worm 16 and the worm wheel 17.
And the rotational motion of the worm wheel 17 is converted into linear motion of the rack shaft 19 by meshing the gear portion of the pinion shaft 18 with the gear portion of the rack shaft 19, and the side rods 20, 21 and the knuckle arm are transferred from the rack shaft 19. Via the rear wheels 3,
4 to provide a steering angle.

The 4WS control unit 14 includes:
As shown in FIG. 4, the power supply circuit 14a and the sensor power supply circuit 1
4b, input interface 14c, CPU1, CPU
2, monitoring circuit 14d, D / A conversions 14e, 14f, 14
g, 14h, 14i, a CPU output monitoring circuit 14j, a relay output driver 14k, a motor output driver 14m, and a power steering solenoid output driver 14n.

The power supply circuit 14a has a battery power supply directly from the battery 24 and an ignition switch 25.
Of the ignition power (corresponding to the ignition power b).

The input interface 14c includes a sensor signal from a rear steering angle main sensor 26 and a rear steering angle sub sensor 27 by a potentiometer, a sensor signal from a steering sensor 28, a sensor signal from a vehicle speed sensor 29, and a stop lamp. Switch signals from the switch 30, the brake switch 31, and the inhibit switch 32 are input. Here, the rear steering angle main sensor 26 is a sensor that detects the rotation amount of the pinion shaft 18, and the rear steering angle sub-sensor 27 is a sensor that detects the stroke amount of the rack shaft 19.

The relay output driver 14k receives the monitoring output from the monitoring circuit 14d and the warning valve output from the warning valve 33, and
(Equivalent to the motor power relay c).

The motor output driver 14m is driven by a motor power supply via a high cas relay 34,
A rear wheel steering angle command is input from PU1 via D / A converters 14g and 14h, and a motor output is sent to the high cas motor 15.

The power steering solenoid output driver 14
n inputs a power steering command from the CPU 1 via the D / A converter 14i, and sends a power steering solenoid output to the power steering solenoid 35.

Next, the operation will be described.

[Relay drive control operation] FIG. 5 is a flowchart showing the flow of the relay drive control operation performed by the monitoring circuit 14d of the 4WS control unit 14.
Hereinafter, each step will be described (corresponding to the rear wheel steering angle control means g).

Ignition switch 2 in step 50
The switching operation of the switch 5 from OFF to ON starts the processing described later.

In step 51, the motor power supply voltage value Vre
lay is read.

The motor power supply voltage value Vrelay is obtained by measuring the terminal voltage of the high cast relay 34 by an internal circuit or by inputting it to a comparison circuit (corresponding to motor power supply voltage value detecting means d).

In step 52, the timer value T from the time when the ignition switch 25 is turned on is set to the first set time t.
It is determined whether it is 1 (for example, 1 sec) or more.

In step 53, when the time condition of step 52 is satisfied, it is determined whether or not the latest motor power supply voltage value Vrelay is less than 9 V (corresponding to the first motor power supply voltage value determination means e). ).

In step 54, the motor power supply voltage value Vrelay is read in the same manner as in step 51.

In step 55, the timer value T from the time when the ignition switch 25 is turned on is set to the second set time t.
It is determined whether it is 2 (for example, 4 sec) or more.

In step 56, when the time condition of step 55 is satisfied, it is determined whether or not the latest motor power supply voltage value Vrelay is less than 9 V (corresponding to the second motor power supply voltage value determination means f). ).

In step 57, Vre in step 53
When lay <9V is satisfied, or when Vrelay <9V is satisfied in step 56, a drive command to turn on the relay switch is output to the high cas relay 34.

In step 58, the rear wheel steering angle control is started on the premise that the motor power is secured by the relay drive in step 57.

In step 59, when none of the conditions of Vrelay <9V in steps 53 and 56 is satisfied, the relay switch is turned off to the high-cast relay 34.
A drive prohibition command to keep F is output, and a fail-safe process such as prohibition of rear wheel steering angle control and lighting of the warning valve 33 is executed.

[First Relay Welding Detection Operation] When the ignition switch 25 is switched from OFF to ON after sufficient OFF time of the ignition switch 25 has elapsed while the high cast relay 34 is not welded, as shown in FIG. Since the motor power supply voltage value Vrelay is zero, the motor power supply voltage value Vrelay is determined to be Vrelay <9 V by the motor power supply voltage value determination in step 53.
, A drive command is output, and the system for starting rear wheel steering angle control can be started early.

That is, as shown in the time chart of FIG. 6, the highcast relay 34 is switched from OFF to ON at the time when the first set time t1 has elapsed from the time when the ignition switch 25 was switched from OFF to ON,
This time is the start timing at which the rear wheel steering angle control can be started.

However, in the embodiment, after a relay power ON check allowance time t3 has elapsed from the relay ON time, the rear steering angle control logic is executed to start the rear wheel steering angle control.

Here, the first set time t1 is set to 1 second. This is because when the high cast relay 34 is welded to the ON side, the ignition switch 25 is turned on and then the capacitor for the motor power supply is charged. Is set by the time required.

The threshold for judging the motor power supply voltage value is set to 9 V. This is because the minimum value of the motor power supply voltage value is 10 V, and the harness and the relay contact resistance of about 1 V are taken into consideration. Is set.

[Second Relay Weld Detection Operation] When the high cast relay 34 is not welded, a short OFF time of the ignition switch 25 elapses and the ignition switch 2
5 is switched from OFF to ON, as shown in FIG. 7, the motor power supply voltage Vrelay remains high due to the time constant of the circuit, and at the time of the first set time t1, the motor power supply voltage Vrelay becomes Vrelay. Even if it is determined that ≧ 9V, at the time of the second set time t2 thereafter, step 55
The motor power supply voltage value Vrela
It is determined that y is Vrelay <9V, and the routine proceeds to step 57, where a drive command is output to the high cas relay 34 at this time.

That is, as shown in the time chart of FIG. 7, the high cast relay 34 is switched from OFF to ON at the time when the second set time t2 has elapsed since the time when the ignition switch 25 was switched from OFF to ON,
This time is a start timing at which the rear wheel steering angle control can be started, and although the start timing of the rear wheel steering angle control is delayed, the non-welding of the high cast relay 34 is reliably detected by the recheck.

Here, the second set time t2 is set to 4 sec. This is because the ignition switch 25 is turned off.
Immediately after switching from ON to ON, assuming full acceleration, the vehicle speed requires rear wheel steering angle control in about 4 seconds, so this time is used as it is.

[Third Relay Weld Detection Operation] At the time of welding of the high cast relay 34, as shown in FIG.
Even at the set time t2, the motor power supply voltage value Vrelay is V
Since it is determined that relay ≧ 9V, the process proceeds to step 59, and the output of the drive command to the high cast relay 34 is prohibited.

Therefore, steps 53 and 56
Based on the detection of welding of the high cast relay 34 by the two checks described above, a fail-safe system can be entered.

Next, the effects will be described.

(1) In an electric motor-driven four-wheel steering system in which the rear wheel steering angle is controlled by the high-cass motor 15,
Set the ignition switch 25 to O before starting the rear wheel steering angle control.
At the time of the first set time t1 after setting N, the welding check of the high cast relay 34 is performed.
If the welding is not welded, the control is started immediately. If the welding of the high cast relay 34 is suspected, the ignition switch 25 is turned on and a check is performed again at the second set time t2 to confirm that there is no welding. Then, since the relay drive control for starting the control is performed, the detection of the welding of the high cas relay 34 can be ensured and the timing of starting the rear wheel steering angle control can be achieved at the same time.

(2) The first set time t1 for performing the welding check is 1 second required for charging the motor power supply capacitor after turning on the ignition switch 25 when the high cast relay 34 is welded to the ON side. , The shortest rear wheel steering angle control start timing can be obtained while ensuring the detection of welding of the high cas relay 34.

(3) The ignition switch 25 is turned on from OFF to ON for the second set time t2 for performing the welding check.
Immediately after switching to, assuming full acceleration, the vehicle speed will require the rear wheel steering angle control in about 4 seconds, so this time was used as it was and set for 4 seconds, so even if the vehicle starts in full acceleration, It is possible to secure rear wheel steering angle control that enhances turning performance when the vehicle speed at which wheel steering angle control becomes necessary.

Although the embodiment has been described with reference to the drawings, the specific configuration is not limited to the embodiment, and even if there are changes and additions without departing from the gist of the invention, the invention is included in the invention. It is.

For example, the first set time t1 (1 sec), the second set time t2 (4 sec), and the motor power supply voltage value determination threshold 9V are not limited to the values of the embodiment, but may be controlled by the control system or the system. Can be set as appropriate depending on the vehicle on which is mounted.

[0056]

As described above, according to the present invention, in an electric motor-driven four-wheel steering system in which a rear wheel steering angle is controlled by an electric motor, a motor power supply relay is controlled before starting rear wheel steering angle control. A means to start welding control, start control early if the relay is not welded, check again if the relay is suspected to be welded, confirm that there is no welding, and then start control Thus, it is possible to achieve both the detection of welding of the motor power supply relay and the early start of the rear wheel steering angle control start timing.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to a claim showing an electric motor-driven four-wheel steering device of the present invention.

FIG. 2 is an overall system diagram showing a vehicle to which the electric motor-driven four-wheel steering device according to the embodiment of the present invention is applied.

FIG. 3 is a diagram showing an electric rear wheel steering mechanism of the electric motor driven four-wheel steering device of the embodiment.

FIG. 4 is an electronic control system diagram centering on a 4WS control unit of the embodiment apparatus.

FIG. 5 is a flowchart showing a flow of a relay drive control operation performed by a monitoring circuit of a 4WS control unit of the embodiment device.

[Fig. 6] Sufficient ignition OF when relay is not welded
5 is a time chart when the ignition is switched from OFF to ON after an elapse of an F time.

FIG. 7: Short ignition OFF when relay is not welded
It is a time chart when the ignition is switched from OFF to ON after a lapse of time.

FIG. 8: The ignition is switched from OFF to O at the time of relay welding
It is a time chart at the time of switching to N.

[Explanation of symbols]

 a electric motor b ignition power supply c motor power supply relay d motor power supply voltage value detection means e first motor power supply voltage value determination means f second motor power supply voltage value determination means g rear wheel steering angle control means

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ identification code FI B62D 113: 00 (58) Field surveyed (Int.Cl. ⁷ , DB name) B62D 5/04 B62D 6/00 B62D 7/14

Claims (1)

(57) [Claims] An electric motor for controlling a rear wheel steering angle by driving by applying a motor control current; a motor power relay interposed between the electric motor and an ignition power supply for supplying the motor power by driving the motor; the motor power supply voltage value detection means for detecting the power supply voltage value of the electric motor, the time from when the ignition camera turns is turned power-on
Is measured, and the measurement time is immediately after the ignition power is turned on.
Short the first motor power supply voltage value determining unit that the motor supply voltage value to determine whether less than a predetermined value at the time when the first set has passed the time, the motor supply voltage value in the first motor power supply voltage value determining means
Is determined to be equal to or greater than the predetermined value, the measurement time is set to the first setting
A second motor power supply voltage value determining means for determining whether or not the motor power supply voltage value is less than a predetermined value when a second set time by a time setting longer than the predetermined time has elapsed; When the voltage value is determined to be less than the predetermined value, or when the second motor power supply voltage value determination means determines that the motor power supply voltage value is less than the predetermined value, a drive command is issued to the motor power supply relay. Output and start rear wheel steering angle control, and when both motor power supply voltage value determination means determine that the motor power supply voltage value is equal to or greater than a predetermined value, output of a drive command to the motor power supply relay is prohibited. An electric motor-driven four-wheel steering device, comprising: a rear wheel steering angle control unit that prohibits rear wheel steering angle control.